阅读说明：本技术 用于侧链路通信的消息的按需中继 (On-demand relaying of messages for sidelink communications ) 是由 T·V·恩古延 S·K·巴盖尔 K·古拉蒂 A·巴德瓦 于 2020-03-13 设计创作，主要内容包括：描述了用于无线通信的方法、系统和设备。在一些系统(例如,车联网(V2X)系统)中,源用户装备(UE)可以将数据分组多播到周围的UE。在一些情形中,接收方UE可能由于阻塞、遮蔽或干扰而未能接收到传输。接收方UE可以多播请求分组的重传的消息。成功地从源UE接收到数据分组并且从接收方UE接收到中继请求消息的任何周围UE可以确定是否中继该分组。确定是否中继分组可以基于参考信号收到功率(RSRP)阈值、可用资源、到被阻塞的UE的距离或其某种组合。在一些示例中,即使在接收方UE与原始源UE之间的路径被阻塞的情况下,接收方UE也可以成功地从中继UE接收经中继的分组。(Methods, systems, and devices for wireless communication are described. In some systems, such as a vehicle networking (V2X) system, a source User Equipment (UE) may multicast data packets to surrounding UEs. In some cases, the receiving UE may fail to receive the transmission due to blocking, shadowing, or interference. The recipient UE may multicast a message requesting retransmission of the packet. Any surrounding UEs that successfully received a data packet from the source UE and received a relay request message from the recipient UE may determine whether to relay the packet. Determining whether to relay a packet may be based on a Reference Signal Received Power (RSRP) threshold, available resources, distance to a blocked UE, or some combination thereof. In some examples, the recipient UE may successfully receive the relayed packet from the relay UE even if the path between the recipient UE and the original source UE is blocked.)

1. A method for wireless communication at a first User Equipment (UE), comprising:

determining that the first UE failed to receive a data packet from a second UE;

transmitting a message indicating failure of the first UE to receive the data packet; and

receiving the data packet from a third UE different from the second UE based at least in part on the message indicating failure of the first UE to receive the data packet.

2. The method of claim 1, wherein determining that the first UE failed to receive the data packet from the second UE comprises:

receiving control information from the second UE;

decoding the control information, wherein the decoded control information indicates resources for transmission of the data packet; and

failing to decode the data packet in the indicated resources.

3. The method of claim 2, further comprising:

determining whether to schedule at least one further retransmission of the data packet by the second UE based at least in part on the decoded control information.

4. The method of claim 2, further comprising:

determining that there are one or more further retransmissions of the data packet scheduled by the second UE, wherein the message indicating failure of the first UE to receive the data packet is transmitted based at least in part on determining the absence.

5. The method of claim 2, wherein the decoded control information further indicates a second resource for retransmission of the data packet, the method further comprising:

determining that decoding the data packet fails in the indicated second resource for retransmission; and

transmitting a second message indicating a failure to decode the data packet in the indicated second resource for retransmission.

6. The method of claim 1, further comprising:

determining a cause of failure of the first UE to receive the data packet, wherein the cause of failure is interference, a transmitted received signal energy being below a received signal energy threshold, or a combination thereof.

7. The method of claim 6, further comprising:

determining whether to transmit the message indicating the failure of the first UE to receive the data packet to the second UE or the third UE, or both, based at least in part on the reason for the failure.

8. The method of claim 6, further comprising:

determining an attachment failure of the first UE to receive an attachment data packet from the second UE;

determining that a cause of the additional failure of the first UE to receive the additional data packet is interference;

determining to schedule at least one further retransmission of the additional data packet by the second UE, wherein the at least one further retransmission is dependent on a negative acknowledgement message;

transmitting a negative acknowledgement message of the additional data packet to the second UE based at least in part on the cause of the additional failure of the first UE to receive the additional data packet being interference; and

receiving a retransmission of the additional data packet from the second UE based at least in part on the negative acknowledgement message.

9. The method of claim 6, wherein:

the reason for the failure is that the received signal energy of the transmission is below the received signal energy threshold; and

the message indicating failure of the first UE to receive the data packet is transmitted to the third UE.

10. The method of claim 1, further comprising:

selecting one or more resources for a resource reservation, wherein the message indicating failure of the first UE to receive the data packet includes the resource reservation, and wherein the data packet is received on the one or more resources indicated by the resource reservation.

11. The method of claim 1, wherein the message indicating that the first UE failed to receive the data packet comprises a source identifier indicating the second UE or a packet identifier indicating the data packet, or both.

12. The method of claim 11, wherein receiving the data packet comprises:

receiving the data packet from the third UE based at least in part on the source identifier or the packet identifier or both.

13. The method of claim 1, wherein the message indicating failure of the first UE to receive the data packet comprises an exclusion range of reserved resources, a modulation and coding scheme, a transmission mode, a redundancy version, a reference signal pattern, or a combination thereof, and wherein receiving the data packet comprises:

receiving the data packet from the third UE based at least in part on the exclusion range of the reserved resources, the modulation and coding scheme, the transmission mode, the redundancy version, the reference signal pattern, or a combination thereof.

14. The method of claim 1, further comprising:

receiving the data packet from a fourth UE different from the second UE and the third UE based at least in part on the message indicating failure of the first UE to receive the data packet; and

decoding the data packet based at least in part on combining information corresponding to receiving the data packet from the third UE with information corresponding to receiving the data packet from the fourth UE.

15. The method of claim 1, wherein the message indicating the failure of the first UE to receive the data packet comprises a negative acknowledgement message or a request for the data packet, or both.

16. A method for wireless communication at a first User Equipment (UE), comprising:

receiving a data packet from a second UE;

receiving a message from a third UE indicating a failure of the third UE to receive the data packet; and

relaying the data packet to the third UE based at least in part on the message indicating failure of the third UE to receive the data packet.

17. The method of claim 16, wherein the message indicating failure of the third UE to receive the data packet comprises a resource reservation, the method further comprising:

determining one or more resources indicated by the resource reservation; and

determining to relay the data packet to the third UE based at least in part on the first UE supporting transmission on the one or more resources, wherein the data packet is relayed to the third UE on the one or more resources indicated by the resource reservation.

18. The method of claim 16, further comprising:

determining a reference signal received power for receiving the message indicating failure of the third UE to receive the data packet; and

determining to relay the data packet to the third UE based at least in part on the determined reference signal received power being greater than a reference signal received power threshold.

19. The method of claim 18, wherein the message indicating failure of the third UE to receive the data packet includes a reference signal received power threshold, the method further comprising:

determining the reference signal received power threshold based at least in part on the message indicating failure of the third UE to receive the data packet.

20. The method of claim 18, further comprising:

adjusting a power control parameter for relaying the data packet to the third UE based at least in part on the determined reference signal received power.

21. The method of claim 16, further comprising:

receiving a message from a fourth UE indicating a failure of the fourth UE to receive additional data packets, wherein the message indicating the failure of the fourth UE to receive the additional data packets includes a resource reservation;

determining to refrain from relaying the additional data packet to the fourth UE in one or more resources indicated by the resource reservation; and

refraining from communicating on one or more resources that overlap with one or more resources indicated by the resource reservation based at least in part on the resource reservation.

22. The method of claim 16, wherein the data packet is received from the second UE according to a modulation and coding scheme, a spatial multiplexing scheme, and a demodulation reference signal pattern, and wherein relaying the data packet to the third UE comprises:

relaying the data packet to the third UE according to the modulation and coding scheme, the spatial multiplexing scheme, the demodulation reference signal pattern, or a combination thereof.

23. The method of claim 16, wherein the data packet is received from the second UE according to a first modulation and coding scheme, a first spatial multiplexing scheme, and a first demodulation reference signal pattern, and wherein relaying the data packet to the third UE comprises:

relaying the data packet to the third UE according to a second modulation and coding scheme different from the first modulation and coding scheme, a second spatial multiplexing scheme different from the first spatial multiplexing scheme, a second demodulation reference signal pattern different from the first demodulation reference signal pattern, or a combination thereof.

24. The method of claim 23, wherein the message indicating failure of the third UE to receive the data packet comprises an indication of the second modulation and coding scheme, the second spatial multiplexing scheme, the second demodulation reference signal pattern, or a combination thereof, the method further comprising:

determining the second modulation and coding scheme, the second spatial multiplexing scheme, the second demodulation reference signal pattern, or a combination thereof based at least in part on the message indicating failure of the third UE to receive the data packet.

25. The method of claim 16, further comprising:

determining a distance between the first UE and the third UE; and

determining to relay the data packet to the third UE based at least in part on the determined distance being less than a distance threshold.

26. The method of claim 16, wherein the message indicating that the third UE failed to receive the data packet comprises a source identifier indicating the second UE, a packet identifier indicating the data packet, an exclusion range of reserved resources, a transmission mode, a redundancy version, a reference signal pattern, or a combination thereof, and wherein relaying the data packet to the third UE comprises:

relaying the data packet to the third UE based at least in part on the source identifier, the packet identifier, the exclusion range of the reserved resources, the transmission mode, the redundancy version, the reference signal pattern, or a combination thereof.

27. The method of claim 16, wherein the message indicating the failure of the third UE to receive the data packet comprises a negative acknowledgement message or a request for the data packet, or both.

28. A method for wireless communication at a first User Equipment (UE), comprising:

scheduling transmission of the data packet in one or more resources to the second UE and the third UE;

transmitting control information to the second UE and the third UE, the control information including resource reservations indicating the one or more resources and including an indication that enables the second UE to relay the data packet to the third UE in response to a message indicating failure of the third UE to receive the data packet; and

transmitting the data packet to the second UE and the third UE in the one or more resources.

29. The method of claim 28, further comprising:

receiving the data packet from the second UE based at least in part on the message indicating failure of the third UE to receive the data packet.

30. An apparatus for wireless communication at a first User Equipment (UE), comprising:

means for determining that the first UE failed to receive a data packet from a second UE;

means for transmitting a message indicating failure of the first UE to receive the data packet; and

means for receiving the data packet from a third UE different from the second UE based at least in part on the message indicating failure of the first UE to receive the data packet.

SUMMARY

A method for wireless communication at a first UE is described. The method can comprise the following steps: determining that the first UE failed to receive the data packet from the second UE; transmitting a message indicating a failure of the first UE to receive the data packet; and receiving a data packet from a third UE different from the second UE based on the message indicating failure of the first UE to receive the data packet.

An apparatus for wireless communication at a first UE is described. The apparatus may include a processor and a memory coupled to the processor. The processor and memory may be configured to: determining that the first UE failed to receive the data packet from the second UE; transmitting a message indicating a failure of the first UE to receive the data packet; and receiving a data packet from a third UE different from the second UE based on the message indicating failure of the first UE to receive the data packet.

Another apparatus for wireless communication at a first UE is described. The apparatus may include means for: determining that the first UE failed to receive the data packet from the second UE; transmitting a message indicating a failure of the first UE to receive the data packet; and receiving a data packet from a third UE different from the second UE based on the message indicating failure of the first UE to receive the data packet.

A non-transitory computer-readable medium storing code for wireless communication at a first UE is described. The code may include instructions executable by a processor for: determining that the first UE failed to receive the data packet from the second UE; transmitting a message indicating a failure of the first UE to receive the data packet; and receiving a data packet from a third UE different from the second UE based on the message indicating failure of the first UE to receive the data packet.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, determining that a first UE failed to receive a data packet from a second UE may include operations, features, apparatuses, or instructions to: the method further includes receiving control information from the second UE, decoding the control information, and failing to decode the data packet in the indicated resource. In some cases, the decoded control information indicates resources for transmission of the data packet.

Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: determining whether to schedule at least one further retransmission of the data packet by the second UE based on the decoded control information.

Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: it is determined that there are no one or more further retransmissions of the data packet scheduled by the second UE. In some cases, a message indicating failure of the first UE to receive the data packet may be transmitted based on determining the absence.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, the decoded control information may further indicate a second resource for retransmission of the data packet. Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: determining that decoding the data packet in the indicated second resource for retransmission failed, and transmitting a second message indicating that decoding the data packet in the indicated second resource for retransmission failed.

Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: a cause of failure of the first UE to receive the data packet is determined. In some cases, the cause of the failure may be interference, the received signal energy of the transmission is weak (e.g., below a received signal energy threshold), or a combination thereof.

Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: determining whether to transmit a message to the second UE or the third UE or both indicating a failure of the first UE to receive the data packet based on the reason for the failure.

Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: an attachment failure of the first UE to receive the additional data packet from the second UE is determined. Some examples may further include operations, features, means, or instructions for: a determination is made that the cause of the additional failure of the first UE to receive the additional data packet is interference. Some examples may further include operations, features, means, or instructions for: at least one further retransmission of the additional data packet is determined to be scheduled by the second UE, and the at least one further retransmission may be dependent on a Negative Acknowledgement (NAK) message. Some examples may further include operations, features, means, or instructions for: a NAK message for the additional data packet is transmitted to the second UE based on the reason for the additional failure of the first UE to receive the additional data packet being interference. Some examples may further include operations, features, means, or instructions for: a retransmission of the additional data packet is received from the second UE based on the NAK message.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, the reason for the failure is that the transmitted received signal energy is weak, and a message indicating that the first UE failed to receive the data packet may be transmitted to a third UE. In some cases, the transmission may be determined to be weak based on the transmission being below a received signal energy threshold.

Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: one or more resources for resource reservation are selected. In some cases, the message indicating that the first UE failed to receive the data packet includes a resource reservation. In some cases, the data packet may be received on one or more resources indicated by the resource reservation.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, the message indicating that the first UE failed to receive the data packet includes a source Identifier (ID) indicating the second UE or a packet ID indicating the data packet, or both.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, receiving the data packet may include operations, features, apparatuses, or instructions to: a data packet is received from the third UE based on the source ID or the packet ID, or both.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, the message indicating that the first UE failed to receive the data packet may include an exclusion range of reserved resources, a Modulation and Coding Scheme (MCS), a transmission mode, a redundancy version, a reference signal pattern, or a combination thereof. In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, receiving the data packet may include operations, features, apparatuses, or instructions to: receiving a data packet from the third UE based on the excluded extent of the reserved resources, the MCS, the transmission mode, the RV, the reference signal mode, or a combination thereof.

Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: receiving a data packet from a fourth UE different from the second UE and the third UE based on a message indicating failure of the first UE to receive the data packet. Some examples may further include operations, features, means, or instructions for: decoding the data packet based on combining information corresponding to receiving the data packet from the third UE and information corresponding to receiving the data packet from the fourth UE.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, the message indicating that the first UE failed to receive the data packet comprises a NAK message or a request for the data packet, or both.

A method for wireless communication at a first UE is described. The method can comprise the following steps: receiving a data packet from a second UE; receiving a message from a third UE indicating a failure of the third UE to receive the data packet; and relaying the data packet to the third UE based on the message indicating failure of the third UE to receive the data packet.

An apparatus for wireless communication at a first UE is described. The apparatus may include a processor and a memory coupled to the processor. The processor and memory may be configured to: receiving a data packet from a second UE; receiving a message from a third UE indicating a failure of the third UE to receive the data packet; and relaying the data packet to the third UE based on the message indicating failure of the third UE to receive the data packet.

Another apparatus for wireless communication at a first UE is described. The apparatus may include means for: receiving a data packet from a second UE; receiving a message from a third UE indicating a failure of the third UE to receive the data packet; and relaying the data packet to the third UE based on the message indicating failure of the third UE to receive the data packet.

A non-transitory computer-readable medium storing code for wireless communication at a first UE is described. The code may include instructions executable by a processor for: receiving a data packet from a second UE; receiving a message from a third UE indicating a failure of the third UE to receive the data packet; and relaying the data packet to the third UE based on the message indicating failure of the third UE to receive the data packet.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, the message indicating that the third UE failed to receive the data packet comprises a resource reservation. Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: one or more resources indicated by the resource reservation are determined. Some examples may further include operations, features, means, or instructions for: determining to relay the data packet to the third UE based on the first UE supporting transmission on the one or more resources. In some cases, the data packet may be relayed to the third UE on one or more resources indicated by the resource reservation.

Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: a Reference Signal Received Power (RSRP) for receiving a message indicating a failure of a third UE to receive a data packet is determined. Some examples may further include operations, features, means, or instructions for: determining to relay the data packet to the third UE based on the determined RSRP being greater than the RSRP threshold.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, the message indicating the failure of the third UE to receive the data packet may include operations, features, means, or instructions to: the RSRP threshold is determined based on a message indicating failure of the third UE to receive the data packet.

Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: adjusting a power control parameter for relaying the data packet to the third UE based on the determined RSRP.

Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: receiving a message from the fourth UE indicating a failure of the fourth UE to receive the additional data packet. In some cases, the message indicating that the fourth UE failed to receive the additional data packet includes a resource reservation. Some examples may further include operations, features, means, or instructions for: determining to refrain from relaying the additional data packet to the fourth UE in the one or more resources indicated by the resource reservation. Some examples may further include operations, features, means, or instructions for: refraining from communicating on one or more resources that overlap with one or more resources indicated by the resource reservation based on the resource reservation.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, the data packet may be received from the second UE according to an MCS, a spatial multiplexing scheme, and a demodulation reference signal pattern. In some cases, relaying the data packet to the third UE may include operations, features, means, or instructions for: relaying the data packet to the third UE according to the MCS, the spatial multiplexing scheme, the demodulation reference signal mode, or a combination thereof.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, the data packet may be received from the second UE according to the first MCS, the first spatial multiplexing scheme, and the first demodulation reference signal pattern. In some cases, relaying the data packet to the third UE may include operations, features, means, or instructions for: relaying the data packet to the third UE according to a second MCS different from the first MCS, a second spatial multiplexing scheme different from the first spatial multiplexing scheme, a second demodulation reference signal mode different from the first demodulation reference signal mode, or a combination thereof.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, the message indicating the failure of the third UE to receive the data packet may include operations, features, means, or instructions to: determining a second MCS, a second spatial multiplexing scheme, a second demodulation reference signal mode, or a combination thereof based on the message indicating the failure of the third UE to receive the data packet.

Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: the method further includes determining a distance between the first UE and the third UE, and determining to relay the data packet to the third UE based on the determined distance being less than a distance threshold.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, the message indicating the failure of the third UE to receive the data packet may include operations, features, means, or instructions to: relaying the data packet to the third UE based on the source ID, the packet ID, the exclusion range of the reserved resources, the transmission mode, the RV, the reference signal mode, or a combination thereof.

In some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein, the message indicating that the third UE failed to receive the data packet comprises a NAK message or a request for the data packet, or both.

A method for wireless communication at a first UE is described. The method can comprise the following steps: scheduling transmission of the data packet in one or more resources to the second UE and the third UE; transmitting control information to the second UE and the third UE, the control information including a resource reservation indicating the one or more resources and including an indication enabling the second UE to relay the data packet to the third UE in response to a message indicating failure of the third UE to receive the data packet; and transmitting the data packet to the second UE and the third UE in the one or more resources.

An apparatus for wireless communication at a first UE is described. The apparatus may include a processor and a memory coupled to the processor. The processor and memory may be configured to: scheduling transmission of the data packet in one or more resources to the second UE and the third UE; transmitting control information to the second UE and the third UE, the control information including a resource reservation indicating the one or more resources and including an indication enabling the second UE to relay the data packet to the third UE in response to a message indicating failure of the third UE to receive the data packet; and transmitting the data packet to the second UE and the third UE in the one or more resources.

Another apparatus for wireless communication at a first UE is described. The apparatus may include means for: scheduling transmission of the data packet in one or more resources to the second UE and the third UE; transmitting control information to the second UE and the third UE, the control information including a resource reservation indicating the one or more resources and including an indication enabling the second UE to relay the data packet to the third UE in response to a message indicating failure of the third UE to receive the data packet; and transmitting the data packet to the second UE and the third UE in the one or more resources.

A non-transitory computer-readable medium storing code for wireless communication at a first UE is described. The code may include instructions executable by a processor for: scheduling transmission of the data packet in one or more resources to the second UE and the third UE; transmitting control information to the second UE and the third UE, the control information including a resource reservation indicating the one or more resources and including an indication enabling the second UE to relay the data packet to the third UE in response to a message indicating failure of the third UE to receive the data packet; and transmitting the data packet to the second UE and the third UE in the one or more resources.

Some examples of the methods, apparatuses (devices), and non-transitory computer-readable media described herein may further include operations, features, apparatuses, or instructions to: the data packet is received from the second UE based on a message indicating failure of the third UE to receive the data packet.

Brief Description of Drawings

Fig. 1 and 2 illustrate examples of a wireless communication system supporting on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure.

Fig. 3 illustrates an example of a process flow to support on-demand relaying of messages for side-link communication in accordance with one or more aspects of the present disclosure.

Fig. 4 and 5 illustrate block diagrams of devices that support on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure.

Fig. 6 illustrates a block diagram of a communication manager that supports on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure.

Fig. 7 illustrates a diagram of a system including devices that support on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure.

Fig. 8-15 show flow diagrams illustrating methods of supporting on-demand relaying of messages for side-link communications according to one or more aspects of the present disclosure.

Detailed Description

In some wireless communication systems (e.g., V2X systems or D2D systems, etc.), UEs may communicate with each other via sidelink communications. In some examples, these UEs may be examples of vehicles in the V2X system. However, in some cases, certain effects (such as shadowing and blocking) may reduce the reliability of communication between UEs. In the case of shadowing and blocking, the received signal power at the UE fluctuates due to the object obstructions of the propagation path between the transmitter and receiver of the signal. Both shadowing and blocking can be measured in decibels (dB). If shadowing occurs, the path loss may be about 7dB, and blocking may result in a path loss of about 10-15 dB. Shadowing may result from a recipient UE being located under an object covering a large area (e.g., an object such as a large building may shadow the UE). The blockage may be caused by an object located in a direct path between the transmitting UE and the receiving UE (e.g., an object such as a truck or other vehicle may block the UE). In some cases, there may be multiple blockers (e.g., more than one blocker or obstacle) between the transmitter and receiver and may result in a path loss of about 30 dB. Both shadowing and blocking can result in strong signal attenuation.

The blocking, shadowing, or a combination thereof may result in sufficient signal attenuation such that the receiving party may not be able to receive the data packet from the source transmitter. In some cases, the source transmitter may retransmit the packet; however, the retransmission may continue to be affected by the blocking or shadowing. The number of repetitions and increased transmit power required for the receiver to successfully receive the packet (i.e., overcome the blockage, shadowing, or both) may use an over-provisioning of resources and result in significant latency in the system. In some cases, multiple packet retransmissions with increased transmit power may cause signal collisions and interference at other UEs. Interference and latency due to blocking and shadowing can lead to performance degradation in wireless communication systems.

In some wireless communication systems (e.g., systems supporting V2X communication, D2D communication, or both), a UE may communicate on a sidelink communication channel using techniques for mitigating the effects of blocking/shadowing. These UEs may be examples or components of vehicles or other wireless devices, and the sidelink communications may be referred to as V2X, vehicle-to-vehicle (V2V), or D2D communications. In some cases, the communication may involve the transmitting UE multicasting a packet, where one or more receiving UEs within a target range may monitor and receive the packet. However, in some examples, for one or more UEs, packet reception at the target range may fail due to shadowing, blocking, or a combination thereof. It should be understood that blocking and masking may be used interchangeably herein, and any description relating to blocking may also be applied to masking (and vice versa).

If the recipient UE identifies that it failed to receive the transmitted packet (e.g., due to congestion or shadowing), the recipient UE may transmit a signal requesting retransmission of the missing packet (e.g., using a NAK message). The request may indicate that the recipient UE failed to receive the packet and that further retransmission of the packet should be sent. In some cases, the transmitting UE may not receive the request due to shadowing, blocking, or a combination thereof. In other cases, the transmitting UE may receive the request, but the performance gain obtained by the transmitting UE retransmitting packets may be limited if the retransmission to the receiving UE continues to be obscured, blocked, or both. Furthermore, if the number of resources or transmit power or both for a retransmission are significantly increased in order to reach the receiving UE, the retransmission may cause collisions with other signals and interference to other UEs throughout the network, degrading performance in the network.

To increase the reliability of successful reception of the packet by the recipient UE, the recipient UE may multicast a request for retransmission of the packet. One or more other UEs (e.g., instead of or in addition to the transmitting UE) may receive the request for retransmission. In some cases, at least one of the UEs may have successfully received a packet from the transmitting UE during the multicast transmission (e.g., if the UE is not blocked or obscured). Any UE that successfully receives a packet and receives a request for retransmission may determine whether to relay the packet to a recipient UE that failed to receive the packet. For example, the UE may determine to relay the packet to the recipient UE based on a link quality with the recipient UE or a distance to the recipient UE, or both. The relay UE may relay the packet to the recipient UE based on the request for retransmission. In some cases, the signal path from the relay UE to the receiving UE may not be blocked or obscured (e.g., even if the signal path from the transmitting UE to the receiving UE is blocked, obscured, or both). As such, relaying packets may increase the probability of successfully receiving the packets at the receiving UE.

Aspects of the present disclosure are initially described in the context of a wireless communication system. Specific examples of on-demand relaying of messages in sidelink (e.g., V2X, D2D, V2V, etc.) communication systems are described subsequently. Aspects of the present disclosure are further illustrated and described by, and with reference to, apparatus diagrams, system diagrams, and flow charts relating to on-demand relaying of messages for sidelink communications.

Fig. 1 illustrates an example of a wireless communication system 100 that supports on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. The wireless communication system 100 includes base stations 105, UEs 115, and a core network 130. In some examples, the wireless communication system 100 may be an LTE network, an LTE-a Pro network, or a New Radio (NR) network. In some cases, wireless communication system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, or communications with low cost and low complexity devices.

The base station 105 may communicate wirelessly with the UE115 via one or more base station antennas. The base stations 105 described herein may include or may be referred to by those skilled in the art as base transceiver stations, radio base stations, access points, radio transceivers, node bs, evolved node bs (enbs), next generation node bs or gigabit node bs (any of which may be referred to as gnbs), home node bs, home evolved node bs, or some other suitable terminology. The wireless communication system 100 may include different types of base stations 105 (e.g., macro cell base stations or small cell base stations). The UEs 115 described herein may be capable of communicating with various types of base stations 105 and network equipment, including macro enbs, small cell enbs, gbbs, relay base stations, and so forth.

Each base station 105 may be associated with a particular geographic coverage area 110, supporting communication with various UEs 115 in that particular geographic coverage area 110. Each base station 105 may provide communication coverage for a respective geographic coverage area 110 via a communication link 125, and the communication link 125 between the base station 105 and the UE115 may utilize one or more carriers. The communication links 125 shown in the wireless communication system 100 may include uplink transmissions from the UEs 115 to the base stations 105 or downlink transmissions from the base stations 105 to the UEs 115. Downlink transmissions may also be referred to as forward link transmissions, and uplink transmissions may also be referred to as reverse link transmissions.

The geographic coverage area 110 of a base station 105 can be divided into sectors that form a portion of the geographic coverage area 110, and each sector can be associated with a cell. For example, each base station 105 may provide communication coverage for a macro cell, a small cell, a hot spot, or other type of cell, or various combinations thereof. In some examples, the base stations 105 may be mobile and thus provide communication coverage for a moving geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, and the overlapping geographic coverage areas 110 associated with different technologies may be supported by the same base station 105 or different base stations 105. The wireless communication system 100 may include, for example, a heterogeneous LTE/LTE-A/LTE-A Pro or NR network in which different types of base stations 105 provide coverage for various geographic coverage areas 110.

The term "cell" refers to a logical communication entity for communicating with a base station 105 (e.g., on a carrier) and may be associated with an identifier to distinguish between neighboring cells (e.g., Physical Cell Identifier (PCID), Virtual Cell Identifier (VCID)) operating via the same or different carriers. In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., Machine Type Communication (MTC), narrowband internet of things (NB-IoT), enhanced mobile broadband (eMBB), or others) that may provide access for different types of devices. In some cases, the term "cell" may refer to a portion (e.g., a sector) of geographic coverage area 110 over which a logical entity operates.

The UEs 115 may be dispersed throughout the wireless communication system 100, and each UE115 may be stationary or mobile. A UE115 may also be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where a "device" may also be referred to as a unit, station, terminal, or client. The UE115 may also be a personal electronic device, such as a cellular telephone, a Personal Digital Assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, the UE115 may also refer to a Wireless Local Loop (WLL) station, an internet of things (IoT) device, an internet of everything (IoE) device, or an MTC device, among others, which may be implemented in various items such as appliances, vehicles, meters, and so forth.

Some UEs 115, such as MTC or IoT devices, may be low cost or low complexity devices and may provide automated communication between machines (e.g., communication via machine-to-machine (M2M)). M2M communication or MTC may refer to data communication techniques that allow devices to communicate with each other or with the base station 105 without human intervention. In some examples, M2M communications or MTC may include communications from devices that integrate sensors or meters to measure or capture information and relay the information to a central server or application that may utilize the information or present the information to a person interacting with the program or application. Some UEs 115 may be designed to collect information or implement automated behavior of a machine. Examples of applications for MTC devices include: smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, field survival monitoring, weather and geographic event monitoring, queue management and tracking, remote security sensing, physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ a reduced power consumption mode of operation, such as half-duplex communications (e.g., a mode that supports unidirectional communication via transmission or reception but does not simultaneously transmit and receive). In some examples, half-duplex communication may be performed with a reduced peak rate. Other power saving techniques for the UE115 include entering a power saving "deep sleep" mode when not engaged in active communication, or operating on a limited bandwidth (e.g., according to narrowband communication). In some cases, the UE115 may be designed to support critical functions (e.g., mission critical functions), and the wireless communication system 100 may be configured to provide ultra-reliable communication for these functions.

In some cases, the UE115 may also be able to communicate directly with other UEs 115 (e.g., using peer-to-peer (P2P) or D2D protocols). One or more UEs of the group of UEs 115 communicating with D2D may be within the geographic coverage area 110 of the base station 105. The other UEs 115 in the group may be outside the geographic coverage area 110 of the base station 105 or otherwise unable to receive transmissions from the base station 105. In some cases, groups of UEs 115 communicating via D2D may utilize a one-to-many (1: M) system, where each UE115 transmits to every other UE115 in the group. In some cases, the base station 105 facilitates scheduling of resources for D2D communication. In other cases, D2D communication is performed between UEs 115 without involving base stations 105.

The base stations 105 may communicate with the core network 130 and with each other. For example, the base stations 105 may interface with the core network 130 over backhaul links 132 (e.g., via S1, N2, N3, or other interfaces). The base stations 105 may communicate with each other over backhaul links 134 (e.g., via X2, Xn, or other interfaces) directly (e.g., directly between base stations 105) or indirectly (e.g., via the core network 130). UE115 may communicate with core network 130 via communication link 135.

The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an Evolved Packet Core (EPC) that may include at least one Mobility Management Entity (MME), at least one serving gateway (S-GW), and at least one Packet Data Network (PDN) gateway (P-GW). The MME may manage non-access stratum (e.g., control plane) functions such as mobility, authentication, and bearer management for UEs 115 served by base stations 105 associated with the EPC. User IP packets may be communicated through the S-GW, which may itself be connected to the P-GW. The P-GW may provide IP address allocation as well as other functions. The P-GW may be connected to network operator IP services. The operator IP services may include access to the internet, intranets, IP Multimedia Subsystem (IMS), or Packet Switched (PS) streaming services.

At least some network devices, such as base stations 105, may include subcomponents, such as access network entities, which may be examples of Access Node Controllers (ANCs). Each access network entity may communicate with UEs 115 through a number of other access network transport entities, which may be referred to as radio heads, intelligent radio heads, or transmission/reception points (TRPs). In some configurations, the various functions of each access network entity or base station 105 may be distributed across various network devices (e.g., radio heads and access network controllers) or consolidated into a single network device (e.g., base station 105).

Wireless communication system 100 may operate using one or more frequency bands, such as in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). The 300MHz to 3GHz region may be referred to as the Ultra High Frequency (UHF) region or the decimeter band because the wavelengths range from about 1 to 1 meter long. UHF waves can be blocked or redirected by building and environmental features. However, these waves may penetrate a variety of structures sufficiently for a macro cell to provide service to a UE115 located indoors. UHF-wave transmission can be associated with smaller antennas and shorter ranges (e.g., less than 100km) than transmission using smaller and longer waves of the High Frequency (HF) or Very High Frequency (VHF) portions of the spectrum below 300 MHz.

The wireless communication system 100 may also operate in the ultra-high frequency (SHF) region using a frequency band from 3GHz to 30GHz, also referred to as a centimeter frequency band. The SHF region includes frequency bands (such as the 5GHz industrial, scientific, and medical (ISM) frequency bands) that may be opportunistically used by devices that may be able to tolerate interference from other users.

The wireless communication system 100 may also operate in the Extremely High Frequency (EHF) region of the spectrum (e.g., from 30GHz to 300GHz), which is also referred to as the millimeter-band. In some examples, the wireless communication system 100 may support millimeter wave (mmW) communication between the UE115 and the base station 105, and EHF antennas of respective devices may be even smaller and more closely spaced than UHF antennas. In some cases, this may facilitate the use of antenna arrays within the UE 115. However, propagation of EHF transmissions may experience even greater atmospheric attenuation and shorter ranges than SHF or UHF transmissions. The techniques disclosed herein may be employed across transmissions using one or more different frequency regions, and the frequency band usage designated across these frequency regions may differ by country or regulatory agency.

In some cases, the wireless communication system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communication system 100 may employ Licensed Assisted Access (LAA), LTE unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band, such as the 5GHz ISM band. When operating in the unlicensed radio frequency spectrum band, wireless devices, such as base stations 105 and UEs 115, may employ a Listen Before Talk (LBT) procedure to ensure that frequency channels are clear before transmitting data. In some cases, operation in the unlicensed band may be based on a carrier aggregation configuration (e.g., LAA) in coordination with component carriers operating in the licensed band. Operations in the unlicensed spectrum may include downlink transmissions, uplink transmissions, peer-to-peer transmissions, or a combination of these. Duplexing in the unlicensed spectrum may be based on Frequency Division Duplexing (FDD), Time Division Duplexing (TDD), or a combination of both.

In some examples, a base station 105 or UE115 may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. For example, the wireless communication system 100 may use a transmission scheme between a transmitting device (e.g., base station 105) equipped with multiple antennas and a receiving device (e.g., UE 115) equipped with one or more antennas. MIMO communication may employ multipath signal propagation to increase spectral efficiency by transmitting or receiving multiple signals via different spatial layers, which may be referred to as spatial multiplexing. For example, a transmitting device may transmit multiple signals via different antennas or different combinations of antennas. Also, the receiving device may receive multiple signals via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams. Different spatial layers may be associated with different antenna ports for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO), in which multiple spatial layers are transmitted to the same receiver device; and multi-user MIMO (MU-MIMO), in which a plurality of spatial layers are transmitted to a plurality of devices.

Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting or receiving device (e.g., base station 105 or UE 115) to shape or steer an antenna beam (e.g., a transmit beam or a receive beam) along a spatial path between the transmitting and receiving devices. Beamforming may be achieved by combining signals communicated via antenna elements of an antenna array such that signals propagating in a particular orientation relative to the antenna array undergo constructive interference while other signals undergo destructive interference. The adjustment to the signals communicated via the antenna elements may include the transmitting or receiving device applying a particular amplitude and phase shift to the signals carried via each antenna element associated with the device. The adjustment associated with each antenna element may be defined by a set of beamforming weights associated with a particular orientation (e.g., relative to an antenna array of a transmitting device or a receiving device, or relative to some other orientation).

In one example, the base station 105 may use multiple antennas or antenna arrays for beamforming operations for directional communication with the UEs 115. For example, some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted multiple times in different directions by the base station 105, which may include a signal being transmitted according to different sets of beamforming weights associated with different transmission directions. Transmissions in different beam directions may be used (e.g., by the base station 105 or a receiving device, such as UE 115) to identify beam directions used by the base station 105 for subsequent transmission and/or reception.

Some signals, such as data signals associated with a particular recipient device, may be transmitted by the base station 105 in a single beam direction (e.g., a direction associated with the recipient device, such as the UE 115). In some examples, a beam direction associated with transmission along a single beam direction may be determined based at least in part on signals transmitted in different beam directions. For example, the UE115 may receive one or more signals transmitted by the base station 105 in different directions, and the UE115 may report an indication to the base station 105 of the signal that the UE115 receives at the highest signal quality or other acceptable signal quality. Although the techniques are described with reference to signals transmitted by the base station 105 in one or more directions, the UE115 may use similar techniques for transmitting signals multiple times in different directions (e.g., to identify beam directions used by the UE115 for subsequent transmission or reception) or for transmitting signals in a single direction (e.g., for transmitting data to a receiving device).

A receiving device (e.g., UE115, which may be an example of a mmW receiving device) may attempt multiple receive beams when receiving various signals from base station 105, such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a recipient device may attempt multiple receive directions by: receiving via different antenna sub-arrays, processing received signals according to different antenna sub-arrays, receiving according to different sets of receive beamforming weights applied to signals received at multiple antenna elements of an antenna array, or processing received signals according to different sets of receive beamforming weights applied to signals received at multiple antenna elements of an antenna array, either of which may be referred to as "listening" according to different receive beams or receive directions. In some examples, the receiving device may use a single receive beam to receive along a single beam direction (e.g., when receiving a data signal). The single receive beam may be aligned in a beam direction determined based on listening from different receive beam directions (e.g., the beam direction determined to have the highest signal strength, highest signal-to-noise ratio, or other acceptable signal quality based on listening from multiple beam directions).

In some cases, the antennas of a base station 105 or UE115 may be located within one or more antenna arrays that may support MIMO operation or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly (such as an antenna tower). In some cases, the antennas or antenna arrays associated with the base station 105 may be located at different geographic locations. The base station 105 may have an antenna array with a number of rows and columns of antenna ports that the base station 105 may use to support beamforming for communications with the UEs 115. Likewise, the UE115 may have one or more antenna arrays that may support various MIMO or beamforming operations.

In some cases, the wireless communication system 100 may be a packet-based network operating according to a layered protocol stack. In the user plane, communication of the bearer or Packet Data Convergence Protocol (PDCP) layer may be IP-based. The Radio Link Control (RLC) layer may perform packet segmentation and reassembly to communicate on logical channels. The Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat request (HARQ) to provide retransmission by the MAC layer, thereby improving link efficiency. In the control plane, a Radio Resource Control (RRC) protocol layer may provide for establishment, configuration, and maintenance of RRC connections of radio bearers supporting user plane data between the UE115 and the base station 105 or core network 130. At the physical layer, transport channels may be mapped to physical channels.

In some cases, the UE115 and the base station 105 may support retransmission of data to increase the likelihood that the data is successfully received. HARQ feedback is a technique that increases the likelihood that data will be correctly received on the communication link 125. HARQ may include a combination of error detection (e.g., using Cyclic Redundancy Check (CRC)), Forward Error Correction (FEC), and retransmission (e.g., automatic repeat request (ARQ)). HARQ may improve throughput of the MAC layer in poor radio conditions (e.g., signal-to-noise conditions). In some cases, a wireless device may support simultaneous slot HARQ feedback, where the device may provide HARQ feedback in a particular slot for data received in a previous symbol in that slot. In other cases, the device may provide HARQ feedback in subsequent time slots or according to some other time interval.

The time interval in LTE or NR may be in a basic unit of time (which may for example refer to the sampling period T)_s1/30,720,000 seconds). The time intervals of the communication resources may be organized according to radio frames each having a duration of 10 milliseconds (ms), where the frame period may be expressed as T_f＝307,200T_s. The radio frame may be identified by a System Frame Number (SFN) ranging from 0 to 1023. Each frame may include 10 subframes numbered from 0 to 9, and each subframe may have a duration of 1 ms. A subframe may be further divided into 2 slots, each having a duration of 0.5ms, and each slot may contain 6 or 7 modulation symbol periods (e.g., depending on the length of the cyclic prefix preceding each symbol period). Each symbol period may contain 2048 sample periods, excluding the cyclic prefix. In some cases, a subframe may be the smallest scheduling unit of the wireless communication system 100 and may be referred to as a Transmission Time Interval (TTI). In other cases, the minimum scheduling unit of the wireless communication system 100 may be shorter than a subframe or may be dynamically selected (e.g., in a burst of shortened tti (sTTI) or in a selected component carrier using sTTI).

In some wireless communication systems, a slot may be further divided into a plurality of mini-slots containing one or more symbols. In some examples, a symbol of a mini-slot or a mini-slot may be a minimum scheduling unit. For example, each symbol may vary in duration depending on the subcarrier spacing or operating frequency band. Further, some wireless communication systems may implement timeslot aggregation, where multiple timeslots or mini-timeslots are aggregated together and used for communication between the UE115 and the base station 105.

The term "carrier" refers to a set of radio frequency spectrum resources having a defined physical layer structure for supporting communications over the communication link 125. For example, the carrier of the communication link 125 may comprise a portion of a radio frequency spectrum band operating according to a physical layer channel for a given radio access technology. Each physical layer channel may carry user data, control information, or other signaling. The carriers may be associated with predefined frequency channels (e.g., evolved universal mobile telecommunications system terrestrial radio access (E-UTRA) absolute radio frequency channel numbers (EARFCNs)) and may be located according to a channel grid for discovery by UEs 115. The carriers may be downlink or uplink (e.g., in FDD mode), or configured to carry downlink and uplink communications (e.g., in TDD mode). In some examples, a signal waveform transmitted on a carrier may include multiple subcarriers (e.g., using multicarrier modulation (MCM) techniques such as Orthogonal Frequency Division Multiplexing (OFDM) or discrete fourier transform spread OFDM (DFT-S-OFDM)).

The organization of the carriers may be different for different radio access technologies (e.g., LTE-A, LTE-A Pro, NR). For example, communications on a carrier may be organized according to TTIs or slots, each of which may include user data as well as control information or signaling supporting decoding of the user data. The carrier may also include dedicated acquisition signaling (e.g., synchronization signals or system information) and control signaling to coordinate carrier operation. In some examples (e.g., in a carrier aggregation configuration), a carrier may also have acquisition signaling or control signaling that coordinates the operation of other carriers.

The physical channels may be multiplexed on the carriers according to various techniques. The physical control channels and physical data channels may be multiplexed on the downlink carrier using, for example, Time Division Multiplexing (TDM) techniques, Frequency Division Multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, control information transmitted in the physical control channel may be distributed in a cascaded manner between different control regions (e.g., between a common control region or common search space and one or more UE-specific control regions or UE-specific search spaces).

A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples, the carrier bandwidth may be referred to as a carrier or "system bandwidth" of the wireless communication system 100. For example, the carrier bandwidth may be one of several predetermined bandwidths (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80MHz) of a carrier of a particular radio access technology. In some examples, each served UE115 may be configured to operate over part or all of the carrier bandwidth. In other examples, some UEs 115 may be configured for operation using a narrowband protocol type associated with a predefined portion or range within a carrier (e.g., a set of subcarriers or RBs) (e.g., "in-band" deployment of narrowband protocol types).

In a system employing MCM technology, a resource element may include one symbol period (e.g., the duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme). Thus, the more resource elements the UE115 receives and the higher the order of the modulation scheme, the higher the data rate of the UE115 may be. In a MIMO system, wireless communication resources may refer to a combination of radio frequency spectrum resources, time resources, and spatial resources (e.g., spatial layers), and using multiple spatial layers may further improve the data rate of communication with the UE 115.

Devices of the wireless communication system 100 (e.g., base stations 105 or UEs 115) may have a hardware configuration that supports communication over a particular carrier bandwidth or may be configurable to support communication over one carrier bandwidth of a set of carrier bandwidths. In some examples, the wireless communication system 100 may include a base station 105 and/or a UE115 that supports simultaneous communication via carriers associated with more than one different carrier bandwidth.

The wireless communication system 100 may support communication with UEs 115 over multiple cells or carriers, a feature that may be referred to as carrier aggregation or multi-carrier operation. The UE115 may be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used with both FDD and TDD component carriers.

In some cases, the wireless communication system 100 may utilize an enhanced component carrier (eCC). An eCC may be characterized by one or more characteristics including a wider carrier or frequency channel bandwidth, a shorter symbol duration, a shorter TTI duration, or a modified control channel configuration. In some cases, an eCC may be associated with a carrier aggregation configuration or a dual connectivity configuration (e.g., when multiple serving cells have suboptimal or non-ideal backhaul links). An eCC may also be configured for use in unlicensed spectrum or shared spectrum (e.g., where more than one operator is allowed to use the spectrum). An eCC characterized by a wide carrier bandwidth may include one or more segments that may be utilized by UEs 115 that are unable to monitor the entire carrier bandwidth or are otherwise configured to use a limited carrier bandwidth (e.g., to conserve power).

In some cases, an eCC may utilize a different symbol duration than other component carriers, which may include using a reduced symbol duration compared to the symbol duration of the other component carriers. Shorter symbol durations may be associated with increased spacing between adjacent subcarriers. Devices utilizing an eCC, such as UE115 or base station 105, may transmit a wideband signal (e.g., according to a frequency channel or carrier bandwidth of 20, 40, 60, 80MHz, etc.) with a reduced symbol duration (e.g., 16.67 microseconds). A TTI in an eCC may include one or more symbol periods. In some cases, the TTI duration (i.e., the number of symbol periods in a TTI) may be variable.

The wireless communication system 100 may be an NR system that may utilize any combination of licensed, shared, and unlicensed spectrum bands, etc. Flexibility in eCC symbol duration and subcarrier spacing may allow eCC to be used across multiple spectra. In some examples, NR sharing spectrum may improve spectrum utilization and spectral efficiency, particularly through dynamic vertical (e.g., across frequency domains) and horizontal (e.g., across time domains) sharing of resources.

In some wireless communication systems 100, sidelink communications (e.g., V2X communications, D2D communications, or any other sidelink communications) may be used to support messaging between UEs 115. In some cases, a UE115 (e.g., a vehicle) may transmit data packets to surrounding UEs 115 via a multicast transmission. However, an object (e.g., UE115, another device, an object in nature, or any other object) may prevent such signals from reaching the intended recipient. Thus, a portion of the receiving UE115 may be unable to receive data packets in sidelink transmissions due to interference, blocking, shadowing, or a combination thereof. Specifically, one UE115 may be unable to receive packets due to congestion, while other UEs 115 in the area may receive packets.

The blocked UE115 may determine that it cannot receive packets from the source UE115 and may transmit the request in a multicast transmission so that neighboring UEs 115 may receive the request. The request may instruct the neighboring UE115 to transmit packets to the blocked UE 115. The relay request manager 101 (e.g., an example or component of a communication manager as described with reference to fig. 4-7) may process the request. The neighboring UEs 115 may receive the request, determine whether they have received the desired packet, and determine whether to relay the packet. For example, the UE115 may determine to act as a relay UE115 if the UE115 is close enough to the blocked UE115 based on the location information of both UEs 115, if the UE115 has a strong enough link quality with the blocked UE115 based on the requested RSRP, or some combination thereof. A UE115 that has previously received a data packet from the source UE115 and determined to be a valid relay UE for the blocked UE115 may transmit (i.e., relay) packets to the blocked UE115 based on the request. Depending on the location of the UE115 and the obstruction(s) in the system, while transmissions from the original source UE115 to the blocked UE115 may be blocked, transmissions from the relay UE115 to the blocked UE115 may be successful.

Fig. 2 illustrates an example of a wireless communication system 200 that supports on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. In some examples, the wireless communication system 200 may implement aspects of the wireless communication system 100. The wireless communication system 200 may include UEs 115-a, 115-b, 115-c, and 115-d, which may be examples of UEs 115 as described with reference to FIG. 1. In some cases, UE115 may be an example of a vehicle in a V2X system. In other cases, UE115 may be an example of a wireless device in a D2D system. In some examples, UE 115-c may implement an on-demand procedure for requesting a blocked data packet. For example, the UE 115-a may transmit a request to the relay UE 115-d via the sidelink 225, and the UE 115-d may relay the packet to the UE 115-c based on the request. Additionally or alternatively, other wireless devices (such as the UEs 115-a, 115-b or some combination of these UEs 115) may implement on-demand relaying of data packets requested due to congestion.

In sidelink communications, data packets may be transmitted via multicast transmission such that the source UE 115-a may transmit the packets and multiple UEs within target range (e.g., UEs 115-b, 115-c, 115-d, etc.) may monitor the data packets. For one or more UEs 115, packet reception at the target range may fail due to shadowing, blocking, interference, or a combination thereof. However, packets may be received at other UEs 115 that are not blocked, shadowed, or experience significant interference. For example, the source UE 115-a may transmit packets via sidelinks 210 and 220 in a multicast transmission. However, in some cases, transmissions to the recipient UE 115-c (e.g., on the sidelink 210) may be blocked by some obstruction, such as the UE 115-b or some other device, structure, or the like. In these cases, the transmitted packet may not arrive on the sidelink 210 at the intended recipient at the UE 115-c with sufficient signal strength for the UE 115-c to successfully receive and decode the packet. In some cases, the UE 115-d may successfully receive packets in the multicast transmission from the source UE 115-a via the sidelink 220 (e.g., due to positioning of obstructions in the system).

The failure of data packet reception in the system may be due to interference or due to blocking/shadowing. In some cases, the source UE 115-a, the recipient UE 115-c, or both may identify when a packet reception failure occurs. The transmitting UE 115-a may transmit a control message including control information indicating resources for transmission of data packets. If the receiving UE 115-c is capable of decoding the control message or channel but is not capable of receiving and decoding the data packet in the indicated resource, the receiving UE 115-c may determine that the receiving UE 115-c has lost the transmitted packet.

In some examples, the source UE 115-a, the recipient UE 115-c, or both, may determine a reason for the packet reception failure. For example, if the UE 115-c is capable of decoding control information instead of data, the UE 115-c may determine whether the decoding failure of the data packet is due to interference. In one scenario, the path between the transmitting party (e.g., at source UE 115-a) and UE 115-c may be unobstructed, but the data may be interference limited. This may be determined if the UE 115-c is able to decode multiple (e.g., two) control messages corresponding to multiple (e.g., two) overlapping data transmissions by different transmitters that are too close to each other (and interfere with each other). In another scenario, the UE 115-c may determine that the packet decoding failure is due to interference if the data packet decoding fails and the RSRP of the link quality or the Reference Signal Received Quality (RSRQ) measurement is above a certain threshold. In these cases, the transmitting party may retransmit the data packet at a later time when interference may be reduced. In other cases, the packet decoding failure may be due to blocking, shadowing, or a combination thereof. For example, if the UE 115-c does not determine that the packet decoding failure is due to interference, the UE 115-c may determine that the packet decoding failure is due to blocking/shadowing. In some cases, the UE 115-c may analyze the expected cause of the decoding failure. In other cases, UE 115-c may not perform the analysis.

If the receiving UE 115-c measures a weak RSRP or RSRQ or both, the receiving UE 115-c may determine that packet reception failed due to a weak link between the UE 115-c and the transmitting party (e.g., UE 115-a). In some cases, the weak link may be due to blocking or shadowing. If the remaining delay budget of the packet is low (e.g., below the delay budget threshold), the receiving UE 115-c may transmit a NAK message, which may include a retransmission request for the data packet, to the transmitting UE 115-a. The delay budget specifies an allowed amount of time for which the data packet is to be delayed between scheduled transmission and reception. In some cases, the receiving UE 115-c may determine that the transmitting UE scheduled one or more retransmissions of the packet (e.g., reserved resources for the next transmission based on bits or fields in the decoded control information), and the receiving UE 115-c may monitor the packet in resources scheduled for retransmission.

If the source UE 115-a has no further scheduled retransmissions of the packet, the source UE 115-a may indicate the last transmission of its packet (e.g., using a bit or field in the control information). In some cases, the transmission via the sidelink 210 may still be blocked from successfully reaching the UE 115-c. If the UE 115-c fails to receive the packet, the blocked UE 115-c may transmit a signal to request the packet. In some cases, the UE 115-c may transmit the request if no more retransmissions of the packet are scheduled, if the remaining delay budget for the packet allows (e.g., above a certain threshold), or if some combination of these conditions are met. The signal requesting the packet may be transmitted via multicast or unicast transmission. The blocked UE 115-c may transmit the request, and the UE 115-d may receive the request via the sidelink 225. In some cases, the request may be blocked from reaching the source UE 115-a via the sidelink 235 (e.g., due to the hindering UE 115-b). In other cases, the UE 115-a may also receive the request if there is no longer an obstacle between the UE 115-c and the UE 115-a.

The request may include a source ID of the source UE 115-a, a packet ID of the requested data packet, an RSRP threshold used to determine whether the link quality is strong enough to relay the packet, reserved resources on which to send the relay packet, any required exclusion range for the reserved resources, an MCS, a transmission mode, an RV for relay transmission of the data packet, a reference signal pattern, or some combination of these parameters. The parameters in the request may indicate how the relay UE115 relays the packet such that multiple relay UEs 115 may have similar transmissions (e.g., using the same or similar transmission parameters). The request may additionally reserve resources indicated in the request so that other UEs 115 receiving the request but not acting as relays may refrain from transmitting on these resources to avoid interference to the relay packet.

A UE115 (such as UE 115-d) receiving packets from the source UE 115-a may receive a request from the blocked UE 115-c. In some cases, the UE 115-d may determine whether to act as a relay for the blocked UE 115-c based on one or more parameters. For example, the source UE 115-a may transmit a message to one or more UEs 115 (e.g., UEs 115-b, 115-c, and 115-d) indicating that the UE115 may determine whether to act as a relay for the blocked UE115 (e.g., UE 115-c). The indication (which may be an example of a parameter from which the UE115 may determine whether to act as a relay) may be a bit indicator in a control message that schedules data packets. One value of the bit indicator (e.g., a bit value of one) may enable the UE115 to relay the data packet to another UE115 when the other UE115 loses the data packet. The absence of another bit value (e.g., a bit value of zero) or a bit indicator may cause the UE115 to suppress relaying the data packet even if another UE115 loses the data packet. Additionally or alternatively, the one or more parameters may relate to the UE 115-d relaying packets if the UE 115-d is close enough to the blocked UE 115-c based on the location information of both UEs 115, if the UE 115-d and the UE 115-c have a sufficiently strong link quality (e.g., determined by comparing the current RSRP of the request from the UE 115-c to an RSRP threshold that may be configured or dynamically indicated in the request), or if a combination of these conditions is met. If the UE 115-d determines to act as the relaying UE 115-d (e.g., if this type of relay is enabled at the UE 115-d, the UE 115-d determines that it is close enough to the blocked UE 115-c, is not blocked from the UE 115-c based on a strong enough link quality with the UE 115-c, has indicated resources available for transmission, etc.), the relaying UE 115-d may transmit packets to the blocked UE 115-c on the resources indicated in the request (e.g., via the sidelink 230). In this manner, the wireless communication system 200 can enable on-demand relaying of data packets between UEs to alleviate congestion in the system.

In some cases, the hindering UE 115-b may additionally or alternatively act as a relay UE (e.g., may transmit on reserved resources and have received an appropriate packet if the UE 115-b meets RSRP requirements). In some cases, both UE 115-b and UE 115-d may be potential relay UEs. In these cases, both UE 115-b and UE 115-d may relay data packets to UE 115-c. Since both UEs 115 receive the indicated information in the request from UE 115-c, the UEs 115 may relay data packets using the same transmission parameters. Upon receiving two data packets, the UE 115-c may combine the transmissions and decode the data packets. The complexity of the combined transmission may be reduced based on common transmission parameters used by the relay UEs 115. In some cases, the UE 115-c may set one or more thresholds for relaying packets to limit the number of active relaying UEs 115 in the system.

In some cases, the packet may be relayed using a high MCS (e.g., a higher MCS than the initial packet transmission from the source UE 115-a). Additionally or alternatively, MIMO may be used to reduce resource usage at the blocked UEs 115. In some cases, power control may be implemented by the relay UE 115-d such that the transmit power supports receiving packets at the blocked UE 115-c but does not support reception far beyond the blocked UE 115-c. By implementing power control, interference to other UEs 115 (e.g., other recipient UEs 115 not shown) may be mitigated, which may improve overall network performance.

It should be understood that the processes described with reference to the wireless communication system 200 may be applicable to a V2X system, a D2D system, or any other type of system that supports sidelink communications between devices. Additionally, the described communications may be examples of unicast, broadcast, and/or multicast signaling.

Fig. 3 illustrates an example of a process flow 300 supporting on-demand relaying of messages for side-link communication in accordance with one or more aspects of the present disclosure. Process flow 300 may illustrate an example on-demand relay scheme to provide lost data packets to UE 115. In some examples, the process flow 300 may implement aspects of the wireless communication systems 100 and 200. For example, the UE 115-e may request the blocked data packet from the UE 115-f, where the UE 115-f successfully receives the data packet from the UE 115-g. UEs 115-e, 115-f, and 115-g may be examples of corresponding wireless devices described with reference to fig. 1 and 2. For example, the UEs 115-e, 115-f, and 115-g may be examples of vehicles in a V2X system, wireless devices in a D2D system, or any other type of UE115 that operates using sidelink communications. Alternative examples may be implemented in which some of the operations are performed in a different order than described or not performed at all. In some cases, the operations may include additional features not mentioned below, or further operations may be added.

At 305, a UE 115-g (e.g., a source or transmitting UE 115) may transmit a signal (e.g., in a V2X transmission) that may include a data packet. The transmission may be multicast or unicast, and the data packet may be intended for reception at UE 115-e, UE 115-f, or both. However, the data packet may not be received by UE 115-e. This may be due to interference, blockage, shadowing, or a combination thereof. However, the UE 115-f may successfully receive the data packet from the UE 115-g.

At 310, the UE 115-e (e.g., the blocked or receiving UE 115) may determine that receiving the data packet from the UE 115-g failed. In some cases, a failure to receive a data packet may occur when the remaining delay budget for the packet is low (e.g., below a certain threshold) and the receiving UE 115-e may not be able to wait for the next retransmission from the source UE 115-g. The failure may be determined based on the UE 115-e receiving control information from the UE 115-g indicating resources for transmitting the data packet, but the UE 115-e failing to decode the data packet in the indicated resources. The recipient UE 115-e may also determine whether there is a scheduled future retransmission based on information indicated in the decoded control.

At 315, the UE 115-e may transmit a message to the UE 115-f, the UE 115-g, or other UEs 115 that may have received a data packet from the source UE 115-g indicating a failure to receive the data packet. In some cases, the failure message may be transmitted based on the UE 115-e determining that no future retransmissions of the data packet are scheduled (e.g., there are no one or more scheduled further retransmissions) to transmit according to the control information. The message may be transmitted via unicast signaling to UEs 115 that are known or expected not to be blocked, or via multicast signaling to any surrounding UEs 115 (e.g., within a target range). The failure message may include a resource reservation such that the data packet may be received on the indicated reserved resource. In some cases, the failure message may include a source ID indicating the UE 115-g or a packet ID indicating the data packet, or both. In some cases, the failure message may include one or more exclusion parameters of the reserved resources, such as an exclusion range (e.g., RSRP, distance). In some cases, the failure message may include an MCS index, a transmission mode, an RV, a reference signal mode, an RSRP threshold, or a combination thereof. The UE 115-f may receive the request and determine whether to relay the data packet to the UE 115-e. For example, the UE 115-f may determine whether the UE 115-f is close enough to the UE 115-e based on the location information of the two UEs. Additionally or alternatively, the UE 115-f may determine whether the UE 115-f has a sufficiently strong link quality with the UE 115-e based on the RSRP used to receive the failure message at 315. In some cases, the UE 115-f may determine to relay the data packet to the UE 115-e based on the identified RSRP being greater than the RSRP threshold, the identified distance being less than a distance threshold, the UE 115-f supporting transmission in the indicated resource, or a combination thereof.

At 320, the UE 115-f (e.g., relay UE 115) may relay the data packet to the UE 115-e based on the failure message (e.g., if the UE 115-f satisfies an RSRP threshold, supports transmission in one or more reserved resources indicated by the resource reservation in the failure message, successfully receives the data packet, etc.). The packet may be relayed by the UE 115-f to the UE 115-e on one or more reserved resources. In some cases, UE 115-f may adjust power control parameters for relaying data packets based on RSRP for receiving the failure message. The UE 115-f may select transmission parameters for relaying the data packet based on the parameters (i.e., the request for the packet) indicated in the failure message. In some cases, the UE 115-e may successfully receive the relay data packet from the UE 115-f on one or more reserved resources at 320.

Fig. 4 illustrates a block diagram 400 of an apparatus 405 that supports on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. The device 405 may be an example of aspects of a UE115 as described herein. The device 405 may include a receiver 410, a communication manager 415, and a transmitter 420. The device 405 may also include a processor. Each of these components may be in communication with each other (e.g., via one or more buses).

The receiver 410 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to on-demand relaying of messages for sidelink communications, etc.). The information may be passed to other components of the device 405. The receiver 410 may be an example of aspects of the transceiver 720 described with reference to fig. 7. The receiver 410 may utilize a single antenna or a set of antennas.

The communication manager 415 may be implemented at the first UE. In some cases, the communication manager 415 may determine that the first UE failed to receive the data packet from the second UE (e.g., in a sidelink transmission, such as a V2X or D2D transmission); transmitting a message indicating a failure of the first UE to receive the data packet; and receiving a data packet from a third UE different from the second UE based on the message indicating failure of the first UE to receive the data packet. Additionally or alternatively, the communication manager 415 may receive a data packet from a second UE; receiving a message from a third UE indicating a failure of the third UE to receive the data packet; and relaying the data packet to the third UE based on the message indicating failure of the third UE to receive the data packet. Additionally or alternatively, the communication manager 415 may schedule transmission of the data packet in one or more resources to the second UE and the third UE; transmitting control information to the second UE and the third UE, the control information including a resource reservation indicating the one or more resources and including an indication enabling the second UE to relay the data packet to the third UE in response to a message indicating failure of the third UE to receive the data packet; and transmitting the data packet to the second UE and the third UE in the one or more resources. The communication manager 415 may be an example of aspects of the communication manager 710 described herein.

The actions performed by the communication manager 415 as described herein may be implemented to achieve one or more potential improvements in side-link messaging latency, overhead, or both. For example, relaying a data packet to a UE115 that lost the data packet may improve the latency involved in the UE115 receiving the lost data packet. Further, the relay may allow the UE115 to communicate on the sidelink to avoid potential blocking/shadowing, thereby improving reliability of data packet retransmission. Improved reliability of data packet retransmission (e.g., when the data packet is relayed by the second UE115 rather than retransmitted by the first UE115 to avoid potential impediments) may reduce overhead on sidelink channels.

Based on the first UE115 receiving the lost data packet from the third UE115 (e.g., different from the second UE115 that originally transmitted the data packet), a processor of the first UE115 (e.g., a processor that controls the receiver 410, the communication manager 415, the transmitter 420, etc.) may reduce processing resources used for sidelink communications at the first UE115, the second UE115, the third UE115, or some combination thereof. For example, by receiving the relaying data packet, the first UE115 may reduce the number of times the first UE115 requests retransmission of the data packet. Reducing the number of retransmission requests may reduce the number of times the processor increases processing power and turns on the processing unit to monitor for retransmissions. Additionally or alternatively, the second UE115 may reduce the number of retransmissions performed for the data packet (e.g., because the third UE115 may successfully relay the data packet to avoid potential blocking of the data packet) in order for the first UE115 to successfully receive the data packet. Reducing the number of retransmissions of a data packet may reduce the number of times the processor increases processing power and turns on the processing unit to perform the retransmission.

The communication manager 415 or subcomponents thereof may be implemented in hardware, code executed by a processor (e.g., software or firmware), or any combination thereof. If implemented in code executed by a processor, the functions of the communication manager 415 or its subcomponents may be performed by a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in this disclosure.

The communication manager 415, or subcomponents thereof, may be physically located at various locations, including being distributed such that portions of functionality are implemented by one or more physical components at different physical locations. In some examples, the communication manager 415 or subcomponents thereof may be separate and distinct components in accordance with various aspects of the present disclosure. In some examples, the communication manager 415 or subcomponents thereof may be combined with one or more other hardware components, including but not limited to an input/output (I/O) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof, in accordance with various aspects of the present disclosure.

Transmitter 420 may transmit signals generated by other components of device 405. In some examples, the transmitter 420 may be co-located with the receiver 410 in a transceiver module. For example, the transmitter 420 may be an example of aspects of the transceiver 720 described with reference to fig. 7. The transmitter 420 may utilize a single antenna or a set of antennas.

Fig. 5 illustrates a block diagram 500 of a device 505 that supports on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. The device 505 may be an example of aspects of the device 405 or UE115 as described herein. The device 505 may include a receiver 510, a communication manager 515, and a transmitter 570. The device 505 may also include a processor. Each of these components may be in communication with each other (e.g., via one or more buses).

Receiver 510 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to on-demand relaying of messages for sidelink communications, etc.). Information may be passed to other components of device 505. The receiver 510 may be an example of aspects of the transceiver 720 described with reference to fig. 7. Receiver 510 may utilize a single antenna or a set of antennas.

The communication manager 515 may be an example of aspects of the communication manager 415 as described herein. Communication manager 515 may include a reception failure determination component 520, a failure message transmission component 525, a relaying packet reception component 530, an original packet reception component 535, a failure message reception component 540, a packet relaying component 545, a relay determination component 550, a transmission scheduling component 555, a control information component 560, a data packet component 565, or some combination of these components. The communication manager 515 may be an example of aspects of the communication manager 710 described herein. The communication manager 515 may be implemented by the first UE.

Reception failure determining component 520 may determine that the first UE failed to receive the data packet from the second UE. Failure message transmitting component 525 may transmit a message indicating a failure of the first UE to receive the data packet. The relay packet receiving component 530 may receive a data packet from a third UE different from the second UE based on the message indicating that the first UE failed to receive the data packet. In some cases, the operations performed by the reception failure determination component 520, the relaying packet receiving component 530, or both, may be performed by the receiver 510 or the transceiver 720. Additionally or alternatively, the operations performed by failure message transmission component 525 may be performed by transmitter 570 or transceiver 720.

Original packet receiving component 535 may receive a data packet from a second UE. The failure message receiving component 540 may receive a message from the third UE indicating that the third UE failed to receive the data packet. The packet relay component 545 may relay the data packet to the third UE based on a message indicating that the third UE failed to receive the data packet. In some cases, the operations performed by original packet reception component 535, failure message reception component 540, or both, may be performed by receiver 510 or transceiver 720. Additionally or alternatively, the operations performed by packet relay component 545 may be performed by transmitter 570 or transceiver 720.

Relay determination component 550 may additionally handle conflicts between relaying information, transmitting original information, receiving information, or some combination of these actions (e.g., for certain types of wireless devices, such as half-duplex devices). For example, relay determining component 550 may determine that multiple messages indicate failure to receive different data packets and may determine that resources for relaying different data packets overlap (e.g., overlap in time). The relay determining component 550 may determine which data packet to relay based on a priority value of the data packet or a random selection procedure. Similarly, if the device 505 determines a packet to be relayed on demand, and determines that resources for relaying the packet overlap (e.g., overlap in time) with resources scheduled for receiving a transmission at the device 505 or transmitting an original transmission by the device 505, the relay determining component 550 may determine whether to relay the packet or receive the transmission or transmit the original packet based on one or more collision handling rules. For example, relay determining component 550 may determine how to operate in overlapping resources based on a priority value of a data packet, a priority value for a relay, transmit, and/or receive operation, a random selection procedure, or some combination of these criteria.

Transmission scheduling component 555 can schedule transmission of the data packet to the second UE and the third UE in one or more resources. Control information component 560 may transmit control information to the second UE and the third UE, the control information including a resource reservation indicating one or more resources and an indication enabling the second UE to relay the data packet to the third UE in response to a message indicating failure of the third UE to receive the data packet. Data packet component 565 may transmit a data packet to the second UE and the third UE in the one or more resources. Operations performed by control information component 560, data packet component 565, or both, may be performed by transmitter 570 or transceiver 720.

Transmitter 570 may transmit signals generated by other components of device 505. In some examples, the transmitter 570 may be co-located with the receiver 510 in a transceiver module. For example, the transmitter 570 may be an example of aspects of the transceiver 720 described with reference to fig. 7. Transmitter 570 may utilize a single antenna or a set of antennas.

Fig. 6 illustrates a block diagram 600 of a communication manager 605 that supports on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. The communication manager 605 may be an example of aspects of the communication manager 415, the communication manager 515, or the communication manager 710 described herein. Communication manager 605 may include any combination of reception failure determining component 610, failure message transmitting component 615, relaying packet receiving component 620, information receiving component 625, information decoding component 630, decoding failure component 635, retransmission determining component 640, resource selecting component 645, packet receiving component 650, packet decoding component 655, original packet receiving component 660, failure message receiving component 665, packet relaying component 670, resource determining component 675, relay determining component 680, RSRP determining component 685, parameter adjusting component 690, scheme determining component 694, distance determining component 695, transmission scheduling component 696, control information component 697, data packet component 698, and data packet receiving component 699. Each of these modules may communicate with each other directly or indirectly (e.g., via one or more buses). The communication manager 605 may be used for wireless communication at a first UE (e.g., a UE operating on a sidelink communication link).

Reception failure determining component 610 may determine that the first UE failed to receive the data packet from the second UE. The failure message transmitting component 615 may transmit a message indicating that the first UE failed to receive the data packet. In some cases, the message indicating that the first UE failed to receive the data packet is an example of a NAK message, a request for a data packet, or both. The relay packet receiving component 620 may receive the data packet from a third UE different from the second UE based on the message indicating that the first UE failed to receive the data packet.

In some cases, determining that the first UE failed to receive the data packet from the second UE may include further operations (e.g., performed by information receiving component 625, information decoding component 630, and decoding failure component 635). Information receiving component 625 may receive control information from the second UE. Information decoding component 630 can decode the control information, wherein the decoded control information indicates resources for transmission of the data packet. The decode failure component 635 may not be able to decode the data packet in the indicated resource. Retransmission determining component 640 can determine whether to schedule at least one further retransmission of the data packet by the second UE based on information indicated in the decoded control (e.g., decoded control information). In some examples, retransmission determining component 640 may determine that there are one or more further retransmissions of the data packet scheduled by the second UE, wherein the message indicating failure of the first UE to receive the data packet is transmitted based on the determination that there are no further retransmissions. For example, the retransmission determining component 640 may determine that there are no further retransmissions of the data packet scheduled by the second UE.

In some cases, the decoded control information may indicate a second resource for retransmission of the data packet. In some cases, reception failure determining component 610 may determine that decoding the data packet failed in the indicated second resource for retransmission. In some cases, the failure message transmitting component 615 may transmit a second message indicating a failure to decode the data packet in the indicated second resource for retransmission.

In some cases, failure message transmitting component 615 may determine a cause of failure of the first UE to receive the data packet, where the cause of failure may be interference, a weak signal, or a combination thereof. In some cases, failed transmit component 615 may determine that the signal is weak based on the RSRP value of the transmission (e.g., RSRP that is below a threshold due to blocking/shadowing). Failure message transmitting component 615 may determine whether to transmit a message to the second UE or the third UE, or both, indicating that the first UE failed to receive the data packet based on the reason for the failure. For example, if the failure cause is a low signal energy of transmission (e.g., received signal energy of transmission is below a received signal energy threshold), a message indicating that the first UE failed to receive the data packet may be transmitted to a third UE (e.g., a nearby UE for relaying the data packet). However, if the failure cause is interference, a message indicating that the first UE failed to receive the data packet may be transmitted to the second UE for retransmission of the data packet. For example, reception failure determining component 610 may determine an additional failure of the first UE to receive additional data packets from the second UE. The failure message transmitting component 615 may determine that a cause of an additional failure of the first UE to receive the additional data packet is interference and schedule at least one further retransmission of the additional data packet by the second UE, wherein the at least one further retransmission is dependent on the NAK message. Failure message transmitting component 615 may also transmit a NAK message for the additional data packet to the second UE based on the reason for the additional failure of the first UE to receive the additional data packet being interference. The receiver may receive a retransmission of the additional data packet from the second UE based on the NAK message.

Resource selection component 645 may select one or more resources for resource reservation, wherein the message indicating failure of the first UE to receive the data packet includes the resource reservation, and wherein the data packet is received on the one or more resources indicated by the resource reservation.

In some cases, the message indicating that the first UE failed to receive the data packet may include an RSRP threshold, and receiving the data packet may include packet receiving component 650 receiving the data packet from the third UE based on the RSRP threshold. In some cases, the message indicating that the first UE failed to receive the data packet includes a source ID indicating the second UE or a packet ID indicating the data packet, or both. In some cases, the message indicating that the first UE failed to receive the data packet may include a resource exclusion parameter, such as an exclusion range (e.g., RSRP, distance) of reserved resources. In some cases, the message indicating that the first UE failed to receive the data packet may include an MCS, a transmission mode, an RV, a reference signal mode, or a combination thereof. In some cases, receiving the data packet may include packet receiving component 650 receiving the data packet from the third UE based on the source ID or the packet ID, or both. In some cases, receiving the data packet may include packet receiving component 650 receiving the data packet from the third UE based on the excluded range of reserved resources. In some cases, receiving the data packet may include packet receiving component 650 receiving the data packet from the third UE based on the MCS, the transmission mode, the RV, the reference signal mode, or a combination thereof.

In some examples, packet receiving component 650 may receive the data packet from a fourth UE different from the second UE and the third UE based on a message indicating that the first UE failed to receive the data packet. The packet decoding component 655 may decode the data packet based on combining information corresponding to receiving the data packet from the third UE and information corresponding to receiving the data packet from the fourth UE.

Original packet receiving component 660 may receive a data packet from a second UE. The failure message receiving component 665 can receive a message from the third UE indicating that the third UE failed to receive the data packet. In some cases, the message indicating that the third UE failed to receive the data packet is an example of a NAK message, a request for a data packet, or both. The packet relay component 670 may relay the data packet to the third UE based on a message indicating that the third UE failed to receive the data packet. In some cases, the message indicating that the third UE failed to receive the data packet may include a source ID indicating the second UE or a packet ID indicating the data packet, or both, and relaying the data packet to the third UE may include packet relay component 670 relaying the data packet to the third UE based on the source ID or the packet ID, or both. In some cases, the message indicating that the third UE failed to receive the data packet may include an excluded range of reserved resources, and relaying the data packet to the third UE may include packet relay component 670 relaying the data packet to the third UE based on the excluded range of reserved resources. In some cases, the message indicating the failure of the third UE to receive the data packet may include a transmission mode, RV, reference signal mode, or a combination thereof, and relaying the data packet to the third UE may include packet relay component 670 relaying the data packet to the third UE based on the transmission mode, RV, reference signal mode, or a combination thereof.

In some cases, failure message receiving component 665 can receive a message from the fourth UE indicating that the fourth UE failed to receive the additional data packet, wherein the message includes a resource reservation. Relay determining component 680 may determine to refrain from relaying additional data packets to the fourth UE in the one or more resources indicated by the resource reservation and may refrain from communicating on one or more resources that overlap with the one or more resources indicated by the resource reservation based on the resource reservation.

In some examples, receiving the data packet from the second UE in accordance with the MCS, the spatial multiplexing scheme, the DMRS pattern, or a combination thereof, and relaying the data packet to the third UE involves the packet relay component 670 relaying the data packet to the third UE in accordance with the MCS, the spatial multiplexing scheme, the DMRS pattern, or a combination thereof. In some examples, receiving the data packet from the second UE in accordance with the first MCS, the first spatial multiplexing scheme, the first DMRS pattern, or a combination thereof, and relaying the data packet to the third UE involves the packet relay component 670 relaying the data packet to the third UE in accordance with a second MCS that is different from the first MCS, a second spatial multiplexing scheme that is different from the first spatial multiplexing scheme, a second DMRS pattern that is different from the first DMRS pattern, or a combination thereof. In some cases, the message indicating that the third UE failed to receive the data packet may include an indication of a second MCS, a second spatial multiplexing scheme, a second DMRS pattern, or a combination thereof. Scheme determining component 694 may determine a second MCS, a second spatial multiplexing scheme, a second DMRS pattern, or a combination thereof based on the message indicating that the third UE failed to receive the data packet.

In some cases, the message indicating that the third UE failed to receive the data packet may include a resource reservation. In some of these cases, resource determining component 675 may determine one or more resources indicated by the resource reservation. In some cases, relay determining component 680 may determine to relay the data packet to the third UE based on the first UE supporting transmission on the one or more resources, wherein the data packet is relayed to the third UE on the one or more resources indicated by the resource reservation.

RSRP determining component 685 may determine an RSRP for receiving a message indicating that the third UE failed to receive the data packet. In some cases, relay determining component 680 may determine to relay the data packet to the third UE based on the determined RSRP being greater than the RSRP threshold. In some examples, the message indicating that the third UE failed to receive the data packet includes an RSRP threshold, and RSRP determining component 685 may determine the RSRP threshold based on the message indicating that the third UE failed to receive the data packet. In some cases, parameter adjusting component 690 may adjust a power control parameter for relaying the data packet to the third UE based on the determined RSRP.

The distance determining component 695 may determine a distance between the first UE and the third UE, and the relay determining component 680 determines to relay the data packet to the third UE based on the determined distance being less than a distance threshold.

Transmission scheduling component 696 may schedule transmission of the data packet to the second UE and the third UE in one or more resources. Control information component 697 may transmit control information to the second UE and the third UE, the control information including a resource reservation indicating one or more resources and an indication enabling the second UE to relay the data packet to the third UE in response to a message indicating failure of the third UE to receive the data packet. Data packet component 698 may transmit data packets to the second UE and the third UE in one or more resources. The data packet receiving component 699 may receive the data packet from the second UE based on a message indicating that the third UE failed to receive the data packet.

Fig. 7 illustrates a diagram of a system 700 that includes a device 705 that supports on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. Device 705 may be an example of device 405, device 505, or UE115 or include components of device 705, device 805, or UE115 as described herein. Device 705 may include components for two-way voice and data communications, including components for transmitting and receiving communications, including a communications manager 710, an I/O controller 715, a transceiver 720, an antenna 725, memory 730, and a processor 740. These components may be in electronic communication via one or more buses, such as bus 745.

The apparatus 705 may be an example or a component of a first UE. The communication manager 710 may identify a failure in the transmission for the first UE to receive the data packet from the second UE; transmitting a message indicating a failure of the first UE to receive the data packet; and receiving a data packet from a third UE different from the second UE based on the message indicating failure of the first UE to receive the data packet. Additionally or alternatively, the communication manager 710 may receive a data packet in a transmission from a second UE; receiving a message from a third UE indicating a failure of the third UE to receive the data packet; and relaying the data packet to the third UE based on the message indicating failure of the third UE to receive the data packet. Additionally or alternatively, the communication manager 710 may schedule transmission of the data packet in one or more resources to the second UE and the third UE; transmitting control information to the second UE and the third UE, the control information including a resource reservation indicating one or more resources and including an indication enabling the second UE to relay the data packet to the third UE in response to a message indicating failure of the third UE to receive the data packet; and transmitting the data packet to the second UE and the third UE in the one or more resources.

I/O controller 715 may manage input and output signals for device 705. I/O controller 715 may also manage peripheral devices that are not integrated into device 705. In some cases, I/O controller 715 may represent a physical connection or port to an external peripheral device. In some cases, I/O controller 715 may utilize an operating system, such as Or another known operating system. In other cases, I/O controller 715 may represent or interact with a modem, keyboard, mouse, touch screen, or similar device. In some cases, I/O controller 715 may be implemented as part of a processor. In some cases, a user may interact with the device 715 via the I/O controller 705 or via hardware components controlled by the I/O controller 715.

The transceiver 720 may communicate bi-directionally via one or more antennas, wired or wireless links, as described above. For example, the transceiver 720 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 720 may also include a modem to modulate packets and provide the modulated packets to an antenna for transmission, as well as to demodulate packets received from the antenna.

In some cases, the wireless device may include a single antenna 725. However, in some cases, the device may have more than one antenna 725, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

Memory 730 may include Random Access Memory (RAM) and Read Only Memory (ROM). The memory 730 may store computer-readable, computer-executable code 735 comprising instructions that, when executed, cause the processor to perform various functions described herein. In some cases, memory 730 may include, among other things, a basic I/O system (BIOS) that may control basic hardware or software operations, such as interaction with peripheral components or devices.

Processor 740 may include intelligent hardware devices (e.g., a general purpose processor, a DSP, a Central Processing Unit (CPU), a microcontroller, an ASIC, an FPGA, a programmable logic device, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, processor 740 may be configured to operate the memory array using a memory controller. In other cases, the memory controller may be integrated into processor 740. Processor 740 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 730) to cause apparatus 705 to perform various functions (e.g., functions or tasks to support on-demand relaying of messages for sidelink communications).

Code 735 may include instructions for implementing aspects of the present disclosure, including instructions for supporting wireless communications. Code 735 may be stored in a non-transitory computer-readable medium, such as system memory or other type of memory. In some cases, code 735 may not be directly executable by processor 740, but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

Fig. 8 illustrates a flow diagram of a method 800 of illustrating supporting on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. The operations of method 800 may be implemented by a UE115 (e.g., a vehicle) or a component thereof as described herein. For example, the operations of method 800 may be performed by a communication manager as described with reference to fig. 4-7. In some examples, the UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

At 805, a UE (e.g., a first UE) may determine that the first UE failed to receive a data packet from a second UE. The operations of 805 may be performed according to methods described herein. In some examples, aspects of the operations of 805 may be performed by a reception failure determination component as described with reference to fig. 4-7.

At 810, the UE may transmit a message indicating failure of the first UE to receive the data packet. The operations of 810 may be performed according to methods described herein. In some examples, aspects of the operations of 810 may be performed by a failure message transmission component as described with reference to fig. 4-7.

At 815, the UE may receive a data packet from a third UE different from the second UE based on the message indicating the failure of the first UE to receive the data packet. 815 may be performed according to the methods described herein. In some examples, aspects of the operations of 815 may be performed by a relaying packet receiving component as described with reference to fig. 4-7.

Fig. 9 illustrates a flow diagram of a method 900 of explaining supporting on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. The operations of method 900 may be implemented by a UE115 (e.g., a vehicle) or a component thereof as described herein. For example, the operations of method 900 may be performed by a communication manager as described with reference to fig. 4-7. In some examples, the UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

At 905, a UE (e.g., a first UE) may receive a control message from a second UE. 905 operations may be performed according to methods described herein. In some examples, aspects of the operations of 905 may be performed by an information receiving component as described with reference to fig. 4-7.

At 910, the UE may decode the control information, wherein the decoded control information indicates resources for transmission of the data packet. 910 may be performed according to the methods described herein. In some examples, aspects of the operations of 910 may be performed by an information decoding component as described with reference to fig. 4-7.

At 915, the UE may fail to decode the data packet in the indicated resources. 915 may be performed in accordance with the methods described herein. In some examples, aspects of the operations of 915 may be performed by a decode failure component as described with reference to fig. 4-7.

At 920, the UE may determine that the first UE failed to receive the data packet from the second UE. In some cases, the UE may determine a cause of the failure (e.g., interference or blocking/shadowing), and may determine whether to transmit a message indicating the failure based on the cause. For example, if the UE determines that the UE fails to receive data packets due to congestion/shadowing in the system, the UE may transmit a message requesting to relay the data packets (e.g., to a nearby UE that is different from the second UE). Operations of 920 may be performed according to methods described herein. In some examples, aspects of the operations of 920 may be performed by a reception failure determination component as described with reference to fig. 4-7.

At 925, the UE may transmit a message indicating that the first UE failed to receive the data packet. 925 may be performed according to the methods described herein. In some examples, aspects of the operations of 925 may be performed by a failure message transmission component as described with reference to fig. 4-7.

At 930, the UE may receive a data packet from a third UE different from the second UE based on the message indicating failure of the first UE to receive the data packet. The operations of 930 may be performed according to methods described herein. In some examples, aspects of the operations of 930 may be performed by a relaying packet receiving component as described with reference to fig. 4-7.

Fig. 10 illustrates a flow diagram of a method 1000 of explaining supporting on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. The operations of method 1000 may be implemented by a UE115 (e.g., a vehicle) or a component thereof as described herein. For example, the operations of method 1000 may be performed by a communications manager as described with reference to fig. 4-7. In some examples, the UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

At 1005, a UE (e.g., a first UE) may determine that the first UE failed to receive a data packet from a second UE. The operations of 1005 may be performed in accordance with the methods described herein. In some examples, aspects of the operations of 1005 may be performed by a reception failure determination component as described with reference to fig. 4-7.

At 1010, the UE may determine that there are no one or more further retransmissions of the data packet scheduled by the second UE. In some cases, a message indicating failure of the first UE to receive the data packet may be transmitted based on determining the absence. 1010 may be performed according to the methods described herein. In some examples, aspects of the operations of 1010 may be performed by a retransmission determination component as described with reference to fig. 4-7.

At 1015, the UE may transmit a message indicating that the first UE failed to receive the data packet (e.g., where the message may be transmitted based on determining that no further retransmissions are scheduled). 1015 operations may be performed according to the methods described herein. In some examples, aspects of the operation of 1015 may be performed by a failure message transmission component as described with reference to fig. 4-7.

At 1020, the UE may receive a data packet from a third UE different from the second UE based on the message indicating the failure of the first UE to receive the data packet. 1020 may be performed according to the methods described herein. In some examples, aspects of the operations of 1020 may be performed by a relaying packet receiving component as described with reference to fig. 4-7.

Fig. 11 illustrates a flow diagram of a method 1100 of supporting on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. The operations of method 1100 may be implemented by a UE115 (e.g., a vehicle) or a component thereof as described herein. For example, the operations of method 1100 may be performed by a communications manager as described with reference to fig. 4-7. In some examples, the UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

At 1105, a UE (e.g., a first UE) may receive a data packet from a second UE. 1105 may be performed according to the methods described herein. In some examples, aspects of the operations of 1105 may be performed by an original packet receiving component as described with reference to fig. 4 through 7.

At 1110, the UE may receive a message from a third UE indicating that the third UE failed to receive the data packet. 1110 may be performed according to the methods described herein. In some examples, aspects of the operations of 1110 may be performed by a failure message receiving component as described with reference to fig. 4-7.

At 1115, the UE may relay the data packet to the third UE based on the message indicating that the third UE failed to receive the data packet. 1115 operations may be performed in accordance with the methods described herein. In some examples, aspects of the operation of 1115 may be performed by a packet relay component as described with reference to fig. 4-7.

Fig. 12 illustrates a flow diagram of a method 1200 of explaining supporting on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. The operations of the method 1200 may be implemented by a UE115 (e.g., a vehicle) or a component thereof as described herein. For example, the operations of method 1200 may be performed by a communication manager as described with reference to fig. 4-7. In some examples, the UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

At 1205, a UE (e.g., a first UE) may receive a data packet from a second UE. The operations of 1205 may be performed according to the methods described herein. In some examples, aspects of the operations of 1205 may be performed by the original packet receiving component as described with reference to fig. 4-7.

At 1210, the UE may receive a message from a third UE indicating a failure of the third UE to receive a data packet, wherein the message includes a resource reservation. 1210 may be performed according to the methods described herein. In some examples, aspects of the operations of 1210 may be performed by a failure message receiving component as described with reference to fig. 4-7.

At 1215, the UE may determine one or more resources indicated by the resource reservation. The operations of 1215 may be performed in accordance with the methods described herein. In some examples, aspects of the operations of 1215 may be performed by a resource determination component as described with reference to fig. 4-7.

At 1220, the UE may determine to relay the data packet to a third UE based on the first UE supporting transmission on the one or more resources. In some cases, the data packet is relayed to the third UE on one or more resources indicated by the resource reservation. 1220 may be performed according to the methods described herein. In some examples, aspects of the operations of 1220 may be performed by a relay determination component as described with reference to fig. 4-7.

At 1225, the UE may relay the data packet to the third UE based on the message indicating failure of the third UE to receive the data packet, wherein the data packet is relayed to the third UE on the resources indicated by the resource reservation. 1225 may be performed according to the methods described herein. In some examples, aspects of the operations of 1225 may be performed by a packet relay component as described with reference to fig. 4-7.

Fig. 13 shows a flow diagram illustrating a method 1300 of supporting on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. The operations of method 1300 may be implemented by a UE115 (e.g., a vehicle) or a component thereof as described herein. For example, the operations of method 1300 may be performed by a communication manager as described with reference to fig. 4-7. In some examples, the UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

At 1305, a UE (e.g., a first UE) may receive a data packet from a second UE. 1305 may be performed in accordance with the methods described herein. In some examples, aspects of the operations of 1305 may be performed by an original packet receiving component as described with reference to fig. 4-7.

At 1310, the UE may receive a message from a third UE indicating that the third UE failed to receive the data packet. 1310 may be performed according to the methods described herein. In some examples, aspects of the operations of 1310 may be performed by a failure message receiving component as described with reference to fig. 4-7.

At 1315, the UE may determine an RSRP for receiving a message indicating that a third UE failed to receive the data packet. 1315 may be performed according to the methods described herein. In some examples, aspects of the operations of 1315 may be performed by RSRP determination components as described with reference to fig. 4-7.

At 1320, the UE may determine to relay the data packet to a third UE based on the determined RSRP being greater than the RSRP threshold. 1320 may be performed in accordance with the methods described herein. In some examples, aspects of the operations of 1320 may be performed by a relay determination component as described with reference to fig. 4-7.

At 1325, the UE may relay the data packet to the third UE based on the message indicating that the third UE failed to receive the data packet. 1325 may be performed according to the methods described herein. In some examples, aspects of the operations of 1325 may be performed by a packet relay component as described with reference to fig. 4-7.

Fig. 14 shows a flow diagram illustrating a method 1400 of supporting on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. The operations of the method 1400 may be implemented by a UE115 (e.g., a vehicle) or a component thereof as described herein. For example, the operations of method 1400 may be performed by a communication manager as described with reference to fig. 4-7. In some examples, the UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

At 1405, a UE (e.g., a first UE) may receive a data packet from a second UE. 1405 may be performed according to the methods described herein. In some examples, aspects of the operations of 1405 may be performed by the original packet receiving component as described with reference to fig. 4 through 7.

At 1410, the UE may receive a message from a third UE indicating that the third UE failed to receive the data packet. 1410 may be performed according to the methods described herein. In some examples, aspects of the operations of 1410 may be performed by a failure message receiving component as described with reference to fig. 4-7.

At 1415, the UE may determine a distance between the first UE and the third UE. The operations of 1415 may be performed according to the methods described herein. In some examples, aspects of the operations of 1415 may be performed by a distance determination component as described with reference to fig. 4-7.

At 1420, the UE may determine to relay the data packet to the third UE based on the determined distance being less than the distance threshold. 1420 operations may be performed according to the methods described herein. In some examples, aspects of the operations of 1420 may be performed by a relay determination component as described with reference to fig. 4-7.

At 1425, the UE may relay the data packet to the third UE based on the message indicating that the third UE failed to receive the data packet. 1425 may be performed in accordance with the methods described herein. In some examples, aspects of the operation of 1425 may be performed by a packet relay component as described with reference to fig. 4-7.

Fig. 15 shows a flow diagram illustrating a method 1500 of supporting on-demand relaying of messages for sidelink communications in accordance with one or more aspects of the present disclosure. The operations of method 1500 may be implemented by a UE115 (e.g., a vehicle) or a component thereof as described herein. For example, the operations of method 1500 may be performed by a communication manager as described with reference to fig. 4-7. In some examples, the UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

At 1505, a UE (e.g., a first UE) may schedule transmission of a data packet in one or more resources to a second UE and a third UE. 1505 may be performed in accordance with the methods described herein. In some examples, aspects of the operations of 1505 may be performed by the original packet receiving component as described with reference to fig. 4-7.

At 1510, the UE may transmit control information to the second UE and the third UE, the control information including a resource reservation indicating one or more resources and an indication enabling the second UE to relay the data packet to the third UE in response to the message indicating failure of the third UE to receive the data packet. 1510 may be performed according to the methods described herein. In some examples, aspects of the operations of 1510 may be performed by a failure message receiving component as described with reference to fig. 4-7.

At 1515, the UE may transmit the data packet to the second UE and the third UE in the one or more resources. 1515 the operations may be performed in accordance with the methods described herein. In some examples, aspects of the operations of 1515 may be performed by a distance determination component as described with reference to fig. 4-7.

It should be noted that the methods described herein describe possible implementations, and that the operations and operations may be rearranged or otherwise modified and other implementations are possible. Further, aspects from two or more methods may be combined.

Example 1: a method for wireless communications at a first UE, comprising: determining that the first UE failed to receive the data packet from the second UE; transmitting a message indicating a failure of the first UE to receive the data packet; and receiving a data packet from a third UE different from the second UE based at least in part on the message indicating the failure of the first UE to receive the data packet.

Example 2: the method of example 1, wherein determining that the first UE failed to receive the data packet from the second UE comprises: receiving control information from a second UE; decoding control information, wherein the decoded control information indicates resources for transmission of the data packet; failing to decode the data packet in the indicated resources.

Example 3: the method of example 2, further comprising: determining whether to schedule at least one further retransmission of the data packet by the second UE based at least in part on the decoded control information.

Example 4: the method of any of examples 2 or 3, further comprising: determining that there are one or more further retransmissions of the data packet scheduled by the second UE, wherein the message indicating that the first UE failed to receive the data packet is transmitted based at least in part on the determining that there are no further retransmissions.

Example 5: the method of any of examples 2 to 4, wherein the decoded control information further indicates second resources for retransmission of the data packet, the method further comprising: determining that decoding the data packet failed in the indicated second resource for retransmission; and transmitting a second message indicating a failure to decode the data packet in the indicated second resource for retransmission.

Example 6: the method of any of examples 1 to 5, further comprising: a cause of a failure of the first UE to receive the data packet is determined, wherein the cause of the failure is interference, a transmitted received signal energy being below a received signal energy threshold, or a combination thereof.

Example 7: the method of example 6, further comprising: determining whether to transmit a message to the second UE or the third UE or both indicating a failure of the first UE to receive the data packet based at least in part on the reason for the failure.

Example 8: the method of any of examples 6 or 7, further comprising: determining an attachment failure of the first UE to receive the additional data packet from the second UE; determining that a cause of an additional failure of the first UE to receive the additional data packet is interference; determining at least one further retransmission of the additional data packet is scheduled by the second UE, wherein the at least one further retransmission is dependent on the NAK message; transmitting a NAK message for the additional data packet to the second UE based at least in part on the cause of the additional failure of the first UE to receive the additional data packet being interference; and receiving a retransmission of the additional data packet from the second UE based at least in part on the NAK message.

Example 9: the method of any one of examples 6 to 8, wherein: the reason for the failure is that the transmitted received signal energy is below the received signal energy threshold; and a message indicating failure of the first UE to receive the data packet is transmitted to the third UE.

Example 10: the method of any of examples 1 to 9, further comprising: selecting one or more resources for resource reservation, wherein the message indicating failure of the first UE to receive the data packet comprises the resource reservation, and wherein the data packet is received on the one or more resources indicated by the resource reservation.

Example 11: the method of any of examples 1 to 10, wherein the message indicating that the first UE failed to receive the data packet comprises a source ID indicating the second UE or a packet ID indicating the data packet, or both.

Example 12: the method of example 11, wherein receiving the data packet comprises: receiving a data packet from the third UE based at least in part on the source ID or the packet ID or both.

Example 13: the method of any of examples 1 to 12, wherein the message indicating that the first UE failed to receive the data packet comprises an exclusion range of reserved resources, an MCS, a transmission mode, an RV, a reference signal pattern, or a combination thereof, and wherein receiving the data packet comprises: receiving a data packet from a third UE based at least in part on an exclusion range of reserved resources, an MCS, a transmission mode, an RV, a reference signal mode, or a combination thereof.

Example 14: the method of any of examples 1 to 13, further comprising: receiving a data packet from a fourth UE different from the second UE and the third UE based at least in part on a message indicating failure of the first UE to receive the data packet; and decode the data packet based at least in part on combining information corresponding to receiving the data packet from the third UE with information corresponding to receiving the data packet from the fourth UE.

Example 15: the method of any of examples 1 to 14, wherein the message indicating that the first UE failed to receive the data packet comprises a NAK message or a request for a data packet, or both.

Example 16: an apparatus, comprising: at least one apparatus for performing a method as in any one of examples 1-15.

Example 17: an apparatus for wireless communication, comprising a processor; and a memory coupled to the processor, the processor and memory configured to perform the method of any of examples 1-15.

Example 18: a non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to perform a method as in any one of examples 1 to 15.

Example 19: a method for wireless communications at a first UE, comprising: receiving a data packet from a second UE; receiving a message from a third UE indicating a failure of the third UE to receive the data packet; and relaying the data packet to the third UE based at least in part on the message indicating failure of the third UE to receive the data packet.

Example 20: the method of example 19, wherein the message indicating failure of the third UE to receive the data packet includes a resource reservation, the method further comprising: determining one or more resources indicated by the resource reservation; and determine to relay the data packet to the third UE based at least in part on the first UE supporting transmission on the one or more resources, wherein the data packet is relayed to the third UE on the one or more resources indicated by the resource reservation.

Example 21: the method of any one of examples 19 or 20, further comprising: determining RSRP for receiving a message indicating failure of the third UE to receive the data packet; determining to relay the data packet to the third UE based at least in part on the determined RSRP being greater than the RSRP threshold.

Example 22: the method of example 21, wherein the message indicating failure of the third UE to receive the data packet comprises an RSRP threshold, the method further comprising: the RSRP threshold is determined based at least in part on a message indicating a failure of a third UE to receive the data packet.

Example 23: the method of any one of examples 21 or 22, further comprising: adjusting a power control parameter for relaying the data packet to the third UE based at least in part on the determined RSRP.

Example 24: the method of any of examples 19 to 23, further comprising: receiving a message from a fourth UE indicating that the fourth UE failed to receive the additional data packet, wherein the message indicating that the fourth UE failed to receive the additional data packet includes a resource reservation; determining to refrain from relaying the additional data packet to the fourth UE in the one or more resources indicated by the resource reservation; and refrain from communicating on one or more resources that overlap with one or more resources indicated by the resource reservation based at least in part on the resource reservation.

Example 25: the method of any of examples 19 to 24, wherein the data packet is received from the second UE according to the MCS, the spatial multiplexing scheme, and the DMRS pattern, and wherein relaying the data packet to the third UE comprises: relaying the data packet to the third UE according to the MCS, the spatial multiplexing scheme, the DMRS pattern, or a combination thereof.

Example 26: the method of any of examples 19 to 25, wherein the data packet is received from the second UE according to the first MCS, the first spatial multiplexing scheme, and the first DMRS pattern, and wherein relaying the data packet to the third UE comprises: relaying the data packet to a third UE according to a second MCS that is different from the first MCS, a second spatial multiplexing scheme that is different from the first spatial multiplexing scheme, a second DMRS pattern that is different from the first DMRS pattern, or a combination thereof.

Example 27: the method of example 26, wherein the message indicating that the third UE failed to receive the data packet includes an indication of a second MCS, a second spatial multiplexing scheme, a second DMRS pattern, or a combination thereof, the method further comprising: determining a second MCS, a second spatial multiplexing scheme, a second DMRS pattern, or a combination thereof based at least in part on the message indicating the failure of the third UE to receive the data packet.

Example 28: the method of any of examples 19 to 27, further comprising: determining a distance between the first UE and the third UE; and determine to relay the data packet to the third UE based at least in part on the determined distance being less than the distance threshold.

Example 29: the method of any of examples 19 to 28, wherein the message indicating that the third UE failed to receive the data packet comprises a source ID indicating the second UE, a packet ID indicating the data packet, an exclusion range of reserved resources, a transmission mode, a RV, a reference signal pattern, or a combination thereof, and wherein relaying the data packet to the third UE comprises: relaying the data packet to the third UE based at least in part on the source ID, the packet ID, an exclusion range of reserved resources, a transmission mode, the RV, a reference signal pattern, or a combination thereof.

Example 30: the method of any of examples 19 to 29, wherein the message indicating that the third UE failed to receive the data packet comprises a NAK message or a request for a data packet, or both.

Example 31: an apparatus, comprising: at least one apparatus for performing the method of any of examples 19-30.

Example 32: an apparatus for wireless communication, comprising a processor; and a memory coupled to the processor, the processor and memory configured to perform the method of any of examples 19 to 30.

Example 33: a non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to perform a method as in any one of examples 19 to 30.

Example 34: a method for wireless communications at a first UE, comprising: scheduling transmission of the data packet in one or more resources to the second UE and the third UE; transmitting control information to the second UE and the third UE, the control information including a resource reservation indicating one or more resources and including an indication enabling the second UE to relay the data packet to the third UE in response to a message indicating failure of the third UE to receive the data packet; and transmitting the data packet to the second UE and the third UE in the one or more resources.

Example 35: the method of example 34, further comprising: receiving a data packet from the second UE based at least in part on the message indicating failure of the third UE to receive the data packet.

Example 36: an apparatus, comprising: at least one apparatus for performing a method as in any of examples 34 or 35.

Example 37: an apparatus for wireless communication, comprising a processor; and a memory coupled to the processor, the processor and the memory configured to perform the method of any of examples 34 or 35.

Example 38: a non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to perform a method as in any of examples 34 or 35.

The techniques described herein may be used for various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA, Single-Carrier frequency division multiple Access (SC-FDMA), and other systems. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95 and IS-856 standards. The IS-2000 version may be generally referred to as CDMA 20001X, 1X, etc. IS-856(TIA-856) IS commonly referred to as CDMA 20001 xEV-DO, High Rate Packet Data (HRPD), etc. UTRA includes wideband CDMA (wcdma) and other variants of CDMA. TDMA systems may implement radio technologies such as global system for mobile communications (GSM).

The OFDMA system may implement radio technologies such as Ultra Mobile Broadband (UMB), evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers (IEEE)802.11(Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). LTE, LTE-A and LTE-A Pro are versions of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE-A, LTE-A Pro, NR, and GSM are described in literature from an organization named "third Generation partnership project" (3 GPP). CDMA2000 and UMB are described in documents from an organization named "third generation partnership project 2" (3GPP 2). The techniques described herein may be used for both the systems and radio technologies mentioned herein and for other systems and radio technologies. Although aspects of the LTE, LTE-A, LTE-A Pro or NR system may be described for exemplary purposes and LTE, LTE-A, LTE-A Pro or NR terminology may be used in much of the description, the techniques described herein may also be applied to applications other than LTE, LTE-A, LTE-A Pro or NR applications.

A macro cell may cover a relatively large geographic area (e.g., an area with a radius of several kilometers) and may allow unrestricted access by UEs with service subscriptions with the network provider. A small cell may be associated with a lower power base station (as compared to a macro cell), and the small cell may operate in the same or a different (e.g., licensed, unlicensed, etc.) frequency band than the macro cell. According to various examples, a small cell may include a picocell, a femtocell, and a microcell. A picocell, for example, may cover a small geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A femtocell may also cover a smaller geographic area (e.g., a residence) and may provide restricted access by UEs associated with the femtocell (e.g., UEs in a Closed Subscriber Group (CSG), UEs of users in the residence, etc.). The eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, pico eNB, femto eNB, or home eNB. An eNB may support one or more (e.g., two, three, four, etc.) cells and may also support communication using one or more component carriers. The gbb for a macro cell may be referred to as a macro gbb. A gNB for a small cell may be referred to as a small cell gNB, pico gNB, femto gNB, or home gNB. The gNB may support one or more (e.g., two, three, four, etc.) cells (e.g., component carriers).

The wireless communication systems described herein may support synchronous or asynchronous operation. For synchronous operation, each base station may have similar frame timing, and transmissions from different base stations may be approximately aligned in time. For asynchronous operation, each base station may have different frame timing, and transmissions from different base stations may not be aligned in time. The techniques described herein may be used for synchronous or asynchronous operations.

Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general purpose processor, a DSP, an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and the following claims. For example, due to the nature of software, the functions described herein may be implemented using software executed by a processor, hardware, firmware, hard-wired, or any combination thereof. Features that implement functions may also be physically located at various locations, including being distributed such that portions of functions are implemented at different physical locations.

Computer-readable media includes both non-transitory computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another. Non-transitory storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media can comprise RAM, ROM, electrically erasable programmable ROM (eeprom), flash memory, Compact Disc (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk (disk) and disc (disc), as used herein, includes CD, laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

As used herein, including in the claims, "or" as used in a list of items (e.g., a list of items accompanied by a phrase such as "at least one of" or "one or more of") indicates an inclusive list, such that, for example, a list of at least one of A, B or C means a or B or C or AB or AC or BC or ABC (i.e., a and B and C). Also, as used herein, the phrase "based on" should not be read as referring to a closed condition set. For example, an exemplary operation described as "based on condition a" may be based on both condition a and condition B without departing from the scope of the present disclosure. In other words, the phrase "based on," as used herein, should be interpreted in the same manner as the phrase "based, at least in part, on.

In the drawings, similar components or features may have the same reference numerals. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description may apply to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label.

The illustrations set forth herein in connection with the figures describe example configurations and are not intended to represent all examples that may be implemented or fall within the scope of the claims. The term "exemplary" as used herein means "serving as an example, instance, or illustration," and does not mean "preferred" or "advantageous over other examples. The detailed description includes specific details to provide an understanding of the described technology. However, the techniques may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

The description herein is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.