阅读说明：本技术 确定用于传输的rach前置码消息的数目 (Determining the number of RACH preamble messages for transmission ) 是由 M·N·伊斯兰 B·萨迪格 N·阿贝迪尼 于 2018-12-14 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。在一些系统中,基站和用户装备(UE)可使用波束成形来传送随机接入信道(RACH)消息。UE可(例如,在随机接入响应(RAR)窗口内)传送多个RACH前置码消息以发起RACH规程。UE可在与从基站接收到的参考信号相对应的传输机会中传送RACH前置码消息。在一些情形中,UE可基于该UE同时监视响应于每个所传送的消息的RAR消息的能力来确定要在RAR窗口内传送的RACH前置码消息的数目。在其他情形中,UE可向基站传送对UE能力的指示。基站可基于这些能力来确定用于UE的RACH资源配置,并且可向该UE指示该配置。(Methods, systems, and devices for wireless communication are described. In some systems, a base station and User Equipment (UE) may transmit a Random Access Channel (RACH) message using beamforming. The UE may transmit multiple RACH preamble messages (e.g., within a Random Access Response (RAR) window) to initiate a RACH procedure. The UE may transmit a RACH preamble message in a transmission opportunity corresponding to a reference signal received from the base station. In some cases, the UE may determine the number of RACH preamble messages to transmit within a RAR window based on the UE's ability to simultaneously monitor RAR messages in response to each transmitted message. In other cases, the UE may transmit an indication of the UE capabilities to the base station. The base station may determine a RACH resource configuration for the UE based on the capabilities and may indicate the configuration to the UE.)

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

receiving a plurality of reference signals, wherein each reference signal of the plurality of reference signals corresponds to at least one transmission opportunity for Random Access Channel (RACH) preamble message transmission;

determining a number of RACH preamble messages to transmit in response to the received plurality of reference signals, wherein the determination is based at least in part on a capability of the UE to simultaneously monitor Random Access Response (RAR) messages corresponding to the number of RACH preamble messages; and

transmitting the determined number of RACH preamble messages based at least in part on the determining, wherein each RACH preamble message of the number of RACH preamble messages corresponds to a reference signal of the received plurality of reference signals.

2. The method of claim 1, wherein transmitting the determined number of RACH preamble messages further comprises:

transmitting the determined number of RACH preamble messages in the RAR window.

3. The method of claim 2, wherein transmitting the determined number of RACH preamble messages in the RAR window comprises:

transmitting at least one of the determined number of RACH preamble messages prior to expiration of the RAR window, wherein the RAR window corresponds to a previously transmitted RACH preamble message.

4. The method of claim 2, wherein transmitting the determined number of RACH preamble messages comprises:

transmitting, within the RAR window, a plurality of RACH preamble messages corresponding to a same reference signal of the plurality of reference signals based at least in part on the same reference signal corresponding to a plurality of transmission opportunities for RACH preamble message transmission.

5. The method of claim 2, wherein the RAR window corresponds to a first RACH preamble message of the number of RACH preamble messages.

6. The method of claim 1, further comprising:

monitoring a plurality of RAR messages, wherein each RAR message of the plurality of RAR messages is responsive to an associated RACH preamble message of the number of RACH preamble messages.

7. The method of claim 6, wherein each of the plurality of reference signals is received on a particular receive beam, and wherein monitoring the plurality of RAR messages comprises:

monitoring each RAR message on the particular receive beam for the reference signal corresponding to the associated RACH preamble message.

8. The method of claim 6, further comprising:

receiving one or more RAR messages in response to one or more of the number of RACH preamble messages.

9. The method of claim 8, further comprising:

stopping the monitoring based at least in part on receiving a first RAR message in response to one or more of the number of RACH preamble messages.

10. The method of claim 8, further comprising:

selecting one RAR message from a plurality of received RAR messages based at least in part on a reception order of the plurality of received RAR messages, an indicated RACH message 3(Msg3) transmission power for the plurality of received RAR messages, an estimated reception power for the plurality of received RAR messages, a pseudo-random selection procedure, or a combination thereof; and

transmitting a single RACH Msg3 in response to the plurality of received RAR messages based at least in part on the selecting.

11. The method of claim 8, further comprising:

transmitting a plurality of RACH message 3(Msg3) transmissions in response to the plurality of received RAR messages.

12. The method of claim 1, wherein the capability of the UE to simultaneously monitor RAR messages corresponding to the number of RACH preamble messages is based at least in part on a number of sub-arrays, a number of receive panels, a number of UE diversity branches, a number of reference signals received on each receive beam, or a combination thereof.

13. The method of claim 1, wherein determining the number of RACH preamble messages to transmit is further based at least in part on whether each of the plurality of reference signals is received with a reference signal received power that is greater than a reference signal received power threshold.

14. The method of claim 13, wherein each of the plurality of reference signals is received simultaneously with a reference signal received power that is greater than the reference signal received power threshold.

15. The method of claim 13, wherein each of the plurality of reference signals is received with a same beam at a reference signal received power that is greater than the reference signal received power threshold.

16. The method of claim 13, further comprising:

determining the reference signal received power threshold based at least in part on a network configuration.

17. The method of claim 1, wherein the plurality of reference signals comprise synchronization signal blocks, channel state information reference signals (CSI-RS), or a combination thereof.

18. The method of claim 1, wherein at least one of the number of RACH preamble messages corresponds to a contention-free RACH procedure.

19. The method of claim 18, further comprising:

a single RAR message is received in response to multiple RACH preamble messages.

20. The method of claim 1, wherein at least one of the number of RACH preamble messages corresponds to a contention-based RACH procedure.

21. The method of claim 20, wherein determining the number of RACH preamble messages to transmit is further based at least in part on a maximum number of RACH preamble messages to transmit within a RAR window.

22. A method for wireless communications at a base station, comprising:

transmitting a plurality of reference signals, wherein each reference signal of the plurality of reference signals corresponds to at least one transmission opportunity for Random Access Channel (RACH) preamble message transmission;

receiving a number of RACH preamble messages from a User Equipment (UE) based at least in part on the UE's ability to simultaneously monitor Random Access Response (RAR) messages in response to the number of RACH preamble messages, wherein each RACH preamble message of the number of RACH preamble messages corresponds to a reference signal of the plurality of reference signals; and

transmitting at least one RAR message in response to the number of RACH preamble messages.

23. The method of claim 22, wherein receiving the number of RACH preamble messages from the UE further comprises:

receiving the number of RACH preamble messages from the UE in a RAR window.

24. The method of claim 23, wherein receiving the number of RACH preamble messages from the UE in the RAR window comprises:

receiving at least one of the number of RACH preamble messages prior to expiration of the RAR window, wherein the RAR window corresponds to a previously received RACH preamble message.

25. The method of claim 23, wherein the at least one RAR message is transmitted within the RAR window.

26. The method of claim 22, wherein transmitting the at least one RAR message comprises:

transmitting a single RAR message in response to the number of RACH preamble messages.

27. The method of claim 22, wherein transmitting the at least one RAR message comprises:

transmitting a RAR message in response to each received RACH preamble message of the number of RACH preamble messages.

28. The method of claim 22, further comprising:

receiving one or more RACH message 3(Msg3) transmissions in response to the at least one RAR message.

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

transmitting an indication of one or more capabilities of the UE;

receiving an indication of resources configured for a plurality of Random Access Channel (RACH) preamble message transmissions based at least in part on one or more capabilities of the UE; and

a number of RACH preamble messages are transmitted according to the configured resources.

30. The method of claim 22, wherein receiving the indication of the configured resources further comprises:

receiving the indication of resources configured for multiple RACH preamble message transmissions within a Random Access Response (RAR) window.

31. The method of claim 29, wherein the one or more capabilities comprise a maximum number of reference signals that the UE can detect from one or more base stations simultaneously.

32. The method of claim 31, wherein the UE can simultaneously detect the maximum number of reference signals at a reference signal received power that is greater than a reference signal received power threshold.

33. The method of claim 31, wherein the reference signal comprises a synchronization signal block, a channel state information reference signal (CSI-RS), or a combination thereof.

34. The method of claim 29, wherein the one or more capabilities comprise a number of sub-arrays, a number of receive panels, a number of UE diversity branches, a number of receive beams, a number of transmit beams, or a combination thereof.

35. The method of claim 29, wherein the one or more capabilities comprise a level of beam correspondence for the UE.

36. The method of claim 35, further comprising:

receiving a plurality of reference signals, wherein a number of transmission opportunities for RACH preamble message transmission for each of the plurality of reference signals is based at least in part on a number of transmit beams for each receive beam used by the UE.

37. The method of claim 29, wherein the indication of the configured resources comprises a handover message, Radio Resource Control (RRC) signaling, a Medium Access Control (MAC) Control Element (CE), Downlink Control Information (DCI), a Master Information Block (MIB), remaining system information (RMSI), Other System Information (OSI), or a combination thereof.

38. The method of claim 29, wherein the configured resources correspond to a contention-free RACH procedure.

39. A method for wireless communications at a base station, comprising:

receiving an indication of one or more capabilities of a User Equipment (UE);

configuring resources for a plurality of Random Access Channel (RACH) preamble message transmissions based at least in part on one or more capabilities of the UE; and

transmitting an indication of the configured resources to the UE.

40. The method of claim 39, wherein configuring the resources for a plurality of RACH preamble message transmissions further comprises:

the resources are configured for a plurality of RACH preamble message transmissions within a Random Access Response (RAR) window.

41. The method of claim 39, wherein the one or more capabilities comprise a maximum number of reference signals that the UE can detect from one or more base stations within a time window.

42. The method of claim 41, wherein the maximum number of reference signals is based at least in part on a reference signal received power threshold.

43. The method of claim 41, wherein the reference signal comprises a synchronization signal block, a channel state information reference signal (CSI-RS), or a combination thereof.

44. The method of claim 39, wherein the one or more capabilities comprise a number of sub-arrays, a number of receive panels, a number of UE diversity branches, a number of receive beams, a number of transmit beams, or a combination thereof.

45. The method of claim 39, wherein the one or more capabilities comprise a level of beam correspondence for the UE.

46. The method of claim 45, further comprising:

transmitting a plurality of reference signals, wherein a number of transmission opportunities for RACH preamble message transmission for each of the plurality of reference signals is based at least in part on a number of transmit beams for each receive beam used by the UE.

47. The method of claim 39, wherein the indication of the configured resources comprises a handover message, Radio Resource Control (RRC) signaling, a Media Access Control (MAC) Control Element (CE), Downlink Control Information (DCI), a Master Information Block (MIB), remaining System information (RMSI), Other System Information (OSI), or a combination thereof.

48. The method of claim 39, further comprising:

receiving a number of RACH preamble messages according to the configured resources.

49. The method of claim 39, wherein the configured resources correspond to a contention-free RACH procedure.

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

means for receiving a plurality of reference signals, wherein each reference signal of the plurality of reference signals corresponds to at least one transmission opportunity for Random Access Channel (RACH) preamble message transmission;

means for determining a number of RACH preamble messages to transmit in response to the received plurality of reference signals, wherein the determination is based at least in part on a capability of the UE to simultaneously monitor Random Access Response (RAR) messages corresponding to the number of RACH preamble messages; and

means for transmitting a determined number of RACH preamble messages based at least in part on the determining, wherein each RACH preamble message of the number of RACH preamble messages corresponds to a reference signal of a received plurality of reference signals.

51. The apparatus of claim 50, wherein means for transmitting the determined number of RACH preamble messages further comprises:

means for transmitting the determined number of RACH preamble messages in the RAR window.

52. The apparatus of claim 51, wherein the means for transmitting the number of RACH preamble messages in the RAR window further comprises:

means for transmitting at least one of the determined number of RACH preamble messages prior to expiration of the RAR window, wherein the RAR window corresponds to a previously transmitted RACH preamble message.

53. The apparatus of claim 51, wherein means for transmitting the number of RACH preamble messages further comprises:

means for transmitting a plurality of RACH preamble messages corresponding to a same reference signal of the plurality of reference signals within the RAR window based at least in part on the same reference signal corresponding to a plurality of transmission opportunities for RACH preamble message transmission.

54. The apparatus of claim 51, wherein the RAR window corresponds to a first RACH preamble message of the number of RACH preamble messages.

55. The apparatus of claim 50, further comprising:

means for monitoring for a plurality of RAR messages, wherein each RAR message of the plurality of RAR messages is responsive to an associated RACH preamble message of the number of RACH preamble messages.

56. The apparatus of claim 55, wherein each of the plurality of reference signals is received on a particular receive beam, and wherein the means for monitoring the plurality of RAR messages further comprises:

means for monitoring each RAR message on the particular receive beam for the reference signal corresponding to the associated RACH preamble message.

57. The apparatus of claim 55, further comprising:

means for receiving one or more RAR messages in response to one or more of the number of RACH preamble messages.

58. The apparatus of claim 57, further comprising:

means for stopping the monitoring based at least in part on receiving a first RAR message in response to one or more of the number of RACH preamble messages.

59. The apparatus of claim 57, further comprising:

means for selecting one RAR message from a plurality of received RAR messages based at least in part on an order of receipt of the plurality of received RAR messages, an indicated RACH message 3(Msg3) transmission power for the plurality of received RAR messages, an estimated received power for the plurality of received RAR messages, a pseudo-random selection procedure, or a combination thereof; and

means for transmitting a single RACHMsg3 in response to the plurality of received RAR messages based at least in part on the selecting.

60. The apparatus of claim 57, further comprising:

means for transmitting a plurality of RACH message 3(Msg3) transmissions in response to a plurality of received RAR messages.

61. The apparatus of claim 50, wherein the capability of the UE to simultaneously monitor RAR messages corresponding to the number of RACH preamble messages is based at least in part on a number of sub-arrays, a number of receive panels, a number of UE diversity branches, a number of reference signals received on each receive beam, or a combination thereof.

62. The apparatus of claim 50, wherein determining the number of RACH preamble messages to transmit is further based at least in part on whether each of the plurality of reference signals is received with a reference signal received power that is greater than a reference signal received power threshold.

63. The apparatus of claim 62, wherein each of the plurality of reference signals is received simultaneously with a reference signal received power that is greater than the reference signal received power threshold.

64. The apparatus of claim 62, wherein each of the plurality of reference signals is received with a same beam at a reference signal received power greater than the reference signal received power threshold.

65. The apparatus as claimed in claim 62, further comprising:

means for determining the reference signal received power threshold based at least in part on a network configuration.

66. The apparatus of claim 50, wherein the plurality of reference signals comprise synchronization signal blocks, channel state information reference signals (CSI-RSs), or a combination thereof.

67. The apparatus of claim 50, wherein at least one of the number of RACH preamble messages corresponds to a contention-free RACH procedure.

68. The apparatus as recited in claim 67, further comprising:

means for receiving a single RAR message in response to multiple RACH preamble messages.

69. The apparatus of claim 50, wherein at least one of the number of RACH preamble messages corresponds to a contention-based RACH procedure.

70. The apparatus of claim 69, wherein determining the number of RACH preamble messages to transmit is further based at least in part on a maximum number of RACH preamble messages to transmit within a RAR window.

71. An apparatus for wireless communication at a base station, comprising:

means for transmitting a plurality of reference signals, wherein each reference signal of the plurality of reference signals corresponds to at least one transmission opportunity for Random Access Channel (RACH) preamble message transmission;

means for receiving a number of Random Access Response (RAR) messages from a User Equipment (UE) based at least in part on the UE's ability to simultaneously monitor for the number of RACH preamble messages, wherein each RACH preamble message of the number of RACH preamble messages corresponds to a reference signal of the plurality of reference signals; and

means for transmitting at least one RAR message in response to the number of RACH preamble messages.

72. The apparatus of claim 71, further comprising:

means for receiving the number of RACH preamble messages from the UE in a RAR window.

73. The apparatus of claim 72, further comprising:

means for receiving at least one RACH preamble message of the number of RACH preamble messages prior to expiration of the RAR window, wherein the RAR window corresponds to a previously received RACH preamble message.

74. The apparatus of claim 72, wherein the at least one RAR message is transmitted within the RAR window.

75. The apparatus of claim 71, wherein the means for transmitting the at least one RAR message further comprises:

means for transmitting a single RAR message in response to the number of RACH preamble messages.

76. The apparatus of claim 71, wherein the means for transmitting the at least one RAR message further comprises:

means for transmitting a RAR message in response to each received RACH preamble message of the number of RACH preamble messages.

77. The apparatus of claim 71, further comprising:

means for receiving one or more RACH message 3(Msg3) transmissions in response to the at least one RAR message.

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

means for transmitting an indication of one or more capabilities of the UE;

means for receiving an indication of resources configured for a plurality of Random Access Channel (RACH) preamble message transmissions based at least in part on one or more capabilities of the UE; and

means for transmitting a number of RACH preamble messages according to the configured resources.

79. The apparatus of claim 84, wherein means for receiving an indication of resources configured for a plurality of RACH preamble message transmissions further comprises:

means for receiving the indication of resources configured for multiple RACH preamble message transmissions within a Random Access Response (RAR) window.

80. The apparatus of claim 78, wherein the one or more capabilities comprise a maximum number of reference signals that the UE can detect from one or more base stations simultaneously.

81. The apparatus of claim 80, wherein the UE can simultaneously detect the maximum number of reference signals at a reference signal received power that is greater than a reference signal received power threshold.

82. The apparatus of claim 80, wherein the reference signal comprises a synchronization signal block, a channel state information reference signal (CSI-RS), or a combination thereof.

83. The apparatus of claim 78, wherein the one or more capabilities comprise a number of sub-arrays, a number of receive panels, a number of UE diversity branches, a number of receive beams, a number of transmit beams, or a combination thereof.

84. The apparatus of claim 78, wherein the one or more capabilities comprise a level of beam correspondence for the UE.

85. The apparatus as claimed in claim 84, further comprising:

means for receiving a plurality of reference signals, wherein a number of transmission opportunities for RACH preamble message transmission for each reference signal of the plurality of reference signals is based at least in part on a number of transmit beams for each receive beam used by the UE.

86. The apparatus of claim 78, wherein the indication of the configured resources comprises a handover message, Radio Resource Control (RRC) signaling, a Media Access Control (MAC) Control Element (CE), Downlink Control Information (DCI), a Master Information Block (MIB), remaining system information (RMSI), Other System Information (OSI), or a combination thereof.

87. The apparatus of claim 78, wherein the configured resources correspond to a contention-free RACH procedure.

88. An apparatus for wireless communication at a base station, comprising:

means for receiving an indication of one or more capabilities of a User Equipment (UE);

means for configuring resources for a plurality of Random Access Channel (RACH) preamble message transmissions based at least in part on one or more capabilities of the UE; and

means for transmitting an indication of the configured resources to the UE.

89. The apparatus of claim 88, wherein means for configuring the resources for a plurality of RACH preamble message transmissions further comprises:

means for configuring the resources for a plurality of RACH preamble message transmissions within a Random Access Response (RAR) window.

90. The apparatus of claim 88, wherein the one or more capabilities comprise a maximum number of reference signals the UE can detect from one or more base stations within a time window.

91. The apparatus of claim 90, wherein the maximum number of reference signals is based at least in part on a reference signal received power threshold.

92. The apparatus of claim 90, wherein the reference signal comprises a synchronization signal block, a channel state information reference signal (CSI-RS), or a combination thereof.

93. The apparatus of claim 88, wherein the one or more capabilities comprise a number of sub-arrays, a number of receive panels, a number of UE diversity branches, a number of receive beams, a number of transmit beams, or a combination thereof.

94. The apparatus of claim 88, wherein the one or more capabilities comprise a level of beam correspondence for the UE.

95. The apparatus as claimed in claim 94, further comprising:

means for transmitting a plurality of reference signals, wherein a number of transmission opportunities for RACH preamble message transmission for each reference signal of the plurality of reference signals is based at least in part on a number of transmit beams for each receive beam used by the UE.

96. The apparatus of claim 88, wherein the indication of the configured resources comprises a handover message, Radio Resource Control (RRC) signaling, a Medium Access Control (MAC) Control Element (CE), Downlink Control Information (DCI), a Master Information Block (MIB), remaining system information (RMSI), Other System Information (OSI), or a combination thereof.

97. The apparatus as claimed in claim 88 and further comprising:

means for receiving a number of RACH preamble messages according to the configured resources.

98. The apparatus of claim 88, wherein the configured resources correspond to a contention-free RACH procedure.

Background

The following relates generally to wireless communications, and more particularly to determining a number of Random Access Channel (RACH) preamble messages for transmission.

Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be able to support communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth generation (4G) systems, such as Long Term Evolution (LTE) systems, LTE-advanced (LTE-a) systems, or LTE-a Pro systems, and fifth generation (5G) systems that may be referred to as New Radio (NR) systems. These systems may employ various techniques, such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), or discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM). A wireless multiple-access communication system may include several base stations or network access nodes, each supporting communication for multiple communication devices simultaneously, which may otherwise be referred to as User Equipment (UE).

Wireless communication between two wireless nodes (e.g., between a base station and a UE) may use beams or beamformed signals for transmission and/or reception. The base station may transmit a beamformed synchronization signal on a downlink synchronization beam. The UE may receive synchronization signals on one or more of the downlink synchronization beams and thus be able to initiate a RACH procedure with the base station. In some cases, the UE may send a message to the base station as part of a RACH procedure. The UE may send messages using an uplink transmit beam and the base station may receive transmissions using an uplink receive beam. However, in some examples, the base station may send multiple RACH transmission opportunities to the UE within a short time frame (e.g., within milliseconds). The UE may not be able to efficiently determine how many transmission opportunities to utilize for RACH messaging because increasing the number of transmissions may result in a tradeoff between the likelihood of reception at the base station and the ability of the UE to receive further RACH messages from the base station in response.

SUMMARY

The described technology relates to improved methods, systems, devices or apparatus that support determining a number of Random Access Channel (RACH) preamble messages for transmission. In general, the described techniques provide base station resource configuration or User Equipment (UE) determination techniques to determine the number of RACH preamble messages for transmission. In some wireless communication systems, a UE may transmit multiple RACH preamble messages within a Random Access Response (RAR) window to initiate a RACH procedure (e.g., a contention-free or contention-based random access procedure). The UE may transmit a RACH preamble message in a transmission opportunity corresponding to a reference signal received from the base station. In some cases, the UE may determine the number of RACH preamble messages to transmit within a RAR window based on the UE's ability to simultaneously monitor RAR messages in response to each transmitted message. For example, a UE may receive a set of reference signals (e.g., Synchronization Signal Blocks (SSBs), channel state information reference signals (CSI-RS), etc.) that includes a RACH transmission opportunity, and may determine the number of RACH preamble messages to transmit in the transmission opportunity based on which and how many downlink receive beams the UE may monitor for responses. In other cases, the UE may transmit an indication of one or more capabilities of the UE to the base station. The base station may determine a RACH resource configuration for the UE based on the received capabilities and may transmit an indication of the resource configuration to the UE. The UE may determine a number of RACH preamble messages to transmit based at least in part on the received configuration.

A method of wireless communication at a UE is described. The method can comprise the following steps: receiving a set of reference signals, wherein each reference signal in the set of reference signals corresponds to at least one transmission opportunity for a RACH preamble message transmission; and determining a number of RACH preamble messages to transmit in response to the received reference signal set, wherein the determination is based at least in part on a capability of the UE to simultaneously monitor RAR messages corresponding to the number of RACH preamble messages. The method may further comprise: transmitting the determined number of RACH preamble messages based at least in part on the determination, wherein each RACH preamble message of the number of RACH preamble messages corresponds to a reference signal in the received reference signal set.

An apparatus for wireless communication at a UE is described. The apparatus may include: means for receiving a set of reference signals, wherein each reference signal in the set of reference signals corresponds to at least one transmission opportunity for a RACH preamble message transmission; and means for determining a number of RACH preamble messages to transmit in response to the received reference signal set, wherein the determination is based at least in part on a capability of the UE to simultaneously monitor RAR messages corresponding to the number of RACH preamble messages. The apparatus may further comprise: means for transmitting a determined number of RACH preamble messages based at least in part on the determination, wherein each RACH preamble message of the number of RACH preamble messages corresponds to a reference signal of the received reference signal set.

Another apparatus for wireless communication at a UE is described. The apparatus may include a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions are operable to cause the processor to: receiving a set of reference signals, wherein each reference signal in the set of reference signals corresponds to at least one transmission opportunity for a RACH preamble message transmission; and determining a number of RACH preamble messages to transmit in response to the received reference signal set, wherein the determination is based at least in part on a capability of the UE to simultaneously monitor RAR messages corresponding to the number of RACH preamble messages. The instructions are further operable to cause the processor to: transmitting the determined number of RACH preamble messages based at least in part on the determination, wherein each RACH preamble message of the number of RACH preamble messages corresponds to a reference signal in the received reference signal set.

A non-transitory computer-readable medium for wireless communication at a UE is described. The non-transitory computer-readable medium may include instructions operable to cause a processor to: receiving a set of reference signals, wherein each reference signal in the set of reference signals corresponds to at least one transmission opportunity for a RACH preamble message transmission; and determining a number of RACH preamble messages to transmit in response to the received reference signal set, wherein the determination is based at least in part on a capability of the UE to simultaneously monitor RAR messages corresponding to the number of RACH preamble messages. The instructions are further operable to cause the processor to: transmitting the determined number of RACH preamble messages based at least in part on the determination, wherein each RACH preamble message of the number of RACH preamble messages corresponds to a reference signal in the received reference signal set.

In some examples of the above methods, devices, and non-transitory computer-readable media, transmitting the determined number of RACH preamble messages involves transmitting the determined number of RACH preamble messages in a RAR window. In some examples of the above methods, devices, and non-transitory computer-readable media, transmitting the determined number of RACH preamble messages in the RAR window involves transmitting at least one of the determined number of RACH preamble messages before expiration of the RAR window, wherein the RAR window corresponds to a previously transmitted RACH preamble message.

In some examples of the above methods, devices, and non-transitory computer-readable media, transmitting the determined number of RACH preamble messages involves transmitting a plurality of RACH preamble messages within a RAR window corresponding to a same reference signal in a reference signal set based at least in part on the same reference signal corresponding to a plurality of transmission opportunities for RACH preamble message transmission.

In some examples of the above methods, devices, and non-transitory computer-readable media, the RAR window corresponds to a first RACH preamble message of the number of RACH preamble messages.

Some examples of the above methods, apparatus, and non-transitory computer-readable media may further include processes, features, means, or instructions for: monitoring a set of RAR messages, wherein each RAR message in the set of RAR messages may be in response to an associated RACH preamble message of the number of RACH preamble messages. In some examples of the above methods, devices, and non-transitory computer-readable media, each reference signal in the set of reference signals may be received on a particular receive beam, and wherein monitoring the set of RAR messages involves monitoring each RAR message on a particular receive beam for the reference signal corresponding to the associated RACH preamble message.

Some examples of the above methods, apparatus, and non-transitory computer-readable media may further include processes, features, means, or instructions for receiving one or more RAR messages in response to one or more of the number of RACH preamble messages. Some examples of the above methods, apparatus, and non-transitory computer-readable media may further include processes, features, means, or instructions for: stopping monitoring based at least in part on receiving a first RAR message in response to one or more of the number of RACH preamble messages.

Some examples of the above methods, apparatus, and non-transitory computer-readable media may further include processes, features, means, or instructions for: selecting one of the plurality of received RAR messages based at least in part on an order of receipt of the plurality of received RAR messages, an indicated RACH message 3(Msg3) transmission power for the plurality of received RAR messages, an estimated received power for the plurality of received RAR messages, a pseudo-random selection procedure, or a combination thereof. Some examples of the above methods, apparatus, and non-transitory computer-readable media may further include processes, features, means, or instructions for: transmitting a single RACH Msg3 in response to the plurality of received RAR messages based at least in part on the selection. Some examples of the above methods, apparatus, and non-transitory computer-readable media may further include processes, features, means, or instructions for transmitting multiple RACH Msg3 transmissions in response to multiple received RAR messages.

In some examples of the above methods, devices, and non-transitory computer-readable media, the ability of the UE to monitor the RAR message for each corresponding RACH preamble message may be based at least in part on the number of sub-arrays, the number of receive panels, the number of UE diversity branches, the number of reference signals received on each receive beam, or a combination thereof.

In some examples of the above methods, devices, and non-transitory computer-readable media, determining the number of RACH preamble messages to transmit may be further based at least in part on whether each reference signal in the reference signal set may be received at a reference signal received power greater than a reference signal received power threshold. In some examples of the above methods, apparatus, and non-transitory computer-readable media, each reference signal in the set of reference signals may be received simultaneously at a reference signal received power that is greater than a reference signal received power threshold. In some examples of the above methods, apparatus, and non-transitory computer-readable media, each reference signal in the set of reference signals may be received with the same beam at a reference signal received power that is greater than a reference signal received power threshold. Some examples of the above methods, apparatus, and non-transitory computer-readable media may further include processes, features, means, or instructions for: the reference signal received power threshold is determined based at least in part on a network configuration.

In some examples of the above methods, apparatus, and non-transitory computer-readable media, the reference signal set comprises SSBs, CSI-RSs, or a combination thereof.

In some examples of the above methods, devices, and non-transitory computer readable media, at least one of the number of RACH preamble messages corresponds to a contention-free RACH procedure. Some examples of the above methods, apparatus, and non-transitory computer-readable media may further include processes, features, means, or instructions for receiving a single RAR message in response to multiple RACH preamble messages.

In some examples of the above methods, devices, and non-transitory computer readable media, at least one of the number of RACH preamble messages corresponds to a contention-based RACH procedure. In some examples of the above methods, devices, and non-transitory computer-readable media, determining the number of RACH preamble messages to transmit may be further based at least in part on a maximum number of RACH preamble messages to transmit in the RAR window.

A method of wireless communication at a base station is described. The method can comprise the following steps: transmitting a set of reference signals, wherein each reference signal in the set of reference signals corresponds to at least one transmission opportunity for a RACH preamble message transmission; and receiving a number of RACH preamble messages from the UE based at least in part on the UE's ability to simultaneously monitor RAR messages in response to the number of RACH preamble messages, wherein each of the number of RACH preamble messages corresponds to a reference signal in the reference signal set. The method may further comprise: transmitting at least one RAR message in response to the number of RACH preamble messages.

An apparatus for wireless communication at a base station is described. The apparatus may include: means for transmitting a set of reference signals, wherein each reference signal in the set of reference signals corresponds to at least one transmission opportunity for a RACH preamble message transmission; and means for receiving a number of RACH preamble messages from the UE based at least in part on the UE's ability to simultaneously monitor RAR messages in response to the number of RACH preamble messages, wherein each of the number of RACH preamble messages corresponds to a reference signal in the reference signal set. The apparatus may further comprise: means for transmitting at least one RAR message in response to the number of RACH preamble messages.

Another apparatus for wireless communication at a base station is described. The apparatus may include a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions are operable to cause the processor to: transmitting a set of reference signals, wherein each reference signal in the set of reference signals corresponds to at least one transmission opportunity for a RACH preamble message transmission; and receiving a number of RACH preamble messages from the UE based at least in part on the UE's ability to simultaneously monitor RAR messages in response to the number of RACH preamble messages, wherein each of the number of RACH preamble messages corresponds to a reference signal in the reference signal set. The instructions are further operable to cause the processor to: transmitting at least one RAR message in response to the number of RACH preamble messages.

A non-transitory computer-readable medium for wireless communication at a base station is described. The non-transitory computer-readable medium may include instructions operable to cause a processor to: transmitting a set of reference signals, wherein each reference signal in the set of reference signals corresponds to at least one transmission opportunity for a RACH preamble message transmission; and receiving a number of RACH preamble messages from the UE based at least in part on the UE's ability to simultaneously monitor RAR messages in response to the number of RACH preamble messages, wherein each of the number of RACH preamble messages corresponds to a reference signal in the reference signal set. The instructions are further operable to cause the processor to: transmitting at least one RAR message in response to the number of RACH preamble messages.

In some examples of the above methods, apparatus, and non-transitory computer-readable media, receiving the number of RACH preamble messages from the UE involves receiving the number of RACH preamble messages from the UE in a RAR window. In some examples of the above methods, devices, and non-transitory computer-readable media, receiving the number of RACH preamble messages from the UE in the RAR window involves receiving at least one of the number of RACH preamble messages before expiration of the RAR window, wherein the RAR window corresponds to a previously received RACH preamble message. In some examples of the above methods, devices, and non-transitory computer-readable media, the at least one RAR message may be transmitted in a RAR window.

In some examples of the above methods, devices, and non-transitory computer-readable media, transmitting the at least one RAR message involves transmitting a single RAR message in response to the number of RACH preamble messages. In other examples of the above methods, devices, and non-transitory computer-readable media, transmitting the at least one RAR message involves transmitting the RAR message in response to each received RACH preamble message of the number of RACH preamble messages.

Some examples of the above methods, apparatus, and non-transitory computer-readable media may further include processes, features, means, or instructions for receiving one or more RACH Msg3 transmissions in response to the at least one RAR message.

An additional method of wireless communication at a UE is described. The method can comprise the following steps: transmitting an indication of one or more capabilities of the UE; receiving an indication of resources configured for a plurality of RACH preamble message transmissions based at least in part on one or more capabilities of the UE; and transmitting a number of RACH preamble messages according to the configured resources.

An apparatus for wireless communication at a UE is described. The apparatus may include: means for transmitting an indication of one or more capabilities of a UE; means for receiving an indication of resources configured for a plurality of RACH preamble message transmissions based at least in part on one or more capabilities of the UE; and means for transmitting a number of RACH preamble messages according to the configured resources.

Another apparatus for wireless communication at a UE is described. The apparatus may include a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions are operable to cause the processor to: transmitting an indication of one or more capabilities of the UE; receiving an indication of resources configured for a plurality of RACH preamble message transmissions based at least in part on one or more capabilities of the UE; and transmitting a number of RACH preamble messages according to the configured resources.

A non-transitory computer-readable medium for wireless communication at a UE is described. The non-transitory computer-readable medium may include instructions operable to cause a processor to: transmitting an indication of one or more capabilities of the UE; receiving an indication of resources configured for a plurality of RACH preamble message transmissions based at least in part on one or more capabilities of the UE; and transmitting a number of RACH preamble messages according to the configured resources.

In some examples of the above methods, devices, and non-transitory computer-readable media, receiving an indication of resources configured for multiple RACH preamble message transmissions further involves receiving an indication of resources configured for multiple RACH preamble message transmissions within a RAR window.

In some examples of the above methods, apparatus, and non-transitory computer-readable media, the one or more capabilities include a maximum number of reference signals that the UE can detect from one or more base stations simultaneously. In some examples of the above methods, apparatus, and non-transitory computer-readable media, the UE may detect the maximum number of reference signals simultaneously at a reference signal received power that is greater than a reference signal received power threshold. In some examples of the above methods, apparatus, and non-transitory computer-readable media, the reference signal comprises an SSB, a CSI-RS, or a combination thereof.

In some examples of the above methods, apparatus, and non-transitory computer-readable media, the one or more capabilities include a number of sub-arrays, a number of receive panels, a number of UE diversity branches, a number of receive beams, a number of transmit beams, or a combination thereof.

In some examples of the above methods, apparatus, and non-transitory computer-readable media, the one or more capabilities include a level of beam correspondence for the UE. Some examples of the above methods, apparatus, and non-transitory computer-readable media may further include processes, features, means, or instructions for receiving a set of reference signals, wherein a number of transmission opportunities for RACH preamble message transmission for each reference signal in the set of reference signals may be based at least in part on a number of transmit beams for each receive beam used by the UE.

In some examples of the above methods, apparatus, and non-transitory computer-readable media, the indication of the configured resources comprises a handover (handover) message, Radio Resource Control (RRC) signaling, a Medium Access Control (MAC) Control Element (CE), Downlink Control Information (DCI), a Master Information Block (MIB), remaining system information (RMSI), Other System Information (OSI), or a combination thereof.

In some examples of the above methods, devices, and non-transitory computer-readable media, the configured resource corresponds to a contention-free RACH procedure.

An additional method of wireless communication at a base station is described. The method can comprise the following steps: receiving an indication of one or more capabilities of a UE; configuring resources for a plurality of RACH preamble message transmissions based at least in part on one or more capabilities of the UE; and transmitting an indication of the configured resources to the UE.

An apparatus for wireless communication at a base station is described. The apparatus may include: means for receiving an indication of one or more capabilities of a UE; means for configuring resources for a plurality of RACH preamble message transmissions based at least in part on one or more capabilities of the UE; and means for transmitting an indication of the configured resources to the UE.

Another apparatus for wireless communication at a base station is described. The apparatus may include a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions are operable to cause the processor to: receiving an indication of one or more capabilities of a UE; configuring resources for a plurality of RACH preamble message transmissions based at least in part on one or more capabilities of the UE; and transmitting an indication of the configured resources to the UE.

A non-transitory computer-readable medium for wireless communication at a base station is described. The non-transitory computer-readable medium may include instructions operable to cause a processor to: receiving an indication of one or more capabilities of a UE; configuring resources for a plurality of RACH preamble message transmissions based at least in part on one or more capabilities of the UE; and transmitting an indication of the configured resources to the UE.

In some examples of the above methods, apparatus, and non-transitory computer-readable media, configuring resources for multiple RACH preamble transmissions further involves configuring resources for multiple RACH preamble message transmissions within a RAR window.

In some examples of the above methods, apparatus, and non-transitory computer-readable media, the one or more capabilities include a maximum number of reference signals that the UE may detect from one or more base stations within a time window. In some examples of the above methods, apparatus, and non-transitory computer-readable media, the maximum number of reference signals may be based at least in part on a reference signal received power threshold. In some examples of the above methods, apparatus, and non-transitory computer-readable media, the reference signal comprises an SSB, a CSI-RS, or a combination thereof.

In some examples of the above methods, apparatus, and non-transitory computer-readable media, the one or more capabilities include a number of sub-arrays, a number of receive panels, a number of UE diversity branches, a number of receive beams, a number of transmit beams, or a combination thereof.

In some examples of the above methods, apparatus, and non-transitory computer-readable media, the one or more capabilities include a level of beam correspondence for the UE. Some examples of the above methods, apparatus, and non-transitory computer-readable media may further include processes, features, means, or instructions for transmitting a set of reference signals, wherein the number of transmission opportunities for RACH preamble message transmission for each reference signal in the set of reference signals may be based at least in part on the number of transmit beams for each receive beam used by the UE.

In some examples of the above methods, apparatus, and non-transitory computer-readable media, the indication of the configured resources comprises a handover message, RRC signaling, MAC CE, DCI, MIB, RMSI, OSI, or a combination thereof.

Some examples of the above methods, apparatus, and non-transitory computer-readable media may further include processes, features, means, or instructions for receiving a number of RACH preamble messages according to the configured resources. In some examples of the above methods, devices, and non-transitory computer-readable media, the configured resource corresponds to a contention-free RACH procedure.