Method for determining resources and wireless transmit/receive unit
阅读说明：本技术 用于确定资源的方法和无线发射/接收单元 (Method for determining resources and wireless transmit/receive unit ) 是由 M-i·李 J·A·斯特恩-波科维茨 V·科姆沙 江美龙 于 2014-01-24 设计创作，主要内容包括：于此公开了一种用于确定资源的方法和无线发射/接收单元。所述方法包括：测量从基站传送的多个波束参考信号；从测量的所述多个波束参考信号中选择波束参考信号；从所述基站接收配置消息,所述配置消息包括关于所述多个波束参考信号的对应信息,其中所述对应信息为所述多个波束参考信号的每一者指派至少一个物理随机接入信道(PRACH)资源集合,其中所述配置消息是广播消息或无线电资源控制(RRC)消息中的至少一者；基于所接收的对应信息,确定为所选择的波束参考信号指派的PRACH资源集合；以及使用所确定的PRACH资源集合中的至少一个PRACH资源来传送PRACH信号。(A method and wireless transmit/receive unit for determining resources is disclosed herein. The method comprises the following steps: measuring a plurality of beam reference signals transmitted from a base station; selecting a beam reference signal from the plurality of beam reference signals measured; receiving a configuration message from the base station, the configuration message comprising corresponding information regarding the plurality of beam-reference signals, wherein the corresponding information assigns at least one set of Physical Random Access Channel (PRACH) resources for each of the plurality of beam-reference signals, wherein the configuration message is at least one of a broadcast message or a Radio Resource Control (RRC) message; determining a set of PRACH resources assigned for the selected beam-reference signal based on the received corresponding information; and transmitting the PRACH signal using at least one PRACH resource of the determined set of PRACH resources.)
1. A method for determining resources in a wireless transmit/receive unit, WTRU, the method comprising:
measuring a plurality of beam reference signals transmitted from a base station;
selecting a beam reference signal from the plurality of beam reference signals measured;
receiving a configuration message from the base station, the configuration message comprising corresponding information regarding the plurality of beam-reference signals, wherein the corresponding information assigns at least one set of Physical Random Access Channel (PRACH) resources for each of the plurality of beam-reference signals, wherein the configuration message is at least one of a broadcast message or a Radio Resource Control (RRC) message;
determining a set of PRACH resources assigned for the selected beam-reference signal based on the received corresponding information; and
transmitting the PRACH signal using at least one PRACH resource of the determined set of PRACH resources.
2. The method of claim 1, wherein the corresponding information regarding the plurality of beam-reference signals comprises a plurality of measurement configurations.
3. The method of claim 1, wherein the determined set of PRACH resources comprises at least one PRACH preamble, and wherein the PRACH signal is a PRACH preamble of the determined set of PRACH resources.
4. The method of claim 1, wherein the WTRU selects a beam reference signal based on determining that the measured beam reference signal power is better than a threshold on at least one beam reference signal.
5. The method of claim 1, wherein the at least one set of PRACH resources is allocated based on a total number of the plurality of beam-reference signals.
6. The method of claim 1, wherein the beam-reference signal is a channel state information-reference signal (CSI-RS).
7. The method of claim 1, wherein the determined set of PRACH resources comprises at least one set of time resources, and wherein the PRACH signal is transmitted in one of the set of time resources.
8. The method of claim 1, wherein the beam is a 3-D beam.
9. The method of claim 1, further comprising:
determining the PRACH signal based on the received corresponding information.
10. A wireless transmit/receive unit (WTRU) for determining resources, the WTRU comprising:
a processor; and
a transceiver operatively coupled to the processor;
wherein:
the processor and the transceiver are configured to measure a plurality of beam-reference signals transmitted from a base station;
the processor is configured to select a beam-reference signal from the plurality of beam-reference signals measured;
the transceiver is configured to receive a configuration message from the base station, the configuration message including corresponding information regarding the plurality of beam-reference signals, wherein the corresponding information assigns at least one set of Physical Random Access Channel (PRACH) resources for each of the plurality of beam-reference signals, wherein the configuration message is at least one of a broadcast message or a Radio Resource Control (RRC) message;
the processor is configured to determine a set of PRACH resources assigned for the selected beam-reference signal based on the received corresponding information; and
the processor and the transceiver are configured to transmit a PRACH signal using at least one PRACH resource of the determined set of PRACH resources.
11. The WTRU of claim 10, wherein the corresponding information regarding the plurality of beam-reference signals includes a plurality of measurement configurations.
12. The WTRU of claim 10, wherein the determined set of PRACH resources includes at least one PRACH preamble, and wherein the PRACH signal is a PRACH preamble of the determined set of PRACH resources.
13. The WTRU of claim 10, wherein the processor selects a beam reference signal based on determining that the measured beam reference signal power is better than a threshold on at least one beam reference signal.
14. The WTRU of claim 10, wherein the at least one set of PRACH resources is allocated based on a total number of the plurality of beam-reference signals.
15. The WTRU of claim 10, wherein the beam-reference signal is a channel state information-reference signal (CSI-RS).
16. The WTRU of claim 10, wherein the determined set of PRACH resources includes at least one set of time resources, and wherein the PRACH signal is transmitted in one of the set of time resources.
17. The WTRU of claim 10, wherein the beam is a 3-D beam.
18. The WTRU of claim 10, further comprising:
wherein the processor is further configured to determine the PRACH signal based on the received corresponding information.
19. A method for determining resources in a wireless transmit/receive unit, WTRU, the method comprising:
measuring a plurality of beam reference signals transmitted from a base station;
selecting a beam reference signal from the plurality of beam reference signals measured;
receiving a configuration message from the base station, the configuration message including corresponding information regarding the plurality of beam-reference signals, wherein the corresponding information provides at least one set of Physical Random Access Channel (PRACH) preambles for each of the plurality of beam-reference signals, wherein the set of PRACH preambles includes one or more PRACH preambles, wherein the configuration message is at least one of a broadcast message or a Radio Resource Control (RRC) message;
determining a set of PRACH preambles assigned for the selected beam-reference signal based on the received corresponding information; and
transmitting a PRACH preamble using the determined PRACH preamble set.
20. The method of claim 19, wherein the corresponding information regarding the plurality of beam-reference signals comprises a plurality of measurement configurations.
21. The method of claim 19, wherein the WTRU selects a beam reference signal based on determining that the measured beam reference signal power is better than a threshold on at least one beam reference signal.
22. The method of claim 19, wherein the at least one set of PRACH preambles is allocated based on a total number of the plurality of beam-reference signals.
23. The method of claim 19, wherein the beam-reference signal is a channel state information-reference signal (CSI-RS).
24. The method of claim 19, wherein the beam is a 3-D beam.
25. The method of claim 19, further comprising:
determining the PRACH preamble based on the received corresponding information.
Background
Reference Signals (RSs) may be divided into wireless transmit/receive unit (WTRU) -specific reference signals (WTRU-RSs) and cell-specific reference signals (CRSs). The WTRU-RS may be used for a particular WTRU such that the RS is transmitted for the resources allocated to the WTRU. On the other hand, the CRS may be shared by all WTRUs in the cell, so that the RS transmits in a wideband manner. In addition, the reference signal may be further distinguished into a demodulation reference signal (DM-RS) and a channel state information reference signal (CSI-RS) according to the use of the reference signal.
The DM-RS may be used only for a specific WTRU and the RS is typically precoded to exploit the beamforming gain. CRS may be defined for all WTRUs in a cell and for demodulation and measurement purposes.
Disclosure of Invention
A method and apparatus for determining a vertical beam for reception is disclosed herein. A method for use in a wireless transmit/receive unit (WTRU) includes receiving a broadcast message from an evolved node b (eNB), the message including information associated with a plurality of vertical beams, wherein the information includes at least one set of physical random access control channel (PRACH) resources associated with each of the plurality of vertical beams, measuring a reference signal transmitted on each of the plurality of vertical beams to select a receive vertical beam, transmitting a PRACH preamble in the set of resources associated with the selected receive vertical beam, and receiving a communication from the eNB using the selected receive vertical beam.
Drawings
The invention will be understood in more detail from the following description, given by way of example and understood in conjunction with the accompanying drawings, in which:
FIG. 1A is a system diagram of an exemplary communication system in which one or more disclosed embodiments may be implemented;
FIG. 1B is a system diagram of an exemplary wireless transmit/receive unit (WTRU) for use in the communication system shown in FIG. 1A;
fig. 1C is a system diagram of an exemplary radio access network and an exemplary core network for the communication system shown in fig. 1A;
figure 2 is a diagram of WTRU-specific precoded demodulation reference signals (DM-RSs);
FIG. 3 is a diagram of non-precoded cell-specific Reference Signals (RSs);
figure 4 is an illustration of WTRU-specific DM-RS for standard Cyclic Prefix (CP);
fig. 5 is an illustration of a cell-specific reference signal (CRS) structure depending on the number of antenna ports;
FIG. 6 is an illustration of a DM-RS pattern supporting up to eight layers;
FIG. 7 is a diagram of channel state information reference signal (CSI-RS) pattern reuse according to the number of ports;
FIG. 8 is a timing diagram of an example of periodic reporting;
fig. 9 is a block diagram of an Active Antenna System (AAS) radio architecture;
fig. 10 is a diagram of vertical functional partitioning (sectorization) with AAS radio architecture;
figure 11 is an illustration of WTRU-specific elevation (elevation) beamforming using AAS;
fig. 12 is an illustration of a contention-based random access procedure;
FIG. 13 is a diagram of a downlink beam tracking reference signal (d-BTRS) using a four-port CSI-RS pattern;
fig. 14 is an exemplary method for receiving a receive vertical beam.
Detailed Description
Fig. 1A is an illustration of an
As shown in fig. 1A, the
The
The
More specifically, as previously described,
In another embodiment, the
In other embodiments, the
For example, the base station 114B in fig. 1A may be a wireless router, a home node B, a home enodeb, or an access point, and may use any suitable RAT for facilitating wireless connectivity in a local area such as a company, home, vehicle, campus, and the like. In one embodiment, the
The RAN104 may communicate with a
The
Some or all of the
Figure 1B is a system diagram of an
The
Transmit/receive
Furthermore, although transmit/receive
The
The
The
The
Fig. 1C is a system block diagram of the RAN104 and the
The RAN104 may include enodebs 140a, 140B, 140c, it being understood that the RAN104 may include any number of enodebs and remain consistent with embodiments. The
each of the enodebs 140a, 140B, 140c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the uplink and/or downlink, and so forth. As shown in FIG. 1C, the
The
The
The serving
The serving
The
Reference Signals (RSs) may be divided into wireless transmit/receive unit (WTRU) -specific reference signals (WTRU-RSs) and cell-specific reference signals (CRSs). The WTRU-RS may be used only for a particular WTRU such that the RS is transmitted for the resources allocated to the WTRU. The CRS may be shared by all WTRUs in a cell so that the RS transmits in a wideband manner. The reference signal may further distinguish between a demodulation reference signal (DM-RS) and a channel state information reference signal (CSI-RS).
The DM-RS may be used for a particular WTRU, and the RS may be precoded in general to take advantage of the beamforming gain. Because the WTRU-specific DM-RS is not shared with other WTRUs in the cell, the DM-RS may be transmitted on the time/frequency resources allocated to the WTRU. The DM-RS may be used for demodulation purposes only.
Figure 2 is an example of WTRU-specific precoding DM-RS. Fig. 2 includes a
Fig. 2 shows that if precoding DM-RS is utilized, the RS can be precoded with the same precoding used for the data symbols and the same number of RS sequences, corresponding to the number of transmitted layers, K. Here, K is equal to or less than the number N of antenna portst。
In fig. 2, K beams may be allocated for a WTRU or shared with multiple WTRUs. If multiple WTRUs share K beams, then co-scheduled WTRUs may share the same time/frequency resource at the same time. Measurement reference signals such as CSI-RS may be used together for the WTRU to measure channel state information if precoded DM-RS is used.
CRS may be defined for all WTRUs in a cell and may be used for demodulation and measurement purposes. Since CRS is shared by all WTRUs, non-precoded RS may typically be utilized to keep cell coverage consistent. Precoded RSs may have different cell coverage depending on the direction due to the beamforming effect.
Fig. 3 is an example of a non-precoded cell-specific RS. Fig. 3 includes a
Fig. 3 shows an example of a multiple-input multiple-output (MIMO) transmitter for non-precoded CRS transmission. In some cases, WTRU transparent antenna virtualization may be used if the number of physical antenna elements is different from the number of logical antenna ports. The RS sequence can be transmitted on all antenna ports regardless of the number of beams.
Figure 4 is an example of WTRU-specific DM-RS (port-5) for standard CP. Fig. 4 shows DM-RS (antenna port 5400) defined to support non-codebook based transmission at an evolved node b (enb) in an LTE system and the antenna port 5400 supports only single layer transmission. Since antenna port 5400 is always transmitted over CRS, the total RS overhead may increase significantly.
Fig. 5 is an example of a CRS structure depending on the number of antenna ports. Fig. 5 shows CRS patterns for
A predefined RS sequence (e.g., a pseudo-random noise (PN) sequence, etc.) may be transmitted in the RE positions of the CRS ports to minimize inter-cell interference, thereby improving channel estimation accuracy from the CRS. The PN sequence may be applied in a subframe at the OFDM symbol level, and the sequence may be based on the cell ID, subframe number, and OFDM symbolIs defined. For example, the number of CRS antenna ports in an OFDM symbol containing CRS may be two per Physical Resource Block (PRB), and the number of PRBs in an LTE system may vary from 6 to 110. In this case, the total number of antenna ports CRS used in the OFDM symbol containing the RS may be 2 × NRBThis may imply that the sequence length should be
Wherein
wherein
To reduce the total RS overhead, DM-RS based downlink transmission may be introduced into release 10LTE-a systems. The CRS may be a non-precoded RS that is commonly used for all WTRUs in a cell, so the RS sequences for all antenna ports may need to be transmitted all the time. On the other hand, the DM-RS may be a WTRU-specific precoded RS, and the same precoder for PDSCH may be used for DM-RS. In this case, the RS sequence may be transmitted only on the antenna ports for PDSCH transmission, whereby RS overhead may be reduced compared to CRS, since the number of antenna ports used may be less than or equal to the number of antenna ports for CRS depending on the number of layers for PDSCH transmission.
Fig. 6 is an example of a DM-RS pattern supporting up to 8 layers. Fig. 6 shows a DM-RS pattern in a PRB of a subframe by a standard CP as an example. Fig. 6 includes two Code Division Multiplexing (CDM) groups, CDM group 1601 and CDM group 2602. Also shown in fig. 6 is a 4-
CDM groups may be used to multiplex up to 4 layers in each CDM group. Thus, in this mode, up to 8 layers may be multiplexed as a maximum value. For CDM multiplexed to each CDM group, 4 × 4 walsh spreading may be used.
Since DM-RS is only used for demodulation performance, a time/frequency sparse matrix CSI-RS may be introduced for measurement purposes. The CSI-RS may be transmitted with a duty cycle {5,10,20,40,80} ms in a Physical Downlink Shared Channel (PDSCH) region. Furthermore, up to 20 CSI-RS pattern reuses may be used in the subframe as shown in fig. 7.
Fig. 7 is an example of CSI-RS pattern reuse depending on the number of ports. Fig. 7 shows CSI-RS patterns for 2Tx 701, T4x702, and 8Tx 703 antenna ports. In fig. 7, the same hatching indicates a set of REs for a specific CSI-RS configuration. The differently shaded regions represent the Rel-8 CRS704, the Physical Downlink Control Channel (PDCCH) region 705, the
Two types of reporting channels may be used, such as a Physical Uplink Control Channel (PUCCH) and a Physical Uplink Shared Channel (PUSCH). The PUCCH reporting channel may provide robust CSI feedback with limited feedback overhead allowed. The PUSCH reporting channel may allow for a large amount of feedback overhead with lower reliability. Thus, PUCCH reporting channels may be used for periodic CSI feedback for coarse link adaptation, while PUSCH reporting may be triggered periodically for better link adaptation.
Table 1 is an example of reporting modes in LTE/LTE-A.
Table 1: reporting mode in LTE/LTE-A
Scheduling method
Periodic CSI reporting channel
Aperiodic CSI reporting channel
Frequency non-selectivity
PUCCH
Frequency selectivity
PUCCH
PUSCH
CSI feedback may be reported in the formats of Rank Indicator (RI), Precoder Matrix Index (PMI), and Channel Quality Indicator (CQI). The RI and PMI may be computed at the WTRU receiver by selecting a rank and precoding matrix in a predefined codebook, which selection may maximize WTRU throughput. PMI and CQI may be further divided into wideband, subband and WTRU-selected subband, while RI is reported only in wideband manner.
Table 2 further shows the details aperiodic and periodic for CSI feedback depending on the transmission mode.
Table 2: Rel-8/Rel-9 details of transport-dependent CSI feedback
The periodic feedback may be transmitted on PUCCH even though it may be transmitted on PUSCH when a channel is present. Periodic reporting may use different types of reported sequences; these types can be defined as: type 1: a sub-band CQI; type 2: wideband CQI/PMI; type 3: RI; and type 4: wideband CQI.
Fig. 8 is an example of a periodic report. A typical reporting sequence is shown in fig. 8, where the numbers in each rectangle correspond to the above report types. Type 3RI may be reported with the longest duty cycle defined as Hx MRI x NP sub-frame, where H, MRI and NP are configured by higher layers. Type 2802 wideband CQI/PMI may be reported with a longer duty cycle than type 1803 subband CQI, since subband CQI changes more frequently over time due to its short-term channel characteristics.
Aperiodic feedback may be requested through
In LTE Rel-10, the type of periodic PUCCH feedback may be further extended to the following types for eight transmit antenna ports:
In the
An Active Antenna System (AAS) may control a smart antenna system for signal processing. Fig. 9 is a general block diagram of an AAS radio architecture. As shown in fig. 9, the AAS system consists of three components, namely a Digital Signal Processing (DSP) controller 901 (also known as a beam controller), an
Fig. 10 is an exemplary concept of vertical functional partitioning with AAS radio architecture. Fig. 10 shows an example of 1
Figure 11 is an example of WTRU-specific elevation beamforming using AAS. In addition to vertical functional sectorization, the
In LTE, Random Access (RA) procedures may be used in certain scenarios, e.g., one or more of the following scenarios: 1) for RRC connection requests, such as for initial access or registration; 2) for RRC connection re-establishment, such as radio link failure below; 3) during handover to access a target cell; 4) to obtain Uplink (UL) synchronization, such as when UL synchronization is lost and Downlink (DL) data arrives or UL data is transmitted; 5) when the WTRU has UL data to transmit and no dedicated resources (e.g., no PUCCH resources already allocated to the WTRU); and 6) timing advance is needed for positioning purposes, such as WTRU positioning.
There are two forms of RA procedures possible: contention-based (may also be referred to as common), may be applied to the first five events above, and non-contention-based (may also be referred to as contention-free or dedicated), may be applied or applied only to handover, DL data arrival, and positioning.
When using a contention-based RA procedure, the WTRU may initiate processing by transmitting an RA preamble randomly selected from a common pool of preambles and communicated to the WTRU by the network (e.g., via broadcast system information). The WTRU may transmit a preamble on a PRACH resource (e.g., a resource in time and frequency) selected by the WTRU from a set of allowed resources, which may be communicated to the WTRU by the network (e.g., via broadcast system information). The allowed set of PRACH resources may be referred to as a cell configured set of PRACH resources. The time unit of the PRACH resource may be a subframe. The subframe selected by the WTRU for the PRACH resource may be the next subframe configured for the PRACH, where the WTRU may transmit the PRACH (e.g., based on timing, measurements, and other WTRU constraints). The frequency aspect of the PRACH resource (e.g., Resource Blocks (RBs)) selected by the WTRU in the selected subframe may be based on parameters communicated to the WTRU by the network (e.g., via broadcast system information). In some cases, for example, for Frequency Division Duplex (FDD), one frequency resource may be allowed for PRACH in any subframe. The frequency resource may be defined by a starting (minimum) RB number, which may be provided by the network, e.g., a prach-frequency offset (prach-frequency offset), and may have a fixed bandwidth, such as 6 RBs.
When using contention-based RA procedures, it is possible for at least two WTRUs to select the same resource (preamble and PRACH resource) for random access and thus the contention situation may need to be resolved.
When using the non-contention based RA procedure, the WTRU may transmit, over the network, an RA preamble, e.g., a RA-preamble index (RA-preamble index), explicitly signaled to the WTRU. The WTRU may transmit a preamble on a PRACH resource selected from a particular subset of the cell-configured PRACH resources. The subset (e.g., mask) may be explicitly signaled to the WTRUs by the network, e.g., ra-PRACH-mask index (ra-PRACH-MaskIndex). The WTRU may use the indicated resources on the condition that the subset includes only one choice.
In some cases, which may be applicable to one or both RA procedure types, the preamble transmission may be persistent or repeated over more than one subframe. In this case, the selected subframe may be a starting subframe of the transmission.
The terms RACH resources and PRACH resources may be used interchangeably.
Fig. 12 is an example of a contention-based RA procedure. The steps of the contention-based RA procedure are as follows.
The WTRU1201 may transmit 1203 the selected RA preamble on the selected PRACH resource to the
A Random Access Response (RAR)1204 may be formed by the network, such as the
For scheduled
For
For contention-based RA, the WTRU may derive a common pool of preambles from parameters provided by the network. From these parameters, the WTRU may derive a full set of preambles, e.g., a certain number, such as 64 preambles, which may be based on one or more root Zadoff-Chu sequences. The parameter that may specify the use of one or more sequences may be a rootsequence index. The WTRU may receive additional parameters indicating a subset of preambles that may be used by the WTRU and how to divide the subset into two groups (a and B). For example, a number of RA-preambles may define a subset of preambles. The first sizeoffra-preamblsgroupa (the size of RA preamble group a) may be in group a (e.g.,
A PRACH configuration index, such as the PRACH-ConfigIndex, may be used by the network to inform the WTRU which preset list of possible configurations to select for the set of cell-configured PRACH resources. The preset configuration (e.g., for FDD) may define one or more preamble formats that may define a time for a preamble Cyclic Prefix (CP) and a time for the preamble sequence, a System Frame Number (SFN) that allows PRACH (e.g., all, only even, only odd), and subframes (e.g., a particular 1, 2, 3, 4, 5, or all 10 subframes) that allow the allowed SFN of PRACH.
A Power Headroom Report (PHR) may be triggered by the WTRU if any of the following events occur.
The PHR may be triggered if a prohibitPHR-Timer expires or has expired and the pathloss has changed more than dl-pathloss change dB for at least one active serving cell, wherein the pathloss is used as a pathloss reference due to the last transmission of the PHR when the WTRU has UL resources for a new transmission.
The PHR is triggered upon expiration of a periodicPHR-Timer.
The PHR may be triggered by upper layers based on a configuration or reconfiguration of the power headroom reporting functionality that is not used to disable the functionality.
The PHR may be triggered based on activation of a serving cell (SCell) with a configured UL.
PHR may be triggered in the following cases: 1) a prohibit phr-Timer expires or has expired, 2) when the WTRU has UL resources for a new transmission, and 3) on a true following condition in the Transmission Time Interval (TTI) for any active SCell with configured UL: with UL resources allocated for transmission or with PUCCH transmission on the cell, and due to power management for the cellTheory (such as P-MPR)CAllowed) has been allocated UL resources for transmission on that cell or PUCCH transmission because the last transmission of the PHR has changed by more than dl-PathlossChange dB.
The PHR may be transmitted by the WTRU in a particular TTI (which may correspond to a particular subframe) if the WTRU has UL resources allocated for a new transmission for that TTI (or subframe) and the following applies: the power headroom reporting procedure determines that at least one PHR has been triggered and not cancelled, and that the allocated UL resources can accommodate the PHR MAC control element plus its subheader (in case an extendedPHR is not configured); or extended PHR MAC control element plus its subheader (in case the extendedPHR is configured), results in logical channel prioritization.
The WTRU may transmit a Sounding Reference Signal (SRS) to the eNB when configured or triggered to do so. The WTRU may transmit the SRS in the last symbol of the subframe.
The SRS transmission by the WTRU may be periodic or aperiodic. The periodic SRS transmission may be configured by the eNB. Aperiodic SRS transmission may be triggered by the eNB, for example, by including a request for aperiodic SRS with the UL grant.
The cell-specific SRS subframes may be subframes in which SRS may be transmitted in a given cell. The configuration of the cell-specific subframes may be provided in signaling, such as broadcast or dedicated Radio Resource Control (RRC) signaling.
The WTRU-specific SRS subframe may be a subframe in which a particular WTRU may transmit SRS, which may be a subset of a cell-specific SRS subframe. The configuration of WTRU-specific subframes may be provided to the WTRU in signaling, such as dedicated RRC signaling. For periodic and aperiodic SRS, there may be separate WTRU-specific subframes configured for WTRUs.
When an aperiodic SRS is triggered in subframe n, the WTRU may transmit an SRS in the next aperiodic WTRU-specific SRS subframe n + k, where k satisfies a certain criterion, e.g., k > -4.
When one SRS (periodic or aperiodic SRS) and another SRS or channel are both scheduled to be transmitted in the same subframe, the rules and/or configuration parameters may dictate whether the WTRU may transmit the scheduled SRS.
Aperiodic SRS triggers and aperiodic SRS requests may be used interchangeably.
The eNB receiver may estimate a suitable downlink vertical beam (e.g., a transmit vertical beam) for a particular WTRU based on an uplink vertical beam (e.g., a receive vertical beam), thus requiring SRS for receive vertical beam convergence. Since the UL coverage may be different, there is more than 6dB between before and after the receive vertical beam adjustment. Thus, faster receive vertical convergence may reduce interference and increase UL throughput. However, current SRS designs may not allow for faster receive vertical beam convergence because their transmissions have a duty cycle and/or a single subframe transmission may only be once.
To allow for efficient vertical beam adjustment, WTRU reports that aid in vertical beam selection may be used at the eNB. Because the vertical antenna elements cannot be seen by the WTRU, multiple DL reference signals may be used for the WTRU to select the best vertical beam associated with a particular reference signal. However, current DL reference signal structures may not allow for multiple DL reference signals or the overhead of multiple DL reference signals may be too large.
Since SRS transmission is only available after initial cell access, the PRACH procedure may not enjoy the benefits of an Active Antenna System (AAS). Furthermore, the UL coverage of PRACH may be worse than before, as the appropriate UL vertical beam for a particular WTRU may no longer be estimated at the eNB receiver. Thus, PRACH may not have sufficient coverage in the AAS compared to other UL/DL channels.
For RA procedures, such as initial RA procedures, in order to obtain initial access or transmit an RRC connection request, performance needs to be improved by using vertical beamforming. Methods and procedures may be needed for the WTRU to determine the vertical beams used for transmission and the eNB to know which vertical beams to use for reception.
The power headroom report may be updated immediately after the receive beam convergence, since there may be more than a 6dB difference between before and after the receive beam convergence. Current power headroom reporting behavior may not support this case. May be used for the eNB to receive the PHR for the WTRU as soon as possible after the vertical beam convergence for the WTRU has been selected. Methods and processes are needed to accomplish this.
Because the WTRU moves in a cell that spans multiple vertical sectors/beams, the optimal vertical beam for the WTRU may change frequently over time. In order to provide suitable coverage in a vertically sectorized cell, WTRU mobility may be considered even in the cell. Current LTE/LTE-a systems may be inflexible with respect to supporting WTRU mobility across multiple vertical beams within a cell.
New UL reference signals may be defined for better receive beam convergence, and the reference signals may be similar to Sounding Reference Signals (SRS). The UL reference signal on which the reception beam converges may be defined as an uplink beam tracking reference signal (u-BTRS).
In a first example, the u-BTRS may be defined only in the PUSCH region, where the PUSCH region implies that PRBs are not used for PUCCH in a subframe. In this case, one or more of the following may be employed.
The u-BTRS may be transmitted in a subframe configured for a cell-specific u-BTRS subframe and a last single carrier frequency division multiple access (SC-FDMA) symbol, such as SRS. In an example, the cell-specific u-BTRS may be equivalent to a cell-specific SRS subframe. In another example, cell-specific u-BTRS subframes may be configured independently and may be mutually exclusive from cell-specific SRS subframes. Alternatively, the cell-specific u-BTRS subframe may be configured independently of the cell-specific SRS subframe, while the subframe may overlap fully or partially between the u-BTRS and SRS. In the case of overlap, at least one of the following may be utilized: u-BTRS transmissions have a higher priority, whereby all SRS transmissions in a subframe may be dropped; SRS transmissions have a higher priority, whereby all u-BTRSs in a subframe may be dropped; and subframes may be used for u-BTRS transmission or SRS transmission. If both transmissions are triggered and/or scheduled in a subframe, the u-BTRS may have a higher priority and the SRS may be dropped, and vice versa.
The u-BTRS may be transmitted in a subframe configured for a cell-specific u-BTRS subframe (rather than the last SC-FDMA symbol), thus allowing multiplexing of the u-BTRS and SRS in the same subframe in case of scheduling. In this case, one or more of the following may be utilized: the second to last SC-FDMA symbol may be used for the u-BTRS subframe; one of the SC-FDMA symbols for DM-RS may be used for u-BTRS transmission; the last SC-FDMA symbol in the first slot may be used for u-BTRS transmission in the subframe; and SC-FDMA symbols for u-BTRS may be configured by a broadcast channel (e.g., SIB-x).
In the cell-specific u-BTRS subframe, u-BTRS can be transmitted only in the PUSCH region even though SRS can be transmitted in all system bandwidths. Thus, the frequency bandwidth for u-BTRS in a subframe may be smaller than SRS. For example, if the system has 50 PRBs in the UL, the SRS may be transmitted in any position of the 50 PRBs according to the configuration. u-BTRS can only be in center N of PUSCHPUSCHTransmitted in a PRB. In this case, at least one of the following may be utilized: n is a radical ofPUSCHAnd NuBTRSCan be used interchangeably, where NuBTRSRepresents PRBs configured for u-BTRS transmission, which may be defined as independent of PUSCH region; n is a radical ofPUSCHConfigurable by higher layers for indication NPUSCHThe starting PRB number may be indicated; and NPUSCHMay be dynamically indicated in each trigger of u-BTRS.
In a second example, multiple SC-FDMA symbols may be used for u-BTRS in a subframe. If multiple SC-FDMA symbols are used for u-BTRS transmission, it is possible to reduce the reception beam convergence time. For u-BTRS transmission in multiple SC-FDMA symbols, one or more of the following may be utilized.
Multiple SC-FDMA symbols in a subframe for u-BTRS transmission may be located at a center NPUSCH/NuBTRSWithin a PRB.
Last N in subframeuBTRSSymbols may be used for u-BTRS transmission and at least one of the following may be used。NuBTRSMay be defined as a predefined integer. For example, N may be useduBTRS2 or NuBTRS＝3。NuBTRSMay be configured by the eNB via a broadcast channel (e.g., MIB or SIB-x) or higher layer signaling.
Among the plurality of SC-FDMA symbols for u-BTRS transmission, if one SC-FDMA symbol collides with an SC-FDMA symbol for SRS transmission, the collided SC-FDMA symbol may not be used for u-BTRS transmission in a subframe and other SC-FDMA symbols may be used.
When multiple SC-FDMA symbols are used for u-BTRS transmission, the u-BTRS in an SC-FDMA symbol may be transmitted repeatedly in other SC-FDMA symbols at the same frequency position.
In a solution for PUSCH transmission, if a WTRU capable of u-BTRS transmission is scheduled for PUSCH transmission in a cell-specific u-BTRS subframe, at least one of the following WTRU behaviors may be utilized. The WTRU may transmit PUSCH and cell-specific u-BTRS resources around rate matching in a subframe. The WTRU may transmit PUSCH if the WTRU is not scheduled to transmit u-BTRS in a subframe. Otherwise, the WTRU may relinquish the PUSCH and transmit the u-BTRS in the subframe. Alternatively, the WTRU may drop the u-BTRS transmission and transmit PUSCH in the subframe.
A DL beam tracking reference signal (d-BTRS) may be defined for vertical beam measurement purposes so that a WTRU may measure multiple vertical beams from the d-BTRS associated with the vertical beam. Suppose Nvertical(NIs perpendicular to) Beams used in a cell, NverticalThe d-BTRS may be configured such that one d-BTRS may correspond to one vertical beam. In an example, multiple CSI-RSs may be used as d-BTRSs for multiple vertical beam tracking. In this case, one or more of the following may be utilized.
Multiple CSI-RSs may be configured in a cell-specific manner and each CSI-RS may be associated with a vertical beam. To configure cell-specific CSI-RS (e.g., d-BTRS), at least one of the following may be used. The two or more CSI-RS configurations may be signaled to the WTRU via a broadcast channel (e.g., MIB or SIB-x), and the CSI-RS configurations may include at least one of: number of antenna ports, duty cycle, pattern, or subframe offset. The number of antenna ports per cell-specific CSI-RS configuration may be limited to one or two antenna ports, which may be independent of the WTRU-specific CSI-RS configuration. The cell-specific CSI-RS may be transmitted in a subset of the PRBs. For example, the cell-specific CSI-RS may be transmitted in even-numbered PRBs or odd-numbered PRBs. The WTRU may be informed of the subset of PRBs of the cell-specific CSI-RS as part of the CSI-RS configuration.
The vertical beam measurement reporting process may be defined based on multiple cell-specific CSI-RSs for better DL vertical beam tracking at the eNB transmitter. For the vertical beam measurement reporting procedure, WTRU behavior may be defined as at least one of the following. The WTRU may measure two or more cell-specific CSI-RSs and measure received signal-to-noise ratio (SNR) and received signal-to-interference-and-noise ratio (SINR), which may be considered Reference Signal Received Power (RSRP), path loss, wideband CQI, or subband CQI. The WTRU may report the measured received SINR of each cell-specific CSI-RS in a specific UL subframe on a condition scheduled to be reported or triggered in the subframe.
The antenna ports in the cell-specific CSI-RS may correspond to specific vertical beams. A single cell-specific CSI-RS may be configured with two or more antenna ports and each antenna port may be associated with a specific vertical beam. The WTRU may measure the received SINR for each antenna port in the cell-specific CSI-RS and report the measured SINR in a specific UL subframe if reporting or triggering is scheduled in the subframe.
In another example, the new measurement RS may be defined as d-BTRS in order to get better measurement accuracy than CSI-RS.
The new measurement RS (d-BTRS) may be defined with one or more of the following properties. A single antenna port may be defined with 3 or 6 subcarrier spacings. Orthogonal Frequency Division Multiplexing (OFDM) symbols in a subframe may be used as reference signals, which results in 1 subcarrier spacing in the frequency domain. The CSI-RS pattern may be reused by modification.
Fig. 13 is an example of a downlink beam tracking reference signal (d-BTRS) using a four-port CSI-RS pattern. For example, a 4-port CSI-RS pattern may be used as the 2-port d-
Selecting or determining RA resources may include selecting/determining one or more of RA preamble, RA preamble format, and PRACH resources, which may include selecting/determining time and/or frequency aspects (e.g., allocation) of resources. The WTRU may select or determine one or more RA resources based on the at least one measurement.
The eNB may provide and the WTRU may receive one or more measurement configurations, where each measurement configuration may correspond to a signal having one or more particular characteristics that the eNB may transmit. For example, the signal may include a particular vertical (or DL vertical) beam.
In this specification, vertical and DL vertical beams are exemplary features. Any other features may be used and still be consistent with this description.
The eNB may signal the configuration to the WTRU via higher layer signaling, such as broadcast or dedicated RRC signaling.
The measurement configuration may include parameters required for the WTRU to make measurements, such as: the timing of the measurements (e.g., which frames and subframes), the frequency location, the measurement identifier, the type of measurement, or other parameters specific to the type of measurement.
Separately or as part of the measurement configuration, the eNB may indicate a measured association (or measurement configuration) that may correspond to a particular transmission characteristic, such as a vertical beam, with a particular set of RA resources or RA parameters.
The RA resource or RA parameter may include or may cause the WTRU to determine: a set of one or more RA preambles, a preamble format of a RA preamble, or a set of one or more PRACH resources that may include an allocation of frequency and/or time. The indication may be signaled by the eNB to the WTRU via higher layer signaling, such as broadcast or dedicated RRC signaling.
The indication may include any parameters necessary to convey the particular set of RA parameters. For example, the parameters may include: one or more indices in one or more tables with predefined configurations, which may for example define the frames and/or subframes used; one or more masks for use with another configuration (or configurations) that defines a larger set of resources; a specific preamble number (or index); a starting preamble number (or index); a preamble number; a frequency offset of the first RB; or RB number.
An indication of association and/or random access or other related parameters may be provided for individual measurements (or measurement configurations) and/or for group measurements (or measurement configurations).
A set of RA resources may currently be provided in a cell for contention-based RA. Because all WTRUs may use these resources and the eNB may not have specific information about these WTRUs, the eNB may not treat the reception of RA preambles from different WTRUs differently, even though the eNB may need to do so.
One way for the eNB to identify the specific purpose or characteristics of the WTRU transmitting the preamble may be to specify that a specific RA resource is used by the WTRU for a specific purpose or has specific characteristics. For example, the particular characteristic may be a preferred or selected beam direction. The eNB may specify particular RA resources, e.g., particular RA preambles and/or PRACH resources, to use by the WTRU that prefers or selects particular one or more vertical beam directions in the UL and/or DL. To receive these preambles and/or resources, the eNB may use a specific UL vertical beam that may result in better reception performance.
As another example, the particular feature may be that the WTRU has determined that measurements made by the WTRU authorize use of a particular set of RA resources (e.g., a particular RA preamble and/or PRACH resources). For example, if measurements made by the WTRU satisfy certain criteria, the WTRU may select and/or use a RA resource (e.g., RA preamble and/or PRACH resource) of a set of RA resources (e.g., RA preamble and/or PRACH resources) associated with the measurement or measurement configuration.
The set of RA resources may be allocated by the eNB and/or used by the WTRU for RA transmissions when the WTRU has a particular characteristic or purpose.
The set of RA resources associated with a particular feature or purpose may include a set of RA preambles and/or a set of PRACH resources. The set of RA preambles and/or the set of PRACH resources have one or more of the following aspects different from the RA preambles and PRACH resources specified in the cell for contention-based RA: a preamble, a time aspect (or allocation) of PRACH resources, or a frequency aspect (or allocation) of PRACH resources.
In selecting RA resources, a WTRU with a particular purpose or feature may (or may only) select RA resources (e.g., PRACH resources including a preamble and in time and frequency) among a set of RA resources allowed or designated for the particular purpose or feature.
For a set of RA preambles that may be used for a particular purpose or feature, one or more of the following may be utilized.
The RA preamble set may be a designated subset of a full set of preambles existing for a cell. The set may be in a subset of a full set that is not part of group a or group B.
The RA preamble set may be a set of preambles separated from the full set of preambles existing for the cell. The set may have its own root Zadoff-Chu sequence or sequences. Given multiple purposes or features, e.g., vertical beam or measurement configurations, there may be a set (or multiple sets) of preambles that is separate from the full set of preambles existing for the cell, and each purpose or feature may be associated with a subset of the set (or one of the sets).
One set of preambles may be designated for a set of purposes or features, e.g., a set of vertical beams or measurements (or measurement configurations). Given the N purposes or characteristics in the group, the set of preambles may be evenly divided, e.g., based on explicit or implicit configuration, in groups with awareness (understanding) between the WTRU and the eNB, as to which preambles correspond to which member of the group. When the measurements are specific, the awareness may be based on, for example, measurement identity or order of measurement configuration, so that in case the WTRU selects an RA preamble based on a specific measurement that meets the criteria, it is known from which preamble set to select.
The RA preamble set may be preambles in existing groups a and/or B. In this case, the preamble may not be used by the eNB to learn the purpose or feature.
The RA preamble formats used for the preamble set may be different. For example, one or more specific CP lengths, e.g., longer than currently used for a given preamble format, may be used for a specific purpose or feature.
For a set of PRACH resources that may be used for a particular purpose or feature, one or more of the following may be utilized.
The frequency allocation of PRACH resources may be separate or different from the frequency allocation of the set of PRACH resources existing for the cell. Each purpose or feature may have its own frequency resource where the starting RB may be specified. A new frequency resource may be specified for a set of purposes or characteristics, e.g. all vertical beams or all measurements of a specific type.
The time allocation of PRACH resources may be independent of or different from the time allocation for the set of PRACH resources existing for the cell. Each purpose or feature may have its own time allocation. A new time allocation may be specified for a set of purposes or characteristics, e.g., all vertical beams. The time allocation of one or a set of purposes or features may be done through the specification of specific PRACH configuration indices and/or PRACH mask indices, where the configurations and masks corresponding to these indices may be those currently existing, e.g., for all purposes/features, and/or new configurations and masks that may be used. For the case of a set of purposes or features, if one PRACH configuration index is provided, the WTRU may understand how to divide time resources among the group members based on, for example, the specific configuration information it may receive, such as beam or measurement identities or the order of beams or measurements configured or in the configuration. To minimize the impact on the system when having multiple destinations or features, the time allocation for the destinations or features may be less than currently allowed, e.g., less than every other frame.
The WTRU may select or otherwise determine RA resources for RA transmission or a set of RA resources that may be used for RA transmission based on at least one of: one or more measurements; a determination by the WTRU that one or more measurements satisfy certain criteria; the results of the comparison by the at least one measured WTRU with respect to one or more quality criteria or thresholds; the results of the comparison of the two or more measurements; selection of measurements by the WTRU based on particular criteria to be met and/or results of comparisons with one or more other measurements; and measuring an association with one RA resource or a set of RA resources.
The result of the comparison is made by the at least one measured WTRU relative to one or more quality criteria or thresholds. For example, the selection or determination may be made based on the WTRU determining that the measurement is better (or worse) than a threshold. Better may mean greater value, and worse may mean lower value. For example, the WTRU may use the CRS of the cell for RSRP measurements, and if the measurements are greater than a threshold, the WTRU may determine that an existing set of RA resources of the cell (e.g., RA resources not associated with a particular purpose or feature, such as vertical beamforming) may be used.
The result of the comparison of the two or more measurements. For example, the selection and determination may be made based on the WTRU determining that the measurement is better (or worse) than at least one other measurement. For example, the selection or determination may be made based on the WTRU determining that the measurement is the best of the measurement set. Better means greater value, for example by at least one particular threshold. Worse may mean a lower value, e.g. passing at least one particular threshold. In addition to or instead of value, other quality criteria may be used to determine whether one measurement is better (or worse) than another. At least one measurement may need to meet certain other criteria, e.g. quality criteria, to be included in the comparison. For example, the measurement may need to exceed a threshold for inclusion in the comparison.
The WTRU makes the selection of the measurement based on the particular criteria to be met and/or the results of the comparison with one or more other measurements. For example, the WTRU selecting a particular measurement as the best measurement may correspond to the WTRU selecting the best vertical beam.
An association with one RA resource or a set of RA resources is measured. The association of measurements with RA resources may be configured by the eNB, as described above.
One or more measurements may be configured by the eNB, which may mean signaled to the WTRU via higher layer signaling (such as broadcast or dedicated RRC signaling). Such configurations have been described elsewhere herein.
Any threshold that the WTRU may use may be signaled to the WTRU by the eNB, e.g., through broadcast or dedicated signaling.
One or more measurements may be made by the WTRU. The comparison may be performed by the WTRU. The determination as to whether the criteria are met may be performed by the WTRU.
When the selection/determination is of a set of RA resources that may be used for transmission, the WTRU may select a particular RA resource based on a rule similar to an existing rule or may define a new rule.
For example, if there are multiple preambles to choose from, the WTRU may randomly choose one. If there are different preambles to choose from with certain criteria to be met, such as current group a and B preambles, the WTRU may select the preamble in consideration of these criteria. The WTRU may select one randomly if there are multiple frequency resources to choose from. For the time aspect, the WTRU may select the first available subframe in the RA resource set that is allowed to transmit the preamble and may satisfy its time constraint.
In one example, the WTRU may make at least two measurements. The WTRU may compare the measurements and determine which measurement is the best. The WTRU may select or determine the RA resource set associated with the determined best measurement. The WTRU may then select or determine RA resources from the determined set of RA resources and the WTRU may use the resources for RA transmissions.
In another example, the WTRU may first determine whether the measurements meet certain quality criteria, such as whether the measurements exceed a threshold. The WTRU may or may only include the measurement in the comparison if the measurement meets certain criteria. The WTRU may consider only one measurement as the best measurement if it can meet the quality criteria.
In another example, the WTRU may first determine whether a particular criterion is met, such as whether the RSRP of the cell exceeds a threshold. If the criteria are met, the WTRU may use the legacy RA resources for RA transmissions. If the criteria are not met, the WTRU may determine which RA resources to use based on the results of the comparison of measurements associated with the RA resources.
The measurement may be a Reference Signal (RS), wherein the reference signal may be: cell-specific RS (crs), Channel State Information (CSI) RS, Vertical Beam (VB) RS, or any other RS or known signal that may be received by the WTRU or transmitted by the eNB.
If different types of measurements are compared by the WTRU, the eNB may provide parameters to the WTRU to cause the WTRU to adjust one or more measurements prior to the comparison, e.g., to better correlate the measurements.
The WTRU may make and compare measurements for all purposes and features (e.g., existing or legacy measurements) with measurements that may be associated with a particular purpose or feature.
The WTRU may do this without additional configuration from the eNB regarding existing/legacy measurements. The WTRU may understand that these are associated with existing/legacy RA resources.
The WTRU may be provided with multiple RA resources, e.g., one or more RA resource sets, that the WTRU may recognize will be used for a particular purpose or feature. For example, the WTRU may recognize that each RA resource set corresponds to a different vertical beam (where the WTRU may or may not know what each beam direction is), measurement, or measurement configuration. One of these sets may be a set of RA resources that may be used for extant/legacy purposes.
If the WTRU does not know which resource set is the best, the WTRU may, for example, do one or more of: for example, a set is randomly selected from a plurality of RA resource sets; selecting RA resources in the set according to a selection rule (e.g., random selection of preambles in the set, first available subframe in the set that may satisfy a physical timing constraint, etc.); performing an RA procedure (which may include transmitting the selected preamble at a particular power); waiting for RAR; and if no response is received, the WTRU may progressively increase power and try again, which may include repeating RA resource selection from the currently selected RA resource set and increasing power until a RAR is received or a maximum allowed power up or up attempt is reached.
If the WTRU reaches the maximum allowed power up or ramp up attempt, the WTRU may randomly select another set of, for example, RA resources if there is one, and then retry.
The order in which the WTRU selects the RA resource sets may be according to one or more of the following:
the WTRU may select the RA set that is first used for the existing/legacy purpose. The WTRU may determine to select the RA set to be used first for existing/legacy purposes on a condition that it is determined that the measurement (such as RSRP measurement) exceeds a certain threshold.
The WTRU may randomly select a set of RA resources from the provided plurality of sets.
Each time the WTRU selects a RA set, the WTRU may randomly select a set from the multiple sets provided or from a subset of the multiple sets that does not include the set that has been attempted.
The WTRU may select the RA resource sets according to an order configured by the eNB, where the configuration may be signaled to the WTRU by the eNB via signaling (such as broadcast or dedicated RRC signaling).
The WTRU may use the measurements to determine which RA resource set attempts or the order in which the RA resource sets are tried first. When using measurements, the WTRU may select RA resources corresponding to the measurement configuration or the measurement configuration that satisfies certain criteria.
The eNB may use measurements of SRS transmissions from the WTRU to determine a preferred beam direction for UL reception from the WTRU and/or DL transmission to the WTRU.
The eNB may use aperiodic SRS to cause the WTRU to transmit SRS at a particular time.
In order for the eNB to get multiple SRS transmissions, e.g., converge beam directions, the eNB may trigger aperiodic SRS multiple times, where the triggers may be dense in time. For example, the eNB may trigger N aperiodic SRS for the WTRU such that the WTRU is scheduled to transmit and/or transmits SRS in N consecutive WTRU-specific SRS subframes. The consecutive WTRU-specific SRS subframes may not be consecutive subframes, as only the specific subframes may be WTRU-specific SRS subframes.
In order for the eNB to obtain multiple SRS transmissions, e.g., to converge beam directions, the eNB may trigger a multi-slot (multi-shot) aperiodic SRS that may result in the WTRU scheduling to transmit and/or SRS to transmit in N consecutive WTRU-specific SRS subframes. The first subframe in which the WTRU transmits SRS may be a first WTRU-specific subframe that is at least k subframes after the subframe in which the trigger is received, where k may be 4. N may be a known value, a configured value, or a value that provides a trigger.
This is useful for the eNB to receive the PHR after the vertical beam convergence.
To accomplish this, the WTRU may trigger the PHR, for example, based on at least one of: upon receiving the aperiodic SRS request, the request may also include a PHR request; a specific time T, or a number of TTIs or subframes S after receiving an aperiodic SRS request; a specific time T, or a number of TTIs or subframes S after transmission of the aperiodic SRS; a specific time T, or a number of TTIs or subframes S after transmission of the last SRS transmission of the N SRS transmissions triggered by the multi-slot aperiodic SRS request; and a specific time T, or a number of TTIs or subframes S after receiving a dense set of aperiodic SRS requests. For example, if the WTRU receives an aperiodic SRS request in an interval less than B ms, the WTRU may trigger a PHR C ms or TTI or subframe after the last trigger or after the last SRS it transmits in that time interval.
The time T or the number of subframes S may be at least one of: for example, by a known value of a rule; such as configured by higher layer signaling; including aperiodic SRS requests; selected from a set of known values or configured values, such as by an indication that may be included in an aperiodic SRS request; or greater than or equal to 0.
If the aperiodic SRS request includes a PHR request, the PHR may or may only be triggered based on receipt of the aperiodic SRS request.
If it is not possible for the WTRU to transmit a PHR, e.g., if UL resources for a new transmission for which the PHR is suitable are not allocated, the WTRU may transmit the PHR at a later recent time when it is possible when the PHR is transmitted when the PHR is triggered.
Once the criteria for triggering aperiodic SRS related to a PHR are met, the WTRU may continue to trigger the PHR until the PHR is transmitted or is able to be transmitted.
For DL, an eNB, which typically has 3D-MIMO/3D beamforming capability, may require DL CSI to precisely form beams for specific WTRUs, which may be referred to as WTRU-specific beamforming. DL CSI may be obtained using the above-mentioned CSI feedback including PMI/CQI/RI/RSRP/PTI/CPI, etc. The enodeb may also predefine the set of vertical beams (within a single horizontal cell). As described above, each vertical beam may be associated with a particular CSI-RS configuration. To support NVVertical beam, NVThe CSI-RS configuration may be used for the WTRU to measure multiple vertical beams. The WTRU may measure and report Channel State Information (CSI) based on single or multiple CSI-RS configurations. CSI-RS and d-BTRS may be used interchangeably herein. The multiple CSI-RS configurations may be equivalent to multiple d-BTRSs. Furthermore, the d-BTRS may be all or a subset of the antenna ports in the CSI-RS configuration, which may include a single CSI-RS configuration with N ports divided into a plurality of sub-configurationsAnd each subset corresponds to one d-BTRS solution.
As the WTRU moves from one location to another (in the vertical and/or horizontal domain), the desired WTRU-specific 3-D beam (vertical and/or horizontal) may have changed in the vertical domain, the horizontal domain, or both. The desired WTRU-specific beam may need to be updated by WTRU or enodeb triggering events. To support WTRU-specific 3D beamforming, one or more of the following may be utilized.
For any given TTI, the WTRU may measure all CSI-RS configurations and report multiple CSI information (representing vertical beam quality). This may cause excessive feedback overhead. Alternatively, WTRU autonomous behavior may report the best or preferred vertical beam when the desired vertical beam of the WTRU changes due to motion.
The following procedure can be defined. The WTRU k may calculate its wideband SINR γ based on the channel state information and the utilized vertical beamforming (reflected at the current active CSI-RS port)k(Hk,Vk). The WTRU may measure all configured CSI-RS ports and calculate SINR. Once the SINR of the current active CSI-RS port (corresponding to the current vertical beam) drops beyond a defined threshold compared to other configured CSI-RS ports (representing different vertical beams), for example:
Γth: SINR threshold for beam reselection
The WTRU may then report back an indication of the strongest CSI-RS port and beam update associated with the strongest measured SINR. The eNB may update the active vertical beam accordingly for future WTRU transmissions. The active vertical beam update may include a reconfiguration of the active CSI-RS ports. The SINR metric may be replaced with RSRP or RSRQ with the same procedure. Subband or wideband CSI may be used.
The WTRU may be triggered to report a preferred CSI-RS configuration of the plurality of CSI-RS configurations by one or more of the following.
The preferred CSI-RS configuration may be defined as at least one of: a CSI-RS configuration with a maximum wideband CQI (or RSRP) value among a set of CSI-RS configurations, or a CSI-RS configuration that the WTRU prefers to report to CSI including CQI/PMI and/or RI.
The eNB may report a preferred CSI-RS configuration of the plurality of CSI-RS configurations according to the DCI trigger. A trigger bit may be included in the DCI and if the trigger bit indicates "0", the WTRU may not report the preferred CSI-RS configuration, whereas if the trigger bit indicates "1", the WTRU may report the preferred CSI-RS configuration in the corresponding UL subframe. The corresponding UL subframe may be n +4, where n is the subframe index where the WTRU receives the trigger.
The WTRU may report the preferred CSI-RS configuration if at least one of the following conditions is met. The previously preferred CSI-RS configuration has a lower wideband CQI (or RSRP) than any other CSI-RS configuration in subframe k, and the gap between the best CSI-RS configuration and the previously preferred CSI-RS configuration is greater than a predetermined threshold. The CSI-RS configuration with the highest wideband CQI (or RSRP) is changed and the gap is greater than a predetermined threshold.
The WTRU may be configured to periodically report the preferred CSI-RS configuration. Such as at each Ncycle(NCirculation of)[ms]The WTRU may report the preferred CSI-RS configuration. In this case, one or more of the following may be utilized:
the preferred CSI-RS configuration may be Vindex(VIndexing) Is reported, and VindexThe report may be by any of the following: independent of PMI/RI/CQI and/or PTI, or via use of PUCCH format2/2a/2 b.
Preferred CSI-RS configuration (e.g., V)index) Reporting may be performed via PUSCH in a piggybacked manner. In this case, VindexMay be the same as the RI.
The WTRU may be configured with multiple CSI-RS configurations and CSI reporting (e.g., CQI/PMI/RI and/or PTI) may be based on the associated CSI-RS configuration, which may be signaled by the eNB. In this case, one or more of the following may be utilized:
the associated CSI-RS configuration may be signaled via higher layer signaling. If aperiodic CSI reporting is used, the associated CSI-RS configuration may be indicated in the DCI for UL grant. The WTRU may report the preferred CSI-RS configuration via higher layer signaling. The associated CSI-RS configuration may be implicitly informed by confirming that the eNB received the preferred CSI-RS configuration report. Thus, immediately after the confirmation, the WTRU may measure the CSI based on the reported preferred CSI-RS configuration. Multiple CSI-RS configurations may be measured for reporting only the preferred CSI-RS configuration.
The plurality of CSI-RS configurations are cell-specific and the CSI-RS configuration is different from the WTRU-specific CSI-RS configuration. The WTRU may measure a cell-specific CSI-RS configuration (e.g., d-BTRS) for reporting the preferred CSI-RS configuration, while the WTRU may measure a WTRU-specific CSI-RS configuration for CSI reporting to one or more transmission points. In this case, one or more of the following may be utilized:
the WTRU may report based on the cell-specific CSI-RS configuration if one or more of the following conditions are met. The previously preferred cell-specific CSI-RS configuration has a lower wideband CQI (or RSRP) than any other cell-specific CSI-RS configuration in subframe k, and the gap between the best cell-specific CSI-RS configuration and the previously preferred cell-specific CSI-RS configuration is greater than a predetermined threshold. The cell-specific CSI-RS configuration with the highest wideband CQI (or RSRP) is changed and the gap is greater than a predetermined threshold.
The WTRU may report based on the WTRU-specific CSI-RS configuration if the eNB configures a periodic CSI report or triggers an aperiodic CSI report.
In the line of sight (LoS) case, the above beam reselection may be compensated with a triggered beam updated direction of arrival. The eNB may decide and change the beam for the WTRU based on the qualified triggering event. This case is only suitable for the LoS case and low mobility.
The eNB may detect a direction of arrival (DoA) from each WTRU in both azimuth and elevation. Once the measured DoA change from the WTRU reaches a threshold, the eNB may adjust the WTRU to a new direction-based definition code vertical beam.
Fig. 14 is an exemplary method for receiving a receive vertical beam. A wireless transmit/receive unit (WTRU)1401 may receive 1403 a broadcast message from an evolved node b (enb)1402, the message including information associated with a plurality of vertical beams, wherein the information includes at least one set of physical random access control channel (PRACH) resources associated with each of the plurality of vertical beams. The WTRU 1401 may measure 1404 a reference signal transmitted on each of a plurality of vertical beams to select a receive vertical beam. The WTRU 1401 may transmit 1405 the PRACH preamble in a set of resources associated with the selected receive vertical beam. The WTRU 1401 may receive 1406 communications from the eNB 1402 using the selected receive vertical beam.
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