WO2020222896A1

WO2020222896A1 - Methods and apparatus for resource pool switching and pilot adaptation

Info

Publication number: WO2020222896A1
Application number: PCT/US2020/019585
Authority: WO
Inventors: Majid GHANBARINEJAD; Philippe Sartori
Original assignee: Futurewei Technologies, Inc.
Priority date: 2019-05-02
Filing date: 2020-02-25
Publication date: 2020-11-05

Abstract

A method includes indicating a first resource pool (RP) associated with a first physical sidelink shared channel (PSSCH); transmitting, to a second device, signals on the first PSSCH in the first RP; receiving, from the second device, a RP switch request including an indication of a second RP; and transmitting, to the second device, signals on a second PSSCH in the second RP.

Description

Methods and Apparatus for Resource Pool Switching and

Pilot Adaptation

This application claims the benefit of U.S. Provisional Application No. 62/842,274, filed on May 2, 2019, entitled "System and Method for Resource Pool Switching and Pilot Adaptation," which application is hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to methods and apparatus for digital communications, and, in particular embodiments, to methods and apparatus for resource pool (RP) switching and pilot adaptation.a

BACKGROUND

It is expected that vehicle-to-eveiything (V2X) communications will play an essential role in the evolution of the automotive industry in the near future and revolutionize the field. Dedicated short-range communication (DSRC) by IEEE and the long-term evolution - vehicular (LTE-V) developed by 3GPP are two major vehicular communication technologies developed thus far.

The third generation partnership project (3GPP) has also approved a work item for the standardization of the fifth generation (5G) new radio access technology (NR) V2X wireless communication with the goal of providing sG-compatible high-speed reliable connectivity for vehicular communications in the near future for applications such as safety systems and autonomous driving. High data rates, low latencies and high reliabilities are some of the key areas that are being investigated and standardized.

For the purpose of sidelink (SL) communications, the notion of resource pools (RPs) was introduced for the long-term evolution (LTE) SL, and is being largely reused for discussions for NR V2X. In addition, adaptation of pilots, referred to as demodulation reference signals (DMRS), where the density of pilots in the time-frequency grid of an orthogonal frequency-division multiplexing (OFDM) is adapted to channel conditions such as Doppler spread has been discussed.

SUMMARY

According to a first aspect, a method is provided. The method comprising: indicating, by a first device, a first resource pool (RP) associated with a first physical sidelink shared channel (PSSCH); transmitting, by the first device, to a second device, signals on the first PSSCH in the first RP; receiving, by the first device, from the second device, a RP switch request including an indication of a second RP; and transmitting, by the first device, to the second device, signals on a second PSSCH in the second RP.

In a first implementation form of the method according to the first aspect as such, further comprising receiving, by the first device, from an access node, scheduling information for the first PSSCH.

In a second implementation form of the method according to the first aspect as such or any preceding implementation form of the first aspect, the RP switch request being signaled in a sidelink control information (SCI) message.

In a third implementation form of the method according to the first aspect as such or any preceding implementation form of the first aspect, further comprising: transmitting, by the first device, to the access node, the RP switch request; and receiving, by the first device, from the access node, the indication of the second RP for the second PSSCH.

In a fourth implementation form of the method according to the first aspect as such or any preceding implementation form of the first aspect, further comprising transmitting, by the first device, to the second device, scheduling information for the first PSSCH.

In a fifth implementation form of the method according to the first aspect as such or any preceding implementation form of the first aspect, further comprising transmitting, by the first device, to the second device, the indication of the second RP for the second PSSCH.

In a sixth implementation form of the method according to the first aspect as such or any preceding implementation form of the first aspect, the indication of the second RP being transmitted in an SCI message.

In a seventh implementation form of the method according to the first aspect as such or any preceding implementation form of the first aspect, the signals comprising data and a sidelink demodulation reference signal (SL-DMRS).

In an eighth implementation form of the method according to the first aspect as such or any preceding implementation form of the first aspect, an indication of the first RP comprising an index associated with the first RP.

In a ninth implementation form of the method according to the first aspect as such or any preceding implementation form of the first aspect, the first device comprising a transmitting sidelink user equipment (SL UE) and the second device comprising a receiving SL UE.

In a tenth implementation form of the method according to the first aspect as such or any preceding implementation form of the first aspect, further comprising obtaining, by the first device, a RP configuration.

According to a second aspect, a method is provided. The method comprising: receiving, by a second device, from a first device, an indication of a first RP associated with a first PSSCH; receiving, by the second device, from the first device, signals on the first PSSCH in the first RP; performing, by the second device, channel measurements in accordance with the signals; and determining, by the second device, that a second RP meets a switching criteria, and based thereon transmitting, by the second device, to the first device, a RP switch request including an indication of a second RP associated with the second RP.

In a first implementation form of the method according to the second aspect as such, further comprising determining, by the second device, that the second RP meets the switching criteria, and based thereon receiving, by the second device, from the first device, signals on a second PSSCH in the second RP.

In a second implementation form of the method according to the second aspect as such or any preceding implementation form of the second aspect, further comprising receiving, by the second device, from the first device, scheduling information for the first PSSCH.

In a third implementation form of the method according to the second aspect as such or any preceding implementation form of the second aspect, further comprising receiving, by the second device, from the first device, scheduling information for the first PSSCH.

In a fourth implementation form of the method according to the second aspect as such or any preceding implementation form of the second aspect, the signals comprising data and a SL-DMRS, and performing channel measurements comprising performing channel measurements in accordance with the SL-DMRS.

In a fifth implementation form of the method according to the second aspect as such or any preceding implementation form of the second aspect, the first device comprising a transmitting SL UE and the second device comprising a receiving SL UE. In a sixth implementation form of the method according to the second aspect as such or any preceding implementation form of the second aspect, further comprising obtaining, by the second device, a RP configuration.

According to a third aspect, a first device is provided. The first device comprising: a non- transitory memory storage comprising instructions; and one or more processors in communication with the memory storage, wherein the one or more processors execute the instructions to: indicate a first RP associated with a first PSSCH; transmit, to a second device, signals on the first PSSCH in the first RP; receive, from the second device, a RP switch request including an indication of a second RP; and transmit, to the second device, signals on a second PSSCH in the second RP.

In a first implementation form of the first device according to the third aspect as such, the one or more processors further executing the instructions to receive, from an access node, scheduling information for the first PSSCH.

In a second implementation form of the first device according to the third aspect as such or any preceding implementation form of the third aspect, the RP switch request being signaled in a SCI message.

In a third implementation form of the first device according to the third aspect as such or any preceding implementation form of the third aspect, the one or more processors further executing the instructions to transmit, to the access node, the RP switch request; and receive, from the access node, the indication of the second RP for the second PSSCH.

In a fourth implementation form of the first device according to the third aspect as such or any preceding implementation form of the third aspect, the one or more processors further executing the instructions to transmit, to the second device, scheduling information for the first PSSCH.

In a fifth implementation form of the first device according to the third aspect as such or any preceding implementation form of the third aspect, the one or more processors further executing the instructions to transmit, to the second device, the indication of the second RP for the second PSSCH.

In a sixth implementation form of the first device according to the third aspect as such or any preceding implementation form of the third aspect, the indication of the second RP being transmitted in an SCI message. In a seventh implementation form of the first device according to the third aspect as such or any preceding implementation form of the third aspect, the signals comprising data and a SL-DMRS.

In an eighth implementation form of the first device according to the third aspect as such or any preceding implementation form of the third aspect, an indication of the first RP comprising an index associated with the first RP.

In a ninth implementation form of the first device according to the third aspect as such or any preceding implementation form of the third aspect, the first device comprising a transmitting SL UE and the second device comprising a receiving SL UE.

In a tenth implementation form of the first device according to the third aspect as such or any preceding implementation form of the third aspect, the one or more processors further executing the instructions to obtain a RP configuration.

According to a fourth aspect, a first device is provided. The first device comprising: a non-transitoiy memory storage comprising instructions; and one or more processors in communication with the memory storage, wherein the one or more processors execute the instructions to: receive, from a second device, an indication of a first RP associated with a first PSSCH; receive, from the second device, signals on the first PSSCH in the first RP; perform channel measurements in accordance with the signals; and determine that a second RP meets a switching criteria, and based thereon transmitting, to the second device, a RP switch request including an indication of a second RP associated with the second RP.

In a first implementation form of the first device according to the fourth aspect as such, the one or more processors further executing the instructions to determine that the second RP meets the switching criteria, and based thereon receive, from the second device, signals on a second PSSCH in the second RP.

In a second implementation form of the first device according to the fourth aspect as such or any preceding implementation form of the fourth aspect, the one or more processors further executing the instructions to receive, from the second device, scheduling information for the first PSSCH.

In a third implementation form of the first device according to the fourth aspect as such or any preceding implementation form of the fourth aspect, the one or more processors further executing the instructions to receive, from the second device, scheduling information for the first PSSCH.

In a fourth implementation form of the first device according to the fourth aspect as such or any preceding implementation form of the fourth aspect, the signals comprising data and a SL-DMRS, and performing channel measurements comprising performing channel measurements in accordance with the SL-DMRS.

In a fifth implementation form of the first device according to the fourth aspect as such or any preceding implementation form of the fourth aspect, the second device comprising a transmitting SL UE and the first device comprising a receiving SL UE.

In a sixth implementation form of the first device according to the fourth aspect as such or any preceding implementation form of the fourth aspect, the one or more processors further executing the instructions to obtain a RP configuration.

An advantage of a preferred embodiment is that resources (such as RPs or SL-DMRS configurations) can be adapted to meet channel conditions. Adaptation of resources enables performance optimization based on changing environmental condition, potentially resulting in improved communications performance.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

Figure l illustrates an example communications system;

Figures 2A-2B illustrate diagrams of example Type-A front-loaded DMRSs with 2 additional DMRSs;

Figure 3 illustrates a diagram of example Type-B front-loaded DMRSs with 2 additional DMRSs;

Figures 4A-4B illustrate diagrams of type-i and type-2 DMRS patterns in NR Rel-15; Figure 5 illustrates a communications system highlighting dual mobility; Figure 6A illustrates a flow diagram of example operations occurring in an access node participating in SL communications and resource switching according to example embodiments presented herein;

Figure 6B illustrates a flow diagram of example operations occurring in TxUE participating in SL communications and resource switching according to example embodiments presented herein;

Figure 6C illustrates a flow diagram of example operations occurring in RxUE participating in SL communications and resource switching according to example embodiments presented herein;

Figure 7A illustrates a flow diagram of example operations occurring in an access node participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs according to example embodiments presented herein;

Figure 7B illustrates a flow diagram of example operations occurring in a TxUE participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs according to example embodiments presented herein;

Figure 7C illustrates a flow diagram of example operations occurring in a RxUE participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs according to example embodiments presented herein;

Figure 8A illustrates a flow diagram of example operations occurring in a TxUE participating in SL communications and resource switching, with the SL UEs operating in mode 2 according to example embodiments presented herein;

Figure 8B illustrates a flow diagram of example operations occurring in a RxUE participating in SL communications and resource switching, with the SL UEs operating in mode 2 according to example embodiments presented herein;

Figure 9A illustrates a flow diagram of example operations occurring in an access node participating in SL communications and resource switching where a RP or attribute is selected by the access node according to example embodiments presented herein; Figure 9B illustrates a flow diagram of example operations occurring in TxUE participating in SL communications and resource switching, where a RP or attribute is selected by the access node according to example embodiments presented herein;

Figure 9C illustrates a flow diagram of example operations occurring in RxUE participating in SL communications and resource switching, where a RP or attribute is selected by the access node according to example embodiments presented herein;

Figure 10A illustrates a flow diagram of example operations occurring in an access node participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs, where a RP or attribute is selected by the TxUE according to example embodiments presented herein;

Figure 10B illustrates a flow diagram of example operations occurring in a TxUE participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs, where a RP or attribute is selected by the TxUE according to example embodiments presented herein;

Figure 10C illustrates a flow diagram of example operations occurring in a RxUE participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs, where a RP or attribute is selected by the TxUE according to example embodiments presented herein;

Figure 11A illustrates a flow diagram of example operations occurring in a TxUE participating in SL communications and resource switching, with the SL UEs operating in mode 2, where a RP or attribute is selected by the TxUE according to example embodiments presented herein;

Figure 11B illustrates a flow diagram of example operations occurring in a RxUE participating in SL communications and resource switching, with the SL UEs operating in mode 2, where a RP or attribute is selected by the TxUE according to example embodiments presented herein;

Figure 12A illustrates a flow diagram of generalized example operations occurring in an access node participating in SL communications and resource switching according to example embodiments presented herein; Figure 12B illustrates a flow diagram of generalized example operations occurring in TxUE participating in SL communications and resource switching according to example embodiments presented herein;

Figure 12C illustrates a flow diagram of generalized example operations occurring in RxUE participating in SL communications and resource switching according to example embodiments presented herein;

Figure 13A illustrates a flow diagram of generalized example operations occurring in an access node participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the

communication between the SL UEs according to example embodiments presented herein;

Figure 13B illustrates a flow diagram of example operations occurring in a TxUE participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs according to example embodiments presented herein;

Figure 13C illustrates a flow diagram of generalized example operations occurring in a RxUE participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the

Figure 14A illustrates a flow diagram of generalized example operations occurring in a TxUE participating in SL communications and resource switching, with the SL UEs operating in mode 2 according to example embodiments presented herein;

Figure 14B illustrates a flow diagram of example operations occurring in a RxUE participating in SL communications and resource switching, with the SL UEs operating in mode 2 according to example embodiments presented herein;

Figure 15 illustrates an example communication system according to example embodiments presented herein;

Figures 16A and 16 B illustrate example devices that may implement the methods and teachings according to this disclosure; Figure 17 is a block diagram of a computing system that may be used for implementing the devices and methods disclosed herein;

Figure 18 illustrates a block diagram of an embodiment processing system for performing methods described herein, which may be installed in a host device; and

Figure 19 illustrates a block diagram of a transceiver adapted to transmit and receive signaling over a telecommunications network according to example embodiments presented herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The structure and use of disclosed embodiments are discussed in detail below. It should be appreciated, however, that the present disclosure provides many applicable concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific structure and use of embodiments, and do not limit the scope of the disclosure.

Figure 1 illustrates an example communications system too. Communications system too includes an access node 105 serving user equipments (UEs), such as UEs 110, 112,

114, 116, and 118. In a first operating mode, communications to and from a UE passes through access node 105. In a second operating mode, communications to and from a UE do not pass through access node 105, however, access node 105 typically allocates resources used by the UE to communicate when specific conditions are met. Access nodes may also be commonly referred to as Node Bs, evolved Node Bs (eNBs), next generation (NG) Node Bs (gNBs), master eNBs (MeNBs), secondary eNBs (SeNBs), master gNBs (MgNBs), secondary gNBs (SgNBs), network controllers, control nodes, base stations, access points, transmission points (TPs), transmission -reception points (TRPs), cells, carriers, macro cells, femtocells, pico cells, and so on, while UEs may also be commonly referred to as mobile stations, mobiles, terminals, users, subscribers, stations, and the like. Access nodes may be fixed location devices or located in a moving vehicle, such as an automobile, plane, train, boat, etc. UEs may also be located in a moving vehicle, such as a device that is part of the moving vehicle or a device used by a user located in or on the moving vehicle.

Access nodes may provide wireless access in accordance with one or more wireless communication protocols, e.g., the Third Generation Partnership Project (3GPP) long term evolution (LTE), LTE advanced (LTE-A), 5G, 5G LTE, 5G NR, High Speed Packet Access (HSPA), the IEEE 802.11 family of standards, such as 8o2.na/b/g/n/ac/ad/ax/ay/be, etc. While it is understood that communications systems may employ multiple access nodes capable of communicating with a number of UEs, only one access node and five UEs are illustrated for simplicity.

In LTE, demodulation reference signals (DMRSs) are associated with physical sidelink shared channels (PSSCHs), physical sidelink control channels (PSCCH), physical sidelink downlink channels (PSDCH), and physical sidelink broadcast channels (PSBCH). In LTE sidelink, the DMRSs are generated in a manner similar to that of LTE physical uplink shared channels (PUSCHs), but there are some exceptions, which include:

- Different tables are used for parameters such as group/sequence hopping, cyclic shifts, number of layers and antennas ports, etc.

- The set of physical resource blocks used in the mapping process should be identical to the corresponding PSSCH/PSCCH/PSDCH/PSBCH transmission.

- The interleaved single carrier frequency division multiple access (IFDMA) index in the mapping process should be identical to that for the corresponding

PSSCH/PSCCH/PSDCH/PSBCH transmission.

- For sidelink (SL) transmission modes 3 and 4 on the PSSCH and PSCCH, the mapping shall use the orthogonal frequency division multiplexed (OFDM) symbol indices l = 2 and 1 =5 for the first slot in the subframe and l = 1 and / = 4 for the second slot in the subframe.

- For SL transmission modes 3 and 4 on the PSBCH, the mapping shall use the OFDM symbol indices l = 4 and 1 = 6 for the first slot in the subframe and l = 2 for the second slot in the subframe.

- For SL transmission modes 1 and 2, the pseudo-random sequence generator shall be initialized at the start of each slot fulfilling « _s ^SSCH = 0. For SL transmission modes 3 and 4 the pseudo-random sequence generator shall be initialized at the start of each slot fulfilling « _s ^SSCH mod 2 = 0 . Note that this parameter represents the number of the current slot in the subframe pool.

- For SL transmission modes 3 and 4 on the PSCCH, the cyclic shift to be applied for all DMRS in a subframe shall be chosen randomly from four different values.

For SL transmission modes 1 and 2 and SL discovery, the quantity m takes the values m = 0,1 and for SL transmission modes 3 and 4, the quantity m takes the values m = 0,1, 2, 3 for PSSCH and m = 0,1,2 for PSBCH. The parameter m is defined in 3GPP TS 36.211, V14.3.0.

- For SL transmission modes 3 and 4, the quantity /; equals the decimal representation of CRC on the PSCCH transmitted in the same subframe as the PSSCH according to

2^{£ 1} ' with p and L . The parameters are defined in 3GPP TS 36.211, V14.3.0.

Reference signals in NR enhanced Mobile BroadBand (eMBB) including DMRS, channel state information reference signal (CSI-RS), and phase tracking reference signal (PTRS) in the downlink, and their counterparts in the uplink are used for various purposes such as demodulation, CSI acquisition, beam management, mobility management, time/frequency/phase tracking, and so on. NR eMBB does not support a common reference signal (CRS). Therefore, the Uu link transmission scheme(s) will only be based on the DMRS. The Uu link DMRS in NR Rel-15 is UE-specifically configured.

For NR eMBB, for DMRS time (e.g., OFDM symbols) and frequency (e.g., subcarriers) patterns, 2 types (Type-i and Type-2) of DMRS configurations are introduced in NR Rel- 15. Type-i DMRS supports up to 4 orthogonal DMRS ports when 1 symbol is configured for DMRS transmission and up to 8 orthogonal DMRS ports when 2 symbols are configured. Type-2 DMRS supports up to 6 orthogonal DMRS ports when 1 symbol is configured for DMRS transmission and up to 12 orthogonal DMRS ports when 2 symbols are configured. These orthogonal DMRS ports are multiplexed in the time domain, frequency domain, and code domain (orthogonal cover code (OCC)). Both types of DMRS configurations are configurable for downlink and for uplink and they can be configured such that the DMRS for downlink and uplink are orthogonal to each other.

For NR eMBB, two 16-bit configurable DMRS scrambling identifiers (IDs) are supported. The configuration is by radio resource control (RRC) signaling, for example, and, in addition, the scrambling ID is dynamically selected and indicated by a downlink control information (DCI) message. Before RRC configuring the 16-bit DMRS scrambling IDs, the physical cell ID is used for DMRS scrambling.

For NR eMBB, when mapping to symbol locations of a physical downlink shared channel (PDSCH)/PUSCH transmission within a slot, the DMRS can be configured to be only on front-loaded (FL) symbol(s), or on additional DMRS symbol(s) as well. The additional DMRS, when present, should be the exact copy of the front-loaded DMRS for the PDSCH/PUSCH transmission, i.e., the same number of symbols, antenna ports, sequence, etc.

For NR eMBB, with the front-loaded-only DMRS, channel estimation can only rely on 1 or 2 symbols in an early part of the data transmission duration in order to speed up demodulation and reduce overall latency. However, without additional DMRS symbols to enable time domain interpretation/filtering, the channel estimation, and hence, overall performance may degrade even for scenarios with only moderate mobility.

For NR eMBB, for PDSCH/PUSCH resource mapping Type-A, the front-loaded DMRS starts from the third or fourth symbols of each slot (or each hop if frequency hopping is supported). For PDSCH/PUSCH mapping Type-B, the front-loaded DMRS starts from the first symbol of the transmission duration. The number of additional DMRSs can be l, 2, or 3 per network configuration. The location of each additional DMRS depends on the transmission duration (i.e., number of OFDM symbols) of the PDSCH/PUSCH transmission and follows a set of general rules for better channel estimation

performance. These rules allow no more than 2 OFDM symbols for PDSCH after the last DMRS, allow 2 to 4 symbols between neighboring DMRSs, and DMRSs are almost evenly distributed in time.

Figures 2A-2B illustrate diagrams of example Type-A front-loaded DMRSs with 2 additional DMRSs 200. As an example, a first Type-A front-loaded DMRS with 2 additional DMRS 210 includes a front-loaded DMRS 212 in slot #3 with 2 additional DMRSs 214 and 216 in slots #6 and #9, respectively. As another example, a second Type- A front-loaded DMRS with 2 additional DMRS 220 includes a front-loaded DMRS 222 in slot #3 with 2 additional DMRSs 224 and 226 in slots #7 and #11, respectively. As another example, a third Type-A front-loaded DMRS with 2 additional DMRS 230 includes a front-loaded DMRS 232 in slot #2 with 2 additional DMRSs 234 and 236 in slots #6 and #9, respectively. As another example, a fourth Type-A front-loaded DMRS with 2 additional DMRS 240 includes a front-loaded DMRS 242 in slot #2 with 2 additional DMRSs 244 and 246 in slots #7 and #11, respectively.

Figure 3 illustrates a diagram of example Type-B front-loaded DMRSs with 2 additional DMRSs 300. As an example, a first Type-B front-loaded DMRS with 2 additional DMRS 310 includes a front-loaded DMRS 312 in slot #0 with 2 additional DMRSs 314 and 316 in slots #3 and #6, respectively. As another example, a second Type-B front-loaded DMRS with 2 additional DMRS 320 includes a front-loaded DMRS 322 in slot #0 with 2 additional DMRSs 324 and 326 in slots #4 and #8, respectively.

For NR eMBB, the patterns and ports of additional DMRS are the same as those of front- loaded DMRS, with the number of additional DMRS and their positions being configured by RRC signaling. A maximum of 1 additional DMRS for a 2-symbol front-loaded DMRS, and a maximum of 3 additional DMRS for a l-symbol front-loaded DMRS are supported. The positions of the additional DMRS are independent of that of front-loaded DMRS, and may be determined by the actual number of symbols of the front-loaded DMRS, PDSCH/PUSCH mapping type, maximum number of additional DMRS, and

PDSCH/PUSCH duration in symbols. For PDSCH/PUSCH mapping type A, a duration in symbols is defined as the duration between the tst OFDM symbol of the slot and the last OFDM symbol of the scheduled PDSCH/PUSCH resources in the slot. For

PDSCH/PUSCH mapping type B, a duration in symbols is defined as the number of OFDM symbols of scheduled PDSCH/PUSCH resources as signaled.

NR eMBB supports 4 front-loaded DMRS patterns (2 types, each type with 1 or 2 symbols) for PDSCH/PUSCH data demodulation. The front-loaded DMRS pattern is configured by the RRC as follows:

- Configuration type 1 (supported for cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) and discrete Fourier transform spread OFDM (DFT-S- OFDM)):

- l-symbol pattern is configured with Comb 2, i.e., every second resource element (RE) is used for the DMRS pattern, and a cyclic shift of 2 different values is supported. This option supports up to 4 ports.

- 2-symbol pattern is configured with Comb 2, and a cyclic shift of 2 different values is supported. A time-domain OCC (TD-OCC) with two different values ({1 1} and {1 -1}) is also allowed over the two symbols, which increases the number of ports to up to 8 ports.

- Configuration type 2 (supported for CP-OFDM only):

- l-symbol pattern is configured with a 2-value frequency-division OCC (FD-OCC) across adjacent REs in the frequency domain, and supports up to 6 ports.

- 2-symbols pattern is also configured with a 2-value FD-OCC across adjacent REs in the frequency domain, and in addition, a 2-value TD-OCC ({1,1} and {1,- 1}) is also supported over the two symbols, increasing the number of ports to up to 12 ports.

In NR Rel-15, the access node should indicate the location and number of DMRS symbols to the UE for proper processing by the UE. This indication is performed at two stages by RRC signaling and DCI signaling. First, a maximum of 1 or 2 symbols for front-loaded DMRS is configured by RRC signaling for PUSCH or PDSCH. Then, the actual number for each instance is indicated by a DCI through an index to a table if a maximum of 2 symbols is configured for front-loaded DMRS. The configurations described above are typically applied to 14 -symbol slots. Additionally, for 2/4/ 7-symbol non-slot based scheduling, type 1 and type 2 are both supported as follows: for 2/4-symbol transmissions, only l-symbol front-loaded DMRS is supported; and for 7-symbol, both 1- or 2-symbol front-loaded DMRS are supported.

Figures 4A-4B illustrate diagrams of type-i and type-2 DMRS patterns in NR Rel-15. Diagram 400 of Figure 4A illustrates DMRS configuration type 1 single symbol front- loaded DMRS pattern 405 and double symbol front -loaded DMRS pattern 410. Diagram 450 of Figure 4B illustrates DMRS configuration type 2 single symbol front-loaded DMRS pattern 455 and double symbol front-loaded DMRS pattern 460.

On the maximum number of orthogonal DMRS ports, the following apply for UL/DL CP- OFDM. For single-user multiple-input multiple-output (SU-MIMO), a maximum of 8 orthogonal DMRS ports are supported for downlink and a maximum of 4 orthogonal DMRS ports are supported for uplink as follows:

- For the downlink with Type 1, 4 ports for l-symbol DMRS and 8 ports for 2- symbol DMRS are supported per UE.

- For the downlink with Type 2, 6 ports for l-symbol DMRS and 8 ports for 2-symbol DMRS are supported per UE.

- For the uplink with Type 1 or Type 2, 4 ports for l-symbol or 2-symbol DMRS are supported per UE.

For multiuser multiple-input multiple-output (MU-MIMO), a maximum of 12 orthogonal DMRS ports are supported for both downlink and uplink as follows:

- For Type 1, 2 ports for l-symbol or 2-symbol are supported.

- For Type 2, 4 ports for l-symbol or 2-symbol are supported.

For DFT-s-OFDM, only rank-i is supported from UE perspective.

Table 1 summarizes the number of ports supported for different cases.

Table l: Summary of ports supported.

In order to achieve high spectrum efficiency, MU-MIMO transmission and reception has to adapt dynamically to channel conditions, UE distribution, data traffic, and so on. Dynamic adaptation implies that the number of MIMO layers and the occupied DMRS ports for the paired UEs vary with time (from transmission to transmission, for example) and frequency (from resource block group (RBG) to RBG, for example). More transmission layers may provide higher throughput at the cost of increased DMRS overhead.

In NR Rel-15, in addition to the DMRS ports used for data transmission (PDSCH or PUSCH) of the intended UE, a DCI also indicates the number of DMRS code division multiplexing (CDM) group(s) that are without data mapped to their corresponding REs. These DMRS CDM groups include the CDM group(s) of the UE’s DMRS ports, and in addition, the DMRS CDM groups may include CDM group(s) that may be for other UEs’ DMRS ports. Therefore, this signal can be used to indicate MU-MIMO transmission and dynamically adjust the associated overhead. For the downlink (and in a sense, the uplink as well), this mode of operation falls between transparent MU-MIMO where the UE has no knowledge of the paired UE(s) in terms of their used DMRS ports, and the non transparent MU-MIMO where the UE knows exactly which DMRS ports are used for other UE(s). As mentioned previously, when the access node is scheduling a data/ shared channel for a UE in the downlink or uplink, the access node can indicate to the UE, through DCI signaling, information on a DMRS transmission. Multiple tables are defined by the specification 3GPP TS 38.212, V15.4.0, which is hereby incorporated herein by reference in its entirety, for indication of information such as the CDM groups, the number of ports, and the number of symbols for the front -loaded DMRS. If there are additional DMRSs, similar values for the parameters apply to the additional DMRS as well.

Details of the DCI indications are as follows: For the uplink or downlink DMRS port indication for CP-OFDM and DFT-s-OFDM, multiple tables are defined by the standard specification for DMRS configuration Type 1 and Type 2 with a maximum 1 or 2 symbols for the front -loaded DMRS. The scheduled DMRS ports are indicated in the DCI. The actual number of front-loaded DMRS symbols is indicated in the DCI when the maximum number of symbols for the front-loaded DMRS is configured as 2. NR supports rate-matching of DMRS by the parameter "number of CDM groups without data" indicated in the DCI; values of "t", "2", or "3" for this parameter correspond to CDM group o, {0,1}, or {0,1,2}, respectively.

A UE in the MU-MIMO mode should first be scheduled with ports within a specific CDM group, and then across CDM groups (for a single TRP). The ports within the same CDM group should be quasi-collocated (QCL’ed), meaning that they should be transmitted by antennas and pass through channels that show similar large-scale properties. In practice, that may mean that the QCL’ed ports are implemented on a same physical antenna.

NR Rel-15 does not support multiuser configurations between UEs with different DMRS configurations with respect to the actual number of front-loaded DMRS symbols, the number of additional DMRS symbols, DMRS symbol location(s), and the DMRS configuration type. That simplifies the design of the receiver as the receiver only combines measurements with tightly similar configurations of DMRS for the purpose of demodulating signals from multiple UEs.

As related to PUSCH transmission, DMRS port indication is further determined by the rank associated with the PUSCH.

SL communication, especially for V2X applications, may experience dual mobility when both ends of a communication link may be mobile, such as when two mobile UEs are communicating. Figure 5 illustrates a communications system 500 highlighting dual mobility. Communications system 500 includes a roadside unit (RSU) 505

communicating with a first UE (UEt) 510. Communications between RSU 505 and first UE 510 may occur in a cellular-like manner, where RSU 505 controls communications to and from first UE 510. Communications system 500 also includes a second UE (UE2) 515 and a third UE (UE3) 520. Both second UE 515 and third UE 520 are communicating with first UE 510, using SL communication, for example.

First UE 510 is moving in an upward direction at velocity Vi (shown as vector 512), second UE 515 is also moving in an upward direction at velocity V2 (shown as vector 517), while third UE 520 is moving in a downward direction at velocity V3 (shown as vector 522.

Dashed lines represent the Doppler shift present in a communication link. As an example, for the communication link between RSU 505 and first UE 510, a Doppler shift 513 is proportional to the speed of first UE 510 because RSU 505 is immobile. However, the Doppler shift on a SL communication channel may be proportional to the sum of the speeds of the two UEs. As an example, Doppler shift 518 (for the communication link between first UE 510 and second UE 515) is proportional to a difference between the speed of the two UEs because the two UEs are moving in the same direction. As another example, Doppler shift 523 (for the communication link between first UE 510 and third UE 520) is proportional to a sum of the speed of the two UEs because the two UEs are moving in opposite directions. In practice, the dual mobility effect in V2X SL scenarios allows the Doppler shift on a SL channel to vary in the range of o to up to twice the speed of the fastest moving UEs, which leads to a wide range of Doppler frequencies (and hence, coherence times).

In V2X sidelink communication scenarios, there may not always be a central controller similar to an access node to collect channel state indicator (CSI) information and unilaterally decide what density of SL-DMRS is needed for what communication. As a result, there is a need for mechanisms in place for UEs on the SL to adapt their density of the SL-DMRS.

As mentioned previously, SL communications are performed on pools of time-frequency resources referred to as resource pools (RPs). A resource pool (RP) can be configured as a plurality of time-frequency resources indicated by time resources such as slots and frequency resources such as resource blocks (RBs), which may be repeated periodically over time, follow a pseudo-random pattern, and so on. The notion of RPs was introduced in LTE and is reused in NR V2X. Because a RP can be used by multiple UEs, it is desired that the frame structure and other attributes are determined and known to the UEs to large extent for the sake of design simplicity.

However, there are cases when UEs communicating on a RP need to make changes to frame structure attributes. An example is adaptation of SL-DMRS density, which requires changing the OFDM symbols on which SL-DMRS are transmitted. The UEs should know the resource used for SL-DMRS transmission in a slot, and it is desired to maintain such attributes of a frame structure in a RP. Therefore, there is a need for a mechanism for UEs on a SL to switch communications from one RP to another RP that possesses the demanded frame structure attribute such as SL-DMRS density.

Furthermore, RP switching may be used for purposes such as load balancing and so on.

According to an example embodiment, methods and apparatus for RP switching are provided. In some embodiments, emphasis is placed on RP switching for SL-DMRS adaptation. However, the methods and apparatus may be extended to RP switching for other reasons, such as changes in frame structure attributes. The example embodiments are discussed within the framework of the SL-DMRS.

However, the example embodiments are applicable to other types of reference signals, such as channel state information reference signals (CSI-RSs), sounding reference signals (SRSs), phase tracking reference signals (PTRSs), or other reference signals with similar or different functionalities or terminologies.

Furthermore, some embodiments are described with emphasis placed on unicast communications. But the example embodiments are also operable with groupcast or other types of SL communications.

In an embodiment, the methods and apparatus in the present disclosure comprise transmitting and receiving signals between UEs, as well as between a UE and a network entity such as an access node. The signaling may be originated and/or processed at different layers such as the radio resource control (RRC) layer, medium access control (MAC) layer, or the physical (PHY) layer. PHY layer signaling, as described in the present disclosure, may comprise a downlink control information message (DCI), a sidelink control information message (SCI), a sidelink feedback control information message (SFCI), or a like, as appropriate.

For example, in a mode t communication, a PHY layer signaling may refer to a DCI on a physical downlink control channel (PDCCH) from an access node to a transmitting UE (TxUE) and/or a receiving UE (RxUE). Alternatively, PHY layer signaling may refer to an SCI on a physical sidelink control channel (PSCCH) from a TxUE to an RxUE. In any mode of SL communication, PHY control signaling from an RxUE back to a TxUE (such as acknowledgement/negative-acknowledgement (ACK/NACK), CSI feedback, etc.) may refer to an SFCI on a physical sidelink feedback channel (PSFCH).

Additionally, as used herein, a configuration may refer to a configuration by a higher layer entity, for example, the RRC, or it may refer to a pre-configuration. In this disclosure, this is denoted as (pre)configuration.

According to an example embodiment, SL UEs acquire the channel condition (e.g., channel quality measurements) and select a resource (such as a RP or a SL-DMRS configuration) that satisfies the channel condition.

In an embodiment, the SL UEs obtain SL-DMRS configurations allowing different patterns and densities including in the time domain. Each configuration may be received by RRC signaling from the network (such as a network entity (including an access node, a controller, or network function), or a database) or from another SL UE, or it may be obtained by a preconfiguration.

The SL UEs also obtain RP configurations. Each RP comprises a set of time and frequency resources and can be associated, by configuration or control signaling, for example, with other configurations such as SL-DMRS configurations. For example, a resource pool RPi can be associated with a certain SL-DMRS configuration Di, and another resource pool RP2 can be associated with another SL-DMRS configuration D2, etc. The SL-DMRS configuration may be unique for a given RP, or there may be multiple SL-DMRS configurations associated with a given RP.

The SL UEs use the RPs and the SL-DMRS configurations, as well as other signaling such as activation/deactivation and indication messages, for communications on the SL.

In an embodiment, in order to adapt the SL-DMRS to channel conditions, transmitting UEs (TxUEs) acquire CSI by performing measurements on reference signals, and/or use feedback from receiving UEs (RxUEs). In order to assist with SL-DMRS adaptation, receiving UEs (RxUEs) acquire CSI by performing measurements on reference signals and send feedback to transmitting UEs (TxUEs), for example.

TxUEs and/or RxUEs can then use the measurement results and/or feedback information to select a resource pool that is associated with a SL-DMRS configuration that satisfies the current channel conditions. For example, in the case that the channel, as assessed by a SL UE, requires a higher or lower density of SL-DMRS, the SL UE can perform signaling with a peer SL UE to switch to a RP that is associated with a SL-DMRS configuration that allows a higher or lower density, respectively.

In mode t communication, the SL UE obtains RP (pre)configurations associated with SL- DMRS (pre)configurations. The SL-DMRS configurations, for example from RRC signaling, may or may not include a value for SL-DMRS density (e.g., a number of additional SL-DMRS per slot). If a value for such a parameter is determined, the SL UE can retain the value for as long as the configuration is valid or until the value is overridden by any following signaling, such as from RRC or MAC signaling.

Furthermore, independent of whether the value is or is not determined by RRC or MAC signaling, a DCI message may determine an RP or a value for the SL-DMRS density parameter when scheduling a transmission. Because DCI signaling may not be as reliable as RRC or MAC signaling due to lack of acknowledgement, DCI signaling is more suitable for one-time/aperiodic indication of RP or SL-DMRS density, for example per PSSCH. In some embodiments, RP switching or SL-DMRS indication information in the DCI may be communicated by an SCI as well. In alternative embodiments, RP switching or SL- DMRS indication is not communicated by a DCI, but only an SCI by the transmitting UE determining RP or SL-DMRS for an upcoming PSSCH.

In mode 2 communication, the SL UE obtains RP (pre) configurations associated with SL- DMRS (pre)configurations. The SL UE obtains the RP (pre)configurations through signaling, for example. As another example, the RP (pre)configurations are specified by a technical standard or an operator of the communications system. In such a situation, the RP (pre)configurations may be stored in a memory of the SL UE, provided in an initial attachment procedure or programmed in the memory during manufacture, for example. The SL-DMRS configurations, for example from RRC signaling, may or may not include a value for SL-DMRS density (e.g., a number of additional DMRS per slot). If a value for such a parameter is determined, the SL UE can retain the value for as long as the configuration is valid or until the value is overridden by any following signaling, such as from RRC or MAC signaling. Furthermore, independent of whether the value is or is not determined by RRC or MAC signaling, an SCI message may determine an RP or a value for the SL-DMRS density parameter when scheduling a transmission. Because SCI signaling may not be as reliable as RRC or MAC signaling due to lack of

acknowledgement, SCI signaling is more suitable for one-time/ aperiodic indication of RP or SL-DMRS density, for example per PSSCH.

Figure 6A illustrates a flow diagram of example operations 6oo occurring in an access node participating in SL communications and resource switching. Operations 6oo may be indicative of operations occurring in an access node as the access node participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching.

Operations 6oo begin with the access node sending RP configurations and associated SL- DMRS configurations (block 605). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D ,, D₂, ..., D_N} maybe sent to the SL UEs. In an embodiment, each RP may be associated with a SL-DMRS configuration or, alternatively, each RP may be associated with multiple SL-DMRS configurations. In which case, further signaling may be used for indication of a SL-DMRS configuration for a transmission in the RP. Each SL-DMRS configuration may include information on SL- DMRS sequence generation, density and patterns in time and frequency domains, number of ports, quasi-collocation (QCL) information, and so on. Each RP or SL-DMRS configuration may be associated with UEs in a cell, a specific UE or a group of UEs, one or multiple connections, and so on. Additional details are provided below. The configuration may be sent using, e.g., RRC signaling (dedicated or common) from the access node, or by PC5 RRC signaling. Alternatively, the configuration could be pre configured.

The access node transmits an indication of a particular RP (RPi) for a next

communication between SL UEs (block 607). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by a TxUE, intended for a RxUE, for example. The access node transmits scheduling information for the next communication between SL UEs (block 609). The scheduling information includes information such as resources in RP, transmission mode, modulation and coding scheme (MCS), and so forth. The scheduling information may be transmitted in a DCI message. The RP configurations and associated SL-DMRS configurations, the scheduling information, and the indication may be transmitted in one or more messages. As an example, the RP configurations and associated SL-DMRS configurations may be sent in a first message corresponding to operations associated with block 605. As an example, the indication may be transmitted in a second message corresponding to operations associated with block 607, while the scheduling information may be transmitted in a third message corresponding to operations associated with block 609. As another example, the RP configurations and associated SL-DMRS

configurations, the indication, and the scheduling information may be transmitted in a single message corresponding to operations associated with blocks 605-609. Other combinations of transmitting the RP configurations and associated SL-DMRS configurations, the scheduling information, and the indication are possible.

The access node performs a check to determine if a request requesting the selection of a different resource is received (block 611). The access node may receive control signaling, such as an uplink control information (UCI) including an ACK/NACK. The control signaling may include the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information maybe received from the TxUE or the RxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

If the access node has received the request requesting the selection of the different resource, the access node transmits an indication of the different resource (block 613). If the request specified a RP RPj, the access node may transmit the indication of the specified RP RPj. If the request specified a SL-DMRS configuration Dj, the access node may transmit the indication of the RP associated with the SL-DMRS configuration Dj, RPj. The access node may or may not allow the RP switch. The RP switch may be rejected for a variety of reasons, including too many SL communications are already using the requested RP, historic RP communications performance, ACK/NACK rate for the RP, and so on.

Figure 6B illustrates a flow diagram of example operations 620 occurring in TxUE participating in SL communications and resource switching. Operations 620 may be indicative of operations occurring in a TxUE as the TxUE participates in SL

communications and resource (e.g., RP or SL-DMRS configuration) switching.

Operations 620 begin with the TxUE receiving RP configurations and associated SL- DMRS configurations (block 625). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D , D₂, ..., DN} maybe received from an access node. In an embodiment, each RP may be associated with a SL-DMRS configuration or, alternatively, each RP may be associated with multiple SL-DMRS configurations. In which case, further signaling may be used for indication of a SL-DMRS configuration for a transmission in the RP. Each SL-DMRS configuration may include information on SL- DMRS sequence generation, density and patterns in time and frequency domains, number of ports, QCL information, and so on. Each RP or SL-DMRS configuration may be associated with UEs in a cell, a specific UE or a group of UEs, one or multiple connections, and so on. Additional details are provided below. The configuration may be sent using, e.g., RRC signaling (dedicated or common) from the access node, or by PC5 RRC signaling. Alternatively, the configuration could be pre-configured.

The TxUE receives an indication of a particular RP (RPi) for a next communication (block 627). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by the TxUE, intended for a RxUE, for example. The TxUE receives scheduling information for the next communication between SL UEs (block 629). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a DCI message. The RP configurations and associated SL-DMRS configurations, the scheduling information, and the indication may be received in one or more messages. As an example, the RP configurations and associated SL-DMRS configurations may be received in a first message corresponding to operations associated with block 625. As an example, the indication may be received in a second message corresponding to operations associated with block 627, while the scheduling information may be received in a third message corresponding to operations associated with block 629. As another example, the RP configurations and associated SL- DMRS configurations, the indication, and the scheduling information may be received in a single message corresponding to operations associated with blocks 625-629. Other combinations of receiving the RP configurations and associated SL-DMRS

configurations, the scheduling information, and the indication are possible.

The TxUE transmits data and SL-DMRS in the particular RP (block 631). The transmission is transmitted in accordance with the SL-DMRS configuration. The TxUE may receive control signaling, such as a SCI including an ACK/NACK, CSI, etc. The TxUE performs a check to determine if control signaling has been received (block 633). The control signaling may include the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be received from the RxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

If the TxUE has received the request requesting the selection of the different resource, the TxUE transmits another request requesting the selection of the different resource (block 635). The request requesting the selection of the different resource is transmitted to the access node, for example. The request requesting the selection of the different resource may be transmitted in an UCI. The request requesting the selection of the different resource may be a different request received by the TxUE in block 633 or the request requesting the selection of the different resource may be the request received by the TxUE in block 633 that is forwarded to the access node.

The TxUE may return to block 627 to receive an indication of the different resource and the operations 620 may continue as described above, but for the different resource.

Figure 6C illustrates a flow diagram of example operations 640 occurring in RxUE participating in SL communications and resource switching. Operations 640 may be indicative of operations occurring in a RxUE as the RxUE participates in SL

communications and resource (e.g., RP or SL-DMRS configuration) switching.

Operations 640 begin with the RxUE receiving RP configurations and associated SL- DMRS configurations (block 645). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D , D₂, ..., DN} maybe received from an access node. In an embodiment, each RP may be associated with a SL-DMRS configuration or, alternatively, each RP may be associated with multiple SL-DMRS configurations. In which case, further signaling may be used for indication of a SL-DMRS configuration for a transmission in the RP. Each SL-DMRS configuration may include information on SL- DMRS sequence generation, density and patterns in time and frequency domains, number of ports, QCL information, and so on. Each RP or SL-DMRS configuration may be associated with UEs in a cell, a specific UE or a group of UEs, one or multiple connections, and so on. Additional details are provided below. The configuration may be sent using, e.g., RRC signaling (dedicated or common) from the access node, or by PC5 RRC signaling. Alternatively, the configuration could be pre-configured.

The RxUE receives an indication of a particular RP (RPi) for a next communication (block 647). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by a TxUE, intended for the RxUE, for example. The RxUE receives scheduling information for the next communication between SL UEs (block 649). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a DCI message. The RP configurations and associated SL-DMRS configurations, the scheduling information, and the indication may be received in one or more messages. As an example, the RP configurations and associated SL-DMRS configurations may be received in a first message corresponding to operations associated with block 645. As an example, the indication may be received in a second message corresponding to operations associated with block 647, while the scheduling information may be received in a third message corresponding to operations associated with block 649. As another example, the RP configurations and associated SL- DMRS configurations, the indication, and the scheduling information may be received in a single message corresponding to operations associated with blocks 645-649. Other combinations of receiving the RP configurations and associated SL-DMRS

configurations, the scheduling information, and the indication are possible.

The RxUE receives data and SL-DMRS in the particular RP (block 651). The transmission is transmitted in accordance with the SL-DMRS configuration. The RxUE performs channel measurements (block 653). The channel measurements maybe performed in accordance with the SL-DMRS received from the TxUE, for example. The channel measurements may be signal plus interference to noise ratio (SINR) measurements, signal to noise ratio (SNR) measurements, reference signal received power (RSRP) measurements, reference signal received quality (RSRQ) measurements, received signal power measurements, etc.

The RxUE performs a check to determine if there is a different resource that is more suitably meets the channel measurements (block 655). As an example, the RxUE may determine that alternate resources are needed to meet data rate requirements with the channel measurements as determined in block 653, or that a different SL-DMRS configuration (with higher or lower SL-DMRS density) is needed to allow for adequate channel measurements. Alternatively, the RxUE may determine that the current SL- DMRS configuration with a higher or lower SL-DMRS density is more suitable. The RxUE identifies the resource (e.g., a different RP RPj or SL-DMRS configuration Dj) if one exists. If there are multiple resources, then the RxUE may randomly select a resource or use historical information (previous performance results using the resources, traffic on the resources, etc.) to select a resource, for example. The RxUE transmits control signaling, such as a SCI including an ACK/NACK, CSI, etc. (block 657). The control signaling includes the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information maybe transmitted to the TxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs. In an embodiment, the control information is transmitted directly to the access node, in an UCI, for example. In an embodiment, the control information is transmitted to both the TxUE and the access node.

The RxUE may return to block 647 to receive an indication of the different resource and the operations 640 may continue as described above, but for the different resource.

In an embodiment, in mode 1 communication, the TxUE selects the resource used for the communication between the SL UEs. In such a situation, the access node does not select the resource for the communication between the SL UEs. However, because of the mode 1 communication, the access node still provides scheduling information for the communication between the SL UEs.

Figure 7A illustrates a flow diagram of example operations 700 occurring in an access node participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the

communication between the SL UEs. Operations 700 may be indicative of operations occurring in an access node as the access node participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching.

Operations 700 begin with the access node sending RP configurations and associated SL- DMRS configurations (block 705). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D ,, D₂, ..., D_N} maybe sent to the SL UEs. The access node transmits scheduling information for the next communication between SL UEs (block 707). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information maybe transmitted in a DCI message. The RP configurations and associated SL-DMRS configurations, and the indication may be transmitted in one or more messages. As an example, the RP configurations and associated SL-DMRS configurations may be sent in a first message corresponding to operations associated with block 705. As an example, the scheduling information may be transmitted in a second message corresponding to operations associated with block 707. As another example, the RP configurations and associated SL-DMRS configurations, the scheduling information may be transmitted in a single message corresponding to operations associated with blocks 705-707. Other combinations of transmitting the RP configurations and associated SL-DMRS configurations, and the scheduling information are possible.

Figure 7B illustrates a flow diagram of example operations 720 occurring in a TxUE participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs. Operations 720 may be indicative of operations occurring in a TxUE as the TxUE participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching.

Operations 720 begin with the TxUE receiving RP configurations and associated SL- DMRS configurations (block 725). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D ,, D₂, ..., D_N} maybe received from an access node. The TxUE transmits an indication of a particular RP (RPi) for a next

communication (block 727). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by the TxUE, intended for a RxUE, for example. The TxUE receives scheduling information for the next communication between SL UEs (block 729). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a DCI message. The RP configurations and associated SL-DMRS configurations, and the scheduling information may be received in one or more messages. As an example, the RP configurations and associated SL-DMRS configurations may be received in a first message corresponding to operations associated with block 725. As an example, the scheduling information may be received in a second message corresponding to operations associated with block 729. As another example, the RP configurations and associated SL-DMRS configurations, and the scheduling information may be received in a single message corresponding to operations associated with blocks 725 & 729. Other combinations of receiving the RP configurations and associated SL-DMRS configurations, and the scheduling information are possible.

The TxUE transmits data and SL-DMRS in the particular RP (block 731). The transmission is transmitted in accordance with the SL-DMRS configuration. The TxUE may receive control signaling, such as a SCI including an ACK/NACK, CSI, etc. The TxUE performs a check to determine if control signaling has been received (block 733). The control signaling may include the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be received from the RxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

If the TxUE has received the request requesting the selection of the different resource, the TxUE transmits an indication of the different resource (block 735). Operations 720 may continue as described above, but for the different resource. If the TxUE has not received the request requesting the selection of the different resource, operations 720 terminate.

Figure 7C illustrates a flow diagram of example operations 740 occurring in a RxUE participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs. Operations 740 may be indicative of operations occurring in a RxUE as the RxUE participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching.

Operations 740 begin with the RxUE receiving RP configurations and associated SL- DMRS configurations (block 745). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D ,, D₂, ..., D_N} maybe received from an access node. The RxUE receives an indication of a particular RP (RPi) for a next communication (block 747). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by a TxUE, intended for the RxUE, for example. The indication is received from the TxUE.

The RxUE receives scheduling information for the next communication between SL UEs (block 749). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a DCI message from the access node. The RP configurations and associated SL-DMRS configurations, the scheduling information, and the indication may be received in one or more messages. As an example, the RP configurations and associated SL-DMRS configurations may be received in a first message corresponding to operations associated with block 745. As an example, the indication may be received in a second message corresponding to operations associated with block 747, while the scheduling information may be received in a third message corresponding to operations associated with block 749. As another example, the RP configurations and associated SL-DMRS configurations, the indication, and the scheduling information may be received in a single message corresponding to operations associated with blocks 745-749. Other combinations of receiving the RP configurations and associated SL-DMRS configurations, the scheduling information, and the indication are possible.

The RxUE receives data and SL-DMRS in the particular RP (block 751). The transmission is received in accordance with the SL-DMRS configuration. The RxUE performs channel measurements (block 753). The channel measurements maybe performed in accordance with the SL-DMRS received from the TxUE, for example.

The RxUE performs a check to determine if there is a different resource that is more suitably meets the channel measurements (block 755). As an example, the RxUE may determine that alternate resources are needed to meet data rate requirements with the channel measurements as determined in block 753, or that a different SL-DMRS configuration (with higher or lower SL-DMRS density) is needed to allow for adequate channel measurements. Alternatively, the RxUE may determine that the current SL- DMRS configuration with a higher or lower SL-DMRS density is more suitable. The RxUE identifies the resource (e.g., a different RP RPj or SL-DMRS configuration Dj) if one exists. If there is a different resource that more suitably meets the channel measurements, the RxUE transmits control signaling, such as a SCI including an

ACK/NACK, CSI, etc. (block 757). The control signaling includes the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be transmitted to the TxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent

communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

The RxUE may return to block 747 to receive an indication of the different resource and the operations 740 may continue as described above, but for the different resource.

In an embodiment, in mode 2 communication, the TxUE determines whether or not to permit the resource switch. In such a situation, the access node is not involved in the communication between the SL UEs. Figure 8A illustrates a flow diagram of example operations 8oo occurring in a TxUE participating in SL communications and resource switching, with the SL UEs operating in mode 2. Operations 8oo may be indicative of operations occurring in a TxUE as the TxUE participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching.

Operations 8oo begin with the TxUE obtaining RP configurations and associated SL- DMRS configurations (block 805). The RP configurations {RP , RP₂, RP_N} and the associated SL-DMRS configurations {D ,, D₂, D_N} maybe received over RRC signaling. The RP configurations and the associated SL-DMRS configurations may be received from the network (such as a network entity (including an access node, a controller, or network function), or a database), or another SL UE. Alternatively, the RP configurations and the associated SL-DMRS configurations may be preconfigured. As an example, the RP configurations and the associated SL-DMRS configurations may be specified by a technical standard and saved in a memory of the TxUE. As another example, the RP configurations and the associated SL-DMRS configurations may be specified by an operator of the network and provided to the TxUE during an attachment procedure or a mobility procedure (such as a handover).

The TxUE transmits an indication of a particular RP (RPi) for a next communication (block 807). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by the TxUE, intended for a RxUE, for example. The TxUE transmits scheduling information for the next communication between the SL UEs (block 809). Because the access node is not involved in the communications between the SL UEs, the TxUE may select the resources for the next communication between the SL UEs and sends the scheduling information related to the resources. The scheduling information may be transmitted in an SCI, for example. The scheduling information, and the indication may be transmitted in one or more messages. As an example, the indication may be transmitted in a first message corresponding to operations associated with block 807. As an example, the scheduling information may be transmitted in a second message corresponding to operations associated with block 809. As another example, the indication, and the scheduling information may be transmitted in a single message corresponding to operations associated with blocks 807-809. Other combinations of transmitting the scheduling information, and the indication are possible.

The TxUE transmits data and SL-DMRS in the particular RP (block 811). The transmission is transmitted in accordance with the SL-DMRS configuration. The TxUE may receive control signaling, such as a SCI including an ACK/NACK, CSI, etc. The TxUE performs a check to determine if control signaling has been received (block 813). The control signaling may include the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be received from the RxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

If the TxUE has received the request requesting the selection of the different resource, the TxUE transmits an indication of the different resource (block 815). Operations 800 may continue as described above, but for the different resource. If the TxUE has not received the request requesting the selection of the different resource, operations 800 terminate.

Figure 8B illustrates a flow diagram of example operations 850 occurring in a RxUE participating in SL communications and resource switching, with the SL UEs operating in mode 2. Operations 800 may be indicative of operations occurring in a RxUE as the RxUE participates in SL communications and resource (e.g., RP or SL-DMRS

configuration) switching.

Operations 850 begin with the RxUE obtaining RP configurations and associated SL- DMRS configurations (block 855). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D ,, D₂, ..., D_N} maybe received over RRC signaling. The RP configurations and the associated SL-DMRS configurations may be received from the TxUE. The RP configurations and the associated SL-DMRS configurations maybe received from the network (such as a network entity (including an access node, a controller, or network function), or a database), or another SL UE. Alternatively, the RP configurations and the associated SL-DMRS configurations may be preconfigured. As an example, the RP configurations and the associated SL-DMRS configurations may be specified by a technical standard and saved in a memory of the RxUE. As another example, the RP configurations and the associated SL-DMRS configurations may be specified by an operator of the network and provided to the RxUE during an attachment procedure or a mobility procedure (such as a handover).

The RxUE receives an indication of a particular RP (RPi) for a next communication (block 857). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by a TxUE, intended for the RxUE, for example. The indication is received from the TxUE, for example. The RxUE receives scheduling information for the next communication between SL UEs (block 859). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a SCI message from the TxUE. The scheduling information, and the indication may be received in one or more messages. As an example, the indication may be received in a first message corresponding to operations associated with block 857. As an example, the scheduling information may be received in a second message corresponding to operations associated with block 859. As another example, the indication, and the scheduling information may be received in a single message corresponding to operations associated with blocks 857-859. Other combinations of receiving the scheduling information, and the indication are possible.

The RxUE receives data and SL-DMRS in the particular RP (block 861). The

transmission is transmitted in accordance with the SL-DMRS configuration. The RxUE performs channel measurements (block 863). The channel measurements maybe performed in accordance with the SL-DMRS received from the TxUE, for example.

The RxUE performs a check to determine if there is a different resource that more suitably meets the channel measurements (block 865). As an example, the RxUE may determine that alternate resources are needed to meet data rate requirements with the channel measurements as determined in block 863, or that a different SL-DMRS configuration (with higher or lower SL-DMRS density) is needed to allow for adequate channel measurements. Alternatively, the RxUE may determine that the current SL- DMRS configuration with a higher or lower SL-DMRS density is more suitable. The RxUE identifies the resource (e.g., a different RP RPj or SL-DMRS configuration Dj) if one exists. If there is a different resource that more suitably meets the channel measurements, the RxUE transmits control signaling, such as a SCI including an ACK/NACK, CSI, etc. (block 867). The control signaling includes the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be transmitted to the TxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent

The RxUE may return to block 857 to receive an indication of the different resource and the operations 850 may continue as described above, but for the different resource.

In the discussion of the example embodiments presented herein, the configuration information, the scheduling information, the indications, etc., are presented as being transmitted or received in separate operations or messages. However, in practice, it is often advantageous (e.g., to reduce latency, communications overhead, etc.) to transmit or receive more than one of such information in a single message. As an example, instead of transmitting three separate messages, with each message containing only one of the configuration information, the scheduling information, the indications, etc., a single message may be transmitted that includes all of the information. As another example, instead of transmitting three separate messages, with each message containing only one of the configuration information, the scheduling information, the indications, etc., a single message may be transmitted that includes two pieces of the information, and another message may be transmitted that includes the remaining piece of the information. Similar advantages are present when receiving messages. Therefore, the discussion of separate operations or messages should not be construed as being limiting to the scope of the example embodiments.

In the discussion of the example embodiments presented herein, the illustrative messages carrying information are provided as examples and are not meant to limit the scope of the example embodiments. As an example, the information, as described herein as being carried by PHY signaling (in the form of DCI, SCI, SFCI, UCI, etc.), may instead be carried by MAC or RRC signaling, or even in higher layer signaling. Additionally, the example embodiments may or may not be performed for every scheduling instance. As an example, control signaling to carry CSI or a RP/SL-DMRS indication may be scheduled every n slots, every n instances of a PSSCH, every n instances of a RP, and so on, where n is an integer number.

According to an alternative embodiment, RRC signaling carries RP configurations as well as SL-DMRS configurations and indications. SL-DMRS indication may include an indication of an associated DMRS configuration (in a situation where the association of multiple SL-DMRS configurations with a RP is possible) and/ or indication of values for configuration parameters such as patterns and ports when the values are unknown or are desired to be overridden. In other words, a single RRC message includes the RP configurations, the SL-DMRS configurations and indications, as well as an indication of an associated DMRS configuration or values for configuration parameters. In this alternative embodiment, lower-layer signaling is not employed for configuration and indication.

According to an alternative embodiment, RRC signaling carries RP configurations as well as SL-DMRS configurations, but SL-DMRS indications are carried by MAC and/ or PHY signaling (DCI, SCI, etc.) in an activation or deactivation manner. In this case, lower- layer signaling, such as MAC and PHY signaling, activates and/or deactivates the use of SL-DMRS configurations per connection, per RP, per slot, per bandwidth, etc., meaning that once a configuration is activated, it remains active until deactivated or altered by subsequent signaling or by expiration of a timer, for example.

Other alternative embodiments are not precluded. Furthermore, alternative

embodiments are also possible regarding one or multiple messages carry one or multiple pieces of information regarding configurations and indications. As an example, a single message carries one or multiple pieces of information. As another example, multiple messages carry one or multiple pieces of information. As yet another example, one message carries one or a subset of multiple pieces of information, while multiple messages carry one or a subset of multiple pieces of information.

In the example embodiments presented above, when operating in mode l, both the TxUE and the RxUE are capable of receiving signals from the access node directly. However, it is possible that one of the SL UEs is not in network coverage. In such situations, it is possible that one SL UE communicates the control information received from the access node to the other SL UE. For example, a first SL UE receiving a DCI message containing scheduling information may communicate the information to a second SL UE in an SCI message prior to PSSCH communications. Other information such as configuration or indication messages, ACK/NACK, request messages, and so on, may also be

communicated by a first SL UE to a second SL UE after receiving the information from an access node.

In the example embodiments presented above, a request message indicates an alternative SL-DMRS configuration or alternative values for the SL-DMRS, which then triggers signaling to switch to another RP that is associated with the requested alternative SL- DMRS. Alternatively, the request message may directly indicate a particular RP for switching. For example, a SL UE may perform measurements and realize that a particular SL-DMRS density in a particular SL-DMRS configuration D_j is more suitable according to the current channel conditions. In this case, the SL UE may request switching to a RPj that is associated with the particular SL-DMRS configuration Dj (by indicating RP_j) rather than indicating D_j.

In an embodiment, an RxUE initiates a request for an alternative SL-DMRS

configuration or RP switching. However, the initiation of signaling for RP switching, SL- DMRS adaptation, and so on, may be performed by a TxUE, an access node, or another entity, such as a Roadside Unit (RSU). In the example embodiments presented above, RP switching is performed for SL-DMRS adaptation. However, in general, RP switching can be performed for adaptation of other frame structure attributes or due to other reasons such as load balancing, quality of service (QoS), and so on. A detailed discussion of RP switching for the adaptation of other frame structure attributes or for other reasons is provided below.

Each of the signaling steps described in example embodiments presented herein may be accompanied with other signaling such as ACK/NACK messages. Such signaling is omitted for the sake of brevity. Furthermore, signaling steps may be performed in a different order or they may be combined. For example, scheduling information, resource pool selection, and/or SL-DMRS indication may be combined in a message, carried in separate messages, or combined in multiple messages with each message carrying one or more of the information. The information may be communicated in an order different from what is presented herein.

SL-DMRS configurations may differ. As an example, SL-DMRS configurations may differ in time-domain pattern (e.g., number of symbols per SL-DMRS, number of SL-DMRS per slot (such as number of additional SL-DMRS per slot), and so on); frequency-domain pattern (e.g., density or comb pattern in a physical resource block (PRB), comb pattern at PRB level or other level, bandwidth of SL-DMRS (such as whether the SL-DMRS is limited to the PSSCH bandwidth or the SL-DMRS may be extended beyond the PSSCH bandwidth, for example), and so on); and number of ports and time division multiplexing (TDM)/frequency division multiplexing (FDM)/CDM group configurations.

In an embodiment, each of the SL-DMRS configurations may be associated with a carrier, a bandwidth part (BWP), a time-domain resource (such as a slot or a frame), a RP, a pattern in resources such as a time-frequency repetition pattern (TFRP), and so on. In the discussion of the example embodiments presented herein, an emphasis is placed on associations with RPs, but other alternatives are possible and not precluded. Each RP or SL-DMRS configuration may be UE-specific, or, alternatively, may be used by a group or all SL UEs. Therefore, if the configurations are obtained by signaling, the signaling may be broadcast, groupcast, geocast, multicast, unicast to a specific UE, etc.

If multiple SL-DMRS configurations are available for a transmission, for example on a PSSCH, the SL UE can be configured (e.g., by RRC or MAC signaling) or indicated (e.g., by MAC or PHY signaling) regarding which SL-DMRS configuration to use for the transmission. In order to indicate a particular SL-DMRS configuration from the available configurations, an identifier (ID) or an index associated with the configuration can be used as the indicator, for example. Configuration IDs can be used for association between configurations. For example, a RP configuration/indication may include SL-DMRS configuration IDs or vice versa. A configuration ID is normally included in the configuration message. The ID is expected to be unique, i.e., not currently in use by more than one active configuration. If a configuration is released, its ID can be reused, possibly after a certain period of time has passed. Using a configuration ID for indicating a SL-DMRS configuration may have the following disadvantages:

- Overhead: Configuration IDs can be large because they need to guarantee uniqueness in the presence of possibly a large number of UEs or RPs, each requiring one or more configurations;

- Ambiguity: If configurations are not sent by a central controller such as an access node, multiple active configurations may have the same ID. As an example, in mode 2 communications where multiple SL UEs may configure DMRS in an area, if two different configurations happen to have the same ID, a SL-DMRS indication signaling cannot be interpreted unambiguously.

The latter issue can be addressed by indicating a configuration ID jointly with a unique ID of the SL UE that has sent the configuration, but this method may worsen the overhead problem.

An alternative to indicating a configuration by its ID is to associate an index to each configuration. This index may or may not be included in the configuration message. For example, if there are M RPs, with each RP being associated with N SL-DMRS

configurations, then at least flog₂ ( M . N)] bits are needed to indicate a configuration ID, but only flog₂ N] bits are needed to indicate a configuration index for a PSSCH scheduled in a particular RP.

In some embodiments, a SL-DMRS configuration may not carry all the information to uniquely determine the SL-DMRS. In such cases, the signaling indicating a SL-DMRS configuration can further carry the additional information needed. For example, if a SL- DMRS configuration determines all the SL-DMRS information except for the number of additional SL-DMRS per slot, a DCI/SCI indicating the SL-DMRS configuration can also carry information regarding the number of additional SL-DMRS.

Alternatively, information indicated by the configuration may be overridden by the indication signaling. For example, if a SL-DMRS configuration determines a number of additional SL-DMRS, a DCI/SCI indicating the SL-DMRS configuration can further carry a different number of additional SL-DMRS that overrides the current value for a scheduled transmission. Yet as another alternative, signaling, such as RRC or MAC signaling, may override configuration parameters in a persistent or semi-persistent manner.

The example embodiments presented herein may occur in an access node participating in mode l communication or a TxUE participating in mode 2 communication. Furthermore, a RxUE may request a different SL-DMRS configuration or pattern (such as a larger or smaller number of additional SL-DMRS, for example). The RxUE may generate the request based on information, such as (but not limited to):

- Sensor information from a speedometer;

- Speed information in a basic safety message (BSM);

- Results of measurements using SL-DMRS of a previous message from the same TxUE;

- Results of measurements using a CSI-RS from the same TxUE.

In the situation where the RxUE generates the request based on sensor information, an embodiment technique involves the RxUE acquiring an estimate of its speed v through a sensor (e.g., a speedometer) and calculates the coherence time T_c associated with v. An example equation is T_c = a/f_m, where:

f_m ⁼ ~f_c is the Doppler frequency corresponding to the speed v and center/carrier frequency f_c, and c is the speed of light; and

a is a constant, e.g., a = 0.423.

Alternative equations, other values for a, or a tabulation of an equation are other possibilities to calculate the coherence time. Then, if the RxUE detects that the coherence time associated with its speed is longer or shorter than is addressed by the current number of additional SL-DMRS, the RxUE can request the TxUE to decrease or increase the number of additional SL-DMRS, accordingly.

This technique may be simple to implement, but it has the drawback that the RxUE only considers its own speed in order to make the request, while the actual number of additional SL-DMRS needs for a SL communication may generally depend on the relative speed between the two SL UEs of the link. For example, in communications between vehicle UEs in a platoon (i.e., all vehicle UEs are in a cluster traveling in the same direction at approximately the same speed), all the vehicle UEs may be traveling at highway speeds, but their relative speed can be very small, practically zero, which makes the technique potentially wasteful in terms of SL-DMRS resource overhead. On the other hand, for communications between vehicle UEs traveling in opposite directions, this technique may not provide sufficient SL-DMRS density unless the SL-DMRS resource are overprovisioned, in which case the technique is again potentially inefficient.

An alternative technique involves letting the RxUE use velocity sensor information only as starting point, and then the RxUE adjusts the SL-DMRS density based on the specifics of each SL channel. For example, the SL-DMRS density for a SL between two SL UEs can be adjusted to the relative velocity between the two SL UEs. As another example, the SL- DMRS density for a transmission to multiple receiving SL UEs in a groupcast sidelink should satisfy the Doppler corresponding to the greatest of relative velocities between the TxUE and each of the RxUEs.

In the situation where the RxUE generates the request based on speed information in a BSM, an embodiment technique involves the RxUE combining its own sensory information with the information received in a BSM from the TxUE in order to produce the request. For this purpose, the RxUE acquires an estimate of its own speed v_t and the speed of the other SL UE v₂ and calculates the coherence time associated with v = v_L + v₂. This estimate may be pessimistic because the relative speed between the two SL UEs (as shown in Figure 5 Error! Reference source not found.) may be lower than v = v₁ + v₂. Therefore, as an alternative technique, the RxUE may calculate the coherence time associated with v = b(v₁ + v₂), where b is a constant (pre)configured or specified by the technical standard.

In the situation where the RxUE generates the request based on measurement results using SL-DMRS of a previous message from the TxUE, an embodiment technique involves the RxUE performing measurements on SL-DMRS of the previous message from the TxUE in order to produce the request. For example, given a time-domain density of SL-DMRS from the TxUE, the RxUE can perform measurements on multiple symbols and combine the results in order to estimate a coherence time. If the estimated coherence time is longer or shorter than is addressed by the current number of additional SL- DMRS, the RxUE can request the TxUE to decrease or increase the number of additional SL-DMRS, accordingly.

In the situation where the RxUE generates the request based on measurement results using CSI-RS from the TxUE, an embodiment technique involves the RxUE performing measurements on CSI-RS of the previous message from the TxUE in order to produce the request, in a manner similar to the embodiment technique utilizing the SL-DMRS described previously. In practice, the CSI-RS needs to be sufficiently dense and sufficiently spread over time in order to allow the RxUE to perform reliable measurements. Therefore, a periodic or semi-persistent CSI-RS is better suited for this purpose than an aperiodic CSI-RS. The overhead for such CSI-RS may be large for a system congested with SL UEs in a relatively small area. However, the CSI-RS for this purpose does not need to be necessarily configured within the bandwidth that is configured for communications between the two SL UEs because the primary purpose is to estimate the relative speed and coherence time. Therefore, even if a coherence time T_Ci is estimated based on measurements on CSI-RS in a center/ carrier frequency f_Ci, then a coherence time T_Ci on a center/carrier frequency /_¾ can be obtained by T_Ci = T_{c c}Jf_C2, for example.

A combination of embodiment techniques for generating the request is possible. As an example, the RxUE may utilize sensor information and SL-DMRS measurements. As another example, the RxUE may utilize sensor information and speed information from a BSM. As another example, the RxUE may utilize sensor information, speed information from a BSM, and SL-DMRS measurements.

The example embodiments presented herein may be generalized to RP switching for purposes other than SL-DMRS adaptation. As an example, frame structure attributes may be associated with a RP, and a request or demand to change any or all of the frame structure attributes may trigger a RP switch. Examples of frame structure attributes include, but are not limited to, symbol location of reference signals (CSI-RS, DMRS, PTRS, tracking reference signal (TRS), etc.), reference signal patterns and

configurations, slot length in terms of the number of symbols, length or bandwidth of a shared channel/region, length or bandwidth of a control channel/region, numerology parameters, and so on. If a SL UE or an access node detects that a change of such attributes is desired or needed, the SL UE or access node may initiate signaling for a RP switch.

As another example, system-level factors such as load balancing or provisioning quality of service (QoS) may also trigger a RP switch. For example, if a RP is detected to be overloaded and an alternative RP can be used for a better load balancing, the SL UE or the access node detecting the overloaded RP may initiate signaling for a RP switch.

Figure 9A illustrates a flow diagram of example operations 900 occurring in an access node participating in SL communications and resource switching where a RP or attribute is selected by the access node. Operations 900 may be indicative of operations occurring in an access node as the access node participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching, where a RP or attribute is selected by the access node.

Operations 900 begin with the access node sending RP configurations and associated SL- DMRS configurations (block 905). The RP configurations {RP , RP₂, RP_N} and the associated SL-DMRS configurations {D ,, D₂, D_N} maybe sent to the SL UEs. In an embodiment, each RP may be associated with a SL-DMRS configuration or, alternatively, each RP may be associated with multiple SL-DMRS configurations. In which case, further signaling may be used for indication of a SL-DMRS configuration for a transmission in the RP. Each SL-DMRS configuration may include information on SL- DMRS sequence generation, density and patterns in time and frequency domains, number of ports, QCL information, and so on. Each RP or SL-DMRS configuration may be associated with UEs in a cell, a specific UE or a group of UEs, one or multiple connections, and so on. Additional details are provided below. The configuration may be sent using, e.g., RRC signaling (dedicated or common) from the access node, or by PC5 RRC signaling. Alternatively, the configuration could be pre-configured.

The access node transmits an indication of a particular RP (RPi) for a next

communication between SL UEs (block 907). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by a TxUE, intended for a RxUE, for example. The access node transmits scheduling information for the next communication between SL UEs (block 909). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be transmitted in a DCI message.

The access node performs a check to determine if a request requesting the selection of a different resource is received (block 911). The access node may receive control signaling, such as an UCI including an ACK/NACK. The control signaling may include the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be received from the TxUE or the RxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

If the access node has received the request requesting the selection of the different resource, the access node transmits an indication of the different resource (block 913). If the request specified a RP RPj, the access node may transmit the indication of the specified RP RPj. If the request specified a SL-DMRS configuration Dj, the access node may transmit the indication of the RP associated with the SL-DMRS configuration Dj, RPj. The access node may or may not allow the RP switch. The RP switch may be rejected for a variety of reasons, including too many SL communications are already using the requested RP, historic RP communications performance, ACK/NACK rate for the RP, and so on.

Figure 9B illustrates a flow diagram of example operations 920 occurring in TxUE participating in SL communications and resource switching, where a RP or attribute is selected by the access node. Operations 920 may be indicative of operations occurring in a TxUE as the TxUE participates in SL communications and resource (e.g., RP or SL- DMRS configuration) switching, where a RP or attribute is selected by the access node.

Operations 920 begin with the TxUE receiving RP configurations and associated SL- DMRS configurations (block 925). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D ,, D₂, ..., D_N} maybe received from an access node. In an embodiment, each RP may be associated with a SL-DMRS configuration or, alternatively, each RP may be associated with multiple SL-DMRS configurations. In which case, further signaling may be used for indication of a SL-DMRS configuration for a transmission in the RP. Each SL-DMRS configuration may include information on SL- DMRS sequence generation, density and patterns in time and frequency domains, number of ports, QCL information, and so on. Each RP or SL-DMRS configuration may be associated with UEs in a cell, a specific UE or a group of UEs, one or multiple connections, and so on. Additional details are provided below. The configuration may be sent using, e.g., RRC signaling (dedicated or common) from the access node, or by PC5 RRC signaling. Alternatively, the configuration could be pre-configured.

The TxUE receives an indication of a particular RP (RPi) for a next communication (block 927). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by the TxUE, intended for an RxUE, for example. The TxUE receives scheduling information for the next communication between SL UEs (block 929). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a DCI message.

The TxUE transmits signals in the particular RP (block 931). The signals may include data, reference signals, control signals, etc. The transmission is transmitted in accordance with the SL-DMRS configuration. The TxUE may receive control signaling, such as a SCI including an ACK/NACK, CSI, etc. The TxUE performs a check to determine if control signaling has been received (block 933). The control signaling may include the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information maybe received from the RxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

If the TxUE has received the request requesting the selection of the different resource, the TxUE transmits another request requesting the selection of the different resource (block 935). The request requesting the selection of the different resource is transmitted to the access node, for example. The request requesting the selection of the different resource may be transmitted in an UCI. The request requesting the selection of the different resource may be a different request received by the TxUE in block 933 or the request requesting the selection of the different resource may be the request received by the TxUE in block 933 that is forwarded to the access node.

The TxUE may return to block 927 to receive an indication of the different resource and the operations 920 may continue as described above, but for the different resource.

Figure 9C illustrates a flow diagram of example operations 940 occurring in RxUE participating in SL communications and resource switching, where a RP or attribute is selected by the access node. Operations 940 may be indicative of operations occurring in a RxUE as the RxUE participates in SL communications and resource (e.g., RP or SL- DMRS configuration) switching, where a RP or attribute is selected by the access node.

Operations 940 begin with the RxUE receiving RP configurations and associated SL- DMRS configurations (block 945). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D ,, D₂, ..., D_N} maybe received from an access node. In an embodiment, each RP may be associated with a SL-DMRS configuration or, alternatively, each RP may be associated with multiple SL-DMRS configurations. In which case, further signaling may be used for indication of a SL-DMRS configuration for a transmission in the RP. Each SL-DMRS configuration may include information on SL- DMRS sequence generation, density and patterns in time and frequency domains, number of ports, QCL information, and so on. Each RP or SL-DMRS configuration may be associated with UEs in a cell, a specific UE or a group of UEs, one or multiple connections, and so on. Additional details are provided below. The configuration may be sent using, e.g., RRC signaling (dedicated or common) from the access node, or by PC5 RRC signaling. Alternatively, the configuration could be pre-configured. The RxUE receives an indication of a particular RP (RPi) for a next communication (block 947). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by a TxUE, intended for the RxUE, for example. The RxUE receives scheduling information for the next communication between SL UEs (block 949). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a DCI message.

The RxUE receives signals in the particular RP (block 951). The signals may include data, reference signals, control signals, etc. The transmission is received in accordance with the SL-DMRS configuration. The RxUE performs an assessment of the RP or attributes (block 953). The assessment may be performed in accordance with the signals (e.g., SL- DMRS, CSI-RS, other RS, data, control signals, etc.) received from the TxUE, for example. The assessment may be based on SINR measurements, SNR measurements, RSRP measurements, RSRQ measurements, received signal power measurements, etc.

The RxUE performs a check to determine if there is a different RP or attribute that is more suitably meets the assessment (block 955). As an example, the RxUE may determine that alternate RPs are needed to meet data rate requirements with the assessment as determined in block 953, or that a different attribute is needed to allow for adequate assessment. The RxUE identifies the resource (e.g., a different RP RPj or SL- DMRS configuration Dj) if one exists. If there are multiple resources, then the RxUE may randomly select a resource or use historical information (previous performance results using the resources, traffic on the resources, etc.) to select a resource, for example. If there is a different resource that more suitably meets the assessment, the RxUE transmits control signaling, such as a SCI including an ACK/NACK, CSI, etc. (block 957). The control signaling includes the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be transmitted to the TxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs. In an embodiment, the control information is transmitted directly to the access node, in an UCI, for example. In an embodiment, the control information is transmitted to both the TxUE and the access node.

The RxUE may return to block 947 to receive an indication of the different resource and the operations 940 may continue as described above, but for the different resource. Figure ioA illustrates a flow diagram of example operations tooo occurring in an access node participating in SL communications and resource switching, with the SL UEs operating in mode t and the access node not selecting the resource for the

communication between the SL UEs, where a RP or attribute is selected by the TxUE. Operations tooo may be indicative of operations occurring in an access node as the access node participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching, where a RP or attribute is selected by the TxUE.

Operations tooo begin with the access node sending RP configurations and associated SL-DMRS configurations (block 1005). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D , D₂, ..., DN} maybe sent to the SL UEs. The access node transmits scheduling information for the next communication between SL UEs (block 1007). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information maybe transmitted in a DCI message.

Figure 10B illustrates a flow diagram of example operations 1020 occurring in a TxUE participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs, where a RP or attribute is selected by the TxUE. Operations 1020 may be indicative of operations occurring in a TxUE as the TxUE participates in SL

communications and resource (e.g., RP or SL-DMRS configuration) switching, where a RP or attribute is selected by the TxUE.

Operations 1020 begin with the TxUE receiving RP configurations and associated SL- DMRS configurations (block 1025). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D ,, D₂, ..., D_N} maybe received from an access node. The TxUE transmits an indication of a particular RP (RPi) for a next

communication (block 1027). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by the TxUE, intended for a RxUE, for example. The TxUE receives scheduling information for the next communication between SL UEs (block 1029). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a DCI message.

The TxUE transmits signals in the particular RP (block 1031). The signals may include data, reference signals, control signals, etc. The transmission is transmitted in accordance with the SL-DMRS configuration. The TxUE may receive control signaling, such as a SCI including an ACK/NACK, CSI, etc. The TxUE performs a check to determine if control signaling has been received (block 1033). The control signaling may include the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information maybe received from the RxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

If the TxUE has received the request requesting the selection of the different resource, the TxUE transmits an indication of the different resource (block 1035). Operations 1020 may continue as described above, but for the different resource. If the TxUE has not received the request requesting the selection of the different resource, operations 1020 terminate.

Figure 10C illustrates a flow diagram of example operations 1040 occurring in a RxUE participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs, where a RP or attribute is selected by the TxUE. Operations 1040 may be indicative of operations occurring in a RxUE as the RxUE participates in SL

Operations 1040 begin with the RxUE receiving RP configurations and associated SL- DMRS configurations (block 1045). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D ,, D₂, ..., D_N} maybe received from an access node. The RxUE receives an indication of a particular RP (RPi) for a next communication (block 1047). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by a TxUE, intended for the RxUE, for example. The indication is received from the TxUE.

The RxUE receives scheduling information for the next communication between SL UEs (block 1049). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a DCI message from the access node. The RxUE receives signals in the particular RP (block 1051). The signals may include data, reference signals, control signals, etc. The transmission is received in accordance with the SL-DMRS configuration. The RxUE performs an assessment of the RP or attributes (block 1053). The assessment may be performed in accordance with the signals (e.g., SL-DMRS, CSI-RS, other RS, data, control signals, etc.) received from the TxUE, for example. The assessment may be based on SINR measurements, SNR measurements, RSRP measurements, RSRQ

measurements, received signal power measurements, etc.

The RxUE performs a check to determine if there is a different RP or attribute that is more suitably meets the assessment (block 1055). As an example, the RxUE may determine that alternate RPs are needed to meet data rate requirements with the assessment as determined in block 1053, or that a different attribute is needed to allow for adequate assessment. The RxUE identifies the resource (e.g., a different RP RPj or SL-DMRS configuration Dj) if one exists. If there are multiple resources, then the RxUE may randomly select a resource or use historical information (previous performance results using the resources, traffic on the resources, etc.) to select a resource, for example. If there is a different resource that more suitably meets the assessment, the RxUE transmits control signaling, such as a SCI including an ACK/NACK, CSI, etc.

(block 1057). The control signaling includes the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be transmitted to the TxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs. In an embodiment, the control information is transmitted directly to the access node, in an UCI, for example. In an embodiment, the control information is transmitted to both the TxUE and the access node.

The RxUE may return to block 1047 to receive an indication of the different resource and the operations 1040 may continue as described above, but for the different resource.

Figure 11A illustrates a flow diagram of example operations 1100 occurring in a TxUE participating in SL communications and resource switching, with the SL UEs operating in mode 2, where a RP or attribute is selected by the TxUE. Operations 1100 may be indicative of operations occurring in a TxUE as the TxUE participates in SL

Operations 1100 begin with the TxUE obtaining RP configurations and associated SL- DMRS configurations (block 1105). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D , D₂, ..., DN} maybe received over RRC signaling. The RP configurations and the associated SL-DMRS configurations may be received from the network (such as a network entity (including an access node, a controller, or network function), or a database), or another SL UE. Alternatively, the RP configurations and the associated SL-DMRS configurations may be preconfigured. As an example, the RP configurations and the associated SL-DMRS configurations may be specified by a technical standard and saved in a memory of the TxUE. As another example, the RP configurations and the associated SL-DMRS configurations may be specified by an operator of the network and provided to the TxUE during an attachment procedure or a mobility procedure (such as a handover).

The TxUE transmits an indication of a particular RP (RPi) for a next communication (block 1107). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by the TxUE, intended for a RxUE, for example. The TxUE transmits scheduling information for the next communication between the SL UEs (block 1109). Because the access node is not involved in the communications between the SL UEs, the TxUE may select the resources for the next communication between the SL UEs and sends the scheduling information related to the resources. The scheduling information may be transmitted in an SCI, for example.

The TxUE transmits signals in the particular RP (block till). The signals may include data, reference signals, control signals, etc. The transmission is transmitted in accordance with the SL-DMRS configuration.

The TxUE may receive control signaling, such as a SCI including an ACK/NACK, CSI, etc. The TxUE performs a check to determine if control signaling has been received (block 1113). The control signaling may include the request requesting the selection of a different resource (e.g., a different RP RPj). The control information may be received from the RxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

If the TxUE has received the request requesting the selection of the different resource, the TxUE transmits an indication of the different resource (block 1115). Operations 1100 may continue as described above, but for the different resource. If the TxUE has not received the request requesting the selection of the different resource, operations 1100 terminate.

Figure 11B illustrates a flow diagram of example operations 1150 occurring in a RxUE participating in SL communications and resource switching, with the SL UEs operating in mode 2, where a RP or attribute is selected by the TxUE. Operations 1150 may be indicative of operations occurring in a RxUE as the RxUE participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching, where a RP or attribute is selected by the TxUE.

Operations 1150 begin with the RxUE obtaining RP configurations and associated SL- DMRS configurations (block 1155). The RP configurations {RP , RP₂, RP_N} and the associated SL-DMRS configurations {D ,, D₂, D_N} maybe received over RRC signaling. The RP configurations and the associated SL-DMRS configurations may be received from the TxUE. The RP configurations and the associated SL-DMRS configurations maybe received from the network (such as a network entity (including an access node, a controller, or network function), or a database), or another SL UE. Alternatively, the RP configurations and the associated SL-DMRS configurations may be preconfigured. As an example, the RP configurations and the associated SL-DMRS configurations may be specified by a technical standard and saved in a memory of the RxUE. As another example, the RP configurations and the associated SL-DMRS configurations may be specified by an operator of the network and provided to the RxUE during an attachment procedure or a mobility procedure (such as a handover).

The RxUE receives an indication of a particular RP (RPi) for a next communication (block 1157). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by a TxUE, intended for the RxUE, for example. The indication is received from the TxUE, for example. The RxUE receives scheduling information for the next communication between SL UEs (block 1159). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a SCI message from the TxUE. The RxUE receives signals in the particular RP (block 1161). The signals may include data, reference signals, control signals, etc. The transmission is received in accordance with the SL-DMRS configuration. The RxUE performs assessments (block 1163). The assessments may be performed in accordance with the signals received from the TxUE, for example.

The RxUE performs a check to determine if there is a different resource that more suitably meets the assessments (block 1165). As an example, the RxUE may determine that alternate RPs are needed to meet data rate requirements with the assessment as determined in block 1153, or that a different attribute is needed to allow for adequate assessment. The RxUE identifies the resource (e.g., a different RP RPj or SL-DMRS configuration Dj) if one exists. If there are multiple resources, then the RxUE may randomly select a resource or use historical information (previous performance results using the resources, traffic on the resources, etc.) to select a resource, for example. If there is a different resource that more suitably meets the assessment, the RxUE transmits control signaling, such as a SCI including an ACK/NACK, CSI, etc. (block 1167). The control signaling includes the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be transmitted to the TxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs. In an embodiment, the control information is transmitted directly to the access node, in an UCI, for example.

The RxUE may return to block 1157 to receive an indication of the different resource and the operations 1150 may continue as described above, but for the different resource.

The example embodiments presented herein may be generalized to RP switching for any purpose that an access node or SL UE determines to improve efficiency or deems to be appropriate.

Figure 12A illustrates a flow diagram of generalized example operations 1200 occurring in an access node participating in SL communications and resource switching.

Operations 1200 may be indicative of operations occurring in an access node as the access node participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching.

Operations 1200 begin with the access node sending RP configurations and associated SL-DMRS configurations (block 1205). The RP configurations {RP , RP₂, ..., RP_N} and the associated SL-DMRS configurations {D ,, D₂, ..., D_N} maybe sent to the SL UEs. In an embodiment, each RP may be associated with a SL-DMRS configuration or, alternatively, each RP may be associated with multiple SL-DMRS configurations. In which case, further signaling may be used for indication of a SL-DMRS configuration for a transmission in the RP. Each SL-DMRS configuration may include information on SL- DMRS sequence generation, density and patterns in time and frequency domains, number of ports, QCL information, and so on. Each RP or SL-DMRS configuration may be associated with UEs in a cell, a specific UE or a group of UEs, one or multiple connections, and so on. Additional details are provided below. The configuration may be sent using, e.g., RRC signaling (dedicated or common) from the access node, or by PC5 RRC signaling. Alternatively, the configuration could be pre-configured.

The access node transmits an indication of a particular RP (RPi) for a next

communication between SL UEs (block 1207). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by a TxUE, intended for a RxUE, for example. The indication may be explicitly sent, such as an RP index in a message. The indication may be implicitly sent, wherein the RP index may be determined from resource(s) used to send the message. As an example, a time slot number or a RB location in frequency may serve as an implicit indication of the particular RP. The access node transmits scheduling information for the next communication between SL UEs (block 1209). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be transmitted in a DCI message.

The access node performs a check to determine if a request requesting the selection of a different resource is received (block 1211). The access node may receive control signaling, such as an UCI including an ACK/NACK. The control signaling may include the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be received from the TxUE or the RxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

If the access node has received the request requesting the selection of the different resource, the access node transmits an indication of the different resource (block 1213). If the request specified a RP RPj, the access node may transmit the indication of the specified RP RPj. If the request specified a SL-DMRS configuration Dj, the access node may transmit the indication of the RP associated with the SL-DMRS configuration Dj, RPj. The access node may or may not allow the RP switch. The RP switch may be rejected for a variety of reasons, including too many SL communications are already using the requested RP, historic RP communications performance, ACK/NACK rate for the RP, and so on.

Figure 12B illustrates a flow diagram of generalized example operations 1220 occurring in TxUE participating in SL communications and resource switching. Operations 1220 may be indicative of operations occurring in a TxUE as the TxUE participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching.

Operations 1220 begin with the TxUE receiving RP configurations and associated SL- DMRS configurations (block 1225). The RP configurations {RP , RP₂, ..., RP_N} and the associated SL-DMRS configurations {D ,, D₂, ..., D_N} maybe received from an access node. In an embodiment, each RP may be associated with a SL-DMRS configuration or, alternatively, each RP may be associated with multiple SL-DMRS configurations. In which case, further signaling may be used for indication of a SL-DMRS configuration for a transmission in the RP. Each SL-DMRS configuration may include information on SL- DMRS sequence generation, density and patterns in time and frequency domains, number of ports, QCL information, and so on. Each RP or SL-DMRS configuration may be associated with UEs in a cell, a specific UE or a group of UEs, one or multiple connections, and so on. Additional details are provided below. The configuration may be sent using, e.g., RRC signaling (dedicated or common) from the access node, or by PC5 RRC signaling. Alternatively, the configuration could be pre-configured.

The TxUE receives an indication of a particular RP (RPi) for a next communication (block 1227). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by the TxUE, intended for an RxUE, for example. The TxUE receives scheduling information for the next communication between SL UEs (block 1229). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a DCI message.

The TxUE transmits signals in the particular RP (block 1231). The signals may include data, reference signals, control signals, etc. The transmission is transmitted in accordance with the SL-DMRS configuration. The TxUE may receive control signaling, such as a SCI including an ACK/NACK, CSI, etc. The TxUE performs a check to determine if control signaling has been received (block 1233). The control signaling may include the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information maybe received from the RxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

If the TxUE has received the request requesting the selection of the different resource, the TxUE transmits another request requesting the selection of the different resource (block 1235). The request requesting the selection of the different resource is transmitted to the access node, for example. The request requesting the selection of the different resource may be transmitted in an UCI. The request requesting the selection of the different resource may be a different request received by the TxUE in block 1233 or the request requesting the selection of the different resource may be the request received by the TxUE in block 1233 that is forwarded to the access node.

The TxUE may return to block 1227 to receive an indication of the different resource and the operations 1220 may continue as described above, but for the different resource. Figure 12C illustrates a flow diagram of generalized example operations 1240 occurring in RxUE participating in SL communications and resource switching. Operations 1240 may be indicative of operations occurring in a RxUE as the RxUE participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching.

Operations 1240 begin with the RxUE receiving RP configurations and associated SL- DMRS configurations (block 1245). The RP configurations {RP , RP₂, ..., RP_N} and the associated SL-DMRS configurations {D,, D₂, ..., D_N} maybe received from an access node. In an embodiment, each RP may be associated with a SL-DMRS configuration or, alternatively, each RP may be associated with multiple SL-DMRS configurations. In which case, further signaling may be used for indication of a SL-DMRS configuration for a transmission in the RP. Each SL-DMRS configuration may include information on SL- DMRS sequence generation, density and patterns in time and frequency domains, number of ports, QCL information, and so on. Each RP or SL-DMRS configuration may be associated with UEs in a cell, a specific UE or a group of UEs, one or multiple connections, and so on. Additional details are provided below. The configuration may be sent using, e.g., RRC signaling (dedicated or common) from the access node, or by PC5 RRC signaling. Alternatively, the configuration could be pre-configured.

The RxUE receives an indication of a particular RP (RPi) for a next communication (block 1247). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by a TxUE, intended for the RxUE, for example. The RxUE receives scheduling information for the next communication between SL UEs (block 1249). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a DCI message.

The RxUE receives signals in the particular RP (block 1251). The signals may include data, reference signals, control signals, etc. The transmission is received in accordance with the SL-DMRS configuration. The RxUE performs an assessment of the RP or attributes (block 1253). The assessment may be performed in accordance with the signals (e.g., SL-DMRS, CSI-RS, other RS, data, control signals, etc.) received from the TxUE, for example. The assessment may be based on SINR measurements, SNR measurements, RSRP measurements, RSRQ measurements, received signal power measurements, etc.

The RxUE performs a check to determine if an RP switch should take place (block 1255). An RP switch may take place for a variety of reasons, including, but not limited to meeting performance requirements, meeting error rate requirement, load balancing, etc. The RxUE identifies the resource (e.g., a different RP RPj or SL-DMRS configuration Dj) if one exists. If there are multiple resources, then the RxUE may randomly select a resource or use historical information (previous performance results using the resources, traffic on the resources, etc.) to select a resource, for example. If there is a different resource that more suitably meets the assessment, the RxUE transmits control signaling, such as a SCI including an ACK/NACK, CSI, etc. (block 1257). The control signaling includes the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be transmitted to the TxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs. In an embodiment, the control information is transmitted directly to the access node, in an UCI, for example. In an embodiment, the control information is transmitted to both the TxUE and the access node.

The RxUE may return to block 1247 to receive an indication of the different resource and the operations 1240 may continue as described above, but for the different resource.

Figure 13A illustrates a flow diagram of generalized example operations 1300 occurring in an access node participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs. Operations 1300 may be indicative of operations occurring in an access node as the access node participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching.

Operations 1300 begin with the access node sending RP configurations and associated SL-DMRS configurations (block 1305). The RP configurations {RP , RP₂, ..., RP_N} and the associated SL-DMRS configurations {D ,, D₂, ..., D_N} maybe sent to the SL UEs. The access node transmits scheduling information for the next communication between SL UEs (block 1307). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information maybe transmitted in a DCI message.

Figure 13B illustrates a flow diagram of example operations 1320 occurring in a TxUE participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the communication between the SL UEs. Operations 1320 may be indicative of operations occurring in a TxUE as the TxUE participates in SL communications and resource (e.g., RP or SL-DMRS

configuration) switching. Operations 1320 begin with the TxUE receiving RP configurations and associated SL- DMRS configurations (block 1325). The RP configurations {RP , RP₂, RP_N} and the associated SL-DMRS configurations {D,, D₂, D_N} maybe received from an access node. The TxUE transmits an indication of a particular RP (RPi) for a next

communication (block 1327). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by the TxUE, intended for a RxUE, for example. The indication may be explicitly sent, such as an RP index in a message. The indication may be implicitly sent, wherein the RP index may be determined from resource(s) used to send the message. As an example, a time slot number or a RB location in frequency may serve as an implicit indication of the particular RP. The TxUE receives scheduling information for the next communication between SL UEs (block 1329). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a DCI message.

The TxUE transmits signals in the particular RP (block 1331). The signals may include data, reference signals, control signals, etc. The transmission is transmitted in accordance with the SL-DMRS configuration. The TxUE may receive control signaling, such as a SCI including an ACK/NACK, CSI, etc. The TxUE performs a check to determine if control signaling has been received (block 1333). The control signaling may include the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information maybe received from the RxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

If the TxUE has received the request requesting the selection of the different resource, the TxUE transmits an indication of the different resource (block 1335). Operations 1320 may continue as described above, but for the different resource. If the TxUE has not received the request requesting the selection of the different resource, operations 1320 terminate.

Figure 13C illustrates a flow diagram of generalized example operations 1340 occurring in a RxUE participating in SL communications and resource switching, with the SL UEs operating in mode 1 and the access node not selecting the resource for the

communication between the SL UEs. Operations 1340 may be indicative of operations occurring in a RxUE as the RxUE participates in SL communications and resource (e.g., RP or SL-DMRS configuration) switching. Operations 1340 begin with the RxUE receiving RP configurations and associated SL- DMRS configurations (block 1345). The RP configurations {RP , RP₂, RP_N} and the associated SL-DMRS configurations {D,, D₂, D_N} maybe received from an access node. The RxUE receives an indication of a particular RP (RPi) for a next communication (block 1347). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by a TxUE, intended for the RxUE, for example. The indication is received from the TxUE.

The RxUE receives scheduling information for the next communication between SL UEs (block 1349). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a DCI message from the access node. The RxUE receives signals in the particular RP (block 1351)· The signals may include data, reference signals, control signals, etc. The transmission is received in accordance with the SL-DMRS configuration. The RxUE performs an assessment of the RP or attributes (block 1353). The assessment may be performed in accordance with the signals (e.g., SL-DMRS, CSI-RS, other RS, data, control signals, etc.) received from the TxUE, for example. The assessment may be based on SINR measurements, SNR measurements, RSRP measurements, RSRQ

measurements, received signal power measurements, etc.

The RxUE performs a check to determine if an RP switch should take place (block 1355). An RP switch may take place for a variety of reasons, including, but not limited to meeting performance requirements, meeting error rate requirement, load balancing, etc. The RxUE identifies the resource (e.g., a different RP RPj or SL-DMRS configuration Dj) if one exists. If there are multiple resources, then the RxUE may randomly select a resource or use historical information (previous performance results using the resources, traffic on the resources, etc.) to select a resource, for example. If there is a different resource that more suitably meets the assessment, the RxUE transmits control signaling, such as a SCI including an ACK/NACK, CSI, etc. (block 1357). The control signaling includes the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be transmitted to the TxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs. In an embodiment, the control information is transmitted directly to the access node, in an UCI, for example. In an embodiment, the control information is transmitted to both the TxUE and the access node. The RxUE may return to block 1347 to receive an indication of the different resource and the operations 1340 may continue as described above, but for the different resource.

Figure 14A illustrates a flow diagram of generalized example operations 1400 occurring in a TxUE participating in SL communications and resource switching, with the SL UEs operating in mode 2. Operations 1400 maybe indicative of operations occurring in a TxUE as the TxUE participates in SL communications and resource (e.g., RP or SL- DMRS configuration) switching.

Operations 1400 begin with the TxUE obtaining RP configurations and associated SL- DMRS configurations (block 1405). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D , D₂, ..., DN} maybe received over RRC signaling. The RP configurations and the associated SL-DMRS configurations may be received from the network (such as a network entity (including an access node, a controller, or network function), or a database), or another SL UE. Alternatively, the RP configurations and the associated SL-DMRS configurations may be preconfigured. As an example, the RP configurations and the associated SL-DMRS configurations may be specified by a technical standard and saved in a memory of the TxUE. As another example, the RP configurations and the associated SL-DMRS configurations may be specified by an operator of the network and provided to the TxUE during an attachment procedure or a mobility procedure (such as a handover).

The TxUE transmits an indication of a particular RP (RPi) for a next communication (block 1407). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by the TxUE, intended for a RxUE, for example. The indication may be explicitly sent, such as an RP index in a message. The indication may be implicitly sent, wherein the RP index may be determined from resource(s) used to send the message. As an example, a time slot number or a RB location in frequency may serve as an implicit indication of the particular RP. The TxUE transmits scheduling information for the next communication between the SL UEs (block 1409). Because the access node is not involved in the communications between the SL UEs, the TxUE may select the resources for the next communication between the SL UEs and sends the scheduling information related to the resources. The scheduling information may be transmitted in an SCI, for example.

The TxUE transmits signals in the particular RP (block 1411). The signals may include data, reference signals, control signals, etc. The transmission is transmitted in accordance with the SL-DMRS configuration. The TxUE may receive control signaling, such as a SCI including an ACK/NACK, CSI, etc. The TxUE performs a check to determine if control signaling has been received (block 1413)· The control signaling may include the request requesting the selection of a different resource (e.g., a different RP RPj). The control information may be received from the RxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs.

If the TxUE has received the request requesting the selection of the different resource, the TxUE transmits an indication of the different resource (block 1415). Operations 1400 may continue as described above, but for the different resource. If the TxUE has not received the request requesting the selection of the different resource, operations 1400 terminate.

Figure 14B illustrates a flow diagram of example operations 1450 occurring in a RxUE participating in SL communications and resource switching, with the SL UEs operating in mode 2. Operations 1450 may be indicative of operations occurring in a RxUE as the RxUE participates in SL communications and resource (e.g., RP or SL-DMRS

configuration) switching.

Operations 1450 begin with the RxUE obtaining RP configurations and associated SL- DMRS configurations (block 1455). The RP configurations {RP , RP₂, ..., RPN} and the associated SL-DMRS configurations {D , D₂, ..., DN} maybe received over RRC signaling. The RP configurations and the associated SL-DMRS configurations may be received from the TxUE. The RP configurations and the associated SL-DMRS configurations maybe received from the network (such as a network entity (including an access node, a controller, or network function), or a database), or another SL UE. Alternatively, the RP configurations and the associated SL-DMRS configurations may be preconfigured. As an example, the RP configurations and the associated SL-DMRS configurations may be specified by a technical standard and saved in a memory of the RxUE. As another example, the RP configurations and the associated SL-DMRS configurations may be specified by an operator of the network and provided to the RxUE during an attachment procedure or a mobility procedure (such as a handover).

The RxUE receives an indication of a particular RP (RPi) for a next communication (block 1457). The indication may be an index to the particular RP in a list of RPs, for example. The next communication may be a PSSCH transmitted by a TxUE, intended for the RxUE, for example. The indication is received from the TxUE, for example. The RxUE receives scheduling information for the next communication between SL UEs (block 1459). The scheduling information includes information such as resources in RP, transmission mode, MCS, and so forth. The scheduling information may be received in a SCI message from the TxUE. The RxUE receives signals in the particular RP (block 1461). The signals may include data, reference signals, control signals, etc. The transmission is received in accordance with the SL-DMRS configuration. The RxUE performs assessments (block 1463). The assessments may be performed in accordance with the signals received from the TxUE, for example.

The RxUE performs a check to determine if an RP switch should take place (block 1465). An RP switch may take place for a variety of reasons, including, but not limited to meeting performance requirements, meeting error rate requirement, load balancing, etc. The RxUE identifies the resource (e.g., a different RP RPj or SL-DMRS configuration Dj) if one exists. If there are multiple resources, then the RxUE may randomly select a resource or use historical information (previous performance results using the resources, traffic on the resources, etc.) to select a resource, for example. If there is a different resource that more suitably meets the assessment, the RxUE transmits control signaling, such as a SCI including an ACK/NACK, CSI, etc. (block 1467). The control signaling includes the request requesting the selection of a different resource (e.g., a different RP RPj or SL-DMRS configuration Dj). The control information may be transmitted to the TxUE. The different resource may be for a subsequent communication between the SL UEs. The subsequent communication may be for a PSSCH, which is a new transmission or a retransmission of an earlier transmission, between the SL UEs. In an embodiment, the control information is transmitted directly to the access node, in an UCI, for example.

The RxUE may return to block 1457 to receive an indication of the different resource and the operations 1450 may continue as described above, but for the different resource.

Figure 15 illustrates an example communication system 1500. In general, the system 1500 enables multiple wireless or wired users to transmit and receive data and other content. The system 1500 may implement one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), or non-orthogonal multiple access (NOMA).

In this example, the communication system 1500 includes electronic devices (ED) 1510a- 1510c, radio access networks (RANs) 1520a- 1520b, a core network 1530, a public switched telephone network (PSTN) 1540, the Internet 1550, and other networks 1560. While certain numbers of these components or elements are shown in Figure 15, any number of these components or elements may be included in the system 1500. The EDs 15103-15100 are configured to operate or communicate in the system 1500. For example, the EDs i5ioa-i5ioc are configured to transmit or receive via wireless or wired communication channels. Each ED i5ioa-i5ioc represents any suitable end user device and may include such devices (or may be referred to) as a user equipment or device (UE), wireless transmit or receive unit (WTRU), mobile station, fixed or mobile subscriber unit, cellular telephone, personal digital assistant (PDA), smartphone, laptop, computer, touchpad, wireless sensor, or consumer electronics device.

The RANs i52oa-t52ob here include base stations I570a-t570b, respectively. Each base station I570a-t570b is configured to wirelessly interface with one or more of the EDs i5ioa-i5toc to enable access to the core network 1530, the PSTN 1540, the Internet 1550, or the other networks 1560. For example, the base stations I570a-t570b may include (or be) one or more of several well-known devices, such as a base transceiver station (BTS), a Node-B (NodeB), an evolved NodeB (eNodeB), a Next Generation (NG) NodeB (gNB), a Home NodeB, a Home eNodeB, a site controller, an access point (AP), or a wireless router. The EDs lsioa-isioc are configured to interface and communicate with the Internet 1550 and may access the core network 1530, the PSTN 1540, or the other networks 1560.

In the embodiment shown in Figure 15, the base station 1570a forms part of the RAN 1520a, which may include other base stations, elements, or devices. Also, the base station 1570b forms part of the RAN 1520b, which may include other base stations, elements, or devices. Each base station I570a-t570b operates to transmit or receive wireless signals within a particular geographic region or area, sometimes referred to as a“cell.” In some embodiments, multiple-input multiple-output (MIMO) technology maybe employed having multiple transceivers for each cell.

The base stations I570a-t570b communicate with one or more of the EDs i5ioa-i5ioc over one or more air interfaces 1590 using wireless communication links. The air interfaces 1590 may utilize any suitable radio access technology.

It is contemplated that the system 1500 may use multiple channel access functionality, including such schemes as described above. In particular embodiments, the base stations and EDs implement 5G New Radio (NR), LTE, LTE-A, or LTE-B. Of course, other multiple access schemes and wireless protocols may be utilized.

The RANs I520a-t520b are in communication with the core network 1530 to provide the EDs 1510a- 1510c with voice, data, application, Voice over Internet Protocol (VoIP), or other services. Understandably, the RANs I520a-t520b or the core network 1530 may be in direct or indirect communication with one or more other RANs (not shown). The core network 1530 may also serve as a gateway access for other networks (such as the PSTN 1540, the Internet 1550, and the other networks 1560). In addition, some or all of the EDs i5ioa-i5toc may include functionality for communicating with different wireless networks over different wireless links using different wireless technologies or protocols. Instead of wireless communication (or in addition thereto), the EDs may communicate via wired communication channels to a service provider or switch (not shown), and to the Internet 1550.

Although Figure 15 illustrates one example of a communication system, various changes may be made to Figure 15. For example, the communication system 1500 could include any number of EDs, base stations, networks, or other components in any suitable configuration.

Figures 16A and 16 B illustrate example devices that may implement the methods and teachings according to this disclosure. In particular, Figure 16A illustrates an example ED 1610, and Figure 16B illustrates an example base station 1670. These components could be used in the system 1500 or in any other suitable system.

As shown in Figure 16A, the ED 1610 includes at least one processing unit 1600. The processing unit 1600 implements various processing operations of the ED 1610. For example, the processing unit 1600 could perform signal coding, data processing, power control, input/output processing, or any other functionality enabling the ED 1610 to operate in the system 1500. The processing unit 1600 also supports the methods and teachings described in more detail above. Each processing unit 1600 includes any suitable processing or computing device configured to perform one or more operations. Each processing unit 1600 could, for example, include a microprocessor, microcontroller, digital signal processor, field programmable gate array, or application specific integrated circuit.

The ED 1610 also includes at least one transceiver 1602. The transceiver 1602 is configured to modulate data or other content for transmission by at least one antenna or NIC (Network Interface Controller) 1604. The transceiver 1602 is also configured to demodulate data or other content received by the at least one antenna 1604. Each transceiver 1602 includes any suitable structure for generating signals for wireless or wired transmission or processing signals received wirelessly or by wire. Each antenna 1604 includes any suitable structure for transmitting or receiving wireless or wired signals. One or multiple transceivers 1602 could be used in the ED 1610, and one or multiple antennas 1604 could be used in the ED 1610. Although shown as a single functional unit, a transceiver 1602 could also be implemented using at least one transmitter and at least one separate receiver.

The ED 1610 further includes one or more input/output devices 1606 or interfaces (such as a wired interface to the Internet 1550). The input/output devices 1606 facilitate interaction with a user or other devices (network communications) in the network. Each input/output device 1606 includes any suitable structure for providing information to or receiving information from a user, such as a speaker, microphone, keypad, keyboard, display, or touch screen, including network interface communications.

In addition, the ED 1610 includes at least one memory 1608. The memory 1608 stores instructions and data used, generated, or collected by the ED 1610. For example, the memory 1608 could store software or firmware instructions executed by the processing unit(s) 1600 and data used to reduce or eliminate interference in incoming signals. Each memory 1608 includes any suitable volatile or non-volatile storage and retrieval device(s). Any suitable type of memory may be used, such as random access memory (RAM), read only memory (ROM), hard disk, optical disc, subscriber identity module (SIM) card, memory stick, secure digital (SD) memory card, and the like.

As shown in Figure 16B, the base station 1670 includes at least one processing unit 1650, at least one transceiver 1652, which includes functionality for a transmitter and a receiver, one or more antennas 1656, at least one memory 1658, and one or more input/output devices or interfaces 1666. A scheduler, which would be understood by one skilled in the art, is coupled to the processing unit 1650. The scheduler could be included within or operated separately from the base station 1670. The processing unit 1650 implements various processing operations of the base station 1670, such as signal coding, data processing, power control, input/output processing, or any other functionality. The processing unit 1650 can also support the methods and teachings described in more detail above. Each processing unit 1650 includes any suitable processing or computing device configured to perform one or more operations. Each processing unit 1650 could, for example, include a microprocessor, microcontroller, digital signal processor, field programmable gate array, or application specific integrated circuit.

Each transceiver 1652 includes any suitable structure for generating signals for wireless or wired transmission to one or more EDs or other devices. Each transceiver 1652 further includes any suitable structure for processing signals received wirelessly or by wire from one or more EDs or other devices. Although shown combined as a transceiver 1652, a transmitter and a receiver could be separate components. Each antenna 1656 includes any suitable structure for transmitting or receiving wireless or wired signals. While a common antenna 1656 is shown here as being coupled to the transceiver 1652, one or more antennas 1656 could be coupled to the transceiver(s) 1652, allowing separate antennas 1656 to be coupled to the transmitter and the receiver if equipped as separate components. Each memory 1658 includes any suitable volatile or non-volatile storage and retrieval device(s). Each input/output device 1666 facilitates interaction with a user or other devices (network communications) in the network. Each input/output device 1666 includes any suitable structure for providing information to or receiving/providing information from a user, including network interface communications.

Figure 17 is a block diagram of a computing system 1700 that may be used for implementing the devices and methods disclosed herein. For example, the computing system can be any entity of UE, access network (AN), mobility management (MM), session management (SM), user plane gateway (UPGW), or access stratum (AS). Specific devices may utilize all of the components shown or only a subset of the components, and levels of integration may vary from device to device. Furthermore, a device may contain multiple instances of a component, such as multiple processing units, processors, memories, transmitters, receivers, etc. The computing system 1700 includes a processing unit 1702. The processing unit includes a central processing unit (CPU) 1714, memory 1708, and may further include a mass storage device 1704, a video adapter 1710, and an I/O interface 1712 connected to a bus 1720.

The bus 1720 may be one or more of any type of several bus architectures including a memory bus or memory controller, a peripheral bus, or a video bus. The CPU 1714 may comprise any type of electronic data processor. The memory 1708 may comprise any type of non-transitory system memory such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), or a combination thereof. In an embodiment, the memory 1708 may include ROM for use at boot-up, and DRAM for program and data storage for use while executing programs.

The mass storage 1704 may comprise any type of non-transitory storage device configured to store data, programs, and other information and to make the data, programs, and other information accessible via the bus 1720. The mass storage 1704 may comprise, for example, one or more of a solid state drive, hard disk drive, a magnetic disk drive, or an optical disk drive.

The video adapter 1710 and the I/O interface 1712 provide interfaces to couple external input and output devices to the processing unit 1702. As illustrated, examples of input and output devices include a display 1718 coupled to the video adapter 1710 and a mouse, keyboard, or printer 1716 coupled to the I/O interface 1712. Other devices may be coupled to the processing unit 1702, and additional or fewer interface cards may be utilized. For example, a serial interface such as Universal Serial Bus (USB) (not shown) may be used to provide an interface for an external device.

The processing unit 1702 also includes one or more network interfaces 1706, which may comprise wired links, such as an Ethernet cable, or wireless links to access nodes or different networks. The network interfaces 1706 allow the processing unit 1702 to communicate with remote units via the networks. For example, the network interfaces 1706 may provide wireless communication via one or more transmitters/transmit antennas and one or more receivers/ receive antennas. In an embodiment, the processing unit 1702 is coupled to a local-area network 1722 or a wide-area network for data processing and communications with remote devices, such as other processing units, the Internet, or remote storage facilities.

Figure 18 illustrates a block diagram of an embodiment processing system 1800 for performing methods described herein, which may be installed in a host device. As shown, the processing system 1800 includes a processor 1804, a memory 1806, and interfaces 1810-1814, which may (or may not) be arranged as shown in the figure. The processor 1804 may be any component or collection of components adapted to perform

computations and/or other processing related tasks, and the memory 1806 may be any component or collection of components adapted to store programming and/or instructions for execution by the processor 1804. In an embodiment, the memory 1806 includes a non-transitoiy computer readable medium. The interfaces 1810, 1812, 1814 may be any component or collection of components that allow the processing system 1800 to communicate with other devices/components and/or a user. For example, one or more of the interfaces 1810, 1812, 1814 may be adapted to communicate data, control, or management messages from the processor 1804 to applications installed on the host device and/or a remote device. As another example, one or more of the interfaces 1810, 1812, 1814 may be adapted to allow a user or user device (e.g., personal computer (PC), etc.) to interact/communicate with the processing system 1800. The processing system 1800 may include additional components not depicted in the figure, such as long term storage (e.g., non-volatile memory, etc.).

In some embodiments, the processing system 1800 is included in a network device that is accessing, or part otherwise of, a telecommunications network. In one example, the processing system 1800 is in a network-side device in a wireless or wireline

telecommunications network, such as a base station, a relay station, a scheduler, a controller, a gateway, a router, an applications server, or any other device in the telecommunications network. In other embodiments, the processing system 1800 is in a user-side device accessing a wireless or wireline telecommunications network, such as a mobile station, a user equipment (UE), a personal computer (PC), a tablet, a wearable communications device (e.g., a smartwatch, etc.), or any other device adapted to access a telecommunications network.

In some embodiments, one or more of the interfaces 1810, 1812, 1814 connects the processing system 1800 to a transceiver adapted to transmit and receive signaling over the telecommunications network. Figure 19 illustrates a block diagram of a transceiver 1900 adapted to transmit and receive signaling over a telecommunications network. The transceiver 1900 may be installed in a host device. As shown, the transceiver 1900 comprises a network-side interface 1902, a coupler 1904, a transmitter 1906, a receiver 1908, a signal processor 1910, and a device-side interface 1912. The network-side interface 1902 may include any component or collection of components adapted to transmit or receive signaling over a wireless or wireline telecommunications network.

The coupler 1904 may include any component or collection of components adapted to facilitate bi-directional communication over the network-side interface 1902. The transmitter 1906 may include any component or collection of components (e.g., up- converter, power amplifier, etc.) adapted to convert a baseband signal into a modulated carrier signal suitable for transmission over the network-side interface 1902. The receiver 1908 may include any component or collection of components (e.g., down -converter, low noise amplifier, etc.) adapted to convert a carrier signal received over the network-side interface 1902 into a baseband signal. The signal processor 1910 may include any component or collection of components adapted to convert a baseband signal into a data signal suitable for communication over the device-side interface(s) 1912, or vice-versa. The device-side interface(s) 1912 may include any component or collection of components adapted to communicate data-signals between the signal processor 1910 and components within the host device (e.g., the processing system 1800, local area network (LAN) ports, etc.).

The transceiver 1900 may transmit and receive signaling over any type of

communications medium. In some embodiments, the transceiver 1900 transmits and receives signaling over a wireless medium. For example, the transceiver 1900 may be a wireless transceiver adapted to communicate in accordance with a wireless

telecommunications protocol, such as a cellular protocol (e.g., long-term evolution (LTE), etc.), a wireless local area network (WLAN) protocol (e.g., Wi-Fi, etc.), or any other type of wireless protocol (e.g., Bluetooth, near field communication (NFC), etc.). In such embodiments, the network-side interface 1902 comprises one or more

antenna/radiating elements. For example, the network-side interface 1902 may include a single antenna, multiple separate antennas, or a multi-antenna array configured for multi-layer communication, e.g., single input multiple output (SIMO), multiple input single output (MISO), multiple input multiple output (MIMO), etc. In other

embodiments, the transceiver 1900 transmits and receives signaling over a wireline medium, e.g., twisted-pair cable, coaxial cable, optical fiber, etc. Specific processing systems and/or transceivers may utilize all of the components shown, or only a subset of the components, and levels of integration may vary from device to device. It should be appreciated that one or more steps of the embodiment methods provided herein may be performed by corresponding units or modules. For example, a signal may be transmitted by a transmitting unit or a transmitting module. A signal may be received by a receiving unit or a receiving module. A signal may be processed by a processing unit or a processing module. Other steps may be performed by a performing unit or module, or a determining unit or module. The respective units or modules may be hardware, software, or a combination thereof. For instance, one or more of the units or modules may be an integrated circuit, such as field programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs).

Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope of the disclosure as defined by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A method comprising:

indicating, by a first device, a first resource pool (RP) associated with a first physical sidelink shared channel (PSSCH);

transmitting, by the first device, to a second device, signals on the first PSSCH in the first RP;

receiving, by the first device, from the second device, a RP switch request including an indication of a second RP; and

transmitting, by the first device, to the second device, signals on a second PSSCH in the second RP.

2. The method of claim l, further comprising receiving, by the first device, from an access node, scheduling information for the first PSSCH.

3. The method of any one of claims t-2, the RP switch request being signaled in a sidelink control information (SCI) message.

4. The method of claim 2, further comprising:

transmitting, by the first device, to the access node, the RP switch request; and receiving, by the first device, from the access node, the indication of the second RP for the second PSSCH.

5. The method of claim l, further comprising transmitting, by the first device, to the second device, scheduling information for the first PSSCH.

6. The method of any one of claims l or 5, further comprising transmitting, by the first device, to the second device, the indication of the second RP for the second PSSCH.

7. The method of claim 6, the indication of the second RP being transmitted in an SCI message.

8. The method of any one of claims 1-6, the signals comprising data and a sidelink demodulation reference signal (SL-DMRS).

9. The method of any one of claims 1-8, an indication of the first RP comprising an index associated with the first RP. to. The method of any one of claims 1-9, the first device comprising a transmitting sidelink user equipment (SL UE) and the second device comprising a receiving SL UE.

11. The method of any one of claims l-io, further comprising obtaining, by the first device, a RP configuration.

12. A method comprising:

receiving, by a second device, from a first device, an indication of a first resource pool (RP) associated with a first physical sidelink shared channel (PSSCH);

receiving, by the second device, from the first device, signals on the first PSSCH in the first RP;

performing, by the second device, channel measurements in accordance with the signals; and

determining, by the second device, that a second RP meets a switching criteria, and based thereon transmitting, by the second device, to the first device, a RP switch request including an indication of a second RP associated with the second RP.

13. The method of claim 12, further comprising determining, by the second device, that the second RP meets the switching criteria, and based thereon receiving, by the second device, from the first device, signals on a second PSSCH in the second RP.

14. The method of any one of claim 12-13, further comprising receiving, by the second device, from the first device, scheduling information for the first PSSCH.

15. The method of any one of claims 12-14, further comprising receiving, by the second device, from the first device, scheduling information for the first PSSCH.

16. The method of any one of claims 12-15, the signals comprising data and a sidelink demodulation reference signal (SL-DMRS), and performing channel measurements comprising performing channel measurements in accordance with the SL-DMRS.

17. The method of any one of claims 12-16, the first device comprising a transmitting sidelink user equipment (SL UE) and the second device comprising a receiving SL UE.

18. The method of any one of claims 12-17, further comprising obtaining, by the second device, a RP configuration.

19. A first device comprising :

a non-transitory memory storage comprising instructions; and

one or more processors in communication with the memory storage, wherein the one or more processors execute the instructions to:

indicate a first resource pool (RP) associated with a first physical sidelink shared channel (PSSCH); transmit, to a second device, signals on the first PSSCH in the first RP; receive, from the second device, a RP switch request including an indication of a second RP; and

transmit, to the second device, signals on a second PSSCH in the second RP.

20. The first device of claim 19, the one or more processors further executing the instructions to receive, from an access node, scheduling information for the first PSSCH.

21. The first device of any one of claims 19-20, the RP switch request being signaled in a sidelink control information (SCI) message. 22. The first device of claim 20, the one or more processors further executing the instructions to transmit, to the access node, the RP switch request; and receive, from the access node, the indication of the second RP for the second PSSCH.

23. The first device of claim 19, the one or more processors further executing the instructions to transmit, to the second device, scheduling information for the first PSSCH.

24. The first device of any one of claims 19 or 23, the one or more processors further executing the instructions to transmit, to the second device, the indication of the second RP for the second PSSCH.

25. The first device of claim 24, the indication of the second RP being transmitted in an SCI message.

26. The first device of any one of claims 19-24, the signals comprising data and a sidelink demodulation reference signal (SL-DMRS).

27. The first device of any one of claims 19-26, an indication of the first RP comprising an index associated with the first RP. 28. The first device of any one of claims 19-27, the first device comprising a transmitting sidelink user equipment (SL UE) and the second device comprising a receiving SL UE.

29. The first device of any one of claims 19-28, the one or more processors further executing the instructions to obtain a RP configuration.

30. A first device comprising :

a non-transitory memory storage comprising instructions; and

receive, from a second device, an indication of a first resource pool (RP) associated with a first physical sidelink shared channel (PSSCH);

receive, from the second device, signals on the first PSSCH in the first RP; perform channel measurements in accordance with the signals; and determine that a second RP meets a switching criteria, and based thereon transmitting, to the second device, a RP switch request including an indication of a second RP associated with the second RP.

31. The first device of claim 30, the one or more processors further executing the instructions to determine that the second RP meets the switching criteria, and based thereon receive, from the second device, signals on a second PSSCH in the second RP.

32. The first device of any one of claims 30-31, the one or more processors further executing the instructions to receive, from the second device, scheduling information for the first PSSCH.

33. The first device of any one of claims 30-32, the one or more processors further executing the instructions to receive, from the second device, scheduling information for the first PSSCH.

34. The first device of any one of claims 30-33, the signals comprising data and a sidelink demodulation reference signal (SL-DMRS), and performing channel measurements comprising performing channel measurements in accordance with the SL-DMRS.

35. The first device of any one of claims 30-34, the second device comprising a transmitting sidelink user equipment (SL UE) and the first device comprising a receiving SL UE.

36. The first device of any one of claims 30-35, the one or more processors further executing the instructions to obtain a RP configuration.