WO2025207991A1

WO2025207991A1 - Method and apparatus for aggregated transmissions of srs

Info

Publication number: WO2025207991A1
Application number: PCT/US2025/021948
Authority: WO
Inventors: Tao Deng; Tuong Hoang; Jongwoo HONG; Benoit Pelletier; Virgile Garcia
Original assignee: InterDigital Patent Holdings Inc
Current assignee: InterDigital Patent Holdings Inc
Priority date: 2024-03-28
Filing date: 2025-03-28
Publication date: 2025-10-02
Anticipated expiration: 2026-09-28

Abstract

A method may be implemented by a wireless transmit/receive unit (WTRU). The method may include receiving a reference signal (RS) transmission configuration and determining a set of aggregated transmission parameters to perform aggregated RS transmissions. The determination may be based on the RS transmission configuration. The set of aggregated RS transmission parameters may be sent to one or more of a network or other WTRUs in an aggregation group. An indication to transmit an aggregated RS may be received. An indication to transmit the aggregated RS to the other WTRUs in the aggregation group may be sent. The aggregated RS may be transmitted using the determined set of transmission parameters and the RS transmission configuration.

Description

METHOD AND APPARATUS FOR AGGREGATED TRANSMISSIONS OF SRS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of United States Provisional Application No. 63/570,879 filed on March 28, 2024, the entire contents of which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Application for 5G and beyond is expanding in many vertical directions such as, e.g., XR, industrial loT, intelligent transportation system and so on. Such new scenario imposes new service requirements with reasonable resource and power efficiency such as such as ultra-high UL data rate, ultra-low latency, and high reliability. Some services such as XR, VR/AR may even require a tight synchronization among data flows from different devices (e.g., gloves, glasses, etc.) running a single application layer.

SUMMARY

[0003] A wireless transmit/receive unit (WTRU) may be described herein. The WTRU may include a processor. The processor may be configured to receive a reference signal (RS) transmission configuration and determine a set of aggregated transmission parameters to perform aggregated RS transmissions. The determination may be based on the RS transmission configuration. The processor may be configured to send the set of aggregated RS transmissions parameters to one or more of a network or other WTRUs in an aggregation group, receive an indication to transmit an aggregated RS transmission, send the indication to transmit the aggregated RS transmission to the other WTRUs in the aggregation group, and transmit the aggregated RS transmission using the determined set of transmission parameters and the RS transmission configuration.

[0004] The set of aggregated RS transmission parameters may include one or more of a subset of aggregated WTRUs, transmission resources, an antenna port mapping, or a transmission power for each WTRU in the aggregation group.

[0005] The processor may be configured to distribute the transmission power across one or more WTRUs in the aggregation group based on one or more of received pathloss information, maximum transmit power of each WTRU in the aggregation group, or a power scaling factor associated with the aggregated RS transmission.

[0006] The set of aggregated RS transmission parameters may include the antenna port mapping. [0007] The processor may be configured to determine the antenna port mapping of antenna ports of different WTRUs in the aggregation group to respective RS ports based on a received configuration indicating an RS port allocation scheme for aggregated transmission.

[0008] The processor may be configured to receive a set of non-aggregated transmission parameters to perform non-aggregated RS transmissions, receive an additional indication that indicates whether to transmit the aggregated RS transmission or the non-aggregated RS transmissions, and determine whether to use the set of aggregated transmission parameters or the set of non-aggregated transmission parameters to perform a transmission based on the additional indication.

[0009] The indication to transmit the aggregated RS transmission may include one or more of an RS resource identifier (ID), a radio network temporary identifier (RNTI), or an indication source.

[0010] The indication to transmit the aggregated RS transmission may include an RS resource ID. The RS resource ID may correspond to an RS resource set configured for an aggregation group transmission mode. The RS may be a sounding reference signal (SRS).

[0011] The processor may be configured to select an RS resource set based on a received aggregation configuration, wherein the aggregation configuration indicates an RS usage mode associated with the aggregation group, to determine the set of transmission parameters.

[0012] The processor may be configured to determine the set of transmission parameters by selecting a subset of WTRUs for aggregated RS transmission based on one or more of an indication of collocation, an indication of synchronization timing, or an indication of supported antenna ports received from a group coordinator.

[0013] A method may be implemented by a wireless transmit/receive unit (WTRU). The method may include receiving a reference signal (RS) transmission configuration and determining a set of aggregated transmission parameters to perform aggregated RS transmissions. The determination may be based on the RS transmission configuration. The set of aggregated RS transmission parameters may be sent to one or more of a network or other WTRUs in an aggregation group. An indication to transmit an aggregated RS transmission may be received. An indication to transmit the aggregated RS transmission to the other WTRUs in the aggregation group may be sent. The aggregated RS transmission may be transmitted using the determined set of transmission parameters and the RS transmission configuration.

[0014] The set of aggregated RS transmission parameters may include one or more of a subset of aggregated WTRUs, transmission resources, an antenna port mapping, or a transmission power for each WTRU in the aggregation group. [0015] The method may include distributing the transmission power across WTRUs based on one or more of received pathloss information, maximum transmit power of each WTRU, or a power scaling factor associated with the aggregated RS transmission.

[0016] The set of aggregated RS transmission parameters may include the antenna port mapping.

[0017] The method may include determining the antenna port mapping of antenna ports of different WTRUs in the aggregation group to respective RS ports based on a received configuration indicating an RS port allocation scheme for the aggregated RS transmission.

[0018] The method may include receiving a set of non-aggregated transmission parameters to perform non-aggregated RS transmissions, receiving an additional indication that indicates whether to transmit the aggregated RS transmission or the non-aggregated RS transmissions, and determining whether to use the set of aggregated transmission parameters or the set of non-aggregated transmission parameters to perform a transmission based on the additional indication.

[0019] The indication to transmit the aggregated RS transmission may include one or more of an RS resource identifier (ID), a radio network temporary identifier (RNTI), or an indication source.

[0020] The indication to transmit the aggregated RS transmission may include an RS resource ID. The RS resource ID may correspond to an RS resource set configured for an aggregation group transmission mode. The RS may be a sounding reference signal (SRS).

[0021] The method may include selecting an RS resource set based on a received aggregation configuration. The aggregation configuration may indicate an RS usage mode associated with the aggregation group, to determine the set of transmission parameters.

[0022] The method may include determining the set of transmission parameters by selecting a subset of WTRUs for aggregated RS transmission based on one or more of an indication of collocation, an indication of synchronization timing, or an indication of supported antenna ports received from a group coordinator.

[0023] A wireless transmit/receive unit (WTRU) may include a processor and memory. The processor and memory may be configured to receive a configuration as part of an aggregation group. The processor and memory may be configured to determine a set of transmission parameters to perform aggregated SRS transmissions. The determination may be based on the received configuration. The processor and memory may be configured to send the set of aggregated SRS transmissions parameters.

[0024] The processor and memory may be configured to receive an indication to transmit an aggregated SRS. The processor and memory may be configured to send the aggregated SRS transmission indication. The processor and memory may be configured to transmit the aggregated SRS using the set of transmission parameters and the received configuration.

[0025] The received configuration may include one or more SRS resources configuration and/or SRS sets configuration. The received configuration may include one or more transmissions configured with an aggregation scheme and/or transmissions associated with an SRS. The received configuration may include one or more indications about other member WTRUs.

[0026] The determined set of transmission parameters may include one or more of a selected WTRU subset, a selected SRS set, an antenna-port mapping, and/or a transmit power.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented.

[0028] FIG. 1 B is a system diagram illustrating an example wireless transmit/receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A according to an embodiment.

[0029] FIG. 1C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communications system illustrated in FIG. 1 A according to an embodiment.

[0030] FIG. 1 D is a system diagram illustrating a further example RAN and a further example CN that may be used within the communications system illustrated in FIG. 1 A according to an embodiment.

[0031] FIG. 2 illustrates an example scenario for aggregated reference signal (RS) (e.g., (SRS)) transmission.

[0032] FIG. 3 illustrates an example method for aggregated reference signal (RS) (e.g., (SRS)) transmission.

DETAILED DESCRIPTION

[0033] FIG. 1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems 100 may employ 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), zero-tail unique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0034] As shown in FIG. 1 A, the communications system 100 may include wireless transmit/receive units (WTRUs) 102a, 102b, 102c, 102d, a RAN 104/113, a CN 106/115, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and/or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and/or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a “station” and/or a “ST A”, may be configured to transmit and/or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g, remote surgery), an industrial device and applications (e.g, a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c and 102d may be interchangeably referred to as a WTRU. Further, any description herein that is described with reference to a UE may be equally applicable to a WTRU (or vice versa). For example, a WTRU may be configured to perform any of the processes or procedures described herein as being performed by a UE (or vice versa).

[0035] The communications systems 100 may also include a base station 114a and/or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106/115, the I nternet 110, and/or the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and/or network elements.

[0036] The base station 114a may be part of the RAN 104/113, which may also include other base stations and/or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and/or the base station 114b may be configured to transmit and/or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for a wireless service to a specific geographical area that may be relatively fixed or that may change over time. The cell may further be divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and/or receive signals in desired spatial directions.

[0037] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0038] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104/113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 115/116/117 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and/or High-Speed UL Packet Access (HSUPA). [0039] I n an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/or LTE-Advanced Pro (LTE-A Pro).

[0040] I n an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR Radio Access , which may establish the air interface 116 using New Radio (NR).

[0041] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for instance using dual connectivity (DC) principles. Thus, the air interface utilized by WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and/or transmissions sent to/from multiple types of base stations (e.g, a eNB and a gNB).

[0042] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e, Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0043] The base station 114b in FIG. 1 A may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g, for use by drones), a roadway, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not be required to access the Internet 110 via the CN 106/115. [0044] The RAN 104/113 may be in communication with the CN 106/115, which may be any type of network configured to provide voice, data, applications, and/or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106/115 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and/or perform high-level security functions, such as user authentication. Although not shown in FIG. 1A, it will be appreciated that the RAN 104/113 and/or the CN 106/115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104/113 or a different RAT. For example, in addition to being connected to the RAN 104/113, which may be utilizing a NR radio technology, the CN 106/115 may also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0045] The CN 106/115 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and/or the other networks 112. The PSTN 108 may include circuit- switched telephone networks that provide plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and/or the internet protocol (IP) in the TCP/IP internet protocol suite. The networks 112 may include wired and/or wireless communications networks owned and/or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104/113 or a different RAT.

[0046] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0047] FIG. 1 B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1 B, the WTRU 102 may include a processor 118, a transceiver 120, a transmit/receive element 122, a speaker/microphone 124, a keypad 126, a display/touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and/or other peripherals 138, among others. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0048] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input/output processing, and/or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit/receive element 122. While FIG. 1B depicts the processor 118 and the transceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0049] The transmit/receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g. , the base station 114a) over the air interface 116. For example, in one embodiment, the transmit/receive element 122 may be an antenna configured to transmit and/or receive RF signals. In an embodiment, the transmit/receive element 122 may be an emitter/detector configured to transmit and/or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit/receive element 122 may be configured to transmit and/or receive both RF and light signals. It will be appreciated that the transmit/receive element 122 may be configured to transmit and/or receive any combination of wireless signals.

[0050] Although the transmit/receive element 122 is depicted in FIG. 1 B as a single element, the WTRU 102 may include any number of transmit/receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit/receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0051] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit/receive element 122 and to demodulate the signals that are received by the transmit/receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11, for example. [0052] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and/or the removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0053] The processor 118 may receive power from the power source 134, and may be configured to distribute and/or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0054] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station (e.g., base stations 114a, 114b) and/or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by way of any suitable locationdetermination method while remaining consistent with an embodiment.

[0055] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and/or hardware modules that provide additional features, functionality and/or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs and/or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a Virtual Reality and/or Augmented Reality (VR/AR) device, an activity tracker, and the like. The peripherals 138 may include one or more sensors, the sensors may be one or more of a gyroscope, an accelerometer, a hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor; an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and/or a humidity sensor.

[0056] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the UL (e.g., for transmission) and downlink (e.g., for reception) may be concurrent and/or simultaneous. The full duplex radio may include an interference management unit 139 to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WRTU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the downlink (e.g., for reception)).

[0057] FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0058] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and/or receive wireless signals from, the WTRU 102a.

[0059] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and/or DL, and the like. As shown in FIG. 1 C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0060] The CN 106 shown in FIG. 1 C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and/or operated by an entity other than the CN operator.

[0061] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation/deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and/or WCDMA.

[0062] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 may generally route and forward user data packets to/from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring user planes during inter- eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0063] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0064] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and/or wireless networks that are owned and/or operated by other service providers.

[0065] Although the WTRU is described in FIGS. 1 A-1 D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (e.g., temporarily or permanently) wired communication interfaces with the communication network.

[0066] In representative embodiments, the other network 112 may be a WLAN.

[0067] A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have an access or an interface to a Distribution System (DS) or another type of wired/wireless network that carries traffic in to and/or out of the BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. The traffic between ST As within a BSS may be considered and/or referred to as peer-to- peer traffic. The peer-to-peer traffic may be sent between (e.g. , directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11 e DLS or an 802.11 z tunneled DLS (TDLS). A WLAN using an Independent BSS (I BSS) mode may not have an AP, and the STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an “ad- hoc” mode of communication.

[0068] When using the 802.11 ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling. The primary channel may be the operating channel of the BSS and may be used by the STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) may be implemented, for example in in 802.11 systems. For CSMA/CA, the STAs (e.g., every STA), including the AP, may sense the primary channel. If the primary channel is sensed/detected and/or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g, only one station) may transmit at any given time in a given BSS.

[0069] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0070] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately. The streams may be mapped on to the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0071] Sub 1 GHz modes of operation are supported by 802.11 af and 802.11 ah. The channel operating bandwidths, and carriers, are reduced in 802.11 af and 802.11 ah relative to those used in 802.11 n, and 802.11ac. 802.11 af supports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11 ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11 ah may support Meter Type Control/Machine- Type Communications, such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, for example, limited capabilities including support for (e.g., only support for) certain and/or limited bandwidths. The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0072] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802.11 n, 802.11 ac, 802.11 af, and 802.11 ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and/or limited by a ST A, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11 ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 1 MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes. Carrier sensing and/or Network Allocation Vector (NAV) settings may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which supports only a 1 MHz operating mode), transmitting to the AP, the entire available frequency bands may be considered busy even though a majority of the frequency bands remains idle and may be available.

[0073] In the United States, the available frequency bands, which may be used by 802.11 ah, are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11 ah is 6 MHz to 26 MHz depending on the country code.

[0074] FIG. 1 D is a system diagram illustrating the RAN 113 and the CN 115 according to an embodiment. As noted above, the RAN 113 may employ an NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the CN 115.

[0075] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and/or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to, and/or receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and/or gNB 180c).

[0076] The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and/or OFDM subcarrier spacing may vary for different transmissions, different cells, and/or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing varying number of OFDM symbols and/or lasting varying lengths of absolute time).

[0077] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and/or a non-standalone configuration. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without also accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with/connect to gNBs 180a, 180b, 180c while also communicating with/connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In the non-standalone configuration, eNode-Bs 160a, 160b, 160c may serve as a mobility anchor for WTRUs 102a, 102b, 102c and gNBs 180a, 180b, 180c may provide additional coverage and/or throughput for servicing WTRUs 102a, 102b, 102c.

[0078] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and/or DL, support of network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG. 1D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0079] The CN 115 shown in FIG. 1 D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While each of the foregoing elements are depicted as part of the CN 115, it will be appreciated that any of these elements may be owned and/or operated by an entity other than the CN operator.

[0080] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different PDU sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of NAS signaling, mobility management, and the like. Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types of services being utilized WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, and/or the like. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and/or non-3GPP access technologies such as WiFi. [0081] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 115 via an N11 interface. The SMF 183a, 183b may also be connected to a UPF 184a, 184b in the CN 115 via an N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating WTRU IP address, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notifications, and the like. A PDU session type may be IP-based, non-IP based, Ethernet-based, and the like.

[0082] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, and the like.

[0083] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and/or wireless networks that are owned and/or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local Data Network (DN) 185a, 185b through the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0084] In view of Figures 1A-1 D, and the corresponding description of Figures 1A-1 D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-ab, UPF 184a-b, SMF 183a-b, DN 185a-b, and/or any other device(s) described herein, may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more, or all, of the functions described herein. For example, the emulation devices may be used to test other devices and/or to simulate network and/or WTRU functions.

[0085] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and/or in an operator network environment. For example, the one or more emulation devices may perform the one or more, or all, functions while being fully or partially implemented and/or deployed as part of a wired and/or wireless communication network in order to test other devices within the communication network. The one or more emulation devices may perform the one or more, or all, functions while being temporarily implemented/deployed as part of a wired and/or wireless communication network. The emulation device may be directly coupled to another device for purposes of testing and/or may performing testing using over-the-air wireless communications.

[0086] The one or more emulation devices may perform the one or more, including all, functions while not being implemented/deployed as part of a wired and/or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and/or a non-deployed (e.g., testing) wired and/or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and/or wireless communications via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation devices to transmit and/or receive data.

[0087] The application for 5G and beyond may expand in multiple vertical directions, including extended reality (XR), industrial Internet of Things (loT), and intelligent transportation systems. Such scenarios may impose new service requirements while maintaining reasonable resource and power efficiency, such as ultra-high uplink (UL) data rates, ultra-low latency, and high reliability. Certain services, including XR and virtual reality/augmented reality (VR/AR), may require tight synchronization among data flows from multiple devices (e.g., gloves, glasses, and/or other devices) operating within a single application layer.

[0088] Wireless transmit/receive units (WTRUs) in a network may be grouped to assist each other and/or perform collaborative tasks and procedures, forming an aggregation group. The group may be defined either statically or dynamically, based on the presence of WTRUs in proximity, support for aggregation and/or collaborative features, or a shared data interest among WTRUs (e.g., WTRUs belonging to the same user, subscriber, and/or set of devices). Tasks performed by WTRUs in an aggregation group may involve aspects of communication protocols in both higher-layer and lower-layer protocol stacks. In some instances, collaboration may aim to collect and regroup distributed knowledge and/or decisions to improve overall system performance. In other instances, a WTRU may perform tasks on behalf of another WTRU in a delegative manner. The network may utilize WTRU aggregation to take advantage of multiple Uu links and sidelinks among WTRUs to dynamically route uplink and/or downlink data while considering transmission power, channel conditions, and/or quality of service (QoS) requirements for the data. This approach may enable efficient group management while maintaining QoS and/or quality of experience (QoE) for the service. Aggregation and/or collaboration may also involve a WTRU relaying data, either to the network or to another WTRU.

[0089] Lower-layer aggregation (e.g., medium access control (MAC) and/or physical (PHY) layer aggregation) may allow the network to utilize combining gain at lower layers to enhance system performance. Additionally, physical downlink shared channel (PDSCH) and/or physical uplink shared channel (PUSCH) transmissions may be conducted over the same resources to reduce resource overhead and enhance WTRU antenna capabilities. For example, joint transmissions utilizing single-frequency network (SFN) transmission may enable multiple WTRUs to transmit the same signal over the same resource, thereby increasing received power at a gNodeB (gNB) and improving decoding performance due to lower-layer combining gain. On the downlink (DL) side, WTRUs may receive transmissions and either combine physical signals before decoding or decode and exchange results afterward. Hybrid automatic repeat request (HARQ) retransmissions may be avoided as long as a transmission on at least one WTRU is successful, which may reduce latency and eliminate unnecessary retransmissions. WTRUs may also employ distributed transmission and/or reception techniques, similar to distributed multiple-input multipleoutput (MIMO), to leverage channel diversity among WTRUs (e.g., by transmitting and/or receiving different data layers). WTRUs in an aggregation group may be considered as a single logical device, with interactions and configurations managed within the group (e.g., through a group coordinator (GC)).

[0090] In current Third Generation Partnership Project (3GPP) standards, the network may schedule and prepare Uu transmissions based on reference signals (RSs) measured to estimate the channel quality between a WTRU and a gNB. Sounding reference signals (SRSs) may be utilized as uplink reference signals for uplink channel estimation and may also be used for downlink estimation and/or beam management. Reference signal (RS) (e.g., sounding reference signal (SRS)) transmissions may be configured individually for each WTRU, and a WTRU may receive, via radio resource control (RRC) configuration, one or more SRS resource sets including one or more SRS resources, indicating how to transmit SRS (e.g., timing, frequency, and/or cyclic shifts).

[0091] Enhancements to the transmission of aggregated WTRUs may involve enabling joint and/or aggregated SRS transmissions, allowing the network to obtain improved channel measurements for aggregated WTRUs. The specification may describe methods for supporting SRS transmissions applicable to WTRUs operating as a single unit within an aggregation group. The specification may further detail approaches for determining SRS transmission parameters for a set of WTRUs to coordinate transmissions and prevent ambiguity (e.g., antenna-to-port mapping and/or transmit power allocation for multiple WTRUs).

[0092] Under existing standards, in cases where WTRUs perform aggregated transmissions, each WTRU may transmit SRS separately, and the corresponding aggregated channel may not be directly measured by the network. Consequently, the network may lack an accurate measurement of the aggregated transmission. Furthermore, WTRU aggregation may be managed at the WTRU side (e.g., by a GC), and the network may not be aware of ongoing aggregation configurations, which may be modified and/or updated dynamically.

[0093] Additionally, from the WTRU perspective, SRS transmissions may involve internal implementation components (e.g., antenna-to-SRS port mapping and/or SRS power control) that may need to be managed collectively across WTRUs in an aggregation group. Without coordination, ambiguity may arise concerning the sharing of SRS ports and/or resources among WTRUs. Thus, coordination between WTRUs may be required to facilitate proper SRS transmission.

[0094] Methods for determining and utilizing aggregation-specific transmission parameters for SRS transmission may be based on a collection of configurations and/or information related to WTRUs within an aggregation group.

[0095] A wireless transmit/receive unit (WTRU) may receive a pre-config uration as part of an aggregation group. The configuration may include one or more sounding reference signal (SRS) resource(s) and/or set(s), specifying the resource configuration and the configured number of ports. Additionally and/or alternatively, the WTRU may be configured for transmission with an aggregation scheme (e.g., non-single frequency network (non-SFN) transmission) associated with an SRS, such as an uplink (UL) grant with an SRS indication. The WTRU may also receive indications (e.g., from a group coordinator (GC)) regarding other WTRUs in the aggregation group, including information on the number of supported antenna ports, supported aggregation schemes, and/or collocation indications (e.g., relative positions and/or synchronization timing between WTRUs).

[0096] A WTRU may determine a set of transmission parameters to perform aggregated SRS transmissions based on the received configuration and indications. The transmission parameters may include the SRS resource(s) and/or set(s) identifiers (IDs) for aggregation-based transmission, which may be determined based on the configured aggregated transmissions and the associated SRS indication. Additionally and/or alternatively, the WTRU may determine a subset of WTRUs to perform the aggregated SRS transmission. The WTRU may select a set of WTRUs based on WTRU configurations within the aggregation group. For example, for an SRS configured with four transmission (TX) ports and associated with a non-SFN transmission, the WTRU may select two WTRUs, each having two TX ports, that are not collocated and support non-SFN aggregated transmission.

[0097] The WTRU may determine a mapping between the antenna ports of the selected subset of WTRUs and the configured SRS ports. For example, the WTRU may map two antenna ports of a first WTRU to the first two SRS ports and two antenna ports of a second WTRU to the third and fourth SRS ports. Additionally and/or alternatively, the WTRU may determine aggregated SRS transmission power parameters based on the SRS transmit power of the WTRUs. The WTRU may determine the transmit power for another WTRU’s port based on its transmit power control, distributing the power equally among WTRUs.

[0098] A WTRU may send the aggregated SRS resource and/or the set of transmission parameters (e.g., port mapping and/or transmission power) to the determined subset of WTRUs and/or to the network. In cases where a WTRU receives an indication to transmit an aggregated SRS, the WTRU may send an SRS transmission indication to the WTRUs determined for the aggregated transmission. The WTRU may receive the indication via MAC activation or downlink control information (DCI) commands for semi-persistent and/or aperiodic SRS and may send the indication via sidelink MAC (SL-MAC) or sidelink control information (SCI), respectively.

[0099] A WTRU may transmit the SRSs using the determined set of aggregated transmission parameters and the received configuration. This coordination among WTRUs may enable the transmission of reference signals (RSs) that correctly represent the aggregated UL channel, allowing the network to perform accurate measurements and improve scheduling. The WTRU may collect and process information from multiple sources to determine transmission parameters for the aggregation configuration and avoid ambiguity in transmission assignments. For example, the WTRU may determine which SRS is used as a reference for an incoming transmission and/or assess the antenna and power capabilities of WTRUs within the aggregation group.

[0100] A group of WTRUs may form an aggregation group, which may include a GC. The GC may manage certain group functions and centralize information that may not be available to the network. The aggregation group may be predetermined but may also be dynamically updated. The aggregation group may consist of WTRUs sharing a common data interest, belonging to the same user and/or subscriber, being part of the same set of devices, and/or being in close proximity to each other. Example use cases may include XR, loT, and/or wearable devices.

[0101] For WTRU aggregation in UL transmission and downlink (DL) reception, a WTRU may perform UL transmission and/or DL reception with the support of one or more assistant WTRUs to take advantage of WTRU diversity gain in transmission and/or reception. A WTRU may be configured for aggregation and may be assigned SRS resources and/or sets based on its capabilities. The WTRU may report its aggregation configuration and/or support to the network, for example, via WTRU capability indications, radio resource control (RRC) (re)configuration, UL MAC control elements (MAC-CE), and/or physical (PHY)-level indications. Additionally and/or alternatively, the WTRU may report its aggregation configuration and/or support to another WTRU using sidelink (SL) transmissions, such as PC5-RRC, PC5- MAC, and/or SCI indications.

[0102] A WTRU may receive configuration parameters for aggregation mode operations. The configuration may include requirements, parameters, and/or settings related to aggregation, based on the capabilities and/or aggregation support of the WTRU. In one example, a WTRU may receive aggregation configuration from the network as part of an RRC (re)configuration. Additionally and/or alternatively, a WTRU may receive aggregation configuration from another WTRU, such as a GC, via SL transmissions (e.g., PC5-RRC).

[0103] In one example, a WTRU may receive one or more configurations. These configurations may include transmission modes. The WTRU may be configured to support or be enabled for one or more transmission modes. Different transmission modes may include a first transmission mode in which the WTRU may transmit an SRS using only its own antennas and antenna ports for the transmission (e.g., without aggregation). A second transmission mode may allow the WTRU to transmit the SRS using an aggregation of WTRUs, meaning multiple WTRUs may participate in transmitting the SRS. This mode may conserve a portion of the WTRU’s transmission energy and/or enable joint transmissions between WTRUs to improve channel quality. A third transmission mode may allow the WTRU to delegate the transmission of the SRS to other WTRUs, meaning the WTRU may not be part of the group of WTRUs performing the SRS transmission. This mode may conserve the delegating WTRU’s transmission power and energy while allowing the network to obtain knowledge of its SRS via the assistant WTRU’s transmissions.

[0104] In one example, the WTRU may be configured to support one or more of the transmission modes (e.g., based on its hardware, software, and/or implementation capabilities or by belonging to and/or being configured as a WTRU category supporting the feature). In another example, the WTRU may be configured to support one or more transmission modes for different transmissions or types of transmissions (e.g., using a first transmission mode for a first SRS set or SRS resource and using a second transmission mode for another SRS set or SRS resource).

[0105] The WTRU may be configured to use one or more aggregated transmission techniques. In one example, multiple WTRUs may simultaneously transmit the same signals on the same time and/or frequency resources so that the signals add up at a gNB. This transmission method may be referred to as SFN transmission. A benefit of SFN transmission may be that the received signal strength is boosted at the gNB, and the channel may benefit from diversity across different sources. In another example, multiple WTRUs may transmit different parts of a transmission, and the network may combine the received transmissions to reconstruct the complete transmission. For instance, WTRUs may be configured to transmit different layers of the transmission. The WTRUs may still act as a single logical entity and, from the network perspective, may be treated as different ports and/or layers of a single transmission.

[0106] The WTRU may be configured with indications regarding the aggregation group. The WTRU may receive a list of WTRUs within the aggregation group (e.g., including their WTRU IDs). Additionally and/or alternatively, the WTRU may receive an indication of the presence and/or ID of a GC, if applicable. The WTRU may receive an indication of the cells for which the aggregation group is active and/or supported. Additionally, the WTRU may receive information regarding other WTRUs within the group, including the number of antenna ports available for transmission and/or reception, transmit power and/or maximum transmit power, aggregation feature support (e.g., transmission modes, transmission schemes, and/or aggregation port mapping combinations), synchronization status and/or time alignment, battery level and/or energy settings, correlation and/or orthogonality with the WTRU, and/or relative or absolute position. The WTRU may also receive a priority list of WTRUs (e.g., indicating which WTRUs may be prioritized for participation in aggregated transmissions) and/or a list of non-preferred WTRUs that may be selected last for aggregated transmissions.

[0107] The WTRU may be configured to follow certain requirements regarding how aggregation may be performed and/or how WTRUs may be grouped. For example, the WTRU may receive configuration regarding grouping requirements such as correlation thresholds, maximum distance thresholds, and/or synchronization and/or time alignment thresholds.

[0108] In one example, the WTRU may be configured with SRS resources and/or sets. The WTRU may be individually configured with SRS resources and/or sets (e.g., receiving the configuration from the network as part of its RRC configuration). In one example, the WTRU may receive the configuration from the network (e.g., using SI, RRC, MAC, and/or PHY-level indications). In another example, the WTRU may receive configuration from another WTRU using SL communication (e.g., SL-RRC, SL-MAC, and/or SCI indications) or other inter-WTRU communication systems.

[0109] The SRS resource set configuration may include an SRS resource set ID, one or more SRS resources, and/or the resource type (e.g., whether the SRS resource set is periodic, semi-persistent, and/or aperiodic, along with corresponding configurations). The SRS resource set configuration may also include the usage (e.g., whether the SRS is used for beam management, codebook-based transmission, noncodebook transmission, and/or antenna switching). In one example, a new usage may be included that indicates the SRS is being used for aggregated transmissions. Additionally, the configuration may include power control parameters (e.g., target received power value (pO), power scaling (alpha), and/or reference pathloss). In one example, the power control parameters may include one set of values for non-aggregated transmissions and another set of values for aggregated transmissions. The configuration may also indicate whether an SRS resource set supports or allows transmission using aggregation (e.g., using a binary flag). [0110] The SRS resource configuration may include an SRS resource ID, the number of SRS ports, and/or spatial relation information used for the SRS. The WTRU may be pre-configured with an SRS resource, including spatial relation information (e.g., spatialRelationlnfo or spatialRelationlnfoPos), which may be received from a higher-layer configuration, pre-configuration, a MAC spatial reference update command, and/or an RS of a DCI activating an SRS resource and/or set. The RS may be an SSB, CSI-RS, and/or an SRS. Additionally, the configuration may include information regarding resources allocated for SRS transmission, including resource mapping, transmission comb, time and/or frequency indications, and/or other transmission-related parameters.

[0111] The WTRU may receive the SRS resources and/or sets configuration as part of a group of WTRUs (e.g., not for a specific individual WTRU). The WTRU may receive an SRS resources and/or sets configuration targeting a group (e.g., with a configuration indicating a group and/or aggregation ID). In that case, the SRS transmission may be left for the group of WTRUs to determine and configure how the WTRUs in the group manage to transmit the SRS.

[0112] Determination of transmission parameters for aggregated SRS may be discussed. The WTRU may determine the SRS set and/or resources, modes of transmission, and transmission parameters for itself. A source WTRU or an assisted WTRU may receive an SRS configuration for itself and determine whether and/or how to perform the aggregation of the SRS transmission for its SRS sets and/or resources. The WTRU may determine the SRS set and/or resources, modes of transmission, and transmission parameters for another WTRU. A WTRU operating as a group coordinator or an assistant WTRU may receive an SRS configuration for another WTRU (e.g., an assisted WTRU) and determine whether and/or how the assisted WTRU performs the aggregation of the SRS transmission. The WTRU may determine the SRS set and/or resources, modes of transmission, and transmission parameters for a group of WTRUs. A WTRU operating as a group coordinator may receive an SRS configuration applicable to a group of WTRUs and determine whether, which, and/or how the WTRUs in the group perform the aggregation of the SRS transmission.

[0113] A WTRU may determine to transmit SRS using an aggregated mode of transmission. The WTRU may determine one, more, or combinations of the following aspects: the SRS set(s) and/or resource(s) to use the aggregation mode of transmission on, the WTRU(s) that participate in the aggregated mode of transmission, the aggregated antenna port mapping (e.g., the mapping between the antenna ports of the WTRUs in the aggregation and the SRS ports), the transmit power to use for the different aggregated SRS ports, and the WTRU(s) associated with the different SRS resources within a resource set. [0114] The following describes the determination of the previously mentioned aspects separately, but it is to be understood that the criteria may be combined and some determination steps may be jointly determined. The WTRU may determine to use aggregated transmissions for some UL RS transmissions (e.g., based on received configuration and/or indication).

[0115] A WTRU may determine the transmission mode of some SRS resources or sets based on one or more conditions. The WTRU may determine to use a first mode of transmission (e.g., without aggregation) if a first condition is satisfied, a second mode of transmission (e.g., with aggregation) if a second condition is satisfied, and so on. The WTRU may determine to use different transmission modes for different SRS transmissions. A first mode of transmission may be used for some SRS sets and/or SRS resources, and a second mode of transmission may be used for some other SRS sets and/or SRS resources, both being simultaneously configured and/or active.

[0116] The WTRU may be configured and/or determine to measure one or more quality parameters (e.g., SINR, RSSI, RSRP, CQI) on one or more configured and/or determined signals and/or channels. The WTRU may receive the configuration (e.g., via SIB, RRC, MAC-CE, DCI), which may include one or more thresholds associated with the measurements. The WTRU may measure one or more quality parameters on received or detected DL signals and/or channels (e.g., SSB, PDCCH, PDSCH, or a DL RS such as DL DMRS and/or CSI-RS). The WTRU may determine to use the first mode of transmission if the measured quality parameter is higher than a first threshold, or may determine to use a second mode of transmission if the measured quality parameter is lower than a second threshold. The WTRU may determine the mode of transmission for a given SRS by measuring a DL channel associated with that SRS (e.g., when a WTRU receives the configuration of an SRS resource with a spatial relation indicating a DL RS, the WTRU may use the measurement on that DL RS to determine the SRS mode of transmission). The WTRU may also use the measurement of a signal and/or channel that is QCL’ed (e.g, transmitted by the network with similar spatial conditions) as the RS indicated in the spatial relation configuration.

[0117] The WTRU may determine to use one mode of transmission based on a configuration that the WTRU received and/or determined. The WTRU may determine or receive a configuration indicating that the WTRU is part of an aggregated group of WTRUs for the transmission of at least some control, data, or RS transmissions with the corresponding WTRU IDs in the group, data information (e.g, data flows, QoS flows, queues), and RS IDs. The WTRU may receive, as part of the aggregation group, the configuration indicating that the SRS of the group is to be transmitted using aggregation. The WTRU may determine to use the second mode of transmission (e.g, with aggregation) for an SRS set or resource when the SRS is indicated in the received configuration as part of the RS to transmit with aggregation (e.g., based on explicit indication in the SRS configuration). The WTRU may determine to use one mode of transmission (e.g., the third mode - delegated transmission) when the SRS configuration explicitly indicates the mode of transmission to use for the SRS (e.g., using a new field in the SRS resource or set configuration). The WTRU may use the aggregation mode when the SRS resource set usage is set to aggregation or delegation. The WTRU may determine to use the second mode of transmission (e.g., with aggregation) for an SRS set or resource when the SRS is used as a reference directly or indirectly (e.g., as a reference of a reference) for the transmission of data that is configured to be transmitted with aggregation (e.g., if the WTRU is configured and/or indicated a transmission via DCI or RRC where the SRS is in the TCI state, QCL states, or spatial transform). The WTRU may determine to use the second mode of transmission (e.g., with aggregation) for an SRS set or resource when the WTRU is configured with a QoS (e.g., based on latency, reliability, or data rate) associated with an aggregated transmission and that the WTRU has or expects data to be in the UL buffer, which is associated with the QoS requiring the aggregation.

[0118] The WTRU may determine to use one mode of transmission or another for an SRS resource or set based on the SRS port configurations (TX and RX). The WTRU may be configured with an SRS set indicating 4 SRS TX ports, while the WTRU alone supports (e.g., only supports) 2TX ports and supports 4TX when aggregated with another WTRU(s), then the WTRU may determine to use the aggregation mode of transmission for that SRS set. The WTRU may be configured with an SRS set indicating 2 SRS TX ports and supports 2 SRS TX ports alone or with another WTRU(s), and may determine to use the second mode of transmission (with aggregation).

[0119] The WTRU may be configured and/or determine to estimate its position in the network and/or with respect to the serving cell. The WTRU may use its position to determine the mode of transmission of the SRS. The WTRU may be configured and/or determine to use GNSS-based positioning, network-based positioning, and/or positioning based on another WTRU. The WTRU may be configured or determine to estimate its absolute position or relative position with respect to its serving cell. The WTRU may use synchronization signals and/or time alignment indications to estimate its distance to the serving cell. The WTRU may be configured with or determine thresholds with respect to distances and/or positions. The WTRU may determine to use the first mode of transmission if the WTRU is determined or indicated to be not in the cell-edge (e.g., if the distance to the serving cell is lower than a first threshold), or to use a second mode of transmission if determined or indicated to be in the cell-edge (e.g., if the distance to the serving cell is higher than a second threshold). [0120] The WTRU may have a low battery level or be configured in an energy-saving mode. The WTRU may determine to use aggregation for transmissions based on being configured in an energy-saving mode. [0121] The WTRU may determine to use one of the modes of transmission by default when there is no relevant configuration and/or no specific criterion being satisfied for the determination of mode of transmission. The WTRU may be configured (e.g., preconfigured) with a default mode of transmission. For example, the WTRU may be preconfigured to use a mode of transmission with aggregation (e.g., the second mode of transmission).

[0122] The WTRU may select the WTRUs in a group to perform a UL RS transmission (e.g., based on their capabilities).

[0123] The WTRU may determine a set and/or group of WTRUs to perform the aggregated transmission of some SRS sets and/or resources based on one or more conditions. The WTRU may select WTRUs to perform the aggregation transmission from a configured and/or determined list of WTRUs (e.g., the WTRUs in the aggregation group). The WTRU may select WTRUs to perform the aggregation transmission from WTRUs not configured to be part of the current aggregation group. The WTRU may select WTRUs to perform the aggregation transmission from both WTRUs configured and not configured to be part of the current aggregation group.

[0124] The WTRU may select a first set of WTRUs to perform the aggregation transmission if a first condition is satisfied, a second set of WTRUs to perform the aggregation transmission if a second condition is satisfied, and so on. The WTRU may determine to use different sets of WTRUs for different SRS transmissions. A first set of WTRUs may be used for some SRS sets and/or SRS resources, and a second set of WTRUs may be used for some other SRS sets and/or SRS resources, both being simultaneously configured and/or active.

[0125] The WTRU may select the WTRUs to perform the aggregated transmission of some SRS sets and/or SRS resources based on one or more or combinations of the following. The WTRU may determine to use one mode of transmission based on configuration that the WTRU received and/or determined. The WTRU may determine or receive a configuration indicating that the WTRU is part of an aggregated group of WTRUs for the transmission of at least some control, data, and/or RS transmissions with the corresponding WTRU IDs in the group, data information (e.g., data flows, QoS flows, queues), and RS IDs. The WTRU may select WTRUs within the WTRUs of the configured aggregation group. For an SRS set and/or resource, the WTRU may select WTRUs that are configured to perform the aggregated transmissions of the considered SRS set and/or resource, or the aggregated transmission of a data payload or control message using the SRS set and/or resource as a direct or indirect reference.

[0126] The WTRU may select WTRUs to perform the aggregated transmission based on the capabilities of the WTRUs. The WTRU may receive the WTRU capabilities of other WTRUs (e.g., based on information received by the WTRUs directly using PC5 connection, by another WTRU such as a group coordinator, or by the network). The WTRU may receive information about the supported features relative to aggregation for another WTRU, such as supporting aggregated transmission schemes, supported channels and/or signals for aggregation, the supported maximum number of WTRUs in an aggregated transmission, supported aggregated antenna port combinations, and/or the supported number of TX and RX ports. The WTRU may select WTRUs that support aggregated SRS transmissions. The WTRU may select WTRUs that support a configured aggregated transmission mode (e.g., supporting SFN transmission when SFN transmissions are configured or supporting non-SFN and/or independent port transmissions when non-SFN and/or independent port transmissions are configured). The WTRU may select WTRUs for which the total number of WTRUs in the aggregation is below or equal to the maximum supported WTRUs in an aggregated transmission. The WTRU may select a WTRU that supports the same number of TX and RX ports as itself (e.g., so that the two WTRUs' antenna port configurations could be identical). The WTRU may select a WTRU based on the number of TX and RX ports it supports, so that the total number of TX and/or RX ports is equal to or beyond a value. The value may be the number of ports indicated in the SRS configurations. The WTRU may select a WTRU that supports the aggregated antenna port combination that the WTRU is configured and/or determined to use for that SRS set and/or resource.

[0127] The WTRU may be configured and/or informed or may determine the correlation between the Uu channels of the WTRUs. The correlation information may indicate the level of correlation between the WTRUs (e.g., very correlated, loosely correlated, or not correlated). The WTRU may select the WTRUs for the aggregation based on the correlation values and the RS used to measure the correlation (e.g., the RS that is directly or indirectly used as a reference for the SRS set and/or resource). The WTRU may select another WTRU for which the Uu channels of the two WTRUs have a very high correlation for a given RS. The WTRU may select another WTRU for which the Uu channels of the two WTRUs have no correlation for a given RS. The WTRU may determine which correlation criterion to use for WTRU selection based on the aggregation transmission scheme of the transmission. A WTRU configured with an aggregated transmission using SFN transmissions may select WTRUs with high correlation (e.g., higher than a threshold). A WTRU configured with aggregated transmissions where the ports are independent (e.g., distributed MIMO) may select WTRUs with no and/or low correlation (e.g., lower than a threshold).

[0128] The WTRU may select WTRUs based on their position. The WTRU may select WTRUs within a given relative distance or proximity (e.g., based on a configured threshold of maximum distance between the WTRUs). This maximum distance may be beneficial to ensure good SL signal quality between the WTRUs or to ensure colocation of the WTRUs. The WTRU may select WTRUs that are close to the gNB (e.g., within a maximum distance threshold based on configuration).

[0129] The WTRU may select another WTRU based on synchronization aspects. The WTRU may select a WTRU if it is capable of adapting the timing of its transmission to match the timing of other WTRUs. The WTRU may select WTRUs that have the same configured time alignment parameters.

[0130] The WTRU may select other WTRUs based on WTRU priority. The WTRU may receive a WTRU priority list that sorts WTRUs in order for the aggregation transmissions. The WTRU may then select the WTRUs according to the order of priority, from the WTRUs satisfying other criteria, if any. The WTRU may have a list of non-preferred WTRUs that it avoids for the aggregated transmission.

[0131] It is understood that even if the presented criteria may be used as filters to down-select WTRUs that do not satisfy some criteria, the WTRU may also perform a selection and/or prioritization among the WTRUs that satisfy the requirements. The WTRU may select, from the set of satisfying WTRUs, the WTRUs whose priority in a received and/or determined WTRU priority list is higher. The WTRU may select, from the set of satisfying WTRUs, the WTRUs that have the strongest correlation of their signal (e.g., in the case where the WTRU delegates some ports of transmission, to maximize the similarity between the channels). The WTRU may select, from the set of satisfying WTRUs, the WTRUs that support the highest number of TX and/or RX ports to reduce the number of WTRUs in the aggregation to a minimum and avoid overhead between the WTRUs.

[0132] The WTRU may determine a set of transmission parameters for the aggregated SRS transmission. The WTRU may determine a set of transmission parameters for the aggregated transmission of a given SRS set and/or resource with a given set and/or group of WTRUs. The transmission parameters may include one or more of the following. The WTRU may determine a set of aggregated antenna port combinations based on the SRS configuration and WTRU capabilities.

[0133] The WTRU may determine the mapping between the antenna ports of the set and/or group of WTRUs and the SRS ports for the aggregated transmission of the SRS. In non-aggregated transmissions, the WTRU determines the antenna port to SRS port mapping itself (e.g., from internal implementation) and applies the same mapping for the SRS and the transmissions where that SRS is used as a reference. One antenna port may be mapped to a first SRS port that transmits on one of the SRS resources, and another antenna port may be mapped to a second SRS port that transmits on another SRS resource. Multiple antenna ports of a WTRU may be mapped to SRS ports using a given SRS resource. The WTRU may receive the configuration for the different SRS ports indicating the different SRS resources, cyclic shifts, frequency spacing (combing), frequency offsets, and so on, identifying and separating the different SRS ports. In aggregated SRS transmissions, the different WTRUs shall know how to map their antenna ports to the SRS ports (e.g., how the SRS ports are shared across the WTRUs).

[0134] The WTRU may receive SRS configuration indicating a given number of TX and/or RX ports (e.g., in the case of DL sounding using channel reciprocity). If the WTRUs do not know the mapping, there may be ambiguity about which SRS ports the WTRUs should transmit on, which may generate undesired overlapping transmissions.

[0135] The WTRU may determine that all WTRUs in the group apply an independent, overlapping mapping between their antenna ports and the SRS ports. In this option, all the WTRUs may simultaneously transmit on the SRS resources for each port. Each WTRU may use its own internal mapping (e.g., the same as the legacy non-aggregated mapping). This option may be beneficial for SFN transmissions, where the WTRU jointly transmits the SRS so that the gNB may perform channel estimation on the actual combination of UL signals and hence more accurately determine the aggregated channel.

[0136] The WTRU may determine that the antenna ports of different WTRUs map to separated SRS ports. For example, the two antenna ports of a first WTRU in the group may map to the first two SRS ports, and the two antenna ports of a second WTRU in the group may map to the third and fourth SRS ports. In this option, the WTRUs may transmit separately using the resources associated with different SRS ports. This option may be beneficial for the gNB to estimate individual channels and be able to schedule precoding or multi-layer transmissions.

[0137] The WTRU may determine to use all or parts of the antenna ports of one or more of the WTRUs in the group for the aggregated transmission. The WTRU may determine to use all the antenna ports of the WTRUs in the group (e.g., when the WTRUs have the same number of antenna ports and also the same as the SRS ports in SFN transmission). The WTRU may determine to use only one out of two or more of the antenna ports for each WTRU in the group (e.g., based on signal quality of the WTRU's signal or WTRU battery levels). [0138] The WTRU may determine the aggregated antenna port mapping across multiple WTRUs based on the SRS resource configuration. The WTRU may determine that the SRS transmission of ports configured to be simultaneous may be mapped to different WTRUs (e.g., to enable WTRUs to transmit each with full power). The WTRU may determine that the SRS transmission of ports configured in different time slots may be mapped to the same WTRU.

[0139] The WTRU may determine the aggregated antenna port mapping based on the SRS usage. The WTRU may determine that an SRS resource set configured with usage- 'antennaSwitching," "codebook," or "nonCodebook'' is configured to use different WTRUs and/or WTRU ports for each SRS port. The WTRU may determine that an SRS resource set configured with usage- 'beamManagement" may be associated with a mapping with overlapping ports across WTRUs.

[0140] The WTRU may determine the aggregated mapping of the WTRUs in the group (e.g., overlapping mapping, separated mapping, or a combination of both) based on one or more or combinations of the following. The WTRU may determine the mapping of the antenna ports of the group to the SRS ports based on the correlation of the Uu channels of the WTRUs. The WTRU may be configured and/or informed or may determine the correlation and/or orthogonality between the Uu channels of the WTRUs. The WTRU may determine to use the overlapping mapping across WTRUs when the WTRUs have a high correlation or low orthogonality. The WTRU may determine to use the separated mapping across WTRUs when the WTRUs have no and/or low correlation or high orthogonality.

[0141] The WTRU may determine the mapping of the antenna ports of the group to the SRS ports based on the aggregation transmission scheme of the transmission. A WTRU configured with an aggregated transmission using SFN transmissions may select to use overlapping mapping. A WTRU configured with aggregated transmissions where the ports are independent (e.g., distributed MIMO) may select to use separated mapping.

[0142] The WTRU may determine the antenna port mapping of the WTRUs based on the number of SRS ports configured for the SRS. A WTRU receiving an SRS configuration indicating 4 TX ports and the two WTRUs in the group having 2 TX antenna ports each may determine that the WTRUs use a separated mapping to have enough total TX ports in the aggregation. If the WTRU is configured with a 2 TX port SRS set and/or resource, and the WTRUs in the group all support 2 TX ports, the WTRU may select the overlapping mapping.

[0143] The WTRU may determine the antenna port mapping of the WTRUs based on received and/or determined configuration. The WTRU may receive a configuration indicating whether to use the overlapping or separated mapping for selected types of aggregated transmissions (e.g, at least for the aggregated SRS transmissions). The WTRU may receive and/or determine a configuration indicating the thresholds and conditions for which the different mappings apply (e.g., the threshold on correlation and/or orthogonality that the WTRU needs to use for the orthogonality criterion).

[0144] The WTRU may determine the antenna port mapping based on the signal quality of the WTRUs. Two WTRUs having similar RSRP or signal quality may be mapped to the same ports to have a similar contribution or conditions and be favorable for overlapping mapping.

[0145] The WTRU may determine the antenna port mapping based on the synchronization or time alignment of the WTRUs. The WTRU may map WTRUs with the same time alignment parameter to the same SRS ports, while WTRUs with different time alignment parameters may be mapped to different ports. [0146] It is understood that even if the presented criteria may be used as filters to down-select ports, the WTRU may also perform a selection and/or prioritization among the WTRUs or WTRUs’ ports that satisfy the requirements. The WTRU may prioritize a WTRU or a WTRU’s port whose RSRP is higher to the SRS port to maximize the signal quality of the aggregated transmission. The WTRU may prioritize a WTRU or a WTRU’s port based on its correlation with itself (e.g., prioritizing the WTRU’s port for which the WTRUs have the strongest correlation in the case of SFN transmission). The WTRU may prioritize WTRUs with the lowest correlation in the case of non-SFN transmission to increase diversity.

[0147] The WTRU may determine the format of the aggregated port mapping based on the selected WTRUs, their capabilities, and the transmission mode. The WTRU may determine the format of the mapping of the antenna ports of the WTRUs in the group. The WTRU may determine the individual antenna port to SRS port mapping of the WTRUs in the group based on the number of ports supported by the WTRUs in the group, the number of SRS ports, and the determined port mapping.

[0148] Each WTRU may map to a vector of antenna port indices with a length of SRS ports to indicate which port of a WTRU is used for which SRS port. For instance, WTRU1 : [1 ,2, -1 ,-1] means that WTRUI’s first antenna port maps to the first SRS port, WTRUTs second antenna maps to the second SRS port, and WTRU1 does not have an antenna port mapping to the third and fourth SRS ports, as the "-1" value is used to denote the absence of mapping, although other ways to indicate this absence are not precluded.

[0149] Each WTRU may map to a set of SRS port indices. For instance, WTRU2: {3,4} means that WTRU2’s antenna ports are mapped to SRS ports 3 and 4. If no further information is determined or stored in the mapping signaling, WTRU2 may determine itself how to map its antenna ports to the received SRS ports. [0150] The WTRU may determine the SRS ports that the WTRUs map their antennas port to and/or a number of antenna ports to use for that mapping, based on, for example, the number of SRS ports and/or the determined port mapping. As an example of mapping format, each WTRU may map to a set of SRS port indices and a number of antenna ports to use. For instance, WTRU2: {3,4} with 2 antenna ports means that two of WTRU2’s antenna ports are mapped to SRS ports 3 and 4. If no further information is determined or stored in the mapping signaling, WTRU2 may determine itself how to map two of its antenna ports to the received SRS ports.

[0151] The WTRU may determine a number of ports that the WTRUs should map to the SRS ports. The WTRU may indicate to another WTRU that it is allocated with 2 ports for a given SRS resource and/or set. The other WTRU may then autonomously map its ports to the SRS ports based on the SRS resource and/or set configuration. If the SRS resource and/or set is configured with 2 TX ports and the other WTRU receives the configuration to map 2 ports to that SRS resource and/or set, the WTRU should map 2 of its TX ports to the 2 SRS ports.

[0152] The WTRU may determine a mapping indicating which WTRUs map to which SRS resources. In that case, the WTRUs are indicated with the SRS resource ID and may perform their own internal mapping between their antenna ports and all of the SRS ports based on the configuration of the SRS group and/or resource. Each WTRU then covers all the ports, and the WTRUs transmit the SRS with overlapping and/or simultaneous transmissions.

[0153] The WTRU may determine that itself and another WTRU both map their 2 TX ports to the 2 SRS ports of an SRS resource and/or set based on the transmission mode associated with the SRS being an SFN transmission (e.g., as configured and/or determined from the scheduling indication received by the WTRU for a transmission using this SRS as a reference). The WTRU may then send a configuration to the other WTRU indicating the corresponding SRS resource and/or set and that it shall map 2 of its TX ports to the SRS ports. The WTRU may determine that itself and another WTRU both map their 2 TX ports to different SRS ports of an SRS resource and/or set that includes 4 TX ports based on the transmission mode associated with the SRS being a non-SFN transmission (e.g., as configured and/or determined from the scheduling indication received by the WTRU for a transmission using this SRS as a reference). The WTRU determines which SRS ports each WTRU should be mapped to so that no ambiguity or overlap appears. The WTRU may, for example, select ports {0,1} for itself and {2,3} for the other WTRU. The WTRU may then indicate to the other WTRU the SRS resource and/or set and the corresponding port mapping (e.g., 2 ports to be mapped to SRS ports {2,3}). [0154] The WTRU may determine the aggregated SRS transmit power configuration based on the determined port mapping, the aggregated transmission scheme, and WTRU capabilities and/or WTRU power control. The WTRU may determine parameters applicable to the transmission power or transmit power control of the WTRUs in the aggregation group related to the aggregated SRS based on, for example, the transmission power parameters of the assisted WTRU(s) and the aggregated port mapping. To perform the joint or distributed transmission of the configured SRS, WTRUs need to be aligned on the power contribution they each bring to the signal transmission. In NR legacy operations, the SRS transmit power is equally split over the ports of a single WTRU.

[0155] The WTRU may determine the actual transmission power to be used for the aggregated SRS transmission (e.g., based on its own transmit power control behavior and other WTRU power capabilities such as maximum transmit power). The WTRU may determine the total transmit power (e.g., the sum of the transmit power from all WTRUs for the transmission of the aggregated SRS) based on its own SRS transmit power control behavior (e.g., using the legacy SRS power control behavior). The WTRU may determine the total transmit power based on a transmit power control behavior dedicated to aggregated SRS transmissions (e.g., where some parameters are given for the group instead of being WTRU-specific, such as using an average pathloss value or a dedicated and/or configured power scaling factor for aggregation). The WTRU may determine the transmit power for each aggregated SRS port. The WTRU may determine the total transmit power of the aggregated SRS transmission and share evenly the linear value of the total SRS transmit power across the aggregated SRS ports by dividing it by the number of ports. The WTRU may determine the transmit power for each port based on the maximum transmit power of each WTRU and/or the pathloss of the WTRUs. The WTRU may determine the transmit power of each port to compensate for the pathloss between the WTRU and the gNB so that each port brings an equal contribution at the network side, with the individual port contribution determined based on the total power of the WTRU and the pathloss of the WTRUs.

[0156] The WTRU may determine the transmit power of the aggregated SRS transmission for each WTRU in the group, and each WTRU may further distribute the power across its ports for the SRS transmission. The WTRU may determine the total transmit power of the aggregated SRS transmission and divide it by the number of WTRUs. The WTRU may determine the transmit power per WTRU individually (e.g., based on each WTRU’s maximum transmit power and/or power contribution corrected by its pathloss). The WTRU may determine the transmit power of each port to compensate for the pathloss between the WTRU and the gNB so that each WTRU brings an equal contribution at the network side, with the individual WTRLI contribution determined based on the total power of the WTRU and the pathloss of the WTRUs.

[0157] The WTRU may determine one or more of the SRS transmit power control loop parameters (e.g., maximum output power, target power (pO), power scaling factor (alpha), pathloss) to be used by the WTRUs for the transmission of the aggregated SRS based on its own power loop. The WTRU may determine these parameters to effectively configure the other WTRUs to follow a similar power control algorithm so that the different WTRUs apply the same behavior in the SRS transmit power. The WTRU may determine a common maximum transmit power for the SRS transmission applied for each WTRU and/or port, and the WTRU may determine this value based on its own maximum transmit power (e.g., the same or divided by the number of WTRUs). Other transmission parameter values can be determined and shared, such as the power scaling factor (alpha) or the pathloss value to use as a reference, using the assisted WTRU’s value as a reference.

[0158] The WTRU may determine an offset that the WTRUs in the group apply to their regular transmission power calculation to compensate for being part of an aggregated transmission. The WTRU may determine, for an aggregated transmission with 2 WTRUs and 2 transmit ports each, to apply a -3dB offset to the SRS transmission power. For the WTRUs in the group, having a power control parameter for an aggregated SRS transmission is equivalent to having a new dedicated power control for that SRS. The WTRUs may have a regular power control behavior and/or set of parameters for non-aggregated transmissions and another behavior and/or set of parameters for aggregated transmissions. The WTRUs may have multiple SRS power control behaviors and/or sets of parameters for different aggregations of SRS (e.g., if the parameters are determined based on one WTRU’s value or based on the parameters of the group of WTRUs).

[0159] The WTRU may determine which transmit power rule or parameter to determine (e.g., the transmit power per WTRU or per port or using power control parameters) based on the aggregated transmission scheme used for the transmission, the determined aggregated port mapping, the capabilities of the WTRU(s), their power profiles, and the Uu channel quality of the WTRU(s). The WTRU may determine to share the power equally across ports for the different WTRUs when the transmission scheme associated with the aggregated SRS is SFN since it may be beneficial to have a similar contribution of received power at the network side for the coherent reception of the aggregated signal. The WTRU may determine to use a different target power for the WTRUs in the aggregation group based on the Uu channel quality of the WTRUs and their power profiles. The WTRU may determine a higher target power for WTRUs with a strong power profile and a lower target power for WTRUs limited by battery capacity. The WTRU may also determine the target power based on the pathloss of the WTRUs to the network to avoid requiring a strong transmit power from WTRUs with lower channel quality.

[0160] The WTRU may determine a per-port transmit power or power control parameter based on the determined aggregated port mapping. The WTRU may determine that when two antenna ports (e.g., across WTRUs) are mapped to a single SRS port while another SRS port is mapped to a single antenna port, the antenna ports mapped to a common SRS port may have a different transmit power (e.g., -3dB) than the one with a single antenna port.

[0161] The WTRU may determine the association between SRS resources of an SRS resource set and the WTRUs in the aggregation group (e.g., based on the determined port mapping or the SRS usage). The WTRU may determine how the different SRS resources of an SRS resource set are distributed among WTRUs in the group (e.g., based on the SRS configuration, such as usage). The WTRU may share the SRS resources of an SRS resource set evenly among the WTRUs in the sub-group of aggregated WTRUs. The WTRU may also share the SRS resources of an SRS resource set evenly among the determined SRS ports. When different SRS resources correspond to different SRS ports (e.g., when the usage is set to antennaSwitching), the WTRU may use the determined aggregated SRS port mapping to associate and/or allocate the SRS resources to the WTRUs.

[0162] In the case where the SRS is configured for usage=beamManagement, and the different SRS resources of the SRS resource set correspond to different spatial filters from the WTRU, the different WTRUs in an aggregation scenario may have their own spatial filters and sweep them separately using the SRS resource set. The WTRU may determine which resources from the resource set to allocate and/or associate with each WTRU (e.g., based on the number of spatial filters supported by each WTRU in the aggregation group). The WTRU may separately allocate and/or associate a part of the SRS resources from an SRS resource set corresponding to the supported number of spatial filters for each WTRU. The WTRUs may allocate and/or associate overlapping SRS resources from an SRS resource set to different WTRUs in the group, generating a combined spatial filter on the overlapping resources.

[0163] The WTRU may determine the format of the SRS resource allocation and/or association with the other WTRUs based on the determined resource sharing. The WTRU may indicate to another WTRU the set of SRS resource IDs corresponding to its allocated part (e.g., using SL RRC, SL MAC, or SCI indications). The WTRU may determine the previous aspects sequentially, or some aspects may be determined jointly as part of a single determination step. [0164] The WTRU may first determine that a given SRS set and/or resource shall use an aggregated mode of transmission and then jointly determine which WTRU and the corresponding antenna ports (e.g., since the number of ports and supported combinations may be part of the WTRU selection process). The WTRU may first determine that a given SRS set and/or resource shall use an aggregated mode of transmission and then jointly determine the transmission power parameters and which WTRUs are in the aggregation transmission based on the power configuration of the WTRUs (e.g., based on each WTRU’s available or maximum power) to avoid selecting WTRUs that do not have enough transmit power to match the transmission. The WTRU may first determine that it shall perform transmissions with aggregation with some other WTRUs (e.g., based on received configuration or indications) and then determine which SRS resources and/or sets are suitable for that group of WTRUs (e.g., based on the number of supported ports among the group).

[0165] The WTRU may request UL RS configuration based on the aggregation configuration. The WTRU may first determine a total number of antenna ports to be used for the aggregation (e.g., based on the WTRU capabilities and number of antennas in the group) and then send an indication to the network including this aggregation configuration. The WTRU may send this configuration as an RRC configuration or a WTRU capability indication to the network. This indication intends to trigger and/or request the network to configure and/or reconfigure the WTRU with an SRS configuration that includes the total supported number of ports.

[0166] A WTRU may first indicate to the network its own capability of 2 antenna ports, then determine that with aggregation, it may support up to 4 antenna ports jointly with other WTRUs, and send the indication to the network as an updated or additional WTRU capability. The WTRU may then receive a new set of SRS configurations where the number of ports is higher than what it supports without aggregation (e.g., 4 ports). The WTRU may determine that an SRS resource and/or set is configured implicitly for aggregation when the number of configured ports is higher than its own capability.

[0167] The WTRU may transmit the determined set of parameters to the WTRUs and the network. The WTRU may send the determined set of transmission parameters for the SRS transmission to another WTRU. The WTRU may send the aggregated SRS transmission parameters using Sidelink RRC configuration or reconfiguration (e.g., for semi-static aggregation configuration). The WTRU may also send the aggregated SRS transmission parameters using Sidelink MAC (e.g., MAC CE) configuration or SL PHY level configuration (e.g., in SCI). [0168] The WTRU may send the aggregated SRS transmission parameters to the GC. The WTRU may be configured (e.g. , as part of the aggregation) to report aggregation-related configuration and decisions to the group coordinator of an aggregation group. The GC may have been indicated via the group configuration. In this case, the WTRU report may include the transmission parameters for all the WTRUs concerned with the aggregation of the SRS transmission (e.g., the selected WTRUs) and identified individually (e.g., via their WTRU ID). The WTRU may send the aggregated SRS transmission parameters to the WTRUs participating in the aggregated SRS transmission. The WTRU may be configured (e.g., as part of the aggregation) to report the determined configuration to the selected WTRUs in the aggregation group. The WTRU may report to the selected WTRU(s) using dedicated unicast transmissions to each WTRU individually, where the report may include only the transmission parameters required by that WTRU. The WTRU may transmit the transmission parameters to all the WTRUs using groupcast and/or broadcast transmission, where the individual configurations are indicated with the corresponding WTRU IDs.

[0169] If the source and/or assisted WTRU is not the WTRU performing the decision and is not part of the selected group of WTRU(s) (e.g., when the SRS transmission is fully delegated), the WTRU determining the transmission parameters may still report to the source and/or assisted WTRU indicating that the WTRU is not part of the transmission group. The WTRU may indicate the SRS resources and/or sets configuration that are part of the aggregation. The configuration may include the SRS resource and/or set ID when the SRS resources and/or sets are commonly configured to the WTRUs in the group. The configuration may include parts or all of the SRS resource and/or set configuration (e.g., periodicity, time and frequency resources of the SRS, offsets, scrambling, IDs) received by the WTRU. The configuration may indicate the gNB (e.g., cell ID) corresponding to the received SRS configuration. The WTRU may indicate the determined list of WTRUs participating in the aggregation group for the aggregated SRS transmission. The WTRU may indicate the determined aggregated port mapping (e.g, using the formats described previously). The WTRU may indicate the determined transmit power parameters to be used by the other WTRUs for the transmission. The parameters may include total transmit power, per-WTRU transmit power, per-port transmit power, power control behavior parameters (e.g, pathloss, offsets, scaling factor).

[0170] The WTRU may indicate to another WTRU a change in an aggregation configuration using the above-mentioned parameters. The WTRU may have determined a first aggregation set of parameters, sent the first set of parameters to the WTRUs in the aggregation, then determined a second set of parameters (an update in the configuration) based on newly received configuration or indications, and sent the second set of parameters to the WTRUs in the aggregation. The WTRU may determine that one or more of the WTRUs in the aggregation group configured for the aggregated transmission of the SRS is no longer part of the aggregation of that SRS in a second determination of the set of parameters. The WTRU may then send an indication to these WTRUs indicating that they are no longer part of the aggregation for the corresponding SRS IDs.

[0171] A WTRU may receive a first set of parameters for the aggregation transmission of SRS and further receive a second set of parameters for the aggregation transmission of the same SRS (e.g., based on SRS ID). The WTRU may then update the set of parameters based on the latest received parameters.

[0172] In some examples, WTRUs may share their SRS resources and/or sets configuration. A WTRU may send the SRS resources and/or sets configuration it received from the network, where the SRS resources and/or sets are configured specifically for that WTRU (e.g., WTRU-specific RRC configuration, similar to legacy). The WTRU may send the SRS resources and/or sets configuration limited to the SRS resources and/or sets that are configured and/or determined to be part of aggregation schemes to the WTRUs of the aggregation.

[0173] The WTRU may send the SRS resources and/or sets configuration it received from the network, where the SRS resources and/or sets are configured for a group of WTRUs. The WTRU may receive these SRS configurations as part of the group, and they may be configured for the group (e.g., using a configuration indicating its applicability to the group). In that case, the WTRU may indicate the corresponding SRS ID from within the group configuration when indicating the SRS resource and/or set to apply the aggregation configuration to.

[0174] The WTRUs may each receive SRS resources and/or sets configuration from the network separately (e.g., using WTRU-specific RRC configuration), but the network may configure the WTRUs with common SRS resources and/or sets. A WTRU may first send its SRS resource and/or set configuration to another WTRU, and the other WTRU receiving the configuration may establish a mapping and/or correspondence between the received SRS configuration from the network and from the WTRU (e.g., mapping the SRS IDs). That way, the WTRUs may then share (e.g., only share) SRS IDs when indicating SRS configurations, and the WTRU receiving the SRS IDs may use the established mapping to retrieve from its own configuration the correct SRS configuration.

[0175] The WTRU may send the determined set of transmission parameters for the SRS transmission to the network. The WTRU may send the aggregated SRS transmission parameters using RRC configuration or reconfiguration (e.g., for semi-static aggregation configuration). The WTRU may also send the aggregated SRS transmission parameters using MAC (e.g., UL MAC CE) configuration or SL PHY level configuration (e.g., in UCI).

[0176] In examples, (e.g., for each determined aggregated SRS resource and/or set transmission), the WTRU may indicate the SRS resources and/or sets configuration that are part of the aggregation. The configuration may be referenced using the SRS resource and/or set ID. The WTRU may indicate the determined list of WTRUs participating in the aggregation group for the aggregated SRS transmission for WTRU selection. The WTRU may indicate the determined aggregated port mapping (e.g., using the formats described above) for antenna-port to SRS port mapping. The WTRU may indicate the determined transmit power parameters to be used by the other WTRUs for the transmission. The parameters, as described above, may include total transmit power, per-WTRU transmit power, per-port transmit power, and power control behavior parameters (e.g., offsets and/or scaling factor.).

[0177] The WTRU may indicate other WTRUs to perform the SRS transmission based on received activation and/or triggers. In one aspect of the solution, a WTRU may receive an indication to perform the transmission of an SRS resource and/or set that is determined and/or configured to be performed using aggregation. When receiving such an indication, the WTRU may send (e.g., forward) a similar indication to the WTRUs in the aggregation group. For example, the WTRU receives the configuration for a periodic SRS transmission (e.g., via RRC) and sends the periodic transmission parameters (e.g., resources, and/or periodicity) to the WTRUs in the aggregation group (e.g., via SL RRC). As another example, the WTRU received the configuration for a semi-persistent SRS transmission (e.g., via RRC) and receives an indication to activate the transmission (e.g., via MAC indication). The WTRU may send the activation indication (e.g., using SL MAC indication). As another example, the WTRU received an aperiodic SRS transmission configuration (e.g., via RRC) and receives a transmission command to perform the SRS transmission (e.g., via MAC and/or DCI indication). The WTRU may send the transmission command (e.g., using SL MAC and/or SCI indication).

[0178] In one aspect of the solution, a WTRU indicated to transmit an SRS using an aggregated mode of transmission may use the determined and/or received aggregation transmission parameters for the transmission of the indicated SRS. A WTRU may use a combination of the received (e.g., received from the network or shared by another WTRU) configuration for the SRS resource and/or set configuration (e.g., for resource and/or scheduling indications) and the determined and/or received set of aggregation parameters (e.g., for antenna and/or power configuration). In some examples, the WTRU may transmit (e.g., only transmit) on a part of the configured SRS ports or resources when the other ports are mapped to another WTRU, based on the determined and/or received port mapping. The WTRU may use the determined and/or received transmit power configuration instead of the regular SRS power control behavior to determine the transmit power to apply for the SRS transmission. A WTRU participating in an aggregated SRS transmission (e.g., an assistant WTRU) may send the SRS transmission including an indication of its WTRU ID and/or antenna port ID as part of the SRS (e.g., as an implicit indication such as scrambling the transmission or applying an offset or a cyclic shift corresponding to its WTRU and/or port ID). Adding this indication in the SRS transmission may avoid the need for the WTRUs to report the aggregation configuration to the network, with the network detecting the mapping and WTRU selection when receiving the SRS directly.

[0179] The WTRU may be configured with multiple sets of parameters (e.g., power control parameters and/or port mapping) for the transmission of SRS resources and/or sets (e.g., for when it transmits with or without aggregation). The WTRU (e.g., assistant WTRU) may receive some sets of parameters from another WTRU (e.g., the assisted WTRU or GC). In another option, the WTRU may have determined some sets of parameters itself (e.g., the GC or the assisted and/or source WTRU). The WTRU may be configured, store, and/or have determined multiple transmission parameter sets for different aggregation configurations (e.g., a WTRU may assist multiple WTRUs in SRS transmissions, or different SRS resources and/or sets may apply different transmission parameters). The WTRU may determine to use one of the sets of parameters based on the received indication for the SRS transmission (e.g., via DCI, MAC, and/or RRC) and based on whether the SRS is configured, determined, and/or indicated to be transmitted with or without aggregation. The WTRU may determine to use one of the sets of parameters based on the upcoming transmissions. For example, the WTRU may receive a transmission grant wherein the transmission is configured to use an SRS as a reference, and the transmission is configured to use aggregation. The WTRU may then determine to use the SRS transmission configuration corresponding to the aggregated transmission configuration.

[0180] The WTRU may use the determined set of parameters for SRS transmission for aggregated transmissions based on an SRS indication in the received grants. In one aspect of the solution, the WTRU configured and/or having determined a set of parameters (e.g., aggregated port mapping) for the transmission of aggregated SRS transmission may receive a transmission indication (e.g., a grant) configured with an SRS as a reference for the spatial filter or for codebook, for which the WTRU is configured and/or transmitted previously with aggregated SRS transmission. The WTRU may reuse parts or all of the set of parameters to transmit other signals or channels, such as PUSCH, DMRS, or any transmissions that use the aggregated SRS as a reference for its transmission.

[0181] The WTRU may reuse the same transmission configuration for the granted transmission (s) as the aggregated SRS transmission configuration (e.g., for the transmission of the data payload PUSCH and the associated RS such as PUSCH DMRS). The WTRU may send and/or forward the grant or send a transmission indication including the necessary information from the grant, such as scheduling information, to the WTRUs in the aggregation. The indication may further include the data and/or signal to be transmitted by the WTRUs. The indication may include the SRS IDs to be used as a reference and be the reference for the set of parameters and/or mode of transmission to be used by the other WTRUs for that transmission.

[0182] The WTRU may transmit the granted transmission using a different set of parameters (e.g., without aggregation), while the SRS was configured and/or transmitted with aggregation. The WTRU may determine to use the different set of parameters based on a received indication in the grant (e.g., indicating that the transmission should not be performed with aggregation) or if the time between the received and/or decoded grant and the actual transmission is not enough to forward and/or send the necessary information to the other WTRUs.

[0183] The WTRU may determine the mode of transmission and/or set of parameters to use for a given transmission based on the SRS indication in the grant. The SRS indication may include an explicit or implicit indication to use the aggregation. The WTRU may receive an indication jointly with the SRS indication (e.g., a bit-flag) for aggregation or non-aggregation. The WTRU may be configured with a dual SRS ID corresponding to the same SRS resources and/or sets but with or without aggregation, and when the WTRU receives the SRS ID, the WTRU determines the mode of transmission and/or set of parameters based on the received SRS ID. The WTRU may determine to use the aggregated SRS parameters for a given transmission when it receives a DCI granting the transmission scrambled with a specific RNTI indicating the use of aggregation (e.g., an aggregation group-RNTI, which can be specific for each aggregation group or aggregation configuration). The WTRU may then use the set of parameters used for aggregation for the SRS indicated in the grant.

[0184] A WTRU may be (pre)configured as part of an aggregation group with a first set of transmission parameters for an SRS set (e.g., using non-aggregated transmission) and a second set of transmission parameters for the same SRS set (e.g., using aggregated transmission configuration, including inter-WTRU port mapping, other WTRU ID). [0185] The WTRU may receive a transmission command from the network indicating an SRI for the transmission and the scheduling resources (e.g., via a DCI carrying a scheduling grant). The WTRU may determine that the SRI is for an aggregated transmission with the other WTRU based on the RNTI used for the DCI being an aggregation group-RNTI or RNTI of another WTRU, the DCI being transmitted in resources reserved for aggregation scheduling, and/or an explicit indication in the DCI.

[0186] The WTRU may send the scheduling command, the corresponding SRI, and transmission parameters to the other WTRUs. The WTRU may transmit (e.g., PUSCH, PUSCH DMRS) on the indicated resources using the transmission parameters associated with the aggregation transmission mode for the received SRI.

[0187] WTRU actions and/or steps may receive the following (pre)configuration as part of an aggregation group: one or more SRS resources and/or sets configuration, including the resource configuration and their configured number of ports; transmission configured with an aggregation scheme (e.g., non-SFN transmission) and associated with an SRS (e.g., an UL grant with SRS indication); and indications (e.g., received from a GC) about the other member WTRUs, such as supported number of antenna ports and aggregation schemes, and/or indication on collocation between the WTRUs (e.g., positions and/or synchronization timing).

[0188] WTRU actions and/or steps may determine a set of transmission parameters to perform aggregated SRS transmissions based on the received configuration and indications. The determination may include the SRS resource and/or set IDs to be transmitted with aggregation (e.g., based on the configured aggregated transmissions and the associated SRS indication).

[0189] The WTRU may determine a subset of WTRUs to perform the aggregated SRS transmission. The WTRU may select a set of WTRUs based on the WTRU configurations in the group. For example, for an SRS configured with 4TX ports and associated with a non-SFN transmission, the WTRU may select two WTRUs with 2TX ports each that are not collocated and supporting non-SFN aggregated transmission. [0190] The WTRU may determine the mapping between antenna ports of the subset of WTRUs to the configured SRS ports. The WTRU may map the two antenna ports of the first WTRU to the first two SRS ports and the two antennas of the second WTRU to the third and fourth SRS ports.

[0191] The WTRU may determine aggregated SRS transmission power parameters based on the WTRUs’ SRS transmit power. The WTRU may determine the transmit power of another WTRU’s port based on its transmit power control and by dividing the power equally among WTRUs. [0192] WTRU actions and/or steps may send the aggregated SRS resource and/or set of transmission parameters (e.g., port mapping, transmission power) to the determined subset of WTRUs and to the network.

[0193] In the case where the WTRU receives an indication to transmit an aggregated SRS, the WTRU may send an SRS transmission indication to the WTRUs determined for the aggregated transmission. The WTRU may receive the indication via MAC activation and/or DCI command for semi-persistent and/or aperiodic SRS and/or send the indication via SL-MAC and/or SCI, respectively.

[0194] WTRU actions and/or steps may transmit the SRSs using the determined set of aggregated transmission parameters and the received configuration.

[0195] Fig. 2 illustrates an example scenario 200 where WTRU A 206a may receive an RS configuration 208 from the network 202 as part of an aggregation group 204. WTRU A 206a may then transmit the RS configuration and/or aggregated transmission parameters 210 to other WTRUs in the group (e.g., WTRU B 206b and/or WTRU C 206c). WTRU B 206b and/or WTRU C 206c may further transmit the RS when the RS is triggered and/or configured to be transmitted on behalf of WTRU A 206a and/or the aggregation group 204. The RS transmission 212 may then be sent to the network 202.

[0196] FIG. 3 illustrates an example method 300 for aggregated sounding reference signal (SRS) transmission, including a method for determining whether the SRS transmission is to be transmitted using determined aggregated SRS transmission parameters or regular parameters.

[0197] A WTRU may determine the set of transmission parameters to use based on an SRS indication. The WTRU may receive a (pre)configuration including a first set of transmission parameters for an SRS resource and/or set using non-aggregated transmission, including SRS resources, spatial filter, and port configuration. The WTRU may also receive a second set of transmission parameters for an SRS resource and/or set configuration using aggregated transmissions, including the SRS resources, the associated SRS set ID and/or SRS IDs, the corresponding spatial filters, a mapping between the WTRU ports and the aggregated SRS ports, power control parameters, and the corresponding WTRU ID.

[0198] The WTRU may receive a transmission command from the network (e.g., a DCI carrying a scheduling grant) and/or from another WTRU (e.g., a grant forwarded over SCI), indicating an SRI for the transmission and the scheduling resources. The WTRU may determine the set of transmission configurations to use for the transmission based on one or more conditions. The determination may include that the SRS ID in the SRI is for an aggregated transmission with another WTRU, the RNTI used for the DCI is an aggregation group-RNTI and/or RNTI of another WTRU, and/or there is an explicit indication in the DCI and/or SCI.

[0199] The WTRU may transmit on the granted resource (e.g., PUSCH and/or PUSCH DMRS) using the determined set of transmission parameters associated with the aggregation transmission mode for the indicated SRS.

[0200] At 302, a WTRU may be configured with aggregation. At 304, the WTRU may receive SRS configuration and WTRU indications, which may include details on available SRS resources, port mappings, and other aggregation-related parameters.

[0201] At 306, the WTRU may determine transmission parameters for aggregated SRS transmission based on the received SRS configuration and WTRU indications. The parameters may define how SRS resources are allocated among WTRUs in the aggregation group.

[0202] At 308, the WTRU may send the determined transmission parameters to aggregated WTRUs in the group. At 310, the WTRU may receive an SRS transmission indication or command.

[0203] At 312, the WTRU may determine whether the SRS is configured for aggregated transmission. If the SRS is determined to not be configured for aggregation at 312, the WTRU may transmit the SRS using the received SRS configuration at 314.

[0204] If the SRS is determined to be configured for aggregation at 312, the WTRU may send an SRS transmission indication or command to aggregate WTRUs at 316. At 318, the WTRU may transmit the SRS using the SRS configuration and the determined aggregated transmission parameters.

Claims

CLAIMS:

1 . A wireless transmit/receive unit (WTRU) comprising: a processor and memory, wherein the processor and memory are configured to: receive a reference signal (RS) transmission configuration; determine a set of aggregated transmission parameters to perform aggregated RS transmissions, wherein the determination is based on the RS transmission configuration; send the set of aggregated RS transmissions parameters to one or more of a network or other WTRUs in an aggregation group; receive an indication to transmit an aggregated RS transmission; send the indication to transmit the aggregated RS transmission to the other WTRUs in the aggregation group; and transmit the aggregated RS transmission using the determined set of transmission parameters and the RS transmission configuration.

2. The WTRU of claim 1 , wherein the set of aggregated RS transmission parameters comprise one or more of a subset of aggregated WTRUs, transmission resources, an antenna port mapping, or a transmission power for each WTRU in the aggregation group.

3. The WTRU of claim 2, wherein the processor is configured to distribute the transmission power across one or more WTRUs in the aggregation group based on one or more of received pathloss information, maximum transmit power of each WTRU in the aggregation group, or a power scaling factor associated with the aggregated RS transmission.

4. The WTRU of claim 2, wherein the set of aggregated RS transmission parameters comprise the antenna port mapping.

5. The WTRU of claim 4 wherein the processor is configured to determine the antenna port mapping of antenna ports of different WTRUs in the aggregation group to respective RS ports based on a received configuration indicating a RS port allocation scheme for the aggregated RS transmission.

6. The WTRU of claim 1 , wherein the processor is configured to: receive a set of non-aggregated transmission parameters to perform non-aggregated RS transmissions; receive an additional indication that indicates whether to transmit the aggregated RS transmission or the non-aggregated RS transmissions; and determine whether to use the set of aggregated transmission parameters or the set of nonaggregated transmission parameters to perform a transmission based on the additional indication.

7. The WTRU of claim 1 , wherein the indication to transmit the aggregated RS transmission comprises one or more of an RS resource identifier(ID), a radio network temporary identifier (RNTI), or an indication source.

8. The WTRU of claim 7, wherein the indication to transmit the aggregated RS transmission comprises an RS resource ID, wherein the RS resource ID corresponds to an RS resource set configured for an aggregation group transmission mode, and wherein the RS is a sounding reference signal (SRS).

9.. The WTRU of claim 1 , wherein the processor is configured to: select a RS resource set based on a received aggregation configuration, wherein the aggregation configuration indicates a RS usage mode associated with the aggregation group, to determine the set of transmission parameters.

10. The WTRU of claim 1 , wherein the processor is configured to determine the set of transmission parameters by selecting a subset of WTRUs for aggregated RS transmission based on one or more of an indication of collocation, an indication of synchronization timing, or an indication of supported antenna ports received from a group coordinator.

11. A method implemented by a wireless transmit/receive unit (WTRU), the method comprising: receiving a reference signal (RS) transmission configuration; determining a set of aggregated transmission parameters to perform aggregated RS transmissions, wherein the determination is based on the RS transmission configuration; sending the set of aggregated RS transmission parameters to one or more of a network or other WTRUs in an aggregation group; receiving an indication to transmit an aggregated RS transmission; sending the indication to transmit the aggregated RS transmission to the other WTRUs in the aggregation group; and transmitting the aggregated RS transmission using the determined set of transmission parameters and the RS transmission configuration.

12. The method of claim 11 , wherein the set of aggregated RS transmission parameters comprises at least one of a subset of aggregated WTRUs, transmission resources, an antenna port mapping, or a transmission power for each WTRU in the aggregation group.

13. The method of claim 12, further comprising distributing the transmission power across WTRUs based on one or more of received pathloss information, maximum transmit power of each WTRU, or a power scaling factor associated with the aggregated RS transmission.

14. The method of claim 12, wherein the set of aggregated RS transmission parameters comprises the antenna port mapping.

15. The method of claim 14, further comprising determining the antenna port mapping of antenna ports of different WTRUs in the aggregation group to respective RS ports based on a received configuration indicating an RS port allocation scheme for the aggregated RS transmission.

16. The method of claim 11 , further comprising: receiving a set of non-aggregated transmission parameters to perform non-aggregated RS transmissions; receiving an additional indication that indicates whether to transmit the aggregated RS transmission or the non-aggregated RS transmissions; and determining whether to use the set of aggregated transmission parameters or the set of nonaggregated transmission parameters to perform a transmission based on the additional indication.

17. The method of claim 11 , wherein the indication to transmit the aggregated RS transmission comprises one or more of an RS resource identifier (ID), a radio network temporary identifier (RNTI), or an indication source.

18. The method of claim 17, wherein the indication to transmit the aggregated RS comprises an RS resource ID, wherein the RS resource ID corresponds to an RS resource set configured for an aggregation group transmission mode, and wherein the RS is a sounding reference signal (SRS).

19. The method of claim 11 , further comprising selecting an RS resource set based on a received aggregation configuration, wherein the aggregation configuration indicates an RS usage mode associated with the aggregation group, to determine the set of transmission parameters.

20. The method of claim 11 , further comprising determining the set of transmission parameters by selecting a subset of WTRUs for aggregated RS transmission based on one or more of an indication of collocation, an indication of synchronization timing, or an indication of supported antenna ports received from a group coordinator.