Reconfigurable smart surface channel state information

Abstract

Systems, methods, and tools associated with a wireless communication network including a reconfigurable smart surface (RIS) are described herein. A wireless transmit / receive unit (WTRU) in such a communication network may receive measurement configuration information, which may indicate at least a first measurement resource and a second measurement resource. The first measurement resource may be associated with a first transmit path associated with a first subset of elements of the RIS, while the second measurement resource may be associated with a second transmit path independent of the RIS. The WTRU may perform measurements based on the measurement configuration information, and may send a report to the network regarding at least one of the measurements.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 346,173, filed on May 26, 2022, the disclosure of which is incorporated herein by reference in its entirety. Background Art

[0003] Channel state information (CSI) acquisition may be performed in a wireless communication system, for example, based on reporting by a wireless transmit / receive unit (WTRU). The reporting may be based on measurements of reference signals such as a channel state information reference signal (CSI-RS). Reconfigurable smart surfaces have emerged as a promising technology for wireless communications, but problems associated with reconfigurable smart surfaces need to be addressed. Summary of the invention

[0004] Systems, methods, and tools associated with a wireless communication network including a reconfigurable smart surface (RIS) are described herein. A wireless transmit / receive unit (WTRU) as described herein may include a processor, a receiver, a transmitter, and / or a memory, etc. as described herein. The WTRU may be configured to perform and may perform the actions described herein. The WTRU may receive measurement configuration information (e.g., from a network device such as a base station), wherein the measurement configuration information may indicate at least a first measurement resource and a second measurement resource (e.g., in the same measurement resource set or in different measurement resource sets). The first measurement resource may be associated with a first transmission path, the first transmission path being associated with a first subset (a first row, a first column, or a first combination) of elements of a reconfigurable smart surface (RIS) (e.g., transmissions along the first transmission path may be reflected by the first subset of elements of the RIS), and the second measurement resource may be associated with a second transmission path independent of the RIS (e.g., transmissions along the second transmission path may be directly from the network device to the WTRU, e.g., without being reflected by the RIS). The WTRU may perform a first measurement using the first measurement resource indicated by the measurement configuration information, and may perform a second measurement using the second measurement resource indicated by the measurement configuration information. The first measurement may be performed based on a first reference signal received via the first transmission path, and the second measurement may be performed based on a second reference signal received via the second transmission path. The WTRU may send a report regarding at least one of the first measurement or the second measurement to the network device (e.g., the report may indicate results of the first measurement and / or the second measurement).

[0005] At least one of the first reference signal or the second reference signal described herein may include a channel state information (CSI) reference signal, and the report sent to the network device may include a CSI report (e.g., the measurement configuration information may indicate a corresponding channel quality parameter to be measured and reported). The first reference signal and the second reference signal may be received from the same multiple-input multiple-output (MIMO) transmitter associated with the network device.

[0006] In an example, the measurement configuration information described herein may indicate a third measurement resource associated with a third transmission path, the third transmission path being facilitated by a second subset of elements of the RIS (e.g., a second row, a second column, or a second combination of elements), and the WTRU may perform a third measurement based on a third reference signal received via the third transmission path. In an example, all or a subset of the first, second, and third reference signals may be time division multiplexed (TDM) and / or received during a reference signal transmission burst that may include multiple time slots.

[0007] In an example, the WTRU sending the report about at least one of the first measurement or the second measurement to the network device may include: the WTRU sending a first report indicating a result of the first measurement using a first uplink grant, and sending a second report indicating a result of the second measurement using a second uplink grant. In an example, the WTRU may indicate the results of the first measurement and the second measurement in the same report.

[0008] In an example, the measurement configuration information may indicate that the first measurement resource and the second measurement resource are associated with corresponding resource indexes, transmission times, transmission periodicities and / or transmission power offsets, and the WTRU may determine that the first measurement resource is associated with the first transmission path and the second measurement resource is associated with the second transmission path based on the corresponding resource indexes, transmission times, transmission periodicities or transmission power offsets associated with the first measurement resource and the second measurement resource.

[0009] A base station as described herein may include a processor, a receiver, a transmitter, a memory, etc. as described herein. The base station may be configured to perform and may perform the actions described herein. The base station may receive information about a RIS and may transmit a measurement configuration to a WTRU, wherein the measurement configuration information may indicate at least a first measurement resource and a second measurement resource. The first measurement resource may be associated with a first transmission path to the WTRU that may use the RIS, and the second measurement resource may be associated with a second transmission path to the WTRU that may be independent of the RIS (e.g., not using reflections from the RIS). The base station may (e.g., in response to transmitting the measurement configuration information to the WTRU) receive a report from the WTRU, wherein the report may indicate a result of at least one of a first measurement performed based on the first measurement resource or a second measurement performed based on the second measurement resource. The base station may determine whether to update a state of the RIS based on the report received from the WTRU. Based on the determination to update the state of the RIS, the base station may transmit a configuration message to the RIS, wherein the configuration message may indicate at least that the state of the RIS is to be updated. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented.

[0011] Figure 1B is an example of a method that can be used according to an embodiment of the present invention. Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) for use within the illustrated communication system.

[0012] Figure 1C is an example of a method that can be used according to an embodiment of the present invention. Figure 1A System diagram of an example Radio Access Network (RAN) and an example Core Network (CN) for use within the illustrated communication system.

[0013] Figure 1D is an example of a method that can be used according to an embodiment of the present invention. Figure 1A System diagram of another example RAN and another example CN used within the illustrated communication system.

[0014] Figure 2 is a diagram illustrating a RIS-assisted communication system.

[0015] Figure 3 is a diagram illustrating an example RIS CSI procedure.

[0016] Figure 4 is a diagram illustrating an example of signaling in a system including RIS.

[0017] Figure 5 is a diagram illustrating example operations that may be associated with a WTRU.

[0018] Figure 6 is a diagram illustrating example operations that may be associated with RIS.

[0019] 7(a), 7(b) and 7(c) are diagrams illustrating examples of organizing RIS elements into sub-surfaces.

[0020] Figure 8 is a diagram illustrating an example of a RIS sub-surface.

[0021] Fig. 9 is a diagram illustrating an example procedure for scene-specific RIS sub-surface configuration updates.

[0022] Fig.10 is a diagram illustrating an example of element-by-element RIS signaling.

[0023] Fig.11 is a diagram illustrating an example of RIS signaling for each sub-surface.

[0024] Fig.12 is a diagram illustrating an example of CSI-RS resources.

[0025] Fig.13 is a diagram illustrating an example of multi-port CSI-RS resources.

[0026] Figure 14(a) to Figure 14(i) is a diagram illustrating an example of multi-port CSI-RS resources with TDM antenna ports.

[0027] Fig.15 is a diagram illustrating an example of a plurality of multi-port CSI-RS resources.

[0028] Fig.16 is a diagram illustrating an example of multiple CSI-RS resource sets in a CSI resource setting.

[0029] Fig.17 is a diagram illustrating an example of multiple CSI-RS resource sets in a CSI resource setting.

[0030] Fig.18 is a diagram illustrating an example of 8-port CSI-RS resources.

[0031] Fig.19 is a diagram illustrating an example of 8-port CSI-RS resources.

[0032] 20(a) and 20(b) are diagrams illustrating examples of CSI-RS resources associated with two users (eg, two WTRUs).

[0033] 21(a) and 21(b) are diagrams illustrating examples of a mapping order. DETAILED DESCRIPTION

[0034] Figure 1A 1 is a diagram illustrating an example communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through sharing of system resources (including wireless bandwidth). For example, the communication system 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 multi-carrier (FBMC), etc.

[0035] like Figure 1A As shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, RAN 104 / 113, CN 106 / 115, public switched telephone network (PSTN) 108, Internet 110 and other networks 112, but it should be understood 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 “STA”) may be configured to send and / or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0036] The communication system 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 that is configured to 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 Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an evolved Node B (eNB), a Home Node B, a Home evolved Node B, a next generation Node B (gNB), an NR Node B, a site controller, an access point (AP), a wireless router, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0037] 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), a relay node, etc. The base station 114a and / or the base station 114b may be configured to send and / or receive wireless signals on one or more carrier frequencies (which may be referred to as cells (not shown)). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrums. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, a cell associated with the base station 114a may be divided into three sectors. Therefore, in one embodiment, the base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In one 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 send and / or receive signals in a desired spatial direction.

[0038] 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).

[0039] More specifically, as noted above, the communication 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, etc. 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 use Wideband CDMA (WCDMA) to establish the air interface 115 / 116 / 117. 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).

[0040] In one 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) that may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0041] In 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).

[0042] In one 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 together implement LTE radio access and NR radio access, for example using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions transmitted to / from multiple types of base stations (e.g., eNBs and gNBs).

[0043] 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, CDMA2000EV-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), etc.

[0044] Figure 1A The base station 114b in the example may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a business location, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, 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 one 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 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 micro-micro cell base station or a femto cell base station. As Figure 1A As shown, base station 114b may have a direct connection to Internet 110. Therefore, base station 114b may not need to access Internet 110 via CN 106 / 115.

[0045] 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 different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not described in detail in the text and video, the CN 106 / 115 may be 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 different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Figure 1AAlthough not shown in the figure, 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 utilize NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0046] The CN 106 / 115 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides 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), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired communication networks and / or wireless communication 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.

[0047] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication 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 via different wireless links). Figure 1A The illustrated WTRU 102c 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.

[0048] Figure 1B is a system diagram illustrating an example WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, 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. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0049] 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 associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal decoding, 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. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0050] The send / receive element 122 may be configured to send a signal to a base station (e.g., base station 114a) or receive a signal from the base station via an air interface 116. For example, in one embodiment, the send / receive element 122 may be an antenna configured to send and / or receive an RF signal. In one embodiment, the send / receive element 122 may be a transmitter / detector configured to send and / or receive, for example, an IR, UV or visible light signal. In another embodiment, the send / receive element 122 may be configured to send and / or receive both an RF signal and an optical signal. It should be understood that the send / receive element 122 may be configured to send and / or receive any combination of wireless signals.

[0051] Although the transmit / receive element 122 Figure 1B Although depicted as a single element in the figure, 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.

[0052] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. For example, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0053] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an 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 a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a 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 a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0054] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control 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, etc.

[0055] 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 from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0056] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules 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 electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, module, a frequency modulation (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, etc. Peripheral device 138 may include one or more sensors, which may be one or more of the following: 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.

[0057] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for both 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 for reducing and / or substantially eliminating self-interference via signal processing performed via hardware (e.g., a choke) or via a processor (e.g., a separate processor (not shown) or via the processor 118). In an embodiment, the WRTU 102 may include a half-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for both UL (e.g., for transmission) or downlink (e.g., for reception)) may be concurrent and / or simultaneous.

[0058] Figure 1C 1 is a system diagram illustrating the RAN 104 and the CN 106 in accordance with one 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.

[0059] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-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 evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0060] Each of the evolved Node 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, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0061] Figure 1C The illustrated CN 106 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 is depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than a CN operator.

[0062] The MME 162 may be connected to each of the evolved Node-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, etc. 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.

[0063] The SGW 164 may be connected to each of the evolved Node-Bs 160a, 160b, 160c in the RAN 104 via an 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 the user plane during an inter-evolved Node-B handover, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, and the like.

[0064] 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.

[0065] 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 be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts 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 other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers.

[0066] Although the WTRU Figures 1A to 1D Although described as wireless terminals, it is contemplated that in certain representative embodiments, such terminals may (eg, temporarily or permanently) use a wired communications interface with a communications network.

[0067] In a representative embodiment, the other network 112 may be a WLAN.

[0068] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for a BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or carries traffic away from the BSS. Traffic originating from outside the BSS and destined for the STA may be reached by the AP and may be delivered to the STA. Traffic originating from the STA and destined for a target outside the BSS may be transmitted to the AP to be delivered to the corresponding target. Traffic between STAs within the BSS may be transmitted by the AP, for example, wherein the source STA may transmit traffic to the AP, and the AP may deliver traffic to the target STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic may be transmitted between the source STA and the target STA (e.g., directly between them) using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (eg, all STAs in the STA) may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad-hoc" communication mode.

[0069] When using the 802.11ac infrastructure operation mode or a similar operation mode, the AP may send beacons on a fixed channel (such as a primary channel). The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a width dynamically set via signaling. The primary channel may be a working channel of the BSS and may be used by the STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including the AP) may listen to the primary channel. If the primary channel is listened / 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.

[0070] High throughput (HT) STAs may communicate using a 40 MHz wide channel, for example, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0071] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz channels and / or 80MHz channels can be formed by combining continuous 20MHz channels. 160MHz channels can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and the data can be sent by sending STA. At the receiver of the receiving STA, the above-mentioned operation for 80+80 configuration can be reversed, and the combined data can be transmitted to the medium access control (MAC).

[0072] 802.11af and 802.11ah support operating modes below 1GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support instrument type control / machine type communications, such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0073] WLAN systems that can support multiple channels and channel bandwidths (such as 802.11n, 802.11ac, 802.11af, and 802.11ah) include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA (which supports the minimum bandwidth operation mode) from all STAs operating in the BSS. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) a 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operation modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (supporting only a 1MHz operation mode) is sending to the AP, the entire available band may be considered busy even if most of the band remains idle and may be available.

[0074] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0075] Figure 1D 1 is a system diagram illustrating the RAN 113 and the CN 115 in accordance with an embodiment. As noted above, the RAN 113 may employ 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.

[0076] 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, the gNBs 180a, 180b may utilize beamforming to send signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may, for example, use multiple antennas to send wireless signals to and / or receive wireless signals from the WTRU 102a. In one 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 an unlicensed spectrum, while the remaining component carriers may be on a licensed spectrum. In one embodiment, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNB 180a and gNB 180b (and / or gNB 180c).

[0077] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with parameter sets that may be scalable. For example, 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 the gNBs 180a, 180b, 180c using subframes or Transmission Time Intervals (TTIs) of varying or scalable lengths (e.g., containing varying numbers of OFDM symbols and / or varying absolute time lengths over time).

[0078] 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 a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c while not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate / connect with the gNB 180a, 180b, 180c while also communicating / connecting with another RAN, such as the eNodeB 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more eNodeBs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNodeB 160a, 160b, 160c may act as a mobility anchor for the WTRUs 102a, 102b, 102c, and the gNB 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0079] Each of the gNBs 180a, 180b, 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, support of network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b, routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0080] Figure 1DThe illustrated CN 115 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possible data networks (DNs) 185a, 185b. Although each of the foregoing elements is depicted as part of the CN 115, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0081] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different PDU sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of NAS signaling, mobility management, etc. The AMF 182a, 182b may use network slicing in order to customize CN support for the WTRU 102a, 102b, 102c based on the type of services utilized by the WTRU 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 mobile broadband (eMBB) access, services for machine type communication (MTC) access, etc. 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.

[0082] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 115 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 115 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0083] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the 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, etc.

[0084] 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 acts 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 other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to local data networks (DNs) 185a, 185b via the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and the N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0085] Given that Figures 1A to 1D as well as Figures 1A to 1D Corresponding to the description of the present invention, one or more or all of the functions described herein with reference to one or more of the following may be performed by one or more simulation devices (not shown): WTRU102a-d, base station 114a-b, evolved Node B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b and / or any other device described herein. The simulation device may be one or more devices configured to mimic one or more or all of the functions described herein. For example, the simulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0086] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, one or more simulation devices may perform one or more functions 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. One or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device may be directly coupled to another device for testing purposes and / or may use over-the-air wireless communications to perform testing.

[0087] One or more simulation devices can perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test scenario in a test laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. One or more simulation devices can be test equipment. Direct RF coupling and / or wireless communication via an RF circuit system (e.g., which can include one or more antennas) can be used by the simulation device to send and / or receive data.

[0088] The CSI may be used to adapt transmission schemes, such as transmitter precoding. CSI acquisition may be based on reference signal measurements and reporting by the WTRU, such as measurements of the CSI-RS. In the presence of a reconfigurable intelligent surface (RIS) in a wireless communication environment (e.g., a radio-based environment), the CSI-related procedures may be extended to incorporate RIS states in the presence of additional links between the WTRU and the RIS (referred to herein as WTRU-RIS links or paths) and / or additional links between the base station and the RIS (referred to herein as BS-RIS links or paths).

[0089] Methods for RIS CSI acquisition (e.g., RIS CSI determination and / or reporting) may be provided. Operations based on sub-surfaces (e.g., which may correspond to subsets of RIS elements) may be performed to reduce the complexity of channel estimation and / or CSI calculations associated with the RIS and / or to reduce CSI overhead (e.g., for RIS with multiple elements). Suitable CSI-RS transmission schemes may be implemented. RIS-related measurements and / or parameters may be included in CSI reports.

[0090] For example, a RIS may be included in a wireless communication network because of its ability to enhance the propagation of wireless signals. The RIS may include a flat surface that includes a large number of elements, such as scattering elements of sub-wavelength size (referred to herein as RIS elements). The RIS elements may utilize an electronic RIS controller to change (e.g., dynamically change) the electromagnetic properties (e.g., phase and / or amplitude) of the impact signal. For example, by appropriately optimizing the state of the RIS elements, the impact signal may be directed to a desired receiver to improve communication performance (e.g., achieve higher spectral efficiency, enhanced coverage, etc.). In addition to providing an improved wireless communication environment, the RIS elements may also support applications such as joint communications, sensing, and / or wireless power transfer. The RIS elements may also support features such as reflection, refraction, focusing, collimation, polarization, etc. The RIS may be classified as passive, semi-active, or active. A passive RIS may shift (e.g., only shift) the phase of the impact signal and may include multiple passive elements. A semi-active RIS and / or an active RIS may provide phase shift and / or amplification gain. A semi-active RIS may include a mixture of active and passive elements, while an active RIS may include all active elements (e.g., only active elements). Active RIS elements may have sensing capabilities. Since the RIS may be considered a communication or network node, RIS-assisted communication may involve at least three nodes, such as a base station (BS), a WTRU, and a RIS. Communication paths may be established to include a BS-RIS-WTRU path and a BS-WTRU communication path. Various communication procedures including initial access, beamforming, control signaling, channel acquisition, CSI measurement and reporting, etc. may be updated to enable RIS-assisted communication paths and / or support the introduction of RIS into the network. For example, channel acquisition and / or CSI reporting may be adapted to RIS-assisted communication scenarios.

[0091] Hereinafter, the term "RIS" may refer to a RIS, a combination of a RIS and a RIS controller, or a RIS controller. A base station may communicate with a RIS (e.g., via an air interface) and provide control information to the RIS. A RIS system may include one or more RIS elements, which may be organized into sub-surfaces (e.g., each sub-surface may include a subset of elements of the RIS). In some examples provided herein, the RIS may be described in the context of a downlink (DL), but the same or similar techniques may also be applicable to an uplink (UL).

[0092] For ease of description, a single-antenna WTRU and a narrowband system (e.g., a subcarrier of an OFDM-based system) may be used in the examples provided herein. However, the techniques described in those examples may also be applicable to multi-antenna WTRUs, such as WTRUs that may combine multiple received signals into a single signal based on receiver processing (e.g., using analog, digital, or hybrid beamforming or combining techniques). In an example, such receiver processing may be applied to a radio channel.

[0093] In a first example model, the RIS system may utilize only one element of the RIS (eg, one RIS element out of M RIS elements), such as Figure 2 In this model, the equivalent baseband received complex-valued scalar signal y at the WTRU m (eg, a signal received via a RIS reflected path and / or a direct path in the form of a complex-valued scalar) may be given by Equation 1 below.

[0094] y m =(b m a′ m φ m +d′)Ps+z=(c′ m φ m +d′)Ps+z (1)

[0095] Where s may represent a complex-valued scalar symbol, such as a known reference (eg, pilot) symbol, and P may represent a scalar symbol having a dimension of N T ×1 complex-valued pre-decoding vector (e.g., N T It can be the number of transmit antennas or antenna ports at the transmit reception point (TRP), and d'=[d'0...d' NT-1 ] may represent a complex-valued channel between the TRP and the WTRU (e.g., excluding channels with dimensions 1×N T In addition, a' m A complex-valued vector channel (e.g., of dimension 1×N) between TRP and RIS elements may be represented T ), c' m =b m a' m The concatenated complex-valued vector channel (e.g., of dimension 1×N) between the TRP, RIS element m, and the WTRU may be represented. T ), and φ m A complex-valued scalar RIS element factor representing a RIS element m, where m = 1, ..., M. In addition, b m may represent a complex-valued scalar channel between the RIS element and the WTRU, and z may represent additive noise and / or interference.

[0096] In the case of passive RIS, the factor φ mmay have a fixed amplitude, such as, for example, a unit amplitude (|φ m |=1). In the case of active RIS or hybrid RIS, φ m The amplitude of can be variable and / or controllable. In some examples (e.g., for a passive RIS), the RIS element can be turned off (e.g., φ m =0 or φ m ≈0). At a given time, a RIS element can be in a specific state (φ m ), the particular state may be assumed to be applicable to one or more (eg, all) subcarriers of a particular bandwidth.

[0097] The terms "reference signal (RS)" and "pilot" are used interchangeably herein. In the case of OFDM, an RS or pilot may include multiple (eg, known) symbols that may be mapped to different subcarriers and / or OFDM symbols.

[0098] For example, the TRP pre-coding P can be included in the TRP to RIS channel to simplify Figure 2 The following equation 2 can be applied to such scenarios:

[0099] y m =(b m a m φ m +d)s+z=(c m φ m +d)s+z (2) where d = d'P may represent a complex-valued scalar effective direct TRP to RIS channel (eg, including TRP precoding), a m =a' m P may represent a complex-valued scalar channel between TRP and RIS elements, and c m =b m a m It may represent a concatenated complex-valued scalar channel from the TRP to the mth RIS element and further to the WTRU.

[0100] In a second example model, the RIS system may utilize multiple RIS elements of the RIS (e.g., all M RIS elements of the RIS). Such a system may, for example, transmit signals (c m φ m s) is incorporated into the system to establish, as shown in equation 3 below:

[0101] y=((a⊙b)Φ+d)s+z=(cΦ+d)s+z (3)

[0102] Where a may represent a complex-valued vector channel of dimension 1×M between the TRP and the RIS (e.g., M may be the number of RIS elements), b may represent a complex-valued vector channel of dimension 1×M between the RIS element and the WTRU, and c=a⊙b=b⊙a may represent the element-wise (e.g., Hadamard) vector product of a and b. Additionally, Φ may represent a factor φ of dimension M×1 containing M RIS elements. m is a complex-valued vector of , and may correspond to a RIS state. In an example (eg, in the case of a rectangular RIS), M x M may represent the number of RIS elements in a first direction (eg, horizontally). y M may represent the number of RIS elements in the second direction (eg, vertical), and M may be equal to M x *M y .

[0103] If RIS is present in a communication network, there may be multiple paths for a receiver node (e.g., WTRU), such as, for example, a RIS-assisted path (e.g., a BS-RIS-WTRU path) and a direct path (e.g., a BS-WTRU path, which may also be referred to herein as a RIS-independent path). A RIS-assisted path may include (e.g., any) path involving a RIS (e.g., using reflections of a RIS). A direct or RIS-independent path may exclude a RIS (e.g., a signal transmitted on a direct path may not be reflected by a subset of sub-surfaces or elements of a RIS). A direct path may be used for signals (e.g., superimposed signals) or combined signals (e.g., in the case of a multi-TRP transmission scheme) from multiple (e.g., all) reflection paths. Channel properties may be controlled by introducing phase and / or amplification gain to an impinging signal on a RIS surface. Channel estimation (e.g., CSI measurements) may be performed in a RIS-assisted system (e.g., on a direct path and / or a RIS-assisted path) to improve communication performance.

[0104] When described herein, channel estimation may include cascaded channel estimation and / or separate channel estimation. In cascaded channel estimation, the channel estimation may be performed at the WTRU and / or the base station (e.g., gNB) in the case of downlink or uplink channel estimation, respectively (e.g., by Figure 2 The b shown m a′ m φ m In the separate channel estimation, the channel associated with the BS-RIS path (e.g., a′ m ) and / or channels associated with the RIS-WTRU path (e.g., b m ). The specific channel estimation technique applied by the WTRU or base station may depend on the RIS state.

[0105] An example method for cascaded channel estimation may include an "on-off" method. In the on-off method, channel estimation may be performed as a multi-step (e.g., two-step) process, where in a first step, one or more (e.g., all) RIS elements may be turned off and a direct channel may be estimated, and in a second step, RIS elements of the RIS may be turned on (e.g., one by one) and the channel gain introduced by each RIS element may be calculated. The overall channel may be estimated by combining the channel gain from the direct path and the channel gain from the RIS elements.

[0106] Another example method for concatenated channel estimation may include a "turn on" method that may avoid turning off the RIS elements during pilot signal transmission. Different Φ (factor) vectors that may be known to the WTRU, such as, for example, orthogonal vectors, may be applied during pilot signal transmission. The direct channel and / or the RIS auxiliary channel may be estimated by inverting the effects of the Φ vector.

[0107] The large number of RIS elements may make the channel estimation task computationally intensive. Channel estimation in a RIS-assisted communication system may be performed on multiple communication paths including, for example, RIS-assisted communication paths and direct (e.g., RIS-independent) communication paths. Hardware limitations and / or infinite resolution phase shifts may make channel estimation difficult in practical implementations. The resolution of the phase shifter may define the number of possible states that can be achieved by the RIS. Discrete phase shifters (e.g., which may be actually utilized) may introduce quantization errors that may affect the channel estimation at the receiver.

[0108] Channel estimation may be performed at a granularity of each RIS element. For example, to estimate the concatenated channel c and / or the direct channel d in Equation 3, the network device may send multiple known pilot (reference) signals in symbol s. Since c may include M elements and d may include one element, M+1 pilots may be used to estimate the channel coefficients.

[0109] To simplify notation, the same pilot symbol s (which may also be referred to herein as a pilot signal) may be assumed in the M+1 occasions herein, but a person skilled in the art will appreciate that the pilot symbol may also be different in different occasions (e.g., according to a specific complex-valued sequence, as long as the sequence is known to the WTRU). The received pilot symbols may be combined, for example, according to the following equation 4:

[0110] y=hΘs+z (4)

[0111] where y=[y0 … y M ] may represent M+1 received pilot symbols, and h=[dc] may represent a 1×(M+1) vector having a direct channel and M channels via RIS. Θ may be equal to where Φ i z = [z0 … z M ] may represent a 1×(M+1)-dimensional vector associated with received noise and / or interference.

[0112] In an example (eg, where Θ has a full rank known to the WTRU), the channel may be estimated based on y, for example, according to Equation 5 below. The channel may also be estimated based on a minimum mean square error (MMSE).

[0113]

[0114] Different methods can be used to design Φ i For example, in the on-off method described herein, RIS elements (e.g., all RIS elements) may be turned off during a pilot symbol such as the first pilot symbol, which may result in Φ0=0 or Φ0≈0. This may result in a received symbol of y0=ds+z0.

[0115] The direct channel d may be estimated by the WTRU. For example, during pilot symbols 1 to M, the RIS elements may be turned on one by one (e.g., while other elements are still turned off). This may result in the i-th pilot symbol being received, for example, as shown in Equation 6.

[0116] y i =(cΦ i +d)s+z=(c i φ i +d)s+z i Where i=1,…,M (6)

[0117] For i>0, Φ i may have zero values ​​(eg, all elements are zero values), except that the i-th element of the vector may be equal to 1 (eg, Φ i =1). For example, Φ1 can be equal to [1 0 … 0] T , Φ2 can be equal to [0 1 0 … 0] T , and so on. As another example, [Φ1 … Φ M ] can be equal to I M , where I M It may be an M-dimensional identity matrix. In these examples, it may be assumed that the RIS elements may be turned on in an order based on the RIS element index, but those skilled in the art will appreciate that the elements may be turned on in any order.

[0118] In an example (e.g., such as the opening method described herein), Φ iΘ may be a vector with no zero-valued elements. This may mean that multiple (e.g., all) RIS elements may be turned on during pilot symbol transmission. Θ may be a DFT matrix and / or a Hadamard matrix, etc., and the RIS state during pilot transmission may be based on columns of the DFT matrix or the Hadamard matrix. In at least these examples, Θ -1 Can be equal to Θ T , which simplifies the implementation.

[0119] DL CSI acquisition (e.g., a first mode of DL CSI acquisition) may be based on the WTRU performing measurements on one or more CSI-RS and reporting corresponding CSI measurement results. DL CSI acquisition (e.g., a second mode of DL CSI acquisition) may be based on the WTRU sending a sounding reference signal (SRS) (e.g., including antenna switching between antennas that can be used for DL ​​reception), the network device performing CSI measurements and / or assuming UL / DL reciprocity (e.g., CSI estimated on the UL may be applicable to the DL).

[0120] The WTRU may be configured to perform channel measurements and / or determine (e.g., calculate) CSI using at least one CSI-RS resource, which may be associated with one or more antenna ports. The WTRU may be configured to perform interference and / or noise measurements using at least one CSI-RS resource (e.g., by measuring the signal-to-interference-plus-noise ratio (SINR)). One or more CSI-RS resources may be grouped into CSI-RS resource sets. The CSI-RS resources may be non-zero power (NZP) CSI-RS resources, where the WTRU may assume that a specific RS is transmitted. The CSI-RS resources may be CSI-RS resources used for interference measurement, where the WTRU may assume that no RS is transmitted. Thus, the CSI-RS resources and resource sets described herein may be, for example, non-zero power (NZP) CSI-RS resources and resource sets, or interference measurement (IM) CSI-RS resources or resource sets. For brevity, the terms "CSI-RS resources" and "CSI-RS resource sets" may be used herein to refer to NZP and / or IM CSI-RS resources and resource sets.

[0121] The CSI-RS resources may be periodic, semi-persistent (e.g., capable of being activated / deactivated), or aperiodic (e.g., triggered by a specific condition). The WTRU may be configured with periodic, semi-persistent, or aperiodic CSI reporting. In an example, periodic CSI reports may be sent on the PUCCH, aperiodic CSI reports may be sent on the PUSCH, and semi-persistent CSI reports may be sent on the PUCCH or on the semi-persistent PUSCH.

[0122] The CSI report may be based on channel measurements performed using a resource set, such as a CSI-RS resource set. (Each) channel measurement resource may be associated with an interference measurement resource and / or a non-zero power CSI-RS resource used for channel measurement. The WTRU may report CSI corresponding to one or more resources in the resource set used for channel measurement. If the resource set includes multiple resources, the WTRU may report a resource index, for example, to identify the corresponding resource used for measurement. Such a resource index may, for example, include a CSI-RS resource indicator (CRI) or an SSB resource indicator (SSBRI).

[0123] In an example (e.g., where a multi-port CSI-RS is used as a channel measurement resource), the WTRU may be configured to calculate one or more precoding matrix indicators (PMIs), which may include a wideband PMI and / or multiple subband PMIs. The PMI may, for example, correspond to a precoding vector or precoding matrix selected directly from a codebook. The PMI may include a combination (e.g., a linear combination) of multiple precoding vectors or precoding matrices from the codebook. In an example, the CSI report may include a channel quality indicator (CQI), which may be a wideband CQI (e.g., where wideband PDSCH transmission is performed) and / or a subband CQI (e.g., where subband PDSCH transmission is performed). If the CSI report includes a PMI, the CQI may correspond to a set of layers associated with the PMI.

[0124] The WTRU may receive (e.g., be scheduled with) one or more CSI-RS resources and may use the CSI-RS resources to acquire downlink CSI. The WTRU may perform measurements on the acquired channels and may send the acquired CSI to the base station (e.g., in a corresponding CSI report) based on the measurements performed (e.g., via PUCCH or PUSCH). In RIS-assisted communication, there may be multiple (e.g., two) communication paths between the base station and the WTRU, including, for example, a first path involving RIS (e.g., using RIS to reflect the signal) and a second path independent of RIS (e.g., the second path may be a direct path between the base station and the WTRU that is not assisted by RIS). When RIS is present in the communication system, RIS may introduce phase shift and / or amplification to the impinging signal, for example, based on predefined or preset RIS states that may be configurable by a RIS controller. RIS may reflect an incident beam in a desired direction. RIS states may be valid portions of a reference signal received at the WTRU, which may be predefined or preset due to the presence of a RIS-assisted communication path.

[0125] Conventional CSI acquisition procedures may not support RIS-assisted communication paths and / or may not be able to distinguish between direct paths and RIS-assisted paths. Techniques disclosed herein may allow a WTRU to acquire knowledge about the state of the RIS (e.g., which may be communicated to the WTRU explicitly or implicitly from a base station or RIS controller) and estimate channels (e.g., CSI) associated with the RIS-assisted path. Using these techniques, configuration parameters and / or mechanisms may be adapted (e.g., optimized) based on the presence of the RIS to improve the performance of the wireless communication system.

[0126] Conventional CSI reports (such as those that include conventional RI, PMI, and / or CQI parameters) may not be sufficient to capture the impact of the RIS state. CSI measurements (e.g., estimates) by the WTRU and / or CSI reports to the base station may be used by the base station for link adaptation (e.g., such as adjusting the BS transmission scheme in terms of modulation and coding), for multi-antenna precoding, and / or for frequency domain resource allocation. Adjustments to the RIS state made by the base station and / or the WTRU may involve improving received signal quality, such as that associated with precoding and / or frequency selective scheduling, and / or may involve achieving a specific block error rate, such as that associated with modulation and coding scheme (MCS) selection. For example, adjustment of the RIS state may be similar to predecoder selection in terms of improving received signal quality. Conventional CSI procedures may not support efficient CSI-based RIS state adjustment.

[0127] As described herein, a wireless communication system may include various nodes, such as one or more base stations (e.g., gNBs), one or more TRPs, one or more RISs, one or more WTRUs, etc. The CSI procedures for such systems may be configured to accommodate the RISs. Figure 3 An example of such a CSI procedure is illustrated. Figure 4 Example signaling that may occur in a communication system including a RIS is illustrated. It should be noted that various examples may also be performed Figure 3 Additional operations not shown in the examples and may be omitted in various examples Figure 3 In addition, although Figure 3 The RIS states in the example may be described as being defined at the RIS element level, but the RIS states may also be defined at the sub-surface level (e.g., a sub-surface may include multiple elements). Figure 4 Additional signaling not shown in the examples and may be omitted in various examples Figure 4 Some signaling shown.

[0128] like Figure 3 and / or Figure 4As shown, the RIS may signal (e.g., report or otherwise indicate) the capabilities of the RIS to a base station (BS). This may be followed by the base station configuring the RIS and / or the WTRU. The WTRU may perform RIS CSI measurements, for example, based on the CSI-RS sent by the base station. In the case of semi-persistent or aperiodic CSI-RS, the WTRU may receive corresponding activation or trigger signaling that may be sent by the base station. The base station may indicate to the RIS that certain RIS states may be used at certain times (e.g., using sub-surface level RIS states in symbols that may carry CSI-RS for RIS CSI). The operation may be shown as Figure 4 RIS state scheduling in the RIS. The WTRU may report the RIS CSI to the base station (e.g., after RIS CSI measurement and / or calculation). Based on the RIS CSI report, the base station may perform RIS parameter interpolation, for example, to obtain RIS element-level RIS states, and may indicate the RIS element-level RIS states to the RIS, for example, for later use. Subsequently, additional CSI measurements and reports (e.g., traditional CSI measurements and reports) may be performed based on the RIS element-level RIS states available at the RIS. In the case of semi-persistent or aperiodic CSI-RS or CSI reporting, the WTRU may receive corresponding activation or trigger signaling. The base station may schedule the use of RIS element-level RIS states during certain time periods (e.g., in symbols that may carry CSI-RS resources and / or in symbols that may carry CSI reports). For example, after CSI measurement and / or reporting, DL and / or UL transmissions may be performed on the PDSCH and / or PUSCH, respectively. The base station may schedule the RIS to use the appropriate RIS state in symbols that may carry DL and / or UL transmissions. In this way, enhanced performance may be obtained based on RIS state (eg, RIS element level RIS state).

[0129] Different types or categories of RIS may be supported in the wireless communication systems described herein. For example, the RIS in a communication system may differ in terms of the number of RIS elements (e.g., M), the number of horizontal / vertical RIS elements (e.g., M), and the number of RIS elements. x and / or M y ), range and / or resolution of RIS element magnification and / or phase shifting, sub-surface and / or parameter interpolation capabilities, etc. A range as described herein may include, for example, a minimum and maximum value for RIS element magnification. A resolution as described herein may include a step size between values ​​supported within a range. For example, a RIS may support a phase shift resolution of π / 16. A resolution or range capability may list the supported values.

[0130] RIS capabilities as described herein may include a set of parameters related to various aspects that may differ between different RISs. RIS categories may be defined based on one or more capabilities. A RIS may connect to a network device and report the capabilities and / or categories (e.g., category 1, category 2, etc.) of the RIS to the network device (e.g., Figure 3 and Figure 4 For example, the RIS may use RRC messages to report its capabilities and / or categories.

[0131] RIS may be configured by a network device such as a base station (e.g., gNB), such as Figure 3 and Figure 4 . The configuration may be performed via one or more RRC configuration messages (e.g., via RRC signaling). When referred to herein, the term "RIS state" may correspond to certain settings of RIS element factors (e.g., such as amplification, phase shift, etc.), and the terms "RIS configuration" and "sub-surface configuration" may correspond to RRC configuration information associated with the RIS that may be conveyed via RRC signaling. In addition, the term "legacy" may refer to operations that may not involve or be independent of the RIS (e.g., including CSI measurement and reporting operations).

[0132] Configuration information (e.g., parameters) of the RIS may include one or more of the following. The configured information may include sub-surface related parameters, such as sub-surface configuration IDs associated with multiple sub-surfaces and / or multiple sub-surface configurations (e.g., the sub-surface configuration IDs may be used to identify the corresponding sub-surface configurations). The configured parameters may include the number of sub-surfaces (e.g., S), the number of horizontal sub-surfaces (e.g., S x ), the number of vertical sub-surfaces (e.g., S y ), the number of RIS elements per sub-surface, the number of RIS elements per horizontal sub-surface, the number of RIS elements per vertical sub-surface, the RIS element factor resolution (e.g., phase resolution), etc.

[0133] The configuration information of the RIS may include time domain configuration information for the sub-surface configuration and / or the RIS state, and the configuration information may indicate a time instance at which the sub-surface configuration and / or the RIS state may be used. The time domain configuration information may include, for example, a configuration ID (e.g., a sub-surface configuration ID, a RIS state ID, etc.) to which the time domain configuration information may be applied (e.g., the time domain configuration information may be included in the sub-surface and / or RIS state configuration). The time domain configuration information may indicate a time domain behavior of the configuration (e.g., periodic or semi-persistent), a periodicity of the configuration, a time offset and / or a duration (e.g., in terms of time slots, symbols, or milliseconds), a parameter set (e.g., an integer index μ, which may correspond to 2 -μThe time reference associated with the time domain configuration information may be given based on the timing of the cell in which the configuration may be provided to the RIS. The time domain configuration information may be applicable to periodic or semi-persistent time domain behavior.

[0134] The configuration information of the RIS may include trigger state configuration information, which may be applicable to the non-periodic time domain behavior of the sub-surface or the RIS state. The trigger state configuration information may indicate a trigger state set, wherein the trigger state may correspond to a parameter value included in the DCI. The trigger state configuration information may associate the trigger state with the sub-surface configuration (e.g., via the sub-surface configuration ID) and / or the RIS state (e.g., via the RIS state ID).

[0135] Configuration information of the RIS may include information indicating the corresponding range and / or resolution of RIS elements and / or sub-surface factors (e.g., magnification, phase shift, etc.) of the RIS. Such information may be provided, for example, in the form of one or more codebooks or a number of bits (e.g., bits for covering a corresponding range of phase shifts).

[0136] Configuration information for the RIS may include one or more RIS states and / or RIS state IDs that may be associated with one or more sub-surface configurations. In an example, a sub-surface configuration may not be provided, in which case an operation based on a RIS element may be performed. In an example, a sub-surface configuration may be provided at a RIS element level (e.g., each RIS element may be considered a sub-surface).

[0137] like Figure 3 and Figure 4 As shown, a network device such as a base station (BS) may configure a WTRU with parameters related to RIS CSI enhancement. Configuration parameters or configuration information related to RIS CSI may include one or more of the following. The configuration information may include sub-surface level configuration information, such as parameters of the sub-surface RIS configuration discussed herein. The configuration information may include information about sub-surface configurations that may be useful for the WTRU to perform RIS CSI calculations. For example, the WTRU may be informed about which sub-surfaces (or corresponding pilot signals) may be adjacent in a particular direction (e.g., along the x-axis of a 2D space) so that the WTRU may estimate a phase gradient across multiple sub-surfaces in that direction.

[0138] The configuration information may include conventional CSI reporting configuration information, such as, for example, channel quality related parameters to be measured (e.g., CQI related reporting configuration information). The configuration information may include enhanced CSI reporting configuration information, such as, for example, one or more RIS parameters of the RIS parameters described herein (e.g., RIS related channel quality parameters to be measured, such as RIS-QI, etc.). The configuration information may include conventional CSI resource configuration information. The configuration information may include enhanced CSI resource or resource set configuration information, such as, for example, an enhanced CSI-RS resource set configuration including S+1 CSI-RS resources (e.g., S may correspond to the number of sub-surfaces of the RIS). In an example, the WTRU may be configured with multiple CSI-RS resource sets, wherein one or more resource sets are dedicated to RIS CSI measurement and reporting, and one or more other resource sets are dedicated to conventional operations, such as conventional CSI acquisition, beam management, etc.

[0139] Based on the configuration information described herein, the WTRU may receive one or more reference signals, perform measurements of the reference signals, and calculate (e.g., determine) the CSI that may include one or more parameters associated with the RIS, such as Figure 3 and Figure 4 As illustrated. For example, the WTRU may estimate each sub-surface phase shift based on the set of enhanced CSI-RS resources associated with the RIS. Thus, the CSI report sent by the WTRU may include RIS-related CSI parameters (e.g., only RIS-related CSI parameters), or RIS and legacy CSI parameters (e.g., such as legacy CQI, PMI, RI, etc.). The WTRU may transmit the CSI report to a network device (e.g., a base station) (e.g., based on the configuration information described herein), for example, in one or more PUCCH transmissions or one or more PUSCH transmissions. Figure 3 and Figure 4 As illustrated. The WTRU may include the RIS CSI in the UL Control Information (UCI) or in the MAC Control Element (CE). The CSI report may also include one or more RIS parameters.

[0140] Based on the reported RIS CSI (which may include one or more RIS parameters, for example), the network device may interpolate the sub-surface level RIS state into the element level RIS state, such as Figure 3 and Figure 4As shown. The interpolation may be performed by the base station receiving the CSI report, by another network node (e.g., another base station or core network device), and / or by the RIS (e.g., a RIS controller), etc. If the interpolation is performed by another network node, the network (e.g., a base station responsible for configuring the RIS) may indicate the interpolated RIS state to the RIS (e.g., at each RIS element level) or configure the RIS with the interpolated RIS state, which may be associated with the RIS state ID. If the interpolation is performed by the RIS (e.g., a RIS controller), the network may indicate the RIS parameters reported by the WTRU to the RIS or configure the RIS with the RIS parameters reported by the WTRU. The RIS (e.g., a RIS controller) may perform the interpolation from the RIS parameters reported by the WTRU to each RIS element factor. The network may indicate the association between the resulting (e.g., after interpolation) RIS state and the RIS state ID. For example, if sub-surfaces are not used or configured, or if the sub-surface granularity is RIS elements (e.g., if each RIS element corresponds to a sub-surface), the interpolation may be omitted.

[0141] The CSI may be measured and / or reported at the RIS element level. For example, based on its configuration, the WTRU may receive one or more reference signals, perform measurements of the reference signals, and calculate (e.g., determine) CSI (e.g., CQI, RI, PMI, etc.) based on the measurements. The WTRU may perform channel measurements using one or more CSI-RS resources included in a CSI-RS resource set. A network device such as a base station may indicate or configure the RIS to use an element-level RIS state during the one or more CSI-RS resources. The network device may do so, for example, by configuring, indicating, triggering, and / or activating time domain configuration information for the element-level RIS state, which may overlap in time with the one or more CSI-RS resources. The network device may indicate or configure the RIS to use the element-level RIS state during a subsequent DL / UL transmission. The network may do so, for example, by configuring, indicating, triggering, and / or activating time domain configuration information for the RIS state, which may overlap in time with one or more of the DL / UL transmissions. DL transmissions may include PDCCH, PDSCH, CSI-RS, TRS and / or PRS transmissions, while UL transmissions may include PUCCH, PUSCH and / or SRS transmissions. The use of a particular RIS state may be dynamically indicated or scheduled, such as Figure 4 exemplified.

[0142] Figure 5 Example procedures associated with CSI measurement and reporting are illustrated (e.g., in Figure 3After one or more of the illustrated operations). As shown, at 502, the WTRU may be configured with RIS CSI and / or traditional CSI related configuration information. At 504, the WTRU may perform RIS CSI measurements and / or calculations, which may be based on one or more CSI-RS sent by the base station. In the case of semi-persistent or aperiodic CSI-RS, corresponding activation or trigger signaling may be performed (e.g., also performed at 504). At 506, the WTRU may report RIS CSI based on the RIS CSI measurements and / or calculations. At 508, the WTRU may perform traditional CSI measurement calculations (e.g., CSI independent of RIS), and may report the measurements and / or calculations (e.g., including CQI) to the base station at 510. In the case of semi-persistent or aperiodic CSI-RS or CSI reporting, corresponding activation or trigger signaling may be provided (e.g., performed at 510). At 512, the WTRU may perform DL reception and / or UL transmission (eg, on the PDSCH and / or PUSCH, respectively).

[0143] Figure 6 Example RIS procedures associated with CSI measurement and / or reporting are illustrated (e.g., which may be Figure 3 One or more of the illustrated RIS-side operations are performed afterwards).

[0144] In an example, the number of RIS elements on the RIS may be high, and performing channel estimation and / or CSI reporting at the RIS element level may be expensive (e.g., in terms of overhead and signaling). For example, the cost may be reduced by introducing sub-surface based estimation and reporting. The RIS elements may be distributed (e.g., organized or grouped) into S sub-surfaces, including, for example, S in a sub-surface. x horizontal elements and S y The distribution of RIS elements into sub-surfaces may be uniform (e.g., the number of RIS elements is the same for each sub-surface) or non-uniform (e.g., the number of RIS elements is different for different sub-surfaces). In the case of a multi-panel RIS, (e.g., each) panel may be considered a sub-surface, or (e.g., each) panel may be divided into multiple sub-surfaces.

[0145] Figures 7A to 7C illustrate examples of RIS elements distributed into sub-surfaces. Figures 7A and 7B illustrate examples of uniform distribution, while Figure 7C illustrates an example of non-uniform distribution. In situations where different RIS surfaces may be assigned to different users, the number of RIS elements or resources assigned to a user (e.g., WTRU) may be increased or decreased (e.g., a non-uniform RIS distribution may be used). A WTRU requesting more resources may be assigned a sub-surface having a larger size or dimension (e.g., having more RIS elements), while a WTRU with a less stringent request may be assigned a sub-surface having a smaller size or dimension (e.g., having fewer RIS elements).

[0146] The number of pilots (e.g., reference signals) used for CSI and / or channel acquisition may be M+1 for a RIS having M elements (e.g., in the case of element-by-element RIS channel estimation). As the size of the RIS surface increases, the computational complexity of the estimation process may increase greatly, making the channel estimation process inefficient and / or time consuming. In an example, channel estimation may be performed by dividing and / or grouping the RIS elements into smaller groups (e.g., which may be referred to as sub-surfaces herein) and performing channel estimation at the sub-surface level. Such a sub-surface may include a set of one or more RIS elements. The distribution of RIS elements into sub-surfaces may be uniform or non-uniform. In the case of a multi-panel RIS, (e.g., each) panel may be considered a sub-surface, or (e.g., each) panel may be further divided into multiple sub-surfaces. Figure 8 An example of dividing the RIS into six sub-surfaces (eg, S=6) is illustrated.

[0147] RIS states may be configured at the sub-surface level (e.g., the same RIS element factor may be applied to RIS elements in a sub-surface). Sub-surface level channel estimation may be performed by configuring and transmitting (e.g., one) pilot (e.g., reference signal) per sub-surface (e.g., instead of configuring and transmitting a pilot per RIS element). By introducing sub-surfaces, the dimensionality of the channel estimation problem may be reduced from M+1 to S+1 (e.g., in terms of the number of reference signal resources configured, the number of reference signals sent, and / or the number of CSI calculations performed). For example, the on-off method and / or the on-method described herein may be applied to a sub-surface (e.g., instead of being applied to individual RIS elements) to reduce pilot overhead and / or reduce channel estimation complexity.

[0148] The RIS system described above with reference to Equations 1 to 6 can be used to illustrate sub-surface based RIS operations. j represents the set of RIS element indices in the jth sub-surface, where j=1, ..., S. The union of the sub-surfaces may include multiple (eg, all) of these RIS element indices, for example, ∪j Γ j = {1,…,M}, and the sub-surface sets can be disjoint. Let γ j is an M×1 vector, where j The index in γ is 1 on each row given by γ and zero elsewhere (e.g., the row index may start at 1). γ may be selected corresponding to the jth subsurface j RIS elements in .

[0149] Let G = [γ1 … γ S ] is a sub-surface selection matrix with a dimension of M×S. The above equation 3 (for example, which may represent a RIS system model) may be written as the following equation 7:

[0150] y=(cGΦ s +d)s+z=(c s Φ s +d)s+z (7)

[0151] where Φ s It can represent a complex-valued vector of dimension S×1, including S sub-surface factors factor Applicable to Γ j RIS elements in (e.g., ), and the same RIS element factor Applicable to (eg, each) element in the jth subsurface. c s =cG may represent a 1×S dimensional vector of aggregate channels including S RIS reflections per sub-surface (e.g., c s The jth element of can be equal to ).

[0152] The term (c s Φ s +d) may have the same form as the term (cΦ+d) in Equation 3, except for the length of the vector, which may be S (e.g., representing the number of sub-surfaces) in the former and M (e.g., representing the number of RIS elements) in the latter. (e.g., any) method for channel estimation that may be applicable to each RIS element operation may also be applicable to each sub-surface operation, and vice versa. For example, RIS channel estimation as described herein (e.g., channel estimation for each RIS element) may be (e.g., directly) applicable to channel estimation for each sub-surface by changing the problem dimension (e.g., adding an s superscript). For example, h=[dc s ] can be used to represent the 1×(S+1) vector corresponding to the direct channel and the S channels via the RIS sub-surface, and Θ can be adapted to

[0153]

[0154] in represents the S×1 vector of RIS sub-surface factors during the i-th pilot symbol, and Θ can be a square matrix with dimension (S+1)×(S+1).

[0155] For S sub-surfaces, S+1 pilots (e.g., reference signals or reference signal resources) may be used to estimate the concatenated channels associated with the S sub-surfaces. For example, the WTRU may estimate the concatenated channel according to the following equation 8:

[0156] y=hΘs+z (8) where y=[y0 … y S ] can represent S+1 received pilot symbols, h = [dc s ] may represent a (1×(S+1)) vector having a direct channel and S channels associated with S sub-surfaces, and z=[z0 … z S ] may represent a 1×(S+1) vector associated with noise and / or interference received via the RIS.

[0157] Based on the above equations (where Θ is a full rank matrix that may be known to the WTRU), the WTRU may estimate the channel based on the received pilot y (e.g., as illustrated in Equation 5 or using other suitable techniques). For example, in the on-off method described herein, the RIS sub-surfaces (e.g., all RIS sub-surfaces) may be turned off in a first step (e.g., or ) to obtain the direct link coefficients (e.g., generate received symbols) during the transmission of the first pilot symbol. From the second pilot symbol (i=1, ..., S), (e.g., one) sub-surface may be turned on, while the other sub-surfaces may remain in an off state. Thus, the j-th received pilot as reflected by the j-th sub-surface may be illustrated by Equation 6, where i=1, ..., S.

[0158] In the sub-surface based techniques described herein, if element-by-element channel gain acquisition is performed within (e.g., each) sub-surface, the sub-surface based estimation may be the same as the element-by-element channel estimation (e.g., using M+1 pilot symbols). In the case of a rectangular RIS with uniform sub-surfaces, if the number of sub-surfaces in the horizontal direction is denoted as S x , and the number of sub-surfaces in the vertical direction is denoted as S y , then S can be equal to S x *S y .

[0159] The sub-surface configuration may be scenario-dependent. The WTRU may implicitly or explicitly obtain a suitable phase configuration (e.g., RIS state) for (e.g., each) sub-surface, for example, as part of CSI acquisition. A RIS element may be provided with a specific phase configuration that may achieve a desired performance gain in RIS-assisted communications (e.g., to achieve directional beamforming). The phase configurations between adjacent RIS elements may be correlated (e.g., to some extent) and may not be completely independent or uncorrelated. A positive correlation coefficient between two variables may indicate that the variables may be moving in the same direction and are highly correlated (e.g., compared to a zero or negative correlation coefficient). In an example, it may be assumed that the phase configurations between adjacent RIS sub-surfaces may be correlated. The correlation coefficient p between two adjacent RIS sub-surfaces i and j ij It can be given as in Equation 9 below:

[0160]

[0161] where cov(h i ,h j ) can represent the variable h i With h j The covariance between in represents the expectation operator, and Respectively represent variables (h i ,h j )’s mean and standard deviation.

[0162] The variation in correlation coefficients across different RIS sub-surfaces may be utilized to determine the impact of the operating environment or setting (e.g., user mobility, obstacles, etc.) and / or to select a sub-surface level RIS configuration. For example, when the WTRU is moving in a horizontal plane, the RIS phase configuration between horizontally separated sub-surfaces may be more sensitive to phase variations (e.g., compared to vertically separated sub-surfaces). This may result in a change in p in the horizontal direction. ij 7A ). Based on the change in sub-surface configuration, the WTRU may report sub-surface correlations, which may be used to update the RIS state and / or the sub-surface configuration itself. In the case where multiple WTRUs are assisted by the RIS and each WTRU is served by a different or the same set of sub-surfaces, the sub-surface configuration may be determined based on the respective operating scenarios of the WTRUs. For example, when different WTRUs are at different vertical angles, sub-surfaces as illustrated in FIG. 7A may be considered, while if the WTRUs are moving at the same vertical angle, a configuration based on sub-surfaces distributed according to FIG. 7B may be considered (e.g., to achieve enhanced performance gains).

[0163] Fig. 9 Example procedures associated with scenario-related sub-surface configuration are illustrated. The procedures may involve a base station, a RIS, and / or one or more WTRUs. The RIS may be divided into sub-surfaces (e.g., as configured by a base station). A subset of sub-surfaces or all sub-surfaces may be activated and / or assigned to one or more WTRUs at a given time. The base station may configure the WTRU and / or the RIS. The WTRU may use CSI RS resources provided by the base station to perform CSI acquisition and / or CSI measurements (e.g., for a direct path and / or a RIS-assisted path). The WTRU may perform correlation calculations across sub-surfaces to determine (e.g., obtain) one or more dominant sub-surfaces. The WTRU may report RISC I (e.g., including a RIS-quality indicator (RIS-QI), a correlation coefficient, a phase shift function, etc.) at each sub-surface level (e.g., each sub-surface may include one or more RIS elements). Using current and / or past RIS CSI reports from the WTRU, the base station may identify one or more dominant sub-surfaces. Based on these reports, the base station may determine to update sub-surface level settings at the RIS (e.g., the number and / or location of sub-surfaces allocated to a user, multiplexing transmissions associated with a sub-surface to more WTRUs, etc.). The base station may (e.g., in response to the determination) reconfigure the RIS and / or update one or more of the WTRUs with new or updated RIS configuration information. The base station and / or the RIS may interpolate sub-surface level RIS states into element-by-element RIS states based on RIS phase shifts (e.g., RIS phase shift functions) reported by the WTRUs. For example, these interpolated RIS states may be used by the RIS to provide CSI-RS resources for a CSI acquisition task.

[0164] The RIS may be configured at the element level (e.g., on a per-element basis) or at the sub-surface level (e.g., on a per-sub-surface basis) based on the capabilities of the RIS. Thus, if CSI acquisition is performed at a per-element level for M RIS elements, there may be M+1 pilot transmissions. Fig.10The message exchanges associated with element-by-element RIS operations are illustrated. As shown, the RIS and the WTRU may be configured by a network, such as a base station (BS). The WTRU may perform measurements using available CSI-RS resources. Based on the CSI-RS resources, the WTRU may determine (e.g., obtain) CSI for a direct path (e.g., a path from a base station to the WTRU without reflections from the RIS) and / or a RIS-assisted path (e.g., a path from a base station to the RIS and then to the WTRU). The WTRU may perform measurements and report the element-by-element results (e.g., in a traditional CSI report or an additional RIS CSI report). Based on the reports from the WTRU, the base station may configure the RIS with an updated RIS state. DL and / or UL transmissions may then be performed based on the reports and / or the updated (or original) RIS state.

[0165] If the RIS surface is divided into S sub-surfaces, S+1 CSI-RS resources (e.g., S+1 reference signal transmissions) may be used to perform sub-surface level CSI acquisition. The signaling overhead associated with sub-surface level CSI acquisition may be reduced M / S (e.g., compared to element-by-element CSI acquisition). Fig.11 An example of sub-surface level RIS signaling is illustrated.

[0166] In an example (e.g., in the case of a uniform distribution of elements in each sub-surface), the total number of sub-surfaces may be inversely proportional to the number of elements in each sub-surface. The fewer RIS elements included in the sub-surface, the larger the number of sub-surfaces may be, and vice versa. Increasing the number of sub-surfaces may be expensive because this may increase the overhead for signaling associated with CSI feedback. On the other hand, if a large number of elements are included in the sub-surface, the performance of the communication system may be degraded in some aspects (e.g., compared to the performance that can be achieved using smaller sub-surfaces or element-by-element CSI acquisition). The resolution of the phase that can be achieved at the element level or sub-surface level (e.g., the number of bits representing the phase configuration in the case of a discrete phase shifter) may affect the overall communication performance. Smaller phase resolution may introduce quantization errors and result in performance degradation. On the other hand, since fewer bits are used for each phase configuration, smaller phase resolution may result in less signaling overhead. Therefore, the sub-surface dimension and / or phase resolution may be parameters that can be controlled to improve RIS-assisted communication performance and / or reduce signaling overhead. The WTRU may recommend to the network sub-surfaces of desired size or dimensions and / or phase resolution to achieve target performance (e.g., in terms of SINR, BLER, etc.). For example, if the WTRU is not achieving the target performance, the WTRU may request a change (e.g., increase) in the granularity of the sub-surface (e.g., by reducing the size or number of elements of one or more sub-surfaces), or a change (e.g., increase) in the phase resolution at the RIS element level or at the sub-surface level (e.g., based on a predefined configuration). The achievable phase resolution may not be infinite and may be limited by hardware constraints. If the RIS has been configured with the maximum possible phase resolution, the base station (BS) may increase the granularity of the sub-surface by reducing the size of the sub-surface until an element-by-element RIS configuration is achieved. If element-by-element granularity has been achieved and the WTRU requests further performance improvement, the phase resolution of each RIS element may be increased, for example, until the highest possible phase resolution is achieved.

[0167] CSI-RS can be used for a wide range of purposes, such as beam management, mobility, time-frequency tracking, CSI acquisition, etc. The configuration and transmission of CSI-RS can be performed in a wide range of use cases. Various CSI-RS transmission schemes and corresponding configurations can be applied to RIS CSI determination. One or more CSI-RS can be provided for a RIS sub-surface.

[0168] The RIS element may be in one state (e.g., a single state) at a time. A RIS element factor (e.g., a single RIS element factor) may be used within a specific duration, such as an OFDM symbol. The RIS element factor of a RIS element may change between durations (e.g., between symbols). There may be a transient time associated with a change in the RIS element factor, which may be shorter than the OFDM cyclic prefix. The RIS state of a RIS element at a given time (e.g., the RIS state in an OFDM symbol) may be used for CSI measurement and / or reporting. Pilots (e.g., reference signals) may be time-division multiplexed (e.g., rather than frequency-division multiplexed or code-division multiplexed) such that multiple pilots with different RIS states may be sent or received. This may impose constraints on the operation of the RIS, including CSI determination and / or RIS adjustment.

[0169] The CSI-RS may be used as a pilot for RIS channel estimation and / or CSI acquisition. In an example, M+1 CSI-RS resources may be used to determine the CSI associated with the RIS, where M may be the number of sub-surfaces of the RIS (or RIS elements in some examples). Additional resources (e.g., 1 of the M+1) may be used to estimate a direct path or channel (e.g., between a base station and a WTRU that is not assisted by the RIS). In an example, the M+1 CSI-RS resources may be included in a CSI-RS resource set. In an example, the M+1 CSI-RS resources may be included in multiple CSI-RS resource sets. The CSI-RS resources may be single-port or multi-port resources (e.g., dual-port resources).

[0170] Fig.12 An example of a single-port CSI-RS resource within a resource block (RB) (e.g., of 14 symbol slots) is illustrated. Fig.12 In an example of , the CSI-RS resources may have the same subcarrier offset. In other examples, different CSI-RS resources may have different subcarrier offsets. In addition, different CSI-RS resources may have the same or different frequency density, the same or different bandwidth, the same or different number of antenna ports, the same or different code division multiplexing (CDM) type, etc. The periodicity of the CSI-RS resources may also be the same or different. The time slot offsets of the CSI-RS resources may also be the same or different. Constraints may be imposed so that the CSI-RS resources may not overlap in time on a symbol (e.g., on any symbol).

[0171] The M+1 CSI-RS resources associated with the RIS may be associated with similar (but not identical) transmission times (such as, for example, consecutive symbols, the same time slot, consecutive time slots, etc.) to enable timely and correlated CSI measurement and reporting. M of the M+1 CSI-RS resources may correspond to a channel estimate for each sub-surface (or, in some cases, each RIS element), while the remaining CSI-RS resources may correspond to an estimate of a direct path or channel (e.g., which may be referred to herein as a direct CSI-RS resource). The WTRU may determine which CSI-RS resource in a set of CSI-RS resources may be a direct CSI-RS resource using one or more of the techniques described below.

[0172] In an example, the CSI-RS resources in a CSI-RS resource set may be configured as a list (e.g., a list using CSI-RS resource IDs), and the direct CSI-RS resource may have a specific ordinal position in the list. For example, the directional CSI-RS resource may be the first resource in the list or the last resource in the list. In an example, the CSI-RS resources in a CSI-RS resource set may have different CSI-RS resource IDs, and the direct CSI-RS resource may be a CSI-RS resource with the lowest ID, the highest ID, etc. In an example, the CSI-RS resources in a CSI-RS resource set may be ordered in time (e.g., if these resources appear in the same time slot or multiple consecutive time slots), and the direct CSI-RS resource may be a CSI-RS resource with a specific ordinal position in time. For example, the direct CSI-RS resource may be the first resource in time (e.g., with the lowest time slot offset plus symbol offset), the last resource in time, the middle resource (e.g., with M / 2 resources before it and M / 2 resources after it), etc.

[0173] The CSI-RS resource may be configured such that the WTRU may determine whether the CSI-RS resource is a direct CSI-RS resource if the CSI-RS resource is included in a CSI-RS resource set configured for RIS CSI determination. Constraints may be imposed on the configuration of the CSI-RS resources in the CSI-RS resource set to allow the WTRU to determine whether the CSI-RS resource is a direct CSI-RS resource. For example, the direct CSI-RS resource may be configured with a different (e.g., higher) density, a different (e.g., higher) power offset, and / or a different (e.g., shorter) periodicity than other CSI-RS resources in the CSI-RS resource set.

[0174] In an example, the direct CSI-RS resource may be placed or scheduled near the middle (e.g., in terms of time) of the resource set because the accuracy of CSI estimation may increase as the time difference between the direct CSI-RS resource and the other (e.g., M) CSI-RS resources decreases. Fig.12 In the example, CSI-RS resource 4 may be a direct CSI-RS resource.

[0175] In an example, a direct CSI-RS resource may not be in the same resource set as other (e.g., M) CSI-RS resources (e.g., the other resources may be included in one or more CSI-RS resource sets), but a CSI-RS resource set including the direct CSI-RS resource may be associated with a CSI-RS resource set including the other M CSI-RS resources. In an example, the CSI-RS resource set may be configured in a CSI-RS resource setting (e.g., in an IE named CSI-ResourceConfig) (e.g., by an ID of a CSI-RS resource set that may include M+1 CSI-RS resources). Such a CSI-RS resource setting may include, for example, a list of CSI-RS resource sets for channel measurement. The list of CSI-RS resource sets may include a sequence of CSI-RS resource set IDs of the CSI-RS resource sets, which may be configured separately (e.g., using another IE). In an example, a direct CSI-RS resource may be included in a resource set that has a specific ordinal position in the list of CSI-RS resource sets (e.g., as the first set or the last set in the list). In an example, a direct CSI-RS resource may be included in a CSI-RS resource set having a lowest (or highest) CSI-RS resource set ID. In an example, a CSI-RS resource set may be configured such that a WTRU may determine that a resource set includes a direct CSI-RS resource. For example, configuration information for a CSI-RS resource set may include a parameter that may indicate whether the resource set includes a direct CSI-RS resource. In an example, a CSI-RS resource set including a direct CSI-RS resource may be configured with a specific combination of parameters (e.g., a resource set may include a single CSI-RS resource and have a repetition parameter set to "on").

[0176] In an example, M single-port CSI-RS resources may be used to estimate M RIS secondary channels. In an example, one or more multi-port CSI-RS resources may be used to estimate M RIS secondary channels. In the latter example, a direct path or channel may be estimated based on the ports of the one or more multi-port CSI-RS resources. If the number of sub-surfaces is even, this may result in an odd number (M+1) of antenna ports. For simplicity, some examples provided herein may assume that a direct channel may be estimated based on a separate CSI-RS resource, such as, for example, a single-port CSI-RS resource.

[0177] Fig.13 An example of a single-port CSI-RS resource and an example of an 8-port CSI-RS resource are illustrated.

[0178] Traditional communication systems may not support pure time division multiplexing (TDM) of antenna ports within one multi-port CSI-RS resource. Table 1 below shows example entries (e.g., rows 19-24) that may correspond to various numbers of antenna ports and various TDM modes. Rows 1-18 in the table may be used for traditional systems and are repeated here for comparison.

[0179] Table 1: Example CSI-RS positions within a slot

[0180]

[0181]

[0182] Figure 14(a) to Figure 14(i) An example of TDM antenna ports (APs) for multi-port CSI-RS is illustrated. Figures 14(a), 14(b), and 14(c) show 2 / 4 / 8-port CSI-RS resources with antenna ports in consecutive symbols, which may correspond to rows 19 / 20 / 21 in Table 1, respectively, where k_0=2 and l_0=3. Figures 14(d), 14(e), and 14(f) show 2 / 4 / 8-port CSI-RS resources with a single gap symbol, which may correspond to rows 22 / 23 / 24 in Table 1, where k_0=2 and l_0=3. Figures 14(g), 14(h), and 14(i) show 2 / 4 / 8-port CSI-RS resources with two configurable starting symbols (k_0 and k_1). Figure 14(g) may correspond to row 25 in Table 1, where k_0=2, k_1=8 and l_0=3, Figure 14(h) may correspond to row 26 in Table 1, where k_0=2, k_1=9 and l_0=3, and Figure 14(i) may correspond to row 27 in Table 1, where k_0=2, k_1=12 and l_0=3.

[0183] Gap symbols may allow direct CSI-RS resources to be transmitted in the gap, which may improve overall channel and CSI estimation performance in mobile scenarios. Gap symbols may be used to allow the network to multiplex other transmissions in the gap, such as SSB or emergency PDCCH / PDSCH transmissions.

[0184] A plurality of multi-port CSI-RS resources may be provided for RIS-related CSI determination. For example, two or more (e.g., all) of the M+1 (or in some cases M) CSI-RS resources described herein may be multi-port CSI-RS resources. In an example, the multi-port CSI-RS resources may be similarly configured in terms of frequency domain allocation (e.g., which subcarriers within a PRB may be used for CSI-RS resources), bandwidth, density, number of antenna ports, code division multiplexing (CDM) type, etc. For example, the configuration of the multi-port CSI-RS resources may correspond to the same row in Table 1. In an example, the multi-port CSI-RS resources may be configured differently in one or more of the aforementioned aspects. In an example, multiple ports of a CSI-RS resource may span one or more symbols. For such multi-symbol multi-port CSI-RS resources, the RIS may apply the same RIS state during multiple symbols associated with the CSI-RS resource. For example, if the antenna ports associated with the CSI-RS resource span multiple symbols (e.g., for one or more rows in Table 1 where the cdm type is TD2, TD4, etc.), the RIS may do so. In an example, if different sets of ports perform TDM (e.g., for one or more rows in Table 1 where the cdm type is not TD2 or TD4), different RIS states may be applied during different symbols of the multi-symbol, multi-port CSI-RS resource.

[0185] A plurality of CSI-RS resources (eg, N T The antenna ports can be connected to the same RIS state Φ i (or in the case of sub-surfaces ). Such CSI-RS resources may have a configuration according to row 3 of Table 1 (e.g., 2 antenna ports multiplexed in the same symbol), such as Fig.15 This may mean that the WTRU may estimate N for each RIS state and / or each pair of adjacent subcarriers carrying CSI-RS resources. T (eg, 2) different sets of channels.

[0186] M+1 (or S+1 in case of sub-surface) TDM CSI-RS resources may be used to estimate M+1 (or S+1 in case of sub-surface) channels per CSI-RS antenna port. The WTRU may estimate the M+1 (or S+1) N TEach resource in the port CSI-RS resource takes the kth antenna port (k∈{0 … (N T -1)}) and perform channel estimation as described herein (eg, according to Equation 5).

[0187] The following explanation may be provided in the context of a RIS element level model or operation, but may also be applicable to a sub-surface level model or operation. If the TRP precoding P is not included in the TRP to RIS path or channel, then the above equation 3 may be written as the following equation 10:

[0188] Y=((a⊙b)Φ+d)s+z=(((AP) T ⊙b)Φ+d′P)s+z=(((A⊙b T )P) T Φ+d′P)s+z (10)

[0189] Where a = (AP) T It can be a complex-valued vector channel of dimension 1×M between TRP and RIS, and M can be the number of RIS elements including TRP pre-decoding P. Can be a complex value M×N between TRP and RIS T The channel matrix (e.g., excluding TRP precoding). The mth row and kth column in the matrix can be represented as a′, respectively. m and a″ k , where a′ m The meaning may be as described in this article. It can be along the TRP-RIS-WTRU path with dimensions of M×N T The cascaded RIS auxiliary channel matrix, excluding the RIS element factor, where b m The meaning of may be as described herein. As shown in the equation, P may be a complex value N T ×1 pre-coding vector. In an example, P may correspond to N L The complex value N of the layer T ×N L Pre-coding matrix. In those examples, s can be N L ×1 symbol vector (eg, rather than a scalar). To simplify the description, the examples provided herein may be described as having a pre-coding vector P.

[0190] The M+1 pilot symbols received on the kth CSI-RS antenna port may satisfy the following Equation 11 (e.g., following Equation 4 above). CSI-RS antenna ports on adjacent subcarriers or within an RB may be considered, which may allow an assumption or rough estimate that the radio channels across REs carrying different CSI-RS antenna ports may be the same.

[0191]

[0192] where y k =[y k,0 … y k,M ] may be the M+1 received pilot symbols on CSI-RS antenna port k, h k =[d k c k ]=[(d′P k )((A k P k ) T b)] may be a 1×(M+1) vector with a direct channel and M RIS auxiliary channels on CSI-RS antenna port k, and d′ may be a 1×N vector from TRP to WTRU T Direct channel. k It can be N applied to CSI-RS antenna port k T Pre-decoding vector. For example, for span N T The antenna selection pre-decoder can be applied to different CSI-RS antenna ports, where the kth element is 1 and the remaining elements are 0 (e.g., P0 = [10 ... 0] T , P1=[0 1 0 … 0] T When used in this article, the TRP antenna can be interpreted broadly. For example, the antenna can correspond to a set of antenna elements connected to the transceiver chain through a set of splitters and phase shifters. The same pre-decoder P k Applicable to antenna ports of M+1 different CSI-RS resources. It can be a square matrix of dimension (M+1)×(M+1) containing the RIS element factors. The same matrix Θ can be applied to multiple (e.g., all) antenna ports. k =[z k,0 … z k,M ] can be a vector of dimension 1×(M+1) that can be associated with the noise and interference received on the kth CSI-RS antenna port.

[0193] To simplify notation, s may be used to denote a symbol on CSI-RS antenna port k. The pilot symbol s may be different on different antenna ports for different pilots in time (e.g., as long as the symbol is known to the WTRU, e.g., via a known sequence of pilot or reference symbols). In these cases, the notation s may be used instead. k 、s m,k or j,k .

[0194] Using the antenna selection predecoder described in this article, Equation 11 can be simplified to the following Equation 12:

[0195]

[0196] where d′ k may represent the direct scalar channel or path from the kth TRP antenna to the WTRU, and a′ k ' may be a 1×M vector associated with the channel between the kth TRP antenna and the M RIS elements.

[0197] To simplify the description, the index k may represent a CSI-RS antenna port and a TRP antenna (eg, due to the antenna selection predecoder described herein). Other mappings between one or more TRP antennas and CSI-RS antenna ports may be performed using the predecoder P. k For example, the WTRU may estimate the channel from the TRP to the WTRU (e.g., including direct channels and / or RIS auxiliary channels) for each CSI-RS antenna port, which may correspond to The estimation of each TPR antenna of T In the example, the following can be true: And the WTRU can use A⊙b T and d′ to jointly optimize P and Φ in Equation 10. For example, the WTRU may select P and Φ such that |((A⊙b T )P) T Φ+d′P| may be maximized (eg, this may maximize received power or SNR). Precoding P may affect the gain of the direct path (eg, |d′P|) and / or the gain of the RIS auxiliary path (eg, |(A⊙b T )P) T Φ|). The RIS state Φ may (eg, only) affect the gain of the RIS auxiliary path.

[0198] In an example, the WTRU may report a recommended precoder (e.g., P) and / or a recommended RIS state (e.g., Φ) in a CSI report. The recommended precoder may be parameterized using various methods including various types of traditional PMI reporting methods (e.g., Type I and Type II codebooks, wideband PMI and sub-band PMI, etc.). The recommended RIS state may be parameterized using a set of parameters as discussed herein. to parameterize.

[0199] The pre-decoder and RIS state optimization and reporting described herein may be applicable to sub-surface based RIS operations. For example, for sub-surface based RIS operations, the pre-decoder and RIS state optimization and reporting may be applicable to sub-surface based RIS operations by using dimension S instead of M, and / or by using a marker for sub-surface based operations such as Φ s and ) to accommodate the description provided above.

[0200] RIS CSI-RS bursts may be provided. This may be because when the number of RIS elements M is large, the reference signal transmission in one time slot may not be sufficient. In these cases, RS transmission may be performed over multiple time slots, where the multiple time slots may or may not be consecutive. Conventional communication systems may support up to 8 CSI-RS resources in a CSI-RS resource set. This constraint may be used to limit the WTRU CSI calculation complexity and / or the number of bits used for CRI in a CSI report. For RIS CSI, the CSI complexity per CSI-RS resource may be lower for the WTRU (e.g., compared to other types of CSI reports), and / or the RIS CSI report may not include CRI. Therefore, extended CSI-RS resource sets (e.g., with more than 8 CSI-RS resources) may be supported for estimating M sub-surface-based channels with M CSI-RS resources. The CSI-RS resources may be TDMed, and / or the CSI-RS resources in a resource set may span multiple time slots. The CSI-RS resources may be single-port or multi-port resources, even though these CSI-RS resources may be illustrated as single-port CSI-RS resources in some of the figures provided herein.

[0201] A CSI-RS resource (e.g., M CSI-RS resources associated with RIS CSI determination) may be split into multiple (e.g., Z) CSI-RS resource sets. The Z resource sets may be included or indicated in a CSI-RS resource setting or configuration. A CSI-RS resource set including direct CSI-RS resources may be included in a CSI-RS resource setting or configuration.

[0202] In a conventional communication system, a CSI report may be generated and / or sent based on a channel measurement performed using resources (e.g., CSI-RS or SSB) included in a CSI-RS resource set (e.g., such as a single CSI-RS resource set). For example, a CSI resource setting may include a single CSI-RS resource set for periodic and semi-persistent CSI reporting. As an enhancement, a CSI report may be generated based on resources included in multiple CSI-RS resource sets. For example, a CSI resource setting may be configured with multiple CSI-RS resource sets for periodic and / or semi-persistent CSI reporting.

[0203] In an example, CSI-RS resources in a CSI-RS resource set may be transmitted in the same time slot, and CSI-RS resources in different resource sets of the same CSI resource setting may be transmitted in different time slots. In an example, CSI-RS resources in different CSI-RS resource sets of the same CSI-RS resource setting may be transmitted in the same time slot. Fig.16 An example is illustrated where two CSI-RS resource sets are in the same time slot and a third CSI-RS resource set is in a subsequent time slot. In the example, CSI-RS resource set 0 may include direct CSI-RS resources, while the other two resource sets (sets 1 and 2) may include M CSI-RS resources associated with RIS (e.g., M=16).

[0204] In an example, CSI-RS resources in different CSI-RS resource sets of the same CSI resource setting may be transmitted in the same time slot or in different time slots. Fig.17 An example is shown in which some CSI-RS resources in CSI-RS resource set 2 are transmitted in the same time slot as CSI-RS resources in another resource set of the same CSI resource setting, while other CSI-RS resources in CSI-RS resource set 2 may be transmitted in different time slots.

[0205] In an example, a multi-port CSI-RS resource may be used for sub-surface based channel estimation. The number of pilots (e.g., M) may be higher than the number (e.g., maximum number) of TDM CSI-RS antenna ports (e.g., the maximum number of TDM antenna ports in the example of Table 1 may be 8). For values ​​of M greater than 8 (e.g., M=16), multiple pilots may be obtained across multiple multi-port CSI-RS resources. For example, two 8-port CSI-RS resources may provide sufficient pilots for M=16, as shown in FIG. Fig.18 and Fig.19 As illustrated in FIG. . As discussed herein, the multiple CSI-RS resource sets, the multi-port CSI-RS resources may be in the same time slot or in different time slots, such as Fig.18 As shown. Multi-port CSI-RS resources can cross time slot boundaries, such as Fig.19 shown.

[0206] Multiple CSI-RS resource sets may be separated in the frequency domain. CSI-RS resource sets may be sent simultaneously and / or dedicated to different tasks. For example, as shown in FIG. 20( a), one CSI-RS resource set may be used for channel measurement while another CSI-RS resource set may be used for interference measurement. The CSI resource sets may include M+1 resources, which may be TDMed as discussed herein. The configured CSI-RS resource settings may be used in multi-user scenarios (e.g., multiple users may use the same RIS), where different users may be scheduled with different CSI-RS resource sets, and the resources (e.g., M+1 resources) for a user (e.g., a WTRU) may be FDMed or TDMed. FIG. 20( b) illustrates an example of dual-user CSI-RS transmission for an M-element or M-subsurface RIS.

[0207] The sub-surface of RIS may be mapped to CSI-RS resources and / or antenna ports. In the examples provided herein, the WTRU may obtain knowledge about the matrix θ described herein, for example, via specification information and / or configuration information received from the network. The columns of θ may correspond to M+1 pilots, where (e.g., one) pilot may correspond to a direct channel or path, and the M other pilots may correspond to RIS auxiliary channels. The WTRU may be configured with a mapping between the columns of θ and the CSI-RS resources and / or antenna ports. The WTRU may use the mapping to estimate the channel and / or generate a RIS CSI report. A direct channel or path may be estimated using a direct CSI-RS resource, which may be identified according to various methods described herein. The other M columns of θ may correspond to different CSI-RS resources and / or antenna ports, which may be TDMed. The M columns of θ may be mapped to CSI-RS resources and / or antenna ports that may be continuous in time. For example, the leftmost column in θ that does not correspond to a direct channel (e.g., having the smallest column index) may be mapped to a CSI-RS resource or antenna port that is not configured as a direct CSI-RS resource. The column may also be mapped to a CSI-RS resource or antenna port that may have the smallest time slot, the smallest symbol offset, etc.

[0208] The WTRU may use the mapping order to collect received symbols that may be associated with the vector y described herein. Note that the vector y may include symbols received from multiple CSI-RS resources, symbols received from different antenna ports of a multi-port CSI-RS resource, or symbols received from antenna ports of different multi-port CSI-RS resources.

[0209] The mapping as described herein may be created based on RIS elements or sub-surfaces. For example, according to Equation 4, the first row of the matrix Θ may correspond to the direct path, while the other rows of Θ may correspond to the RIS auxiliary paths. This may mean that h and The first element in θ may correspond to a direct path. In other examples, any row of θ may correspond to a direct path, while the remaining rows may correspond to RIS auxiliary paths.

[0210] The rows in Θ that may not correspond to direct paths may correspond to RIS elements. The mapping between RIS elements and rows of Θ may be defined (e.g., configured) to enable the WTRU to calculate RIS parameters, which may be based on horizontally or vertically adjacent RIS elements, corner and / or edge RIS elements, etc. The mapping between RIS elements and rows of Θ may be reflected in the mapping to h and The elements of the map.

[0211] In an example, the first row in θ that does not correspond to a direct path (e.g., the second row of θ in Equation 4) may correspond to RIS elements in a RIS corner. Such a row may correspond to a RIS element in the lower left corner. From this corner, adjacent RIS elements in the horizontal or vertical direction may be mapped to subsequent rows of θ in sequence. If RIS elements are first mapped to θ in the horizontal direction, then these elements may be mapped in the vertical direction, and vice versa.

[0212] FIG. 21( a ) illustrates a mapping order of RIS elements in which the horizontal direction may be mapped first. FIG. 21( b ) illustrates a mapping order of RIS elements in which the vertical direction may be mapped first. The numbers associated with the RIS elements may correspond to the row index for the RIS elements in Θ, or to the row index of h and The index of the element in .

[0213] In the case of subsurface-based operations (e.g., according to Equation 8), the subsurfaces are related to the rows in Θ and h and Similar mappings between elements in θ may be known to the WTRU. A corner sub-surface, such as the lower left corner, may be mapped to the first row in θ that does not correspond to a direct path. A horizontal first mapping or a vertical first mapping similar to that shown in FIG. 21( a) or FIG. 21( b) may be used for the sub-surface. The mapping order (e.g., horizontal or vertical first) may be specified or configurable (e.g., by the network).

[0214] In an example, the WTRU may not know whether the first mapping direction is horizontal or vertical. The directions may be referred to as a first direction and a second direction, either of which may be horizontal, vertical, or in another direction. Based on the mapping order, the WTRU may know whether two RIS elements or sub-surfaces may be adjacent in the first direction or the second direction, whether a RIS element or sub-surface may be along an edge of the first direction or the second direction, etc. The RIS parameter report may relate to the first direction and / or the second direction.

[0215] The WTRU may know the relationship between CSI-RS resources and and / or the relationship between neighboring elements and / or sub-surfaces in the first direction and / or the second direction. The WTRU may report RIS parameters based on the first direction and / or the second direction.

[0216] One or more RIS parameters may be defined and / or configured (e.g., for a WTRU). The WTRU may calculate (e.g., determine) the CSI to report when estimating various channels and / or parameters associated with the CSI. The channel may be given by h=[dc s ], or in the case of RIS element-based channel estimation, by h = [dc]. Other parameters associated with CSI calculation may include noise and / or interference related parameters, which may be related to transmit power, WTRU receiver processing parameters (such as beamforming or spatial filtering associated with the receiver), etc. To simplify the description, some examples may be described in the context of defining RIS states at the RIS element level (e.g., Φ with length M, etc.), but these examples may also be applicable to defining RIS states at the sub-surface level (e.g., Φ with length S). s etc.) to define the RIS status.

[0217] The RIS CSI may be used by the network to adjust or optimize the RIS state for transmission to and / or reception from the WTRU. For example, the network may select the RIS element factor Φ = [φ1 … φ M ] T , so that ∠(c1φ1)=…=∠(c M φ M )=∠d, where ∠d may represent the angle of the complex number d. If (e.g., each) signal component reflected by a RIS element is received in phase with the direct path d, the received signal quality may be enhanced. In an example, the WTRU may determine (e.g., calculate) the appropriate RIS state Φ=[φ1 … φ M ] T And report the information to the network. This operation can be considered as the WTRU recommending the RIS state.

[0218] The WTRU may calculate Φ based on Φ=[φ1 … φ M ] T To calculate the RIS parameter set The WTRU may report or recommend As a representation of Φ. The network can be configured to include Parameters in RIS parameterized models or functions, parameter resolution, etc. The number of bits used to represent Φ can be lower than the number of bits used to represent Φ. The RIS status (expressed as ) may be an approximation or quantization of Φ. The WTRU may select Make (e.g., the vector norm of the error) may be minimized. The WTRU may select So that Φ can be the RIS state corresponding to the effective In each case, the WTRU can choose and the corresponding

[0219] The WTRU may report the estimated direct channel (d) or the estimated angle of the direct channel (∠d). In an example, Φ may be adapted to d and may not be reported. In an example, the RIS parameters may be based on the angle and / or phase of Φ. m The magnitude of may vary with m (e.g., for semi-active or active RIS). To simplify the description, examples of RIS parameter correlation may be described herein in terms of angle and / or phase, but the techniques disclosed herein may also be applicable to φ m The amplitude and / or φ m The complex part of m May include plural).

[0220] RIS element factors may be provided for each sub-surface of the RIS. Given an estimate of h, the WTRU may calculate an appropriate Φ and report it to the network (e.g., directly and / or in some quantization). For example, φ m The angle and / or phase of may be quantized (eg, using a W-ary PSK constellation and / or coding), where each ∠φ m It can be quantized into log2(W) bits, and the total number of bits can add up to M*log2(W) (e.g., in the case of RIS element-level reporting) or S*log2(W) (e.g., in the case of sub-surface-level reporting).

[0221] The various phase shifts (e.g., angles) in Φ may be related. For example, the phase shifts in two adjacent RIS elements may be related. This may mean that more CSI reporting may be possible with less overhead without sacrificing performance. The WTRU may calculate Φ=[φ1 … φ M ] T To calculate the RIS parameter set And can report Instead of Φ. CSI reports may include If Represented by fewer bits than Φ, the feedback overhead can be reduced. Examples of parameterization are discussed below.

[0222] The CSI feedback or report may include an indication of a phase shift function that the WTRU may have selected (e.g., at least if the WTRU has been configured with multiple phase shift functions to choose from). In some cases (e.g., where the WTRU is in the far field), a linear or planar function may be appropriate, while in other cases (e.g., where the WTRU is in the near field), a quadratic function may satisfy the desired phase shift.

[0223] The phase shift of RIS elements across the RIS may be linear or approximately (e.g., substantially) linear. The phase shift may be linear in a particular direction across the RIS. For example, the phase shift may be linear along the horizontal direction of the RIS and / or the vertical direction of the RIS, and the parameters associated with different lines may be different. The linear phase shift along both directions may be considered as a planar phase shift. Let x denote a first direction and y denote a second direction (e.g., they may correspond to the horizontal and vertical directions, respectively). Phase shift lines along the x-axis and / or the y-axis may be estimated, and parameters for either or both lines may be reported in the RIS CSI report. For example, the following may be true: Wherein the exemplary equations in the x-axis and y-axis may be given by the following equation 13:

[0224]

[0225] In the case of RIS element-based channel estimation, m x ∈{0,…,M x -1}, or in the case of subsurface based channel estimation, m x ∈{0,…,S x -1}. m x Can be a RIS element or a subsurface index along the x-axis. y Can be a RIS element or subsurface index along the y-axis. x ,m y ) can be

[0226] In some examples, report β=β x +β y may be sufficient, since this parameter describes the phase shift in the reference element or subsurface, where m x =m y =0 (for example, ). This can be used as a representation of the plane according to Equation 14 below:

[0227]

[0228] The parameters in can be quantized. x and / or α y can be reported and may include errors. x and m y value, the error can be ignored. x and / or m y value, the error (e.g., the total number of errors) may be significant. x and / or α y An example method to quantize the error introduced by may be to adjust the RIS elements or sub-surface indices so that b may represent a phase shift in the middle (or near the middle) of the surface. For example, the following may be enforced for the x-direction: And similarly for the y direction and / or sub-surfaces. As another example, it is possible to enforce

[0229] There may be an even number of elements or sub-surfaces in one or two directions (e.g., the x-direction and / or the y-direction). The indices of these elements or sub-surfaces may be shifted so that β may represent the phase shift between the middle two elements or the average value between the middle two elements (e.g., in the middle of the RIS). For example, and In the case of , the example plane equation can be as follows:

[0230]

[0231] For the x direction, the effective index (m x +1 / 2) can be provided as And similarly for the y direction and / or sub-surface.This may provide a symmetry plane around the RIS center and / or around the phase shift value β.

[0232] The linear or planar phase shift across the RIS may not be sufficient to represent a suitable phase shift Φ to be calculated by the WTRU. A quadratic component may be added to the linear or planar equations described herein. Equation 16 below shows such an example, where

[0233]

[0234] For example, in the linear or planar case, β x and β y Can be combined into β = β x +β y , so that As illustrated in Equation 17 below:

[0235]

[0236] As discussed herein, quantification problems and / or indexing solutions (e.g., including using methods such as m x +1 / 2) may be applicable to examples with quadratic phase shifts. Points in Equation 17 (e.g., extreme points such as minimum or maximum) may occur at and At, or for the quadratic component appears at m x =m y = 0. In order to fit the function to Φ calculated by the WTRU, variable points (e.g., variable extreme points) may be introduced, as illustrated in Equation 18 below:

[0237]

[0238] Parameter δ x and δ y can be used to shift one or more points of a function in the RIS (e.g., the extreme points described herein) to obtain an example RIS parameter set

[0239] The element index of the RIS may be reported. As discussed herein, the reported function parameters (such as, for example, α x ,α y ,γ x ,γ y ) can be increased with the RIS element or subsurface index m x and m y For example, in m x The maximum value of is 1000, in the case of the maximum m x At the RIS element of the value, α x The quantization error in can be magnified 1000 times. x The quantization error in times.

[0240] A way to overcome this problem may be to avoid quantizing and / or reporting gradient parameters. The WTRU may report multiple RIS elements or sub-surface indices to indicate the rate of phase change across the RIS (e.g., linear, quadratic, etc.). In the linear example, the RIS element or sub-surface may be a first reference element, such as a corner RIS element or sub-surface (e.g., m x =m y = 0). The WTRU may have calculated a specific phase φ of the reference element ref =φ 0,0The WTRU may determine a second element or sub-surface in a direction (e.g., in the x-direction). and in the y direction ), for the second element or subsurface, the phase offset (e.g., Δφ) relative to the reference element x and Δφ y ) may (eg, at least approximately) have a particular value, as illustrated below in Equation 19. The second element or sub-surface may be an element different from the first reference element or sub-surface.

[0241]

[0242] CSI reports may include RIS parameter sets Δφ x and / or Δφ y The resolution of Δφ may be lower (eg, the phase shift may correspond to 4-PSK or 8-PSK). The sign of the phase shift may be included. x and Δφ y The resolution or phase shift set may be configurable (eg, Δφ x and Δφ y The set of phase offset values ​​may include values ​​greater than or equal to 2π. This may indicate that the phase may have shifted one full turn or more between the reference element and the second element. For example, the WTRU may select Δφ x and Make can be minimized (a similar operation can be performed for the y direction). The WTRU may choose Δφ x and Make can be minimized (a similar operation can be performed for the y direction). The latter metric can correspond to minimization of the gradient error. Phase wraparound can be included or excluded in the phase calculations described herein.

[0243] The number of phase wraps from the reference element to the second element may be included in the RIS parameter set (e.g., in the x-direction and / or the y-direction). In a numerical example, the WTRU may estimate the channel, as discussed herein, and may determine a suitable RIS state Φ, which may include a suitable RIS element state for one or more (e.g., each) of the 16,384 RIS elements. x =m y = 0 may have a total element index m = 0, where the phase shift is φ 0,0 =φ0. Let Δφ x The phase shift set is The WTRU may determine 83 can have phase shift For the y direction, the WTRU may determine Can have phase shift The WTRU may include the following parameters in the CSI report: For φ 0,0 The number of bits used to represent the phase shift of the reference element, for example, 8 bits are used to represent the phase shift according to the 256-PSK constellation. and The number of bits of can be log2(128)=7 bits. x and Δφ y The number of bits for each can be log2(8)=3 bits. This can add up to 8+7+7+3+3=28 bits to represent a linear or planar phase shift across a 16,384-element RIS.

[0244] The second element (for example, and ) may correspond to a point (e.g., an extreme point) in the phase shift function (e.g., a minimum or maximum value). The phase shift at that point may be reported (e.g., ). The amount of phase wrapping between the reference element and the second element may be reported. These operations may be combined with an assumption of a quadratic phase shift function. The gradient of the function on the x-axis and / or y-axis at the reference element may be reported. The gradient of the function at the reference element in the direction of the second element may be reported. The gradient of the function at the second element may be zero (e.g., because it may be an extreme point).

[0245] Phase shifts can be reported for RIS corner elements or subsurfaces. For example, The RIS parameters can include the phases in the x direction (W x ) and / or in the y direction (W y ) is the amount of phase wrap-around between the corners on the

[0246] The maximum number of RIS phase shifts may depend on the resolution of the RIS element (eg, each RIS element). For a particular resolution of b bits, the total number of possible RIS phase shifts (2 b ) can be considered to form a codebook. (Each) discrete phase value can be obtained uniformly or non-uniformly from a phase shift range [(-π)-π], which can be one period or one cycle of the signal.

[0247] The WTRU may be configured with a codebook which may be a set of C possible RIS states For example, The codebook (or its construction) may be provided or configured in whole or in part. The length of can match Φ or Φ for element-wise or subsurface-wise operations, respectively. s The length of Φ or Φ can be estimated based on one or more multi-port CSI-RS s In the case of , the length may correspond to the number of antenna ports in a multi-port CSI-RS resource, or to the total number of antenna ports across multiple multi-port CSI-RS resources. s As an example, the selected (e.g., bits)RIS status index The RIS CSI parameter set that can be included in the report middle.

[0248] In an example, the WTRU may not estimate or calculate Φ s The WTRU may obtain Direct selection For example, the WTRU may select a RIS state that maximizes the SNR, e.g. In an example, the WTRU may estimate or calculate Φ s and from Select For example, with Φ s The smallest distance For example,

[0249] If RIS is present in a communication network, the performance of the communication network may depend on different RIS parameters. These parameters may include the size of the RIS, the RIS operating configuration (e.g., per element or per sub-surface or entire surface), the resolution of the phase shifter in the case of discrete phase RIS state (b bits), supported RIS modulation, etc. For example, if a larger number of RIS elements are utilized to serve a given user, a higher beamforming gain may be achieved. A lower resolution of (e.g., per) RIS element may introduce higher quantization error (e.g., compared to a higher bit resolution), thereby affecting performance. A metric such as a RIS quality indicator or RIS-QI may be used to capture the impact of RIS parameters on communication performance. The RIS-QI may be reported by the WTRU and used by a base station (e.g., gNB) and / or a RIS controller to update or improve the RIS state. Based on an estimated channel between the RIS and the WTRU (e.g., a channel assisted by the RIS), the WTRU may perform measurements on a RIS assisted link or path. The RIS-QI may be measured based on a target SINR. A mapping of SINR to RIS-QI may be created.

[0250] The interpolation may be performed based on the RIS parameters. The network may receive one or more RIS CSI reports from the WTRU, including the RIS CSI reports discussed herein. The network (e.g., BS, gNB, or RIS controller) can Reconstruct or estimate the recommended RIS status If the channel estimate and / or RIS status is recommended is for each RIS element, then Can be used, for example, directly by the base station to configure, activate and / or refer it to a RIS. If the recommended RIS status is for each sub-surface, the network can execute the RIS state from each sub-surface To each RIS element RIS status The interpolation and / or extrapolation may occur in a network node such as a base station or gNB or at the RIS. Such a process may be illustrated by the following equation 20:

[0251]

[0252] in It can be the recommended RIS state for each sub-surface (e.g., dimension S×1), such as based on the RIS CSI feedback parameter Reconstructed (eg, as a function thereof). g(·) may be an interpolation or extrapolation function that can map the RIS state of each sub-surface (eg, of dimension S×1) to the RIS state of each RIS element (eg, of dimension M×1). It can be a per-RIS element RIS state (e.g., of dimension M×1) that can be in each sub-surface RIS state recommended for the WTRU. Obtained after interpolation or extrapolation.

[0253] Subsurface RIS status can be assigned to RIS elements within a subsurface (e.g., for m∈Γ j , ), where the RIS element may be located at or near the center of the sub-surface. The spacing in the x-direction and y-direction between such RIS elements in different sub-surfaces to which the sub-surface RIS state may be assigned may be equal to the number of RIS elements per sub-surface in the x-direction and the y-direction (e.g., M in the x-direction and M in the y-direction, respectively). x / S x and M y / S y). If there is an even number of RIS elements per sub-surface, there may not be a single center element in the sub-surface in the x-direction and / or the y-direction. In this case, the RIS element indexes may be adjusted, for example, using indexes as discussed herein. For example, the two RIS elements at the center of the sub-surface may be given an index or position m' x +1 / 2 and m' x -1 / 2(or m' x +1 and m' x -1), where index or position m' x may correspond to the sub-surface center in the x-direction (and similarly in the y-direction), which may be assigned a sub-surface RIS state

[0254] Based on having A collection of RIS element indices or positions of assigned RIS states, which may be interpolated and / or extrapolated to generate The remaining RIS states in . Various forms of interpolation and / or extrapolation techniques may be applied, such as linear, quadratic, etc. For various examples with reported function parameters (such as, for example, linear / planar, quadratic, etc.), each subsurface parameter may be scaled to fit the RIS element-level interpolation or extrapolation. For example, the reported linear gradient α x (for a subsurface) can be scaled to (For example, the gradient may be reduced by the number of RIS elements per subsurface in the x-direction.) The reported quadratic parameter γ x (e.g., for a subsurface) can be scaled to (For example, the quadratic parameter may be reduced by the squared number of RIS elements per sub-surface squared in the x-direction.) Similar scaling may be applied in the y-direction.

[0255] In an example, a WTRU may be configured with CSI reporting parameters associated with a RIS (e.g., which may also be referred to herein as CSI measurement parameters). The CSI reporting parameters may include, for example, CSI-RS resources to be measured, channel and / or interference related parameters (e.g., CQI, RI, PMI, CRI, RIS-QI, etc.), and / or other RIS-related configuration information (e.g., parameters), such as the number of sub-surfaces or elements in the x-direction and / or y-direction of the RIS. The WTRU may receive (e.g., be scheduled with) CSI-RS resources, calculate RIS parameters (e.g., RIS CSI-related parameters such as CQI, RI, RIS-QI, etc.), and / or report the RIS parameters in a CSI report.

[0256] In an example, the RIS may report the capabilities of the RIS to a network such as a base station. The RIS is provided with sub-surface (or RIS element) related configuration information and / or time domain configuration information. For example, the RIS may apply the sub-surface (or RIS element) configuration information during a time instance determined based on configuration signaling, an activation command, an explicit or implicit indication, a triggering event, etc. The RIS may receive a RIS element level RIS state (e.g., from a network or a WTRU). For example, the RIS may apply the RIS element level RIS state during a time instance determined based on configuration signaling, an activation command, an explicit or implicit indication, a triggering event, etc.

[0257] Although the above features and elements are described in specific combinations, each feature or element may be used alone without the other features and elements of the preferred embodiment, or in various combinations with or without the other features and elements. Although the specific implementations described herein may consider 3GPP specific protocols, it should be understood that the specific implementations described herein are not limited to such scenarios and are applicable to other wireless systems. For example, although the solutions described herein may consider LTE, LTE-A, New Radio (NR) or 5G specific protocols, it should be understood that the solutions described herein are not limited to such scenarios and are also applicable to other wireless systems.

[0258] The processes described above may be implemented in a computer program, software, and / or firmware incorporated in a computer-readable medium for execution by a computer and / or processor. Examples of computer-readable media include, but are not limited to, electronic signals (sent via wired and / or wireless connections) and / or computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media (such as, but not limited to, built-in hard disks and removable disks), magneto-optical media, and / or optical media (such as compact disk (CD)-ROM disks and / or digital versatile disks (DVDs)). A processor associated with the software may be used to implement a radio frequency transceiver for a WTRU, terminal, base station, RNC, and / or any host computer.

Claims

1. A wireless transmit / receive unit (WTRU), the wireless transmit / receive unit (WTRU) comprising: A processor, the processor being configured to: receiving measurement configuration information from a network device, the measurement configuration information indicating at least a first measurement resource and a second measurement resource, wherein the first measurement resource is associated with a first transmission path, the first transmission path is associated with a first subset of elements of a reconfigurable smart surface (RIS), and wherein the second measurement resource is associated with a second transmission path independent of the RIS; performing a first measurement using the first measurement resource indicated by the measurement configuration information, wherein the first measurement is performed based on a first reference signal received via the first transmission path; performing a second measurement using the second measurement resource indicated by the measurement configuration information, wherein the second measurement is performed based on a second reference signal received via the second transmission path; as well as A report including information about at least one of the first measurement or the second measurement is sent to the network device.

2. The WTRU of claim 1 , wherein at least one of the first reference signal or the second reference signal comprises a channel state information (CSI) reference signal, and wherein the report sent to the network device comprises a CSI report.

3. The WTRU of claim 2, wherein the measurement configuration information further indicates corresponding channel quality parameters to be measured using the first measurement resource and the second measurement resource.

4. The WTRU of claim 1 , wherein the first reference signal and the second reference signal are received from a same multiple-input multiple-output transmitter associated with the network device.

5. The WTRU of claim 1 , wherein the measurement configuration information further indicates a third measurement resource associated with a third transmission path, the third transmission path being assisted by a second subset of elements of the RIS, and wherein the processor is further configured to perform a third measurement based on a third reference signal received via the third transmission path.

6. The WTRU of claim 5, wherein the processor is configured to receive all or a subset of the first reference signal, the second reference signal, and the third reference signal via time division multiplexing.

7. The WTRU of claim 5, wherein the processor is configured to receive the first reference signal, the second reference signal, and the third reference signal during a reference signal transmission burst comprising a plurality of time slots.

8. The WTRU of claim 1, wherein the measurement configuration information further indicates that the first measurement resource and the second measurement resource belong to different measurement resource sets.

9. The WTRU of claim 1 , wherein the processor is configured to send the report regarding at least one of the first measurement or the second measurement to the network device comprises: The processor is configured to send a first report indicating results of the first measurement using a first uplink grant and to send a second report indicating results of the second measurement using a second uplink grant.

10. The WTRU of claim 1, wherein the measurement configuration information indicates that the first measurement resource and the second measurement resource are associated with corresponding resource indexes, transmission times, transmission periodicities, or transmission power offsets, and wherein the processor is configured to determine that the first measurement resource is associated with the first transmission path and the second measurement resource is associated with the second transmission path independent of the RIS based on the corresponding resource indexes, transmission times, transmission periodicities, or transmission power offsets associated with the first measurement resource and the second measurement resource, and the first transmission path is associated with a first subset of elements of the RIS.

11. A method implemented by a wireless transmit / receive unit (WTRU), the method comprising: receiving measurement configuration information from a network device, the measurement configuration information indicating at least a first measurement resource and a second measurement resource, wherein the first measurement resource is associated with a first transmission path, the first transmission path is associated with a first subset of elements of a reconfigurable smart surface (RIS), and wherein the second measurement resource is associated with a second transmission path independent of the RIS; performing a first measurement using the first measurement resource indicated by the measurement configuration information, wherein the first measurement is performed based on a first reference signal received via the first transmission path; performing a second measurement using the second measurement resource indicated by the measurement configuration information, wherein the second measurement is performed based on a second reference signal received via the second transmission path; as well as A report including information about at least one of the first measurement or the second measurement is sent to the network device.

12. The method of claim 11, wherein the first reference signal and the second reference signal are received from a same multiple-input multiple-output transmitter associated with the network device.

13. The method of claim 11, wherein the measurement configuration information further indicates a third measurement resource associated with a third transmission path, the third transmission path being associated with a second subset of elements of the RIS, and wherein the method further comprises: A third measurement is performed based on a third reference signal received via the third transmission path.

14. The method of claim 13, wherein all or a subset of the first, second and third reference signals are received via time division multiplexing during a reference signal transmission burst comprising a plurality of time slots.

15. A network device, comprising: A processor, the processor being configured to: receiving information about a reconfigurable intelligent surface (RIS); transmitting a measurement configuration to a wireless transmit / receive unit (WTRU), wherein the measurement configuration information indicates at least a first measurement resource and a second measurement resource, wherein the first measurement resource is associated with a first transmission path to the WTRU using the RIS, and wherein the second measurement resource is associated with a second transmission path to the WTRU independent of the RIS; receiving a report from the WTRU, wherein the report indicates a result of at least one of a first measurement performed based on the first measurement resource or a second measurement performed based on the second measurement resource; determining whether to update a status of the RIS based on the report received from the WTRU; as well as Based on a determination to update the status of the RIS, a configuration message is transmitted to the RIS, wherein the configuration message at least indicates that the status of the RIS is to be updated.

Images