Enhanced Precoding Indication for Uplink Transmissions - Patent application

Abstract

A wireless transmit / receive unit (WTRU) may determine a precoding codebook. The WTRU may receive downlink control information (DCI) scheduling an uplink transmission. The DCI may include rank information, precoder information, a first indication associated with a first codeword (CW), and a second indication. Furthermore, the WTRU may determine a subset of the precoding codebook based on the rank information. The WTRU may determine a precoder from the subset of the precoding codebook based at least in part on the precoder information and the second indication, on a condition that the rank information indicates that the rank is less than or equal to a threshold value. Furthermore, the WTRU may transmit a first CW in the uplink transmission using the precoder based on the first indication. In an example, the second indication may be associated with a second CW. In another example, the second indication may be associated with a precoder selection.

Description

[Background technology]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 411,348, filed September 29, 2022, U.S. Provisional Patent Application No. 63 / 445,357, filed February 14, 2023, U.S. Provisional Patent Application No. 63 / 455,790, filed March 30, 2023, and U.S. Provisional Patent Application No. 63 / 465,666, filed May 11, 2023, the contents of which are incorporated herein by reference.

[0002] In multiple input multiple output (MIMO) communications, several enhancements to uplink transmissions are being developed for certain categories of wireless transmit / receive units (WTRUs) to enhance communication coverage, reliability, and throughput. The enhancements include uplink demodulation reference signal (DM-RS), sounding reference signal (SRS), SRS resource indicator (SRI), and transmit precoding matrix indicator (TPMI) enhancements that enable eight transmission (Tx) antenna uplink operation supporting four or more layers per WTRU in uplinks targeting customer premises equipment (CPE), fixed wireless access (FWA), vehicles, and industrial devices. Further enhancements may include coherence assumptions, full power modes, non-full power modes, and the like.

[0003] In current communications, the WTRU receives the TPMI in the scheduling downlink control information (DCI) and uses the scheduling DCI to determine the precoding matrix required for transmission. Moreover, codebook-based precoding may also be used. Summary of the Invention

[0004] A wireless transmit / receive unit (WTRU) may receive a low-overhead transmit precoding matrix indicator (TPMI) / sounding reference signal (SRS) resource indicator (SRI) indication. Additionally, the WTRU may receive a codebook subset restriction indication. The WTRU may also send an uplink transmission based on uplink precoding. In an example, the uplink precoding may be based on the received low-overhead TPMI / SRI indication and the received codebook subset restriction indication. In an example, the codebook subset restriction indication may be received in a medium access control (MAC) control element (CE). In a further example, the codebook subset restriction indication may be received in downlink control information (DCI).

[0005] In another example, the WTRU may receive an antenna group index (AGI), and the uplink precoding may be further based on the received AGI. In an additional example, the WTRU may receive a transmission rank, and the uplink precoding may be further based on the received transmission rank. In yet another example, the WTRU may receive a mapping table, and the uplink precoding may be further based on the received mapping table. In yet another example, the WTRU may receive a scheduling grant, and the uplink precoding may be further based on the received scheduling grant. Furthermore, the WTRU may transmit an SRS transmission. In a further example, the TPMI / SRI indication may be associated with a precoded SRS resource.

[0006] In a further example, the WTRU may receive a channel state information (CSI) reporting configuration. Furthermore, the WTRU may generate a sub-codebook based on the received CSI reporting configuration, the received low-overhead TPMI / SRI indication, and the received codebook subset restriction indication. Uplink precoding may also be based on the sub-codebook. Furthermore, the WTRU may transmit uplink control information (UCI) including several precoders in the sub-codebook. In a further example, the UCI may include a desired number of co-phases. Furthermore, the WTRU may generate the sub-codebook by reducing several co-phases.

[0007] In a further example, the WTRU may receive concatenated bit fields corresponding to activated antenna ports. Additionally or alternatively, the WTRU may receive a first SRI index. The WTRU may then determine a first set of ports based on the first SRI index. Further, the WTRU may receive a second SRI index. The WTRU may then determine one or more offset values ​​for the second set of ports based on the second SRI index.

[0008] The WTRU may determine one or more precoding codebooks. The WTRU may receive a DCI scheduling an uplink transmission. The DCI may include rank information, precoder information, a first indication associated with a first codeword (CW), and a second indication. Moreover, the WTRU may determine a subset of the one or more precoding codebooks based on the rank information. Furthermore, the WTRU may determine a precoder from the subset of the one or more precoding codebooks based at least in part on the precoder information and the second indication, on a condition that the rank information indicates that the rank is less than or equal to a threshold value. Moreover, the WTRU may transmit a first CW in the uplink transmission using the precoder based on the first indication. In an example, the second indication may be associated with a second CW. In another example, the second indication may be associated with a precoder selection. In an example, the threshold value may be 4.

[0009] In a further example, the second indication may be associated with a precoder selection on condition that the rank information indicates that the rank is less than or equal to a threshold value. In a further example, the second indication may be associated with a second CW on condition that the rank information indicates a rank greater than a threshold value.

[0010] Moreover, the WTRU may transmit a second CW using precoder information based on the second indication. In an example, the second indication may indicate a modulation and coding scheme (MCS). In another example, the second indication may indicate a redundancy version (RV). In a further example, the second indication may indicate whether new data is to be transmitted.

[0011] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, in which like reference numerals indicate like elements and in which: [Brief explanation of the drawings]

[0012] [Figure 1A] FIG. 1 is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented. [Figure 1B] 1B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communication system illustrated in FIG. 1A according to one embodiment. [Figure 1C] 1B is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communication system illustrated in FIG. 1A according to one embodiment. [Figure 1D] 1B is a system diagram illustrating a further exemplary RAN and a further exemplary CN that may be used within the communication system illustrated in FIG. 1A according to one embodiment. [Figure 2] FIG. 1 is a system diagram illustrating an example uplink precoding mechanism. [Figure 3] 1 is a block diagram illustrating an example WTRU antenna configuration for WTRU transmissions. [Figure 4] FIG. 1 is a system diagram illustrating an example of uplink precoding according to antenna grouping. [Figure 5] FIG. 1 is a system diagram illustrating an example of a mapping of a transmit precoding matrix indicator (TPMI) indication as a function of an antenna group index (AGI). [Figure 6] FIG. 10 is a flow chart diagram illustrating an example of codebook subset selection and support for high-resolution uplink precoding. [Figure 7] FIG. 10 is a flow chart diagram illustrating another example of codebook subset selection. [Figure 8] FIG. 1 is a system diagram illustrating an example of a general precoding structure. [Figure 9] FIG. 10 is a graph illustrating an example of a comparison of average chord distance using different selection criteria. [Figure 10] FIG. 1 is a codebook diagram illustrating an example of a downlink (DL) codebook in a parent codebook for a precoder. [Figure 11] FIG. 1 is a codebook diagram illustrating an example of a reduced codebook. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1A illustrates 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, broadcasts, etc., to multiple wireless users. The communication system 100 may enable the multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communication system 100 may use 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-tailed unique word discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multicarrier (FBMC), etc.

[0014] 1A, communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of 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 also be referred to as a station (STA), may be configured to transmit 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 smartphone, 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, a head-mounted display (HMD), a vehicle, a drone, a medical device and application (e.g., remote surgery), an industrial device and application (e.g., robots and / or other wireless devices operating in an industrial and / or automated processing chain context), a consumer electronics device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be referred to interchangeably as a UE.

[0015] The communications 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 configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communications networks, such as the CN 106, 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 NodeB, an eNodeB (eNB), a Home NodeB, a Home eNodeB, a Next Generation NodeB such as a gNodeB (gNB), a New Radio (NR) NodeB, a site controller, an access point (AP), a wireless router, etc. While the base stations 114a, 114b are each depicted as a single element, it will be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0016] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may also be referred to as a cell (not shown). These frequencies may be licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for wireless services to a particular geographic area, which may be relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, one 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 per sector of the cell. For example, beamforming may be used to transmit and / or receive signals in desired spatial directions.

[0017] 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 communications 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).

[0018] More specifically, as described 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 and the WTRUs 102a, 102b, 102c in the RAN 104 may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 116 using Wideband CDMA (WCDMA). WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​Uplink (UL) Packet Access (HSUPA).

[0019] 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), which may establish the air interface 116 using Long Term Evolution (LTE), and / or LTE Advanced (LTE-A), and / or LTE Advanced Pro (LTE-A Pro).

[0020] In one 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 NR.

[0021] 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 jointly implement LTE radio access and NR radio access, e.g., using a dual connectivity (DC) principle. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0022] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement a wireless technology such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), etc.

[0023] 1A 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 workplace, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, etc. 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 yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or femtocell. 1A, the base station 114b may have a direct connection to the Internet 110. Therefore, the base station 114b may not be required to access the Internet 110 through the CN 106.

[0024] The RAN 104 can communicate with the CN 106, which may be any type of network configured to provide voice, data, application, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have various quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error resilience requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 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 shown in FIG. 1A , it will be understood that the RAN 104 and / or CN 106 may communicate directly or indirectly with other RANs that use the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may utilize NR radio technology, the CN 106 may also communicate with another RAN (not shown) using GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0025] The CN 106 may also serve 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 providing 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 Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and / or Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the network 112 may include another CN connected to one or more RANs, which may use the same RAT as the RAN 104 or a different RAT.

[0026] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with a base station 114a that can use cellular-based wireless technology and a base station 114b that can use IEEE 802 wireless technology.

[0027] 1B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1B, 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 understood that the WTRU 102 may include any subcombination of the foregoing elements while remaining consistent with an embodiment.

[0028] The processor 118 may be a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor (DSP), multiple 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), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1B depicts the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0029] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive, for example, IR signals, UV signals, or visible light signals. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF signals and light signals. It will be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0030] 1B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO techniques. 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.

[0031] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and demodulate signals received by the transmit / receive element 122. As mentioned above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as, for example, NR and IEEE 802.11.

[0032] 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. Additionally, the processor 118 may access information from and store data in any type of suitable memory, such as non-removable memory 130 and / or removable memory 132. The non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, etc. In other embodiments, the processor 118 may access information from and store data in memory that is not physically located on the WTRU 102, such as on a server or home computer (not shown).

[0033] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control the power to other components within the WTRU 102. The power source 134 may be any suitable device for providing power to the WTRU 102. For example, the power source 134 may include one or more dry batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0034] The processor 118 may also be coupled to a 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 instead of, information from the GPS chipset 136, the WTRU 102 may receive location information from base stations (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 obtain location information by way of any suitable location-determination method while remaining consistent with an embodiment.

[0035] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth 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. The peripherals 138 may include one or more sensors. The sensors may be one or more of a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor, a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, a humidity sensor, etc.

[0036] The WTRU 102 may include a full-duplex radio that may transmit and receive some or all of the signals associated with a particular subframe (e.g., for both the UL (e.g., for transmission) and DL (e.g., for reception) in parallel and / or simultaneously). The full-duplex radio may include an interference management unit to reduce or substantially eliminate self-interference through either hardware (e.g., a choke) or signal processing via a processor (e.g., via a separate processor (not shown) or processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio that may transmit and receive some or all of the signals (e.g., associated with a particular subframe for either the UL (e.g., for transmission) or DL ​​(e.g., for reception)).

[0037] 1C is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As described above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using E-UTRA radio technology. The RAN 104 may also communicate with the CN 106.

[0038] The RAN 104 may include eNode-Bs 160a, 160b, and 160c, although it will be understood that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, and 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, and 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0039] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, etc. As shown in FIG. 1C, the eNode-Bs 160a, 160b, 160c may communicate with each other via an X2 interface.

[0040] 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. While the foregoing elements are depicted as part of the CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0041] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may act as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, activating / deactivating bearers, selecting a particular serving gateway during 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.

[0042] The SGW 164 may be connected to each of the eNodeBs 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 inter-eNodeB handover, triggering paging when DL data is available to the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, etc.

[0043] The SGW 164 may be connected to a PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0044] The CN 106 may facilitate communication 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 communication between the WTRUs 102a, 102b, 102c and traditional landline communication devices. For example, the CN 106 may include or communicate 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 and / or wireless networks owned and / or operated by other service providers.

[0045] Although the WTRU is illustrated in FIGS. 1A-1D as a wireless terminal, it is contemplated that in certain representative embodiments, such a terminal may use a wired communication interface (e.g., temporarily or permanently) with the communication network.

[0046] In a representative embodiment, the other network 112 may be a WLAN.

[0047] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may access or interface with a distribution system (DS) or another type of wired / wireless network that carries traffic into and / or out of the BSS. Traffic to the STA originating from outside the BSS may arrive through the AP and be sent to the STA. Traffic originating from the STA to a destination outside the BSS may be sent to the AP to be sent to the respective destination. Traffic between STAs within the BSS may be sent through the AP; for example, a source STA may send traffic to the AP, and the AP may send traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic may be sent between a source STA and a destination STA (e.g., directly between them) using direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z Tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (e.g., all of the STAs) can communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an "ad hoc" mode of communication.

[0048] When using the 802.11ac infrastructure mode of operation, or a similar mode of operation, an AP can transmit beacons on a fixed channel, such as a primary channel. The primary channel can be a fixed width (e.g., a 20 MHz wide bandwidth) or a dynamically configured width. The primary channel can be the operating channel of the BSS and can be used by STAs to establish a connection with the AP. In a representative embodiment, carrier sense multiple access with collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, STAs (e.g., all STAs), including the AP, can sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) can transmit at any given time in a given BSS.

[0049] High-throughput (HT) STAs may, for example, use 40 MHz wide channels for communication via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0050] A very high throughput (VHT) STA may support 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. A 40 MHz and / or 80 MHz channel may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining eight contiguous 20 MHz channels or two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, after channel encoding, the data may be passed through a segment parser that may split the data into two streams. Inverse fast Fourier transform (IFFT) processing and time-domain processing may be performed separately on each stream. The streams may be mapped onto two 80 MHz channels, and the data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the above operations for the 80+80 configuration may be reversed, and the combined data may be sent to the medium access control (MAC).

[0051] Sub-1 GHz operating modes are supported by 802.11af and 802.11ah. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, while 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah can support meter-type control / machine-type communication (MTC), such as MTC devices within a macro coverage area. MTC devices may have specific capabilities, e.g., limited capabilities, including support for (e.g., support only for) specific and / or limited bandwidths. MTC devices may include batteries with above-threshold battery life (e.g., to maintain very long battery life).

[0052] A WLAN system may support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, including a channel that may be designated as a primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by the STA that supports the smallest bandwidth operating mode among all STAs operating in the BSS. In an 802.11ah example, the primary channel may be 1 MHz wide for a STA (e.g., an MTC-type device) that supports (e.g., only supports) the 1 MHz mode, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) setting may depend on the status of the primary channel. For example, if the primary channel is busy due to a STA (that only supports 1 MHz operating mode) transmitting to the AP, all available frequency bands may be considered busy even if most of the available frequency bands remain idle.

[0053] In the United States, the available frequency bands that may be used by 802.11ah are 902 MHz to 928 MHz. In South Korea, the available frequency bands are 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11ah is 6 MHz to 26 MHz depending on the country code.

[0054] 1D is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As described above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using NR radio technology. The RAN 104 may also communicate with the CN 106.

[0055] The RAN 104 may include gNBs 180a, 180b, and 180c, although it will be understood that the RAN 104 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, and 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In an embodiment, the gNBs 180a, 180b, and 180c may implement MIMO technology. For example, the gNB 180a, 180b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, and 180c. Thus, the gNB 180a may transmit wireless signals to and / or receive wireless signals from the WTRU 102a using multiple antennas, for example. 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 multipoint (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNBs 180a and 180b (and / or 180c).

[0056] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of different or scalable lengths (e.g., including different numbers of OFDM symbols and / or lasting different lengths of absolute time).

[0057] 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 can communicate with the gNBs 180a, 180b, 180c without accessing other RANs (e.g., eNode-Bs 160a, 160b, 160c, etc.). In a standalone configuration, the WTRUs 102a, 102b, 102c can utilize one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c can communicate with the gNBs 180a, 180b, 180c using signals in unlicensed bands. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate with / connect to a gNB 180a, 180b, 180c while also communicating with / connecting to another RAN, such as an eNode-B 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-Bs 160a, 160b, 160c may act as mobility anchors for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0058] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, supporting network slicing, DC, interworking between NR and E-UTRA, routing of user plane data to user plane functions (UPFs) 184a, 184b, routing of control plane information to access and mobility management functions (AMFs) 182a, 182b, etc. As shown in FIG. 1D, the gNBs 180a, 180b, 180c may communicate with each other via an Xn interface.

[0059] 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While the foregoing elements are depicted as part of the CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0060] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selecting a particular SMF 183a, 183b, managing registration areas, terminating non-access stratum (NAS) signaling, mobility management, etc. Network slicing may be used by the AMF 182a, 182b to customize CN support for the WTRUs 102a, 102b, 102c based on the type of service being utilized by the WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for MTC access, etc. The AMFs 182a, 182b may provide a control plane function for switching between the RAN 104 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.

[0061] The SMFs 183a, 183b may be connected to the AMFs 182a, 182b in the CN 106 via an N11 interface. The SMFs 183a, 183b may also be connected to the UPFs 184a, 184b in the CN 106 via an N4 interface. The SMFs 183a, 183b may select and control the UPFs 184a, 184b and configure the routing of traffic through the UPFs 184a, 184b. The SMFs 183a, 183b may perform other functions such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0062] The UPFs 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks such as the Internet 110 to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPFs 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 DL packets, providing mobility anchoring, etc.

[0063] The CN 106 may facilitate communication with other networks. For example, the CN 106 may include or communicate 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 and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to the local DNs 185a, 185b through the UPFs 184a, 184b via an N3 interface to the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b.

[0064] 1A-1D and the corresponding description thereof, one or more or all of the functions described herein with respect to one or more of the WTRUs 102a-d, base stations 114a-b, eNode-Bs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMFs 182a-b, UPFs 184a-b, SMFs 183a-b, DNs 185a-b, and / or any other devices described herein may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation devices may be used to test other devices and / or to simulate network and / or WTRU functionality.

[0065] The emulation 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 emulation devices may perform one or more, or all, functions while fully or partially implemented and / or deployed as part of a wired and / or wireless communications network to test other devices in the communications network. One or more emulation devices may perform one or more, or all, functions while temporarily implemented / deployed as part of a wired and / or wireless communications network. The emulation device may also be directly coupled to another device for the purpose of testing and / or performing tests using over-the-air wireless communications.

[0066] The one or more emulation devices may perform one or more functions, inclusive, while not being implemented / deployed as part of a wired and / or wireless communications network. For example, the emulation devices may be utilized in a test lab and / or test scenario within an undeployed (e.g., test) wired and / or wireless communications network to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (which may, for example, include one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0067] In MIMO communications, several enhancements to uplink transmissions are being developed for certain categories of WTRUs to enhance communication coverage, reliability, and throughput. The enhancements include uplink demodulation reference signal (DM-RS), sounding reference signal (SRS), SRS resource indicator (SRI), and transmit precoding matrix indicator (TPMI) enhancements that enable eight transmission (Tx) antenna uplink operation supporting four or more layers per WTRU in uplinks targeting customer premises equipment (CPE) / fixed wireless access (FWA) / vehicles / industrial devices. Further enhancements may include coherence assumption, full power mode, non-full power mode, and the like.

[0068] In current communications, the WTRU receives the TPMI in the scheduling downlink control information (DCI) and uses the scheduling DCI to determine the precoding matrix required for transmission. Moreover, codebook-based precoding may also be used.

[0069] FIG. 2 is a system diagram illustrating an example uplink precoding mechanism. One example illustrated in system diagram 200 includes a codebook-based uplink precoding mechanism. In codebook-based uplink precoding, the WTRU receives information associated with the rank, preferred precoding, and preferred beam for uplink transmission in a scheduling DCI. For example, the associated set of information for uplink precoding received in DCI format 0_1 ​​may be summarized as follows: The set of information includes the TPMI and number of layers, which may take up to 0 to 6 bits, and precoding options for single-layer, two-layer, three-layer, and four-layer transmissions. The set of information indicates the transmit beam, including the SRS resource set indicator, which may be zero or two bits, with multiple SRS resource set configurations to support multiple transmit / receive point (mTRP) uplink transmissions. The set of information also indicates the SRI, which may be zero or two bits.

[0070] 2, codeword (CW)-to-layer mapping may be performed on data for the CW in module 240. In that case, the output of module 220 may then be used as input for precoder 260, which may apply the received TPMI, the received SRI, or both to the CW. The CW may then be transmitted by transmit / receive elements 222, 223, 224, 225. In one example, transmit / receive elements 222, 223, 224, 225 may be configured to transmit signals to a base station, such as base station 114a, over the air interface 116 shown in FIG. 1A. In a further example, transmit / receive elements 222, 223, 224, 225 may be antennas configured to transmit and / or receive RF signals.

[0071] 3 is a block diagram illustrating an example WTRU antenna configuration for WTRU transmission. In the example shown in block diagram 300, Ng antenna groups equal to or greater than one may be considered, each group comprising a coherent antenna, and across groups, antennas may be non-coherent / coherent depending on the device type. An example of an antenna group may be a panel. Linear arrays (1D / 2D) of cross-polarized or single-polarized antenna configurations may also be considered. Within an antenna group, antenna elements are uniformly spaced.

[0072] To support codebook-based uplink transmission for 8Tx WTRU uplink transmissions, two main categories are used: Alt1-b and Alt2-a. Category Alt1-b includes an uplink 2Tx / 4Tx codebook and / or 8x1 antenna selection vector as a starting point for designing a codebook for a partially / non-coherent WTRU and a downlink Type I codebook as a starting point for designing a codebook for a fully coherent WTRU. Category Alt2-a includes an uplink 2Tx / 4Tx codebook and / or 8x1 antenna selection vector as a starting point for designing a codebook for a fully / partially / non-coherent WTRU.

[0073] As shown in configuration diagram 300, in Case 1, Ng is equal to 1, indicating one antenna group. Further, in Case 1, antenna layout 320 and antenna layout 330. Antenna layout 320 has an M of 2, indicating two rows of antennas, an N of 2, indicating two columns of antennas, and a P of 2, indicating there are two cross-polarized antennas for every four squares in the layout. Thus, antenna layout 320 has eight antennas in a group.

[0074] Also, antenna layout 330 for Case 1 has an M of 1, indicating one row of antennas, an N of 2, indicating two columns of antennas, and a P of 2, indicating there are two cross-polarized antennas for every four squares in the layout. Thus, antenna layout 330 has eight antennas in a group.

[0075] Additionally, both antenna layout 320 and antenna layout 330 have isotropic antenna patterns. They may both have indoor FWA, outdoor FWA, or industrial applications. Furthermore, both antenna layout 320 and antenna layout 330 have an antenna element gain of 8 decibels (dBi) relative to isotropy and a half-power beam width (HPBW) of 65 degrees for outdoor FWA applications.

[0076] Further, as shown in diagram 300, in Case 2, Ng is equal to 2, indicating two antenna groups. Also, in Case 2, antenna layout 340 has M of 1, indicating one row of antennas in each group, and each group has d G-V The antennas are separated vertically by an arbitrary distance of , where the N of 2 indicates two rows of antennas and the P of 2 indicates two cross-polarized antennas for every four squares in the layout. Thus, antenna layout 340 has eight antennas in two groups. As can be seen in Figure 3, antenna layout 340 has zero horizontal distance between groups.

[0077] Additionally, the antenna layout 350 for Case 2 has M of 1, representing one row of antennas, and each group is d G-H The antennas are separated horizontally by an arbitrary distance of . Additionally, antenna layout 350 has an N of 2, indicating two rows of antennas in each group, and a P of 2, indicating two cross-polarized antennas for every four squares in the group. Thus, antenna layout 350 has eight antennas in two groups.

[0078] Furthermore, both antenna layout 340 and antenna layout 350 have isotropic antenna patterns. They may both have indoor FWA, outdoor FWA, or industrial applications. Furthermore, both antenna layout 340 and antenna layout 350 have an antenna element gain of 8 dBi and a HPBW of 65 degrees for outdoor FWA applications.

[0079] Also, as shown in diagram 300, in Case 3, Ng is equal to 4, indicating four antenna groups. For example, in antenna layout 360, each group is separate in both the vertical and horizontal directions. Each group in antenna layout 360 has an M of 1, indicating one row of antennas, an N of 1, indicating one column of antennas, and a P of 2, indicating there are two cross-polarized antennas for every four squares in the layout. Each group is divided into d G-H are separated horizontally by an arbitrary distance of d G-V Thus, antenna layout 360 has eight antennas in four groups.

[0080] Further, as shown in the diagram 300, in case 3, the antenna layout 370 is divided into four groups, each of which has d G-H Each section of antenna layout 370 has an M of 1 to indicate one row of antennas, an N of 1 to indicate one column of antennas, and a P of 2 to indicate that there are two cross-polarized antennas for every four squares in the layout. Thus, antenna layout 360 has eight antennas in four groups.

[0081] 3, both antenna layout 360 and antenna layout 370 have isotropic antenna patterns. They may also have indoor FWA, outdoor FWA, or industrial applications. Furthermore, both antenna layout 360 and antenna layout 370 have an antenna element gain of 4 dBi and a HPBW of 110 degrees for outdoor FWA applications.

[0082] Given the scope of recent enhancements to wireless communications, greater overhead is expected for indication of information associated with rank, preferred precoding, and preferred beam for uplink transmissions. However, to maintain spectral efficiency of wireless networks, a low-overhead solution for SRI and / or transmitter precoder matrix indication for codebook-based uplink transmissions, as well as SRI indication for non-codebook-based uplink transmissions, would be advantageous.

[0083] FIG. 4 is a system diagram illustrating an example of uplink precoding with antenna grouping. As shown in the example system diagram 400, three precoding structures each perform CW-to-layer mapping on data for the CW. For example, in one example in the leftmost precoding structure of FIG. 4, module 420 performs CW-to-layer mapping on data for the CW. Furthermore, the output of module 420 can then be used as input for precoder 430, which can apply the received TPMI indication, the received SRI indication, or both to the CW. The CW can then be transmitted by eight antennas 422, 423, 424, 425, 426, 427, 428, and 429. In one example, the eight antennas 422, 423, 424, 425, 426, 427, 428, and 429 can transmit signals to a base station, such as base station 114a, over the air interface 116 shown in FIG. 1A.

[0084] Further, in the example shown in the central precoding structure of FIG. 4, module 440 performs CW-to-layer mapping on the data for the CW. Furthermore, the output of module 440 may then be used as input to two precoders 450, 455. Precoder 455 may apply a first received TPMI indication, a first received SRI indication, or both, to the CW. Furthermore, precoder 450 may apply a second received TPMI indication, a second received SRI indication, or both, to the CW. The CW from precoder 450 may then be transmitted by four antennas 482, 483, 484, and 485. Furthermore, the CW from precoder 455 may then be transmitted by four antennas 486, 487, 488, and 489. In one example, antennas 482, 483, 484, 485, 486, 487, 488, 489 can transmit signals over air interface 116 shown in FIG. 1A to a base station, such as base station 114a.

[0085] In another example, shown in the rightmost precoding structure of FIG. 4 , module 460 performs CW-to-layer mapping on data for the CW. Furthermore, the output of module 460 may then be used as input for four precoders 470, 472, 474, and 476. Precoder 476 may apply a first received TPMI indication, a first received SRI indication, or both, to the CW. Furthermore, precoder 474 may apply a second received TPMI indication, a second received SRI indication, or both, to the CW. Similarly, precoder 472 may apply a third received TPMI indication, a third received SRI indication, or both, to the CW. Similarly, precoder 470 may apply a fourth received TPMI indication, a fourth received SRI indication, or both, to the CW. The CW from precoder 470 may then be transmitted by two antennas 492, 493, the CW from precoder 472 may then be transmitted by two antennas 494, 495, the CW from precoder 474 may then be transmitted by two antennas 496, 497, and the CW from precoder 476 may then be transmitted by two antennas 498, 499.

[0086] The CW may then be transmitted by eight antennas 492, 493, 494, 495, 496, 497, 498, 499. In one example, the eight antennas 492, 493, 494, 495, 496, 497, 498, 499 may be configured to transmit signals over the air interface 116 shown in FIG. 1A to a base station, such as base station 114a.

[0087] Based on the overall precoding structure shown in FIG. 4 , to support uplink precoding with a larger number of antennas for MIMO or NR MIMO, several enhancements in the codebook structure and indications would be advantageous. In particular, the examples provided herein address the following issues for an 8-Tx WTRU: The examples provided herein address control signaling associated with SRI / TPMI indication, which may be used for either or both of Alt1-b and Alt2-a, reducing overhead, or both. The examples provided herein also address unified indication for both coherent and non / partially coherent WTRUs, which may be used for either or both of Alt1-b and Alt2-a. As used in the examples and embodiments herein, the terms antenna panel, antenna group, and antenna port group may be used interchangeably.

[0088] The following examples and embodiments include low-overhead TPMI / SRI indication. Precoding structures for partitioning for TPMI / SRI indication per antenna group are included in the following examples and embodiments. For uplink transmission, the WTRU may partition the M-TX antenna set into K antenna groups consisting of N TX antennas per antenna group, where N≦M. It may be further assumed that the antennas within each antenna group are coherent. To simplify the presentation of the main ideas, each antenna group is assumed to have the same number of TX antennas, but the same presented solutions below may apply to cases where the antenna groups have different numbers of TX antennas.

[0089] To determine the uplink precoder, the WTRU may receive a K_TPMI TPMI indication and a K_SRI SRI indication, where K_TPMI≦K and K_SRI≦K. In a solution, the WTRU may receive two or more TPMI / SRI indications, e.g., two indications, where a first indication selects a TPMI / SRI value from a first set of possible TPMI / SRI values ​​and a second indication selects a TPMI / SRI value from a second set of possible TPMI / SRI values. Such an approach may be implemented in one example in the centralized precoding structure shown in FIG. 4.

[0090] The following examples and embodiments include different SRI / TPMI set sizes for each antenna group. For each antenna group, the size and combination of each possible set of SRI / TPMI values ​​may be different from other groups. For example, there may be more TPMI / SRI choices for the first antenna group and fewer choices for the remaining groups. In an example solution, there may be K1_TPMI possible choices for the first indication and K2_TPMI possible choices for the second indication, where K1_TPMI>K2_TPMI. In a solution, when the WTRU receives K1_TPMI indications, it may also receive (K1_TPMI-1) or fewer indicators and determine to be in-phase between each set of antenna groups. Such an approach may be implemented in the center precoding structure or the rightmost precoding structure shown in FIG. 4, for example.

[0091] The reduction of options may be performed through an indicated codebook subset restriction, where the indication may be per antenna group, based on a combined radio resource control (RRC)+MAC control element (CE), or may be dynamically indicated by the MAC CE and / or DCI. The restriction may be applied to the antenna group itself or per precoding option per antenna group. In another solution, the subset restriction may be determined by the indicated modulation and coding scheme (MCS), where the subset restriction may apply for lower-order modulations.

[0092] The WTRU may receive multiple restrictions, and then it may receive a dynamic indication of the restrictions to be applied for interpretation of the received TPMI. The criteria for application of the subset restrictions may be based on some signal quality, for example, power per layer or power per antenna group. Power per antenna group may be used in one example if different power ratings per antenna group are supported.

[0093] The WTRU can determine the SRI / TPMI values ​​based on association, correlation, or both. For example, the WTRU can receive different TPMI codebooks depending on the antenna configuration reported by the WTRU, such as options a and b or categories a and b from FIG. 3. Different antenna setups may result in different correlations along the vertical or horizontal dimension. Reusing the same codebook elements and sizes for every antenna group index (AGI) may result in excessive signaling overhead because the bit field for TPMI can cover the entire precoding codebook, while there may only be a suboptimal subset of TPMI for a pair of AGIs.

[0094] FIG. 5 is a system diagram illustrating an example of mapping of TPMI indications as a function of AGI. In the example solution shown in system diagram 500, the WTRU can determine the mapping of TPMI indications to a codebook of precoders as a function of AGI. A parent codebook may be defined with size S_0 510, which includes the complete set of precoders, and a subset of the parent codebook 510 may be configured as a function of AGI. For example, a WTRU may report its supported number Ng of antenna port groups as part of its WTRU capabilities. The WTRU may receive a codebook configuration having Ng codebook subsets, where the first codebook subset is of size S_1 512, the second codebook subset is of size S_2, etc., until the Ng-th codebook subset is of size S_Ng 515. Each codebook subset may be defined as a subset of precoders from the parent codebook S_0 510.

[0095] Also in the example shown in FIG. 4 , module 540 performs CW-to-layer mapping on the data for the CW. Furthermore, the output of module 540 may then be used as input for two precoders 560, 565. Precoder 560 may apply a first received TPMI indication, a first received SRI indication, or both, to the CW. Furthermore, precoder 565 may apply another received TPMI indication, another received SRI indication, or both, to the CW. The other received TPMI indication may be the last one in a set of N TPMI indications received and applied by the WTRU. Furthermore, the other received SRI indication may be the last one in a set of N SRI indications received and applied by the WTRU. The CW from precoder 560 may then be transmitted via antennas 522, 524. Furthermore, the CW from precoder 565 may then be transmitted via antennas 526, 528. In one example, antennas 522, 524, 526, 528 can transmit signals over air interface 116 shown in FIG. 1A to a base station, such as base station 114a.

[0096] The WTRU may also be configured with an association between a codebook subset and an antenna port group. For example, AGI 1 may be associated with a first codebook subset of size S_1 512. The WTRU may receive a TPMI for AGI 1 and may determine to use one of the S_1 precoders from the codebook over the antenna port that includes AGI 1. The WTRU may similarly determine precoders for other AGIs. When the WTRU receives an UL grant that may indicate an Ng TPMI, the WTRU may determine a precoder for each AGI by using the respective codebook for each AGI. The WTRU may then transmit a physical uplink shared channel (PUSCH) using the selected precoder for each AGI. The WTRU may receive MAC-CE or RRC signaling to reconfigure the contents of the associated subset of precoders for each AGI, e.g., S_i.

[0097] If all codebook sizes are equal, the WTRU can receive Ng TPMI using the same number of bits per TPMI. In one example where all codebook sizes are equal, S_i=S for all i. In an example solution, even if all codebook sizes are equal, such as S_i=S for all i, the available choices in each codebook may be different.

[0098] In an example solution, the Ng TPMI subsets may be arranged in a hierarchical structure such as S_1>S_2>···>S_g, thereby achieving different numbers of bits per TPMI. This arrangement may be determined as a function of the AGI structure of the WTRU. For example, TPMI1=i_1 may indicate the first precoder from the S_1 codebook 512 for AGI 1. For TPMI2, the WTRU may determine a codebook of size S_2 based on a subset of precoders from S_0 510 that is conditional on TPMI1. For example, if TPMI1=i_1 is indicated, then indices j_1,···j_S2 from S_0 510 are selected. If TPMI1=i_2, then a different subset of indices may be taken from S_0, thereby forming the codebook for TPMI2. Similar conditional constructions may be devised for other AGIs. The WTRU may receive MAC-CE or RRC signaling, thereby reconfiguring the associated set of precoders among S_i.

[0099] In some example solutions, the WTRU may receive a preconfigured association between codebook indices such that the WTRU can determine two or more TPMIs for two or more AGIs based on a single explicit TPMI indication for a reference AGI. The reference AGI may be indicated by the WTRU in its capability report or signaled by the network in a preconfigured association. For example, for a WTRU with two AGIs, AGI1 may be defined as the reference AGI, and TPMI1 for AGI1 may indicate a precoder from a codebook of size S1. For AGI2, TPMI2 may consist of a single precoding vector taken from a codebook of size S_2=1 associated with TPMI1. The WTRU may receive its association to TPMI2 and TPMI1 as a preconfigured set of precoders. If the WTRU receives a grant for TPMI1, the WTRU can transmit a PUSCH using TPMI1 and the associated TPMI2 via AGI1 and AGI2, respectively, without receiving an explicit TPMI2 in the grant.

[0100] Examples and embodiments provided herein may include enhanced rank indication. Furthermore, examples provided herein may include rank information separate from the TPMI indication. In an example solution, the WTRU may receive, for example, K_TPMI indications corresponding to respective antenna groups among K antenna groups, where each indication may correspond to a different rank for transmission by the corresponding antenna group. In an alternative or additional solution, the WTRU may receive a first indication, such as via MAC CE, DCI, another implicit / explicit indication, etc., and determine the transmission rank accordingly. The WTRU may then determine only the precoding information from the received indicated TPMI. Once the WTRU determines the indicated rank, it may identify a preferred precoding and apply the precoding for the uplink transmission. One or more of the following further examples may also apply accordingly. In one example, the WTRU may use the indicated rank to determine the number of layers to use for transmission.

[0101] In an example solution, for example, in industrial and FWA applications where some of the information related to a transmission may change slowly over time, a WTRU may receive a DCI for a first indication, where the received DCI may carry, for example, a transmission rank or an SRI. In an example solution, a common DCI may be used to indicate such information for several WTRUs.

[0102] In another example solution, the rank information may be determined by using a rank-related radio network identifier (RNTI) used for scrambling a cyclic redundancy check (CRC) of the DCI carrying the TPMI / SRI information. Using the first indication, the WTRU may determine the transmission rank for the entirety of transmissions over the M_TX antenna set, or may determine that the transmission rank is per antenna group.

[0103] In a further example solution, the WTRU may receive K DCI messages, each DCI message may carry at least one of a rank, TPMI, and / or SRI indication for uplink transmission. The WTRU may determine the association of each DCI message to an antenna group from an index carried in the DCI message and based on information related to their resource mapping, e.g., according to a physical downlink control channel (PDCCH) mapping order, or based on one or more of the RNTIs, e.g., antenna group-RNTIs, used for scrambling the CRC of the DCI message.

[0104] In yet another example solution, the WTRU may determine a set of applicable TPMI indices to be mapped to a TPMI field in the DCI for an antenna group, e.g., based on the received indicated rank (L) for each antenna group. In one example, the set of applicable TPMI indices may be applicable for each corresponding antenna group. In a further example, the TPMI field may include a "number of precoding information and layers" field.

[0105] The set of applicable TPMI indices is rank L, rank f1(L), rank f2(L), ···, rank f b (L), ··· and rank f B (L) may include one or more TPMI indices corresponding to fb (L) is a rank value based on the bth predetermined or pre-configured function (with respect to L). In one example, corresponding may be considered to be one or more of relating, based on, relating to, or mapped. In one example, f1(L), rank f2(L), ..., and rank f B At least one of (L) may be composed of or associated with a value of L. An independent value of B may be associated with each L. In one example, an associate may be considered to be used, composed of, or both.

[0106] In one example, the WTRU may receive a pre-configured or indicated mapping table. The mapping table may include an indicated rank, represented by L. Additionally, the mapping table may include the number of ranks for a set of applicable TPMI indices, represented by B.

[0107] L, B, f b An example of a pre-configured or indicated mapping table between rank f1(L), rank f2(L), and rank f3(L) is shown in Table 1. Based on Table 1, the WTRU can determine which value of B applies in response to receiving the indicated rank (L). Based on the value of B, the WTRU can determine whether the set of applicable TPMI indices is rank f1(L), . . . , rank f4(L), . . . B (L) may include one or more TPMI indices corresponding to or associated with at least one of (L). In one example, the one or more TPMI indices may be from a table associated with a parent TPMI, from a parent codebook, and / or from the (entire) applicable row of a "Precoding Information and Number of Layers" field mapping table, which may also be according to the coherency parameter. This may provide benefits in terms of reduced signaling overhead with respect to the DCI field size, which may be an important factor in the reliability of the control channel over which the DCI may be transmitted.

[0108] [Table 1]

[0109] In one example, the WTRU may use L, B, f b The WTRU may receive a pre-configured or indicated mapping table between rank f1(3) (which is rank 1 from Table 1), rank f2(3) (which is rank 2 from Table 1), and rank f3(3) (which is rank 3 from Table 1) as shown by the strike-through marks in Table 2 below. B=3 The set of applicable TPMI indexes can be determined by removing / excluding one or more rows for TPMI indexes that do not correspond to (3).

[0110] Table 2 is an example of determining the set of applicable TPMI indices from a parent table / codebook. The remainder of the rows in Table 2 that have not been removed / excluded can be re-indexed, for example, from TPMI index=0, resulting in a low-overhead TPMI field construction with a reduced TPMI field bit width / size. This is an example based on an example parent codebook with coherency-related parameters set to “fullyAndPartialAndNonCoherent” and a maximum rank up to 4. The example parent codebook may be based on different coherency-related parameters set to “partialAndNonCoherent” or other applicable values, and / or based on a different maximum rank, for example, up to 8, etc., and the suggested WTRU behavior for at least determining the set of applicable TPMI indices may be applied to the configured and generated parent codebook.

[0111] [Table 2]

[0112] In one example, the WTRU may use L, B, f b The WTRU may receive a pre-configured or indicated mapping table between rank f1(2) (which is rank 1 from Table 1) and rank f2(3) (which is rank 2 from Table 1). The WTRU may receive an indicated rank (L) set to L=2 for the second antenna group, for example. In response to receiving the indicated rank of L=2, the WTRU may determine that the value of B is 2 based on Table 1. In response to determining B is 2, the WTRU may determine that the value of B is 2, as shown by the strikethrough marks in Table 3 below. B=2 The set of applicable TPMI indexes can be determined by removing / excluding one or more rows for TPMI indexes that do not correspond to (2).

[0113] Table 3 is an example of determining the set of applicable TPMI indices from a parent table / codebook. The remainder of the rows in Table 3 that are not removed / excluded can be re-indexed, for example, from TPMI index=0, resulting in a low-overhead TPMI field construction with a reduced TPMI field bit width / size. This is an example based on an example parent codebook with coherency-related parameters set to “fullyAndPartialAndNonCoherent” and a maximum rank up to 4. The example parent codebook may be based on different coherency-related parameters set to “partialAndNonCoherent” or other applicable values, and / or based on a different maximum rank, for example, up to 8, etc., and the suggested WTRU behavior for at least determining the set of applicable TPMI indices may be applied to the configured or generated parent codebook.

[0114] [Table 3]

[0115] In one example, the WTRU may receive a scheduling grant via a DCI associated with the UL, e.g., format 0_1, 0_2, etc., including at least two TPMI fields. In one example, the first TPMI field may correspond to a first antenna group and may be generated / constructed based on Table 2 above. Further, the second TPMI field may correspond to a second antenna group and may be generated / constructed based on Table 3 above. The WTRU may receive, along with the scheduling grant, a first value for the first TPMI field indicating index 4 as "layer 2: TPMI=0" and a second value for the second TPMI field indicating index 3 as "layer 1: TPMI=3." In response to receiving the values, the WTRU may apply, or e.g., generate, a first precoder, e.g., a two-layer precoder based on TPMI=0, on the first antenna group and a second precoder, e.g., a one-layer precoder based on TPMI=3, on the second antenna group. The WTRU may perform UL transmissions based on using a first precoder for the first antenna group and a second precoder for the second antenna group, which may be transmitted simultaneously from both the first antenna group and the second antenna group, for example, if the WTRU is configured / indicated to perform such simultaneous transmissions from more than one antenna group.

[0116] Examples and embodiments herein include optimized 8-port SRI indication for non-codebook based PUSCH transmission. In one example, when a WTRU is configured with non-codebook PUSCH transmission, it uses N SRS single-port SRS resources, and L maxThe WTRU may receive a configuration of an SRS resource set having a maximum number of layers. The WTRU may be scheduled to transmit a PUSCH, and the WTRU may determine a precoder for the PUSCH antenna port as a function of the SRI indication in the DCI that maps to the SRS resource. The WTRU may receive a DCI with a bit field that dynamically indicates the port index scheduled for PUSCH transmission. For example, Table 4 below shows the L max An example of one such table when =2 is shown below.

[0117] [Table 4]

[0118] Table 4 shows the L max 4 is an example of SRI indication for non-codebook based PUSCH transmission where L = 2. As can be seen in Table 4, each row represents max Since layers can be scheduled up to a maximum of N = 2, we can indicate the SRI port index, which can be one port or two ports. SRS For ports 0 to N SRS All possible pairs of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 110, 116, 117, 118, 120, 121, 122, 123, 124, 125, 130, 131, 132, 140, 141, 142, 143, 1

[0119]

number

[0120] where c k n is the combination coefficient (n chooses k), and the number of hits required is N indices is the smallest power of 2 greater than

[0121] Recent wireless communication specifications allow for a maximum of N SRSis 4. The N considered in the current discussion of the specification SRS If the same design principles are reused for up to N = 8, all existing tables that may require a large number of rows and significant specification impact will need to be redesigned. For example, SRS =8 and L max For = 8, a table with 255 possible indices with 8-bit fields is required. Therefore, in the following example, a solution is proposed to minimize the impact of the wireless communication specifications on the SRI indication and increase the efficiency of wireless communication.

[0122] In an example, the WTRU may receive concatenated bit fields corresponding to activated antenna ports. In an example solution, a WTRU configured with non-codebook PUSCH transmission may receive N SRS / N indicated using the indication mechanism used for the two SRS ports SRS The solution is to determine N SRS ports. SRS When N is greater than a threshold, e.g., 4, a WTRU configured with non-codebook PUSCH transmission may reduce N by using one or any combination of the following: SRS The WTRU may determine the indicated SRS port by using the indication mechanism used for N / 2 SRS port indication. SRS 1 and N SRS 2 Two concatenated SRI fields may be used for the indication of N ports, provided that SRS i The sum of N SRS is equal to N SRS i ≦N SRS Further, the WTRU may, for example,

[0123]

number

[0124] The WTRU may use a port mapping table for indication of up to an SRS port, and may use Table 4 to determine the indicated SRS port.

[0125] In an example solution, the WTRU may receive a first and second SRI. The WTRU may map the first received SRI index to Table 4 to determine a first set of indicated ports. The WTRU may then map the second received SRI index to Table 4 and determine one or more offset values ​​(N SRS / 2) may be added to the indicated port value from Table 4. In an alternative or additional solution, the offset value may be configurable and may be indicated to the WTRU.

[0126] For example, N SRS =8, N SRS i Two SRI indications may be used, with N = 4 ports. Each row in Table 4 may be indexed with up to 4 bits, as shown in the last two columns of Table 4. The WTRU may receive a DCI with two bit fields, with each bit field mapping to an index in the table. The WTRU may receive a first index of 4, indicating {0,1}, and a second index of 9, indicating {2,3}. The WTRU may map the first index to a first set of four ports, thus identifying ports 0 and 1. The WTRU then SRS 1 The second index can be mapped to a second set of four ports by adding a shift of {0,1,6,7} to the indication, such that ports {2,3}+4={6,7} are identified. The WTRU can then determine the SRS ports {0,1,6,7} for non-codebook based PUSCH transmission.

[0127] If a reserved field is indicated, the WTRU may determine that the port is not mapped. For example, if the first bit field indicates 10 instead of 4, the WTRU may determine that the first bit field indicates "reserved," ports {0, 1, 2, 3} are not identified, and only SRS ports {6, 7} are identified.

[0128] If both indices map to reserved fields, the WTRU may decide to transmit according to a predetermined behavior. For example, the WTRU may precode the PUSCH according to a preconfigured default precoder. In one example, the default precoder may be one TPMI from a codebook.

[0129] In some example solutions, the WTRU SRS A single SRI indication for each of the ports can be received, and the received indication can be divided into the first N SRS By applying it to the ports, it becomes 2*N SRS maps to N ports SRS By applying a shift of SRS Implicitly determines the indications for N ports. For example, SRS = 4 and L max = 4, the WTRU may receive an index of 4, which indicates {0,1}. The WTRU may determine that antenna ports {0,1,4,5} are identified.

[0130] In an example solution, the table may be configured by RRC signaling. The configuration may be based on the number of antenna groups.

[0131] Examples and embodiments herein include enhanced precoding structures. Furthermore, examples of antenna group selection and precoding structures are provided herein. For uplink transmission, the WTRU may partition the M TX antenna set into K antenna groups, with N TX antennas per antenna group, where N≦M. It may further be assumed that the antennas within each antenna group are coherent. To simplify the presentation of the main ideas, each antenna group is assumed to have the same number of TX antennas, but the same presented solutions below may also apply to cases where the antenna groups have different numbers of TX antennas.

[0132] In an example solution, the uplink precoder structure may be built based on a W=F W W W structure. F may be used to select a subset of antenna groups, and therefore all antenna groups, and F=I, where I is the identity matrix. The selection of F may be based on preferred WTRU directional transmissions, the coherence capabilities of the WTRU, etc.

[0133] W1 may include all preferred beam bases for precoding. W1 may be defined for the entire set of M TX antennas at the WTRU, or for a subset of antenna groups, or alternatively, for each antenna group. The set of beam bases may be fixed or preconfigured. Alternatively or additionally, for a given deployment scenario, the set of beam bases may be determined based on several measurements, for example, using a sounding reference signal to form W1. When W1 = I, no specific beam base may be selected.

[0134] W2 may include coefficients for beam selection and / or combining. W2 may be defined for the entire set of M TX antennas at the WTRU, or for a subset of antenna groups, or alternatively for each antenna group.

[0135] W3 may include a phase factor for coherence between different antenna groups. In a solution, the application of W3 may be determined based on the WTRU coherence capability.

[0136] An uplink precoder may be constructed using a subset of the component precoders (F, W1, W2, W3). For example, a first uplink precoder may be constructed using W1 and W2. Thus, the first uplink precoder may be denoted by W=W1W2, in one example. Furthermore, a second uplink precoder may be constructed using F, W1, and W2. As a result, the second uplink precoder may be denoted by W=FW1W2, in one example.

[0137] The WTRU may perform one or more of the following steps for determining a component precoder, such as one or more of F, W1, W2, or W3, for an uplink transmission. Determining F for selecting one or more of the K antenna groups for transmission may include one or more of the following steps. In an example solution, the WTRU may be configured with K SRS resource sets, each SRS resource set including SRS resources with N TX ports. Alternatively or additionally, the WTRU may be configured with one SRS resource set including K SRS resources, each with N TX ports.

[0138] Using the configured K SRS resources, the WTRU may perform K SRS transmissions, and the K transmitted SRS may or may not be precoded. In an example solution, once the transmission is complete, the WTRU may receive an implicit or explicit indication from the base station to identify L preferred antenna groups for uplink transmission. In one example, the base station may be a gNB. In an example solution, the WTRU may receive L≦K SRI indications to determine the L preferred antenna groups for uplink transmission. Additionally or alternatively, the WTRU may receive a length K bitmap or codeword to determine the L preferred antenna groups for uplink transmission.

[0139] Examples provided herein include identifying basis vectors. In an example solution, the WTRU may determine a component precoder W1 based on an SRI received from a gNB or base station, where the SRI may be associated with a precoded SRS resource. For example, the WTRU may determine one or more W1 candidate matrices based on measurements of a downlink reference signal and precode one or more SRS resources using the determined W1 candidate matrices. In one example, the downlink reference signal may be a non-zero power (NZP)-channel state information (CSI)-reference signal (RS). The WTRU may then send one or more SRS resources and receive an SRI that may indicate at least one of the SRS resources sent by the WTRU. The WTRU may determine W1 based on the received SRI. For example, the WTRU may use the same W1 used to precode the indicated SRS resource. One or more of the following may apply:

[0140] The number of SRS ports in the SRS resource may be the same as the number of beams in the W1 matrix, which may be indicated by the number of columns in W1, in one example. The number of SRS ports in the SRS resource may be determined based on the configuration of the W2 matrix. For example, if a 4-Tx codebook is used for W2, the number of SRS ports in the SRS resource may be 4. Similarly, if a 2-Tx codebook is used for W2, the number of SRS ports in the SRS resource may be 2. The W1 candidate matrix may be up to the WTRU implementation. The total number of W1 candidate matrices may be indicated as a WTRU capability. Alternatively or additionally, the WTRU may indicate the number of SRS resources needed for W1 selection. For example, if the WTRU determines N candidate matrices for W1, the WTRU may indicate to the base station that N SRS resources are needed for W1 determination. In one example, the base station may be a gNB. The total number of W1 candidate matrices may be configured by the gNB or the base station. For example, the gNB or base station may configure the number of SRS resources for W1 determination, and the WTRU may determine the W1 candidate matrix based on the configured number of SRS resources.

[0141] In another example solution, the WTRU may determine the component precoder W1 based on one or more SRIs received from the gNB or base station, where each SRI may be associated with an SRS resource including a single SRS port, e.g., a single-port SRS resource. For example, the WTRU may determine a set of beams, e.g., N precoding vectors, where each beam, e.g., a precoding vector, may be precoded to an SRS resource. The WTRU may receive an indication of a subset of beams, which may be one or more SRIs associated with the single-port SRS resource precoded with the set of beams. In one example, the indication of the subset of beams may be an indication of M precoding vectors, where M is less than or equal to N.

[0142] Each SRI may determine a beam of the W1 matrix, e.g., a column vector of the W1 matrix. Thus, if N beams are used for the W1 matrix, N SRIs may be indicated to the WTRU. The number of SRIs may be determined based on the number of beams in the W1 matrix, e.g., the number of columns in W1. The WTRU may determine W1 based on the indicated or determined set of SRIs. The number of SRIs may be determined based on the configuration of the W2 matrix. For example, if a 4Tx codebook is used for W2, the number of SRIs may be 4. Similarly, if a 2Tx codebook is used for W2, the number of SRIs may be 2.

[0143] In an additional or alternative solution, the WTRU may be configured with more than one single-port SRS resource. For example, the WTRU may be configured with L×N, K×N, or M single-port SRS resources. The configured SRS resources may be configured within the same SRS resource set or may be spread across K SRS resources according to the number of antennas per antenna group. In an example solution, using the configured single-port SRS resources, the WTRU may transmit P SRSs, each of which may be beamformed with a different spatial filter.

[0144] Upon transmission of the P SRSs, the WTRU may receive an indication to determine a preferred subset of beams P_basis for constructing W1. In an example solution, the WTRU may receive one or more SRIs to determine basis beams for forming the W1 matrix. Semi-static, dynamic, or a combination thereof may be used to indicate the preferred set of one or more basis beams. In an example solution, dynamic signaling, e.g., MAC CE or DCI, may indicate a preferred P_basis for constructing W1. In another example solution, more preferred beams than P_basis may be semi-statically configured, and then dynamic signaling, e.g., MAC CE or DCI, may indicate a preferred P_basis from the configured list.

[0145] In an example solution, the WTRU may determine the component precoder W2 based on a TPMI indication in the DCI scheduling the uplink grant. One or more of the following may apply: W2 may be used for combining beams in W1 per layer for PUSCH transmission, and the combining may be performed with power scaling and phase rotation of one or more beams in W1. One or more codebooks may be used for W2, and the WTRU may receive an indication of the codebook to use.

[0146] In another example solution, the WTRU may determine the component precoder W2 based on downlink channel measurements, e.g., NZP-CSI-RS, when channel reciprocity holds between the uplink and downlink. One or more of the following may apply: W2 may be determined by the WTRU based on a given W1 or FW1, which may be indicated by the base station. In one example, the base station may be a gNB.

[0147] In an example solution, one or more antenna groups may be used, configured, or both. Furthermore, each antenna group may be associated with a composite precoder, e.g., FW1W2. In one example, the number of antenna ports is the same across the antenna groups, and the WTRU may determine a common composite precoder, e.g., FW1W2, and the WTRU may determine a co-phasing precoder, e.g., W3, to achieve co-phase between different antenna groups. One or more of the following may be applied: A codebook may be used for W3, and the codebook may be predetermined, configured, or reported and known between a transmitter, e.g., a WTRU, and a receiver, e.g., a base station. In one example, the base station may be a gNB. A TPMI may be indicated for W3 in a DCI scheduling an uplink, e.g., a PUSCH transmission, e.g., using separate TPMI(s) for the other component precoders.

[0148] Examples provided herein include codeword-to-layer and antenna group mappings. In an example solution, for a transmission with two codewords, an 8Tx WTRU may use the following codeword-to-layer mapping for its uplink transmission, as shown in Table 5:

[0149] [Table 5]

[0150] Table 5 is an example of a codeword-to-layer and antenna group mapping. In the example associated with Table 5 above, the number of layers may be the same as the transmission rank. Furthermore, a WTRU with more than one antenna group, e.g., Ng=2, may support the following cases of layer splitting for ranks R=5 and R=6, as shown below in Table 6. Table 6 is an example of layers within one antenna group and layers split across two antenna groups.

[0151] [Table 6]

[0152] In an example solution, the WTRU may extend the principle of codeword-to-layer mapping to layer-to-antenna group mapping, so that the WTRU may not use more than one antenna group for transmission of layers of the same codeword.

[0153] In an exemplary solution, for a transmission with rank R=5, if the indicated layer split across antenna groups is (2,3), the first two layers corresponding to a first codeword may be mapped onto the first antenna group, and the second three layers corresponding to a second codeword may be mapped to the second antenna group. However, when the indicated layer split across antenna groups is (3,2), the first three layers corresponding to a second codeword may be mapped onto the first antenna group, and the second two layers corresponding to the first codeword may be mapped to the second antenna group.

[0154] Similarly, in another exemplary solution, for a transmission with rank R=7, if the designated layers divided across antenna groups is (3,4), the first three layers corresponding to a first codeword may be mapped onto the first antenna group, and the second four layers corresponding to a second codeword may be mapped to the second antenna group. However, when the designated layers divided across antenna groups is (4,3), the first four layers corresponding to a second codeword may be mapped onto the first antenna group, and the second three layers corresponding to the first codeword may be mapped to the second antenna group.

[0155] In an example solution, a WTRU with Ng=4 antenna groups may be assumed to operate with every two antennas as a pair, and similar principles as used for Ng=2 for layer splitting across antenna groups may be used. In the solution, the WTRU may support the following transmission modes, as shown in Table 7. Table 7 is an example of layers split across four antenna groups.

[0156] [Table 7]

[0157] In the example solution, by relying on pairing every two antenna groups, an 8Tx WTRU with Ng=4 can apply the same codeword-to-layer mapping principles for layer-to-antenna group mapping as used for Ng=2. Thus, the WTRU may not use more than one antenna group for transmission of layers of the same codeword.

[0158] The 8Tx WTRU can transmit more than one codeword only if rank R>4; otherwise, a single codeword is transmitted. To support dual-codeword PUSCH transmission, the 8Tx WTRU can receive an additional set of indications for the second codeword, which may include a second MCS field having a size of, for example, 5 bits, a second new data indicator (NDI) field (1 bit), and a second redundancy version (RV) field having a size of, for example, 2 bits. If the indicated rank in the received scheduling DCI is R≦4, the WTRU can use and interpret one or more DCI fields associated with the transmission of the second codeword for other purposes.

[0159] In an example solution, the WTRU may have a much larger number of precoders for transmissions for R≦4 than for transmissions with R>4. In an example solution, the WTRU may use and interpret one or more of the DCI fields associated with the transmission of the second codeword for determining the TPMI. For example, if R>4 and both the first and second codewords are transmitted, the DCI field may carry information about both codewords. However, if R≦4 and only the first codeword is transmitted, the DCI field may carry information about only the first codeword. Thus, the WTRU may use the DCI field that would otherwise be used to carry information about the second codeword to enhance the precoder resolution for the first codeword instead. As a result, the WTRU may enjoy improved wireless communications.

[0160] The WTRU may use the additional information to enhance the precoder resolution in one or more of the following ways. For example, the WTRU may use additional indications to determine precoders that may be associated with the same codebook. For example, using the same principle, e.g., a DFT-based codebook, a codebook may be generated that has N1 precoders for R=1, N2 precoders for R=2, N3 precoders for R=3, N4 precoders for R=4, N5 precoders for R=5, N6 precoders for R=6, N7 precoders for R=7, and N8 precoders for R=8, where N1+N2+N3+N4>N5+N6+N7+N8.

[0161] Additionally or alternatively, the WTRU may use additional information for determining a precoder from a different codebook. For example, according to one or more information elements in a portion of the indication associated with the second codeword, the WTRU may interpret the indicated TPMI by using a different codebook. For example, in a solution, if the NDI assigned to the second codeword is 0, the WTRU may interpret the indicated TPMI according to a design based on an existing DL codebook, and when the NDI for the second codeword is 1, the WTRU may interpret the indicated TPMI according to a design based on an existing UL codebook. In one example, the DL codebook may be an NR DL codebook, and the UL codebook may be an NR UL codebook.

[0162] In another example solution, additional information may be used to enhance the indicated TPMI by indicating a second precoder to be applied to the indicated precoder. The enhancing may be done by introducing a co-phasing operation, a cascaded precoder, a Kronecker co-matrix, and the like.

[0163] In an example solution, when R≦4, the WTRU may determine whether to use an additional indication associated with the second codeword using one or more of the following: In an example solution, to determine whether to use an additional indication, the WTRU may use a dynamic indication, e.g., a DCI or a MAC CE. In another example solution, the WTRU may make such a decision based on a particular indication in the scheduling DCI, e.g., one or more NDI bits associated with the second codeword, a particular RV value associated with the second codeword, etc. In an additional or alternative solution, the WTRU may make the decision based on a reserved codepoint or a particular indicated TPMI. For example, when TPMI=x, the WTRU may use one or more of the DCI fields associated with the second codeword to enhance the precoder resolution.

[0164] 6 is a flowchart illustrating an example of codebook subset selection and support for high-resolution uplink precoding. In the example shown in flowchart 600, a WTRU may report 620 its capability information, including antenna layout and maximum number of layers supported. In one example, the WTRU may report this information to a base station. In one example, the base station may be a gNB. In a further example, the WTRU may determine one or more precoding codebooks based on its antenna layout information. For example, the WTRU may determine 615 a set of precoding codebooks. Also, based on information in the capability information report received by the base station, the base station may determine the same set of precoding codebooks in the set determined by the WTRU.

[0165] In a further example, the WTRU may receive a scheduling DCI for an uplink transmission 630. The scheduling DCI may include two sets of DCI fields associated with a first codeword and a second codeword and may include rank information and precoder information. In a further example, the two sets of DCI fields associated with the first codeword and the second codeword include MCS, NDI, and RV information 625. Furthermore, the rank information and precoder information for the uplink transmission may be indicated jointly or separately to the WTRU.

[0166] Additionally, the WTRU may determine a subset of the one or more determined precoding codebooks based on the indicated rank formation 640. In one example, the WTRU may determine a subset of the precoding codebooks for selecting a precoder 635. In one example, the determined subset of the precoding codebooks may be a first subset of the precoding codebooks. As described further herein, the selection of the precoder may be based on rank.

[0167] In one example, if the rank is less than a threshold, the WTRU may determine a precoder from a first subset of a precoding codebook using the precoder information and at least a portion of one or more of the information related to the second set of MCS, NDI, and RV 650. In one example, the threshold may be 4. If the rank is above the threshold, the WTRU may determine a precoder using only the received precoder information. In one example, a second codeword for use in uplink transmissions is supported only when the rank is greater than a threshold, such as 4 645. If the rank is less than a threshold, such as 4, the WTRU may enhance the precoding resolution by utilizing unused DCI fields for indication of one or more of the second MCS, second NDI, or second RV. In this way, the WTRU can address more precoder options for low-rank transmissions.

[0168] The WTRU may also transmit the scheduled PUSCH using the determined precoder 660. In this manner, the WTRU may complete transmission 655 of the scheduled PUSCH.

[0169] 7 is a flowchart illustrating another example of codebook subset selection. In the example shown in flowchart 700, the WTRU may determine 720 one or more precoding codebooks. Further, the WTRU may receive 740 a DCI scheduling an uplink transmission. In one example, the DCI may include rank information, precoder information, a first indication associated with a first CW, and a second indication. The WTRU may determine 760 a subset of one or more precoding codebooks based on the rank information. The WTRU may also determine 780 a precoder from the subset of one or more precoding codebooks based on the rank information and the precoder information. Further, the WTRU may transmit 790 a first CW in the uplink transmission based on the first information and using the precoder.

[0170] In an additional example, the second indication may be associated with a second CW. In another example, the second indication may be associated with a precoder selection.

[0171] In a further example, the WTRU may determine a precoder from a subset of one or more precoding codebooks based at least in part on the precoder information and the second indication, on the condition that the rank information indicates that the rank is less than or equal to a threshold value. In one example, the threshold value may be 4.

[0172] In another example, the second indication may be associated with a precoder selection on the condition that the rank information indicates that the rank is less than or equal to a threshold value. In a further example, the second indication may be associated with a second CW on the condition that the rank information indicates a rank greater than a threshold value.

[0173] Furthermore, the WTRU may transmit a second codeword using precoder information based on the second indication. In one example, the second indication may indicate an MCS. In another example, the second indication may indicate an RV. In a further example, the second indication may indicate that new data should be transmitted.

[0174] For a WTRU using a precoding structure W=FW1W2W3, one or more of the following modes of operation may be considered: F may be considered for use in selecting one or more of the antenna groups. In an example solution, the WTRU may assume F such that at least one row contains all-zero elements in order to select a limited set of antenna groups for uplink transmission. For example, in an example solution, the WTRU may have an antenna layout consisting of four antenna groups, each pointed in a different direction, e.g., spanned by 90 degrees. The WTRU may then select only a subset of the antenna groups for its uplink transmission.

[0175] In an example solution, the WTRU may determine its assumption for W1 based on its coherence capabilities.

[0176] FIG. 8 is a system diagram illustrating an example of a general precoding structure. In the example solution shown in system diagram 800, in Alt1-b, a fully coherent WTRU can assume W1 ≠ I 860, and therefore W1 can comprise a preferred basis vector for precoded transmission. As mentioned above, W1 may be fixed or determined based on channel sounding. Additionally, a partially coherent WTRU can also assume W1 ≠ I, however, W2 870 may be determined for each antenna group, and W3 880 may be used for co-phasing. As shown in FIG. 8, F 850 ​​can be located at the beginning of the precoding structure.

[0177] 8 in Alt2-a, a non-coherent WTRU may assume W1=I 820, and thus W2 830 may include information for antenna selection and / or combining. Furthermore, a partially coherent WTRU may also assume W1=I 820, where W2 830 may be determined for each antenna group, and further, W3 840 may be used for co-phasing. As in the example of Alt1-b, in Alt2-a, F 810 may be located at the beginning of the precoding structure.

[0178] The examples provided herein include enhancements for DL ​​Type I codebooks for uplink use. The general codebook structure for downlink transmission is defined by the structure W = W1W2, where the precoding operators W1 and W2 are denoted by indices i1 and i2. Index i1 is a complex index that selects the DFT vector corresponding to the strongest beam and is defined as follows:

[0179]

number

[0180] where v∈{1,2,···,8} is the number of transmission layers.

[0181] The entire DFT vector contains N1O1 and N2O2 beams spread across the horizontal and vertical dimensions, where N1 and N2 are the number of configured CSI-RS ports in the horizontal and vertical dimensions, respectively, and O1 and O2 are their configured oversampling ratios to increase the spatial resolution for beamforming. In this indication process, the index i 1,1 and i 1,2 selects the best horizontal and vertical beams spanned by pairs (N1,O1) and (N2,O2), respectively. For v∈{2,3,4}, i 1,3 is used to select the orthogonal beam between layers 1 / 2 and 3 / 4. Additionally, index i2 is for selecting one of four phase values ​​for inter-polarization co-phasing.

[0182] If the NR DL Type I codebook is used as the basis for designing a codebook for uplink transmissions, one or more of the following may be used: The WTRU may declare its coherence capability to indicate its suitability for use with the DL Type I codebook; for non-fully coherent WTRUs, other codebooks may be used. If the WTRU is not fully coherent, the WTRU may indicate the number of antenna groups for the purpose of indicating the need for coherence. In an example solution, the WTRU may also indicate the N1 and N2 values ​​supported according to its antenna configuration. In a further example solution, the WTRU may be indicated to use values ​​smaller than the indicated N1 and N2 values. In an additional or alternative solution, the N1 and N2 values ​​may be fixed. In another example solution, the WTRU may also indicate the O1 and O2 values ​​supported according to its antenna configuration. In a further example solution, the WTRU may be indicated to use values ​​smaller than the indicated O1 and O2 values. In an additional or alternative solution, the O1 and O2 values ​​may be constant. In an example solution, the WTRU may apply in-phase if the WTRU indicates that there are more than two antenna groups, in other words, Ng>1.

[0183] The following examples and embodiments involve codebook size reduction. The total number of precoders in a codebook may be a function of the number of coherence phases. The number of precoders in a codebook may be reduced by half when the number of coherence phases is reduced by half. The number of precoders may also be reduced by using a subset of precoders. Reducing the number of coherence phases and / or using a subset of precoders may be referred to as codebook subset restriction. Codebook subset restriction may be applied to the antenna group itself or to the precoding options per antenna group.

[0184] In one example, the number of N in-phase can be determined using e j2πn / N , provided that n = 0, ···, N - 1. To select a smaller number M of in-phase, the following can be performed. e j2πm / M By replacing N with M as, a smaller number M of in-phase can be generated, provided that m = 0, ···, M - 1, and M < N. Additionally or alternatively, M in-phase subsets may be extracted from the set of N in-phase.

[0185] The WTRU can receive a CSI reporting configuration, which indicates to the WTRU to generate a sub-codebook according to a set of a parent codebook and restriction rules. For codebook subset list restrictions, one or more of the following may apply.

[0186] In an example, the WTRU can perform sub-codebook generation by reducing the number of in-phase. In an exemplary solution, the WTRU can indicate a preferred number M of in-phase in the uplink control information (UCI). In one example, the WTRU can determine and report a preferred value of M based on its hardware capabilities. For example, the WTRU may not be able to generate a certain set of pre-coders resulting from the use of a higher value of M due to its hardware constraints / hardware impairments.

[0187] In another exemplary solution, the WTRU can indicate a maximum number M_max of in-phase as part of its capabilities. Then, the WTRU can receive a value of M, provided that the configured value of M can be less than or equal to M_max. The received value of M can be, for example, an RRC configured in the CSI reporting configuration or dynamically indicated by MAC-CE and / or DCI.

[0188] In an example, the WTRU may perform sub-codebook generation by extracting precoders from a parent codebook. In an example, the WTRU may generate a sub-codebook by extracting a preferred number of precoders from a parent codebook. In one example, the WTRU may extract a preferred number of precoders for 8 antenna transmissions from a parent codebook for 16 antenna transmissions. In another example, the WTRU may extract a preferred number of precoders for 8 antenna transmissions from a parent codebook for 32 antenna transmissions.

[0189] The number of precoders in a sub-codebook may be based on WTRU capabilities, and / or the use case, e.g., URLLC or eMBB, and / or operating conditions, e.g., channel quality indicator (CQI), signal-to-interference-and-noise ratio (SINR), available power, distance between precoders, etc.

[0190] The WTRU may indicate one or more of the following in the UCI: the number of precoders in the sub-codebook; the precoder index extracted from the parent codebook; the precoder index may be indicated using a bitmap, where the number of bits in the bitmap is equal to the number of precoders in the parent codebook; or the parameter settings of the parent codebook. A bit value of "1" in the bitmap may correspond to the index of a precoder in the parent codebook that is included in the sub-codebook. Also, a bit value of "0" in the bitmap may correspond to the index of a precoder in the parent codebook that is excluded in the sub-codebook. In an example, the parameter settings of the parent codebook may include one or more of the number of antennas on a panel, the number of panels, a DFT oversampling factor, or the number of coherence phases used in the parent codebook.

[0191] Additionally or alternatively, the WTRU may receive one or more of the above indications via an RRC configuration and / or MAC-CE and / or DCI.

[0192] In another example solution, the WTRU may generate a sub-codebook by extracting a number of non-cophasing precoders from the parent codebook, where the non-cophasing precoders are e j2πm / M Additionally or alternatively, non-cophasing precoders may be defined as the set of precoders that have a cophase of zero radians / degree.

[0193] The extraction of the non-cophasing precoder from the parent codebook may be based on WTRU capabilities, hardware limitations / impairments, and / or use cases, e.g., URLLC or eMBB, and / or operating conditions, e.g., CQI, SINR, available power, etc.

[0194] The WTRU may indicate, in the UCI, one or more of the number of non-cophasing precoders in the sub-codebook; the non-cophasing precoder index extracted from the parent codebook; or the parameter settings of the parent codebook. A bit value of “1” in the bitmap may correspond to the index of the non-cophasing precoder in the parent codebook that is included in the sub-codebook. Furthermore, a bit value of “0” in the bitmap may correspond to the index of the non-cophasing precoder in the parent codebook that is excluded in the sub-codebook. In an example, the parameter settings of the parent codebook may include one or more of the number of antennas on a panel, the number of panels, or the DFT oversampling factor.

[0195] Additionally or alternatively, the WTRU may receive one or more of the above indications via an RRC configuration and / or MAC-CE or DCI.

[0196] In an example, the WTRU may perform sub-codebook generation by maximizing the distance between precoders. In an example solution, the sub-codebook may be generated based on the distance between precoders of the parent codebook. In one example, the sub-codebook may be generated by maximizing Equation 2, where A i is the i-th, and A j is the precoder of the j-th parent codebook. The WTRU may generate a sub-codebook of M precoders by extracting the M precoders with the maximum distance based on Equation 2.

[0197] max∀i,j||A i -A j || 2 , i≠j Equation 2 The WTRU may indicate a precoder index of the parent codebook contained in the sub-codebook in the UCI. The WTRU may indicate a parameter setting of the parent codebook in the UCI. The WTRU may receive an indication of a procedure index of the parent codebook contained in the sub-codebook using an RRC configuration and / or MAC-CE and / or DCI.

[0198] In another example solution, the WTRU may determine the in-phase values ​​based on a criterion that maximizes the distance between precoders. In one example, based on a criterion that maximizes the distance between precoders. In one example, the optimal in-phase values ​​for a sum of two in-phases are 0 and π radians. In another example, the optimal in-phase values ​​for a sum of four in-phases are 0, π / 2, π, and 3π / 2 radians.

[0199] In another example solution, the WTRU may generate a sub-codebook of precoders from a parent codebook based on maximizing the distance between two complex entries of the precoder. In one example, the WTRU may include only a set of precoders in the codebook based on the distance between two consecutive complex elements of the codebook. In another example, the WTRU may include only a set of precoders in the codebook based on one or more of the distance between the first two complex entries of the precoder, the distance between the third and fourth complex entries of the precoder, or the distance between the second and third entries of the precoder.

[0200] In an example, the WTRU may perform sub-codebook generation by utilizing correlation. In an example solution, the WTRU may determine a sub-codebook of precoders from a parent codebook based on correlation between the precoders. The WTRU may determine a set of M precoders from N precoders based on a criterion that minimizes correlation between the set of M precoders. The minimum correlation between the set of M precoders may be achieved by extracting precoders from the parent codebook and / or by choosing appropriate values ​​of co-phase.

[0201] In another example solution, the WTRU may be configured with only a subset of in-phases. In one example, the WTRU may be restricted to using only a subset of in-phases extracted from the set of in-phases. The subset of in-phases may be selected based on various requirements, such as, for example, any one or any combination of: the WTRU's ability to generate in-phase basis functions; hardware complexity / limitations and / or hardware impairments; channel quality and / or interference; minimizing correlation between precoders; minimizing correlation between precoders in the presence of spatial correlation between antenna elements; or minimizing correlation between precoders in the presence of spatial correlation between antenna elements and channel impairments.

[0202] The WTRU may indicate the in-phase subset in the UCI. Additionally or alternatively, the WTRU may receive an indication of the in-phase subset using one or more of an RRC configuration, a dynamic MAC-CE indication, or a DCI indication.

[0203] In another example solution, the WTRU can generate a sub-codebook from a defined set of complex symbols. In an example solution, the precoder codebook may be generated from a set of predetermined values. In one example, a codebook with eight precoders from predetermined complex values, e.g., 1+0j, -1+0j, may be generated as follows:

[0204] A codebook with eight precoders for three antenna transmission with predetermined values, for example, 1+0j and −1+0j, may be obtained as follows:

[0205]

number

[0206] Furthermore, the codebook may be generated based on different metrics, as shown in the following examples. For example, the codebook may be generated based on the chordal distance between entries in each column, e.g., the chordal distance between the first value in the first column and the second value in the first column, and / or the chordal distance between the second value in the first column and the third value in the first column, and / or the chordal distance between the first column and the second column, and / or the chordal distance between the first row and the second row. In another example, the codebook may be generated based on the correlation between columns of matrix G and / or the correlation between rows of parent codebook G.

[0207] An example of a sub-codebook H with four precoders extracted from a parent codebook G based on maximizing the chordal distance may be obtained as follows:

[0208]

number

[0209] The following examples and embodiments include selection criteria for choosing sub-codebooks from a parent codebook. An exemplary parent codebook for one layer with [N1,N2,O1,O2]=[4,1,2,1] and four in-phases may be generated using a Type 1 single panel codebook. Sub-codebooks may be derived from the parent codebook based on one or more of the following:

[0210] In one example, the codebook may be based on a first criterion or set of criteria. For example, a set of precoders may be extracted from the parent codebook based on one or more of the following: In one example, only precoders consisting of certain complex symbols may be extracted from the parent codebook. In one example, a precoder consisting of quadrature phase shift keying (QPSK) symbols (e.g., [1, -1, 1j, -1j]) may be extracted from the parent codebook. In another example, a precoder consisting of binary phase shift keying (BPSK) symbols, e.g., [1, -1], may be extracted from the parent codebook.

[0211] In a further example, a precoder, for example, a precoder of N elements [a1, a2,... a_N], may only be extracted from the parent codebook if the phase offset between a_n and a_(n+1) is greater than or equal to a threshold (e.g., the phase offset between a_(n) and a_(n+1) is greater than or equal to threshold_a) and / or if the phase offset between a_(n-1) and a_(n) is greater than or equal to a threshold (e.g., the phase offset between a_(n-1) and a_(n)) is greater than or equal to threshold_b).

[0212] In an additional or alternative example, if the phase offset between a_(n) and a_(n+1) is not equal to the phase offset between a_(n+1) and a_(n+2), the precoder, e.g., an N-element precoder [a1, a2,... a_N], may be extracted only from the parent codebook.

[0213] In a further example, the codebook may be based on a second criterion or set of criteria. For example, a set of precoders may be extracted from a parent codebook with a larger number of co-phases, and the extraction may be based on a criterion of minimum correlation between precoders. For example, a correlation coefficient may be determined for each precoder in the parent codebook for all precoders in the codebook of 32 precoders correlated with each other, and the 16 precoders with the smallest correlation are extracted from the parent codebook. Based on the correlation coefficients of the precoders, a set of precoders may be extracted from the parent codebook.

[0214] In another example, the codebook may be based on a third criterion or set of criteria. For example, the set of precoders may be extracted from the parent codebook based on one or more of the following: The set of precoders is drawn from the parent codebook based on the maximum chordal distance between each point of the precoders. In one example, for a precoder [a,b,c,d]^T, the chordal distance of the precoder may be determined as the average (chord(a,b)+chord(a,c)+chord(a,d)+chord(b,c)+chord(b,d)+chord(c,d)), where chordal (a,b) is the chordal distance between entry a and entry b of the precoder. In another example, the chordal distance of the precoder may be determined as the average (chord(a,b)+chord(b,c)+chord(c,d)).

[0215] 9 is a graph illustrating an example of a comparison of the mean chordal distances using different selection criteria. The example shown in FIG. 9 includes a comparison of the mean chordal distances of different resulting codebooks using different selection criteria.

[0216] FIG. 10 is a codebook diagram illustrating an example of a DL codebook in a parent codebook for precoders. In the example case shown in codebook diagram 1000, a DL codebook may be used as the parent codebook. In one example, the parent codebook may be an NR DL codebook. For example, a DL Type-I codebook of 32 precoders with [N1,N2,O1,O2]=[4,1,2,1] and four co-phases may be considered as a parent codebook containing 32 rank=1 precoders. The 32 precoders are represented in FIG. 10 by 32 columns. Eight rows may provide precoders used by up to eight antennas.

[0217] FIG. 11 is a codebook diagram illustrating an example of a reduced codebook. In the exemplary solution shown in codebook diagram 1100, different criteria may be used to prune the codebook to reduce the codebook size. In the exemplary solution, only QPSK-based precoders may be extracted from a Type I codebook of 32 precoders with [N1, N2, O1, O2] = [4, 1, 2, 1] and four co-phases. Thus, 16 QPSK-based precoders are shown in FIG. 11 by 16 columns. As in FIG. 10, eight rows can provide precoders used by up to eight antennas.

[0218] Examples of constructing and selecting multiple codebooks are included herein. In an exemplary solution, a precoding codebook for rank R>1 may be constructed based on a set of rank R=1 precoders. For example, a rank R=2 codebook may be realized by collecting N different pairs of rank R=1 precoders.

[0219] In an example solution, the WTRU may implicitly indicate its supported codebooks according to its antenna layout or the number of antenna groups. In an example solution, the WTRU may implicitly or explicitly indicate one of the antenna layout cases shown in Figure 3 as its supported antenna layout. Then, according to the indicated antenna layout, the WTRU may implicitly indicate to the gNB or base station to use one of the supported codebooks.

[0220] In an example solution, the WTRU may be configured, illustrated, or implemented to support two or more codebooks, and each codebook may be referenced by an index. Each codebook may be for each supported rank, or alternatively, may include all supported ranks. In an example solution, the WTRU may be semi-statically or dynamically instructed to use one of the codebooks for its uplink transmissions.

[0221] In the example solution, at least one N SRS A WTRU configured with an SRS resource set that includes a port SRS resource may be triggered to perform an SRS transmission. SRS This may be performed by simultaneous transmission from ports, or alternatively, it may be performed by N SRSThe SRS transmissions may be performed sequentially at intervals, with one of the non-coherent precoders being applied for transmission at each interval. In a solution, the SRS transmissions may be periodic or aperiodic. Following the SRS transmission, the WTRU may receive an indication, e.g., an index, to select one of the configured codebooks. In an example solution, the WTRU may be RRC configured to use a codebook. Additionally or alternatively, the WTRU may receive a MAC CE or DCI indication to activate a codebook. In another solution, the WTRU may receive a codebook selection indicator in the same scheduling DCI that carries the TPMI.

[0222] In an example solution, an 8Tx WTRU may support the following non-coherent precoders for its rank R=1 uplink transmission:

[0223]

number

[0224] For example, for a rank R=2 transmission, different combinations and permutations of rank R=1 precoders may be considered, and each codebook may be considered for a different WTRU antenna layout or transmission environment. For example, two or more rank R=2 codebooks may be considered using rank R=1 precoders, as shown below. Rank R=2, Codebook-1:

[0225]

number

[0226] Rank R=2, Codebook-2:

[0227]

number

[0228] For example, for a transmission with rank R=2, a WTRU having an antenna layout shown as case 1-b in Figure 3 may use a first codebook, while another WTRU having an antenna configuration shown as case 3-a may use a second codebook. Furthermore, in another example, a WTRU having antenna layout configuration case 3-a may use a first codebook in one deployment, e.g., an indoor scenario, and use a second codebook in another deployment / channel, e.g., an outdoor scenario.

[0229] Although features and elements are described above in particular combinations, those skilled in the art will understand that each feature or element may be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware embodied in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via wired or wireless connections) and 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 internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. 1. A method for use in a wireless transmit / receive unit (WTRU), comprising: determining one or more precoding codebooks; receiving downlink control information (DCI) scheduling an uplink transmission, the DCI including rank information, precoder information, a first indication associated with a first codeword (CW), and a second indication; determining a subset of the one or more precoding codebooks based on the rank information; determining a precoder from the subset of the one or more precoding codebooks based at least in part on the precoder information and the second indication, on the condition that the rank information indicates that the rank is less than or equal to a threshold value; transmitting the first CW in the uplink transmission using the precoder based on the first indication; A method comprising:

2. 2. The method of claim 1, wherein the second indication is associated with a second CW.

3. 2. The method of claim 1, wherein the second indication is associated with a precoder selection.

4. 2. The method of claim 1, wherein the threshold value is four.

5. 2. The method of claim 1, wherein the second indication is associated with a precoder selection on the condition that the rank information indicates that the rank is less than or equal to the threshold value.

6. 2. The method of claim 1, wherein the second indication is associated with the second CW on the condition that the rank information indicates that the rank is greater than the threshold value.

7. transmitting the second CW using the precoder information based on the second indication; The method of claim 6 further comprising:

8. 7. The method of claim 6, wherein the second indication indicates a modulation and coding scheme (MCS).

9. 7. The method of claim 6, wherein the second indication indicates a redundancy version (RV).

10. 7. The method of claim 6, wherein the second indication indicates whether new data is to be transmitted.

11. 27. A wireless transmit / receive unit (WTRU) configured to perform a method according to any one of claims 1 to 26, comprising: Walkie-talkies, and a processor operably coupled to the transceiver Equipped with the processor is configured to determine one or more precoding codebooks; The transceiver is configured to receive downlink control information (DCI) scheduling an uplink transmission, the DCI including rank information, precoder information, a first indication associated with a first codeword (CW), and a second indication; the processor is configured to determine a subset of the one or more precoding codebooks based on the rank information; the processor is configured to determine a precoder from the subset of the one or more precoding codebooks based on the precoder information and at least a portion of the second indication, on a condition that the rank information indicates that the rank is less than or equal to a threshold value; The processor and the transceiver are configured to transmit the first CW in the uplink transmission using the precoder based on the first indication. WTRU

12. 12. The WTRU of claim 11, wherein the second indication is associated with a second CW.

13. 12. The WTRU of claim 11, wherein the second indication is associated with a precoder selection.

14. The WTRU of claim 11 , wherein the threshold value is four.

15. 12. The WTRU of claim 11, wherein the second indication is associated with a precoder selection on the condition that the rank information indicates that the rank is less than or equal to the threshold value.

16. 12. The WTRU of claim 11, wherein the second indication is associated with the second CW on the condition that the rank information indicates that the rank is greater than the threshold value.

17. 17. The WTRU of claim 16, wherein the processor and the transceiver are further configured to transmit the second CW using the precoder information based on the second indication.

18. 17. The WTRU of claim 16, wherein the second indication indicates a modulation and coding scheme (MCS).

19. 17. The WTRU of claim 16, wherein the second indication indicates a redundancy version (RV).

20. 17. The WTRU of claim 16, wherein the second indication indicates whether new data is to be transmitted.

Images