Method, process and apparatus for improving beam resilience in multi-antenna system with hybrid beamforming

Abstract

In an embodiment, the WTRU is configured to apply to a data symbol a transform spread function that spreads the data symbol in a frequency domain to form a first beam, and to transmit the transform spread data symbol in the first beam. For example, embodiments for improving the reliability of signal detection on a compromised link include implementing a generalized space frequency block coding (GSFBC) process. The impairment may be caused by, for example, aging of channel state information, defects during channel state acquisition or reporting, and / or beam skew effects in a multi-antenna system. Embodiments may include the use of hybrid beamforming and GSFBC processes to improve the reliability of signal detection in the presence of beam skew and / or beam misalignment.

Description

[0001] Related Applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 414,229, filed on Oct. 7, 2022, and U.S. Provisional Application No. 63 / 531,176, filed on Aug. 7, 2023, the contents of which are incorporated herein by reference. SUMMARY OF THE INVENTION

[0003] Embodiments of methods, procedures, and devices for improving link stability in the presence of impairments caused by channel aging, deficiencies in the channel state acquisition or reporting process, and / or beam squint effects in multi-antenna systems (e.g., using hybrid beamforming or holographic beamforming) include a Generalized Space-Frequency Block Coding (GSFBC) procedure that aims to improve the reliability of detection in the presence of beam squint and / or beam misalignment.

[0004] Example methods and procedures for transmitting beams with improved link stability in a multi-antenna system may include one or more of the following operations:

[0005] - Obtaining configuration information about a codebook for a Transform Spreading function and thresholds T1 and T2;

[0006] - Obtaining capability information that includes, for example, a subset of the Transform Spreading functions supported by a receiver or any constraints related to the support of a Generalized Space-Frequency Block Coding (GSFBC) procedure;

[0007] - Obtaining a measurement or report of link performance degradation, such as an SNR degradation S1 caused by beam squint and / or an SNR degradation S2 caused by beam misalignment;

[0008] - Obtaining beam-related scheduling information, such as about beams serving other users or available transmit power;

[0009] - Selecting a function from the codebook of available Transform Spreading functions based on S1 being higher than threshold 1 (T1);

[0010] - Selecting a horizontal / vertical (H / V) beamwidth and the orientation of a diversity beam based on S2 being higher than T2 and permission from a scheduler to use the diversity beam; and

[0011] - Generating GSFBC-encoded symbols on the configured beam and transmitting GSFBC-related control signaling information.

[0012] Example methods and procedures for receiving beams with improved link stability in a multi-antenna system may include one or more of the following operations:

[0013] - Obtain configuration information about the transform spreading function and thresholds T3, T4, T5;

[0014] - Transmit capability information that includes, for example, a subset of supported transform spreading functions or any constraints related to the support of the generalized space-frequency block coding (GSFBC) process;

[0015] - Perform measurements of the performance degradation of the link, such as SNR degradation S3 caused by beam skew and / or SNR degradation S4 caused by beam misalignment;

[0016] - Trigger a request to activate GSFBC coding based on the user's speed being higher than T5;

[0017] - Report the performance degradation of the link caused by beam skew based on S3 being higher than T3;

[0018] - Report the performance degradation of the link caused by beam misalignment based on S4 being higher than T4;

[0019] - Obtain GSFBC-related control signaling information; and

[0020] - Perform detection of the GSFBC-coded beam by performing transform de-spreading on the symbols in the main beam and / or diversity beams and Alamouti-based combining.

[0021] In another example, the WTRU is configured to apply a transform spreading function that spreads data symbols in the frequency domain to the data symbols to form a first beam, and transmit the transform-spread data symbols in the first beam. For example, embodiments for improving the reliability of signal detection on a damaged link include implementing a generalized space-frequency block coding (GSFBC) process. The impairment can be caused by, for example, aging of the channel state information, defects in the channel state acquisition or reporting process, and / or beam skew effects in a multi-antenna system. And the embodiments can include using hybrid beamforming and the GSFBC process to improve the reliability of signal detection in the presence of beam skew and / or beam misalignment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] A more detailed understanding can be obtained from the following description given by way of example in conjunction with the drawings, in which like reference numerals indicate like elements and in which:

[0023] Figure 1A is a system diagram illustrating an example communication system in which one or more of the disclosed embodiments can be implemented;

[0024] Figure 1B is a system diagram of an exemplary wireless transmit / receive unit (WTRU) that can be used within the communication system illustrated in Figure 1A ;

[0025] Figure 1C is a system diagram of an exemplary radio access network (RAN) and an exemplary core network (CN) that can be used within the communication system illustrated in Figure 1A ;

[0026] Figure 1D is a system diagram of another exemplary RAN and another exemplary CN that can be used within the communication system illustrated in Figure 1A ;

[0027] Figure 2 is a diagram of a hybrid beamforming architecture according to an embodiment.

[0028] Figure 3 is a diagram of beam separation for respectively pre-compensating beam skew according to an embodiment, where two beams each carry half of the subcarriers.

[0029] Figure 4 is a diagram of a base station and a device connected by at least a pair of beams according to an embodiment.

[0030] Figure 5 is a diagram of transmission processing steps of GSFBC coding including transform spreading and generation of a main beam and a diversity beam according to an embodiment.

[0031] Figure 6 is a diagram of transmission processing steps for GSFBC coding including transform spreading and single beam transmission according to an embodiment.

[0032] Figure 7 is a diagram of transmission processing steps for GSFBC coding including transform spreading and transmission on two beams pointing in different directions and each including half of the subcarriers according to an embodiment.

[0033] Figure 8 is a diagram of transmission processing steps for GSFBC coding including generation of a main beam and a diversity beam according to an embodiment.

[0034] Figure 9 is a diagram illustrating the possibility of a diversity beam (blue / lighter shade) that shows a widened beam in the same or adjacent direction and beams in different directions with respect to the main beam (green / darker shade) in a single TRP scenario according to an embodiment.

[0035] Figure 10 FIG. is an illustration of a control signaling mechanism involved in activating GSFBC by a transmitter in response to a request from a receiver according to an embodiment.

[0036] Figure 11 is a flowchart of a signaling flow for a gNB to trigger activation / deactivation of GSFBC without a request from a receiving WTRU according to an embodiment.

[0037] Figure 12 is a diagram of a geometric layout of an antenna array for simulation using a UPA in the X-Z plane according to an embodiment.

[0038] Figure 13 is according to an embodiment using with beam skew and no beam misalignment Figure 12 of a chart of simulation results of a geometric layout of an antenna.

[0039] Figure 14 is according to an embodiment using with beam skew and random beam misalignment up to ±5% of the ideal direction Figure 12 of a chart of simulation results of a geometric layout of an antenna.

[0040] Figure 15 is according to an embodiment using with beam skew and random beam misalignment up to ±10% of the ideal direction Figure 12 of a chart of simulation results of a geometric layout of an antenna.

[0041] Figure 16 is a flowchart of a transmitted signal of a GSFBC encoded signal according to an embodiment.

[0042] Figure 17 is a flowchart of a method related to receiving a GSFBC encoded signal according to an embodiment.

[0043] Figure 18 is a block diagram of a receiver for GSFBC decoding according to an embodiment.

[0044] Figure 19 is a flowchart of a method for transmitting transformed extended data symbols in a beam according to an embodiment.

[0045] Figure 20 is a flowchart of a method for receiving data symbols in multiple beams according to an embodiment. DETAILED DESCRIPTION

[0046] Figure 1AFIG. is an illustration of an example communication system 100 in which one or more of the disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content (such as voice, data, video, messaging, broadcasting, etc.) to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content by sharing system resources, including wireless bandwidth. For example, the communication system 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique word discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multicarrier (FBMC), and so on.

[0047] As Figure 1A shown, the communication 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 the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a station (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 smart phone, a laptop computer, a netbook computer, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, a medical device and application (e.g., remote surgery), an industrial device and application (e.g., a robot and / or other wireless devices operating in the context of an industrial and / or automation processing chain), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, and so on. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0048] The communication system 100 may also include base station 114a and / or base station 114b. Each of base stations 114a, 114b may be any type of device configured to facilitate access to one or more communication networks (such as CN 106, Internet 110, and / or other networks 112) by wirelessly interfacing with at least one of WTRUs 102a, 102b, 102c, 102d. As an example, base stations 114a, 114b may be base transceiver stations (BTSs), Node Bs, eNode Bs (eNBs), home Node Bs, home eNode Bs, next-generation Node Bs (such as gNode Bs (gNBs)), New Radio (NR) Node Bs, site controllers, access points (APs), wireless routers, etc. Although each of base stations 114a, 114b is depicted as a single element, it will be understood that base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0049] Base station 114a may be part of RAN 104, which may also include other base stations and / or network elements (not shown), such as base station controllers (BSCs), radio network controllers (RNCs), relay nodes, etc. 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 be referred to as cells (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for wireless services to a specific geographical area, which may be relatively fixed or may change over time. A cell may also be split into cell sectors. For example, the cell associated with base station 114a may be split into three sectors. Thus, in one embodiment, base station 114a may include three transceivers, that is, each transceiver corresponds to one sector of the cell. In an embodiment, base station 114a may employ multiple-input multiple-output (MIMO) technology and may use multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

[0050] Base stations 114a, 114b may communicate with one or more of WTRUs 102a, 102b, 102c, 102d via air interface 116, which may be any suitable wireless communication link (such as radio frequency (RF), microwave, centimeter wave, millimeter wave, infrared (IR), ultraviolet (UV), visible light, etc.). Air interface 116 may be established using any suitable radio access technology (RAT).

[0051] More specifically, as described above, the communication system 100 can be a multi-access system and can employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c can implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), and the UMTS UTRA can use Wideband CDMA (WCDMA) to establish the air interface 116. WCDMA can include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA can include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed Uplink (UL) Packet Access (HSUPA).

[0052] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c can implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), and this E-UTRA technology can use Long-Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced Pro LTE (LTE-A Pro) to establish the air interface 116.

[0053] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c can implement a radio technology such as NR radio access, and this NR radio access can use NR to establish the air interface 116.

[0054] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c can implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c can implement LTE radio access and NR radio access together, such as using the Dual Connectivity (DC) principle. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c can be characterized by multiple types of radio access technologies and / or transmissions to / from multiple types of base stations (e.g., eNBs and gNBs).

[0055] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as, for example, 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.

[0056] Figure 1A The base station 114b in may be, for example, a wireless router, a home Node B, a home eNode B, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area (such as a business premise, a home, a vehicle, a campus, an industrial facility, an air corridor (such as for drones), a road, etc.). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a Wireless Local Area Network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a Wireless Personal Area Network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (such as WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a pico cell or a femto cell. As Figure 1A shown, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not need to access the Internet 110 via the CN 106.

[0057] The RAN 104 may communicate with the CN 106, which may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying Quality of Service (QoS) requirements, such as different throughput requirements, latency requirements, fault tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, location-based services for mobile devices, prepaid calling, Internet connectivity, video distribution, etc., and / or perform advanced security functions such as user authentication. Although in Figure 1AAlthough not shown, it will be understood that RAN 104 and / or CN 106 can communicate directly or indirectly with other RANs that employ the same RAT as RAN 104 or a different RAT. For example, in addition to being connected to RAN 104 that can utilize NR radio technology, CN 106 can also communicate with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0058] CN 106 can also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 can include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 can include a global system of interconnected computer networks and devices that use common communication protocols (such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite). The network 112 can include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the network 112 can include another CN connected to one or more RANs, and the one or more RANs can employ the same RAT as RAN 104 or a different RAT.

[0059] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 can include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d can include multiple transceivers for communicating with different wireless networks via different wireless links). For example, Figure 1A the illustrated WTRU 102c can be configured to communicate with a base station 114a that can employ a cellular-based radio technology and with a base station 114b that can employ IEEE 802 radio technology.

[0060] Figure 1B is a system diagram of an exemplary WTRU 102. As Figure 1B shown, the WTRU 102 can include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keyboard 126, a display / touchpad 128, a non-removable memory 130, a removable memory 132, a power supply 134, a Global Positioning System (GPS) chipset 136, and / or other peripheral devices 138, etc. It will be understood that the WTRU 102 can include any sub-combination of the foregoing elements while remaining consistent with the embodiments.

[0061] The processor 118 can be a general-purpose processor, a dedicated 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 can perform signal decoding, data processing, power control, input / output processing, and / or any other function that enables the WTRU 102 to operate in a wireless environment. The processor 118 can be coupled to a transceiver 120, and the transceiver 120 can be coupled to a transmit / receive element 122. Although Figure 1B the processor 118 and the transceiver 120 are depicted as separate components, it will be understood that the processor 118 and the transceiver 120 can be integrated together in an electronic package or chip.

[0062] The transmit / receive element 122 can be configured to transmit signals to, or receive signals from, a base station (such as base station 114a) via an air interface 116. For example, in one embodiment, the transmit / receive element 122 can be an antenna configured to transmit and / or receive RF signals. In an embodiment, the transmit / receive element 122 can be a transmitter / detector configured to transmit and / or receive signals such as IR, UV, or visible light signals. In yet another embodiment, the transmit / receive element 122 can be configured to transmit and / or receive both RF and optical signals. It will be understood that the transmit / receive element 122 can be configured to transmit and / or receive any combination of wireless signals.

[0063] Although the transmit / receive element 122 is depicted as a single element in Figure 1B the WTRU 102 can include any number of transmit / receive elements 122. More specifically, the WTRU 102 can employ MIMO technology. Thus, in one embodiment, the WTRU 102 can include two or more transmit / receive elements 122 (such as multiple antennas) for transmitting and receiving wireless signals via the air interface 116.

[0064] The transceiver 120 can be configured to modulate the signals to be transmitted by the transmit / receive element 122 and demodulate the signals received by the transmit / receive element 122. As described above, the WTRU 102 can have multi-mode capabilities. Thus, the transceiver 120 can include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs (such as NR and IEEE 802.11).

[0065] The processor 118 of the WTRU 102 may be coupled to a speaker / microphone 124, a keyboard 126, and / or a display / touchpad 128 (such as a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit), and may receive user input data from these components. The processor 118 may also output user data to the speaker / microphone 124, the keyboard 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from any type of suitable memory (such as non-removable memory 130 and / or removable memory 132), and store data into these memories. The non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and so on. In other embodiments, the processor 118 may access information from a memory that is not physically located on the WTRU 102 (such as on a server or a home computer (not shown)), and store data into these memories.

[0066] The processor 118 may receive power from a power supply 134, and may be configured to distribute and / or control the power to other components in the WTRU 102. The power supply 134 may be any suitable device for powering the WTRU 102. For example, the power supply 134 may include one or more dry batteries (such as nickel cadmium (NiCd), nickel zinc (NiZn), nickel metal hydride (NiMH), lithium ion (Li-ion), etc.), a solar cell, a fuel cell, and so on.

[0067] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (such as longitude and latitude) related to the current location of the WTRU 102. As a supplement or replacement to the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (such as base stations 114a, 114b) via an 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 understood that the WTRU 102 may obtain location information by any suitable location determination method while remaining consistent with the embodiments.

[0068] The processor 118 may also be coupled to other peripheral devices 138, which may include one or more software and / or hardware modules that provide additional features, functions, and / or wired or wireless connections. For example, the peripheral devices 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, Modules, FM radio units, digital music players, media players, video game console modules, Internet browsers, virtual reality and / or augmented reality (VR / AR) devices, activity trackers, etc. The peripheral device 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.

[0069] The WTRU 102 may include a full-duplex radio for which the transmission and reception of some or all signals (e.g., associated with a specific subframe for both UL (e.g., for transmission) and DL (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit to reduce and / or substantially eliminate self-interference via hardware (e.g., a choke) or via signal processing of a processor (e.g., a separate processor (not shown) or via the processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio for which the transmission and reception of some or all signals (e.g., associated with a specific subframe for UL (e.g., for transmission) or DL (e.g., for reception)).

[0070] Figure 1C is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As described above, the RAN 104 may employ E-UTRA radio technology to communicate with the WTRU 102a, 102b, 102c via the air interface 116. The RAN 104 may also communicate with the CN 106.

[0071] The RAN 104 may include eNode-Bs 160a, 160b, 160c, although it will be understood that the RAN 104 may include any number of eNode-Bs while remaining consistent with the embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRU 102a, 102b, 102c via the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, for example, the eNode-B 160a may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0072] Each of eNode-Bs 160a, 160b, and 160c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, etc. As Figure 1C shown, eNode-Bs 160a, 160b, and / or 160c may communicate with each other via the X2 interface.

[0073] Figure 1C The illustrated CN 106 may include a Mobility Management Entity (MME) 162, a Serving Gateway (SGW) 164, and a Packet Data Network (PDN) Gateway (PGW) 166. Although the above elements are depicted as part of 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.

[0074] MME 162 may be connected to each of eNode-Bs 162a, 162b, 162c in RAN 104 via the S1 interface and may act as a control node. For example, MME 162 may be responsible for authenticating users of WTRUs 102a, 102b, 102c, activation / deactivation of bearers, selection of a specific serving gateway during the initial attachment of WTRUs 102a, 102b, 102c, etc. MME 162 may provide control plane functions for handover between RAN 104 and other RANs (not shown) employing other radio technologies such as GSM and / or WCDMA.

[0075] SGW 164 may be connected to each of eNode Bs 160a, 160b, and / or 160c in RAN 104 via the S1 interface. SGW 164 may generally route and forward user data packets to / from WTRUs 102a, 102b, 102c. SGW 164 may perform other functions such as anchoring the user plane during handover between eNode Bs, triggering paging when DL data is available for WTRUs 102a, 102b, 102c, managing and storing the context of WTRUs 102a, 102b, 102c, etc.

[0076] SGW 164 may be connected to PGW 166, which may provide access for WTRUs 102a, 102b, and / or 102c to a packet switched network (such as Internet 110) to facilitate communication between WTRUs 102a, 102b, and / or 102c and IP-enabled devices.

[0077] CN 106 can facilitate communication with other networks. For example, CN 106 can provide the WTRUs 102a, 102b, and / or 102c with access to a circuit-switched network (such as the PSTN 108), thereby facilitating communication between the WTRUs 102a, 102b, and / or 102c and traditional landline communication devices. For example, CN 106 can include or communicate with an IP gateway (such as an IP Multimedia Subsystem (IMS) server) that acts as an interface between CN 106 and the PSTN 108. In addition, CN 106 can provide the WTRUs 102a, 102b, and / or 102c with access to other networks 112, which can include other wired and / or wireless networks owned and / or operated by other service providers.

[0078] Although the WTRU is described in Figures 1A - 1D as a wireless terminal, it is contemplated that in some representative embodiments, such a terminal can use a wired communication interface (such as temporary or permanent) with the communication network.

[0079] In a representative embodiment, the other network 112 can be a WLAN.

[0080] A WLAN in an infrastructure basic service set (BSS) mode can have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP can 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 going to an STA from outside the BSS can reach the AP and can be delivered to the STA. Traffic from an STA going to a destination outside the BSS can be transmitted to the AP to be delivered to the corresponding destination. Traffic between STAs within the BSS can be transmitted through the AP. For example, where the source STA can transmit traffic to the AP, and the AP can deliver the traffic to the destination STA. Traffic between STAs within the BSS can be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic can be transmitted directly or indirectly between the source STA and the destination STA using direct link setup (DLS). In some representative embodiments, the DLS can use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode can not have an AP, and STAs within the IBSS or using the IBSS (such as all STAs) can communicate directly with each other. The IBSS communication mode can sometimes be referred to in this document as an "ad-hoc" communication mode.

[0081] When operating in 802.11ac infrastructure mode or a similar operating mode, the AP can send beacons on a fixed channel (e.g., the primary channel). The primary channel can be of a fixed width (e.g., a bandwidth of 20 MHz wide) or dynamically set width. The primary channel can be the operating channel of the BSS and can be used by the STA to establish a connection with the AP. In some representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) can be implemented, for example, in an 802.11 system. For CSMA / CA, the STA including the AP (e.g., each STA) can sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, that particular STA can back off. Only one STA (e.g., only one station) can transmit at any given time in a given BSS.

[0082] High Throughput (HT) STAs can communicate using a channel with a width of 40 MHz, for example, by combining the primary 20 MHz channel with an adjacent or non - adjacent 20 MHz channel to form a 40 MHz wide channel.

[0083] Very High Throughput (VHT) STAs can support channels with widths of 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz. The 40 MHz and / or 80 MHz channels can be formed by combining consecutive 20 MHz channels. The 160 MHz channel can be formed by combining eight consecutive 20 MHz channels or by combining two non - consecutive 80 MHz channels, which can be referred to as an 80 + 80 configuration. For the 80 + 80 configuration, the data after channel coding can be fed through a segment parser that can divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing and time - domain processing can be performed on each stream separately. The streams can be mapped to two 80 MHz channels, and the data can be sent by the transmitting STA. At the receiver of the receiving STA, the above operations for the 80 + 80 configuration can be reversed, and the combined data can be transferred to the Media Access Control (MAC).

[0084] The sub-1GHz operation mode is supported by 802.11af and 802.11ah. Compared with the channel operation bandwidth and carrier used in 802.11n and 802.11ac, the channel operation bandwidth and carrier in 802.11af and 802.11ah are reduced. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV white space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah can support meter type control / machine type communication (MTC), such as MTC devices in a macro coverage area. The MTC device can have certain capabilities, such as including restricted capabilities that support (e.g., only support) certain and / or restricted bandwidths. The MTC device can include a battery having a battery life higher than a threshold (e.g., to maintain a very long battery life).

[0085] WLAN systems (such as 802.11n, 802.11ac, 802.11af, and 802.11ah) that can support multiple channels and channel bandwidths include channels that can be designated as the primary channel. The primary channel can have a bandwidth equal to the maximum common operation bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be set and / or restricted by the STA that supports the minimum bandwidth operation mode among all STAs operating in the BSS. In the example of 802.11ah, for an STA that supports (e.g., only supports) the 1MHz mode (e.g., an MTC type device), the primary channel can be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operation modes. Carrier sensing and / or network allocation vector (NAV) settings can depend on the status of the primary channel. If the primary channel (e.g., due to an STA (which only supports the 1MHz operation mode) transmitting to the AP) is busy, then all available frequency bands can be considered busy even if most of the available frequency bands remain idle.

[0086] In the United States, the available frequency band for 802.11ah is from 902MHz to 928MHz. In Korea, the available frequency band is from 917.5MHz to 923.5MHz. In Japan, the available frequency band is from 916.5MHz to 927.5MHz. Depending on the country code, the total available bandwidth for 802.11ah is 6MHz to 26MHz.

[0087] Figure 1DFIG. 0 illustrates a system diagram of RAN 104 and CN 106 according to an embodiment. As described above, RAN 104 may communicate with WTRUs 102a, 102b, and / or 102c via air interface 116 using NR radio technology. RAN 104 may also communicate with CN 106.

[0088] RAN 104 may include gNBs 180a, 180b, and / or 180c, but it will be understood that RAN 104 may include any number of gNBs while remaining consistent with the embodiment. Each of gNBs 180a, 180b, and / or 180c may include one or more transceivers for communicating with WTRUs 102a, 102b, and / or 102c via air interface 116. In one embodiment, gNBs 180a, 180b, and / or 180c may implement MIMO technology. For example, gNB 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from gNBs 180a, 180b, and / or 180c. Thus, for example, gNB 180a may use multiple antennas to transmit wireless signals to and / or receive wireless signals from WTRU 102a. In an embodiment, gNBs 180a, 180b, and / or 180c may implement carrier aggregation technology. For example, gNB 180a may transmit multiple component carriers (not shown) to WTRU 102a. A subset of these component carriers may be on unlicensed spectrum, while the remaining component carriers may be on licensed spectrum. In an embodiment, gNBs 180a, 180b, and / or 180c may implement coordinated multi-point (CoMP) technology. For example, WTRU 102a may receive a coordinated transmission from gNB 180a and gNB 180b (and / or gNB 180c).

[0089] WTRUs 102a, 102b, and / or 102c may communicate with gNBs 180a, 180b, and / or 180c using a transmission associated with a scalable numerology. For example, the OFDM symbol interval and / or the OFDM subcarrier spacing may vary according to different transmissions, different cells, and / or different parts of the radio transmission spectrum. WTRUs 102a, 102b, and / or 102c may communicate with gNBs 180a, 180b, and / or 180c using subframes or transmission time intervals (TTIs) of various or scalable lengths (e.g., including a varying number of OFDM symbols and / or an absolute time of continuously varying length).

[0090] gNBs 180a, 180b, and / or 180c may be configured to communicate with WTRUs 102a, 102b, and / or 102c in stand-alone configuration and / or non-stand-alone configuration. In stand-alone configuration, WTRUs 102a, 102b, and / or 102c may communicate with gNBs 180a, 180b, 180c without accessing another RAN (e.g., eNode-Bs 160a, 160b, 160c). In stand-alone configuration, WTRUs 102a, 102b, and / or 102c may utilize one or more of gNBs 180a, 180b, and / or 180c as a mobility anchor. In stand-alone configuration, WTRUs 102a, 102b, and / or 102c may communicate with gNBs 180a, 180b, and / or 180c using signals in an unlicensed band. In non-stand-alone configuration, WTRUs 102a, 102b, and / or 102c may communicate / connect with gNBs 180a, 180b, and / or 180c while also communicating / connecting with another RAN (e.g., eNode-Bs 160a, 160b, and / or 160c). For example, WTRUs 102a, 102b, and / or 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, and / or 180c and one or more eNode-Bs 160a, 160b, and / or 160c substantially simultaneously. In non-stand-alone configuration, eNode-Bs 160a, 160b, and / or 160c may act as a mobility anchor for WTRUs 102a, 102b, and / or 102c, and gNBs 180a, 180b, and / or 180c may provide additional coverage and / or throughput for serving WTRUs 102a, 102b, and / or 102c.

[0091] Each of gNBs 180a, 180b, and / or 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, support for network slicing, DC, interworking between NR and E-UTRA, routing of user plane data to user plane functions (UPFs) 184a and / or 184b, routing of control plane information to access and mobility management functions (AMFs) 182a and / or 182b, etc. As Figure 1D shown, gNBs 180a, 180b, and / or 180c may communicate with each other via the Xn interface.

[0092] Figure 1DThe illustrated CN 106 may include at least one AMF 182a and / or 182b, at least one UPF 184a and / or 184b, at least one session management function (SMF) 183a and / or 183b, and may include data network (DN) 185a and / or 185b. Although the foregoing elements are depicted as part of 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.

[0093] AMF 182a and / or 182b may be connected via the N2 interface to one or more of gNBs 180a, 180b, and / or 180c in RAN 104 and may act as a control node. For example, AMF 182a and / or 182b may be responsible for authenticating users of WTRUs 102a, 102b, and / or 102c, supporting network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selecting a particular SMF 183a and / or 183b, managing the registration area, terminating non-access stratum (NAS) signaling, mobility management, etc. AMF 182a and / or 182b may use network slicing in order to customize the CN support for WTRUs 102a, 102b, and / or 102c based on the type of service utilized by WTRUs 102a, 102b, and / or 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low-latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, etc. AMF 182a and / or 182b may provide control plane functions for handover between RAN 104 and other RANs ( Figure 1A — Figure 1D not shown in figure) employing other radio technologies (e.g., LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi).

[0094] SMF 183a and / or 183b may be connected via the N11 interface to AMF 182a and / or 182b in CN 106. SMF 183a and / or 183b may also be connected via the N4 interface to UPF 184a and / or 184b in CN 106. SMF 183a and / or 183b may select and control UPF 184a and / or 184b and configure the routing of traffic through UPF 184a and / or 184b. SMF 183a and / or 183b may perform other functions, such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0095] UPF 184a and / or 184b may be connected to one or more of gNBs 180a, 180b, and / or 180c in RAN 104 via the N3 interface, and the N3 interface may provide access to a packet switched network (such as the Internet 110) for WTRU 102a, 102b, and / or 102c to facilitate communication between WTRU 102a, 102b, and / or 102c and IP-enabled devices. UPF 184 and / or 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.

[0096] CN 106 may facilitate communication with other networks. For example, CN 106 may include or communicate with an IP gateway (such as an IP Multimedia Subsystem (IMS) server) that serves as an interface between CN 106 and the PSTN 108. Additionally, CN 106 may provide access to other networks 112 for WTRU 102a, 102b, and / or 102c, and the other networks 112 may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, WTRU 102a, 102b, and / or 102c may be connected to local DNs 185a and / or 185b via the N3 interface to UPF 184a and / or 184b and the N6 interface between UPF 184a and / or 184b and DNs 185a and / or 185b through UPF 184a and / or 184b.

[0097] In view of Figure 1A — Figure 1D and Figure 1A — Figure 1D the corresponding descriptions, one or more or all of the functions related to one or more of the following descriptions herein may be performed by one or more emulation devices (not shown): WTRU 102a - 102d, base stations 114a - 114b, eNode-Bs 160a - 160c, MME 162, SGW 164, PGW 166, gNBs 180a - 180c, AMF 182a - 182b, UPF 184a - 184b, SMF 183a - 183b, DNs 185a - 185b, and / or any other (one or more) devices described herein. The emulation device(s) may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation device(s) may be used to test other devices and / or simulate network and / or WTRU functions.

[0098] The simulation device can be designed to perform one or more tests on other devices in a laboratory environment and / or an operator network environment. For example, one or more simulation devices can perform one or more or all functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. One or more simulation devices can perform one or more or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device can be directly coupled to another device for testing and / or performing tests using over-the-air wireless communication.

[0099] One or more simulation devices can perform one or more (including all) functions while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test laboratory and / or in a test scenario in a non-deployed (e.g., test) wired and / or wireless communication network to perform tests on one or more components. One or more simulation devices can be test devices. The simulation device can send and / or receive data using direct RF coupling and / or wireless communication via an RF circuit (e.g., which can include one or more antennas).

[0100] Abbreviations and Acronyms

[0101] 3GPP Third Generation Partnership Project

[0102] 4G Fourth Generation

[0103] 5G Fifth Generation

[0104] AWGN Additive White Gaussian Noise

[0105] BER Bit Error Rate

[0106] BLER Block Error Rate

[0107] CA Carrier Aggregation

[0108] CBM Common Beam Management

[0109] CC Component Carrier

[0110] CP-OFDM Cyclic Prefix Orthogonal Frequency Division Multiplexing

[0111] CSI Channel State Information

[0112] CSI-RS Channel State Information Reference Signal

[0113] DC Direct Current

[0114] DCI Downlink Control Information

[0115] DCT Discrete Cosine Transform

[0116] DFE Decision Feedback Equalizer

[0117] DFT Discrete Fourier Transform

[0118] DFT-s-OFDM Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing

[0119] DL Downlink

[0120] DLCT Discrete Linear Chirp Transform

[0121] DM-RS Demodulation Reference Signal

[0122] DST Discrete Sine Transform

[0123] DWHT Discrete Walsh-Hadamard Transform

[0124] DWT Discrete Wavelet Transform

[0125] EIRP Effective Isotropic Radiated Power

[0126] EIS Effective Isotropic Sensitivity

[0127] FR1 Frequency Range 1

[0128] FR2-1 Frequency Range 2-1

[0129] GSFBC Generalized Space-Frequency Block Coding

[0130] IBM Independent Beam Management

[0131] ICI Inter-Carrier Interference

[0132] LMMSE Linear Minimum Mean Square Error

[0133] LTE Long Term Evolution

[0134] MAC CE Medium Access Control - Control Element

[0135] MIMO Multiple-Input Multiple-Output

[0136] MU-MIMO Multi-User Multiple-Input Multiple-Output

[0137] NR New Radio

[0138] OFDM Orthogonal Frequency Division Multiplexing

[0139] PA Power Amplifier

[0140] PDCCH Physical Downlink Control Channel

[0141] Physical Downlink Shared Channel (PDSCH)

[0142] Primary Synchronization Signal (PSS)

[0143] Phase Tracking Reference Signal (PT-RS)

[0144] Physical Uplink Shared Channel (PUSCH)

[0145] Quasi-Co-Location (QCL)

[0146] Resource Block (RB)

[0147] Radio Frequency (RF)

[0148] Radio Resource Control (RRC)

[0149] Spatial Frequency Block Coding (SFBC)

[0150] Signal-to-Noise Ratio (SNR)

[0151] Secondary Synchronization Signal (SSS)

[0152] Single-User Multiple-Input Multiple-Output (SU-MIMO)

[0153] Transmit-Receive Point (TRP)

[0154] Transmitter-Receiver (TRX)

[0155] Transmission Time Interval (TTI)

[0156] Transmitter (TX)

[0157] User Equipment (UE)

[0158] Uniform Planar Array (UPA)

[0159] Universal Mobile Telecommunications System (UMTS)

[0160] Wireless Transmit / Receive Unit (WTRU)

[0161] One or more embodiments relate to the field of wireless communications and, more particularly, to methods and processes for improving link robustness in high-frequency systems, where communication is achieved by means of transmit and receive beams generated by beamforming.

[0162] Regarding hybrid beamforming, the 5th generation (5G) NR standard already supports the so-called millimeter wave (mmWave) radio frequencies, i.e., frequencies above 6 GHz characterized by large chunks of spectrum potentially available for wireless communication. The so-called frequency range 2-1 (FR2-1) includes the mmWave radio spectrum between 24.25 GHz and 52.6 GHz in the existing specifications. Additionally, the frequency range 2-2 (FR2-2) includes the mmWave radio spectrum between 52.6 GHz and 71 GHz. At these frequencies, radio propagation can be more stringent than at lower frequencies due to the higher propagation losses caused by the lower effective antenna aperture in a single-antenna system. To compensate for this higher propagation loss, multi-antenna structures are often used on both the transmitter side and the receiver side to implement beamforming to increase signal gain.

[0163] At very high frequencies, the wavelength can be very small (millimeter scale) such that the number of antennas required to overcome the stringent link budget is very large (e.g., often 512, 1024, or even more), thus making it challenging to implement as many TRX chains as required in a full-digital beamforming architecture. This is why hybrid beamforming is widely adopted in FR2-1, where a smaller number of TRX chains (e.g., 2 or 4) use phase shifters in, for example, an RF lens or on / off switching of antennas to excite a larger number of antenna elements (e.g., on the order of 1024 or more). Hybrid beamforming facilitates reducing the complexity of transceiver design but may come at the cost of reduced flexibility in spatial multiplexing. Each of the TRX chains can generate a single beam towards a spatial direction as determined by the phase shifters. Digital precoding of the beams is further performed to spatially multiplex the beams towards different users. However, it may not be possible to digitally precode the signals of individual antenna elements as in a digital beamforming architecture.

[0164] Figure 2 It is a diagram of a hybrid beamforming circuit 200 with a hybrid beamforming architecture according to an embodiment.

[0165] Reference Figure 2 , the baseband digital beamforming stage 202 provides corresponding data streams to the corresponding RF chains 2021 - 202 of the RF chain stage 204, and the RF chains drive the analog beamforming stage 206, and the analog beamforming stage 206 includes analog RF beamformers 2081 - 208 n . The analog beamforming stage 206 uses, for example, as many phase shifters and / or on / off switches 210 (2101 - 210 shown in n ) as the number of antenna elements 2121 - 212 of the antenna 214 multiplied by the number of TRX chains to steer the beam ( n ) in a way that... Figure 2 shown as 2101 - 210 in n )Figure 2 The desired direction in the steering space (not shown in [])). It may not be possible to control the amplitude and phase of the signals at the antenna elements individually, but rather, often under the limitation of having a discrete beam grid, only the relative phase introduced by the phase shifters is controlled to steer the beam, where each beam has a predefined set of phase shifts. In addition, traditional phase shifters have a narrowband response and can only apply a constant phase shift across the entire frequency. Other architectures employ an RF lens for the analog beamforming stage 206 ( Figure 2 not shown in []), where the lens exhibits some frequency dependence on the dielectric constant of the material from which the lens is made.

[0166] One of the potential drawbacks of hybrid beamforming is that the beams cannot be separated in the frequency domain to simultaneously point in different directions in space (e.g., to address different users or spatially multiplex different layers to a given user), because the phase shifters (or switches in the RF lens) apply the beam direction across the entire carrier (e.g., across all subcarriers of an OFDM symbol or a DFT-s-OFDM symbol). In the following, for the purpose of explanation, beams having a single main lobe in a certain direction are mainly considered (ideally achieved in the absence of impairments with one set of phase shifts) to obtain the highest beamforming gain. Thus, one set of phase shifts can be used at a time to achieve beamforming transmission, and transmissions to different devices located in different directions relative to the base station are thus separated in the time domain or the spatial domain, rather than in the frequency domain. Similarly, one set of phase shifts can be used at a time to achieve beams on the receiving side. However, implementing beamforming transmissions and beams in this way on the receiving side may limit the flexibility of the scheduler that divides resources in the time domain, frequency domain, and spatial domain to multiplex users.

[0167] Regarding beam management issues at very high frequencies, 5G NR Release 15 has standardized an integrated framework for beam management. Beam management is responsible for initially setting up a pair of transmit - receive beams, refining them during communication to improve signal quality, detecting beam failures, and successfully recovering from these failures. Broadly speaking, beam management is based on the tracking and reporting of the quality of the beams measured by the receiver side over a set of predefined resource elements (such as channel state information reference signals (CSI - RS) in 4G and 5G), such that the best beam pair is selected throughout the communication (e.g., always selected). This beam management process involves some control signaling, the overhead of which increases with the rate of change of the selected beam pair.

[0168] There are multiple reasons for performing beam changes throughout a communication. One reason is mobility, i.e., the movement of a device (e.g., a WTRU) relative to the line-of-sight direction towards a base station. Even in the absence of net user movement, rotational mobility of the device can result in frequent beam changes (e.g., as caused by slight rotation of a handheld device, sensor, or other connected device in an industrial-like environment). In these cases, as a result of continuously sensing the channel and reporting its quality, the beam management process can trigger frequent beam changes. However, CSI measurements can be impaired by noise or other deficiencies that may cause errors in the beam selection process, and CSI measurements can suffer from channel aging when the channel measured at the time of reporting the CSI is different from the channel experienced at the transmission moment. Thus, the selected beam pair may not be the optimal beam pair, and subsequent channel measurements may trigger further beam reselection with corresponding additional signaling overhead. This problem is more pronounced at very high frequencies because narrower beams are used to overcome excessive path loss.

[0169] At very high frequencies, one of the most severe impairments when dealing with wide bandwidths is the so-called frequency-wideband effect, also known as beam squint, through which the orientation of a beam deviates from its ideal value by an amount that increases with the distance of the beam frequency from the carrier frequency. Beam squint is caused by the narrowband characteristics of the phase shifters and / or the frequency-dependent dielectric constant of the RF lenses, which can be responsible for steering the beam in a hybrid beamforming architecture. This effect is more pronounced when the fractional bandwidth of the signal (i.e., the bandwidth divided by the center frequency) is large. When the fractional bandwidth is only 10%, beam squint can result in an array gain loss of up to 5 - 6 dB, which is a loss figure that can easily be exceeded in these bands due to the potentially large available bandwidths in the THz and sub-THz frequencies.

[0170] The magnitude of the beam squint effect depends on the frequency distance of the beam from the carrier frequency and the number of transmit and / or receive antennas. Since the number of antennas in a transmit / receive entity is typically an implementation feature that is not signaled to other peers, it is sometimes impossible to predict the severity of beam squint until its impact is measured at the receiver side. Similarly, the problems caused by beam misalignment are ultimately determined by the number of antennas at both the transmit side and the receive side, and are typically not predictable by the transmitter until the beam misalignment (or one or more parameters indicating beam misalignment) is measured by the receiver.

[0171] Figure 3 is a diagram of beam separation for pre-compensating beam squint respectively according to an embodiment, where two beams each carry half of the subcarriers.

[0172] Reference Figure 3, examples for mitigating beam skew can involve splitting a transmit beam into two or more beams (e.g., two beams 3001 and 3002), each beam including a subset of the allocated subcarriers (e.g., two subsets 3021 and 3022) and pointing in different directions to pre-compensate for the average deviation caused in each frequency region. As an example, a user can be addressed by a pair of beams 3001 and 3002, each beam 3001 and 3002 being directed in slightly different predefined directions, and each beam 3001 and 3002 allocating half of the subcarriers for that user. Depending on the maximum allowed magnitude of the beam skew, more beams can be used.

[0173] Although this technique effectively halves the maximum frequency distance (and thus, the maximum severity of the beam skew) in each of the beams 3001 and 3002, it may not mitigate the loss caused by beam misalignment, since such misalignment can equally affect all beams regardless of their orientation.

[0174] Regarding Alamouti-based diversity, in conventional implementations and in the so-called frequency range 1 (FR1, below 7.125 GHz), transmit diversity schemes based on Alamouti space-time decoding have been widely used to enhance the reliability of detection. A variant of the Alamouti scheme involving space-frequency block coding (SFBC) is used in the 3GPP Long-Term Evolution (LTE) standard. This type of coding produces a diversity order of two (2) while maintaining the same symbol rate of the communication, i.e., without increasing the bit rate. Alamouti space-time decoding has also been considered in the Universal Mobile Telecommunications System (UMTS) and its evolutions. The 5G NR standard does not explicitly consider transmit diversity, but any vendor-specific implementation that is transparent to the device can be used to improve the detection reliability, such as, for example, cyclic precoding or antenna switching schemes.

[0175] Regarding common and independent beam management in 3GPP, 3GPP engineers and other developers studied the impact of the beam squint effect in the FR2 scenario. When adopting the common beam management (CBM) scheme, the radiation degradation caused by beam squint is more obvious in inter-band and intra-band carrier aggregation (CA). In CBM, the WTRU selects its DL receive beam for all CCs in all configured bands based on DL measurements performed in the only component carrier (CC) configured with the reference signal for beam management. Therefore, when beam squint occurs due to a large frequency separation between CCs, it may have an impact on performance, and NR allows relaxing the effective isotropic sensitivity (EIS) of some CCs. In contrast, the WTRU supporting inter-band CA with independent beam management (IBM) selects its (one or more) DL receive beam for all CCs in each configured band based on DL reference signal measurements performed in that band. Therefore, according to the smaller frequency separation between frequency edges compared to CBM, the measurements in that band can result in a reduced impact from beam squint.

[0176] 3GPP engineers and other developers evaluated the beam squint effect in the FR2 inter-band DL CA scenario and further studied its impact on EIS and effective isotropic radiated power (EIRP) in compliance testing. However, operation at sub-THz and THz frequencies may be impaired even without inter-band CA if the bandwidth allocation is large enough to introduce significant degradation. IBM can mitigate the problem in this case by performing independent beam management of two beams in possibly different directions, but this mitigation may not be efficient as it can significantly increase the associated control signaling from the additional receive beams set by the WTRU.

[0177] When there is significant translational mobility, rotational mobility, or beam squint, conventional beam management techniques based on tracking the best beam pair at the transmitter and receiver sides may cause additional beam reselection and signaling overhead. These problems are particularly severe at very high frequencies for at least the following reasons:

[0178] - Due to the narrowness of the beam and the higher impact from Doppler (which linearly increases with the carrier frequency), the channel aging caused by mobility or imperfections from CSI measurement / reporting may be particularly significant at very high frequencies.

[0179] - A WTRU and other transmitters / receivers may not be able to correct beam skew at the antenna-level digital ground at very high frequencies to compensate for beam deviation in a typical hybrid beamforming architecture that employs narrowband phase shifters or RF lenses with a frequency-dependent dielectric constant. Beam skew may result in SNR loss at subcarriers located farthest from the carrier frequency, and this SNR loss may result in a slanted frequency response even in a completely flat channel. Compared to the case without beam skew, these impaired subcarriers degrade the overall link quality, sometimes regardless of the modulation and coding scheme used, because the symbols no longer "see" the same channel response. As previously demonstrated, when CSI is only known at the receiver, performance can be improved if all symbols experience the same channel gain. Due to the uncertainty of the combined beam skew effects caused by the transmitter and receiver, and the unpredictability of any errors caused by channel aging, the transmitter may not be able to utilize the instantaneous CSI to improve detection. Under these conditions, it is known that performance is generally optimal when symbols experience the same channel gain in both the time domain and the frequency domain.

[0180] - When random misalignment occurs (e.g., from unpredictable rotations or defects during the beam selection process), it may be ineffective to use prior pre-compensation of the spatial orientation of the beam to separate the beams to mitigate beam skew. Robustness against beam misalignment may be particularly important at very high frequencies, where the beam is so narrow that even a deviation of only a few degrees, for example, can significantly degrade communication.

[0181] - Traditionally, Alamouti-based diversity schemes used to improve detection statistics under poor link conditions or when there is significant channel aging rely on the presence of uncorrelated transmit antennas with substantially independent channel responses. Traditional Alamouti schemes may require further processing (e.g., modification) before being applicable to beamforming systems at high frequencies. On the one hand, the same diversity beam as the main beam will not bring any advantages because the channel responses of the beams will be similar and thus will not result in any statistical gain: for example, a SNR gain of only 3 dB at the cost of 3 dB more power, with a zero net gain. On the other hand, a diversity beam pointing in a different direction from the main beam (and whose channel response is uncorrelated with that of the main beam) can improve the statistics of the signal, but is only feasible when there are reflections (e.g., multipath) to help the diversity beam reach the receiver (i.e., if the direction of the diversity beam is also a strong eigenvector of the system). This may be difficult in some line-of-sight scenarios where receive spatial filtering may significantly block most multipath components outside the receiver beamwidth. Additionally, the two beams may be subject to similar (and unpredictable) degradation from beam misalignment, which may render the diversity beam largely ineffective in such cases.

[0182] - Alamouti diversity may not be useful for overcoming beam squint because the SNR degradation at the farthest subcarriers also exists in the diversity beams, resulting in a skewed frequency response. It is well known that performance is improved and usually optimal when data symbols experience the same channel gain in the time domain or frequency domain for a given total SNR. This fact calls for the design of better mitigation methods to reduce the need for frequency selectivity of the channel caused by beam squint.

[0183] - Methods in 3GPP that consider independent beams to address beam squint mainly focus on the CA scenario, but may not be as efficient in non-CA scenarios with a single component carrier because of the increased signaling required to track two beams.

[0184] A better solution can thus improve link stability in a multi-antenna system based on, for example, hybrid beamforming or holographic beamforming (which is impaired by mobility, CSI imperfections, lack of accuracy in CSI measurements, and / or beam squint).

[0185] Embodiments of the methods and processes disclosed herein improve link stability in the presence of channel aging, impairments related to channel state acquisition or reporting, and / or beam squint effects in a multi-antenna system, e.g., using hybrid beamforming or holographic beamforming, but may also use other solutions such as digital beamforming, holographic beamforming, and other solutions capable of steering beams in desired directions in space.

[0186] The following techniques are described as part of one or more embodiments further described below.

[0187] Regarding generalized space-frequency block coding (GSFBC), according to one or more embodiments, decoding schemes (hereinafter denoted as GSFBC) suitable for dealing with the above-mentioned beam impairments are described.

[0188] Figure 4 FIG. is a diagram of a base station 400 and a device 402 connected by at least a pair of beams 4041 and 4042 according to an embodiment. The optimal beam pairs 406 a and 406 l are highlighted as part of a beam grid 408.

[0189] For example purposes, there are scenarios for the transmission and reception of wireless signals where both the transmitting entity 400 and the receiving entity 402 are capable of steering beams in different directions in space, as Figure 4As shown. Beamforming is assumed to compensate for the excessive losses caused by the propagation channel at very high frequencies (especially at sub-THz and THz). To this end, transmit and receive beam pairs are established at initial access and are further refined to periodically update the spatial orientations of each transmit beam and receive beam in the pair to obtain optimal performance. However, channel aging caused by user mobility and deficiencies in CSI acquisition or reporting may degrade the SNR and ultimately trigger further beam reselection. Beam squint (if any) may pose further challenges because individual beam reselections may not be able to mitigate the effects of frequency-dependent deviations of the beam from its ideal orientation.

[0190] To address this scenario, a generalized space-frequency block decoding (GSFBC) process is described, which may include a diversity beam and a space-frequency decoding process, and the space-frequency encoding process may generate complex symbols s (1) and s (2) , and these complex symbols will be transmitted simultaneously using two beams, with the main beam carrying s (1) , and the diversity beam carrying s (2) . The diversity beam and the generalized space-frequency decoding process are configured to mitigate the effects of beam misalignment (e.g., from channel aging or CSI deficiencies), beam squint, and / or any other unpredictable beam impairments that affect performance. In a scenario with multiple transmit-receive points (multi-TRP), the diversity beam may be transmitted by the same or different TRPs to enhance diversity. In an embodiment, as will be explained, the diversity beam or the space-frequency decoding process may be avoided depending on the impairments to be addressed and the characteristics of the transceiver nodes.

[0191] Corresponding transmit and receive processing steps for GSFBC are described according to an embodiment.

[0192] Assume a block of M complex modulated data symbols (where M is even),

[0193] x (1) ={x1,…,x M} Equation (1)

[0194] Throughout the description of this example, it is assumed that the symbols are mapped to appropriate frequency-domain subcarriers in CP-OFDM symbols, but the methods herein may equally apply to other waveforms, modulation techniques, and other multi-carrier / single-carrier waveforms.

[0195] Figure 5 is a schematic diagram of a transmit processing circuit (e.g., a transmit path or a transmit circuit) 500 configured according to an embodiment to implement the transmit processing steps for GSFBC encoding, and the GSFBC encoding includes transform spreading and the generation of a main beam and a diversity beam.

[0196] To increase beam resilience against potential impairments from mobility, beam squint effects, and / or other reasons, embodiments of a generalized space-frequency block decoding process involve transform expansion circuitry / steps and circuitry / methods for generating diversity beams to provide additional link resilience. Refer to Figure 5 , at least the (one or more) transmit processing circuitry / (one or more) steps highlighted in the cross-hatched boxes represent an improvement over the conventional process.

[0197] Still referring to Figure 5 , the serial-to-parallel converter 502 is configured to convert the modulated data symbol x of equation (1) (1) from serial form to parallel form.

[0198] The transform expansion circuit 504 is configured to apply an expansion transform (a transform function that expands the modulated data symbol x in frequency) to the parallel modulated data symbol x from the serial-to-parallel converter 502 (1) to generate an expanded modulated data symbol s according to the following equation (1) : (1) :

[0199]

[0200] The layer mapping circuit 506 is configured to map the expanded modulated data symbol s from the transform expansion circuit 504 (1) onto a first data stream of a first transmit beam and a second data stream of a second transmit beam (e.g., a diversity transmit beam or “diversity beam”). For example, the layer mapping circuit 506 may generate a first data stream equal to s (1) for modulating some or all (e.g., half) of the N available subcarriers in the first transmit beam, and may generate a second data stream equal to the complex conjugate of s (1) (s (2) ) for modulating some or all (e.g., the other half) of the N available subcarriers in the second beam.

[0201] The precoding circuit 508 is configured to precode the first mapped data stream of the expanded modulated data symbol s from the layer mapping circuit 506 (1) according to the following equation (Equation (2)), and precode the second mapped data stream of the expanded modulated conjugate data symbol s (2) :

[0202]

[0203] The resource mapping circuit 510 is configured to map resources to a first precoded data stream and a second precoded data stream (e.g., by allocating a first subset of subcarriers within N available subcarriers at a given frequency location to a precoded symbol of the first precoded data stream and a second subset of subcarriers within N available subcarriers at the same or a different frequency location to a precoded symbol of the second precoded data stream, where M ≤ N).

[0204] The RF beamformer circuit 512 includes a first RF beamformer 514a and a second (e.g., diversity) RF beamformer 514b. The first RF beamformer 514a and the second RF beamformer are configured to form a first transmit beam from a first resource mapped data stream generated by the resource mapping circuit 510 and to form a second (e.g., diversity) beam from a second resource mapped data stream generated by the resource mapping circuit.

[0205] The transmit antenna array 516 is configured to generate and transmit a first transmit beam and a second (e.g., diversity) beam (in the transmission medium) in response to the first and second formed beams from the RF beamformer 512.

[0206] Still referring Figure 5 , a receiver of a device (e.g., a base station gNB or a WTRU) that receives the first beam and the second (e.g., diversity) beam from the antenna array 516 can provide feedback to the GSFBC control module circuit 518 of the transmit circuit 500, which is typically located in another device (e.g., another WTRU or another gNB). The feedback can include one or more signal-related parameters such as channel state information, error rate, and / or SNR at the receiver. In response to the feedback, the control module circuit 518 is configured to control the transform spread circuit 504 to adjust the spread transform and / or is configured to control the RF beamforming circuit 512 to adjust one or more parameters (e.g., beam half-power width, beam direction, and / or subcarriers on each beam) to improve the quality of the (one or more) signals of the data-bearing symbols received (at the receiver).

[0207] Figure 6 is a diagram of a transmit processing circuit 600 configured to perform steps of GSFBC encoding including transform spreading and single-beam transmission according to an embodiment.

[0208] Referring Figure 6 , in an embodiment, the generalized space-frequency block decoding process involves a transform spreading step to provide additional resilience to the beam squint effect in single-beam transmission without additional diversity beams.

[0209] Still referring Figure 6, the serial-to-parallel converter 602 is configured to convert the modulated data symbol x of Equation (1) (1) from serial form to parallel form.

[0210] The transform expansion circuit 604 is configured to apply an expansion transform to the parallel modulated data symbol x from the serial-to-parallel converter 602 (1) to generate an expanded modulated data symbol s according to Equation (2) (1) .

[0211] The layer mapping circuit 606 is configured to map the expanded modulated data symbol s from the transform expansion circuit 504 (1) onto a single data stream for a single transmit beam.

[0212] The precoding circuit 608 is configured to still precode the single mapped data stream of the expanded modulated data symbol s (1) according to Equation (2).

[0213] The resource mapping circuit 610 is configured to map resources to the single precoded data stream, for example, by allocating a subset of subcarriers (e.g., from N available subcarriers) to the precoded symbols of the single precoded data stream at a given frequency location.

[0214] The RF beamformer circuit 612 includes an RF beamformer 614, which is configured to form a single transmit beam from the single resource-mapped data stream generated by the resource mapping circuit 610.

[0215] The transmit antenna array 616 is configured to generate (in the transmission medium) and transmit a single transmit beam in response to the single formed beam from the RF beamformer 612.

[0216] Still referring to Figure 6 , the receiver of a device (e.g., a base station gNB or a WTRU) that receives a single beam from the antenna array 616 can provide feedback to the GSFBC control module circuit 618 of the transmit circuit 600, which is typically located in another device (e.g., another WTRU or another gNB), where the feedback can include one or more signal-related parameters, such as channel state information, error rate, and / or SNR at the receiver. In response to this feedback, the control module circuit 618 is configured to control the transform expansion circuit 604 to adjust the expansion transform to improve the quality of the (one or more) signals carrying data symbols (at the receiver).

[0217] Figure 7FIG. 700 is a diagram of a transmit processing circuit configured to perform steps of GSFBC encoding, the steps of GSFBC encoding including transform spreading and transmission on two beams (e.g., a first main beam and a second diversity beam) pointing in different directions and each including a respective half of the subcarriers.

[0218] Referring Figure 7 , in yet another embodiment, a circuit and a method performed by the circuit involve separating a main beam into two beams pointing in different directions in space, and each beam including a respective half of the subcarriers allocated for transmission, and a transform spreading step for providing additional flexibility for beam skewing for the two beams.

[0219] Still referring Figure 7 , the serial - to - parallel converter 702 is configured to convert the modulated data symbol x of Equation (1) (1) from serial form to parallel form.

[0220] The transform spreading circuit 704 is configured to apply an extended transform to the parallel modulated data symbol x from the serial - to - parallel converter 702 (1) to generate an extended modulated data symbol s according to Equation (2) (1) .

[0221] The layer mapping circuit 706 is configured to map the extended modulated data symbol s from the transform spreading circuit 504 (1) onto data streams for a first transmit beam (e.g., a main transmit beam) and for a second transmit beam (e.g., a diversity transmit beam or “diversity beam”).

[0222] The precoding circuit 708 is configured to precode (Equation (2)) the mapped data stream of the extended modulated data symbol s (1) .

[0223] The resource mapping circuit 710 is configured to map the extended and precoded modulated data symbol to N subcarriers according to the following equations:

[0224] s (2) ={s1, s2,..., s M / 2 , 0, …, 0} Equation (4)

[0225] s (3) ={0,..., 0, s M / 2+1 , …, s M} Equation (5)

[0226] where “0” represents an empty subcarrier, i.e., a subcarrier to which no extended and precoded modulated data symbol s n is mapped.

[0227] The RF beamformer circuit 712 includes a first RF beamformer 714a and a second (e.g., diversity) RF beamformer 714b. The first RF beamformer 714a and the second RF beamformer 714b are configured to form a first transmit (e.g., primary) beam from a first resource-mapped data stream on the first half of N subcarriers of a first transmit beam generated by the resource mapping circuit 710, and to form a second transmit (e.g., diversity) beam from a second resource-mapped data stream on the second half of N subcarriers of a second transmit beam generated by the resource mapping circuit. Each of the RF beamformers 714a and 714b generates a first and a second set of signals (which may be referred to as "sub-signals") to be transmitted by elements N of the transmit antenna array 716 x、y of the first and second signals sets (which may be referred to as "sub-signals") to be transmitted by the transmit antenna array 716.

[0228] The transmit antenna array 716 is configured to generate (in the transmission medium) and transmit a first transmit (e.g., primary) beam and a second transmit (e.g., diversity) beam in response to the first and second sets of signals from the RF beamformer circuit 712.

[0229] Still referring to Figure 7 , a receiver of a device (e.g., a base station gNB or a WTRU) that receives the first beam and the second (e.g., diversity) beam from the antenna array 716 can provide feedback to the GSFBC control module circuit 718 of the transmit circuit 700, which is typically located in another device (e.g., another WTRU or another gNB). The feedback can include one or more signal-related parameters such as channel state information, error rate, and / or SNR at the receiver. In response to the feedback, the control module circuit 718 is configured to control the transform spread circuit 704 to adjust the spread transform to improve the quality of the (one or more) signals carrying data symbols received (at the receiver).

[0230] Figure 8 is a diagram of a transmit processing circuit 800 configured to perform transmit processing steps for GSFBC coding, the steps of GSFBC coding including generating a primary beam and a diversity beam.

[0231] Referring to Figure 8 , in yet another embodiment, a method involves generating a diversity beam without a transform spread step to improve resilience against beam misalignment and other impairments not caused by beam squint.

[0232] Still referring to Figure 8 , the serial-to-parallel converter 802 is configured to convert the modulated data symbol x of equation (1) (1) from serial form to parallel form.

[0233] The layer mapping circuit 806 is configured to map the modulated data symbols x from the serial-to-parallel converter 802 (1) onto a first data stream of a first transmit beam and a second data stream of a second transmit beam (e.g., a diversity transmit beam or “diversity beam”).

[0234] The precoding circuit 808 is configured to precode the first mapped data stream of the modulated data symbols x from the layer mapping circuit 806 (1) according to the following equation (Equation (1)), and to precode the second mapped data stream of the modulated conjugate data symbols x (2) :

[0235] x (1) = {x1, …, x M} Equation (6)

[0236]

[0237] The resource mapping circuit 810 is configured to map resources to the first precoded data stream and the second precoded data stream, and to map the first and second precoded data streams onto N subcarriers by allocating a first set of N subcarriers to the precoded symbols of the first precoded data stream at a given frequency location, and by allocating a second set of N subcarriers to the precoded symbols of the second precoded data stream at the same or a different frequency location.

[0238] The RF beamformer circuit 812 includes a first (e.g., main) RF beamformer 814a and a second (e.g., diversity) RF beamformer 814b, the first RF beamformer 814a and the second RF beamformer 814b being configured to form a first (e.g., main) transmit beam from the first resource mapped data stream generated by the resource mapping circuit 810, and to form a second (e.g., diversity) transmit beam from the second resource mapped data stream generated by the resource mapping circuit. Each of the RF beamformers 814a and 814b generates a first and a second set of signals (which may be referred to as “sub-signals”) to be transmitted by the antenna elements N of the transmit antenna array 816 x、y .

[0239] The transmit antenna array 816 is configured to generate and transmit a first (e.g., main) transmit beam and a second (e.g., diversity) transmit beam (in the transmission medium) in response to the first and second formed beams from the RF beamformer 812.

[0240] Still referring to Figure 8, a receiver of a device (e.g., a base station gNB or a WTRU) that receives a first (e.g., primary) beam and a second (e.g., diversity) beam from an antenna array 816 can provide feedback to a GSFBC control module circuit 818 of a transmission circuit 800, which is typically located in another device (e.g., another WTRU or another gNB), where the feedback can include one or more signal-related parameters such as channel state information, error rate, and / or SNR at the receiver. In response to the feedback, the control module circuit 818 is configured to control an RF beamforming circuit 812 to adjust one or more parameters (e.g., beam half-power width, beam direction, and / or subcarriers on each beam) to improve the quality of the (one or more) signals carrying data symbols received (at the receiver).

[0241] Reference Figures 3 - 8 , without loss of generality, the channel responses of the beams involved in the example are respectively represented by and as a function of subcarrier index k = 1,…,M. In some examples, the primary (first) beam is generated according to a conventional beam management process, and the second beam is a diversity beam for improving resilience. In other examples, both the primary beam and the second beam are the result of splitting a beam into two beams, each beam pointing in a different direction in space and including a corresponding subset of subcarriers assigned to the user to reduce beam squint.

[0242] Embodiments of the methods disclosed herein can be described by a combination of several processing steps explained below, and the detailed steps for generating a PDSCH channel in 5G NR are described below. The following examples assume the absence of SU-MIMO or MU-MIMO, but the description can be directly extended to incorporate these MIMO techniques:

[0243] 1. Transform spreading (e.g., performed by a transform spreading circuit): This step (and / or circuit) applies a discrete transform operator to complex modulated data symbols such that it effectively spreads the symbols in the frequency domain. The data symbols correspond to complex constellation symbols that convey user data mapped to points in the complex plane according to a given constellation and modulation order (e.g., QPSK, M-QAM, etc.). The transform spreading operation aims to cancel frequency variations caused by beam squint and / or other beam impairments by averaging so that the data symbols experience a roughly constant channel gain in frequency, producing a constant effective channel response for the transformed data symbols when there is significant uncertainty in the CSI during transmission, which provides additional robustness against unpredictable impairments that may cause frequency-dependent signal degradation. The output of this step (circuit) can be written as:

[0244]

[0245] Examples of suitable transform spreading operators are, for example, the discrete Walsh-Hadamard transform (DWHT), the discrete Fourier transform (DFT), the discrete cosine transform (DCT), the discrete sine transform (DST), the discrete wavelet transform (DWT), and / or the discrete linear chirp transform (DLCT), etc.

[0246] 2. Layer mapping (e.g., performed by a layer mapping circuit): The WTRU or other transmitter / receiver maps the transform-spread data symbols {s1, …, s M} to spatial layers based on the input of the subsequent steps. In GSFBC coding, one or two layers can be output from this block. As an example, if the main beam and the diversity beam are to be transmitted on two antenna ports, then two layers are the output from this block, while in single-beam transmission only one layer is the output.

[0247] 3. Precoding (e.g., performed by a precoding circuit): The precoding operation is applied to the data symbols on each beam involved in the transmission. This step (circuit) is responsible for the digital beamforming step of the hybrid beamforming architecture. As an example, when a diversity beam is to be generated during transmission, the Alamouti space-frequency block decoding technique is applied, including the symbol-reversed complex conjugate according to the following equation:

[0248]

[0249] In other cases where no diversity beam is involved, the precoding step is mostly transparent and connects the layer mapping with the resource mapping step.

[0250] 4. Resource mapping (e.g., performed by a resource mapping circuit): The WTRU or other transmitter / receiver maps the sequence of complex precoded symbols to the resource elements of each beam. If two beams are generated, the corresponding output of the resource mapping step feeds the RF beamformer that performs the analog beamforming of the beam for transmission. Resource mapping frequency-division multiplexes the data symbols assigned to the data subcarriers with any additional control information present in the OFDM symbols assigned to the control subcarriers (e.g., in 5G NR, DM-RS, PT-RS, CSI-RS, PSS / SSS, or other control signals). Thus, the data symbols are effectively spread in the spatial and frequency domains in one or two beams to improve decoding robustness. In contrast, the control symbols are maintained in their original positions so as not to affect any conventional processes related to, for example, data demodulation, CSI estimation, phase noise compensation, etc., that utilize such control information. Examples of control signals include training symbols, reference signals, and pilot symbols.

[0251] 5. GSFBC Control Module (Circuit): This block controls the parameters for the GSFBC to perform single-beam transmission or dual-beam transmission. The WTRU or other wireless transmitter / receiver processor or controller that executes this block selects the transform spreading function and / or provides the parameters for the transmission of the diversity beam depending on impairments and feedback from the receiver (e.g., the severity of beam squint, mobility, and / or whether misalignment may occur due to defects).

[0252] Contrary to what occurs in DFT-spread OFDM (DFT-s-OFDM) waveforms, the application of the DFT as a transform spreading function does not necessarily result in a single-carrier signal. In an embodiment, the purpose of transform spreading is not to generate a single-carrier waveform (as in DFT-s-OFDM), but to spread the constellation data symbols in the frequency domain to equalize the effective channel response seen by the symbols and help compensate for the overall unknown frequency-selective response caused by impairments. Thus, even when applying a DFT-based transform operator in an OFDM signal, the result is still an OFDM signal where the data symbols are first spread in frequency and then frequency-multiplexed with other control information at their intended frequency positions.

[0253] A diversity (e.g., second) transmit beam can be generated such that it has different characteristics from the main (e.g., first) transmit beam in terms of direction, beam width in the horizontal (H) plane, beam width in the vertical (V) plane, or a combination of these differences. This can be useful for coping with unpredictable impairments caused by beam misalignments including beam squint, and for making the channel responses h (1) and h (2) not the same so that a statistical gain can be obtained. The diversity beam can thus have a wider beam width in the plane (H or V) where impairments are more likely to occur, such that detection is improved without sacrificing the beamforming gain of the main beam. Embodiments of this technique are discussed below.

[0254] GSFBC coding can be regarded as an overall means of providing additional diversity to beamforming transmissions with impairments: in the frequency domain through the spreading operation, and in the spatial domain through the diversity beam. Depending on the scenario of interest, one or the other can be selected to enhance the beam resilience of the transmission, including the separation of the beams. As an example, in a scenario where the expected misalignment is not significant, the diversity beam can be avoided, and only the transform spreading step at the main beam may be sufficient to cope with beam squint, thus saving additional resources (see Figure 6 ). Still as an example, in other cases, the beams can be separated in different directions, each beam including transform spreading and only the corresponding half of the subcarriers, to reduce the magnitude of beam squint if the misalignment is not significant (see Figure 7 ).

[0255] In other cases where beam squint is not significant but beam misalignment may degrade performance, the transform expansion step can be avoided, and a diversity (e.g., second) transmit beam can be generated without additional expansion of the complex symbols (see Figure 8 ).

[0256] Both the transform expansion step and the characteristics of the diversity (e.g., second) transmit beam can be adapted to measurements performed at the receiver side (e.g., such as, detection performance statistics, CSI measurements, user speed, or the rate of change of the serving beam, as described below). As signaled to the transmitter, e.g., by means of a capabilities information message or any other control information, the selection of the transform expansion function can also depend on the complexity and capabilities of the receiving side to support a particular subset of functions.

[0257] The transmit processing steps can be summarized as follows. The term "time-frequency resource" used below generally refers to the moments and frequency subcarriers allocated for transmitting data or control information in the first or second beam (if any), e.g., as signaled by the TRP. Without loss of generality, the term "resource allocation" can be used as a synonym for "time-frequency resource".

[0258] The GSFBC control module collects information about the available set of expansion functions (e.g., as obtained from higher layer signaling) and any capabilities information from the receiving side (e.g., as obtained from a capabilities information message), including, e.g., the supported expansion functions and the support for GSFBC with one or two beams.

[0259] Based on this, and based on any beam-related scheduling information, and based on measurements or reports of link performance degradation, the transmitter selects the expansion function and decides on the transmission and characteristics of the second beam (e.g., its H / V beamwidth, orientation, etc.).

[0260] The transmitter generates complex constellation data symbols, applies the expansion function, and outputs the resulting complex data symbols that will be mapped to the data layer by the layer mapping module.

[0261] If there is a second (e.g., diversity) transmit beam, the precoding module performs symbol inversion and complex conjugation of the complex data symbols to be mapped to the time-frequency resources for the data in the second beam.

[0262] The resource mapping module maps the complex data symbols to the time-frequency resources allocated for the data in the first (e.g., primary) transmit beam and the second (e.g., diversity) transmit beam (if any), and maps any other control information (e.g., such as, DM-RS, PT-RS, CSI-RS, PSS / SSS, or other control signals) to the time-frequency resources allocated for the control in the first beam and the second beam (if any).

[0263] The transmitter sends a first (e.g., primary) beam and a second (e.g., diversity) beam (if any) via an RF beamformer and a TX antenna array, and also transmits any control signaling information including information about the applied GSFBC coding process.

[0264] Without loss of generality, assuming that according to one or more of the above steps, each transmitted beam is accompanied by a suitable diversity beam (if applicable), the embodiments and examples herein can be applied to single-rank transmission, but they can also be applied to spatially multiplexed transmission. The proposed method can also be extended to multi-user MIMO scenarios, provided that the precoding includes MU-MIMO and the obtained channel response has incorporated the effect of any precoding applied to the MU-MIMO for spatially multiplexing users. Additionally, although described above in connection with Figures 5 - 8 the transmitting circuitry, a corresponding receiving circuitry can be constructed as the dual of these transmitting circuits.

[0265] In some embodiments, the WTRU receives a GSFBC-coded signal.

[0266] Figure 9 is a block diagram of a receiver circuit 900 for GSFBC decoding according to an embodiment.

[0267] Referring to Figure 9 , regardless of the application of transform spreading, the detection of the diversity beam (when present) can utilize standard Alamouti decoding. Referring to Figure 9 , the receiving processing required for the detection and recovery of the primary (e.g., first) beam and the diversity (e.g., second) beam of the disclosed GSFBC coding process is shown. In this case, after the resource demapping stage shown in Figure 9 , the received symbols from the primary beam and the diversity beam can be written as:

[0268]

[0269] where w1,…,w M are uncorrelated, circularly symmetric complex Gaussian variables representing additive white Gaussian noise. Assume that the noise power equals N0 and the input SNR, γ, is defined as:

[0270]

[0271] where the expectation operator in the numerator runs over all possible transmitted symbols x i .

[0272] If the receiver “knows” the channel state (e.g., from a suitable demodulation reference signal or other pilot information) and Then the symbols can be recovered in pairs at the cancellation precoding circuit (stage) 912 in Figure 9 by means of the standard Alamouti process. It is assumed that the channel response does not vary significantly over consecutive indices and that:

[0273]

[0274] The process can continue in pairs to show the symbols that can be obtained after combined layer demapping and equalization (circuit / stage 914), as Figure 9 shown. The layer demapping process will transparently forward the symbols to the appropriate equalization stage, such as a linear minimum mean square error (LMMSE) equalizer or a decision feedback equalizer (DFE), whose input has an effective channel gain approximately equal to . The post-detection SNR is given by and can be taken into account during the equalization step.

[0275] In the case of applying transform spreading to the transmission, the symbols obtained after equalization can undergo a transform despreading step to produce an estimate of the original symbols , i.e.:

[0276]

[0277] The existence of the inverse transform function is permitted by the orthogonality of the operator , and the operator ensures the existence of the inverse in the finite-dimensional space and can be represented by the transpose of the matrix representation of .

[0278] Depending on the presence or absence of diversity beams and whether it is affected by the transmission with transform spreading along with the main beam, a combination of the above steps can be applied to the received signal.

[0279] Similar to the transmission processing steps, the GSFBC control module will configure the appropriate parameters of the main beam, diversity beam (if present), and transform despreading stage at the receiver according to the signaling obtained from the transmitter side.

[0280] Still referring to Figure 9 , according to an embodiment, assuming that both the received main (e.g., first) receive beam and the diversity (e.g., second) receive beam are received, the structure and operation of the receiving circuit 900 (e.g., the receiving processing steps for GSFBC decoding) are described as follows.

[0281] A receive antenna array RX 902 with Nx×Ny antenna elements is configured to receive a primary (first) receive beam and a diversity (second) receive beam, both carrying data symbols, where at least one of the beams carries data symbols to which one or more transform spreading functions have been applied at the transmitter.

[0282] The GSFBC control module 904 is configured to provide information regarding the applied transform spreading functions and the resource allocation of the primary receive beam and the diversity receive beam, as obtained, for example, via control signaling from the transmitter, and is further configured to provide information regarding the parameters of the primary beam and the diversity beam.

[0283] The RF beamformer circuit 906 includes a first RF beamformer 908a and a second RF beamformer 908b. The first RF beamformer 908a is configured to form the primary beam in response to information regarding one or more parameters of the primary beam and / or one or more parameters of the diversity beam from the control module 904, and the second RF beamformer 908b is configured to form the diversity beam based on signals received from the Nx×Ny antenna elements of the receive antenna array 902.

[0284] The resource demapping circuit 910 is configured to obtain a first set of received control symbols and received data symbols resulting from the superposition of the primary beam and the diversity beam according to the following equation:

[0285] {r1,…,r M} Equation (18)

[0286] The precoding cancellation circuit 912 is configured to cancel the precoding of the data symbols performed at the transmitter by combining the first set of received complex data symbols with their sign reversal and complex conjugate weighted by the channel responses of the first and second beams, to produce a second set of received data symbols according to the following equation:

[0287]

[0288] The layer demapping + equalizer circuit 914 is configured to transparently forward the second set of received data symbols in steps to an equalizer stage, which produces a set of transform spread equalized data symbols according to the following equation:

[0289]

[0290] The transform despreading circuit 916 is configured to apply the inverse of the transform spreading function used in transmission to the equalized data symbols in response to the transmitter transform spreading information from the control module 904, to produce a suitable estimate of the originally transmitted complex constellation data symbols.

[0291] The parallel-to-serial converter 918 is configured to convert a parallel data stream from the transform despreading circuit 916 into a serial data stream of estimated (recovered) data symbols (e.g., an estimate of the originally transmitted data symbols) according to the following equation:

[0292]

[0293] Without loss of generality, the receiving circuit 900 herein operates considering single-rank transmission, but they can also be applied to spatial multiplexing transmission (e.g., in single-user MIMO or multi-user MIMO scenarios).

[0294] Still referring to Figure 9 , other embodiments of the receiving circuit 900 are considered. For example, if the receiving circuit 900 receives main and diversity beams without transform spreading, then the transform despreading circuit 916 can be omitted from the circuit 900, or the function or operation of the circuit 916 can be suspended. Similarly, if the receiving circuit 900 receives only the main beam, then the RF beamformer circuit 906 can be omitted from the circuit 900, or the function or operation of the circuit 906 can be suspended. In addition, a transmitter circuit compatible with and / or suitable for the receiving circuit 900 can be the dual of the receiving circuit.

[0295] Referring to Figures 4 - 9 , if the diversity beam is the same as the main beam, then the resulting 3dB SNR gain after Alamouti decoding will come at the cost of 3dB more transmit power and thus will not result in a net gain. To obtain a net gain, the diversity beam can be generated according to a different criterion (at both the transmitter and receiver circuits) than the criterion according to which the main beam is generated. Examples of generating the diversity beam according to different criteria include:

[0296] - If the impairment from beam misalignment is significant, then the diversity beam can be generated such that it has a wider beamwidth in the plane (H or V) in which random movement is likely to be more frequent during communication. If the movement is completely random or no particular direction dominates in the result, then the diversity beam can be widened in both the H and V planes to enhance detection in any case.

[0297] - Beam broadening in the H or V plane can be achieved by exciting fewer RF antennas and / or antenna elements in the corresponding plane than are typically employed in the connection mode for the main beam. If desired, the loss due to lower beamforming gain can be compensated by feeding a higher per-PA transmit power to the power amplifier (PA). In other cases, the diversity beam can have a lower transmit power while still providing additional robustness to the main beam without sacrificing coverage. Generation of a wider beam can be accomplished according to the scheduler to avoid a final conflict with the beams for other users, potentially requiring further precoding at the digital precoding stage to minimize inter-user interference when space multiplexing signals.

[0298] - If the movement (of the transmitter and / or receiver relative to each other) is specifically predictable, the transmitter can select one of the directions with a higher reception chance in a direction adjacent to the main beam in the transmitter's beam grid, provided it is not reserved for another user.

[0299] - If the beam skew is not significant, but there is impairment from beam misalignment or there is a blockage in the line-of-sight direction, the transform expansion step can be omitted, and a diversity beam can be generated with characteristics (orientation and H / V beamwidth) that can best enhance detection. This situation can be applied when very narrow beams at high frequencies make it difficult for the beam management scheme to successfully track the movement of the WTRU. In some cases, the diversity beam can be pointed in a completely different direction from the main beam to help overcome a final obstacle in the line-of-sight direction. In such a scenario, depending on the need to improve resilience against misalignment, the diversity beam can or can not have a higher beamwidth.

[0300] - In all of the above cases, the diversity beam can be generated by different TRPs in a multi-TRP scenario.

[0301] Figure 10 is a diagram illustrating the possibility of a diversity beam in a single-TRP scenario according to an embodiment, which shows examples of widened beams 1000, 1002 in the same or adjacent directions relative to the main beam 1004 and a diversity beam 1006 in a different direction.

[0302] Figure 10 Embodiments illustrating these possibilities for the case of a single TRP are shown.

[0303] Still referring to Figure 10, the selection of the diversity beams can be done by the transmitter 1008 (e.g., a base station) in a manner transparent to the receiver 1010 (e.g., a WTRU). In some examples, the transmitter may not signal the characteristics of the diversity beams to the receiver, and the receiver can simply obtain the combined data stream from the two beams and perform appropriate signal decoding. The channel state can only be obtained by the receiver at the main beam and the diversity beams, e.g., by means of suitable reference signals or other pilot information. However, in some examples, the transmitter may also signal the receiver information about one or more quasi-co-located (QCL) source signals (e.g., an index or any other similar identifier) such that the receiver can estimate (e.g., related to any one of time, frequency, and / or spatial characteristics) some parameters based on the source signals and apply them to the signal reception at the main beam and / or the diversity beams.

[0304] As explained above in connection with Figure 3 As explained above, since the main beam is split into two beams, each beam pointing in a different direction and carrying a corresponding half of the subcarriers to reduce the beam squint effect, a second beam can be generated. In this case, the characteristics of the beams are determined by the GSFBC control module as described above.

[0305] When certain events are satisfied, the receiver can trigger a request to activate GSFBC coding. GSFBC coding can also be configured, activated, and / or triggered by the transmitter when certain events are satisfied that may be assisted by measurements reported by the receiver. Such events and measurements can be and can include:

[0306] - The difference in the magnitudes of the CSI measurements at the farthest and nearest subcarriers with respect to the DC subcarrier is higher than a threshold (indicating beam squint). After averaging over multiple time slots, TTIs, or radio frames, this difference can be measured by the transmitter or reported by the receiver to account for the eventual channel variations in time and frequency.

[0307] - The rate of change of the user speed or the serving beam is higher than a threshold (indicating channel aging and / or mobility), as measured by the transmitter or reported by the receiver.

[0308] - The lower rate modulation and coding scheme required to maintain a given detection performance in response to an ACK / NACK indication transmitted by the receiver (indicating performance degradation not resolved by conventional beam management and / or link adaptation processes), as measured by the transmitter or reported by the receiver.

[0309] -A mismatch between CSI measurements performed on reference signals for beam management (e.g., CSI-RS or other pilot information) and CSI measurements performed on demodulation reference signals for data detection (e.g., DM-RS or other pilot information), indicating performance degradation not resolved by conventional beam management and / or link adaptation processes, as measured by the receiver.

[0310] -The rms error magnitude of CSI measurements is higher than a threshold, indicating impairment or inaccuracy of the acquired CSI, as measured by the transmitter or reported by the receiver.

[0311] -Performance statistics (e.g., BER, BLER, ACK / NACK statistics averaged over multiple time slots, etc.) are higher than a fourth threshold, indicating performance degradation not resolved by conventional beam management and / or link adaptation processes, as measured by the transmitter or reported by the receiver.

[0312] Depending on implementation needs, other drivers may also trigger the activation of GSFBC or a request to activate GSFBC. Measurements performed at the receiver side can be reported to the transmitter when some conditions are met (e.g., their levels exceed or are below thresholds whose values can be signaled by the transmitter in a configuration message). The receiver can also report other measurements or combinations of measurements, including a request for GSFBC coding of the triggered beam (if deemed appropriate), to assist the transmitter in evaluating the potential activation of GSFBC. The transmitter can analyze these reports together with other factors (e.g., the number of active beams compared to the maximum number of beams, power consumption, transmit power margin, etc.) for the activation of GSFBC.

[0313] Measurement reports from the receiver can be transmitted on a shared channel (e.g., physical uplink control or shared channel) and can be configured by the transmitter according to, for example, the type of quantity to be reported and whether the report is to be transmitted in a periodic, semi-persistent, aperiodic, on-demand, or event-triggered manner (including the appropriate configuration of events that must trigger a report from the receiver).

[0314] Figure 11 FIG. is an illustration of a control signaling mechanism involved in activating GSFBC by a transmitter in response to a request from a receiver according to an embodiment. Without loss of generality, Figure 11The gNB 1100 therein may be a transmitting entity and the WTRU 1102 may be a receiving entity. At 1104, the WTRU 1102 first reports its capabilities to the gNB 1100 so that the gNB is aware of any constraints related to GSFBC support. At 1106, the gNB 1100 may evaluate the applicability of GSFBC when receiving a request to activate / deactivate GSFBC from the WTRU 1102 based on, for example, link performance, the number of active beams compared to the maximum number of beams at the transmitter, or available power margin, etc. At 1108, the request from the WTRU 1102 may include the amount of performance degradation of the reported link, such as CSI measurements, the rms error magnitude of CSI measurements, user speed, performance statistics, modulation and coding scheme, and / or any other suitable indicator to assist the gNB 1100. If the gNB 1100 decides to activate GSFBC at 1110, it may signal some GSFBC-related parameters to the WTRU by, for example, a suitable downlink control indicator (DCI) signaling as part of the physical downlink control channel (PDCCH), higher layer radio resource control (RRC) signaling, or by means of a MAC CE command. Thus, at 1112, GSFBC-encoded data including one or two beams is generated by the gNB 1100 to improve beam resilience as described above, and the gNB transmits the data to the WTRU 1102 and also transmits a control signal to the WTRU 1102. At 1114, as part of the described cycle, the WTRU 1102 may cancel GSFBC decoding to recover the data transmitted from the gNB 1100, measure GSFBC-related quantities, estimate the suitability of GSFBC for the current conditions, and, if the WTRU requests activation of GSFBC, perform the operations at 1104, 1106, and 1108, receive an activation response from the gNB at 1110, and obtain GSFBC parameters from the gNB 1100 at 1112.

[0315] The control information conveyed by the transmitter (e.g., the gNB 1100 at 1112) may include an indication of GSFBC encoding, and / or an index to the applied transform expansion function in the set of functions included in a predefined codebook. The receiver (e.g., the WTRU 1102) may also perform a blind detection of the actual transform in use without an explicit indication from the transmitter. The transform may also be signaled statically or semi-statically via an RRC configuration message.

[0316] The characteristics of the diversity beam (or the second beam in a beam splitting scenario), e.g., its H / V beamwidth or its orientation, can be transparent to the receiver and its parameters do not need to be exposed for detection to be achieved. If needed, the receiver only obtains channel state information (CSI) to combine symbols from the main beam and the diversity beam according to the above process. Whether the diversity beam is active or not, the main beam can be selected and updated according to conventional beam management techniques. In other cases, gNB 1100 can also signal information of one or more QCL source signals to WTRU 1102 such that the WTRU can estimate some parameters of the main beam and / or the diversity beam.

[0317] The transmitter (e.g., gNB 1100) can also trigger GSFBC without a request from the receiver (e.g., WTRU 1102), e.g., as part of a predefined rule or hard-coded by the implementation, because the transmitter "knows" the amount of beam skew or other impairments affecting reception, or because of insufficient knowledge (or accuracy) of the CSI. This is illustrated in Figure 12 the exemplary flowchart where transmitting gNB 1200 triggers the activation of GSFBC without a request from receiving WTRU 1202, but with the aid of a feedback report from it.

[0318] Figure 12FIG. is an illustration of a control signaling mechanism involved in the activation of GSFBC by a transmitter without a request from a receiver according to an embodiment. Without loss of generality, gNB 1200 may be a transmitting entity and WTRU 1202 may be a receiving entity. At 1204, WTRU 1202 first reports its capabilities to gNB 1200 so that gNB knows any constraints related to GSFBC support. At 1206, WTRU 1202 transmits one or more GSFBC reports to gNB 1200, which may include the amount of performance degradation of the link, such as CSI measurements, the rms error magnitude of CSI measurements, user speed, performance statistics, modulation and coding schemes, and / or any other suitable indicators to assist gNB 1200. In response to this report, gNB 1200 may evaluate the applicability of GSFBC based on, for example, link performance, the number of active beams compared to the maximum number of beams at the transmitter, or available power margin, etc. If gNB 1100 decides to activate GSFBC at 1208, it may signal some GSFBC-related parameters to WTRU1202 by means of, for example, a suitable downlink control indicator (DCI) signaling as part of the physical downlink control channel (PDCCH), higher layer radio resource control (RRC) signaling, or by means of a MAC CE command. Thus, at 1210, gNB 1200 generates GSFBC-encoded data including one or two beams to improve beam flexibility as described above, and gNB transmits this data to WTRU 1202 and also transmits a control signal to WTRU 1202. At 1212, as part of the described cycle, WTRU 1202 may cancel GSFBC decoding to recover the data transmitted from gNB 1200, measure GSFBC-related quantities, estimate the suitability of GSFBC for the current conditions, and perform the operations at 1204, 1206, and 1208 and obtain GSFBC parameters from gNB 1200 at 1210.

[0319] Reference Figures 11 - 12 , in an embodiment, the change to the 5G NR specification includes the transmission of GSFBC-encoded signals in the downlink. If appropriate, similar steps may be followed in the uplink and / or similar steps may be applied to other channels.

[0320] The WTRU “assumes” that the PDSCH channel undergoes further layer mapping and precoding after scrambling and modulation steps to generate GSFBC-encoded symbols according to the changes described herein. To better adapt to existing 3GPP physical layer blocks, one or more of the above-described (performed by the transform expansion circuit) transform expansion steps are included herein as part of the layer mapping (performed by the layer mapping circuit).

[0321] Without loss of generality, the changes are described for the case of up to two layers transmitted via up to two antenna ports and one codeword. The results can be easily generalized to higher numbers of layers and / or antenna ports in SU - MIMO and MU - MIMO.

[0322] The WTRU “assumes” that the complex - valued modulated symbols for codeword 0 are mapped to 1 or 2 layers for transmission. Let d (0) (i) represent the complex - valued modulated symbol in codeword 0 output from the modulation mapper, where the codeword - to - layer mapping operation is performed as described below to produce symbols at the output of the layer - mapping circuit. In this example, is the number of complex - valued modulated symbols in codeword 0, is the number of symbols per layer, and represents the discrete orthogonal transform applied to the complex - valued modulated symbol d (0) (i) (where ) and the output of is as follows. As described below, the higher - layer parameter DLTransformSpreading is introduced to control whether the transform - spreading circuit applies transform - spreading to the beam, and the higher - layer parameter DLTransmitDiversity is also introduced to control whether a second (diversity) beam is generated.

[0323] 1. If DLTransformSpreading is set to 1, then:

[0324] - If DLTransmitDiversity is set to 1, then the WTRU “assumes” that 2 layers are used for transmission of the physical channel on 2 antenna ports as follows:

[0325] x (0) (i) = t (0) (2i), Equation (22)

[0326] x (1) (i) = t (0) (2i + 1), Equation (23)

[0327] where

[0328] - If DLTransmitDiversity is set to 0, then the WTRU “assumes” that 1 layer is used for transmission of the physical channel on 1 antenna port as follows:

[0329] x (0) (i) = t (0) (i),

[0330] where

[0331] 2. If DLTransformSpreading is set to 0, then:

[0332] - If DLTransmitDiversity is set to 1, then the WTRU "assumes" that 2 layers are used for the transmission of the physical channel on 2 antenna ports, as follows:

[0333] x (0) (i) = d (0) (2i),

[0334] x (1) (i) = d (0) (2i + 1),

[0335] where

[0336] - If DLTransmitDiversity is set to 0, then the WTRU "assumes" that 1 layer is used for the transmission of the physical channel on 1 antenna port, as follows:

[0337] x (0) (i) = d (0) (i),

[0338] where and

[0339] The transform can be explicitly described by an index in a predefined codebook of a transform spreading function configured by a higher layer

[0340] In an embodiment, the precoding for GSFBC is only used in combination with the layer mapping for GSFBC, although this is not required. Depending on the value of the higher layer parameter DLTransmitDiversity, the precoding operation is described for one or two antenna ports.

[0341] 1. If DLTransmitDiversity is set to 1, then for the transmission on 2 antenna ports, the WTRU "assumes" that the output of the precoder y(i) = [y (0) (i) y (1) (i)] T , is described by the following equation:

[0342]

[0343] For where is the number of precoded symbols per antenna port. The factor preserves the transmit power such that GSFBC coding does not increase the transmit power.

[0344] 2. If DLTransmitDiversity is set to 0, then the WTRU "assumes" that the output y(i) of the precoder = y (0) (i), is described by the following equation:

[0345] y (0) (i) = x (0) (i), Equation (29)

[0346] where

[0347] Following the conventional antenna port mapping procedure suitable for 5G NR, the symbols at the output of the precoding circuit are then mapped to the appropriate antenna ports.

[0348] The previously described embodiments and examples can be better understood by an analysis of the exemplary embodiments described below.

[0349] The performance of GSFBC coding is shown by suitable link-level simulations that model the effects of beam squint and / or beam misalignment. A transform expansion step based on the discrete Walsh-Hadamard transform (DWHT) is disclosed in this example. As a function of carrier frequency f c and user bandwidth B (where N H = N V ), the beam squint effect is modeled in a rectangular uniform planar array (UPA) including N H × N V antennas. By exciting half of the antennas in each direction, i.e., N H / 2 × N V / 2 antennas, the diversity beams have a broadened beam width in both the H and V planes. Both the main beam and the diversity beams carry half of the total transmit power so as not to bias the bit signal-to-noise ratio Eb / N0.

[0350] By randomly varying the instantaneous elevation angle and azimuth angle θ according to the uniform distributions given by F and θ = U[θ F (1 - ∈), θ and azimuth angle θ in each time slot, where and θ Fdenote the focusing directions of elevation (vertical V) and azimuth (horizontal H), respectively, and ∈ is the maximum relative deviation. The main beam point and the diversity beam point are in the same instantaneous direction in each time slot. and are subject to beam skew according to their corresponding parameters. Since there is no inter-carrier interference (ICI) due (at least in this example) to beam misalignment (which is modeled as changing the level of the signal in each time slot, rather than the level within a time slot), the rate of change of the beam heading does not affect the performance, but only the simulation time required to obtain statistically representative results.

[0351] Figure 13 is a diagram of a geometric arrangement of an array 1300 of antennas 1302 for simulation using UPA in the XZ plane, according to an embodiment.

[0352] The following table summarizes the simulation parameters.

[0353] Table 1: Simulation assumptions

[0354]

[0355]

[0356] The results are shown in Figure 14 , Figure 15 and Figure 16 middle.

[0357] Figure 14 is used in QPSK (left diagram) and 16QAM (right diagram) according to an embodiment Figure 13 Graph of bit error rate versus bit SNR for simulation results of antenna geometry with beam skew and without beam misalignment, f c =200GHz, B=7.84GHz and 15.68GHz.

[0358] Figure 15 According to the use of the embodiment Figure 13 Graph of Bit Error Rate vs. Bit SNR for simulation results of antenna geometry with beam skew, random beam misalignment up to ±5% of the ideal direction, QPSK, f c =200 GHz, B=7.84 GHz (left graph) and 15.68 GHz (right graph).

[0359] Figure 16 According to the use of the embodiment Figure 13 Graph of Bit Error Rate vs. Bit SNR for simulation results of antenna geometry with beam skew, random beam misalignment up to ±10% of the ideal direction, QPSK, f c= 200 GHz, B = 7.84 GHz (left graph) and 15.68 GHz (right graph).

[0360] In the absence of beam misalignment ( Figure 14 ), the transform spreading step improves the uncoded bit error rate by an amount that increases with the magnitude of the beam skew (i.e., with the user's bandwidth). The remaining Eb / N0 gap relative to the ideal curve (labeled "no beam skew" in Figure 14 ) is due to the average SNR loss caused by beam skew, which can be compensated for in practice by a lower coding rate when using forward error correction.

[0361] In the case of random beam misalignment up to ±5% and ±10% of the ideal direction ( Figure 15 and Figure 16 ), respectively), the best results can be obtained by combining the DWHT with diversity. The presence of the DWHT improves the results even in the absence of diversity, especially for larger user bandwidths (15.68 GHz) and smaller beam misalignments (5%). This is evidence that transform spreading is particularly useful for coping with and compensating for beam skew, while diversity brings robustness to beam misalignment. The combination of the two can approach the ideal case of no beam skew or misalignment in terms of performance (~3 dB for ∈ = 0.05 and 12 dB for ∈ = 0.1). Note that misalignment up to ±10% of the beam direction is impractically high and is only disclosed here for illustrative purposes of the performance of the DWHT and diversity techniques in the face of very challenging conditions.

[0362] Figure 17 is a flowchart for generating a transmission signal based on generalized space-frequency block coding (GSFBC) according to an embodiment.

[0363] As Figure 17 shown, the flowchart represents a first WTRU or a set of first WTRUs transmitting a wireless signal to a second WTRU, characterized in that:

[0364] · At 1700, obtain configuration information about the codebook for the transform spreading function and thresholds T1 and T2;

[0365] · At 1702, obtain capability information that includes, for example, a subset of the transform spreading functions supported by the second WTRU or any constraints related to the support of the generalized space-frequency block coding process;

[0366] · At 1704, obtain a measurement or report of the performance degradation of the link, such as the SNR degradation S1 caused by beam skew and / or the SNR degradation S2 caused by beam misalignment;

[0367] · At 1706, beam-related scheduling information such as beams for serving other users or available transmit power is obtained;

[0368] · At 1708, a function is selected from a codebook of available transform expansion functions based on the relationship between S1 and T1; for example, if S1 > T1, then at 1710, a function is selected from the codebook of transform expansion functions and proceeds to 1712, otherwise proceeds directly to 1712;

[0369] · At 1712, if S2 > T2 and diversity beams are permitted, then at 1714, the H / V beamwidth, the orientation of the diversity beam, and permission from the scheduler to use the diversity beam are selected and proceed to 1716, otherwise proceed directly to 1716; and

[0370] · At 1716, GSFBC-encoded symbols are generated on the configured beams, and GSFBC-related control signaling information is also transmitted on one or both of the configured beams or on one or more additional beams, and then returns to 1704.

[0371] Wherein the codebook of transform expansion functions can be configured by a higher layer, for example, via RRC configuration information, MAC CE commands, or predefined by an implementation.

[0372] Wherein the thresholds T1 and T2 can be configured by a higher layer message (such as RRC configuration information, MAC CE commands), or predefined by an implementation.

[0373] Wherein the capability information can include, for example, a subset of transform expansion functions supported within the codebook, and / or any other restrictions on the transform functions in the codebook, as reported by the second WTRU via a higher layer message during initial connection establishment.

[0374] Wherein the performance degradation of the link can include, for example, SNR degradation caused by beam skew, SNR degradation caused by beam misalignment, CSI measurement, rms error magnitude of CSI measurement, performance statistics, modulation and coding scheme, or user speed, etc.

[0375] Wherein the SNR degradation caused by beam skew can be measured by the first WTRU or a set of first WTRUs as the difference between the SNR at the farthest subcarrier and the nearest subcarrier relative to the DC subcarrier averaged over a predefined number of time slots, TTIs, or radio frames.

[0376] The SNR degradation caused by beam misalignment can be measured by the first WTRU or a set of first WTRUs as a reduction in the modulation and coding scheme required to maintain a given detection performance in response to an ACK / NACK indication transmitted by the second WTRU, the reduction being averaged over a predefined number of time slots, TTIs, or radio frames.

[0377] The SNR degradation caused by beam misalignment can be measured by the second WTRU as a reduction in the modulation and coding scheme required to maintain a given detection performance based on the measured block error rate, the reduction being averaged over a predefined number of time slots, TTIs, or radio frames.

[0378] The number of time slots, TTIs, or radio frames used to average the SNR degradation caused by beam skew or beam misalignment can be configured by a higher layer via, for example, RRC configuration information or DCI control information.

[0379] The performance degradation of the link can be measured by the second WTRU and reported to the first WTRU or a set of first WTRUs via, for example, a shared control or data channel or a MAC CE command.

[0380] The report including the performance degradation of the link caused by beam skew and / or beam misalignment can include a request to trigger GSFBC coding of a beam including transform spreading and / or diversity beams.

[0381] The report including the performance degradation of the link caused by beam skew and / or beam misalignment can be transmitted by the second WTRU in a periodic, semi-persistent, aperiodic, on-demand, or event-triggered manner according to configuration information received from a higher layer (e.g., via RRC signaling or DCI control information).

[0382] The function of the codebook from the available transform spreading functions can be selected by the first WTRU or a set of first WTRUs depending on, for example, the SNR degradation S1 caused by beam skew, the validity, complexity, and / or the capability information transmitted by the second WTRU of the extended symbol.

[0383] If there is no line-of-sight blockage between the first WTRU or a set of first WTRUs and the second WTRU, the orientation of the diversity beam can be the same as that of the main beam.

[0384] If there is a line-of-sight blockage between the first WTRU or a set of first WTRUs and the second WTRU, or if the movement of the second WTRU makes the selected diversity beam maximize the detection probability, the orientation of the diversity beam can be different from that of the main beam.

[0385] Wherein, if significant beam misalignment is detected in the H / V direction or both, the H / V beamwidth of the diversity beam can be increased relative to the main beam.

[0386] Wherein, compared with the antennas involved in the transmission of the main beam, the H / V beamwidth of the diversity beam can be increased by exciting a smaller number of antennas along the corresponding direction.

[0387] Wherein, the permission to use the diversity beam can be given by a scheduler according to, for example, channel conditions, interference with other beams, the number of available beams, the complexity of the precoding operation, and / or total power consumption, etc.

[0388] Wherein, depending on, for example, capability information, measurement of SNR degradation, beam-related scheduling information, and / or service requirements, the symbols encoded by GSFBC may include a transform spreading step on the main beam, a transform spreading step on the diversity beam, or both.

[0389] Wherein the GSFBC-related control signaling information may include an indication of GSFBC encoding and / or an index of the transform spreading function applied in the codebook.

[0390] Wherein the GSFBC-related control signaling information may be transmitted to the second WTRU in the form of higher layer RRC configuration information, DCI control indication, or MAC CE command.

[0391] Wherein, in the downlink of a wireless communication system, the first WTRU is a base station device and the second WTRU is a user equipment.

[0392] Wherein the set of the first WTRUs are multiple transmit-receive points in the downlink of a multi-TRP wireless communication system.

[0393] Wherein the first WTRU and the second WTRU are user equipments in the sidelink of a wireless communication system.

[0394] Wherein, in the uplink of a wireless communication system, the first WTRU is a user equipment and the second WTRU is a base station device.

[0395] Figure 18 is a flowchart of a method related to the reception of a GSFBC-encoded signal according to an embodiment.

[0396] Referring to Figure 18 , the first WTRU is receiving a wireless signal from the second WTRU or the set of the second WTRUs, and the method is characterized in that the first WTRU:

[0397] · At 1800, obtain configuration information about the codebook of the transform spreading function and thresholds T3, T4, T5;

[0398] · At 1802, transmit capability information including, for example, a subset of supported transform spreading functions or any constraints related to the support of a generalized space-frequency block coding process;

[0399] · At 1804, perform measurements of the performance degradation of the link, such as SNR degradation S3 caused by beam squint and / or SNR degradation S4 caused by beam misalignment;

[0400] · At 1806, if the user's speed > T5, then, at 1808, trigger a request to activate GSFBC coding and proceed to 1810; otherwise, proceed directly to 1810;

[0401] · At 1810, if S3 > T3, then, at 1812, report the performance degradation of the link caused by beam squint and proceed to 1814; otherwise, proceed directly to 1814;

[0402] · At 1814, if S4 > T4, then, at 1816, report the performance degradation of the link caused by beam misalignment and proceed to 1818; otherwise, proceed directly to 1818

[0403] · At 1818, obtain GSFBC-related control signaling information and proceed to 1820; and

[0404] · At 1820, perform detection of the beam for GSFBC coding by performing transform despreading and Alamouti-based combining on the symbols in the main beam and / or diversity beam, and return to 1804.

[0405] Wherein the codebook of the transform spreading function can be configured by a higher layer, such as via RRC configuration information, DCI information, MAC CE commands, or predefined by the implementation.

[0406] Wherein the thresholds T3, T4, and T5 can be configured by higher layer messages (such as RRC configuration information, DCI information, MAC CE commands), or predefined by the implementation.

[0407] Wherein the capability information can include, for example, a subset of the transform spreading functions supported within the codebook, and / or any other restrictions on the transform functions in the codebook, as reported to the second WTRU or the set of second WTRUs via a higher layer message during initial connection establishment.

[0408] Wherein the performance degradation of the link can include, for example, SNR degradation caused by beam squint, SNR degradation caused by beam misalignment, CSI measurement, rms error magnitude of CSI measurement, performance statistics, modulation and coding scheme, or user speed, etc.

[0409] The SNR degradation caused by beam skew can be measured by the first WTRU as the difference in SNR between the farthest and nearest subcarriers relative to the DC subcarrier averaged over a predefined number of time slots, TTIs, or radio frames.

[0410] The SNR degradation caused by beam misalignment can be measured by the first WTRU as the reduction in the modulation and coding scheme required to maintain a given detection performance based on the measured block error rate, where the reduction is averaged over a predefined number of time slots, TTIs, or radio frames.

[0411] The number of time slots, TTIs, or radio frames used to average the SNR degradation caused by beam skew or beam misalignment can be configured by a higher layer via, for example, RRC configuration information.

[0412] A report including the performance degradation of a link caused by beam skew and / or beam misalignment can be transmitted by the first WTRU via, for example, a shared control or data channel or a MAC CE command.

[0413] A report including the performance degradation of a link caused by beam skew and / or beam misalignment can be transmitted by the first WTRU in a periodic, semi-persistent, aperiodic, on-demand, or event-triggered manner according to configuration information received from a higher layer, for example, via RRC signaling.

[0414] The GSFBC-related control signaling information can include a selected function in the codebook of the transform expansion function.

[0415] The GSFBC-related control signaling information can be obtained by the first WTRU via an RRC configuration message, a DCI control indication, or a MAC CE command.

[0416] The GSFBC-related control signaling information can be obtained by the first WTRU via blind decoding.

[0417] The transform despreading operation can include the inverse of a transform selected by a transmitter in the codebook of the transform expansion function.

[0418] In the downlink of a wireless communication system, the first WTRU is a user equipment and the second WTRU is a base station equipment.

[0419] The set of second WTRUs are multiple transmit-receive points in the downlink of a multi-TRP wireless communication system.

[0420] The first WTRU and the second WTRU are user equipments in the sidelink of a wireless communication system.

[0421] Among them, in the uplink of a wireless communication system, the first WTRU is a base station device, and the second WTRU is a user equipment.

[0422] Figure 19 is a flowchart of a method for transmitting a transform spread data symbol in a beam according to an embodiment.

[0423] Referring to Figure 19 , at 1900, the WTRU applies a transform spread function that spreads the data symbol in the frequency domain to the data symbol. Examples of transform spread functions are disclosed elsewhere herein.

[0424] At 1902, the WTRU forms a transmit beam. Examples of transmit beamforming are disclosed elsewhere herein.

[0425] At 1904, the WTRU transmits the transform spread data symbol in the transmit beam (“on it” or “through it” are other suitable terms).

[0426] Still referring to Figure 19 , although the WTRU is described as transmitting a data symbol in a single transmit beam, it is contemplated that the WTRU may form multiple transmit beams and transmit data symbols in multiple transmit beams. For example, the WTRU may form a primary transmit beam and a diversity transmit beam and transmit data symbols on both beams. Additionally, the data symbol transmitted in one beam may be the complex conjugate of the data symbol in another beam (e.g., with or without sign inversion). Additionally, the beams may have different parameters, such as different directions, different half-power beam widths in the azimuth and / or elevation dimensions, different frequencies / wavelengths, different phases, different amplitudes, different powers, and / or may carry data symbols on different subcarriers. Additionally, the WTRU may adjust the transform spread function and / or one or more beams in response to feedback from a beam receiver.

[0427] Figure 20 is a flowchart of a method for receiving data symbols in multiple beams according to an embodiment.

[0428] Referring to Figure 20 , at 2000, the WTRU receives a data symbol in a first beam, such as a primary receive beam, to which a transform spread function that spreads the data symbol in the frequency domain has been applied. Examples of transform spread functions are disclosed elsewhere herein.

[0429] At 2002, the WTRU receives the complex conjugate (with or without sign inversion) of a data symbol in a second beam, such as a diversity receive beam, to which a transform spread function that spreads the complex conjugate in the frequency domain has been applied. Examples of diversity beams are disclosed elsewhere herein.

[0430] At 2004, the WTRU combines the transformed extended data symbol received and the complex conjugate of the transformed extended data symbol received. Examples of combining the transformed extended data symbol and the complex conjugate of the transformed extended data symbol are disclosed elsewhere herein.

[0431] At 2006, the WTRU recovers the data symbol by applying the inverse of the transform extension function to the combination of the transformed extended data symbol received in the first beam and the complex conjugate received in the second beam.

[0432] Still referring to Figure 20 , although the WTRU is described as receiving the data symbol and the complex conjugate of the data symbol in multiple beams, it is contemplated that the WTRU may receive other combinations of data symbols in multiple beams. For example, the WTRU may receive the data symbol of the first set of modulated subcarriers in one beam and may receive the data symbol of the second set of modulated subcarriers in another beam, where the second set of subcarriers is different from the first set of subcarriers (although there may be some overlap between the first set and the second set of subcarriers). In addition, the beams may have different parameters, for example, different directions, different half-power beam widths in the azimuth and / or elevation dimensions, different frequencies / wavelengths, different phases, different amplitudes, different powers, and / or the data symbols may be carried on different subcarriers. In addition, the WTRU may provide feedback to the transmitter of the beam, and the feedback allows the transmitter to adjust the transform extension function and / or one or more parameters of the beam.

[0433] Although the features and elements are described above in specific combinations, those of ordinary skill in the art will understand that each feature or element may be used alone or in any combination with other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated into a computer-readable medium for execution by a computer or a processor. Examples of computer-readable media include electronic signals (sent 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 storage 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)). The processor associated with the software may be used to implement the radio frequency transceiver used in the WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A method capable of being implemented by a WTRU, the method comprising: Applying a transform spreading function that spreads the data symbol in the frequency domain to the data symbol; Forming a first beam; And Transmitting the transform-spread data symbol in the first beam.

2. The method according to claim 1, further comprising: Generating a complex conjugate of the transform-spread data symbol; Forming a second beam; And Transmitting the transform-spread complex conjugate in the second beam.

3. The method according to claim 2, wherein: The first beam includes a main beam; and The second beam includes a diversity beam.

4. The method according to claim 2, wherein: Transmitting the transform-spread data symbol in the first beam includes transmitting the transform-spread data symbol on a first channel having a first channel response; And Transmitting the transform-spread complex conjugate in the second beam includes transmitting the complex conjugate of the transform-spread data symbol on a second channel having a second channel response.

5. The method according to claim 2, wherein generating the complex conjugate includes generating the complex conjugate with and without a sign inversion operation.

6. The method according to claim 2, further comprising Alamouti coding the transform-spread data symbol and the complex conjugate of the transform-spread data symbol.

7. The method according to claim 1, further comprising transmitting an untransformed control symbol in the first beam.

8. The method according to claim 2, further comprising transmitting an untransformed control symbol in the second beam.

9. The method according to claim 1, wherein transmitting the transform-spread data symbol in the first beam includes modulating subcarriers of the first beam with the transform-spread data symbol.

10. The method according to claim 2, wherein transmitting the complex conjugate of the transform-spread data symbol in the second beam includes modulating subcarriers of the second beam with the complex conjugate of the transform-spread data symbol.

11. The method according to claim 1, further comprising transmitting an indication of the transform spreading function.

12. The method according to claim 2, further comprising transmitting an indication of the second beam.

13. The method according to claim 1, further comprising receiving a request to improve beam resilience in response to a triggering event.

14. The method according to claim 13, wherein the triggering event includes the speed of the received WTRU being equal to or exceeding a speed threshold, the performance degradation due to beam squint being equal to or exceeding a beam squint performance threshold, and / or the performance degradation due to beam misalignment being equal to or exceeding a misalignment performance threshold.

15. The method according to claim 1, further comprising adjusting the transform spreading function in response to a receiver of the transform-spread data symbol in the first beam.

16. The method according to claim 1, further comprising adjusting the first beam in response to a receiver of the transform-spread data symbol in the first beam.

17. The method according to claim 2 further comprises adjusting the transform spreading function in response to a receiver of the transformed and spread data symbol in the first beam and / or the complex conjugate of the transformed and spread data symbol in the second beam.

18. The method according to claim 2 further comprises adjusting the first beam and / or the second beam in response to a receiver of the transformed and spread data symbol in the first beam and the complex conjugate of the transformed and spread data symbol in the second beam.

19. A WTRU configured to: Apply a transform spreading function that spreads the data symbol in the frequency domain to the data symbol; Form a first beam; and Transmit the transformed and spread data symbol in the first beam.

20. The WTRU according to claim 19, further configured to: Generate a complex conjugate of the transformed and spread data symbol; Form a second beam; and Transmit the complex conjugate of the transformed and spread data symbol in the second beam.

21. The WTRU according to claim 20, wherein: The first beam includes a main beam; and The second beam includes a diversity beam.

22. The WTRU according to claim 20, configured to: Transmit the transformed and spread data symbol in the first beam by transmitting the transformed and spread data symbol on a first channel having a first channel response; and Transmit the complex conjugate of the transformed and spread data symbol in the second beam by transmitting the complex conjugate of the transformed and spread data symbol on a second channel having a second channel response.

23. The WTRU according to claim 20, configured to generate the complex conjugate by generating the complex conjugate with and without a sign inversion operation.

24. The WTRU according to claim 20, further configured to perform Alamouti coding on the transformed and spread data symbol and the complex conjugate of the transformed and spread data symbol.

25. The WTRU according to claim 20, further configured to transmit an untransformed and spread control symbol in the first beam.

26. The WTRU according to claim 20, further configured to transmit an untransformed and spread control symbol in the second beam.

27. The WTRU according to claim 19, configured to transmit the transformed and spread data symbol in the first beam by modulating subcarriers of the first beam with the transformed and spread data symbol.

28. The WTRU according to claim 20, configured to transmit the complex conjugate of the transformed and spread data symbol in the second beam by modulating subcarriers of the second beam with the complex conjugate of the transformed and spread data symbol.

29. The WTRU according to claim 19, further configured to transmit an indication of the transform spreading function.

30. The WTRU according to claim 20, further configured to transmit an indication of the second beam.

31. The WTRU according to claim 19 is further configured to receive a request to improve beam flexibility in response to a triggering event.

32. The WTRU according to claim 31, wherein the triggering event includes the speed of the WTRU being equal to or exceeding a speed threshold, the performance degradation caused by beam skew being equal to or exceeding a beam skew performance threshold, and / or the performance degradation caused by beam misalignment being equal to or exceeding a misalignment performance threshold.

33. The WTRU according to claim 19 is further configured to adjust the transform spread function in response to a receiver of the transform spread data symbol in the first beam.

34. The WTRU according to claim 19 further includes adjusting the first beam in response to a receiver of the transform spread data symbol in the first beam.

35. A method that can be implemented by a WTRU, the method comprising: receiving, in a first beam, the data symbol to which a transform spread function that spreads data symbols in the frequency domain has been applied; receiving, in a second beam, the complex conjugate of the transform spread data symbol; combining the received transform spread data symbol and the complex conjugate of the received transform spread data symbol; and recovering the data symbol by applying the inverse of the transform spread function to the combination of the received transform spread data symbol and the complex conjugate of the received transform spread data symbol.

36. The method according to claim 35, wherein: the first beam includes a main beam; and the second beam includes a diversity beam.

37. The method according to claim 35, wherein: receiving the transform spread data symbol in the first receive beam includes receiving the transform spread data symbol on a first channel having a first channel response; receiving the complex conjugate in the second beam includes receiving the complex conjugate on a second channel having a second channel response; and recovering the data symbol includes recovering the data symbol by: weighting the transform spread data symbol received in the first beam and the complex conjugate of the transform spread data symbol received in the second beam with the first channel response and the second channel response, combining the weighted transform spread data symbol and the weighted complex conjugate, and applying the inverse of the transform spread function to the combination of the weighted transform spread data symbol and the weighted complex conjugate.

38. The method according to claim 35, wherein: receiving the transform spread data symbol in the first receive beam includes receiving the transform spread data symbol on a first channel having a first channel response; receiving the complex conjugate of the transform spread data symbol in the second beam includes receiving the complex conjugate on a second channel having a second channel response; and recovering the data symbol includes recovering the data symbol by: Weight the complex conjugates of the transformed spread data symbols received in the first beam and the transformed spread data symbols received in the second beam with the first channel response and the second channel response, Based on the Alamouti combination of the weighted transformed spread data symbols and the weighted complex conjugates, and Apply the inverse of the transform spread function to the Alamouti-based combination of the weighted transformed spread data symbols and the weighted complex conjugates.

39. The method according to claim 35, further comprising: Receiving a first control symbol in the first beam to which the transform spread function has not been applied; And Receiving a second control symbol in the second beam to which the transform spread function has not been applied.

40. The method according to claim 35, further comprising: Receiving a first control symbol in the first beam to which the transform spread function has not been applied; Receiving a second control symbol in the second beam to which the transform spread function has not been applied; and Recovering the first control symbol and the second control symbol without applying the inverse transform spread function to the first control symbol and the second control symbol.

41. The method according to claim 35, wherein receiving the complex conjugate of the data symbol in the second beam includes receiving the complex conjugate with and without a sign inversion operation.

42. The method according to claim 35, wherein: The transformed spread data symbols are carried by subcarriers of the first beam; and The complex conjugate of the transformed spread data symbols is carried by subcarriers of the second beam.

43. The method according to claim 35, further comprising receiving an indication of the transform spread function.

44. The method according to claim 35, further comprising receiving an indication of the second beam.

45. The method according to claim 35, further comprising sending a request to improve beam resilience in response to a triggering event.

46. The method according to claim 45, wherein the triggering event includes the speed of the WTRU being equal to or exceeding a speed threshold, the performance degradation due to beam skew being equal to or exceeding a beam skew performance threshold, and / or the performance degradation due to beam misalignment being equal to or exceeding a misalignment performance threshold.

47. The method according to claim 35, further comprising transmitting feedback regarding the transform spread function, the first beam, and / or the second beam to a transmitter of the first beam and the second beam.

48. A WTRU configured to: Receive the data symbols in a first beam to which a transform spread function that spreads the data symbols in the frequency domain has been applied; Receive the complex conjugate of the transformed spread data symbols in a second beam; Combine the transformed spread data symbols and the complex conjugate of the transformed spread data symbols; and Recover the data symbols by applying the inverse of the transform spread function to the combination of the transformed spread data symbols and the complex conjugate of the transformed spread data symbols.

49. The WTRU according to claim 48, wherein: the first beam includes a main beam; and the second beam includes a diversity beam.

50. The WTRU according to claim 48, wherein the WTRU is configured to: receive the transformed and extended data symbol in the first receive beam by receiving the transformed and extended data symbol on a first channel having a first channel response; receive the complex conjugate of the transformed and extended data symbol in the second beam by receiving the complex conjugate of the transformed and extended data symbol on a second channel having a second channel response; and recovering the data symbol includes recovering the data symbol by weighting the transformed and extended data symbol received in the first beam and the complex conjugate of the transformed and extended data symbol received in the second beam with the first channel response and the second channel response, combining the weighted transformed and extended data symbol and the weighted complex conjugate, and applying the inverse of the transform extension function to the combination of the weighted transformed and extended data symbol and the weighted complex conjugate.

51. The WTRU according to claim 48, wherein the WTRU is configured to: receive the transformed and extended data symbol in the first receive beam by receiving the transformed and extended data symbol on a first channel having a first channel response; receive the complex conjugate in the second beam by receiving the complex conjugate of the transformed and extended data symbol on a second channel having a second channel response; and recover the data symbol by: weighting the transformed and extended data symbol received in the first beam and the complex conjugate of the transformed and extended data symbol received in the second beam with the first channel response and the second channel response, combining the weighted transformed and extended data symbol and the weighted complex conjugate based on Alamouti, and applying the inverse of the transform extension function to the Alamouti-based combination of the weighted transformed and extended data symbol and the weighted complex conjugate of the transformed and extended data symbol.

52. The WTRU according to claim 48, further configured to: receive a first control symbol in the first beam to which the transform extension function has not been applied; and receive a second control symbol in the second beam to which the transform extension function has not been applied.

53. The WTRU according to claim 48, further configured to: receive a first control symbol in the first beam to which the transform extension function has not been applied; receive a second control symbol in the second beam to which the transform extension function has not been applied; and recover the first control symbol and the second control symbol without applying the inverse transform extension function to the first control symbol and the second control symbol.

54. The WTRU according to claim 48, wherein the WTRU is configured to receive the complex conjugate of the transform - extended data symbol in the second beam by receiving the complex conjugate of the transform - extended data symbol generated at the transmitter with and without a sign - inversion operation.

55. The WTRU according to claim 48, wherein: the transform - extended data symbol is carried by a sub - carrier of the first beam; and the complex conjugate of the transform - extended data symbol is carried by a sub - carrier of the second beam.

56. The WTRU according to claim 48, further configured to receive an indication of the transform - extension function.

57. The WTRU according to claim 48, further configured to receive an indication of the second beam.

58. The WTRU according to claim 48, further configured to send a request to improve beam resilience in response to a trigger event.

59. The WTRU according to claim 58, wherein the trigger event includes the speed of the WTRU being equal to or exceeding a speed threshold, the performance degradation caused by beam skew being equal to or exceeding a beam - skew performance threshold, and / or the performance degradation caused by beam misalignment being equal to or exceeding a misalignment performance threshold.

60. The WTRU according to claim 58, further configured to convey feedback regarding the transform - extension function, the first beam, and / or the second beam to the transmitters of the first beam and the second beam.

61. A method executable by a WTRU, the method comprising: forming a first beam and a second beam; transmitting a first data symbol in the first beam; and transmitting a second data symbol in the second beam.

62. The method according to claim 61, wherein: transmitting the first data symbol includes modulating a first sub - carrier in the first beam with the first data symbol; and transmitting the second data symbol includes modulating a second sub - carrier in the second beam with the second data symbol.

63. The method according to claim 61, wherein the second data symbol is the complex conjugate of the first data symbol.

64. The method according to claim 61, wherein: the first beam is a main beam; and the second beam is a diversity beam.

65. A WTRU configured to: form a first beam and a second beam; transmit a first data symbol in the first beam; and transmit a second data symbol in the second beam.

66. The WTRU according to claim 65, configured to: transmit the first data symbol by modulating a first sub - carrier in the first beam with the first data symbol; and transmit the second data symbol by modulating a second sub - carrier in the second beam with the second data symbol.

67. The WTRU according to claim 65, wherein the second data symbol is the complex conjugate of the first data symbol.

68. The WTRU according to claim 65, wherein: the first beam is a main beam; and The second beam is a diversity beam.

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