Method executed by wireless transmit / receive unit (WTRU)

Abstract

The disclosure relates to a method performed by a wireless transmit / receive unit (WTRU). The method comprises: receiving a physical downlink control channel (PDCCH) transmission from a first transmit / receive point (TRP); receiving a first repetition of a physical downlink shared channel (PDSCH) transmission from the first TRP based on the PDCCH transmission; and receiving a second repetition of the PDSCH transmission from a second TRP based on the PDCCH transmission.

Description

[0001] This application is a divisional application of the invention patent application with the application date of January 8, 2020, application number: 202080011137.0, and invention name: "Method and device for reliable multi-transmission system".

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Application No. 62 / 790,347, filed January 9, 2019, and U.S. Provisional Application No. 62 / 805,154, filed February 13, 2019, the contents of which are incorporated herein by reference. Background Art

[0004] In New Radio (NR), multiple transmit / receive point (MTRP) operation is supported with an initial focus on downlink transmissions. A NR wireless transmit / receive unit (WTRU) may be able to receive and process multiple transmissions via transport channels such as the physical downlink control channel (NR-PDCCH) and the physical downlink shared channel (NR-PDSCH). Two scenarios of downlink MTRP operation are presented, where "P-TRP" and "S-TRP" refer to the primary TRP and the secondary TRP, respectively. In the first scenario, a single DCI transmission on the NR-PDCCH may schedule a single downlink transmission on the NR-PDSCH, for which a separate layer may be transmitted from a separate TRP. In the second scenario, multiple NR-PDCCHs may each schedule a corresponding NR-PDSCH, and each NR-PDSCH may be transmitted from a separate TRP. One focus of NR is to support two NR-PDSCH transmissions on a component carrier basis in the case of one bandwidth portion, and corresponding two NR-PDCCH transmissions in a single time slot.

[0005] One benefit of scenario 1 may be that despite transmitting multiple NR-PDSCH data layers, the complexity of the WTRU blind search for DCI (downlink control information) decoding remains similar to the legacy system since the WTRU may only need to decode one transmission received using NR-PDCCH. However, scheduling decisions may be centrally coordinated at one gNB, requiring coordination between multiple TRPs. Also, a beam link failure at the primary coordinating TRP may affect transmissions at other TRPs since the WTRU may receive control information for all TRPs in the coordination set from one TRP.

[0006] In scenario 2, the use of multiple NR-PDCCHs to send multiple DCIs can result in greater scheduling flexibility at the TRP. Each NR-PDCCH transmission can carry different scheduling instructions for the WTRU without being affected by non-ideal backhaul. Therefore, less information may need to be exchanged between cooperating TRPs via the backhaul. In addition, distributed scheduling provides diversity because a beam link failure at one TRP only affects the resources it manages; transmissions at other TRPs can continue without any interruption. This can be an important factor for URLLC applications. On the other hand, since the WTRU may need to perform blind detection on multiple received NR-PDCCHs, the effective size of the search space can be increased. Coordination maintains an important aspect of the operation for preventing collisions of NR-PDCCHs transmitted by multiple TRPs.

[0007] Furthermore, in NR Release 15 Ultra-Reliable Low Latency Communications (URLLC), PDSCH / PUSCH repetition and transmission based on lower coding rates are specified. However, due to the limited achieved gains and the implications for delays incurred by excessive repetitions, further enhancements may still be needed. Summary of the invention

[0008] Methods and apparatus for enhancing transmission reliability are described herein.

[0009] In one aspect, the present disclosure provides a method performed by a wireless transmit / receive unit WTRU, the method comprising: receiving a physical downlink control channel PDCCH transmission from a first transmit / receive point TRP; based on the PDCCH transmission, receiving a first repetition of a physical downlink shared channel PDSCH transmission from the first TRP; and based on the PDCCH transmission, receiving a second repetition of the PDSCH transmission from a second TRP.

[0010] In one aspect, the method provided by the present disclosure may include determining multiple repetitions of transmitting a data payload. Each repetition of the data payload may include a set of coded bit sequences. The method may also include determining a constellation for each of the repetitions of the data payload, and for each repetition of the data payload, mapping the set of coded bit sequences to a corresponding set of modulation symbols using the constellation. Each of the sets of modulation symbols may be different. The method may also include allocating time and frequency resources for transmitting the set of modulation symbols, and transmitting the set of modulation symbols on a downlink channel using the allocated time and frequency resources. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0012] Figure 1A is a system diagram illustrating an exemplary communication system in which one or more disclosed embodiments may be implemented;

[0013] Figure 1B It is shown that according to one embodiment, Figure 1A A system diagram of an exemplary wireless transmit / receive unit (WTRU) for use within the communication system shown;

[0014] Figure 1C It is shown that according to one embodiment, Figure 1A A system diagram of an exemplary radio access network (RAN) and an exemplary core network (CN) used within the illustrated communication system;

[0015] Figure 1D It is shown that according to one embodiment, Figure 1A A system diagram of another exemplary RAN and another exemplary CN used in the communication system shown;

[0016] Figure 2 are diagrams showing two exemplary scenarios of MTRP operation;

[0017] Figure 3 A basic mechanism for enhancing transmission reliability involving transmission of multiple repetitions is shown;

[0018] Figure 4 shows a transmission scheme in which the modulation scheme changes for each consecutive repetition;

[0019] Figure 5 is a block diagram providing an overview of the transport channel processing, which includes Figure 4 The multi-dimensional modulation process provided in;

[0020] Figure 6 An exemplary solution for a high reliability transmission solution based on four repetitions is shown, where only two constellation mapping options are considered for retransmissions;

[0021] Figure 7 A transmission scheme is shown in which the bit-to-symbol mapping of the modulation function changes for each consecutive repetition;

[0022] Figure 8 is a block diagram providing an overview of the transport channel processing, which includes Figure 7 The multi-dimensional modulation process provided in;

[0023] Fig. 9 An exemplary multi-TRP transmission scheme involving two TRPs and using multi-dimensional modulation is shown, where each TRP uses an orthogonal set of resources;

[0024] Fig.10 An exemplary multi-TRP transmission scheme involving two TRPs and using multi-dimensional modulation is shown, where the TRPs use the same set of resources;

[0025] Fig.11 An exemplary case of a multi-TRP transmission with four repetitions is shown, where only two constellation mappings are considered;

[0026] FIG. 12A to FIG. 12M Potential constellation solutions for a system with N=2 dimensions are shown;

[0027] FIG. 13A to FIG. 13C Shows the use of FIG. 12A to FIG. 12M Multiple transport protocol options are presented to achieve performance enhancements. DETAILED DESCRIPTION

[0028] Figure 1A 1 is a schematic diagram illustrating an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through sharing of system resources (including wireless bandwidth). For example, the communication system 100 may employ one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multi-carrier (FBMC), etc.

[0029] like Figure 1AAs 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, but it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a station (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, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0030] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device that is configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a NodeB, an evolved NodeB (eNB), a Home NodeB, a Home evolved NodeB, a next generation NodeB such as a gNodeB (gNB), a new radio (NR) NodeB, a site controller, an access point (AP), a wireless router, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0031] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), a relay node, etc. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrums. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, a cell associated with the base station 114a may be divided into three sectors. Therefore, in one embodiment, the base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In one embodiment, the base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

[0032] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0033] More specifically, as noted above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 116. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​Uplink (UL) Packet Access (HSUPA).

[0034] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0035] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using NR.

[0036] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for example using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0037] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), GSM Enhanced Data Rates for Evolution (EDGE), GSM EDGE (GERAN), etc.

[0038] Figure 1AThe base station 114b in the may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a business location, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or a femtocell. As Figure 1A As shown, the base station 114 b may have a direct connection to the Internet 110. Therefore, the base station 114 b may not need to access the Internet 110 via the CN 106.

[0039] The RAN 104 may be in communication 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 different quality of service (QoS) requirements, such as different throughput requirements, delay requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not described in detail in the specification, the CN 106 may be configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. Figure 1A Although not shown in the figure, it will be appreciated that the RAN 104 and / or the CN 106 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may utilize NR radio technology, the CN 106 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0040] The CN 106 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

[0041] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0042] Figure 1B is a system diagram illustrating an exemplary WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any subcombination of the foregoing elements while remaining consistent with an embodiment.

[0043] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functions that enable the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0044] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) via an air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be a transmitter / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive RF and light signals. It should be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0045] Although the transmit / receive element 122 is Figure 1B 1 as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0046] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0047] The processor 118 of the WTRU 102 may be coupled to a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit) and may receive user input data therefrom. The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any type of suitable memory, such as a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from and store data in a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0048] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power to other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0049] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0050] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, Module, FM radio unit, digital music player, media player, video game player module, Internet browser, virtual reality and / or augmented reality (VR / AR) device, activity tracker, etc. Peripheral device 138 may include one or more sensors. The sensor may be one or more of the following: gyroscope, accelerometer, Hall effect sensor, magnetometer, orientation sensor, proximity sensor, temperature sensor, time sensor; geographic location sensor, altimeter, light sensor, touch sensor, magnetometer, barometer, gesture sensor, biometric sensor, humidity sensor, etc.

[0051] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for 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 for reducing and / or substantially eliminating self-interference via hardware (e.g., choke) or via signal processing performed by a processor (e.g., a separate processor (not shown) or via the processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) or DL ​​(e.g., for reception)) may be concurrent and / or simultaneous.

[0052] Figure 1C 1 is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As described above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0053] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0054] Each of the evolved Node Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0055] 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 foregoing elements are depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0056] The MME 162 may be connected to each of the evolved Node-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, etc. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0057] The SGW 164 may be connected to each of the evolved Node-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during inter-evolved Node-B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, and the like.

[0058] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0059] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0060] Although the WTRU Figures 1A to 1D Although described as a wireless terminal, it is contemplated that in certain representative embodiments such a terminal may (eg, temporarily or permanently) employ a wired communications interface with a communications network.

[0061] In a representative embodiment, the other network 112 may be a WLAN.

[0062] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for a BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or carries traffic away from the BSS. Traffic originating from outside the BSS and leading to the STA may be reached by the AP and may be delivered to the STA. Traffic originating from the STA and leading to a destination outside the BSS may be sent to the AP to be delivered to the corresponding destination. Traffic between STAs within the BSS may be sent by the AP, for example, wherein the source STA may send traffic to the AP, and the AP may deliver traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic may be sent between the source and destination STAs (e.g., directly between them) using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs (eg, all STAs) within or using the IBSS may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad-hoc" communication mode.

[0063] When using the 802.11ac infrastructure operating mode or a similar operating mode, the AP may transmit a beacon on a fixed channel (such as a primary channel). The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a dynamically set width. The primary channel may be an operating channel of the BSS and may be used by the STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including the AP) may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0064] High throughput (HT) STAs may communicate using a 40 MHz wide channel, for example, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0065] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz and / or 80MHz channels can be formed by combining continuous 20MHz channels. A 160MHz channel can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For the 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and data can be transmitted by transmitting STA. At the receiver of the receiving STA, the above-mentioned operation for the 80+80 configuration can be reversed, and the combined data can be sent to the medium access control (MAC).

[0066] 802.11af and 802.11ah support operating modes below 1GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support meter type control / machine type communication (MTC), such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0067] WLAN systems that can support multiple channels and channel bandwidths such as 802.11n, 802.11ac, 802.11af, and 802.11ah include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA (which supports the minimum bandwidth operating mode) from all STAs operating in the BSS. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (supporting only the 1MHz operating mode) is transmitting to the AP, all available frequency bands may be considered busy even if most of the available frequency bands remain idle.

[0068] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0069] Figure 1D 1 is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As noted above, the RAN 104 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0070] The RAN 104 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 104 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may, for example, use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a. In one embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation techniques. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum, while the remaining component carriers may be on licensed spectrum. In one embodiment, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) techniques. For example, the WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0071] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable parameter sets. For example, OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of varying or scalable lengths (e.g., containing different numbers of OFDM symbols and / or continuously varying absolute time lengths).

[0072] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c while also not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate or connect with the gNBs 180a, 180b, 180c while also communicating or connecting with other RANs, such as the eNode-Bs 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more evolved Node-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the evolved Node-Bs 160a, 160b, 160c may serve as mobility anchors for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0073] Each of the gNBs 180a, 180b, 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, support of network slicing, interworking between DC, NR, and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b, routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0074] Figure 1DThe illustrated CN 106 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possible data networks (DNs) 185a, 185b. Although the aforementioned elements are depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0075] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c via the N2 interface in the RAN 104 and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of non-access stratum (NAS) signaling, mobility management, etc. The AMF 182a, 182b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c based on the type of services used by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced mobile broadband (eMBB) access, services for MTC access, etc. The AMF 182a, 182b may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as WiFi.

[0076] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 106 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 106 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating WTRU 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.

[0077] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via the N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, etc.

[0078] The CN 106 may facilitate communications with other networks. For example, the CN 106 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to the DNs 185a, 185b via the UPFs 184a, 184b via the N3 interfaces to the UPFs 184a, 184b and the N6 interfaces between the UPFs 184a, 184b and the local DNs 185a, 185b.

[0079] Given that Figures 1A to 1D as well as Figures 1A to 1D Corresponding to the description of the present invention, one or more or all of the functions described herein with reference to one or more of the following may be performed by one or more simulation devices (not shown): WTRU102a-d, base station 114a-b, evolved Node B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b and / or any other device described herein. The simulation device may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the simulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0080] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, the one or more simulation devices may 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. The one or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device may be directly coupled to another device for testing purposes and / or perform testing using over-the-air wireless communications.

[0081] The one or more simulation devices may perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device may be used in a test scenario in a test lab and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. The one or more simulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuits (e.g., which may include one or more antennas) may be used by the simulation device to transmit and / or receive data.

[0082] In order to enhance the reliability and robustness of transmission, the overall transmission strategy should make better use of diversity. The concept of transmission diversity can include various aspects, such as diversity in the space domain and the time domain. However, simple space diversity and time diversity alone may not be sufficient to achieve high reliability transmission. In the present disclosure, solutions to several problems related to multi-transmission systems are provided.

[0083] Figure 2 A background is provided for improving the utilization of transmit diversity through MTRP operation. Two options for downlink MTRP operation are provided. Figure 2 As shown, P-TRP 201 and S-TRP 202 refer to primary TRP and secondary TRP, respectively. In the first scenario, a single NR-PDCCH 211 schedules a single NR-PDSCH transmission, which involves transmitting separate layers or repetitions 221 and 222 from separate TRPs 201 and 202, respectively. In the second scenario, multiple NR-PDCCHs 211 and 212 each schedule a corresponding NR-PDSCH 221 and 222, for which each NR-PDSCH repetition 221 and 222 is transmitted from a separate TRP 201 and 202. Wireless technologies such as NR can support two NR-PDSCHs on a per component carrier basis in the case of one bandwidth portion, and corresponding two NR-PDCCHs in a single time slot.

[0084] Although the above embodiments are described in the context of NR wireless technology, i.e., using a physical downlink shared channel and a control channel for transmission, other types of wireless technology may be used to implement the enhancements described herein, and various other types of channels may conceivably be used for transmission and / or scheduling repetitions.

[0085] Enhancements to the transmission protocol can be implemented in the above-mentioned MTRP scheme. The enhancements achieved by reusing the basic protocol based on the transmitted signal can be limited. Such transmission protocols may or may not take into account other signal characteristics and attributes. Enhancements to the signal design of the above-mentioned MTRP scheme can also be applied to improve transmission diversity. In order to improve the transmission protocol, the signal design can be adjusted according to the additional transmission.

[0086] In the following disclosure, the term "reference symbol" may be used to refer to a symbol, such as a complex number that is fixed, known and used as a pilot. "Reference signal" may be used to refer to a time domain signal generated after processing the reference symbol. For example, in OFDM, the reference symbol may be a complex number fed into an IDFT block, and the reference signal may be the output of the IDFT block. "Downlink control information" (DCI) may refer to a collection of bits transmitted for one user or a group of users via a PDCCH. "Resource element" (RE) may refer to one OFDM symbol on one subcarrier, and "resource element group" (REG) may refer to a group of REs used as building blocks for control channel elements (CCEs) that allocate resource elements to users. REGs that are adjacent in time or frequency and that share an associated precoder may be referred to as REG "bundles". Here in the present disclosure, NR-REG, NR-CCE, and NR-PDCCH refer to REGs, CCEs, and PDCCHs for new radio (NR) in 5G. In addition, herein, WTRU, user equipment (UE), and user are used interchangeably and refer to the same thing. Additionally, "gNodeB" and "gNB" may refer to the same thing. A "Control Resource Set" (CORESET) may refer to a set of resource elements used for downlink control channels, configured by its frequency resource and its temporal length (in terms of symbols) and the type of its REG bundle. A "search space" (or set of search spaces) is a set of PDCCH candidates that are monitored by a WTRU or a group of WTRUs during blind detection of the PDCCH.

[0087] In the following, the term "retransmission" may be used interchangeably with "repeated transmission", "repetition" and "aggregate transmission". In addition, the term "retransmission number" may be used interchangeably with "retransmission index", "retransmission time", "retransmission order" and "retransmission sequence number".

[0088] Figure 3A basic repetition mechanism for enhancing transmission reliability is shown, wherein each retransmission is a replica of the first transmission using the same modulation and symbol mapping. Repetition can be implemented in the same time slot or across several time slots. For example, as shown, a period 300 of a single transmission can be composed of time slots 301, 302, 303, and 304. Within such time slots, transmissions 312, 313, and 314 can be retransmissions or repetitions of transmission 311. Retransmissions 312, 313, and 314 can be sent, for example, using the same timing symbol numbering as in time slot 301 in consecutive time slots 302, 303, and 304.

[0089] In a solution, the TRP may use multi-dimensional modulation by employing different constellation mappings for one or more retransmissions. The WTRU may be configured to decipher the modulated transmission based on the constellation mapping. Thus, upon receiving a transmission implementing such a multi-dimensional modulation scheme, the WTRU may use logic similar to that required to process and modulate the data payload. For example, as described below, the WTRU may detect one or more transport layers, determine the constellation mapping, demodulate and process a set of modulated symbols to obtain a set of coded bit sequences. The logic used may vary depending on the scheme used to transmit the data payload on the TRP side.

[0090] A constellation map may provide a graphical representation of a digital signal modulation scheme. In an example, a constellation map may be presented as a two-dimensional scattering plane, where the angle of a constellation point measured from the positive x-axis may indicate a phase shift of a modulation symbol, and the distance of the constellation point from the origin may represent another modulation variable, such as amplitude or power. A series of data bits may be mapped to a constellation point representing a modulation symbol.

[0091] Figure 4 and Figure 5 A specific implementation of a high reliability transmission process is shown, wherein the bit-to-symbol mapping of the modulation function is adjusted for each retransmission. Specifically, Figure 4 A transmission repetition mechanism is shown, where the modulation scheme varies according to different constellations 401, 402, 403, and 404. The constellation mapping for each transmission can be designed to enhance detection capabilities by maximizing distance metrics such as vector distance, Euclidean distance, product distance, etc., and by employing different symbol mapping methods (e.g., Gray coding). Figure 4 As shown, for an exemplary transmission of the "0011" bits, different 16QAM symbols can be used to improve the detection probability by providing additional transmission diversity. For each transmission 411, 412, 413, and 414, the position of the mapped bit sequence "0011" within each of its corresponding constellations 401, 402, 403, and 404 can be shifted to a point corresponding to the new symbol.

[0092] Figure 5An overview of transport channel processing is provided, including a multidimensional modulation process that can be implemented in the above-mentioned retransmission process. At 501, data can flow from the medium access (MAC) layer to the physical layer for transmission via a transport channel. Data can be delivered to the physical layer in a transport block, for which a cyclic redundancy code can be calculated and attached. The transport block can be converted into a single code block or segmented into multiple code blocks. At 502, the transport block can be encoded for error correction purposes. Forward error correction (FEC) can be performed using various methods, including low-density parity check coding or turbo coding. Bit-to-symbol mapping can occur at 503, thereby converting the coded bits into modulation symbols for transmission. At 504 and 505, the modulation symbols can be distributed on available resources and precoded for transmission via one or more antennas.

[0093] like Figure 5 As shown, the retransmission counter 506 may be incremented for each consecutive retransmission / repetition. In an embodiment where the constellation mapping is determined based on the retransmission / repetition index, for example, the constellation and therefore the above-mentioned bit-to-symbol mapping may therefore change for each retransmission. In the solution, the resource mapping of each retransmission with a new symbol mapping may also change for each repetition index. In addition, each retransmission with a new constellation mapping may be combined with a different beam or precoder.

[0094] In some solutions, the constellation for each subsequent repetition may be based on a rotated version of the constellation mapping used for the first transmission. The WTRU device may assume the applied rotation for each repetition based on a previous configuration, or based on one or more other parameters such as: maximum repetition factor K, time index, beam index, etc. In other solutions, instead of using a different constellation mapping for each subsequent transmission, a limited number of different constellation mappings may be used to determine the modulation symbols for the subsequent transmissions. The WTRU may also use a limited number of constellation mappings, which may, for example, avoid additional complexity.

[0095] Figure 6 An exemplary solution of a high reliability transmission solution based on four repetitions is shown, where only two constellation mapping options are considered for retransmissions. As shown, repetitions can be transmitted in TTIs 601, 602, 603, and 604, and one of the two constellation mappings can be applied to each TTI in an alternating manner. Each repetition transmitted in a given TTI can be transmitted using a different physical resource band (PRB).

[0096] The WTRU may determine the constellation mapping for each retransmission based on a received semi-static or dynamic indication. For a solution in which K repetitions are to be transmitted, the WTRU may be configured with one or more options for the constellation mapping sequence, i.e., {C1, C2, …, C K}, where each sequence can be referred to by an index.

[0097] Alternatively, the WTRU may determine the constellation mapping for each retransmission based on one or more parameters such as a time transmission index, e.g., symbol number, slot number, frame number, or transmission number. For example, the WTRU may assume that a baseline constellation mapping is used for odd transmission occasions (e.g., slots), and the WTRU may also assume that a secondary constellation mapping is used for even transmission occasions. The baseline constellation mapping may be pre-configured at the WTRU or received via a semi-static or dynamic indication. The baseline constellation mapping may also be predetermined for a wireless technology such as NR.

[0098] In the solution, a bit interleaver may be used for each retransmission, which may result in different constellation points and, therefore, modulation symbols (for each retransmission). For example, one or more bit interleavers may be used, and each bit interleaver may be identified by an index. Hereinafter, an "index" may also be referred to as an "interleaver index", "bit interleaver index", "bit map index", "bit scrambling sequence index", and / or "bit ordering index".

[0099] Figure 7 and Figure 8 A specific implementation of a high reliability transmission process is shown, wherein the bit-to-symbol mapping of the modulation function is adjusted for each retransmission. Specifically, Figure 7 A transmission repetition mechanism is shown in which the modulation scheme is changed by applying an interleaver to the coded bit sequence before mapping the interleaved bit sequence to the existing constellations 701, 702, 703, and 704. Thus, for each transmission 711, 712, 713, and 714, the position of the interleaved bit sequence within each of the constellations 701, 702, 703, and 704 may be shifted to a point corresponding to the new symbol.

[0100] Similar to Figure 6 , Figure 8 A basic overview of transport channel processing is provided, including multi-dimensional modulation that can be implemented in the above retransmission process. Transport channel processing can be as follows: Figure 6 The substantially similar manner described above is performed. At 801, data may flow from the medium access (MAC) layer to the physical layer for transmission via a transport channel. At 802, the transport block may be FEC encoded for error correction purposes. Bit to symbol mapping may occur at 803, thereby converting the coded bits into modulation symbols for transmission. As described above, during bit to symbol mapping, an interleaver may be used to change the modulation symbols to be transmitted in continuous repetitions. In an embodiment, this may be performed instead of using different constellations for transmission, or it may be performed in addition to generating different constellations. At 804 and 805, the modulation symbols may be distributed on available resources and precoded for transmission via one or more antennas.

[0101] In some cases, the bit interleaver index for the downlink transmission may be determined based on the retransmission or repetition number. For example, the first bit interleaver may be used for the first retransmission, the second bit interleaver may be used for the second retransmission, and so on.

[0102] The bit interleaver size may be the same as the number of bits used for the modulation symbol. The number of bits used for the modulation symbol may depend on the order of the modulation scheme, for example, four bits may be used to represent a symbol in a 16QAM scheme. Thus, if the modulation order used for downlink transmission is 16QAM, a four-bit interleaver may be used, and the bit interleaver may be used for each bit sequence formed for the modulation symbol.

[0103] The bit interleaver can perform various transformations on a bit sequence or group to form a modulation symbol, such as cyclic shift, mirroring, or bit reversal. In an example assuming a 16QAM scheme, if a modulation symbol pair with 16QAM is represented as [c n ,c n+1 ,c n+2 ,c n+3 ], the bit interleaver can change the order of the bit sequence so that the resulting bit sequence is [c n+1 ,c n+2 ,c n+3 ,c n ], or for a mirror transformation [c n+3 ,c n+2 ,c n+1 ,c n ].

[0104] A bit interleaver index for a downlink transmission may be determined based on a TRP index, which may be associated with the downlink transmission. The TRP index may be determined or indicated by a channel state information reference signal (CSI-RS) and / or a synchronization signal block (SSB) associated with a demodulation reference signal (DMRS) quasi collocated (QCL-ed) with a channel (e.g., PDSCH).

[0105] The bit interleaver index for the downlink transmission may be determined based on one or more system parameters including, but not limited to, a time slot number, a subframe number, an orthogonal frequency division multiplexing (OFDM) symbol number, a bandwidth part (BWP) index, a carrier index, or a resource block index.

[0106] In one embodiment, the use of the bit interleaver based on the retransmission number can be determined based on the modulation order. For example, if the modulation order is equal to or less than a threshold (e.g., QPSK), the same bit interleaving scheme can be used for all retransmissions. In other scenarios, such as when the modulation order is greater than a threshold, the bit interleaving scheme can be changed, for example, based on the transmission index. The threshold can be determined based on the number of retransmissions (or repetitions) of a single PDSCH transmission (e.g., without HARQ retransmissions).

[0107] In another solution, a two-step interleaver can be used for each retransmission. For example, a first interleaver can be used for each of the bit sequences grouped to form a modulation symbol, and a second interleaver can be used for the modulation symbol. The first interleaver can be referred to as a "bit level" interleaver, and the second interleaver can be referred to as a "symbol level" interleaver. One or more of the following rules can be applied. The operation of the first interleaver can be determined based on the retransmission number, and the operation of the second interleaver can be determined based on the HARQ retransmission number, where the retransmission number can be a repetition number for a single DL transmission.

[0108] In another solution, a bit reversal operation can be used for each retransmission, which can change the modulation symbol to which the bits are mapped via the constellation. For example, the bit sequence [1 1 1 1] can be transmitted in the first retransmission, and the bit sequence can be reversed to [0 0 0 0] in the second transmission. Additional bit reversal operations can be applied to subsequent retransmissions. For example, a bit reversal operation can be used when the modulation order is equal to or less than a threshold (e.g., QPSK), and vice versa.

[0109] In another solution, the scrambling sequence may be determined based on the HARQ retransmission number, where one or more scrambling sequences may be used. init ) can be based on the retransmission number. The scrambling sequence can be used for the coded bits before symbol mapping.

[0110] This document discloses an embodiment of incorporating the above multi-dimensional modulation schemes in a system for multiple TRP transmissions. In such an embodiment, each repetition of a downlink transmission may be transmitted by a separate TRP. Figure 3As shown and as previously described in the above paragraphs, each repetition 311, 312, 313 and 314 may be transmitted by a separate TRP within time slots 301, 302, 303 and 304. Alternatively, a limited number of TRPs may be used to transmit a series of repetitions. Each TRP may transmit multiple repetitions. For example, a TRP may transmit repetitions in an alternating manner, or one TRP may transmit consecutive repetitions before another TRP transmits one or more subsequent repetitions. In the solution, multi-dimensional modulation may be applied to multi-TRP transmissions, and the constellation mapping may vary according to each TRP. In the solution, the constellation of each repetition may be based on a rotated version of the constellation mapping used for the first TRP. Based on a previous configuration, or based on one or more other parameters (such as: the maximum number of TRPs, the time index, or the number of beams, etc.), the TRP may assume the applied rotation for each TRP. Each TRP constellation mapping definition can be implemented using orthogonal or non-orthogonal resources.

[0111] Fig. 9 An exemplary multi-TRP transmission scheme involving two TRPs and using multi-dimensional modulation is shown, where each TRP uses an orthogonal resource set. TRP 901 can be a primary TRP (P-TRP) and TRP 902 can be a secondary TRP (S-TRP). TRPs 901 and 902 can transmit separate repetitions of downlink transmissions to WTRU 903 using separate resource sets 911 and 912. The first resource set 911 and the second resource set 912 may be composed of the same number of REs; however, they may span different time intervals and / or frequencies. In the solution, the orthogonal resources may be mapped onto different bandwidth parts, and the bandwidth parts may each have different parameters. In the solution, the WTRU may explicitly or implicitly determine the constellation mapping used for each TRP transmission based on the DCI.

[0112] Additionally, based on the received semi-static configuration, the WTRU may assume a predefined constellation mapping for each TRP. The WTRU may independently receive and demodulate the transmitted payload mapped on each resource set. The WTRU may detect received symbols mapped on either of the resource sets, or use both resource sets 1 and 2 simultaneously to detect payloads transmitted via separate TRPs.

[0113] Fig.10 An exemplary multi-TRP transmission scheme involving two TRPs 1001 and 1002 and using multi-dimensional modulation is shown, where the TRPs use the same resource set 1010. In the solution, the WTRU may explicitly or implicitly determine the constellation mapping for each TRP transmission based on the DCI. Additionally, based on the received semi-static configuration, the WTRU may assume a predefined constellation mapping for each TRP.

[0114] The WTRU may use a two-step process to detect the transmitted payload. The WTRU may first use spatial demodulation (i.e., MIMO detection) to estimate the mapped symbols transmitted by each TRP. Second, relying on the demodulated symbols, the WTRU may detect the transmitted payload by processing the symbols simultaneously.

[0115] In an alternative solution, the WTRU may detect the transmitted payload using only a single-step process if the constellation mapping used by the TRP is such that for all or most of the bit groups mapped to the symbol, the combination of the received signal based on constellations C1 and C2 can be interpreted according to the new constellation E. In this case, the constellation E may provide a unique complex valued representation, e.g., for E=C1+C2, e j ∈E,e i ≠e j for i≠j.

[0116] Embodiments involving multi-TRP transmissions with constellation cycles are described herein. The TRP may be modulated and transmitted repetitions according to multiple different constellation mappings. In some cases, the number of different constellations used in all repetitions may be less than the number of repetitions transmitted.

[0117] In the solution, the TRP can use a constellation cycling pattern to send repetitions over a set of time transmission intervals (TTIs) with different constellations. The TRP can cycle through a series of constellations {C1, C2, …, C K}. In a multi-TRP scenario with N_TRP coordination points, the WTRU may receive N_TRP repetitions in one TTI.

[0118] Fig.11 An exemplary case of a multi-TRP transmission with four repetitions is shown, where only two constellation mappings (C1 and C2) are considered. Fig.11 As shown, during a first TTI 1111 (e.g., time slot), TRPs 1101 and 1102 may use C1 and C2, respectively, and in a second transmission event 1112, the constellations are swapped to C2 and C1. Transmissions from TRP 1101 and TRP 1102 may occur on orthogonal or non-orthogonal resource sets. In each transmission interval, packets for either transmission using either constellation pair may be self-decodable. Upon receiving the first packet pair, the WTRU may attempt to decode under the assumption that TRPs 1101 and 1102 used C1 and C2 to transmit the multi-dimensional retransmissions. If successfully decoded, the WTRU may send an ACK without waiting for a second reception.

[0119] The WTRU may determine the pattern of constellation mapping (e.g., "hopping pattern" or "constellation sequence") to be used by the S-TRP based on the pattern used for the P-TRP. The WTRU may determine the hopping pattern of the S-TRP based on the cyclic shift pattern of the P-TRP pattern. The cyclic shift index may be based on the TRP index, which may be dynamically indicated in the DCI or semi-statically preconfigured. For example, for 2*K repetitions, the P-TRP pattern may be in the sequence {C1, C2, ..., C K} uses K constellations over K TTIs, while the S-TRP mode can use the cyclic shift sequence {C K ,C1,C2,…,C K-1}, where the WTRU determines the shift equal to (TRP index - 1).

[0120] Alternatively, the WTRU may determine the constellation sequence of the S-TRP as an offset from the sequence used by the P-TRP. For example, the P-TRP may use {C1, C2, ..., C K}, however, S-TRP can use {C 1+i ,C 2+i ,…,C K+i The offset index i may be based on the TRP index, which is dynamically indicated in the DCI or semi-statically pre-configured.

[0121] Alternatively, the WTRU may determine the sequence to be used individually by each TRP. The sequences may be pre-configured as a pool of sequences, where each sequence may be uniquely identified by an index. The WTRU may determine the index based on the TRP index, which may be dynamically indicated in the DCI or semi-statically pre-configured.

[0122] The WTRU may attempt to decode after each TTI, and if the WTRU successfully decodes the transmission before all repetitions are received, the WTRU may be triggered to send an ACK. The ACK may indicate to one or more TRPs to stop transmission repetitions.

[0123] Alternatively, the constellations may remain fixed for one TRP while they cycle over several TTIs for another TRP. For example, starting from TTI [1…K], the P-TRP may use C1 while the S-TRP cycles through {C2,…,C K+1}. The WTRU may determine the cycle period of each TRP based on a pre-configuration or TRP index (eg, the constellation used by the P-TRP may always be fixed).

[0124] Various means for designing constellation mappings are provided herein. In a multi-transmission system, the constellation of each retransmission can be optimized to enhance the performance and reliability of the system. For a constellation design with size M, and assuming N dimensions (e.g., the number of TRPs or the number of iterations), many solutions can be found to support enhanced performance compared to simple time or space multiple transmissions that rely on accurate retransmissions of the payload. Examples of some metrics that can be used to determine and design enhanced constellations include Euclidean and product distances. The distance property of the constellation design can be combined with an appropriate bit mapping method such as Gray coding.

[0125] For example, considering that (l) ∈C N =[x 1m ,x 2m ,…,x Nm ] T ,m∈{1,2,…,M}, where X i =[x 1i ,x 2i ,…,x Ni ] T and X j =[x 1j ,x 2j ,…,x Nj ] T For two modulation points, the Euclidean distance can be measured as And the product distance can be expressed as

[0126] In 12A to Fig.12J In , potential constellation solutions for systems with dimension N=2 are listed. These solutions can benefit from the maximum minimum vector distance. In Figure 12, option 0 represents a reference two-dimensional system where both transmissions apply the same constellation mapping (NR, 16QAM).

[0127] In a solution for an N-dimensional multi-transmission system with N ≥ 2, the WTRU may assume the use of one or more of the constellation mapping options shown in Figure 12. In a solution, the WTRU may further assume any of the proposed options in Figure 12 for transmission repetitions, where further enhancements are based on phase rotation, beam / precoder cycling, dynamic resource allocation, etc.

[0128] Figures 13A to 13C Shown based on FIG. 12A to FIG. 12M The performance enhancements achieved by the presented multiple transport protocol options. As shown in the figure, FIG. 12A to FIG. 12M All presented options in may provide further enhancement compared to option 0, with option 6 providing the largest gain.

[0129] Although features and elements are described above in specific combinations, it will be understood by those of ordinary skill in the art 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 in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via a wired or wireless connection) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media (such as built-in hard disks and removable disks), magneto-optical media, and optical media (such as CD-ROM disks and digital versatile disks (DVDs)). A processor associated with software may be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A method performed by a wireless transmit / receive unit WTRU, the method comprising: receiving a physical downlink control channel, PDCCH, transmission from a first transmit / receive point, TRP; receiving, from the first TRP, a first repetition of a Physical Downlink Shared Channel (PDSCH) transmission based on the PDCCH transmission; and Based on the PDCCH transmission, a second repetition of the PDSCH transmission is received from a second TRP.

2. The method of claim 1, wherein the first TRP is a primary TRP.

3. The method of claim 1, wherein the second TRP is an auxiliary TRP. 4 . The method of claim 1 , wherein a first repetition of the PDSCH transmission and a second repetition of the PDSCH transmission are received in a same time interval.

5. The method according to claim 1, wherein: The first repetition of the PDSCH transmission and the second repetition of the PDSCH transmission are received using different component carriers.

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