WTRU and execution method thereof

Abstract

Disclosed are a WTRU and a method for performing the same. The WTRU may determine a downlink (DL) beam for synchronization. The WTRU may then determine correspondence information (BCI) for a transmit receive point (TRP) transmit (TX) / receive (RX) beam using the determined DL beam. Further, the WTRU may determine a number of WTRU TX beams based at least on the TRP TX / RX BCI. And, the WTRU may determine a set of WTRU TX beams based at least on the DL beams and the TRP TX / RX BCI, where determining the set includes determining one or more WTRUTX beam directions. In addition, the WTRU may transmit data using the determined set of WTRU TX beams. In an example, a TRP TX / RX BCI may be determined based on a received TRP TX / RX BCI.

Description

[0001] This application is a divisional application of the Chinese invention patent application with application date of September 28, 2017, application number 202110204184.3, and invention name “WTRU and its execution method”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Application No. 62 / 400,980 filed on September 28, 2016, U.S. Provisional Application No. 62 / 416,592 filed on November 2, 2016, U.S. Provisional Application No. 62 / 443,319 filed on January 6, 2017, and U.S. Provisional Application No. 62 / 454,470 filed on February 3, 2017, the contents of which are incorporated herein by reference. Background Art

[0004] Several organizations, including the International Telecommunication Union (ITU) Radiocommunication Sector (ITU-R), the Next Generation Mobile Networks (NGMN) Alliance, and the 3rd Generation Partnership Project (3GPP), have outlined general requirements for the emerging fifth generation (5G) systems, also referred to as New Radio (NR). Based on these general requirements, the use cases for the emerging 5G systems can be roughly categorized as follows: enhanced mobile broadband (eMBB), massive machine type communications (mMTC), and ultra-reliable low latency communications (URLLC).

[0005] Different use cases may focus on different requirements, such as higher data rates, higher spectral efficiency, low power and higher energy efficiency, lower latency and higher reliability. Various deployment scenarios are considering the use of a wide spectrum range from 700 megahertz (MHz) to 80 gigahertz (GHz).

[0006] As is well known, as carrier frequency increases, severe path loss may become a critical limiting factor in ensuring adequate coverage. Transmission in millimeter wave systems may also encounter non-line-of-sight losses such as diffraction loss, penetration loss, oxygen absorption loss, and blade loss. Summary of the invention

[0007] Disclosed is a method and system for determining beam reciprocity of beams of a wireless transmit / receive unit (WTRU). The WTRU may determine a downlink (DL) beam for synchronization. The WTRU may then determine transmit (TX) / receive (RX) beam correspondence information (BCI) of a transmission reception point (TRP) using the determined DL beam. Further, the WTRU may determine a number of WTRU TX beams based at least on the TRP TX / RX BCI. And, the WTRU may determine a WTRU TX beam set based at least on the DL beam and the TRP TX / RX BCI, wherein determining the set includes determining one or more WTRU TX beam directions. In addition, the WTRU may transmit data using the determined WTRU TX beam set.

[0008] In an example, the TRP TX / RX BCI may be determined based on a received TRP TX / RX BCI. In another example, the TRP TX / RX BCI may be determined based on at least one of: new radio (NR)-physical broadcast channel (PBCH) cyclic redundancy check (CRC) masking, demasking, one or more NR-PBCH resources, NR-PBCH payload, or system information block (SIB).

[0009] In another example, the determined DL beam may be used to receive the NR-PBCH from the TRP. In an additional example, the NR-PBCH may be the SS / PBCH. And, the SS / PBCH may include the SS block time index.

[0010] Additionally, the TX / RX BCI may include at least one of an indication of a correspondence type, a TX / RX beam width relationship, or a TX / RX beam direction relationship. Also, the WTRU TX beam set may be further determined based on the determined number of WTRU TX beams.

[0011] In an additional example, the WTRU may determine a preamble for a random access channel (RACH) procedure based on the resources used by the determined DL beam. The WTRU may then transmit the preamble. In an example, the preamble may be transmitted using a preamble time resource mapped to the gNB RX beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] A more detailed understanding may be obtained from the following description given by way of example in conjunction with the accompanying drawings, in which:

[0013] Figure 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented;

[0014] Figure 1B Yes, you can Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) for use within a communication system is shown;

[0015] Figure 1C It shows that it can be Figure 1A A system diagram of an example radio access network (RAN) and an example core network (CN) used within the communication system shown;

[0016] Figure 1D It shows that it can be Figure 1A A system diagram of another example RAN and another example CN used within the communication system shown;

[0017] Figure 2 is a flow chart illustrating an example of a beamforming random access method;

[0018] Figure 3 is a flow chart illustrating an example method and process for localized transmit (TX) beam / receive (RX) beam reciprocity;

[0019] Figure 4 is a flow chart illustrating an example use of reciprocity to determine a WTRU-TX beam set;

[0020] Figure 5 is a flow chart illustrating an example TX / RX beam reciprocity indication method;

[0021] Figure 6 is a flow chart illustrating an example method and process for determining TX / RX beam reciprocity;

[0022] Figure 7 is a flow chart showing another example TX / RX beam reciprocity indication method;

[0023] Figure 8 is a flow chart illustrating an example of a WTRU procedure for a beam operation mode;

[0024] Fig. 9 is a flow chart illustrating an example WTRU method and process for determining and reporting WTRU beam correspondence, beam reciprocity, or both;

[0025] Fig.10 is a flow chart illustrating an example physical random access channel (PRACH) procedure and preamble format selection based on beam deployment;

[0026] Fig.11 is a flow chart illustrating another example PRACH process and preamble format selection;

[0027] Fig.12 is a diagram of network operation showing a network operation mode with a power saving mode WTRU;

[0028] Fig.13 is a diagram of network operation showing a network operation mode having a low latency mode;

[0029] Fig.14 is a diagram of network operation showing network operation in a power saving mode and a low latency mode;

[0030] Fig.15 is a flow chart illustrating the effective operation of a transmission reception point (TRP) and the process of determining an operating mode; and

[0031] Fig.16 is a flow chart illustrating an example method and process for beam reciprocity based random access. DETAILED DESCRIPTION

[0032] Figure 1A 1 is a diagram showing an example communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content 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 DFT spread OFDM (ZT UW DTS-sOFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, and filter bank multi-carrier (FBMC), etc.

[0033] 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, although it should be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network components. Each WTRU 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, any of the WTRUs 102a, 102b, 102c, 102d may be referred to as a “station (STA)”, which may be configured to transmit and / or receive wireless signals, and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular 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 working in an industrial and / or automated process chain environment), consumer electronic devices, and devices working 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.

[0034] The communication system 100 may also include a base station 114a and / or a base station 114b. Each base station 114a and / or base station 114b may be any type of device configured to facilitate access to one or more communication networks (e.g., CN 106, Internet 110, and / or other networks 112) by wirelessly interfacing with at least one of the WTRUs 102a, 102b, 102c, 102d. For example, the base stations 114a, 114b may be base transceiver stations (BTS), Node Bs, eNode Bs, Home Node Bs, Home eNode Bs, Next Generation Node Bs (e.g., gNode Bs (gNBs)), New Radio (NR) Node Bs, site controllers, access points (APs), wireless routers, and the like. Although each base station 114a, 114b is depicted as a single component, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network components.

[0035] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network components (not shown), such as a base station controller (BSC), a radio network controller (RNC), a relay node, and the like. 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 cells (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage for a specific geographic area that is relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, a cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, that is, each transceiver corresponds to a sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, by using beamforming, signals may be transmitted and / or received in a desired spatial direction.

[0036] 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, millimeter wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0037] More specifically, as described above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA, among others. 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).

[0038] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0039] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using NR.

[0040] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may jointly implement LTE radio access and NR radio access (e.g., 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).

[0041] 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 (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), and GSM EDGE (GERAN), among others.

[0042] For example, Figure 1AThe base station 114b in the example may be a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any appropriate RAT to facilitate wireless connectivity in a local area, such as a business location, a residence, 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 establish a wireless local area network (WLAN) by implementing a radio technology such as IEEE 802.11. In an embodiment, the base station 114b and the WTRUs 102c, 102d may establish a wireless personal area network (WPAN) by implementing a radio technology such as IEEE 802.15. In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may establish a picocell or a femtocell by utilizing a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, and the like). Figure 1A As shown, the base station 114b may be directly connected to the Internet 110. Thus, the base station 114b may not need to access the Internet 110 via the CN 106.

[0043] 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 WTRUs 102a, 102b, 102c, 102d. The data may have different 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, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or may perform advanced security functions such as user authentication. Although in Figure 1A Although not shown, it will be appreciated that the RAN 104 and / or CN 106 may be in direct or indirect communication with other RANs that employ the same RAT or a different RAT as the RAN 104. 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, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0044] 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 network 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 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 use the same RAT or a different RAT as the RAN 104.

[0045] 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.

[0046] Figure 1B is a system diagram showing an example WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keyboard 126, a display / touchpad 128, non-removable memory 130, a removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It should be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0047] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal decoding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, however it should be appreciated that the processor 118 and the transceiver 120 may be integrated into an electronic package or chip.

[0048] The transmit / receive component 122 may be configured to transmit or receive signals to or from a base station (e.g., base station 114a) via an air interface 116. For example, in one embodiment, the transmit / receive component 122 may be an antenna configured to transmit and / or receive RF signals. As an example, in an embodiment, the transmit / receive component 122 may be a transmitter / detector configured to transmit and / or receive IR, UV, or visible light signals. In yet another embodiment, the transmit / receive component 122 may be configured to transmit and / or receive both RF and optical signals. It should be appreciated that the transmit / receive component 122 may be configured to transmit and / or receive any combination of wireless signals.

[0049] Although in Figure 1B 102 as a single component, but the WTRU 102 may include any number of transmit / receive components 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive components 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0050] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive component 122 and to demodulate signals received by the transmit / receive component 122. As described above, the WTRU 102 may have multi-mode capabilities. Thus, for example, the transceiver 120 may include multiple transceivers that allow the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0051] The processor 118 of the WTRU 102 may be coupled to the speaker / microphone 124, the keyboard 126, and / or the 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 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 and store information in any 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 memories that are not physically located in the WTRU 102, such as, for example, a server or a home computer (not shown).

[0052] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power for use by the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (Ni-Cd), nickel-zinc (Ni-Zn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0053] 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) related to 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 should be appreciated that the WTRU 102 may acquire location information via any suitable positioning method while remaining consistent with an embodiment.

[0054] The processor 118 may also be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, Modules, frequency modulation (FM) radio units, digital music players, media players, video game console modules, Internet browsers, virtual reality and / or augmented reality (VR / AR) devices, and activity trackers, etc. Peripheral device 138 may include one or more sensors, which may be one or more of the following: gyroscopes, accelerometers, Hall effect sensors, magnetometers, orientation sensors, proximity sensors, temperature sensors, time sensors, geolocation sensors, altimeters, light sensors, touch sensors, magnetometers, barometers, gesture sensors, biometric sensors, and humidity sensors, etc.

[0055] The WTRU 102 may include a full-duplex radio for which reception and transmission of some or all signals (e.g., associated with specific subframes for both UL (e.g., for transmission) and DL (e.g., for reception) may be concurrent and / or simultaneous. A full-duplex radio may include an interface management unit that reduces and / or substantially eliminates self-interference by means of signal processing in hardware (e.g., chokes) or via 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 that transmits or receives some or all signals (e.g., associated with specific subframes for both UL (e.g., for transmission) or DL ​​(e.g., for reception).

[0056] Figure 1C 1 is a system diagram showing a communication system 100 including the RAN 113 and the CN 115. As described above, the RAN 113 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the CN 115.

[0057] The RAN 113 may include eNode-Bs 160a, 160b, 160c, however it will be appreciated that the RAN 113 may include any number of eNode-Bs while remaining consistent with an embodiment. Each of the eNode-Bs 160a, 160b, 160c may include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, for example, the eNode-B 160a may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0058] Each eNodeB 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with each other via an X2 interface.

[0059] Figure 1C The illustrated CN 115 may include a mobility management gateway (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. Although each of the foregoing components is described as being part of the CN 115, it should be appreciated that any of these components may be owned and / or operated by an entity other than the CN operator.

[0060] The MME 162 may be connected to each of the eNode-Bs 160a, 160b, 160c in the RAN 113 via an S1 interface and may act as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, performing bearer activation / deactivation processing, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0061] The SGW 164 may be connected to each of the eNode-Bs 160a, 160b, 160c in the RAN 113 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 also perform other functions, such as anchoring the user plane during inter-eNB handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, and managing and storing the contexts of the WTRUs 102a, 102b, 102c, and the like.

[0062] 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.

[0063] The CN 115 may facilitate communications with other networks. For example, the CN 115 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 115 may include or may be in communication with an IP gateway, such as an IP Multimedia Subsystem (IMS) server, and the IP gateway may serve as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0064] Although in Figures 1A-1D Although the WTRU is described as a wireless terminal, it should be appreciated that in certain typical embodiments, such a terminal may use a (eg, temporary or permanent) wired communication interface with a communication network.

[0065] In a typical embodiment, the other network 112 may be a WLAN.

[0066] A WLAN in an infrastructure basic service set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may access or be connected to a distributed system (DS) or other types of wired / wireless networks that send traffic into and / or out of the BSS. Traffic originating from outside the BSS and destined for the STA may arrive through the AP and be delivered to the STA. Traffic originating from the STA and destined for a destination outside the BSS may be sent to the AP for delivery to the corresponding destination. Traffic between STAs within the BSS may be sent through the AP, for example, when 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. The point-to-point traffic may be sent between the source STA and the destination STA (e.g., directly therebetween) using a direct link establishment (DLS). In certain typical embodiments, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS)). For example, 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. Here, the IBSS communication mode may sometimes be referred to as an "ad hoc" communication mode.

[0067] When using the 802.11ac infrastructure mode of operation or a similar mode of operation, the AP may transmit a beacon on a fixed channel (e.g., a primary channel). The primary channel may have a fixed width (e.g., a bandwidth of 20 MHz) or a dynamically set width. The primary channel may be a working channel of the BSS and may be used by STAs to establish a connection with the AP. In certain typical embodiments, carrier sense multiple access (CSMA / CA) with collision avoidance (e.g., in an 802.11 system) may be implemented. For CSMA / CA, STAs (e.g., each STA) including the AP may sense the primary channel. If a particular STA senses / detects and / or determines that the primary channel is busy, the particular STA may back off. In a specified BSS, one STA (e.g., only one station) may transmit at any given time.

[0068] A high throughput (HT) STA may communicate using a 40 MHz wide channel (eg, by combining a 20 MHz wide primary channel with adjacent or non-adjacent 20 MHz wide channels to form a 40 MHz wide channel).

[0069] Very high throughput (VHT) STA can support channels with widths of 20MHz, 40MHz, 80MHz and / or 160MHz. 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 discontinuous 80MHz channels (this combination can be referred to as an 80+80 configuration). For the 80+80 configuration, after channel coding, the data can be transmitted and passed through a segment parser, which can divide the data into two streams. Inverse fast Fourier transform (IFFT) processing and time domain processing can be performed separately on each stream. The stream can be mapped on two 80MHz channels, and the data can be transmitted by the STA performing the transmission. At the receiver of the STA performing the reception, the above operations for the 80+80 configuration can be reversed, and the combined data can be sent to the medium access control (MAC).

[0070] 802.11af and 802.11ah support sub-1 GHz operating modes. The channel operating bandwidth and carriers used in 802.11af and 802.11ah are reduced compared to 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 typical embodiments, 802.11ah may support meter type control / machine type communication (e.g., MTC devices in macro coverage areas). MTC may have certain capabilities, such as limited capabilities including support for (e.g., only support for) certain and / or limited bandwidths. The MTC device may include a battery, and the battery life of the battery is above a threshold (e.g., for maintaining a very long battery life).

[0071] For WLAN systems that can support multiple channels and channel bandwidths (e.g., 802.11n, 802.11ac, 802.11af, and 802.11ah), these systems include channels that can be designated as primary channels. The bandwidth of the primary channel can be equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be set and / or limited by the STA, where the STA originates from all STAs operating in the BSS that supports the minimum bandwidth operation mode. In the example of 802.11ah, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operation modes, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the width of the primary channel can be 1MHz. Carrier sensing and / or network allocation vector (NAV) settings can depend on the status of the primary channel. If the primary channel is busy (e.g., because the STA (which only supports the 1MHz operation mode) transmits to the AP), then even if most of the frequency band remains idle and available for use, the entire available frequency band can be considered busy.

[0072] 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. Depending on the country code, the total bandwidth available for 802.11ah is 6MHz to 26MHz.

[0073] Figure 1D1 is a system diagram showing a communication system 100 including the RAN 117 and the CN 119. As described above, the RAN 117 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 117 may also be in communication with the CN 119.

[0074] The RAN 117 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 117 may include any number of gNBs while remaining consistent with an embodiment. Each of the gNBs 180a, 180b, 180c may 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, 180c may utilize beamforming to transmit and / or receive signals to and / or from the gNBs 180a, 180b, 180c. Thus, for example, the gNB 180a may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a. In an embodiment, gNBs 180a, 180b, 180c may implement carrier aggregation techniques. For example, gNB 180a may transmit multiple component carriers (not shown) to WTR 102a. A subset of these component carriers may be on an unlicensed spectrum, while the remaining component carriers may be on a licensed spectrum. In an embodiment, gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) techniques. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0075] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with the scalable parameter configurations. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may be different for different transmissions, different cells, and / or different portions of the radio transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of different or scalable lengths (e.g., containing different numbers of OFDM symbols and / or lasting different absolute time lengths).

[0076] 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 without accessing other RANs (e.g., the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may utilize one or more of the gNBs 180a, 180b, 180c as mobility anchors. 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 WTRU 102a, 102b, 102c may communicate / connect to the gNB 180a, 180b, 180c while communicating / connecting to another RAN (e.g., the eNode-B 160a, 160b, 160c). For example, the WTRU 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c in a substantially simultaneous manner. In a non-standalone configuration, the eNode-B 160a, 160b, 160c may act as a mobility anchor for the WTRU 102a, 102b, 102c, and the gNB 180a, 180b, 180c may provide additional coverage and / or throughput to serve the WTRU 102a, 102b, 102c.

[0077] Each gNB 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, support network slicing, implement DC, implement interworking between NR and E-UTRA, route user plane data to user plane functions (UPFs) 184a, 184b, and route control plane information to access and mobility management functions (AMFs) 182a, 182b, and the like. Figure 1D As shown, gNB180a, 180b, and 180c can communicate with each other through the Xn interface.

[0078] Figure 1DThe CN 119 shown in FIG. 1 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and may include a data network (DN) 185a, 185b. Although each of the aforementioned components is described as part of the CN 119, it should be understood that any of these components may be owned and / or operated by entities other than the CN operator.

[0079] The AMF 182a, 182b may be connected to one or more gNBs 180a, 180b, 180c in the RAN 117 via an N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, supporting network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selecting a specific SMF 183a, 183b, managing registration areas, terminating non-access stratum (NAS) signaling, and mobility management, etc. The AMF 182a, 1823b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c based on the type of service utilized by the WTRU 102a, 102b, 102c. As an example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for MTC access, etc. The AMF 182a, 182b may provide a control plane function for switching between the RAN 117 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.

[0080] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 119 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 119 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and may configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, and providing downlink data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0081] The UPF 184a, 184b can be connected to one or more gNBs 180a, 180b, 180c in the RAN 117 via the N3 interface, which can provide the WTRUs 102a, 102b, 102c with access to packet-switched networks (e.g., the Internet 110) to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b can perform other functions such as routing and forwarding packets, implementing user plane policies, supporting multi-host PDU sessions, processing user plane QoS, buffering DL packets, and providing mobility anchoring, etc.

[0082] The CN 119 may facilitate communications with other networks. For example, the CN 119 may include an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 119 and the CN 108, or may communicate therewith. In addition, the CN 119 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired 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 an N3 interface to the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b and through the UPFs 184a, 184b.

[0083] In view of Figures 1A-1D and about Figures 1A-1D In accordance with the corresponding description of the present invention, one or more or all of the functions described herein in comparison with one or more of the following may be performed by one or more simulation devices (not shown): WTRU 102a-d, base station 114a-b, eNodeB 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN 185 ab and / or any other device described herein. These simulation devices may be one or more devices configured to simulate one or more or all of the functions herein. For example, these simulation devices may be used to test other devices and / or simulate network and / or WTRU functions.

[0084] The simulation device can be designed to implement one or more tests about other devices in a laboratory environment and / or an operator network environment. For example, the one or more simulation devices can perform one or more or all functions while being implemented and / or deployed as part of a wired and / or wireless communication network in whole or in part to test other devices inside the communication network. The 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 other devices in order to perform the test, and / or can use over-the-air wireless communication to perform the test.

[0085] One or more simulation devices can perform one or more functions, 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 utilized in a test lab and / or a test scenario of a wired and / or wireless communication network that is not deployed (e.g., tested) to implement tests on one or more components. The one or more simulation devices can be test devices. The simulation device can transmit and / or receive data using direct RF coupling and / or wireless communication via RF circuits (e.g., which can include one or more antennas).

[0086] Based on the general requirements listed by the International Telecommunication Union (ITU) Radiocommunication Sector (ITU-R), the Next Generation Mobile Networks (NGMN) Alliance, and the Third Generation Partnership Project (3GPP), the use cases of the emerging fifth generation (5G) systems can be roughly categorized as follows: enhanced mobile broadband (eMBB), massive machine type communications (mMTC), and ultra-reliable low latency communications (URLLC). Different use cases may focus on different requirements, such as higher data rates, higher spectral efficiency, low power and higher energy efficiency, lower latency, and higher reliability. Various deployment scenarios are considering the use of a wide spectrum range ranging from 700 megahertz (MHz) to 80 gigahertz (GHz).

[0087] As we all know, as the carrier frequency increases, severe path loss may become a key limiting factor in ensuring adequate coverage area. Transmission in mmWave systems may also encounter non-line-of-sight losses such as diffraction loss, penetration loss, oxygen absorption loss, and blade loss. An effective way to compensate for severe path loss by providing significant beamforming gain is to use tens or even hundreds of antenna elements to generate beamforming signals. Beamforming techniques can include digital, analog, and hybrid beamforming.

[0088] The eNodeB (or eNB) and / or the WTRU may use a random access procedure for at least one of: WTRU initial access (e.g., accessing a cell or eNodeB); resetting UL timing (e.g., resetting or calibrating WTRU uplink (UL) timing relative to a cell); and timing reset during handover (e.g., resetting or calibrating WTRU timing relative to a handover target cell). The WTRU may transmit a specific physical random access channel (PRACH) preamble sequence at a power PPRACH that may be based on configured parameters and / or measurements, and the WTRU may use one or more time-frequency resources to transmit the preamble. The configured parameters may be provided or configured by the eNodeB, and may include one or more of the following: initial preamble power (e.g., preamblelnitialReceivedTargetPower); offset based on the preamble format (e.g., deltaPreamble); random access response (RAR) window (e.g., ra-ResponseWindowSize); power ramping factor (e.g., powerRampingStep); and maximum number of retransmissions (e.g., preambleTransMax). The PRACH resources may include a preamble or a set of preambles and / or time / frequency resources that may be available for preamble transmission, which may be provided or configured by the eNode B. The metric may include path loss. The WTRU may select one or more time-frequency resources from the permitted set, or the resources may be selected by the eNode B and signaled to the WTRU.

[0089] After the WTRU transmits the preamble, if the eNodeB detects the preamble, it may respond with a RAR message. If the WTRU fails or does not receive a RAR message for the transmitted preamble (which may correspond to a preamble index and / or time / frequency resource, for example) within a specified time (e.g., ra-ResponseWindowSize), the WTRU may send another preamble at a later time with a higher power (e.g., powerRampingStep higher than the previous preamble transmission), where the transmission power may be limited by a maximum power, such as the maximum power configured for the WTRU, which may be configured for the WTRU as a whole (e.g., PCMAX) or for a serving cell of the WTRU (e.g., PCMAX,c). The WTRU may again wait to receive a RAR message from the eNodeB. This sequence of transmitting and waiting may continue until the eNodeB responds with a RAR message or until a maximum number of random access preamble transmissions (e.g., preambleTransMax) is reached. The eNodeB may transmit and the WTRU may receive a RAR message in response to a single preamble transmission.

[0090] Specific instances of random access procedures may be contention-based or contention-free. A contention-free procedure may be initiated by a request (e.g., from an eNodeB), for example, via physical layer signaling, such as a physical downlink control channel (PDCCH) command, or by higher layer signaling, such as a radio resource control (RRC) reconfiguration message (e.g., an RRC connection reconfiguration message that may contain mobility control information and may indicate or correspond to a handover request). For a contention-free procedure that may be initiated by a PDCCH command in subframe n, the PRACH preamble may be transmitted in either the first subframe or the first subframe available for PRACH n+k2, where k2 may be greater than or equal to 6. When initiated by an RRC command, there may be other delays that may be specified, for example, there may be minimum and / or maximum required or allowed delays. The WTRU may autonomously initiate a contention-based procedure for a variety of reasons, for example, these reasons may include initial access, UL synchronization recovery, or recovery from a radio link failure. For certain events (eg, events other than recovery from a radio link failure), there may be no definition or regulation as to how long after such an event the WTRU may send a PRACH preamble.

[0091] For a contention-free random access (RA) procedure, a PRACH preamble signaled by the network may be used (e.g., used by the WTRU). For a contention-based random access procedure, the WTRU may autonomously select a preamble, where the preamble format and / or one or more time / frequency resources that may be used for preamble transmission may be based on an indication or index (e.g., prach-configIndex) that may be provided or signaled by the eNodeB.

[0092] The eNode B may detect one of the preambles transmitted at the gradually increasing transmit power. In response to the detected preamble, the eNode B may transmit a RAR message.

[0093] In the examples presented here, the PRACH preamble may be considered as a PRACH resource. For example, the PRACH resource may include a PRACH preamble, time and / or frequency resources.

[0094] In the examples provided herein, the terms preamble resources, RACH resources, and PRACH resources are used interchangeably. Furthermore, in the examples provided herein, the terms RA, RACH, and PRACH are used interchangeably. Furthermore, in the examples provided herein, beam reciprocity and beam correspondence are used interchangeably.

[0095] The various examples disclosed herein are proposed for physical random access in a beamforming system. The following problems are addressed herein. In 5G New Radio (NR), it is ideal to design a unified RACH for both single beam and multi-beam operations. And in NR, it is ideal to introduce transmit (TX) / receive (RX) reciprocity properties into the random access design. Further, in NR, it is ideal to have an efficient solution for configuring PRACH resources. In addition, a method is provided herein for receiving RAR messages from a single TRP and / or multiple TRPs or performing random access channel (RACH) reception in a scenario with multiple transmit receive points (TRPs). In addition, in NR, it is ideal to design a RACH that is more simplified than the conventional RACH used in LTE.

[0096] When there is full reciprocity, partial reciprocity, or no reciprocity for TX / RX beam reciprocity, it is necessary to have modified WTRU procedures for handling TX / RX beam reciprocity. When the TX / RX beams have reciprocity, association can be used to detect the reciprocity. The next generation Node B (gNB) or TRP may change the beam scanning order. In this case, association or contact may be overridden. The TRP may be used as a non-limiting example of a cell or node that may have a communication path for transmission (e.g., in the downlink) and / or reception (e.g., in the uplink) with the WTRU.

[0097] As used herein, the terms cell, eNodeB, gNB, TRP, node, and entity may be used interchangeably. Further, the terms indication, indicator, and information may be used interchangeably herein. In addition, the examples described herein for a TRP may be applied to a WTRU, and the examples described herein for a WTRU may be applied to a TRP, and still conform to the other examples described herein. The terms reciprocal direction and reciprocal direction may be used interchangeably and still conform to the examples provided herein. In the examples provided herein, the term reciprocal direction may be used to refer to a direction that is opposite (e.g., plus or minus 180 degrees) to another direction. For a WTRU, a beam direction may be derived from an angle of the WTRU. For a TRP, a beam direction may be derived from an angle of the TRP. As used in the examples provided herein, the terms beam reciprocity and beam correspondence may be used interchangeably. Further, in the examples provided herein, the terms beam reciprocity information and beam correspondence information (BCI) may be used interchangeably. Further, in the examples provided herein, the terms DL beam, gNB TX beam, and WTRU RX beam may be used interchangeably. Furthermore, in the examples provided herein, the terms UL beam, gNB RX beam, and WTRU TX beam are used interchangeably.

[0098] Furthermore, in the examples provided herein, the terms mode and state may be used interchangeably. In the examples provided herein, the other connection mode may be an RRC connection mode. Furthermore, in the examples provided herein, the terms RA resources and physical RA (PRA) resources may be used interchangeably. Further, in the examples provided herein, the terms synchronization signal (SS) block and SS / physical broadcast channel (PBCH) block may be used interchangeably. Furthermore, in the examples provided herein, the terms PBCH and NR-PBCH may be used interchangeably, and in the examples provided herein, the terms SS and NR-SS may be used interchangeably.

[0099] When the TX / RX beams have local reciprocity, local correlation or local association can be used to detect the local reciprocity. Some gNB TX beams may not be reciprocal with the gNB RX beams. For example, the TX beamwidth may not be equal to the RX beamwidth. This may be due to different transmit and receive antenna structures or different numbers of antennas. Therefore, for the WTRU process, there are two cases that may need to be considered. In one case, the gNB TX beamwidth may be larger than the gNB RX beamwidth. In another case, the gNB TX beamwidth may be smaller than the gNB RX beamwidth.

[0100] In another scenario, the gNB TX beam may not be fully aligned with the RX beam. For example, even with the same beamwidth, the TX and RX beams may partially overlap.

[0101] In the case of no reciprocity of TX / RX beams, dynamic association can be used. It is necessary to have a modified method for indicating the gNB TX beam from the gNB TX beam. Either dynamic indication or semi-static indication can be used.

[0102] An example method may include transmitting, by the gNB, an indication of gNB TX / RX reciprocity. The method may further include determining, by the gNB, a mapping of gNB TX beams to gNB RX beams. The gNB may determine one or more WTRU transmit beams and may transmit to the WTRU an indication of an optimal DL beam for RAR. The mapping of TX and RX beams may be further refined. If gNB TX / RX reciprocity exists, a full association may be established between the gNB and the WTRU.

[0103] Furthermore, the example method may include performing TX beam scanning and receiving information corresponding to a selected WTRU TX beam from a TRP, wherein the selected WTRU beam information is based on the determined WTRU TX beam. The WTRU may be further configured to perform RX beam scanning and determine one or more RX beams based on a measurement metric. The WTRU may derive one or more TX beams using the determined one or more RX beams, and the WTRU may determine beam reciprocity based on a set of rules.

[0104] An example system may include a receiver configured to receive a request from a TRP for a WTRU to determine beam correspondence or reciprocity information. Based on the received request, the circuitry may be configured to determine the beam correspondence or reciprocity. The system further includes a transmitter configured to transmit a WTRU capability indication to the TRP, the WTRU capability indication including WTRU capability information and information corresponding to the determined beam correspondence or reciprocity. In this way, a single message may be used for both the capability indication and the beam correspondence or reciprocity.

[0105] Figure 2 is a flow chart illustrating an example of a beamformed random access method. As shown in the flow chart 200, the following example process may be performed. The gNB may transmit and the WTRU may receive an indication of gNB TX beam / RX beam reciprocity 210. Further, the WTRU may map the gNB TX beam to the gNB RX beam 220. In addition, the WTRU may determine one or more WTRU transmit beams 230. And, the WTRU may transmit and the gNB may receive an indication of the best DL beam for RAR 240. The WTRU may then refine the mapping of the TX and RX beams 250.

[0106] An example method for handling gNB TX beam / RX beam reciprocity is described herein. If gNB TX / RX reciprocity exists, then a complete association between one or more TX beams of the gNB and one or more Rx beams and an association between the WTRU and the gNB may be established. A one-to-one mapping between SS / PBCH blocks including PBCH and PRACH time beam resources may be used. The detected SS / PBCH block may be indicated with one or more PRACH time resources. The association may indicate the best preamble RX beam or PBCH TX beam at the gNB resulting from the best detected SS / PBCH block. That is, the TX beam may be equal to the RX beam.

[0107] The PBCH may signal the TX / RX beam reciprocity mode to the WTRU. When the WTRU receives this message, the WTRU may need to perform a preamble transmission for a specific gNB RX beam or for each gNB RX beam in order to coordinate with the gNB RX beam scanning. The TX / RX beam reciprocity mode may be used. For example, TX / RX beam reciprocity mode = "1" may indicate that TX / RX beam reciprocity exists. In another example, TX / RX beam reciprocity mode = "0" may indicate that TX / RX beam reciprocity does not exist.

[0108] In the example TX / RX beam reciprocity mode (e.g., TX / RX beam reciprocity mode = "1"), the gNB may change the beam scanning order and override the beam order for beam scanning at any time due to flexible operation of the system and network. The gNB can override the association and TX / RX reciprocity. In this case, it is possible that the best preamble RX beam derived from the best detected SS / PBCH block including the PBCH TX beam may not be indicated. In the example, the RX beam timing and TX beam timing are synchronized, however, even if TX / RX beam reciprocity may exist, the beam order may not be synchronized. Therefore, whether TX / RX beam reciprocity exists or not, a full RX beam scan is required.

[0109] In another example, the gNB may send an indication to the WTRU that includes information about the association between the SS / PBCH block and one or more PRACH preamble sequences and / or one or more resources. As an example, the gNB may signal the WTRU to transmit the preamble in a specific time resource for the gNB RX beam. In this way, the WTRU may not need to perform preamble transmissions for all gNB RX beams during the gNB RX beam scanning period. A PBCH or broadcast signal / channel carrying the remaining minimum system information or other system information may be used to indicate such information about the best gNB RX beam to the WTRU. In another example TX / RX beam reciprocity mode (e.g., TX / RX beam reciprocity mode = "0" or a similar mode), the gNB may send such an indication. By using this mode, the WTRU can save power.

[0110] The example methods proposed here are coverage association and TX / RX beam reciprocity. In the example, one solution is to indicate the coverage mode. For example, the PBCH may signal the coverage mode to the WTRU. When the WTRU receives this message, the WTRU may need to perform a preamble transmission for each gNB RX beam or a subset of gNB RX beams in order to coordinate with the gNB RX beam scanning.

[0111] In an example, overlay mode = "0" may indicate that information about the gNB RX beam should not be assumed even if TX / RX beam reciprocity mode = "1". If TX / RX beam reciprocity mode = "1", then overlay mode = "1" may indicate that information about the gNB RX beam may be assumed. In another example, approach, association mode = "0" may indicate that there is no information about the gNB RX beam and an assumption should be made from the gNB TX beam. Further, association mode = "1" may indicate that information about the gNB RX beam may be assumed from the gNB TX beam.

[0112] The gNB has control over coverage and is aware of TX / RX beam reciprocity. Thus, the gNB can signal the association mode to the WTRU. In an example, if the association mode = "0", then even if the TX / RX beams are reciprocal, information about the gNB RX beam cannot be assumed. In another example, when the association mode = "1", information about the gNB RX beam can be assumed even if the TX / RX beams are not reciprocal.

[0113] Example methods for handling local gNB TX / RX beam reciprocity or no gNB TX / RX beam reciprocity are discussed here. If there is local TX / RX reciprocity, then local associations (e.g., one-to-many, many-to-one, many-to-many) can be used. As long as the associations are time-synchronized, the associations can still indicate the best preamble RX beam on the gNB that originated from the detected best PBCH TX beam. In this case, the gNB may need to arrange the RX beams to match the TX beams as much as possible.

[0114] The TX and RX beam widths may differ due to no gNB TX / RX beam reciprocity or local TX / RX beam reciprocity. If the RX beam is wide and fully covers the TX beam, then an RX beam of this width is sufficient to receive preamble transmissions. If the RX beam is narrow and only covers a portion of the TX beam, then an RX beam with better resolution may be required. In one example, more symbols may be required for gNB RX beam scanning. For example, if the RX beam is only half the beam width of the TX beam, then the gNB may need to double the beam scanning resolution of the gNB receiver. Thus, uneven beam scanning for preamble transmission and / or reception is proposed. The PBCH can use M beams to perform TX beam scanning, while preamble reception on the gNB can use L beams for beam scanning. When L > M, the RX beam width can be less than the TX beam width. When L < M, the RX beam width can be greater than the TX beam width.

[0115] In the examples described here, the TX beam and the RX beam can partially overlap. In an example, even if the TX beam width is the same as the RX beam width, however, if the TX beam and the RX beam are not fully calibrated with each other, then due to the beam overlap between the TX and TX beams, two or more RX beams will still be required to perform beam scanning in order to cover the best TX beam. As in the case where the TX beam width is different from the RX beam width, the TX and RX beam scans may require different numbers of beams. However, for a given WTRU, the gNB may need to monitor the left and right beams corresponding to the DL beam detected for it. In an example, beam reception diversity using signal combining can be used.

[0116] Correlation can be used to detect TX / RX reciprocity. When reciprocity does not exist, full correlation may become less important. In an example, partial correlation can be used. In other words, if the DL TX beam is wider, then one DL TX beam can be mapped to two or more UL RX beams. Alternatively, if the DL TX beam is narrower, then multiple DL TX beams can be mapped to one UL RX beam. There are situations where multiple DL TX beams can be mapped to multiple UL RX beams (for example, when the TX beam width is not an integer multiple of the RX beam width), and vice versa.

[0117] If TX / RX beam reciprocity does not exist, then dynamic signaling or semi-static signaling may be used. In an example, a temporal ordering of the beams may exist, but at least one of the following may also be true: the TX beam resolution may be different from the RX beam resolution, the TX beam and RX beams may not be calibrated, or the TX beam and RX beams may not be synchronized. In another example, beam ordering may not exist and the TX beam width may not be equal to the RX beam width. RX beam scanning may be required. However, it may be necessary to indicate the desired RX beam solution to the WTRU through the use of PBCH. In Figure 3 An example solution is shown in .

[0118] Figure 3 300 is a flowchart illustrating an example method and process for localized TX beam / RX beam reciprocity. In the example shown in flowchart 300, a resolution for TX beam width and a resolution for RX beam width may be determined 310. Also, a TX beam and RX beam overlap ratio may be determined 320. Further, a corresponding signaling mechanism for indicating the beam width resolution and the beam overlap ratio may be selected 330. For example, the gNB may signal to the WTRU information regarding the association between one or more SS / PBCH blocks and one or more PRACH preamble sequences and / or one or more time / frequency resources. As an example, the gNB may signal the beam correspondence information to the WTRU. In addition, the gNB may determine and select an RX beam scanning strategy for the gNB receiver 340. In addition, the gNB may determine and select a TX beam scanning strategy for the WTRU transmitter 350. In an example, the gNB may select that the WTRU should use preamble transmission as the beam scanning strategy.

[0119] The WTRU may receive synchronization (SYNC) signals, reference signals, and / or other signals from the TRP (e.g., to synchronize with the TRP in time and / or frequency). The WTRU may receive one or more signals or information from the TRP in a direction (e.g., determined by the WTRU to be an acceptable direction or an optimal direction). An acceptable direction may be a direction that enables the WTRU to receive and / or decode one or more signals from the TRP (e.g., a broadcast signal (e.g., PBCH) that may include a broadcast channel (BCH)). The optimal direction may be a direction determined by the WTRU, for example, from a set of acceptable directions, to provide the highest signal strength (or other best measurement or metric).

[0120] The determined direction may correspond to a TRP transmit (TRP-TX) beam. Furthermore, the determined direction may correspond to a WTRU receive (WTRU-RX) beam. Information about the TRP-TX beam may be provided either explicitly (e.g., via the PBCH or system information that may be broadcast) or implicitly (e.g., by using different synchronization signals or reference signals for different beams, or by using different masks or cover codes on the synchronization signals or reference signals to distinguish different beams).

[0121] The WTRU may determine the receive direction based on its WTRU-TX beam direction granularity that matches or does not match the TRP-TX beam granularity. In an example, the receive direction may be an angle of arrival.

[0122] The WTRU may select or determine a set of transmit beams (WTRU-TX beams) or transmit directions for transmissions (e.g., initial transmissions) to the TRP based on the determined acceptable beams or directions or the determined best beams or directions. In the embodiments and examples described herein, directions and beams are interchangeable.

[0123] In an example, reciprocity information may be provided, for example, by a TRP and / or for use, for example, by a WTRU. The WTRU may determine a set of beams or directions for transmission to a TRP based at least on the reciprocity of the TRP transmit and receive beams, directions, and / or communication paths (e.g., information about the reciprocity).

[0124] The WTRU may receive and / or use configuration or information related to reciprocity that may be used or assumed for a cell, eNodeB, gNB, TRP, node (e.g., network node), or other entity. In an example, the other entity may be a network entity with which the WTRU may communicate.

[0125] Reciprocity information (e.g., regarding TRP) can be used to indicate a relationship between a transmit communication path (e.g., of TRP) and a receive communication path. As an example, the reciprocity information can include an indication of a relationship between a TRP-TX beam characteristic and a TRP-RX beam characteristic.

[0126] The beam characteristics may be beam width, beam direction, and / or number of beams. For example, the reciprocity information of the TRP may indicate at least one of the following. The reciprocity information may indicate whether the TRP-RX beam width is wider or narrower than the transmit beam width. Furthermore, the reciprocity information may indicate whether the number of TRP-TX beams is the same as the number of TRP-RX beams.

[0127] Further, the reciprocity information may indicate whether the TRP-RX beam direction is the same as the TRP-TX beam direction. In an additional example, the reciprocity information may indicate whether each TRP-RX beam direction is the same as the corresponding TRP-TX beam direction. In an example, the reciprocity information may indicate whether the beam directions are the same, regardless of whether the number of beams is the same and / or whether the beam widths are the same.

[0128] And, the reciprocity information may indicate whether the TRP has a TRP-RX beam in the same direction as the transmit beam. In addition, in the example, the reciprocity information may indicate whether each TRP-RX beam of the TRP has the same direction as the corresponding transmit beam.

[0129] For example, a transmit beam to which reciprocity information may be indicated may be a beam that may provide at least one of the following: a synchronization signal, a reference signal, a broadcast channel or signal (e.g., PBCH), and / or system information (e.g., system information block (SIB)). Further, for example, a transmit beam to which reciprocity information may be indicated may refer to a beam that provides at least one of the following: a synchronization signal, a reference signal, a broadcast channel or signal (e.g., PBCH), and / or system information (e.g., SIB).

[0130] The reciprocity indication may provide a value, ratio, and / or index to a table of values ​​that may convey relevant information. One or more reciprocity indications may be provided via broadcast or system information. The PBCH may provide one or more reciprocity indications. The WTRU may receive and / or determine reciprocity information and may use the information (e.g., at least one reciprocity indicator) to determine at least one beam characteristic regarding a transmission to a TRP.

[0131] The transmission may be a transmission of a signal, such as a reference signal or a channel. The transmission may be a transmission of a preamble, data or a data channel, control information or a control channel. The transmission may be for initial access, wherein the initial access may be a random access, an unlicensed access or a licensed access. In an example, the random access may include a preamble that may be randomly selected for transmission. In another example, the licensed access may include a scheduled access.

[0132] The WTRU may determine whether a beam is an acceptable beam or an optimal beam according to the examples described herein. In an example, an acceptable beam may include an acceptable direction of the beam, and an optimal beam may include an optimal direction of the beam. In the examples described herein, the term determined DL beam is used as a non-limiting example of a determined optimal beam or an acceptable beam.

[0133] The WTRU may determine a set of M transmit beams (WTRU-TX beams) or transmit directions for transmission (e.g., initial transmission) to the TRP based at least on reciprocity information or a reciprocity indication that it may receive or determine for the TRP. The WTRU may perform transmissions to the TRP on the M transmit beams. Transmissions on multiple beams may be in series or in parallel (e.g., based on the capabilities of the WTRU and / or the TRP).

[0134] For example, the WTRU may determine the number of beams M in the WTRU-TX beam set based at least on reciprocity information or a reciprocity indication that may be determined or received by the WTRU. The WTRU may determine which WTRU-TX beams to include in the set (e.g., which beams or directions to perform transmissions on) based at least on reciprocity information or a reciprocity indication that may be determined or received by the WTRU.

[0135] The WTRU may determine (e.g., based on reciprocity information) that at least one of the following is included in the WTRU-TX beam set: a first WTRU-TX beam (e.g., one or only one WTRU-TX beam that may be in the same direction or the direction closest to the determined DL beam); one or more (e.g., N) beams that may be adjacent to the first WTRU-TX beam (e.g., located on its left and / or right side).

[0136] In an example, N may be 0. The values ​​of M and / or N may depend on whether the TRP-TX beam and the TRP-RX beam may have the same direction (e.g., whether the TRP-RX beam may be centered on the TRP-TX beam).

[0137] For example, if the TRP-RX beam can be centered on the TRP-TX beam, then N can be a first number (e.g., 0 or a very small number), and / or M can be a first number (e.g., 1 or a very small number). If the TRP-RX beam is not centered on the TRP-TX beam, then M and / or N can be a second number that can be greater than the first corresponding number.

[0138] The value of M and / or N may depend on the beamwidth of at least one of the following: a WTRU-TX beam, a WTRU-RX beam, a TRP-TX beam, and / or a TRP-RX beam. N may be an even number. N may be evenly split to the left and right of the first beam.

[0139] It is possible that the WTRU-TX beam direction does not exactly match the WTRU-RX beam direction or the TRP-TX beam. The WTRU-TX beam with the closest direction to the determined DL beam may be used as the UL beam.

[0140] The beam type may be at least one of a TRP-TX beam, a TRP-RX beam, a WTRU-TX beam, and / or a WTRU-RX beam. The WTRU may determine at least one of M, N, and / or a WTRU-TX beam set based on at least one of: the number of beams and / or beamwidth of at least one beam type; or a relationship of the number of beams and / or beamwidth between at least two beam types.

[0141] For example, when the beam widths of the TRP-TX beam and the TRP-RX beam are the same, M may be determined to be a first number. When the beam widths of the TRP-TX beam and the TRP-RX beam are different, M may be determined to be a second number. The second number may be smaller than the first number, for example, when the TRP-RX beam is wider than the TRP-TX beam.

[0142] The WTRU may determine the beamwidth of the WTRU-TX beam based at least on reciprocity information that may be received by the WTRU.

[0143] For example, the WTRU may provide beam characteristic information (e.g., regarding WTRU-TX and WTRU-RX beams) and / or reciprocity information to a TRP (e.g., with which it may communicate). Figure 4 An example is shown in .

[0144] Figure 4is a flow chart illustrating an example usage of reciprocity to determine a WTRU-TX beam set. In the example shown in flow chart 400, the WTRU may determine the DL beam to be used 410. For example, the WTRU may determine to use the best DL beam. In another example, the WTRU may determine to use an acceptable DL beam. The WTRU determination may be based on beam strength. In another example, the DL beam may be used for synchronization between the WTRU and the TRP. In another example, the WTRU may use the DL beam to receive the PBCH. In addition, the WTRU may also determine TRP beam reciprocity information. For example, the WTRU may determine the TRP beam reciprocity information based on the determined DL beam. In the example, the WTRU may receive TRP beam reciprocity information 420. Thus, the WTRU may determine the TRP beam reciprocity information based on the received TRP beam reciprocity information. In another example, the WTRU may be pre-configured with TRP beam reciprocity information. In another example, the WTRU may determine the TRP beam reciprocity information based on a PBCH cyclic redundancy check (CRC) mask, one or more PBCH resources, a PBCH payload, or a SIB, and the like. In addition, the WTRU may determine the TRP TX / RX BCI. For example, the WTRU may determine the TRP BCI based on the determined DL beam. In an example, the WTRU may receive the TRP TX / RX BCI. Thus, the WTRU may determine the TRP TX / RX BCI based on the received TRP TX / RXBCI. In another example, the WTRU may be pre-configured with the TRP TX / RX BCI. In another example, the WTRU may determine the TRP TX / RX BCI based on a PBCH cyclic redundancy check (CRC) mask, one or more PBCH resources, a PBCH payload, or a SIB, and the like.

[0145] And, the WTRU may determine a number of WTRU-TX beams that may be represented by M based on the beam reciprocity information 430. In another example, the WTRU may determine the number of WTRU-TX beams based on the TRP TX / RX BCI. In addition, the WTRU may determine a WTRU-TX beam set 440 based on the beam reciprocity information. In a further example, the WTRU may determine the WTRU-TX beam set based on the TRP TX / RX BCI. In another example, the WTRU may further determine the WTRU-TX beam set based on the determined number of WTRU-TX beams. In an example, determining the WTRU-TX beam set includes determining one or more WTRU-TX beam directions.

[0146] In addition, the WTRU may perform a transmission to the TRP using the determined WTRU-TX beam set 450. In an example, the WTRU may perform a transmission to the TRP using a random access procedure. In another example, the WTRU may transmit data using the determined WTRU TX beam set.

[0147] In another example, the WTRU may determine the timing of transmissions using the WTRU TX beam set based at least on the TRP TX / RX BCI. In another example, the TRP TX / RX BCI may include at least one of an indication of a correspondence type, an indication of a TX / RX beam width relationship, or an indication of a TX / RX beam direction relationship. In another example, the WTRU may determine and transmit the WTRU TX / RX BCI.

[0148] The PBCH may indicate TX / RX reciprocity to optimize preamble reception. This indication may be in several ways. For example, a CRC mask may be used or employed in such methods. Another example method may use orthogonal cover codes. Another example method may use PBCH to detect location (e.g., time or frequency). Additional example methods may explicitly employ 1 or 2 bits in the PBCH payload.

[0149] Figure 5 500 is a flow chart illustrating an example TX / RX beam reciprocity indication method. As shown in the example in flow chart 500, TX / RX beam reciprocity can be indicated via PBCH and using a CRC mask. According to the number of TX / RX beam reciprocity patterns, a corresponding number of masks can be used. For example, a PBCH payload can first be generated 510. And a CRC can also be generated 530. The generated CRC can be masked 550 with a sequence that depends on the TX / RX reciprocity. Then, the PBCH payload can be concatenated 570 with the masked CRC.

[0150] To indicate the three types of TX / RX beam reciprocity, three configurations may be defined. For example, configuration 1 may indicate full TX / RX beam reciprocity, configuration 2 may indicate partial TX / RX beam reciprocity, and configuration 3 may indicate no TX / RX beam reciprocity. The numbering of these configurations may be reordered and still conform to the examples provided herein. In addition, a different number of configurations may also be used and still conform to the examples provided herein.

[0151] In the example, three sequences are available for Figure 5 The CRC mask of the depicted method uses. In other examples, the CRC mask may use a different number of sequences and still conform to the examples provided herein.

[0152] In an example, local TX / RX reciprocity may be due to interference and may occur in a dynamic manner. Therefore, using a semi-static signaling method may not be the best process for providing TX / RX beam reciprocity indication. Instead, a combination of semi-static and dynamic signaling methods may be optimal. For example, to indicate two types of TX / RX beam reciprocity, two configuration types may be defined. In an example, configuration 1 may indicate full TX / RX reciprocity and configuration 2 may indicate no TX / RX reciprocity. Thus, two sequences may be used for Figure 5 Depicts the method used by the CRC mask.

[0153] Figure 6 is a flow chart illustrating an example method and process for determining TX / RX beam reciprocity. It is possible that a TRP or gNB may still need to use dynamic signaling (e.g., Layer 1 (L1) / Layer 2 (L2) signaling) to indicate local TX / RX reciprocity. By executing the example process shown in flow chart 600, local TX / RX reciprocity may be dynamically signaled. For example, a WTRU may receive a PBCH 610 indicating TX / RX beam reciprocity. The WTRU may determine whether the PBCH indicates full TX / RX beam reciprocity or no TX / RX beam reciprocity 620. If the PBCH indicates no TX / RX beam reciprocity, then the WTRU may assume no gNB TX / RX beam reciprocity 630. If the PBCH indicates TX / RX beam reciprocity, then the WTRU may assume full gNB TX / RX beam reciprocity 640. When the WTRU receives a PBCH indicating full reciprocity, the WTRU may temporarily assume full gNB TX / RX beam reciprocity 640 until the WTRU receives a second level indication 650 indicating whether the gNB TX / RX beam reciprocity is really full gNB TX / RX beam reciprocity or partial gNB TX / RX beam reciprocity. In an example, such a second level indication may be transmitted using L1 / L2 signaling or RRC signaling. The WTRU may determine whether the second level indication is for full reciprocity or partial reciprocity 660. For example, if the second level indication is for partial reciprocity, then the WTRU may assume partial reciprocity 670. Further, if the second level indication is for full reciprocity, then the WTRU may assume full reciprocity 680.

[0154] To indicate the three types of association patterns, three patterns can be defined. For example, pattern 1 can indicate a complete association, pattern 2 can indicate a partial association, and pattern 3 can indicate no association. The numbering of the patterns can be reordered and still conform to the examples provided here. Further, different numbers of patterns can be used and still conform to the examples provided here.

[0155] In the following example method, the CRC mask for the association mode may use three sequences. In an example, the association mode may also be indicated by a CRC mask.

[0156] Figure 7 700 . In the example shown in flowchart 700 , the gNB may generate a PBCH payload 710 . Further, the gNB may generate a CRC 730 . The generated CRC may be masked with a sequence that depends on the association mode. According to the number of association modes, a corresponding number of one or more masks may be used. The generated CRC may be masked by the gNB with a sequence that depends on the association mode 750 . The gNB may then concatenate the PBCH payload and the masked CRC 770 .

[0157] In another example, the PBCH CRC may be scrambled or XORed with an N-bit mask that may jointly indicate the number of antennas or antenna ports, antenna configuration, antenna and / or TX / RX beam reciprocity. In an example, N may be 16. In other examples, N may be 8, 24, or 32. If the TRP or gNB has TX / RX reciprocity with M transmit antennas, then the PBCH CRC may be scrambled with a mask corresponding to the TX / RX reciprocity for the M antennas, and so on. The PBCH may also be used to indicate one or more gNB RX beams to the WTRU.

[0158] The following example method uses PBCH to indicate the preamble RX beam. In the example where only one RX beam is indicated, the implicit indication may use PBCH masking, SS block time index, PBCH demodulation reference signal (DMRS) sequence index, etc. Further, each mask, SS block time index, or PBCH DMRS sequence index, etc. may correspond to the best gNB RX beam. The best gNB RX beam may be mapped to the preamble index, and the mask, SS block time index, and / or PBCH DMRS sequence index may be associated with the preamble index. The preamble index may include one or more of a sequence index, a time index, a frequency index, or a resource index, etc. In another example, if only one RX beam is indicated, the explicit indication may use payload bits, and a small number of bits may be used to indicate the best gNB RX beam. For example, the bits for the explicit indication may be carried in RACH message 2 or a RAR message.

[0159] In an example of multiple RX beam indication, the implicit indication may be a PBCH mask, an SS block time index, or a PBCH DMRS sequence index, etc., wherein each mask, SS block time index, or PBCH DMRS sequence index, etc. may correspond to a subset of beams, such as the best K gNB RX beams. The best K gNB RX beams may be mapped to a set of one or more preamble indexes, and one or more masks, SS block time indexes, or PBCH DMRS sequence indexes may be associated with the set of preamble indexes. The preamble index may include one or more of a sequence index, a time index, a frequency index, or a resource index, etc. In an example, the best K gNB RX beams may be mapped to a set of K preamble indexes and K masks. In another example of multiple RX beam indication, the explicit indication may use payload bits, and a small number of bits may be used to indicate a subset of beams, such as the best K gNB RX beams.

[0160] In the examples provided herein, a gNB TX beam may be mapped to a gNB RX beam. In an example, the gNB TX beam may be used to transmit an SS block, wherein the SS block may include a time index, which may be an SS block time index. Further, the gNB TX beam ID may be an SS block time index. And, the gNB RX beam may be used to receive a preamble, which may use one or more preamble sequences and / or one or more preamble resources. In addition, the preamble resources may be allocated according to a preamble resource index, which may include a time resource index and / or a frequency resource index. And, the preamble sequence may be determined based on the preamble sequence index. In an example, the gNB TX beam may be mapped to a time index x (e.g., an SS block time index x), and the gNB RX beam may be mapped to a time index y (e.g., a PRACH resource time index y). In an example, y may be equal to x plus c, and c may be a time offset, a frequency offset, another type of offset, etc. In other examples, c may be equal to 0, and the time index may be used or not used. This means that the gNB TX beam is associated with the gNB RX beam, or the DL SS block time index can be associated with the UL preamble time resource index. When the WTRU detects the best gNB TX beam at time x, it can automatically know the best gNB RX beam at time y, and vice versa.

[0161] When the gNB detects the preamble transmitted by the WTRU at time resource index y, it may implicitly know the best SS / PBCH block time index x detected by the WTRU. When the WTRU determines to report the time index (e.g., SS / PBCH block time index x) to the gNB, the WTRU may transmit the preamble at time resource index y, where time indexes x and y are associated with each other. In the example, each gNB TX beam may be mapped to an SS block, and each gNB RX beam may be mapped to a preamble time resource. To ensure that the preamble can be received by the best RX beam of the gNB, the WTRU should send the preamble at time resource y. In the absence of gNB TX / RX reciprocity, the PRACH resources may be defined by a time-frequency index, and the SS block may be associated with one or more UL preamble time / frequency resources and / or sequences. For example, an SS block time index may be associated with one or more UL preamble time / frequency resources and / or sequence indices. This is because the WTRU may select a preamble and may transmit the selected preamble on the PRACH time-frequency resource to identify the SS block and feedback the SS block time index. As an example, the WTRU may select a preamble (e.g., preamble index n) and may transmit the selected preamble on the PRACH frequency resource to identify the nth SS block and feedback the SS block time index. In another example, the WTRU may select a preamble and may transmit the selected preamble on the PRACH frequency resource (e.g., resource index n) to identify the nth SS block and feedback the SS block time index. In another example, the WTRU may select a preamble (e.g., preamble index n) and may transmit the selected preamble on the PRACH frequency resource (e.g., frequency resource index m) to identify the nth SS block and feedback the SS block time index. In this case, the nth SS block may be associated with the preamble index n and the frequency resource index m.

[0162] In an example, the WTRU may select a preamble (e.g., preamble index n) and may transmit the selected preamble on a PRACH frequency resource (e.g., frequency resource index m) at time resource index j to identify the nth SS block and feedback the SS block time index. In this case, the nth SS block may be associated with the preamble index n, the frequency resource index m, and the time resource index j.

[0163] In another example, an SS block may be associated with multiple preambles, frequencies, and / or time indexes. In this case, the WTRU may select a preamble from a preamble set (e.g., preamble set index n) and may transmit the selected preamble on a PRACH frequency resource in a frequency set (e.g., frequency resource set index m) at a time resource set j to identify the nth SS block and feedback the SS block time index. In this case, the nth SS block may be associated with a preamble set index n, a frequency resource set index m, and / or a time resource set index j.

[0164] Multiple SS blocks may also be associated with a preamble, a frequency, and / or a time index. The WTRU may select a preamble (e.g., preamble index n) and may transmit the selected preamble on a PRACH frequency resource (e.g., frequency resource index m) at time resource index j to identify the nth SS block set and feedback the SS block time index or SS block set time index. In this case, the nth SS block set may be associated with a preamble index n, a frequency resource index m, and / or a time resource index j.

[0165] One or more DL TX beams and one or more UL RX beams may be associated. The association between one or more DL TX beams and one or more UL RX beams may be signaled via system information, minimum system information, remaining minimum system information, or other system information. Each of one or more SS blocks, one or more PRACH resources, preamble time resources, preamble frequency resources, and / or one or more preamble sequences may be associated with one or more of each other. The association between SS blocks, PRACH resources, and / or preamble sequences may be signaled via system information, minimum system information, remaining minimum system information, or other system information.

[0166] However, in the presence of gNB TX / RX reciprocity, the PRACH resource may be defined only by the frequency index. This is because the WTRU may select a preamble and transmit the selected preamble on the PRACH frequency resource at time y in order to identify the SS block and feedback the SS block time index if the PBCH is received at time x. For example, the WTRU may select a preamble (e.g., preamble index n) and may transmit the selected preamble on the PRACH frequency resource (e.g., frequency resource index m) at time y in order to identify the nth SS block and feedback the SS block time index. In this case, the nth SS block may be associated with the preamble index n and the frequency resource index m. In the example, the WTRU does not transmit the selected preamble at an undetermined time. The WTRU may transmit the selected preamble only when the gNB makes the best RX beam present. The advantage in this example is that the gNB can receive the preamble with the best RX beam.

[0167] In an example, the WTRU may report the detected SS / PBCH blocks using only the preamble (e.g., preamble resource or sequence, etc.). The preamble may convey or contain SS / PBCH block information, where different preambles (e.g., sequences and / or resources) may indicate different SS / PBCH blocks. The preamble number x may be used to indicate or report the SS / PBCH block number x. In the examples herein, the preamble may be a preamble sequence, a preamble resource, or a combination thereof. The preamble resource may be a preamble time resource, a frequency resource, a preamble space resource, or a combination thereof.

[0168] Different SS / PBCH blocks may be indicated or reported using one or more preambles (e.g., one or more preamble sequences and / or resources). For example, a preamble sequence number x may correspond to a SS / PBCH block number x. The WTRU may use the preamble sequence number x to indicate or report the SS / PBCH block number x. When the WTRU determines to indicate or report the SS / PBCH block number x, the WTRU may select the preamble sequence number x and may transmit the selected preamble sequence number x.

[0169] In another example, the preamble time resource number x may correspond to the SS / PBCH block number x. The WTRU may use the preamble time resource number x to request the SS / PBCH block number x. When the WTRU determines to indicate or report the SS / PBCH block number x, the WTRU may select the preamble time resource number x and may transmit the preamble sequence in the preamble time resource number x.

[0170] In another example, the preamble frequency resource number x may correspond to the SS / PBCH block number x. The WTRU may use the preamble frequency resource number x to indicate or report the SS / PBCH block number x. When the WTRU determines to indicate or report the SS / PBCH block number x, the WTRU may select the preamble frequency resource number x and may transmit the preamble sequence in the preamble frequency resource number x.

[0171] The association between the SS / PBCH block and the preamble may be used. The association between the SS / PBCH block and the preamble time resource, frequency resource, preamble sequence or any combination thereof may be used.

[0172] An association between a preamble sequence and an SS / PBCH block may be used. As an example association, one preamble may be associated with one SS / PBCH block. Preamble sequence number x may be associated with SS / PBCH block number x. When the WTRU determines to indicate or report SS / PBCH block number x, the WTRU may select preamble sequence number x and transmit it. As another example association, one preamble may be associated with multiple SIBs. Preamble sequence number x may be associated with SS / PBCH block number x and SS / PBCH block number y. When the WTRU wants to request SS / PBCH block number x or SS / PBCH block number y, the WTRU may select preamble sequence number x and transmit it. As another example association, multiple preamble sequences may be associated with one SS / PBCH block. Preamble sequence number x and preamble sequence number y may be associated with SS / PBCH block number x. When the WTRU wants to request SS / PBCH block number x, the WTRU may select and transmit preamble sequence number x or preamble sequence number y. When multiple preamble sequence transmissions are used or enabled, the WTRU may transmit preamble sequence number x and preamble sequence number y simultaneously.

[0173] An association between one or more preamble time resources and one or more SS / PBCH blocks may be used. As an example association, one preamble time resource may be associated with one SS / PBCH block. Preamble time resource number x may be associated with SS / PBCH block number x. When the WTRU wants to indicate or report SS / PBCH block number x, the WTRU may select preamble time resource number x and transmit a preamble sequence. As another example association, one preamble time resource may be associated with multiple SIBs. Preamble time resource number x may be associated with SS / PBCH block number x and SS / PBCH block number y. When the WTRU wants to indicate or report SS / PBCH block number x or SS / PBCH block number y, the WTRU may select preamble time resource number x and transmit a preamble. As another example association, multiple preamble time resources may be associated with one SS / PBCH block. Preamble time resource number x and preamble time resource number y may be associated with SS / PBCH block number x. When the WTRU wants to indicate or report SS / PBCH block number x, the WTRU may select preamble time resource number x or preamble time resource number y and transmit the preamble. When multiple preamble time resource transmissions are used or enabled, the WTRU may transmit the preamble in both preamble time resources numbered x and y.

[0174] Likewise, an association between one or more preamble frequency resources and one or more SS / PBCH blocks may be used. Likewise, an association between one or more preamble time / frequency resources, one or more sequences and any one of one or more SS / PBCH blocks may be used.

[0175] If the WTRU receives an indication with an association between the preamble and the SS / PBCH block, then the WTRU may use the preamble to indicate or report the SS / PBCH block. In an example, the preamble may be a preamble sequence and a preamble resource, etc. If the WTRU does not receive an indication with an association between the preamble and the SS / PBCH block, then the WTRU may use a control field in the payload (e.g., RACH message 3) to indicate or report the SS / PBCH block.

[0176] A single association or mapping may be used. A 1-bit association indication may be used. The WTRU may be indicated to have or not have an association, for example, "1" may indicate "has an association" and "0" may indicate "does not have an association".

[0177] In another example, more than one association or mapping may be used. An N-bit association indication may be used. Two examples may be used. In one example, there are two indicators used, and the first indicator may indicate that there is an association or there is no association. In the example, the first indicator may be one bit. If the WTRU receives a first indicator indicating that there is an association, then a second indicator (N bits) may be used to indicate which association should be used. In the example, the second indicator may be N bits. In another example, a single indicator is jointly encoded with "having" and "not having" associations and multiple associations. In the example, the single indicator may be N bits. In the example of 3 associations, a single indicator of two bits may be used. Accordingly, bit 00 may indicate that there is no association. Further, bits 01, 10, and 11 may indicate a first association, a second association, and a third association, respectively. The first association, the second association, and the third association may be labeled "association 1", "association 2", and "association 3", respectively.

[0178] The association indication may be part of the RACH configuration and may be carried or included in a broadcast signal or channel, such as a Remaining Minimum System Information (RMSI) signal. The association indication may also be carried in the SS, New Radio PBCH (NR-PBCH), or other system information (OSI).

[0179] The association between the SS / PBCH block and the PRACH preamble (sequence, resource, index thereof) may be based on the actually transmitted SS / PBCH block which may be indicated in the RMSI. In another example, the association between the SS block and the PRACH preamble (sequence, resource, index thereof) may be based on the maximum SS / PBCH block, wherein the maximum SS / PBCH block may be predetermined according to the frequency band.

[0180] The number of available NT-RACH preambles in a cell can be determined by the following formula:

[0181] M=L′·K Equation (1)

[0182] Where L' may be the number of actually transmitted SS blocks within the SS block set, and K may be the number of preambles associated with each SS block. In an example, K may be 1 for a one-to-one association of preambles and SS blocks.

[0183] This association can be accomplished by mapping M consecutive preambles in a cell to L' SS blocks or SS / PBCH blocks. Also, K consecutive preambles can be mapped to each SS block.

[0184] The preamble in a cell may be associated or mapped to an SS / PBCH block based on at least one of: a cyclic shift of a root Zadoff-Chu sequence, a root index of a Zadoff-Chu sequence, a NR-RACH preamble time instance within a slot, a slot index, and a frequency index (which may include, for example, a subcarrier index and a PRB index, etc.), etc.

[0185] In an example association, the set of NR-RACH preamble sequences in a cell may be determined in the order of: available cyclic shifts of a root Zadoff-Chu sequence, increasing NR-RACH preamble time instances within a slot, increasing root indexes, increasing frequency indexes, and increasing slot indexes. In another example, the set of NR-RACH preamble sequences in a cell may be determined in the order of: cyclic shifts of a root Zadoff-Chu sequence, increasing root indexes of Zadoff-Chu sequences, increasing NR-RACH preamble time instances within a slot, increasing slot indexes, and increasing frequency indexes.

[0186] The gNB may configure the WTRU to report additional SS / PBCH block indices (e.g., the strongest SS / PBCH block index) via a contention-based random access message. In an example, the message may be contention-based random access message 3.

[0187] The gNB may configure the WTRU to report multiple SS / PBCH block indices via a PRACH preamble during a contention-free random access procedure (e.g., in handover). The gNB may be configured to report multiple SS / PBCH block indices via one or more PRACH preambles during a contention-based random access procedure.

[0188] In another example, the best gNB RX beam may be identified without performing RX beam scanning or training at the gNB RX site. This may reduce beam scanning or training overhead and latency. The disadvantage is that the PRACH resources available for a given WTRU may be reduced because now the WTRU is not free to use the resources selected by the WTRU in the time domain. The WTRU may only have degrees of freedom in the frequency domain. This may increase the probability of transmission collisions. However, since the WTRU is forced to transmit the preamble at different time instances, this preamble transmission also reduces the collision probability of the preamble transmission. If the WTRUs are covered by the same beam, the WTRU collision probability may increase because each WTRU has to send the preamble in the same beam and the same time instance without spatial separation.

[0189] For WTRUs in different beams, transmission conflicts can be reduced because the WTRUs are separated in time. This solution may be referred to as autonomous beam scheduling. That is, the time index for the detected best gNB TX beam may automatically determine the PRACH resources for the WTRU in the time domain but not the frequency domain, and the best gNB RX beam may be automatically scheduled. This solution may be considered as autonomous TDMA for RACH.

[0190] In an example, the best gNB TX beam may indicate the best gNB RX beam set (e.g., beam set Q). The WTRU may need to send preambles one at a time. For example, the WTRU may need to send preambles at time x+nc, time x+nc+1, time x+nc-1, and so on, where n is a positive integer if the beam set is a positive or negative index of the best gNB TX beam. The set may be referred to as a local beam set. The local beam set may be considered local relative to the index of the best SS / PBCH block or gNB TX beam.

[0191] In another example, the beam set may also be non-local. The WTRU may randomly send a preamble on one or more PRACH time resources (e.g., time x+nc, time x+nc+1, time x+nc-1, etc.). In the example, X may be the index of the best SS / PBCH block or gNB TX beam, n may be an integer, and c may be a constant for different designs. Thus, the PRACH resources may be defined by a time index (which may be a local time index) and a frequency index (which may be a global frequency index). The local time index is local with respect to the index of the best SS / PBCH block or gNB TX beam. And, the global frequency index is global with respect to the index of the best SS / PBCH block or gNB TX beam.

[0192] Figure 8 800 is a flow chart illustrating an example of a WTRU process for beam operation mode. As shown in the flow chart 800, the WTRU may receive a PBCH at time index x 810. The WTRU may apply a time offset to transmit a preamble 830. The WTRU may also receive a gNB TX / RX reciprocity indicator. The WTRU may determine whether the gNB TX / RX reciprocity indicator is true or false 850. In the example, if the gNB TX / RX reciprocity indicator is equal to true (TRUE), then the WTRU may transmit a preamble 860 at time index y, where y = offset + x. Otherwise, the WTRU may transmit a preamble 870 at time index y, where y = offset + x0.

[0193] In an example, TX / RX beam reciprocity determination, TX / RX beam refinement, or both may be performed. For example, the gNB may have knowledge or information about the TX / RX beam reciprocity. The gNB may also determine or refine the TX / RX beam reciprocity through a training method. Such example solutions may be used for, but are not limited to, the following example configurations.

[0194] In an example, the best SS / PBCH block may be SS / PBCH block index x, and the best PRACH preamble and / or resource may be PRACH preamble sequence / resource index y. In another example, the best TX beam may be beam x, and the best RX beam may be beam y. In a further example configuration, y=x, and this case may be referred to as full beam reciprocity. In another example configuration, y=x+Δ, where Δ=±1, 0, ±2 or Δ=±1, ±2, etc. This case may be referred to as partial beam reciprocity. In an additional example configuration, y≠x and y=x+Δ is not invalid. This case may be referred to as non-beam reciprocity.

[0195] The TX / RX beam reciprocity may be determined or refined using beam scanning or training. In an example, a multi-stage solution may be used. For example, in an example stage, a full beam scan may be performed. In a further example stage, the TX / RX beam reciprocity may be determined or refined. In another example stage, energy-saving beam scanning or training may be performed to update the beam reciprocity.

[0196] In an example, a WTRU TX beam may be mapped to a WTRU RX beam. If the WTRU receives the PBCH on the best WTRU RX beam z, then the WTRU may send the preamble using WTRU TX beam z, provided there is WTRU TX / RX beam reciprocity. Otherwise, at time x+nc, the WTRU may need to send the preamble by scanning all WTRU TX beams one at a time, where n is a positive integer.

[0197] In another example, the best WTRU RX beam may indicate the best WTRU TX beam set. In an example, the best WTRU TX beam set may be beam set Q. At time x+nc, the WTRU may need to send a preamble by scanning the WTRU TX beams of beam set Q one at a time, where n is a positive integer. Such a beam set may be pre-defined via a master information block (MIB) / SIB or via configuration.

[0198] Example methods and processes for determining beam reciprocity, beam correspondence, or both are disclosed herein. Beam reciprocity / correspondence for one or more WTRU TX / RX beams may be determined via the following example steps. It will be appreciated by those skilled in the art that certain steps may be performed out of order or not at all. Other steps may also be performed between the steps provided herein. In step 1, the WTRU may perform a TX beam scan. In step 2, the TRP may determine one or more WTRU TX beams based on measurements performed on the TRP. In step 3, the TRP may indicate or transmit information related to the determined WTRU TX beam information based on the one or more WTRU TX beams determined in step 2. One or more beam indexes of the determined one or more beams may be signaled to the WTRU via, but not limited to, RAR, NR-PRACH message 4, NR-PDCCH, NR enhanced PDCCH (ePDCCH), medium access control element (MAC CE), or RRC signaling, etc.

[0199] In step 4, the WTRU may perform RX beam scanning. In step 5, the WTRU may determine one or more RX beams based on one or more metrics. In step 6, the WTRU may derive one or more TX beams using the one or more RX beams determined in step 5, thereby assuming beam reciprocity / correspondence at the WTRU. In step 7, the one or more beams indicated in step 3 and the one or more beams derived in step 6 may be compared at the WTRU, and the WTRU may determine a final beam reciprocity / correspondence at the WTRU based on a rule or set of rules. For example, if the indicated and derived beams in steps 3 and 6 are the same, then it may be declared and determined that there is full beam reciprocity / correspondence at the WTRU. If the indicated and derived beams in steps 3 and 6 are partially the same, then it may be declared and determined that there is partial beam reciprocity / correspondence at the WTRU. If the indicated and derived beams in steps 3 and 6 are completely different, then it may be declared and determined that there is no beam reciprocity / correspondence at the WTRU.

[0200] To determine beam reciprocity / correspondence with respect to one or more TRP TX / RX beams, the following steps may be performed. It will be appreciated by those skilled in the art that certain steps may be performed out of order or not performed at all. Other steps may also be performed between steps.

[0201] In step 1, the TRP may perform TX beam scanning. In step 2, the WTRU may determine one or more TRP TX beams based on one or more measurements. In step 3, the WTRU may notify, indicate, or transmit information related to the determined TRP TX beam information based on the one or more beams determined in step 2. The determined one or more beam indices may be signaled to the TRP via, but not limited to, WTRU feedback, CSI feedback, NR-PRACH message 1, one or more preambles, NR-PUCCH, NR-PUSCH, or a scheduling request (SR), etc.

[0202] In step 4, the TRP may perform RX beam scanning. In step 5, the TRP may determine one or more RX beams based on one or more measurements. In step 6, the TRP may derive one or more TX beams using the one or more RX beams determined in step 5, thereby assuming beam reciprocity / correspondence on the TRP. In step 7, the one or more beams indicated in step 3 and the one or more beams derived in step 6 may be compared on the TRP, and the TRP may determine the final beam reciprocity / correspondence on the TRP based on a rule or set of rules. For example, if the beams indicated and derived in steps 3 and 6 are the same, then it may be declared and determined that there is complete beam reciprocity / correspondence on the TRP. If the beams indicated and derived in steps 3 and 6 are partially the same, then it may be declared and determined that there is local beam reciprocity / correspondence on the TRP. If the beams indicated and derived in steps 3 and 6 are completely different, then it may be declared and determined that there is no beam reciprocity / correspondence on the TRP.

[0203] The metric or measure used to determine beams or beam reciprocity / correspondence may be based on, but not limited to, signal-to-noise ratio (SNR), signal-to-interference-and-noise ratio (SINR), signal strength, power, beam quality, or CSI, among others.

[0204] By using one or more of the methods and processes described herein, WTRU beam correspondence or reciprocity may be determined. Once the WTRU beam correspondence or reciprocity is determined, the result of the determined beam correspondence or reciprocity may be signaled or indicated to the other side of the wireless connection. For example, if the WTRU determines the beam correspondence or reciprocity, the WTRU may provide feedback to the gNB, TRP, or other WTRU including the result of the determined beam correspondence or reciprocity. Such feedback may be semi-static or dynamic. For example, the result of the determined beam correspondence or reciprocity may be fed back via, but not limited to, initial uplink transmission, WTRU feedback, CSI, NR-PRACH message 1, one or more preambles, NR-PRACH message 3, NR-PUCCH, NR-PUSCH, SR, MAC, MAC CE, RRC signaling, or sidelink transmission, etc. Such feedback may be periodic, aperiodic, on-request, or on-demand. Such feedback on the results of WTRU beam correspondence or reciprocity may be initiated by the WTRU, the TRP, or both. Such feedback on the results of WTRU beam correspondence or reciprocity may be triggered by an event.

[0205] In another example, the WTRU may provide feedback including the results of the determined beam correspondence or reciprocity to the gNB, TRP, or other WTRU as part of the WTRU capability indication. For example, one or more results regarding the determined beam correspondence or reciprocity may be signaled or indicated to the gNB, TRP, or other WTRU, alone or together with the WTRU capabilities, from the designated WTRU via: initial uplink transmission, NR-PRACH message 1, one or more preambles, RRC connection establishment request, NR-PRACH message 3, RRC signaling, or sidelink transmission, etc.

[0206] Fig. 9 900 is a flow chart illustrating example WTRU methods and procedures for determining and reporting WTRU beam correspondence, beam reciprocity, or both. In the example shown in flow chart 900, a gNB or TRP may request information regarding WTRU beam correspondence, beam reciprocity, or both 910. The WTRU may perform methods and procedures regarding beam correspondence / reciprocity 920. In an example, the WTRU may perform methods and procedures for beam correspondence / reciprocity based on a request received from a gNB or TRP. In another example, the WTRU may perform methods and procedures for beam correspondence / reciprocity without receiving a request from a gNB or TRP.

[0207] Further, the WTRU may send an indication of the beam correspondence / reciprocity determination to the gNB or TRP in a predetermined procedure. Such a procedure may be via an initial access procedure, a random access procedure, or an RRC procedure during the RRC connection phase. The WTRU may determine the beam correspondence / reciprocity based on one or more results of the beam correspondence / reciprocity determination method and procedure 930. In an example, the WTRU may determine the beam correspondence / reciprocity by complying with the beam correspondence / reciprocity determination method and procedure provided elsewhere herein. In an example, the WTRU may indicate the beam correspondence / reciprocity information to the gNB or TRP as part of the WTRU capability indication 940. The WTRU may also indicate the beam correspondence / reciprocity to other WTRUs 950. In an example, the WTRU may also indicate the beam correspondence / reciprocity to other WTRUs if necessary.

[0208] The WTRU may indicate beam correspondence or reciprocity information to the gNB or TRP as part of the WTRU capability transmission. The capability transmission may include full or no beam correspondence or reciprocity, or full, partial or no beam correspondence or reciprocity. Additionally, additional categories of beam correspondence or reciprocity may be reported.

[0209] In an example, a preamble may be used to indicate the best DL beam for the RAR. If such DL beam does not change, then the best DL PBCH beam may be used for the RAR DL beam. Such association may be done in a time (or frequency) synchronized manner at the beam level. However, such association should be within a coherence time. There are several reasons why the DL beams used for SYNC, PBCH, and RAR may change, including: if the channel changes rapidly; if the changes occur due to WTRU rotation or obstruction; or if the network decides to use a different DL beam, beam width, or beam order, etc.

[0210] Therefore, in some cases, when the gNB changes the beam scanning order of RAR (which is different from the beam scanning order of PBCH), it is necessary to have a method for indicating the best DL beam with respect to RAR. When such association does not exist or is not used, an alternative solution can be used. For example, the preamble can be used for such indication.

[0211] In an example, a preamble may be used to indicate one of M DL beams. Different preamble groups may be designed. In this case, the preamble may be designed to have M groups, each of which may indicate one of the M DL beams. When the WTRU performs random access, the WTRU may select a preamble from the corresponding preamble group associated with the detected DL beam. When the gNB detects the preamble, it may know which preamble group the detected preamble belongs to, and thereby know which DL beam may be used for subsequent DL transmissions (e.g., for RAR transmissions). In the spatial domain, the DL beams are typically separated in different beam directions, so there is no mutual interference and no collision when the WTRU selects a preamble. Both preambles are received and the same random access (RA)-radio network temporary identifier (RNTI) may be sent.

[0212] Furthermore, due to the spatial separation, RAR messages will not collide. When two or more WTRUs detect the same DL beam and select the same preamble group, there is a greater likelihood that two WTRUs will select the same preamble, since there are fewer preambles in a smaller group, and thus a collision may occur in the RAR. However, since the beams are narrow, fewer WTRUs will reside in the same narrow beam and this reduces the chance that multiple WTRUs may initiate a random access procedure. The collision may be proportional to the number of WTRUs and inversely proportional to the number of preambles.

[0213] In an example, the number of WTRUs and the number of preambles may cancel each other out in terms of collision probability. In such an example, the collision probability may remain the same in other respects. Other methods of using different cyclic shifts of the same root sequence, different root sequences, or a combination of both may also be used.

[0214] In a further example, the indication of WTRU TX / RX beam reciprocity may depend on a preamble format, such as long / short format, preamble sequence length, preamble group, preamble sequence, root index, cyclic shift, one or more frequency / time / space resources, etc. or a combination thereof.

[0215] In addition, the indication of the desired one or more TRP TX beam indices may depend on the preamble format, such as long / short format, preamble sequence length, preamble group, preamble sequence, root index, cyclic shift, one or more frequency / time / space resources, etc. or a combination thereof.

[0216] Synchronous design can be very simple and generate less overhead, but it provides less flexibility because fixed associations are required and resources are determined by association. Thus, fixed associations and resources determined by association reduce flexibility. However, synchronous design can reduce overhead because additional signaling is used for TX / RX beam reciprocity indication.

[0217] The preamble can be used to indicate different service types. In addition to the DL beam for RAR, the preamble can also indicate eMBB, URLLC, and mMTC by selecting the preamble from one of the M preamble groups. The preamble can also indicate different combinations of low latency and payload size.

[0218] The indication about the service type may depend on the preamble format, such as long / short format, preamble sequence length, preamble group, preamble sequence, root index, cyclic shift, one or more frequency / time / space resources, etc. or a combination thereof.

[0219] In an example, in addition to the slot index and frequency index at which the preamble is transmitted in time and frequency, the RA-RNTI may also be calculated based on the SS / PBCH block index associated with the RACH preamble.

[0220] In another example, the RA-RNTI may also be calculated based on a time index and a frequency index. The time index may be a unique value within the RACH resource group. The time index may depend on a time slot index and a starting symbol index within the time slot.

[0221] In another example, the time index in the RA-RNTI may be based on one of: a subframe number, a symbol number, a slot number, and a RACH opportunity index within a radio frame.

[0222] A RACH resource group may be a set of RACH resources that share the same RA-RNTI. A downlink control information (DCI) message that schedules one or more RAR messages on a PRACH preamble on each RACH resource within a RACH resource group in the PDCCH may be masked with the same RA-RNTI. The gNB or the network may indicate the number of RACH resources per RACH resource group. The gNB or the network may indicate the number of random access preamble IDs (RAPIDs). The WTRU may calculate the number of preambles per RACH resource within a RACH resource group.

[0223] One or more PRACH resources can be obtained from the PBCH and / or other sources, with or without association. For example, the PBCH can be used to configure beam resources and PRACH resources, such as time, frequency, and code, etc. The beam resources can also be part of the PRACH resources. Additionally, for example, the PBCH can be used to jointly configure PRACH resources, such as time, frequency, and code, etc. In the case of having synchronous resource allocation for the PRACH, the PBCH can be associated with the PRACH. By detecting the PBCH DL beam, the WTRU can also obtain the time and beam resources for preamble transmission. When the preamble group is also associated with the beam, by detecting the PBCH DL beam, the WTRU can also obtain the code resources. In the example, the WTRU obtaining the code resources can include the WTRU obtaining the preamble group. The PBCH DL beam can also be associated with the frequency resources through modulo operation.

[0224] The synchronous PBCH / PRACH can be designed in two phases. One example phase can include determining the resources for time, beam, and code. Another example phase can include determining the frequency resources. If the frequency resource index is represented by f id then the frequency resources can be determined by Equation 2:

[0225] f id = beam index mod N F Equation (2)

[0226] where N F is the maximum range of f id . For example, if 0 ≤ f id < L, then N F = L.

[0227] In the example, the asynchronous design can use dynamic or semi-static signaling or a combination of both. In another example, the asynchronous design can use a predefined mapping. For example, the angle of departure (AoD), the angle of arrival (AoA), or one or more overlapping beams can all be used as resources. The AoA or AoD can be estimated during initial synchronization or PBCH transmission.

[0228] The beam scanning method for the next phase can be indicated by the preamble. The beam scanning method can depend on time, frequency, code, the number of scans, the number of symbols for successive scans, and periodicity, etc.

[0229] PBCH transmissions in the DL may be associated with PRACH transmissions in the UL. A PBCH to PRACH association may be established whereby, when the WTRU detects the best PBCH TX beam, it may automatically gain knowledge of the best preamble gNB RX beam if there is gNB TX / RX beam reciprocity. If the PBCH transmissions are not associated with the PRACH transmissions, then, when the WTRU detects the best PBCH TX beam, it may not have knowledge of the best preamble gNB RX beam even if there is gNB TX / RX beam reciprocity. Thus, the WTRU requires the PBCH to indicate the best preamble gNB RX beam. In another example, a SIB (e.g., SIB1) may be used to configure the preamble and RACH resources.

[0230] Fig.10 1000 is a flow chart illustrating an example PRACH process and preamble format selection based on a beam deployment. In the example shown in flowchart 1000, the beam deployment may be an indicated beam deployment. As shown in flowchart 1000, a WTRU may be equipped and / or configured with multiple RACH preamble formats 1010. In an example, the RACH preamble formats may include long and short preamble formats. The WTRU may detect a SYNC signal and may receive an indication of single beam or multi-beam operation 1020. Further, the WTRU may determine the preamble format according to the beam deployment or beam operation mode 1030. Further, the WTRU may determine whether a single beam deployment or a multi-beam deployment is indicated 1040.

[0231] If a single beam deployment or single beam operation mode is indicated, the WTRU may determine a preamble format 1050. Further, the WTRU may transmit a preamble with the determined preamble length 1055. The WTRU may then perform a RACH procedure based on the determined preamble format 1060. For example, the WTRU may determine a first preamble format. In an example, the first preamble format may be preamble format A. In another example, the WTRU may determine a long preamble format to be preamble format A. Further, the WTRU may transmit a preamble with a long preamble length. The WTRU may perform a RACH procedure based on the determined long preamble format.

[0232] If a multi-beam deployment or a multi-beam operation mode is indicated, the WTRU may determine a preamble format 1070. Further, the WTRU may transmit a preamble with the determined preamble length 1075. The WTRU may then perform a RACH procedure 1080 based on the determined preamble format. For example, the WTRU may determine a second preamble format. In an example, the second preamble format may be preamble format B. In another example, the WTRU may determine a short preamble format to be preamble format B. Further, the WTRU may transmit a preamble with a short preamble length. The WTRU may perform a RACH procedure based on the determined short preamble format.

[0233] Fig.11 11 is a flow chart illustrating another example PRACH process and preamble format selection. As shown in flowchart 1100, the WTRU may be equipped and / or configured with multiple RACH preamble formats (e.g., long and short preamble formats) 1110. The WTRU may detect a SYNC signal and may receive an indication of multi-beam operation 1120. Further, the WTRU may measure a DL signal (e.g., a SYNC, PBCH, or a broadcast reference signal (BRS) signal) 1130. And, the WTRU may select a preamble format based on a preamble format selection criterion 1140. As an example, the preamble format selection criterion may include a reference signal received power (RSRP), a reference signal received quality (RSRQ), a cell center indication, or a cell edge indication. If the RSRP is below a predetermined threshold or indicates a cell edge, the WTRU may determine a long preamble format and may transmit a preamble with a long preamble length. Otherwise, the WTRU may determine a short preamble format and may transmit a preamble with a short preamble length.

[0234] As an example, if a cell edge is indicated, the WTRU may determine a long preamble format 1150. Furthermore, the WTRU may then transmit a preamble 1160 with a long preamble length.

[0235] In another example, if the cell center is indicated, the WTRU may determine the short preamble format 1170. Furthermore, the WTRU may then transmit a preamble 1180 with a short preamble length.

[0236] Fig.12 12 is a network operation diagram illustrating a network operation mode of a WTRU with an energy saving mode. As shown in the example of network operation diagram 1200, when operating in a regular mode 1210, the WTRU may perform a full beam scan. In the example, the regular mode 1210 may be a first mode. Further, the first mode may be referred to as mode 1. Fig.12As can be seen in the figure, the gNB may use beam 1220 to perform transmission and reception, and the WTRU may use beam 1230 to perform transmission and reception. When operating in energy efficiency mode 1250, the WTRU may perform short beam scanning or no beam scanning. In this mode, the gNB may use beam 1260 to perform transmission and reception, and the WTRU may use beam 1270 to perform transmission and reception. In one example, the energy efficiency or low latency mode 1250 may be referred to as the second mode. In another example, the second mode may be referred to as mode 2.

[0237] Thus, two modes of operation may be required to achieve energy efficiency. When TX / RX beam reciprocity does not exist on the WTRU, the gNB and the WTRU may operate in Mode 1. When TX / RX reciprocity exists on the WTRU, the gNB and the WTRU may operate in Mode 2. The WTRU may report its TX / RX reciprocity to the gNB so that the gNB can decide in which mode it may operate. Each WTRU may report its own TX / RX reciprocity to the gNB (e.g., as part of the WTRU capabilities or as part of CSI feedback). When all WTRUs in a TRP or cell have TX / RX reciprocity, the TRP or gNB may configure Mode 2 for the TRP or cell and operate in Mode 2. Additionally, when all WTRUs in a beam have TX / RX beam reciprocity, the gNB may configure Mode 2 for the beam and operate in Mode 2. Thus, a beam, TRP, or cell may operate in Mode 1 or Mode 2. In an example, the gNB may switch to Mode 2 when the conditions are met in order to achieve energy efficiency. When the conditions are not met, the gNB can switch back to Mode 1 to perform normal operations.

[0238] Fig.13 13 is a network operation diagram showing a network operation mode with a low latency mode. As shown in the example of network operation diagram 1300, low latency mode 1310 may be used. In one example, low latency mode 1310 may be a third mode. Further, the third mode may be referred to as mode 3. Fig.13 As shown, the gNB may use beam 1320 to perform transmission and reception, and the WTRU may use beam 1330 to perform transmission and reception.

[0239] In an example, Mode 3 may be used when there is gNB TX / RX reciprocity. In Mode 3, the gNB may operate an RX cycle where each gNB RX beam allows all WTRU TX preamble beams to perform training with a full scan. Since the gNB has TX / RX reciprocity, each WTRU knows when to send its preamble. As a result, each WTRU can complete the preamble transmission of all WTRU TX beams in a short period of time. Some WTRUs will complete the preamble in a shorter time and some will complete in a longer time, depending on the gNB RX beam of the WTRU. However, Mode 3 provides relatively low latency operation compared to the normal case where all WTRUs complete the preamble training at the same but longer time.

[0240] In summary, Mode 1 may be operated when TX / RX beam reciprocity does not exist on both the gNB and the WTRU. Mode 2 may be operated when TX / RX beam reciprocity exists on the WTRU. Mode 2 may achieve better energy savings. Mode 3 may be operated when gNB TX / RX beam reciprocity exists. Mode 3 may achieve low latency operation. An energy efficient and low latency mode may be used when both the gNB and the WTRU have TX / RX beam reciprocity. This energy efficient and low latency mode may be a fourth mode. The fourth mode may be referred to as Mode 4.

[0241] Fig.14 1400 , the energy saving mode and the low latency mode 1410 may be used. In the example, the energy saving mode and the low latency mode 1410 may be referred to as Mode 4. Mode 4 may achieve both energy efficiency and low latency. Further, the gNB may use beam 1420 to perform transmission and reception, and the WTRU may use beam 1430 to perform transmission and reception.

[0242] In an example, in order to make the network work more efficiently, the gNB may indicate the operating mode to the WTRU. As examples, three example options may be used for such indication. In one example option, the operating mode may be indicated explicitly or implicitly in the PBCH. In another example option, the operating mode may be indicated explicitly or implicitly in the SIB. In another example option, the operating mode may be indicated explicitly or implicitly in the SYNC. In another example, for Mode 3, the parameter N may be predefined or configured to be the number of WTRU RX beams participating in the operation.

[0243] Fig.151500 is a flow chart illustrating the effective operation of the TRP and determining the operation mode. As shown in the example of flow chart 1500, the WTRU may report the TX / RX beam reciprocity to the TRP or gNB 1510. Further, the TRP or gNB may collect WTRU TX / RX beam reciprocity reports from all WTRUs in the cell 1530. The TRP or gNB may decide the appropriate operation mode based on the collected feedback on the WTRU TX / RX beam reciprocity 1550. The TRP or gNB may signal the operation mode to the WTRU 1560.

[0244] A simplified RACH procedure using a reduced number of steps for random access may be used. The simplified RACH method may be designed as follows. The WTRU may send message X. For example, the WTRU may transmit a preamble and message 3, which may include an RRC connection request or a WTRU ID, etc. Further, the gNB may send message Y. For example, the gNB may send a RAR message with an RRC connection complete message or a contention resolution message, etc.

[0245] When the WTRU sends different preambles, a preamble collision does not usually occur.Message 3 may be placed on different time / frequency resources associated with the preamble sequence index.

[0246] When the WTRU sends the same preamble, a collision may occur. Since one or more Messages 3 are in the same time / frequency resource, it is possible that they will not be decoded. One embodiment includes using different time / frequency resources for the preamble by associating Message 3 with another index. For example, time / frequency resource = f(preamble index, other index).

[0247] When WTRUs send the same preamble, sometimes there is no collision if one WTRU has much more power than one or more other WTRUs. In the example, Message 3 for the higher power WTRU may be decodable. In this case, the gNB may send a PDCCH masked with a C-RNTI (which may correspond to the higher power WTRU ID), and the higher power WTRU may decode the PDCCH and PDSCH according to the received message Y. For one or more other WTRUs in the cell, since a different C-RNTI (which may be the lower power WTRU ID) is used, these WTRUs will not decode the PDCCH and therefore cannot decode the PDSCH accordingly. This example method may resolve the contention resolution issue.

[0248] In the examples provided herein, multiple RA processes may be used. In the examples, the RA process may involve the use of a channel that may be referred to as an RA channel (RACH) (e.g., for sending a transmission). For example, the transmission may be or may include, for example, a preamble that may initiate the RA process. The RA process may use another channel and still conform to the examples provided herein. As an example, the process may be a RA process when at least one transmission in the process may involve randomly selecting at least one parameter on which the transmission is based. For example, the RA process may involve randomly selecting a transmission parameter. As an example, the transmission parameter may be selected from a set or pool of configured or available candidates. The transmission parameter may be a code, a preamble, a resource (e.g., time and / or frequency resources), an identity or identifier (e.g., a WTRU ID and RNTI, etc.).

[0249] In an example, one or more RA procedure types may be used (e.g., based on the status of the WTRU). Different RA procedures may result in different delays (e.g., connection delay or access delay). For example, the status of the WTRU may be a mode or state, such as idle, connected, or suspended, etc.

[0250] As an example, the status of the WTRU may be a capability. For example, the status of the WTRU may be a state or a state regarding a parameter (e.g., timing advance). The state of a parameter may be whether the WTRU has the parameter. The state of a parameter may be the lifetime of the parameter. For example, the status of the WTRU may be a state regarding a mode (e.g., connected mode). As an example, the state (e.g., state regarding a mode) may be the length of time that has passed since the WTRU was in a mode (e.g., connected mode), or the length of time that the WTRU was in sleep or in DRX mode.

[0251] In an example, the first type of RA procedure may be referred to as a full RA procedure and the second type of RA procedure may be referred to as a simplified RA procedure.

[0252] The full RA procedure may be used interchangeably with the M-phase RA procedure, the Type 1 RA procedure, the legacy RA procedure, the LTE RA procedure, the legacy contention-based RA procedure, the legacy contention-free RA procedure, and the like.

[0253] The simplified RA procedure may be used interchangeably with the N-phase RA procedure, the type 2 RA procedure, the new RA procedure, the shortened RA procedure, the low-latency RA procedure, the modified RA procedure, and the like.

[0254] The complete RA procedure may include M (eg, M=4) phases (eg, steps), where, as an example, the WTRU may receive or transmit a message (msg) in each phase. In an example, the WTRU may receive or transmit a message in each phase.

[0255] In an example, a WTRU may transmit a msg. The msg transmitted by the WTRU may be received by an eNodeB. As an example, a WTRU may receive a msg, for example, from an eNodeB. An eNodeB may be used as a non-limiting example of a node, such as a base station or other network node.

[0256] In a non-limiting example, M may be 4. The WTRU may transmit a first msg (e.g., msg1 of type 1) in a first phase (e.g., phase 1). The WTRU may receive (or attempt to receive) a second msg (e.g., msg2 of type 1) in a second phase (e.g., phase 2). In a third phase (e.g., phase 3), as an example, the WTRU may transmit a third msg (e.g., msg3 of type 1) based on the received second msg. The WTRU may receive (or attempt to receive) a fourth msg (e.g., msg4 of type 1) in a fourth phase (e.g., phase 4). If msg4 of type 1 is received, the RA procedure may be terminated.

[0257] As an example, the WTRU may receive, obtain and / or determine one or more of the following information during a RA procedure (e.g., a complete RA procedure). The WTRU may receive, obtain and / or determine a temporary WTRU-ID. And, the WTRU may receive, obtain and / or determine a power offset value. Further, the WTRU may receive, obtain and / or determine a timing advance value (e.g., an initial timing advance value). In addition, the WTRU may receive, obtain and / or determine a coverage level. In addition, the WTRU may receive, obtain and / or determine a search space (e.g., a common search space (CSS)). In addition, the WTRU may receive, obtain and / or determine at least one configuration (e.g., a higher layer configuration).

[0258] In an example, a temporary WTRU-ID (e.g., C-RNTI) may be used during an active mode or state (e.g., RRC connected). The temporary WTRU-ID may be used for uplink and / or downlink transmissions (e.g., during an active state). The temporary WTRU-ID may be used interchangeably with C-RNTI, temporary C-RNTI, T-WTRU-ID, and the like. The WTRU-ID may be used interchangeably with IMSI, s-TMSI, P-WTRU-ID, and the like. The WTRU-ID may include a T-WTRU-ID and a P-WTRU-ID, and the like.

[0259] As an example, the WTRU may use a power offset value or transmission power level for an initial uplink transmission. The power offset value may be used when calculating the uplink transmission power for at least the initial or first uplink transmission of a data or control channel (eg, when transmitting msg3).

[0260] In an example, one or more coverage levels may be used. A coverage level may be associated with a RA resource or a set of physical RA (PRA) resources. The WTRU may determine a PRA resource to use for a transmission (e.g., based on a coverage level that may be determined or used by it). An eNodeB or other receiver receiving a transmission from the WTRU may use the PRA resources and may determine a coverage level of the WTRU (e.g., for uplink and / or downlink transmissions) based on the PRA resources.

[0261] The WTRU may receive, obtain and / or determine a search space (e.g., CSS) for a downlink control channel that the WTRU may use to receive or attempt to receive (e.g., during a RA procedure) a DL control channel. For example, one or more CSSs may be used or configured, and the search space may be determined based on a coverage level available to the WTRU in the configured CSS. The coverage level may be determined (e.g., determined by the WTRU) during the RA procedure. Based on the coverage level available to the WTRU for transmitting a RA msg, the WTRU may monitor the corresponding common search space to find a DL control channel that may be associated with a msg (e.g., a reply) from an eNodeB. After the RA procedure ends, the WTRU may monitor the DL control channel using the determined CSS.

[0262] In a further example, the RA resource may be a resource for transmitting and / or receiving a signal, channel, and / or message that may be associated with the RA process. The RA resource may be or may include one or more preambles and / or one or more time / frequency resources (e.g., resources in time and / or frequency).

[0263] PRA resources (e.g., msg1 for type 1) that may be associated with an RA procedure (e.g., a complete RA procedure) may be configured, determined, or indicated. For example, the configuration or indication of the PRA resources for the complete RA procedure may be provided in system information that may be broadcast and / or provided in a broadcast channel. As an example, the system information may include PRA resources that may be associated with a complete RA procedure, such as one or more PRA resource sets.

[0264] The simplified RA procedure may have N (e.g., N=2) phases, where the WTRU may receive or transmit a message (msg) in a phase (e.g., each phase). In an example, the value of N may be less than the value of M. In another example, the value of M may be equal to or less than the value of N.

[0265] In a non-limiting example, N may be 2. The WTRU may transmit a first msg (e.g., msg1 of type 2) in a first phase (e.g., phase 1). The WTRU may receive or attempt to receive a second msg (e.g., msg2 of type 2) in a second phase (e.g., phase 2). If msg2 of type 2 is received, the RA procedure may be completed.

[0266] For the simplified RA procedure, the WTRU may receive, obtain and / or determine a subset of information that may be received, obtained and / or determined from or for a full RA procedure. For example, during or as part of the simplified RA procedure, the WTRU may receive, obtain and / or determine a subset of information that may be received, obtained and / or determined from or for a full RA procedure.

[0267] As an example, the WTRU may acquire the T-WTRU-ID during a simplified RA procedure while the WTRU may acquire the T-WTRU-ID and the timing advance value during a full RA procedure. In an example, the WTRU acquiring the T-WTRU-ID may be or may include the WTRU receiving the T-WTRU-ID. In another example, the WTRU acquiring the T-WTRU-ID may be or may include the WTRU determining the T-WTRU-ID.

[0268] In the examples provided herein, the terms acquire, receive, and determine are used interchangeably. Type 2 msg1 may be or may include at least one of the following: a PRA preamble that may be reserved, configured, or determined for a simplified RA procedure; a PRA preamble that may provide or include information related to a WTRU-ID; a WTRU-ID; and / or an unlicensed transmission (e.g., an unlicensed PUSCH transmission, where the PUSCH may be a GL-PUSCH).

[0269] In an example, the PRA preamble may be a sequence. In an example, the PRA preamble may be a Zadoff-Chu sequence.

[0270] In a further example, a PRA preamble may be transmitted in one or more preamble resources. The PRA preamble may be randomly selected from a set of PRA preambles configured for the simplified RA procedure.

[0271] And, the WTRU-ID may be signaled (e.g., using a UL signal that may be transmitted at a determined or known time / frequency location). The time / frequency location may be determined based on at least one of a PRA preamble (e.g., a PRA preamble that may be transmitted by the WTRU for at least a portion of msg1 of type 2) and a WTRU-ID. The WTRU-ID may be at least one of a T-WTRU-ID, a P-WTRU-ID, a randomly selected WTRU-ID, and the like. The UL signal that may be transmitted may be determined in accordance with the PRA preamble. The UL signal that may be transmitted may be a known or fixed signal. The UL signal that may be transmitted may depend on the WTRU-ID. The UL signal that may be transmitted may be a PRA preamble.

[0272] In an example, the WTRU-ID may be implicitly signaled. For example, the WTRU-ID may be implicitly signaled based on a determination made of a PRA resource. In an example, the PRA resource may be a PRA preamble and / or a time / frequency resource. As an example, for a simplified RA procedure, one or more PRA preambles and / or one or more PRA time / frequency resources may be used, determined and / or configured. The WTRU may transmit a PRA preamble in a PRA time / frequency resource. For example, the WTRU may determine a PRA preamble and / or a PRA time / frequency resource based on the WTRU-ID.

[0273] In a further example, the WTRU-ID may be implicitly transmitted via the determined PRA preamble or explicitly transmitted via data resources and / or control resources. The randomly selected WTRU-ID may include an RNTI (e.g., C-RNTI). As an example, the WTRU may randomly select an RNTI within a set of RNTIs. The set of RNTIs may be a reserved RNTI and / or a configured RNTI. The set of RNTIs will not be used for WTRUs in an RRC connection and / or common functions (e.g., paging, broadcast, RAR, etc.).

[0274] Type 2 msg1 may be or may include unlicensed transmission (e.g., unlicensed PUSCH transmission). For example, one or more PUSCH types including unlicensed PUSCH (GL-PUSCH) may be defined. GL-PUSCH may include at least one of data resources, control resources, and preamble resources.

[0275] As an example, the WTRU may use GL-PUSCH (e.g., GL-PUSCH for msg1 of type-2) to send one or more of the following information. In the example, GL-PUSCH may be used to send a PRA preamble. Furthermore, GL-PUSCH may be used to send a WTRU-ID. And, GL-PUSCH may be used to send an RRC connection request (e.g., an RRC connection establishment or re-establishment request). In another example, GL-PUSCH may be used to send a coverage level. In an additional example, GL-PUSCH may be used to send a service type, such as eMBB, mMTC, and URLLC, etc. In addition, GL-PUSCH may be used to send a WTRU category or type, such as BL-WTRU, CE-WTRU, or normal WTRU, etc.

[0276] In an example, the RRC connection request may be transmitted in data resources and / or control resources. Further, the coverage level may be indicated (e.g., implicitly indicated) by the determined and / or used GL-PUSCH resources and / or the determined and / or used PRA resources. And, the service type may be a type of service requested, required, or needed by the WTRU.

[0277] One or more GL-PUSCH resources available for msg1 may be configurable. In an example, one or more GL-PUSCH resources may be configured via higher layer signaling.

[0278] In a further example, the WTRU may receive or attempt to receive msg2 of type 2. For example, the WTRU may monitor a downlink control information (DCI) message for msg2 of type 2 that may be carried in a DCI message in a DL control channel search space. In an example, the control channel search space may be a common search space. A DCI message that may carry msg2 of type 2 may be referred to as DCI-msg2.

[0279] The DL control channel search space for DCI-msg2 may be determined based on the uplink resources used for type 2 msg1 transmissions. The uplink resources may be determined based at least in part on the WTRU-ID. The RNTI that may be used for DCI-msg2 may be determined based on the uplink resources and / or the WTRU-ID used for type 2 msg1 transmissions.

[0280] In another example, the WTRU may monitor a DCI message that may indicate downlink data resources that may carry msg2 of type 2. msg2 of type 2 may include an indication of whether msg1 of type 2 was successfully received and / or whether the simplified RA procedure was successful. For example, msg2 of type 2 may include a first value (e.g., "TRUE") or a second value (e.g., "FALSE"). The first value may indicate confirmation of the WTRU-ID. The first value may indicate successful receipt of msg1 of type 2 that may correspond to a specific WTRU-ID. The second value may indicate a failure of the simplified RA procedure.

[0281] In another example, msg2 of type 2 may be a signal. For example, by transmitting the signal, it may indicate that a combination of WTRU-IDs that may be explicitly or implicitly transmitted via msg1 of type 2 is confirmed. By transmitting the signal, it may indicate that msg1 of type 2 that may correspond to a specific WTRU-ID is successfully received.

[0282] Type 2 msg2 may carry at least one of the following information: timing advance value; power offset for uplink transmission (e.g., initial uplink transmission); contention resolution message; RRC connection setup complete message; WTRU-ID or confirmation of WTRU-ID indicated by type 2 msg1 may be indicated in type 2 msg1; or one or more higher layer configurations. In an example, the information may be provided as an information element. In another example, the information may be provided as part of an information element.

[0283] In an example solution, one or more types of RA procedures may be used in a cell. For example, a first RA procedure type and a second RA procedure type may be used. The first RA procedure type may be a type 1 or a full RA procedure. The second RA procedure type may be a type 2 or a simplified RA procedure. When a first WTRU condition may be met, the first RA procedure type may be used, and when a second WTRU condition may be met, the second RA procedure type may be used.

[0284] As an example, the number of RA process types that can be used in a cell is configurable (e.g., by an eNodeB). Two are used here as a non-limiting example of the number of RA processes that can be used, configured, or indicated (e.g., by an eNodeB). Any other number can be used and still conform to the examples provided here.

[0285] For a non-limiting example with two RA procedure types, one or both RA procedure types may be used, configured, or indicated by the eNode B. For example, when one RA procedure type may be configured or indicated, then the first (e.g., type 1) RA procedure may be used. For example, when two RA procedure types may be configured or indicated, then either the first (e.g., type 1) RA procedure or the second (e.g., type 2) RA procedure may be used.

[0286] In an example, the WTRU may determine the type of RA process to be used (e.g., a type-1 or type-2 RA process) based on one or more of the following. For example, the WTRU may determine the type of RA process to be used based on the purpose of the RA process (e.g., initial access). Furthermore, when performing the RA process, the WTRU may determine the type of RA process to be used based on the mode or state of the WTRU. Furthermore, the WTRU may determine the type of RA process to be used based on whether the WTRU is changing mode, state, or status (e.g., from an inactive state to an active state, from an RRC idle or suspended state to an RRC connected or resumed state). In addition, the WTRU may determine the type of RA process to be used based on whether the WTRU is using the RA process to change mode, state, or status. In addition, the WTRU may determine the type of RA process to be used based on the type of service that the WTRU may need, use, or request (e.g., eMBB, URLLC, mMTC). In addition, the WTRU may determine the type of RA process to be used based on the WTRU type or category.

[0287] In a further example, the WTRU may determine the RA procedure type (e.g., the RA procedure type to be used) based on the purpose of the RA procedure (e.g., random access). As an example, the WTRU may use a first type (e.g., type 1 or full) RA procedure for initial access. As an example, after performing cell detection and cell ID determination, which may be based on a cell search procedure, the WTRU may perform initial access.

[0288] In another example, the WTRU may determine the RA process type based on the mode, state, or condition of the WTRU. For example, the WTRU may determine the RA process type to be used based on the mode, state, or condition of the WTRU. In the examples provided here, the terms mode, state, and condition are used interchangeably. For example, when switching from an inactive (e.g., idle, DRX, or suspended) state to an active (e.g., connected or resumed) state, the WTRU may use a first type (e.g., type 1 or complete) RA process or a second type (e.g., type 2 or simplified) RA process. Whether type 1 or type 2 is used may be determined based on one or more other factors, such as the length of time the WTRU may be in an inactive state.

[0289] In an additional example, the WTRU may determine the RA procedure type based on the type of service that may be used, requested, needed, or required by the WTRU. For example, the WTRU may determine the type of RA procedure to be used based on the type of service that may be used, requested, needed, or required by the WTRU. For example, when the WTRU may use, request, need, or require an eMBB service type, the WTRU may use a first type (e.g., type 1 or full) RA procedure. As an example, when the WTRU may use, request, need, or require a URLLC service type, the WTRU may use a second type (e.g., type 2 or simplified) RA procedure.

[0290] Furthermore, when switching from an inactive state (e.g., RRC Idle) to an active state (e.g., RRC Connected), the WTRU may determine the RA procedure type based on at least one of: the inactive state time, the WTRU location, and / or an associated cell ID (e.g., a cell ID of a cell with which the WTRU can communicate to perform the RA procedure). As an example, when switching from an inactive state to an active state, the WTRU may determine the RA procedure type to be used.

[0291] In an example, if the WTRU's inactivity time before switching to the active state is shorter than a predefined threshold, the WTRU may use a second type (e.g., type 2 or simplified) RA procedure. Otherwise, a first type (e.g., type 1 or full) RA procedure may be used.

[0292] In another example, during the inactive state time, if the WTRU's location change is less than a predefined threshold, the WTRU may use a second type (e.g., type 2 or simplified) RA procedure. Otherwise, a first type (e.g., type 1 or full) RA procedure may be used.

[0293] The change in the WTRU's position may be derived, calculated, measured or determined based on a difference in the WTRU's position. As an example, the difference in position may be a difference between a position before the inactivity state (e.g., at or near the beginning of the inactivity state) and a current position when performing an RA procedure or determining the type of RA procedure to use. In an example, the change in position may be derived, calculated, measured or determined using GPS or Observed Time Difference of Arrival (OTDOA) data.

[0294] The change in the WTRU's position may be derived, calculated, measured or determined based on a change in a received signal time difference (RSTD) of a signal (e.g., a CRS or PRS). The RSTD may be measured as a received time difference of signals from two cells or eNodeBs, at least one of which may be a serving cell or eNodeB for the WTRU. The reference value may be a value determined at or near the beginning of an inactive state. The current value may be a value determined when performing an RA procedure or when determining the type of RA procedure to be used. The change may be the difference between the reference value and the current value.

[0295] In an example, the WTRU location change may be derived, calculated, measured or determined based on the TX-RX time difference drift during the inactivity time. In another example, instead of determining the location change, the WTRU may use the determination of the RSTD change (e.g., during the inactivity period) to determine the type of RA procedure to use. A second type (e.g., type 2 or simplified) RA procedure may be used for changes determined to be below a threshold. A first type (e.g., type 1 or full) RA procedure may be used for changes determined to be above a threshold.

[0296] In an additional example, rather than determining a change in location, the WTRU may instead use a determination of a change in TX-RX time difference or TX-RX time difference drift (e.g., during an inactive state) to determine the type of RA procedure to use. A second type (e.g., type 2 or simplified) RA procedure may be used for a determined change below a threshold. A first type (e.g., type 1 or full) RA procedure may be used for a determined change above a threshold.

[0297] In another example, if the associated cell ID is different before and after the inactivity state, the WTRU may use a first type (e.g., type 1 or complete) RA procedure. In an example, the associated cell ID may be a cell ID of a serving cell with which the WTRU may perform a RA procedure.

[0298] The WTRU may determine the RA procedure type according to one or more embodiments or examples described herein. Furthermore, the WTRU may perform the determined RA procedure.

[0299] Fig.161600 is a flow chart illustrating an example beam reciprocity based random access method and process. The example shown in flowchart 1600 may also illustrate a beam correspondence based random access method and process. Beam reciprocity or beam correspondence may be indicated by a PBCH with a mask in the PBCH payload, wherein the mask has additional details (e.g., RACH timing). As an example, the gNB may generate a PBCH payload 1610. And, the gNB may generate a CRC 1620. Further, the gNB may mask the generated CRC 1630 with a sequence that depends on the TX / RX reciprocity. The gNB may then concatenate the PBCH payload and the masked CRC 1640. The gNB may then transmit the PBCH payload to which the masked CRC is concatenated by the gNB. As a result, the WTRU may receive beam reciprocity or beam correspondence information 1650 indicated by the masked PBCH, the PBCH payload, or both.

[0300] In addition, the WTRU may determine the status of the WTRU or the time value of the WTRU. For example, the WTRU may determine the location, beam RSRP, cell ID, state, time elapsed since the last TA or time in state, etc. Based on the status of the WTRU and / or the time value of the WTRU (e.g., the status does not change, the status changes, or the time value is less than a threshold), the WTRU may select different random access methods and procedures 1670. For example, the WTRU may select either a 4-step or 2-step random access method and procedure, or a full random or simplified random access method and procedure. In an example, when the status of the WTRU changes, or when the value is greater than or equal to a threshold, the WTRU may select a full four-step RACH procedure 1675. In an example, the status of the WTRU may refer to the location of the WTRU, beam RSRP, cell ID, state of the WTRU, and the value of the WTRU relative to a threshold, etc. Further, when the status changes or when the value is less than a threshold, the WTRU may select a simplified RACH procedure 1680. In an example, the simplified RACH procedure may be a two-step RACH procedure.

[0301] The indicated beam reciprocity or beam correspondence information received by the WTRU may be used to determine one or more UL directions and timings for RACH based on the DL beam and the beam reciprocity or beam correspondence information. In an example, the one or more UL directions and timings may be associated with a DL beam.

[0302] The WTRU may use the determined timing and based on the beam reciprocity information to perform a selected RACH procedure 1695 or similar procedure in the determined one or more UL beams.

[0303] Although the example solutions described herein consider LTE, LTE-A, NR or 5G dedicated protocols, it should be understood that the solutions described herein are not limited to such protocols or scenarios and are also applicable to other wireless systems or other wireless technologies.

[0304] Although the features and elements are described above in a specific combination or order, one of ordinary skill in the art will recognize that each feature or element can be used alone or in any combination with other features and elements. In addition, the methods described herein can be implemented in a computer program, software, or firmware that is incorporated into a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electrical signals (transmitted via wired and wireless connections) and computer-readable media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, buffer memory, semiconductor storage devices, magnetic media (such as internal hard disks and removable disks), magneto-optical media, and optical media (such as CD-ROM discs and digital versatile discs (DVDs)). A processor associated with the software can be used to implement a radio frequency transceiver used in a WTRU, UE, terminal, base station, RNC, or any computer host.

Claims

1. A wireless transmit / receive unit (WTRU), the WTRU comprising: The processor is configured as: Receive synchronization signal (SS) / physical broadcast channel (PBCH) block transmissions; determining an SS / PBCH block index based on information associated with the SS / PBCH block transmission; determining a physical random access channel (PRACH) resource based on the determined SS / PBCH block index; transmitting a first message, the first message comprising a PRACH preamble and an ungranted physical uplink shared channel (PUSCH), wherein the PRACH preamble is associated with a two-step random access procedure and the PRACH preamble is transmitted using the determined PRACH resources; as well as A second message is received in response to the first message, the second message including contention resolution.

2. The WTRU of claim 1 , wherein the information associated with the SS / PBCH block transmission is derived from a demodulation reference signal (DMRS) sequence.

3. The WTRU of claim 2, wherein the DMRS sequence is transmitted in the SS / PBCH block transmission.

4. The WTRU of claim 1 , wherein the information associated with the SS / PBCH block transmission is derived from one or more PBCH payload bits.

5. The WTRU of claim 1, wherein the SS / PBCH block index corresponds to a beam subset.

6. The WTRU of claim 5, wherein the subset of beams comprises a single beam.

7. The WTRU of claim 6, wherein one or more payload bits are used to indicate the single beam.

8. The WTRU of claim 1, wherein the PRACH resources include one or more of a preamble resource, a time resource, and a frequency resource.

9. The WTRU of claim 1, wherein the PRACH resource is determined based on the SS / PBCH index using one or more of a time resource or a frequency resource.

10. A method comprising: Receive synchronization signal (SS) / physical broadcast channel (PBCH) block transmissions; determining an SS / PBCH block index based on information associated with the SS / PBCH block transmission; determining a physical random access channel (PRACH) resource based on the determined SS / PBCH block index; transmitting a first message, the first message comprising a PRACH preamble and an ungranted physical uplink shared channel (PUSCH), wherein the PRACH preamble is associated with a two-step random access procedure and is transmitted using the determined PRACH resources; as well as A second message is received in response to the first message, the second message including contention resolution.

11. The method of claim 10, wherein the information associated with the SS / PBCH block transmission is derived from a demodulation reference signal (DMRS) sequence.

12. The method of claim 11, wherein the DMRS sequence is transmitted in the SS / PBCH block transmission.

13. The method of claim 10, wherein the information associated with the SS / PBCH block transmission is derived from one or more PBCH payload bits.

14. The method of claim 10, wherein the SS / PBCH block index corresponds to a beam subset. The method of claim 14 , wherein the subset of beams comprises a single beam.

16. The method of claim 15, wherein one or more payload bits are used to indicate the single beam.

17. The method according to claim 10, wherein the PRACH resource comprises one or more of a preamble resource, a time resource, and a frequency resource.

18. The method of claim 10, wherein the PRACH resource is determined based on the SS / PBCH index using one or more of time resources or frequency resources.

19. A base station, comprising a processor, wherein the processor is configured to: Transmits synchronization signal (SS) / physical broadcast channel (PBCH) block transmissions; receiving a first message, the first message comprising a physical random access channel (PRACH) preamble and an ungranted physical uplink shared channel (PUSCH), wherein the PRACH preamble is associated with a two-step random access procedure and the PRACH preamble is received using a PRACH resource, wherein: The SS / PBCH block transmission is associated with a SS / PBCH block index, and The SS / PBCH block index is associated with the PRACH resource; and A second message is transmitted in response to the first message, the second message including an indication of contention resolution.

20. A wireless transmit / receive unit (WTRU), the WTRU comprising: A processor, wherein the processor is configured to: determining a downlink beam that satisfies a signal strength rule; receiving a first message using the downlink beam, wherein the first message indicates transmission reception point (TRP) reciprocity information; determining one or more uplink beams associated with the TRP reciprocity information; as well as A second message is sent on the determined one or more uplink beams.

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