Coverage extension by preamble repetition

Abstract

A device, method, and system for coverage extension. The bundle of preamble repeat transmissions is transmitted in response to a Reference Signal Received Power (RSRP) being below a threshold and a Random Access (RA) procedure being initiated. A Random Access Response (RAR) window is monitored for a Random Access Radio Network Temporary Identity (RA-RNTI) corresponding to the preamble repeat transmission. In some implementations, each of the preamble repeat transmissions is transmitted based on a spatial filter that is different from other of the preamble repeat transmissions. In some implementations, each of the preamble repeat transmissions includes a preamble index that is different from the preamble index of other of the preamble repeat transmissions. In some implementations, the spatial filter includes a transmit (Tx) beam. In some implementations, the bundle of preamble repeat transmissions includes a retransmission of msg1.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 308,471, filed in the United States on February 9, 2022, and U.S. Provisional Patent Application No. 63 / 250,017, filed in the United States on September 29, 2021, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] In older new radio (NR) networks, a wireless transmit receive unit (WTRU) cannot retransmit a random access preamble (msg1) in a random access channel procedure (RACH) unless the monitoring window for the random access response (msg2) expires without the WTRU receiving a response from the gNB. Under some conditions, the gNB's preamble correlator may not be able to correctly decode the preamble. Summary of the Invention

[0003] Devices, methods, and systems for coverage extension are described herein. For example, transmission repetition and / or adaptation may be performed by a WTRU during a random access procedure. One or more transmissions sent by the WTRU during the random access procedure may be repeated and / or adapted by the WTRU. For example, the WTRU may transmit a RACH message 1 (e.g., Msg1 or a physical random access channel (PRACH) preamble) and one or more repetitions of the RACH message 1. The repetition may result in an increased probability of Msg1 detection in the network (e.g., a gNB). The repetition of the RACH Msg1 may reduce the overall latency associated with random access for the WTRU, for example, during poor coverage conditions.

[0004] The WTRU may be configured with one or more local beam sets for the random access procedure. For example, the WTRU may be configured to select one or more downlink beams. Each downlink beam may be associated with a respective local beam set. For example, a local beam set may consist of relatively narrow beams associated with a relatively wide beam selected by the WTRU. The WTRU may determine corresponding UL beams associated with one or more beams of the local beam set. The UL beams may be associated with RACH resources. The WTRU may transmit RACH msg1 by repeating transmission of msg1 on the associated RACH resources of the UL beam.

[0005] As an example, a WTRU may be configured to receive configuration information indicating one or more reference signals (RSs) associated with a first synchronization signal block (SSB) and a respective set of one or more random access channel (RACH) occasions (RACH occasions, ROs) for each of the one or more RSs. The first SSB may be associated with a downlink beam. The one or more RSs may be associated with a local beam set. The local beam set may be associated with a downlink beam corresponding to the first SSB. A network (e.g., a gNB) may broadcast multiple SSBs, and one or more (e.g., each) of the multiple SSBs may be associated with a corresponding local beam set. The RS associated with the first SSB may indicate multiple beams in the local beam set. For example, each beam in the local beam set may be associated with a respective reference signal of the RS. Thus, by measuring the RSs, the WTRU may determine which beam in the local beam set has the strongest signal quality.

[0006] For example, the WTRU may determine a subset of RSs associated with a first SSB. The subset of RSs may correspond to the strongest beams in a local beam set associated with the first SSB. Each of the subset of RSs (e.g., a selected beam in the local beam set) may be associated with a corresponding RACH preamble and / or RACH occasion (RO). The WTRU may be configured to transmit a first preamble (e.g., RACH msg1) over a first RO associated with a first RS in the determined subset and transmit a second preamble (e.g., RACH msg1) on a second RO associated with a second RS in the determined subset. The first and second preambles may be the same or different preambles.

[0007] The WTRU may receive multiple random access responses (RARs). For example, the WTRU may receive a first RAR including a first grant and a second RAR including a second grant. The first RAR may be associated with a first RO, and the second RAR may be associated with a second RO. In response, the WTRU may transmit a message according to the first grant and a repetition of the message according to the second grant. The messages may correspond to RACH message 3. The transmission according to the first grant may be associated with a first spatial filter associated with the first RO, and the transmission according to the second grant may be associated with a second spatial filter associated with the second RO. The spatial filters may be associated with respective local beams in a local beam set. Using different spatial filters for RACH message 3 transmissions may increase the probability of successful reception of the message in the network (e.g., gNB). In one example, the WTRU may transmit a second repetition of the message using a third grant, where the transmission using the third grant uses a third spatial filter associated with the third RO.

[0008] To enable the WTRU to evaluate / measure multiple local beam sets associated with different SSBs, the configuration information received by the WTRU may indicate, for each of the multiple SSBs, a respective RS and an associated set of one or more ROs. Thus, each SSB may be associated with a respective multiple RS, and different RSs within the multiple may correspond to different beams in the local beam set for that SSB. The RS may also be an SSB or another type of reference signal (e.g., CSI-RS). The WTRU may first select a first SSB from the multiple SSBs and then select a subset of beams in the local beam set corresponding to the first SSB based on measurements of the reference signals associated with the SSB.

[0009] In one example, the bundle of preamble repeat transmissions is transmitted in response to a reference signal received power (RSRP) being below a threshold and a random access (RA) procedure being initiated. A random access response (RAR) window is monitored for a random access radio network temporary identity (RA-RNTI) corresponding to the preamble repeat transmission. In some implementations, each of the preamble repeat transmissions is transmitted based on a spatial filter that is different from the other ones of the preamble repeat transmissions. In some implementations, each of the preamble repeat transmissions includes a preamble index that is different from the preamble index of the other ones of the preamble repeat transmissions. In some implementations, the spatial filter includes a transmit (Tx) beam. In some implementations, the bundle of preamble repeat transmissions includes a retransmission of msg1. [Brief explanation of the drawings]

[0010] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, in which like reference numerals indicate similar elements and in which:

[0011] [Figure 1A] 1 is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented. [Figure 1B] 1B is a system diagram illustrating an exemplary wireless transmit / receive unit (WTRU) that may be used within the communication system illustrated in FIG. 1A, according to one embodiment. [Figure 1C] 1A is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communication system illustrated in FIG. 1A, according to one embodiment. [Figure 1D]1B is a system diagram illustrating a further exemplary RAN and a further exemplary CN that may be used within the communication system illustrated in FIG. 1A, according to one embodiment. [Figure 2] 1 is a graph illustrating an exemplary aspect of the present invention that may be implemented. [Figure 3A] This is a diagram of a wide beam SSB. [Figure 3B] This is a diagram of a narrow beam SSB. [Figure 4] 4 is a graph showing RACH occasions corresponding to the SSB of FIG. 3; [Figure 5] 10 is an illustration of a WTRU transmission of a preamble for beam sweeping. [Figure 6] 10 is an illustration of an example of a WTRU performing a random access procedure using repetition. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1A is a diagram illustrating an example communication system 100 in which one or more disclosed embodiments may be implemented. Communication system 100 may be a multiple-access system that provides content, such as voice, data, video, messaging, broadcasts, etc., to multiple wireless users. Communication system 100 may enable multiple wireless users to access such content through sharing of system resources, including wireless bandwidth. For example, the communication system 100 may use one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multicarrier (FBMC), etc.

[0013] 1A, communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a station (STA), may be configured to transmit and / or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a mobile phone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and application (e.g., remote surgery), an industrial device and application (e.g., robots and / or other wireless devices operating in an industrial and / or automated processing chain context), a home electronic device, a device operating in a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be referred to interchangeably as a UE.

[0014] The communications system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communications networks, such as the CN 106, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNode B (eNB), a Home Node B, a Home eNode B, a next generation Node B such as a gNode B (gNB), a new radio (NR) Node B, a site controller, an access point (AP), a wireless router, etc. Although the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0015] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage to a particular geographic area, which may be relatively fixed or may change over time. Coverage may include the capture area of ​​a cell, and a cell is considered a serving cell if it is measured by a WTRU as the strongest serving cell (based on RSRP or SS measurements). Cells may be further divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In one embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in desired spatial directions.

[0016] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0017] More specifically, as noted above, the communications system 100 may be a multiple-access system and may employ one or more channel access schemes, such as, for example, CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base station 114a and the WTRUs 102a, 102b, 102c of the RAN 104 may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 116 using wideband CDMA (WCDMA). WCDMA may include communications 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).

[0018] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0019] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using NR.

[0020] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may jointly implement LTE radio access and NR radio access, e.g., using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions transmitted to / from multiple types of base stations (e.g., eNBs and gNBs).

[0021] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement a wireless technology such as IEEE 802.11 (i.e., Wireless Fidelity, WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access, WiMAX), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), or the like.

[0022] 1A may be, for example, a wireless router, a Home Node B, a Home eNode B, or an access point and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, etc. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may establish a picocell or a femtocell using a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.). As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not need to access the Internet 110 through the CN 106.

[0023] The RAN 104 may communicate with the CN 106, which may be any type of network configured to provide voice, data, application, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have various quality of service (QoS) requirements, such as different throughput, latency, error tolerance, reliability, data throughput, mobility, etc. The CN 106 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions such as user authentication. Although not shown in FIG. 1A , it will be understood that the RAN 104 and / or CN 106 may communicate directly or indirectly with other RANs that use the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may utilize NR radio technology, the CN 106 may also communicate with another RAN (not shown) employing GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0024] The CN 106 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network providing plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), the user datagram protocol (UDP), and / or the internet protocol (IP) of the TCP / IP Internet protocol suite. The networks 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the network 112 may include another CN connected to one or more RANs, which may use the same RAT as the RAN 104 or a different RAT.

[0025] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links.) For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with a base station 114a that may use a cellular-based wireless technology and a base station 114b that may use an IEEE 802 wireless technology.

[0026] 1B is a system diagram illustrating an exemplary WTRU 102. As shown in FIG. 1B, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be understood that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0027] The processor 118 may be a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to a transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1B depicts the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0028] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0029] 1B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0030] The transceiver 120 may be configured to modulate signals transmitted by the transmit / receive element 122 and demodulate signals received by the transmit / receive element 122. As mentioned above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as, for example, NR and IEEE 802.11.

[0031] The processor 118 of the WTRU 102 may be coupled to, and may receive user-entered data from, a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light-emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. Note that the processor 118 may access information from and store data in any type of suitable memory, such as non-removable memory 130 and / or removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a Subscriber Identity Module (SIM) card, a memory stick, a Secure Digital (SD) memory card, etc. In other embodiments, the processor 118 may access information from and store data in memory that is not physically located on the WTRU 102, such as on a server or home computer (not shown).

[0032] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control the power to other components in the WTRU 102. The power source 134 may be any suitable device for providing power to the WTRU 102. For example, the power source 134 may include one or more dry cells (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0033] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or instead of information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may obtain location information by way of any suitable location determination method while remaining consistent with an embodiment.

[0034] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or videos), a Universal Serial Bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth module, a Frequency Modulated (FM) radio unit, a digital music player, a media player, a video game player module, an internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, etc. The peripherals 138 may include one or more sensors. The sensor may be one or more of a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor, a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, a humidity sensor, and the like.

[0035] The WTRU 102 may include a full-duplex radio where the transmission and reception of some or all of the signals (e.g., associated with a particular subframe on both the UL (e.g., for transmission) and DL (e.g., for reception)) may be simultaneous and / or together. The full-duplex radio may include an interference management unit to reduce and or substantially eliminate self-interference either through hardware (e.g., a choke) or signal processing via a processor (e.g., via a separate processor (not shown) or processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio where the transmission and reception of some or all of the signals (e.g., associated with a particular subframe on either the UL (e.g., for transmission) or DL ​​(e.g., for reception)) may be simultaneous and / or together.

[0036] 1C is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As mentioned above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using E-UTRA radio technology. The RAN 104 may also communicate with the CN 106.

[0037] The RAN 104 may include eNode-Bs 160a, 160b, and 160c, although it will be understood that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, and 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In an embodiment, the eNode-Bs 160a, 160b, and 160c may implement MIMO technology. Thus, the eNode-B 160a may, for example, use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0038] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling, etc. in the UL and / or DL. As shown in FIG. 1C, the eNode-Bs 160a, 160b, 160c may communicate with each other via an X2 interface.

[0039] 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN), packet data gateway (PGW) 166. While the foregoing elements are illustrated as part of the CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0040] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may function as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, activating / deactivating bearers, selecting a particular serving gateway during initial attach of the WTRUs 102a, 102b, 102c, etc. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0041] The SGW 164 may be connected to each of the eNodeBs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during inter-eNode B handover, triggering paging when DL data is available to the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

[0042] The SGW 164 may be connected to a PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0043] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional landline communications devices. For example, the CN 106 may include or communicate with an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0044] Although the WTRU is illustrated in FIGS. 1A-1D as a wireless terminal, it is contemplated that in certain representative embodiments, such a terminal may use a wired communication interface with the communication network (e.g., temporarily or permanently).

[0045] In an exemplary embodiment, the other network 112 may be a WLAN.

[0046] A WLAN in infrastructure Basic Service Set (BSS) mode may have an access point (AP) of the BSS and one or more stations (STAs) associated with the AP. The AP may have access to or interface with a distribution system (DS) or another type of wired / wireless network that carries traffic within and / or outside the BSS. Traffic originating from outside the BSS to a STA may arrive through the AP and be delivered to the STA. Traffic originating from a STA to a destination outside the BSS may be sent to the AP and transmitted to the respective destination. Traffic between STAs within a BSS may be transmitted, for example, through the AP, where the source STA may send traffic to the AP, which may deliver the traffic to the destination STA. Traffic between STAs within a BSS may be considered and / or referred to as peer-to-peer traffic. Homogeneous traffic may be transmitted between a source STA and a destination STA (e.g., directly between them) via a direct link setup (DLS). In certain exemplary embodiments, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (e.g., all of the STAs) may communicate directly with each other. The IBSS mode of communication may be referred to herein as an "ad hoc" communication mode.

[0047] When using the 802.11ac infrastructure mode of operation or a similar mode of operation, an AP may transmit beacons on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a dynamically configured width. The primary channel may be the operating channel of the BSS and may be used by STAs to establish a connection with the AP. In certain exemplary embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. With CSMA / CA, STAs (e.g., all STAs), including the AP, may sense the primary channel. If the primary channel is sensed / detected and / or determined to be active by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0048] A High Throughput (HT) STA may use a 40 MHz wide channel for communication, which may be formed, for example, through a combination of a 20 MHz primary channel and adjacent or non-adjacent 20 MHz channels.

[0049] A Very High Throughput (VHT) STA may support 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz-wide channels. The 40 MHz and / or 80 MHz-wide channels may be formed by combining multiple contiguous 20 MHz channels. A 160 MHz channel may be formed by combining eight contiguous 20 MHz channels or two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. In the 80+80 configuration, after channel encoding, the data may pass through a segment parser, which may split the data into two streams. Inverse Fast Fourier Transform (IFFT) processing and time-domain processing may be performed separately on each stream. The streams may be mapped to two 80 MHz channels, and the data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations described above for the 80+80 configuration may be reversed and the combined data may be sent to the Medium Access Control (MAC).

[0050] Sub-1 GHz operating modes are supported by 802.11af and 802.11ah. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, while 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to representative embodiments, 802.11ah may support meter-type control / machine-type communications (MTC), such as MTC devices in macro coverage areas. MTC devices may have specific capabilities, including, for example, support for (e.g., only) specific and / or limited bandwidths. An MTC device may include a battery with a battery life above a threshold (eg, to maintain a very long battery life).

[0051] WLAN systems that can support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include a channel that can be designated as a primary channel. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be configured by and / or limited by the STAs among all STAs operating in the BSS that support the minimum bandwidth operating mode. In an 802.11ah embodiment, the primary channel may be 1 MHz wide for STAs (e.g., MTC-type devices) that support (e.g., only) the 1 MHz mode, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) configuration may depend on the conditions of the primary channel. For example, if a STA (that only supports 1 MHz mode of operation) transmitting to an AP has a busy primary channel, all of the available frequency bands may be considered busy even if most of the available frequency bands are idle.

[0052] In the United States, the available frequency band that can be used by 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0053] 1D is a system diagram illustrating the RAN 104 and the CN 106 in accordance with one embodiment. As noted above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using NR radio technology. The RAN 104 may also communicate with the CN 106.

[0054] The RAN 104 may include gNBs 180a, 180b, and 180c, although it will be understood that the RAN 104 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, and 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In an embodiment, the gNBs 180a, 180b, and 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to transmit and / or receive signals to the gNBs 180a, 180b, and 180c. Thus, the gNB 180a may transmit wireless signals to and / or receive wireless signals from the WTRU 102a using, for example, multiple antennas. In one embodiment, the gNBs 180a, 180b, and 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on an unlicensed spectrum, and the remaining component carriers may be on a licensed spectrum. In one embodiment, the gNBs 180a, 180b, and 180c may implement Coordinated Multi-Point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNBs 180a and 180b (and / or 180c).

[0055] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of varying or scalable lengths (e.g., including varying numbers of OFDM symbols and / or varying lengths of absolute time).

[0056] 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 another RAN (e.g., eNode-Bs 160a, 160b, 160c, etc.). In a standalone configuration, the WTRUs 102a, 102b, 102c may utilize one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in unlicensed bands. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate with and connect to a gNB 180a, 180b, 180c while also communicating with and connecting to another RAN, such as an eNode-B 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-Bs 160a, 160b, 160c may act as mobility anchors for the WTRUs 102a, 102b, 102c, while the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0057] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support for network slicing, DC, interworking between NR and E-UTRA, routing of user plane data to User Plane Functions (UPFs) 184a, 184b, routing of control plane information to Access and Mobility Management Functions (AMFs) 182a, 182b, etc. As shown in FIG. 1D , the gNBs 180a, 180b, 180c may communicate with each other via an Xn interface.

[0058] 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While the foregoing elements are illustrated as part of the CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0059] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N2 interface and may function as a control node. For example, the AMF 182a, 182b may be responsible for user authentication of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selection of a particular SMF 183a, 183b, management of registration areas, termination of non-access stratum (NAS) signaling, mobility management, etc. The network slicing may be used by the AMF 182a, 182b to customize the CN support of the WTRUs 102a, 102b, 102c based on the type of service utilizing the WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for MTC access, etc. The AMFs 182a, 182b may provide a control plane function for switching between the RAN 104 and other RANs (not shown) employing other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as WiFi.

[0060] The SMFs 183a, 183b may be connected to the AMFs 182a, 182b in the CN 106 via an N11 interface. The SMFs 183a, 183b may also be connected to the UPFs 184a, 184b in the CN 106 via an N4 interface. The SMFs 183a, 183b may select and control the UPFs 184a, 184b and configure the routing of traffic through the UPFs 184a, 184b. The SMFs 183a, 183b may perform other functions, such as managing and assigning UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0061] The UPFs 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks such as the Internet 110 to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPFs 184, 184b may perform other functions such as routing and forwarding packets, enforcing user plane policy, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, and providing mobility anchoring.

[0062] The CN 106 may facilitate communication with other networks. For example, the CN 106 may include or communicate with an IP gateway (e.g., an IP Multiplexed Media Subsystem (IMS) server) that acts as an interface between the CN 106 and the PSTN 108. Note that the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to the local DNs 185a, 185b through the UPFs 184a, 184b via an N3 interface to the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b.

[0063] 1A-1D and the corresponding description thereof, one or more or all of the functions described herein with respect to one or more of the WTRUs 102a-102d, base stations 114a-114b, eNode-Bs 160a-160c, MME 162, SGW 164, PGW 166, gNBs 180a-180c, AMFs 182a-182b, UPFs 184a-184b, SMFs 183a-183b, DNs 185a-185b, and / or any other devices described herein may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation devices may be used to test other devices and / or simulate network and / or WTRU functions.

[0064] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or an operator network environment. For example, one or more emulation devices may perform one or more or all functions while fully or partially implemented and / or deployed as part of a wired and / or wireless communication network to test other devices in the communication network. One or more emulation devices may perform one or more or all functions while temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation devices may be directly coupled to another device for the purpose of testing and / or performing tests using over-the-air wireless communication.

[0065] One or more emulation devices may perform one or more functions, including but not limited to, while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in test scenarios in a test lab and / or in an undeployed (e.g., test) wired and / or wireless communication network to implement testing of one or more components. One or more emulation devices may be test equipment. Direct RF linkage and / or wireless communication via RF circuitry (which may, for example, include one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0066] Among others, the following abbreviations and acronyms are used herein: configured grant or cell group (CG), dynamic grant (DG), channel access priority class (CAPC), downlink feedback information (DFI), HARQ Process ID (HARQ PID), enhanced Licensed Assisted Access (eLAA), further enhanced Licensed Assisted Access (FeLAA), MAC control element (MAC CE), RACH occasion (RO), random access (RA), physical random access channel (PRACH), acknowledgement (ACK), block error rate (BLER), bandwidth part (BWP), channel access priority (CAP), clear channel assessment (CCA), cyclic prefix (CPC), and cyclic prefix (CPC). cyclic prefix (CP), e.g., conventional OFDM (relying on cyclic prefix) (CP-OFDM), channel quality indicator (CQI), cyclic redundancy check (CRC), channel state information (CSI), contention window (CW), contention window size (CWS), channel occupancy (CO), downlink assignment index (DAS),Index (DAI), Downlink Control Information (DCI), Downlink (DL), Demodulation Reference Signal (DM-RS), Data Radio Bearer (DRB), Hybrid Automatic Repeat Request (HARQ), License Assisted Access (LAA), Listen-Before-Talk (LBT), Long Term Evolution (LTE) such as 3GPP LTE R8 and later, Negative ACK (NACK), Modulation and Coding Scheme (MCS), Multiple Input Multiple Output (MIMO), New Radio (NR), Orthogonal Frequency-Division Multiplexing (OFDM), Physical Layer (PHY), Physical Random Access Channel (PRACH), Primary Synchronization Signal (PSS), Signal (PSS), Random Access Channel (or Procedure) (RACH), Random Access Response (RAR), Radio access network Central Unit (RCU), Radio Link Failure (RLF), Radio Link Monitoring (RLM), Radio Network Identifier (RNTI), Radio Resource Control (RRC), Radio Resource Management (RRM), Reference Signal (RS), Reference Signal Received Power (RSRP), Received Signal Strength Indicator (RSSI), Service Data Unit (SDU), Signal to Interference and Noise Ratio (SIR)Ratio (SINR), Sounding Reference Signal (SRS), Synchronization Signal (SS), Secondary Synchronization Signal (SSS), Switching Gap (SWG) (in self-contained subframes), Semi-Persistent Scheduling (SPS), Supplemental Uplink (SUL), Transport Block (TB), Transport Block Size (TBS), Transmission and Reception Point (TRP), Time-sensitive communications (TSC), Time-sensitive networking (TSN), Uplink (UL), Ultra-Reliable and Low Latency Communications (URLLC), Wide Bandwidth Part (WBWP), e.g., Wireless Local Area Networks (WLANs) and related technologies in the IEEE 802.xx domain.

[0067] The following terms may be used throughout this disclosure.

[0068] The term PRACH resource may be used to refer to a PRACH frequency resource. The term PRACH resource may be used to refer to a PRACH occasion (RO) (e.g., in time). The term PRACH resource may be used to refer to a preamble format (e.g., in terms of total preamble duration, sequence length, guard time duration, and / or cyclic prefix length). The term PRACH resource may be used to refer to a particular preamble sequence, preamble signature, etc. used for transmitting a preamble in a random access procedure.

[0069] The term Msg1 may be used to refer to a PRACH preamble transmission used to initiate a four-step RACH procedure. The term Msg1 may be used interchangeably with the term preamble.

[0070] The term Msg2 may be used to refer to the random access response of the four-step RACH procedure.

[0071] The term Msg3 may be used to refer to a WTRU transmission that is performed based on an uplink grant received in the random access response of the four-step RACH procedure.

[0072] The term Msg4 may be used to refer to the network transmission used for contention resolution during the four-step RACH procedure.

[0073] The term MsgA may be used to refer to the preamble on the PRACH resource and the payload transmission on the PUSCH resource in a two-step random access procedure.

[0074] The term MsgB may be used to refer to a downlink response to MsgA, which may be, for example, a success RAR, a fallback RAR, or a backoff indication.

[0075] The acronym RO may be used herein, which may refer to a RACH occasion.

[0076] The WTRU may be configured to determine channel conditions. The term channel conditions may be used to refer to any conditions related to radio / channel conditions. For example, channel conditions may be determined by the WTRU from one or more of WTRU measurements (e.g., L1 / SINR / RSRP, CQI / MCS, channel occupancy, RSSI, power headroom, exposure headroom, etc.), L3 / mobility-based measurements (e.g., RSRP, RSRQ), radio link monitoring (RLM) status, channel availability in unlicensed spectrum (e.g., whether the channel is occupied based on the determination of an LBT procedure or whether the channel is deemed to have experienced consistent LBT failures), etc. Channel measurements refer to WTRU measurements made using one or more of the aforementioned channel conditions.

[0077] The term properties of the scheduling information (e.g., uplink grant or downlink allocation) may be used herein. The properties of the scheduling information may include one or more of the following: frequency allocation, time allocation aspects such as duration, priority, modulation and coding scheme, transport block size, one or more spatial layers, one or more transport blocks carried, TCI state or SRI, one or more repetitions, and / or whether the grant is a configured grant Type 1, Type 2, or dynamic grant.

[0078] The term indication by DCI may be used herein. The indication by DCI may include one or more of the following: explicit indication by DCI fields or by RNTI used to mask the CRC of the PDCCH, and / or implicit indication by properties such as DCI format, DCI size, core set or search space, aggregation level, e.g., identity of the first control channel resource (e.g., index of the first CCE) for the DCI in cases where the mapping between properties and values ​​may be signaled by RRC or MAC.

[0079] In some implementations, Msg1 202 may be the first message in an RA procedure. In some implementations, Msg1 202 may include a random access preamble, sequence, and / or payload. In some implementations, the preamble may be generated from a cell-specific root sequence, and an offset transmission from the root sequence is used to generate the preamble. In some embodiments, repetition of Msg1 204 may be a useful tool to enhance coverage, for example, in 5G frequency ranges (e.g., FR1 and FR2). For example, a WTRU may use different transmit (Tx) beams (also referred to as spatial domain filters or spatial filters) to transmit different repetitions of msg1 202 and / or to exploit channel diversity. In some implementations, the WTRU may additionally or alternatively transmit repetitions using the same Tx beam, for example, to allow the gNB to correlate and combine preambles from the same WTRU, to allow the gNB to sweep through receive (Rx) beams, and / or to allow the gNB to correlate channels via demodulation reference signal (DMRS) or PRACH bundling.

[0080] In some implementations, decoding a single preamble from preamble repetitions may be sufficient to achieve coverage extension by leveraging channel diversity. In such implementations, a WTRU may transmit bundles of msg1 202 repetitions (e.g., using different spatial filters) and may use one or more (e.g., any) RO 204 (while still indicating that they indicated a selected synchronization signal block (SSB) per legacy behavior (e.g., according to an earlier standard or standard version)). In some embodiments, a bundle of msg1 202 repetitions may include several consecutive repeated msg1 202 (e.g., with or without gaps in the time domain). In some implementations, the RO 204 may be shared with legacy WTRUs. For example, the network may configure one or more (e.g., a maximum number) msg1 202 repetitions per bundle (e.g., that may be repeated before the expiration of the RAR window), e.g., by broadcast or dedicated signaling. If RSRP<threshold and RA is initiated, the WTRU may repeat Msg1 202, and the WTRU may monitor RAR for one or more RA-RNTIs if the Msg1 202 repetition spans two or more "RA-RNTI occasions" in the time or frequency domain (e.g., two or more PRACH resources with the same RA-RNTI value).

[0081] In some implementations, the gNB may benefit from knowing (e.g., being able to use gNB-indicated information) that Msg1 202 repetitions come from the same WTRU (e.g., for Rx beam sweeping), e.g., for better channel estimation and / or to soft-combine received preambles. In some implementations, the network may configure, e.g., by broadcast or dedicated signaling, one or more (e.g., one) subsets of Ro 204 (RO set) on which msg1 202 may be repeated, possibly along with one or more (e.g., maximum) number of repetitions or bundle size indications. In some such implementations, the WTRU may repeat Msg1 202 if RSRP<threshold and an RA is initiated. In some implementations, the WTRU may transmit bundles of msg1 202 repetitions (e.g., using different spatial filters) on the RO set 204 configured for Msg1 202 repetition. In some implementations, the WTRU may monitor the RAR for a combined RA-RNTI corresponding to the RO set, or for the RA-RNTI corresponding to one or more of the ROs in the set (e.g., the first or last RO in the set). In some implementations, one or more preambles or one or more RO partitions may be required.

[0082] The WTRU may be configured to perform Msg1 repetitions using one or more Msg1 repetition types. In some embodiments, the Msg1 202 repetition types may include transmitting repetitions on the same tx beam (e.g., spatial filter) and same preamble index, transmitting repetitions on different tx beams but the same preamble index, transmitting repetitions on the same tx beam but different preamble index, and / or transmitting repetitions on different tx beams and preamble index. Some possible parameters for each Msg1 202 repetition may include the Tx beam (e.g., spatial filter), preamble index, RO, PRACH resource, and / or Tx power, etc.

[0083] In some embodiments, one or more (e.g., a single) preamble transmissions may not be sufficient for a preamble correlator (e.g., of a gNB) to correctly decode the WTRU's preamble (e.g., when the WTRU is in potentially poor (e.g., bad) coverage or radio frequency (RF) radio conditions).

[0084] In legacy NR networks, the WTRU may retransmit Msg1 202 of the RA procedure some time (e.g., only after) the expiration of the RAR (Msg2) monitoring window without receiving a response from the network. In some implementations, Msg2 may be the second message in the random access procedure that the WTRU receives. In some implementations, Msg2 may include the RAR, backoff indication, system information configuration, grant, timing advance, payload, and / or downlink data. Furthermore, preamble retransmissions may be independent from the perspective of the gNB and may not be able to be combined with previously transmitted preambles to improve gNB detection probability. Msg1 202 repetition may be useful to increase the WTRU's link budget and / or increase the probability of Msg1 202 detection at the gNB (or other receiving device), as well as reduce the overall latency associated with random access for the WTRU in potentially poor (e.g., bad) coverage conditions.

[0085] As used herein, a WTRU may transmit or receive a physical channel or reference signal according to one or more spatial domain filters. The term "beam" may be used to refer to a spatial domain filter. As used herein, the terms spatial filter and tx beam may be used interchangeably.

[0086] In some implementations, a WTRU may transmit a physical channel or signal using the same spatial domain filter as that used to receive an RS (e.g., CSI-RS) or SS block. The WTRU transmission may be referred to as the "target," and the received RS or SS block may be referred to as the "reference" or "source." In some such implementations, the WTRU may be said to transmit the target physical channel or signal according to its spatial relationship to such RS or SS block.

[0087] In some implementations, the WTRU may transmit a first physical channel or signal according to the same spatial domain filter as that used to transmit a second physical channel or signal. The first and second transmissions may be referred to as the “target” and “reference” (or “source”), respectively. In some such implementations, the WTRU may transmit the first (target) physical channel or signal according to a spatial relationship to the second (reference) physical channel or signal.

[0088] In some implementations, the spatial relationship may be implicit, configured by RRC, or signaled by MAC CE or DCI. For example, the WTRU may implicitly transmit the PUSCH and DM-RS of the PUSCH according to the same spatial domain filter as the SRS indicated in the DCI or indicated by the SRI configured by RRC. In some implementations, the spatial relationship may be configured by RRC for the SRS resource indicator (SRI) or signaled by the MAC CE for the PUCCH. Such a spatial relationship may be referred to as a "beam indication."

[0089] In some implementations, the WTRU may receive a first (target) downlink channel or signal according to the same spatial-domain filter or spatial reception parameters as a second (reference) downlink channel or signal. For example, such an association may exist between a physical channel, such as a PDCCH or PDSCH, and its respective DM-RS. Such an association may exist when the WTRU is configured with quasi-colocation (QCL) assumption type D between corresponding antenna ports, e.g., when the first and second signals are reference signals. Such an association may be configured as a transmission configuration indicator (TCI) state. In some implementations, the WTRU may receive an indication of the association between a CSI-RS or SS block and a DM-RS, e.g., as an index into a set of TCI states configured by RRC and / or signaled by MAC CE. Such an indication may also be referred to as a "beam indication."

[0090] Some implementations may provide coverage extension through Msg1 202 repetition. For example, some implementations may include Msg1 202 resource selection.

[0091] Some implementations may include non-segment-based Msg1 202 repetition. For example, in some implementations, a WTRU may be configured with one set of PRACH preambles that the WTRU may use for both PRACH repetition mode (e.g., Msg1 202 repetition mode) and PRACH transmissions without repetition mode (e.g., Msg1 202 without repetition mode).

[0092] In some implementations, the WTRU may be configured to repeat Msg1 202 on the same RACH occasion (RO). For example, the WTRU may select and transmit using multiple (e.g., two) different PRACH resources belonging to the same RO. In one embodiment, system information may be used to indicate whether repetition of Msg1 202 should be performed. Upon receiving a system information block (SIB) indicating that repetition of Msg1 202 should be performed, the WTRU may transmit Msg1 202 more than once (e.g., repeatedly) in the same RO. In some implementations, the WTRU may further be configured with a group-common DCI that may enable or disable Msg1 202 repetition in the same RO. In some implementations, the WTRU may be configured to monitor such group-common DCI during the initial access procedure.

[0093] In some implementations, the WTRU may be configured to repeat Msg1 202 on different RACH occasions (ROs). In some such implementations, the WTRU may be configured with a set of ROs that allow repetition. For example, if the WTRU selects the first PRACH resource in the first RO, and if the WTRU allows Msg1 202 repetition, the WTRU may repeat the Msg1 202 transmission one or more times (e.g., only once) in the set of ROs that allow repetition. In some implementations, the set of ROs that allow repetition may depend on the RO selected for the initial Msg1 202 transmission. For example, the WTRU may use one or more (e.g., only one) ROs associated with the same SSB used to determine the PRACH resource for the initial Msg1 202 transmission. In an embodiment, the WTRU may be configured to use an RO associated with an SSB that is quasi-co-located (QCL) with the SSB used to determine the PRACH resource for the initial Msg1 202 transmission.

[0094] In some implementations, the WTRU may be configured to repeat the same PRACH resource / preamble for different repetition occasions. In some implementations, the WTRU may be configured to use different PRACH resources for different occasions. In some implementations, the WTRU may be configured to use a mapping, function, and / or table to determine the PRACH resource for a repetition when enabling repetition of Msg1 202. For example, in some implementations, when the WTRU selects a PRACH resource (e.g., i) for the initial transmission of Msg1 202, the WTRU may select the PRACH resource (e.g., {f1(i), f2(i), ... f) for one or more (e.g., N) repetitions, respectively. N In some implementations, the gNB (or other receiver) may use the received PRACH transmission (e.g., {f1(i), f2(i), ... f(i)}) to determine whether a Msg1 202 repetition has occurred. N (i)}) are correlated. N (.) may be configured to the WTRU in any suitable manner, such as by RRC signaling, or may be pre-configured / fixed, for example, per an appropriate specification.

[0095] In some implementations, the WTRU may select a different PRACH target received power P for each Msg1 202 iteration. PRACH,target In some implementations, P PRACH,target The WTRU pattern of Msg1 may assist the gNB in ​​determining whether a Msg1 202 repetition has occurred. In some implementations, the WTRU may use SIB signaling to determine the P for Msg1 202 repetition. PRACH,target It can be configured in a pattern or fixed in specification.

[0096] In some implementations, the WTRU may be configured to use beam sweeping for Msg1 202 repetitions, or the WTRU may be configured to not use beam sweeping for Msg1 202 repetitions. In some implementations, the WTRU may be explicitly configured to use beam sweeping or not use broadcasted system information. In some implementations, the WTRU may be configured to determine whether beam sweeping for Msg1 202 repetitions is enabled based on whether PRACH and / or DMRS bundling in Msg3 206 is enabled. In some implementations, Msg3 may be the third message in a random access procedure. In some implementations, the WTRU may transmit Msg3 206. In some implementations, Msg3 206 may include an RRC connection request, UL data, and / or other control information. In some implementations, the WTRU may be configured to use beam sweeping for Msg1 202 repetitions in a subset of ROs. In some implementations, the WTRU may be configured with a swept beam pattern for Msg1 202 repetition.

[0097] Some implementations may include partition-based Msg1 202 repetition. For example, in some implementations, a WTRU may be configured with a first set of PRACH preambles that the WTRU may use for a PRACH repetition mode (e.g., Msg1 202 repetition mode) and a second set of PRACH preambles that the WTRU may use for PRACH transmissions without a repetition mode (e.g., no Msg1 202 repetition mode). In some implementations, when operating in Msg1 202 repetition mode, the WTRU may be configured with a time pattern for repetition associated with the set of PRACH preambles configured for Msg1 202 repetition. In some implementations, the WTRU may repeat selected PRACH resources according to the configured time pattern. In some implementations, the WTRU may be configured with a periodicity associated with the set of PRACH preambles configured for Msg1 202 repetition. In some implementations, the WTRU may repeat selected PRACH resources according to the configured periodicity.

[0098] In some implementations, a WTRU may be configured with one or more sets of PRACH preambles for one or more SSBs used, transmitted, and / or monitored in a cell, and each set of PRACH preambles may be associated with a coverage level. In some implementations, the WTRU may perform measurements and / or detection of one or more SSBs used, transmitted, and / or monitored in a cell, and the WTRU may determine the SSBs and / or coverage level based on the measurements and / or detection. Based on the determined SSBs and coverage level, the WTRU may determine a set of PRACH preambles associated with the determined SSBs and coverage level. In some implementations, the WTRU may repeatedly use the determined set of PRACH preambles to perform PRACH transmissions. In some implementations, the number of sets of PRACH preambles and / or the number of supported coverage levels may vary based on the SSB or SSB index. In some implementations, the set of PRACH preambles may include one or more PRACH preambles for repetitions required to meet a particular coverage level, hi some implementations, the WTRU may determine a subset of SSBs based on the determined coverage level.

[0099] Where the number of PRACH preamble sets and / or the number of supported coverage levels may vary based on the SSB or SSB index, for example, a first set of SSBs may support a first number of coverage levels (e.g., 1, 2, 3, 4, 5), and a second set of SSBs may support a second number of coverage levels (e.g., 1, 2, 3), where the coverage levels may correspond to the number of repetitions. In an embodiment, a first subset of SSBs may be with a PRACH repetition mode (e.g., Msg1 202 repetition mode), and a second subset of SSBs may be without a PRACH repetition mode (e.g., Msg1 202 with no repetition).

[0100] Where a set of PRACH preambles may include one or more PRACH preambles for repetitions required to meet a particular coverage level, the set of PRACH preambles may be sets of PRACH resources at different time locations, the same PRACH preamble sequence may be used at different time / frequency locations for repetitions, and / or each set of PRACH preambles may correspond to a coverage level and / or number of repetitions.

[0101] Some implementations may include a PRACH repetition mode (segmented or non-segmented). In an embodiment, the WTRU may determine the PRACH repetition mode based on the SSB (or SSB-id), where a first PRACH repetition mode may be non-segmented-based Msg1 202 repetition and a second PRACH repetition mode may be segmented-based Msg1 202 repetition. In some implementations, the WTRU may determine an SSB from among one or more SSBs used, transmitted, or detected in the cell, and the WTRU may use its associated PRACH repetition mode if coverage enhancement needs to be performed. In some implementations, the WTRU may determine the PRACH repetition mode based on the WTRU capabilities (e.g., whether beam support is supported), and the WTRU may determine an SSB in the set of SSBs associated with the determined PRACH repetition mode.

[0102] In some implementations, an SSB may be associated with two PRACH resource types, where a first PRACH resource type may be associated with a first PRACH repetition mode (e.g., non-segment-based Msg1 202 repetition) and a second PRACH resource type may be associated with a second PRACH repetition mode (e.g., segment-based Msg1 202 repetition). In some implementations, the WTRU may determine the PRACH repetition mode based on one or more of the following: measurements of the SSB, one or more SSBs that meet one or more predetermined conditions, and / or WTRU capabilities.

[0103] When the WTRU determines the PRACH repetition mode based on measurements of an SSB, for example, if the measurement quality of the associated SSB is below a threshold, the WTRU may determine a first PRACH resource type; otherwise, the WTRU may determine a second PRACH resource type.

[0104] When the WTRU determines the PRACH repetition mode based on one or more SSBs that satisfy one or more predetermined conditions, the predetermined conditions may include one or more of the following: a received quality (e.g., L1-RSRP, L1-SINR) higher than a threshold, the number of supported coverage levels, the degree of (e.g., maximum) supported coverage levels (e.g., based on BLER, SINR, or RSRP), and / or support for PRACH preamble repetition.

[0105] If the WTRU determines the PRACH repetition mode based on the WTRU capabilities, the WTRU capabilities may include, for example, whether the WTRU has beam-capable capability. For example, if the WTRU has beam-capable capability, the WTRU may decide to use partition-based Msg1 202 repetition; otherwise, the WTRU may decide to use non-partition-based Msg1 202 repetition.

[0106] The WTRU may be configured to receive multiple SSBs. Some implementations may include an indication of multiple SSBs. For example, the WTRU may be configured with an association between an SSB and a PRACH resource (e.g., a set of ROs and / or preambles). In some implementations, the WTRU may be configured with one or more (e.g., a maximum number) "N" SSBs to indicate as part of a msg1 202 repetition bundle. In some implementations, the WTRU may measure one or more SSBs and select one or more SSBs measured with an RSRP above a configured (e.g., pre-configured) SSB-rsrp threshold. In some implementations, for the msg2 repetition bundle, the WTRU may select the PRACH resource (e.g., ROs and / or preambles) associated with the selected N measured SSBs (e.g., the N SSBs with the strongest signal strength measurements), or an SSB measured with ssb-rsrp > configured threshold ≦ N. In some implementations, the WTRU may change the spatial filter associated with each beam pair. For example, if the WTRU selects SSBs 3, 4, and 5 as the strongest SSBs, the WTRU may repeat msg1 202 on the ROs associated with SSBs 3, 4, and 5, and the WTRU may select a spatial filter associated with each selected beam. In some implementations, the WTRU may adjust or compensate the preamble transmit power or preamble target receive power according to the measured path loss associated with the selected beam pair (e.g., the selected SSB and / or the selected spatial filter / Tx beam).

[0107] In some implementations, the WTRU may select multiple SSBs that are contiguous in time. For example, the WTRU may repeat msg1 202 on the ROs corresponding to the selected SSBs if there are no gaps in the time domain associated with their SSB reception times. In some implementations, the WTRU may repeat msg1 202 on the ROs corresponding to the selected SSBs if the ROs associated with the selected SSBs are contiguous in the time domain (e.g., without RO gaps).

[0108] In some implementations, the WTRU may be configured with a threshold value, and the WTRU may select multiple SSBs such that their combined ssb-rsrp is greater than the threshold value. For example, in a coverage-limited scenario, the WTRU may not be able to find any ssb-rsrp greater than the configured threshold. In this case, in some embodiments, the WTRU may decide to select multiple SSBs such that their combined ssb-rsrp is greater than the threshold value. In some implementations, such a threshold value may be configured separately from the threshold value used in the standard initial access procedure, e.g., because the threshold value is intended to be compared with the combined RSRP of the SSBs. For example, the WTRU may select SSBs 3, 4, and 5 such that the combined ssb-rsrp of the ssb-rsrp corresponding to SSBs 3, 4, and 5 is greater than the threshold value. In some implementations, the WTRU may change the spatial filter associated with each beam pair. For example, if the WTRU selects SSBs 3, 4, and 5 as SSBs (e.g., based on measurements), in some implementations, the WTRU may repeat msg1 202 on the ROs associated with SSBs 3, 4, and 5, and in some implementations, the WTRU may select a spatial filter associated with each selected beam.

[0109] In some implementations, the WTRU may be pre-configured with a selected combination of SSBs where the WTRU is configured with one or more (e.g., the maximum number) "N" SSBs to indicate part of a msg1 202 repetition bundle. In some implementations, the WTRU may be pre-configured with a group of SSB IDs (e.g., [1, 3, 5], [2, 4, 6]). In this example, if the WTRU is configured with N=3, the WTRU may measure the RSRP of SSB1, SSB3, and SSB5. Additionally or alternatively, the WTRU may measure the RSRP of SSB2, SSB4, and SSB6. The WTRU may calculate the combined RSRP for each group of SSBs [SSB1, SSB3, SSB5] and [SSB2, SSB4, SSB6], and the WTRU may decide to use the group of SSBs with the highest combined RSRP for diversity transmission. The WTRU may determine to use the selected group of SSBs if the combined RSRP exceeds a preconfigured threshold. Additionally or alternatively, in some implementations, the WTRU may determine the group of SSBs for diversity transmission depending on the number of SSBs whose RSRP exceeds a preconfigured threshold. In embodiments, the SSB ID combinations may be mutually exclusive, e.g.,

[0012] ,

[0034] , etc., or overlapping combinations, e.g.,

[0123] ,

[0234] , etc. Examples of diversity transmission schemes may include the embodiments used herein (e.g., the WTRU may repeat msg1 202 on the ROs associated with the selected group of SSBs, the WTRU may select a spatial filter associated with each selected beam, etc.).

[0110] In some implementations, the WTRU may select one or more (e.g., multiple) SSBs. If one or more (e.g., multiple) SSBs have a combined RSRP greater than a preconfigured threshold, the WTRU may decide to perform a two-step RACH, e.g., the WTRU may decide to send both a PRACH preamble and msg3 206 using the diversity scheme described herein. In an example, the WTRU may have selected SSBs 3, 4, and 5 as SSBs (e.g., based on measurements). In some implementations, the WTRU may repeat msg1 202 and msg3 206 on the ROs associated with SSBs 3, 4, and 5. Additionally or alternatively, the WTRU may select a spatial filter associated with each selected beam.

[0111] Some implementations may include Msg2 monitoring and coverage extension. For example, some implementations may include RA-RNTI monitoring. In some implementations, the WTRU may monitor the PDCCH for reception of one or more Msg2s after transmitting a msg1 202 repetition bundle. In some implementations, the WTRU may monitor the PDCCH for reception of one or more (e.g., multiple) RARs, possibly multiplexed within the same Msg2. In some implementations, the WTRU may monitor one or more (e.g., multiple) PDCCHs or one or more (e.g., multiple) Msg2s scrambled with one or more RA-RNTIs (e.g., if the transmitted msg1 202 spans two or more of the PRACH resources associated with different RA-RNTI values).

[0112] In some implementations, for a msg1 202 repetition bundle transmitted on a set of ROs preconfigured for preamble repetition, the WTRU may monitor the PDCCH for a combined RA-RNTI associated with the RO set. For example, the combined RA-RNTI may be calculated based on the RA-RNTI values ​​associated with each RO on which msg1 202 was repeated. In an embodiment, the combined RA-RNTI may correspond to the RA-RNTI value of the first or last RO associated with the RO set.

[0113] In some implementations, from among multiple received RARs, the WTRU may select a single RAR and discard the remaining RARs. In some implementations, the WTRU may implicitly or explicitly indicate in the RAR that the other RARs were due to transmissions of msg1 202 repeat bundles coming from the same WTRU.

[0114] Some implementations may involve repetition of Msg3 206. For example, among multiple received RARs, in some implementations, the WTRU may transmit msg3 206 from multiple RARs signaled using multiple grants. In some implementations, for transmitting msg3 206, the WTRU may consider grants in the received RARs scrambled with the RA-RNTI corresponding to the RO in which msg1 202 was repeated.

[0115] In some implementations, the WTRU may use multiple selected grants to transmit repeated copies of a single TB. For grants of the same TBS and / or grants that may not overlap (e.g., are non-overlapping) in the time domain, in some implementations, the WTRU may use the grants for repetition of msg3 206. In some implementations, the WTRU may indicate, for example, in the first copy, the number of grants used to repeat msg3 206. In some implementations, the WTRU may use one or more (e.g., all) of the grants with the same TBS to repeat the Msg3 206 TB. Figure 2 is a graph illustrating a typical scenario of an RA procedure initiated with Msg1 202 coverage extension with msg1 202 repetition. Figure 2 shows Msg4 as the fourth message in the RA procedure.

[0116] In some implementations, the WTRU may use multiple selected grants to transmit multiple TBs either on different HARQ processes or on a single HARQ process. To determine the different HARQ process IDs, in some implementations, the WTRU may determine the HARQ process associated with each grant according to the RAR reception time. For example, in some implementations, the WTRU may associate the first grant received in time with HARQ process 0, the second grant received with HARQ process 1, the third grant received with HARQ process 2, etc. Additionally or alternatively, in some implementations, the WTRU may determine the HARQ process ID from the RAR reception time occasion (e.g., slot number), the SSB (or RO associated with the SSB) associated with the RAR, or a time offset from the SSB transmission time.

[0117] In some implementations, the WTRU may transmit a TB segment on a single HARQ process (e.g., HARQ process 0) using multiple selected grants. In some implementations, the WTRU may segment the msg3 206 TB into multiple segments and transmit them via the received grant on Msg2 scrambled with the RA-RNTI associated with the transmitted msg1 202. In some implementations, multiple smaller grants may be beneficial for Msg3 206 coverage enhancement. In some implementations, the WTRU may view a TB transmission as a TB transmitted over multiple slots, with each slot corresponding to a different grant.

[0118] For grants that overlap in the time domain, in some implementations, the WTRU may select a single grant and discard the remaining overlapping grant(s). If, among multiple signaled grants associated with the monitored RA-RNTI, one or more of the grants are signaled with msg3 206 repetitions, in some implementations, the WTRU may prioritize the selection of such grant and / or discard one or more other grants without repetitions.

[0119] Among multiple signaled grants associated with one or more monitored RA-RNTIs, in some implementations, the WTRU may select a grant that best suits the WTRU's coverage and / or measured path loss. For example, in some implementations, the WTRU may select a grant with a TBS above a TBS threshold for preamble group B if the measured path loss is below a configured threshold (e.g., a path loss threshold associated with the selected preamble group B), and / or discard the grant otherwise.

[0120] In some implementations, among multiple signaled grants associated with one or more monitored RA-RNTIs, the WTRU may select a grant with more available symbols or slots for uplink transmission, such that the WTRU has more opportunities for repeated transmission in the selected grant.

[0121] Some implementations may include in Msg2 an indication of the Tx beam / RO to use in Msg3 206. In some implementations, the WTRU may be configured with RAR reception times associated with one or more SSBs. For example, in some implementations, the WTRU may monitor for Msg2 associated with a particular SSB indication portion of a msg1 202 repetition bundle, in a particular subset of slots, within a particular offset / window from the SSB transmission time, and / or within a particular offset / window from the RO occasion time used to indicate the associated SSB. In some implementations, the WTRU may select the RAR corresponding to the strongest measured SSB (e.g., highest power reception level) after receiving multiple Msg2s or RARs, possibly after the expiration of the RAR window. In some implementations, selecting the RAR corresponding to the strongest measured SSB may facilitate the gNB implicitly refining the strongest beam pair. In some implementations, the WTRU may select the spatial filter used for transmitting msg3 206 according to the RAR and / or SSB associated with the beam pair.

[0122] Among multiple signaled grants associated with one or more monitored RA-RNTIs, in some implementations, the WTRU may select a grant according to the strongest measured SSB (e.g., in some implementations, only among the SSBs indicated in the msg1 202 repetition bundle). For example, in some implementations, the WTRU may select the grant signaled in the RAR associated with the strongest measured SSB (e.g., when several RARs are associated with one or more SSBs). Among multiple signaled grants associated with one or more monitored RA-RNTIs, in some implementations, the WTRU may select a grant according to the strongest spatial filter. For example, in some implementations, the WTRU may implicitly (e.g., from properties of the scheduling information) or explicitly (e.g., from an indication in the DCI or the contents of the RAR). In some implementations, the WTRU may select a grant associated with the strongest measured SSB from multiple grants and / or may discard one or more other grants.

[0123] In some implementations, the gNB (or other receiver (e.g., a gNB may be used throughout)) may explicitly or implicitly signal the strongest Tx beam / RO in Msg2 to use in Msg3 206. In some implementations, the RAR may indicate the RO or one or more Tx beams to use to decode the preamble, and in some implementations the WTRU may use this preamble to transmit Msg3 206. In some implementations, the RAR may indicate whether the WTRU will use one or more of the indicated beams for the msg3 206 repetition, or sweep through one or more configured or indicated beams. In some implementations, the gNB may implicitly signal the strongest tx beam / RO in Msg2 for use in Msg3 206 based on, for example, the random access preamble identity (RAPID) indicated in the RAR (e.g., if different preamble indices are used), the RA-RNTI (e.g., if different msg1 202 repetitions are on different RNTI Ro), and / or the timing of the RAR reception (e.g., the slot used to receive the RAR, the time offset between Msg1 202 and Msg2, or the associated SSB).

[0124] In some implementations, the WTRU may determine the strongest tx beam / RO in Msg2 to use explicitly or implicitly in Msg3 206. The RAR may indicate the RO or Tx beam used to decode the preamble, and the WTRU may use this preamble to transmit Msg3 206. The RAR may indicate whether the WTRU should use the indicated beam for the msg3 206 repetition or sweep through one or more configured or indicated spatial filters. The WTRU may determine the strongest tx beam / RO in Msg2 to use implicitly in Msg3 206 based on, for example, the RAPID indicated in the RAR (e.g., if different preamble indices are used), the RA-RNTI (e.g., if different msg1 202 repetitions are on different RNTI Ro), and / or the timing of the RAR reception (e.g., the slot used to receive the RAR, the time offset between Msg1 202 and Msg2, or the associated SSB). The WTRU may also determine the strongest tx beam from a field in the DCI indicating the RAR or a field in the random access grant carried in the RAR.

[0125] Some implementations may include RAR combinations (e.g., monitoring multiple RARs). For example, some implementations may include an RAR monitoring window. In some implementations, the WTRU may start the RAR monitoring window after transmission of the first repetition, possibly if the repetition is not transmitted over a PRACH resource separately configured by the gNB for the msg1 202 repetition. In some implementations, the WTRU may start or restart the RAR window after transmission of each msg1 202 repetition. Additionally or alternatively, in some implementations, the WTRU may start the RAR window some time after (e.g., only after) transmission of the last repetition. Additionally or alternatively, in some implementations, the WTRU may start the RAR window after the last repetition using the same beam. Additionally or alternatively, in some implementations, the WTRU may start the RAR window after the last repetition using the same msg1 202 repetition bundle.

[0126] In some implementations, the WTRU may stop the RAR window (and / or PDCCH monitoring) after successfully receiving any RAR. Additionally or alternatively, in some implementations, the WTRU may stop the RAR window after receiving a predefined or configured number of RARs. In some implementations, the number of RARs to monitor may be dynamically determined based on the number of indicated SSBs (e.g., the number of preambles transmitted on Ro mapped to different SSBs).

[0127] Some implementations may include Msg2 coverage enhancement. For example, in some implementations, the WTRU may soft-combine RAR / Msg2, e.g., for received RARs scrambled with one or more RA-RNTIs used to transmit one or more Msg1 202. In some implementations, soft-combining may be an error correction technique in which bad packets are not discarded but stored in a buffer. For example, two or more packets received with insufficient information may be combined together in a way that the entire signal can be decoded. In some implementations, the WTRU may receive multiple repetitions of the PDCCH signaling Msg2 and / or PDSCH repetitions for the Msg2 payload. In some implementations, the gNB may mirror the diversity represented by the WTRU in msg1 202 (e.g., so that the WTRU may receive RARs for SSBs associated with the Ro on which msg1 202 was repeated). In some implementations, multiple DL beams corresponding to the swept indicated UL Tx beam may be used for RAR diversity.

[0128] Some implementations may concern the impact of Msg1 202 repetition on the RA procedure. Some such implementations may include RA procedure initiation. For example, in some implementations, the WTRU may initiate the RA procedure using msg1 202 repetition if the measured DL RSRP (or channel conditions) is below a configured threshold (e.g., the threshold is configured for msg3 206 repetition). In some implementations, the WTRU may first compare the measured RSRP to a configured threshold for the supplemental uplink carrier (SUL) versus the normal uplink carrier (normal uplink, NUL) (e.g., first perform carrier selection), and then compare each measured RSRP to the threshold for msg1 202 or msg3 206 repetition. In some implementations, after initiating an RA with msg1 202 repetition, the WTRU may select a PRACH resource associated with and / or configured for the msg1 202 repetition, the WTRU may select multiple times (e.g., uniquely) from a preamble configured for group A, and / or the WTRU may ignore the selection criteria for preamble group A / B and select multiple times (e.g., uniquely) any preamble portion of group A or B.

[0129] In some implementations, the WTRU may initiate a PRACH repetition procedure using a single preamble without repetitions, but may switch to multi-msg1 202 repetitions if, for example, the number of retransmissions (or preamble transmission counter) exceeds a configured or predefined threshold. In some implementations, the WTRU may initiate a PRACH repetition procedure using preamble repetitions, but may switch to sub-PRB PRACH preamble transmissions if the number of retransmissions (or preamble transmission counter) exceeds a configured or predefined threshold.

[0130] Some implementations may include power ramping. For example, in some implementations, the WTRU may power ramp after the RAR window expires. Additionally or alternatively, in some implementations, the WTRU may power ramp after a retransmission of the same beam, whereby in some implementations, the WTRU sweeps one or more (e.g., all) Tx beams before power ramping. Additionally or alternatively, in some implementations, the WTRU is configured with one or more Tx beams (e.g., spatial filters) to sweep before power ramping. In some implementations, the WTRU may not be allowed to change beams until the WTRU has finished power ramping (or a configured number of repetitions) using the same beam.

[0131] Some implementations may include a PRACH beam set. For example, in some implementations, the WTRU may perform PRACH repetitions within a configured or indicated set of beams. Such a set of beams may be referred to hereinafter as a PRACH beam set. The set of beams may be indicated based on one or more of the following: a subset of the cell's SSBs, a set of RSs such as CSI-RS or SRS (e.g., indicated using CRI or SRI), and / or a set of TCI states, e.g., indicated using a TCI state identity or from an index to indicate one of the possible subsets of TCI states.

[0132] In some implementations where a set of beams is indicated as a set of CSI-RS, SRS, or TCI states, the WTRU may determine an association between each such CSI-RS, SRS, or TCI state and an SSB or PRACH occasion for the purpose of selecting an appropriate PRACH occasion. In some implementations, the WTRU may explicitly obtain the association between the PRACH beam set and the SSB or PRACH occasion from RRC, MAC CE, or DCI. For example, in some implementations, the WTRU may receive a PDCCH command for the RACH indicating such a PRACH beam set. In some embodiments, the WTRU may receive a MAC CE indicating a subset of the TCI states for the PRACH beam set.

[0133] In some implementations, the WTRU may derive the PRACH beam set implicitly from another configuration. For example, in some implementations, the PRACH beam set may implicitly correspond to a set of TCI states used for PDCCH or PDSCH reception. In some embodiments, the PRACH beam set may implicitly correspond to a set of periodic and / or aperiodic SRS resources configured for the WTRU. In some implementations, the PRACH beam set may correspond to a set of beams configured as candidate RSs as part of a beam failure recovery configuration.

[0134] Some implementations may include determining a beam repetition mode and a PRACH beam set. The following example implementations facilitate a WTRU to determine a PRACH beam repetition mode. In some implementations, the PRACH beam repetition mode may determine whether the WTRU performs PRACH repetitions. In some implementations, the PRACH beam repetition mode may determine whether the WTRU performs PRACH repetitions using a single beam or two or more beams. In some implementations, the PRACH beam repetition mode may determine the number of beams for PRACH repetitions or the maximum number of beams. In some implementations, the PRACH beam repetition mode may determine whether the WTRU selects at least one beam for PRACH repetitions from any SSB or from an indicated or configured set of beams, such as a PRACH beam set. In some implementations, the PRACH beam repetition mode may determine the identity of one or more beams for PRACH repetitions, such as a PRACH beam set.

[0135] In some implementations, the WTRU may determine the PRACH beam repetition mode and / or PRACH beam set based on which event triggers the initiation of a random access procedure, which may include one or more of a system information (SI) request, beam failure recovery, reconfiguration (handover) with synchronization, initial access, connection re-establishment, DL or UL data arrival, SR failure, transition from RRC_INACTIVE state, establishing time alignment for secondary TAG, consistent UL LBT (listen before talk) failure, and / or a PDCCH command.

[0136] In some implementations, the WTRU may determine the PRACH beam repetition mode as a function of the random access type, such as whether the WTRU performs a four-step random access procedure (Type A) or a two-step random access procedure (Type B), or whether the random access is contention-free or contention-based.

[0137] In some implementations, the WTRU may determine the PRACH beam repetition mode based on explicit signaling. For example, in some implementations, a PRACH configuration information element may indicate the PRACH beam repetition mode. In some implementations, the WTRU may receive a MAC CE indicating the PRACH beam repetition mode. In some implementations, the WTRU may receive the PRACH beam repetition mode from a PDCCH command for the RACH.

[0138] In some implementations, the WTRU may determine a PRACH beam repetition mode based on one or more measurements, such as RSRP, path loss, or RSRQ, from one or more RSs. In some implementations, the WTRU may determine a first PRACH repetition mode (e.g., no repetition mode) if one or more measurements are above a threshold, and / or may determine a second PRACH repetition mode (e.g., a PRACH repetition mode with N repetitions) if one or more (e.g., all) measurements are below a threshold. In some implementations, the one or more RSs may correspond to RSs configured or indicated as a PRACH beam set. In some implementations, the threshold may be configured or indicated by RRC or MAC.

[0139] Some implementations may include incrementing a preamble Tx counter or otherwise tracking one or more preamble Txs. For example, for an RA procedure initiated with a msg1 202 repetition, in some implementations, the WTRU may increment the preamble Tx counter (or otherwise adjust tracking of the number of preamble Txs) in one or more of the following ways: some time after (e.g., only after) the expiration of the RAR window for msg1 202 retransmissions, after each repetition / preamble transmission, after transmission of a complete repeated bundle if one bundle can be configured or predefined, and / or after transmission of a configured or predefined number of preamble copies.

[0140] In implementations where a counter or other tracking is incremented or otherwise adjusted after transmission of a complete repetition bundle, e.g., where one bundle may be configured or predefined, the bundle may include a sweep of the configured number of beams / ROs, or one or more repetitions using the same beam. In implementations where a counter or other tracking is incremented or otherwise adjusted after transmission of a configured or predefined number of preamble copies, the WTRU may increment the counter (or adjust the tracking) every three repetitions, where x is configured, predefined, or in broadcast signaling.

[0141] Some implementations may include a new counter or other tracking to control the number of msg repetitions. For example, in some implementations, the WTRU may maintain an additional new "msg1 repetition counter" (or other tracking variable or mechanism, etc.) on top of the preamble transmission counter to maintain the number of repetitions. In some implementations, the WTRU may increment the counter (or increment or adjust another tracking mechanism) after transmitting each msg1 202 repetition. In some implementations, the WTRU may reset the counter (or other tracking mechanism) based on receiving an RAR or backoff, or based on starting a new repetition bundle, or upon expiration of the RAR window (preamble retransmission). In some implementations, the WTRU may not increment the counter (or may not increment or adjust another tracking mechanism) for skipped transmissions of preamble repetitions, for example, due to an LBT failure or a canceled UL slot (e.g., due to receiving inter-WTRU cancellation signaling, or due to intra-WTRU prioritization for another uplink signal via the PRACH).

[0142] In some implementations, the WTRU may be predefined or configured by broadcast or dedicated signaling with a parameter (e.g., Msg1maxRep) that indicates the amount (e.g., maximum number) of msg1 202 repetitions per bundle (e.g., before the RAR window expires), one or more repetitions per beam, the amount (e.g., maximum) number of repetitions per preamble index, and / or one or more repetitions before power ramping. In some implementations, the WTRU may terminate sending msg1 202 transmissions after transmitting Msg1maxRep, for example, if the msg1 202 repetition counter (or other tracking) is greater than or equal to Msg1maxRep. In some implementations, the WTRU may reset the msg1 202 transmission counter (or other tracking) if the repetition and / or transmission counter is greater than or equal to Msg1maxRep.

[0143] Some implementations may include a backoff indication. For example, in some implementations, the WTRU may be configured with separate or different backoff values ​​that the WTRU may use when an RA procedure involving msg1 202 repetition is initiated. For an RA procedure initiated with msg1 202 repetition, in some implementations the WTRU may receive an instruction to modify the number of repetitions per bundle (or, more generally, Msg1maxRep), which may be signaled as part of the content of msg2 (e.g., as part of the backoff indication). In some implementations, the WTRU may receive an enhanced backoff indication (BI) with instructions to backoff or remove a particular Tx beam (or spatial filter) from the next preamble retransmission bundle and / or to modify the configured set of beams that the WTRU sweeps over a portion of the msg1 202 repetition bundle. In some implementations, the WTRU may be signaled the modified number of repetitions per bundle in the enhanced BI, after receiving which the WTRU performs preamble retransmissions with the modified number of repetitions per bundle. In some implementations, the WTRU may receive an indication in the contents of msg2 or in the BI, after receiving which the WTRU may early terminate transmission of the remaining repetitions in the msg1 202 repetition bundle.

[0144] In some implementations, the WTRU may receive an enhanced BI indicating a switch to the SUL for preamble retransmission, after which the WTRU may abort the ongoing RA procedure and initiate a new RA procedure on the SUL carrier. In some implementations, the WTRU may receive an enhanced BI indicating a switch to sub-PRB PRACH preamble retransmission.

[0145] The WTRU may receive a backoff indication indicating a particular TRP on which to retransmit the preamble and / or retransmit the preamble on a PRACH resource associated with the indicated PRACH resource. The WTRU may receive a backoff indication for one or more of the repetitions it sent and backoff msg1 202 retransmissions for the entire bundle.

[0146] Some implementations may include parameters used for Msg1 202. For example, some implementations may include parameters for the target received preamble power (P0).

[0147] In some implementations, the WTRU may use the same P0 for one or more (e.g., all) repetitions in a msg1 202 repetition bundle, possibly when the same Tx beam is used. In some implementations, the WTRU may use a different (e.g., configured by RRC) P0 (e.g., a value configured separately from any other normal RA procedure, such as one initiated without msg1 202 repetitions) when an RA procedure with msg1 / 3 repetitions is used. In some implementations, the WTRU may adjust P0 based on a measured path loss based on a selected spatial filter or a measured path loss associated with an SSB to which the RO is mapped (e.g., taking into account the selected DL and UL beams). In some implementations, the WTRU may adjust P0 based on a selected Tx beam and / or a selected Rx beam (SSB).

[0148] Some implementations may include a power ramping step parameter (e.g., POWER RAMPING STEP). For example, in some implementations, when an RA procedure with msg 1 / 3 repetition is used, the WTRU may use a different POWER RAMPING STEP (e.g., configured by RRC). In some implementations, the WTRU may adjust the POWER RAMPING STEP based on the measured path loss based on the selected spatial filter or the measured path loss associated with the SSB to which the RO is mapped (e.g., taking into account the selected DL and UL beams). In some implementations, the WTRU may adjust the POWER RAMPING STEP based on the selected Tx beam and / or the selected Rx beam (SSB).

[0149] Some implementations may include other coverage aspects. For example, some implementations may include SUL aspects. In some implementations, the WTRU may be configured with separate RSRP thresholds for the purpose of selecting PRACH resources configured for msg1 202 repetitions on the SUL carrier. In some implementations, Msg1 202 repetitions and / or PRACH resources may be configured separately for the NUL and / or SUL, including the number of repetitions at which Msg1 202 is repeated and / or related parameters such as the number of repetitions, Msg1RepMax, candidate Tx beams to consider for beam sweeping, etc.

[0150] In some implementations, the WTRU may initiate an RA procedure with PRACH repetitions on the NUL carrier (e.g., if the measured RSRP is greater than the SUL-rsrp threshold) and then switch to SUL after one or more preamble transmissions with ≦preambleTransMax.

[0151] Some implementations may include BFR+Msg1 202 repetitions. For example, in some implementations, the WTRU may transmit a beam failure recovery request (BFRQ) (msg1 202) using the same CFRA preamble (e.g., corresponding to the strongest measured CSI-RS) for a configured number of repetitions before the expiration of the RAR window, which may possibly be the same number of repetitions configured for contention-based RA if msg1 202 repetitions are configured and / or a separate configuration is configured. In some implementations, the WTRU may end the repetitions after the WTRU receives a response from the network, e.g., a PDCCH addressed to the WTRU's C-RNTI.

[0152] The WTRU may transmit a BFRQ (msg1 202) using M different CFRA preambles (corresponding to the N strongest measured CSI-RS), where M≧N. The WTRU may transmit a repeated BFRQ (msg1 202) using a combination of CFRA and CBRA preambles, possibly if the BFR timer expires.

[0153] Some implementations may include frequency hopping and / or PRACH selection for Msg1 202 repetition. For example, in some implementations, PRACH resource hopping may be used and / or configured to address interference and / or fading due to frequency selectivity. In some implementations, the WTRU may be predefined or configured to repeat one or more copies of Msg1 202 on different Ros in the frequency domain. In some implementations, such configuration may be received over broadcast or dedicated signaling. In some implementations, the WTRU may be predefined or configured with a frequency hopping pattern. For example, in some implementations, the WTRU may select consecutive Ros in time for repetition while frequency hopping (e.g., randomly) among Ros of the same f_id used for RA-RNTI compression. Additionally or alternatively, in some implementations, the WTRU may hop between Ros of different f_ids.

[0154] The BWP embodiment may be used herein.

[0155] The WTRU may be configured with PRACH resources for msg1 202 repetition on a subset of the bandwidth portion within the carrier on which RA is performed. The configuration of whether msg1 202 repetition is performed may be configured per uplink bwp or per PRACH resource configuration.

[0156] If the criteria for msg1 202 repetition are met and / or if there is an insufficient amount of resources available for msg1 202 repetition in the active BWP (e.g., none at all), the WTRU may switch to another BWP configured with resources for msg1 202 repetition. For example, if the measured channel quality is below a threshold and the current active UL BWP does not support resources for msg1 202 repetition, the WTRU may switch to another UL BWP (e.g., a default or initial BWP) configured with resources for msg1 202 repetition.

[0157] The WTRU may be instructed to switch to another BWP for the (re)transmission of Msg3 206 or the (re)transmission of msg1 202, whereby such an instruction may be signaled as part of the RAR and / or backoff instruction content, or may be indicated by the DCI for msg2 or msgB. In an embodiment, the WTRU may infer the BWP for transmitting msg3 206 from the content of the uplink grant signaled in the RAR and / or the properties of the DCI instruction scheduling msg2. The WTRU may perform msg3 206 repetition if the WTRU is signaled to switch to another BWP for which msg3 206 repetition is configured, e.g., possibly if the procedure started with msg1 202 repetition (e.g., if a PRACH was selected for msg1 202 and / or msg3 206 repetition).

[0158] In an embodiment, the WTRU may determine whether to perform msg1 202 and / or msg3 206 repetitions before selecting an uplink carrier (e.g., SUL vs. NUL), e.g., before evaluating the RSRP criteria for UL carrier selection. The WTRU may be configured with a separate RSRP threshold for NUL vs. SUL selection if the msg1 202 and / or msg3 206 repetition criteria is met (e.g., if the channel is measured below the configured threshold for repetition). Conversely, the WTRU may determine whether to perform msg1 202 and / or msg3 206 repetitions after selecting an uplink carrier (e.g., SUL vs. NUL). In an embodiment, the WTRU may not switch to another BWP after transmitting a preamble on a given BWP. Local transmit beam sweeping with Msg1 202 repetitions initiating for determining and configuring a local beam sweep set may be used herein.

[0159] The WTRU may be configured with a "local beam set" for the purposes of selecting a DL beam, a corresponding UL beam, sweeping the uplink transmit beam, repeating the transmission of msg1 202 preamble, and / or selecting associated RACH resources. The WTRU may be configured with (or determine) a local beam set size, which is the number of SSBs and / or uplink beams for which the WTRU repeats msg1 202. For example, the WTRU may select the strongest SSB and / or strongest CSI-RS according to the strongest measured channel quality (e.g., RSRP or SINR). Additionally or alternatively, the WTRU may select one or more secondary (or adjacent) SSB and / or CSI-RS resources. The secondary SSBs or CSI-RS may be selected consecutively from the index of the strongest SSB or strongest CSI-RS.

[0160] The WTRU may repeat the msg1 202 transmission one or more times less than or equal to the size of the selected local beam set. The WTRU may repeat the msg1 202 transmission one or more times less than or equal to the size of the selected local beam set multiplied by the number of configured msg1 202 repetitions per UL and / or DL ​​beam. In an embodiment, the secondary SSB or CSI-RS may be selected based on the order (e.g., descending) of the channel measurements.

[0161] In an embodiment, the WTRU may be configured to perform a "repeat and sweep" in which the WTRU repeats the msg1 202 transmission for each beam in the selected local beam set. The WTRU may decide to repeat and sweep if the RSRP corresponding to the SSB for which the WTRU decides to perform beam sweeping is below a configured threshold.

[0162] A WTRU may be configured with multiple local beam sets via broadcast or dedicated signaling. The WTRU may be configured with an association between each local beam set and one or more PRACH resources and / or initiating ROs. The associated PRACH resources may be contiguous or spread in the time and / or frequency domains. The WTRU may use the PRACH resources associated with a selected local beam set to sweep the tx / rx beams, possibly after a specific RO defined for the set and / or within a subset of ROs defined by an RO mask for the set. The WTRU may indicate the selected local beam set by transmitting msg1 202 on the associated PRACH resources, whereby msg1 202 may be repeated using different UL beams corresponding to selected / measured DL beams (SSB or CSI-RS) that are part of the selected local beam set. The WTRU may first select a DL beam (SSB or CSI-RS) and then select the local beam set associated with the DL beam. Additionally or alternatively, the WTRU may select the local beam set having the strongest total or average channel measurement associated with the beams in the local beam set.

[0163] The WTRU may select or determine a local beam set for CFRA with msg1 202 repetition. The local beam set for CFRA may be pre-configured per CFRA resource, indicated by RRC signaling, or indicated by DCI or a PDCCH command. For example, the WTRU may receive a PDCCH command indicating a local set to use for CFRA preamble repetition, starting RO, msg1 202 repetition bundle size, and / or associated size of the local beam set size. The WTRU may repeat CFRA preamble transmission / repetition on the CFRA PRACH resource associated with the indicated local beam set or on the indicated RO associated with the local beam set. In an embodiment, the WTRU may receive a PDCCH command indicating a local set to use for a given TRP. The WTRU may receive a PDCCH command indicating a particular TRP within the serving cell or a physical cell ID associated with the TRP on which the WTRU may repeat msg1 202. The WTRU may repeat the CFRA preamble transmission and / or repetition on the CFRA PRACH resources associated with the indicated TRP and / or local beam set.

[0164] Local transmit beam sweeping with Msg1 202 iterations for the local beam set size may be used herein.

[0165] For each local beam set, the WTRU may determine an associated beam set size, whereby the beam set size defines the number of SSBs, number of transmit beams, number of beam pairs, and / or number of msg1 202 repetitions involved in transmitting msg1 202 via the selected local beam set. The WTRU may receive a beam set size configuration for each local beam set or for one or more (e.g., all) configured local beam sets; such configuration may be provided by broadcast or dedicated signaling. Alternatively, the WTRU may determine the size itself, as described herein. From the configured size for the selected local beam set size "M," the WTRU may further dynamically down-select "N" beam pairs, possibly based on channel measurements (e.g., according to the methods described in the next section), where M and N are configured.

[0166] In embodiments, a WTRU may operate in one of two WTRU operating modes, with or without beam tx beam sweeping, possibly depending on the WTRU's capabilities, configuration, and / or measured channel conditions. The network may configure the WTRU with one of two operating modes, potentially configured per cell, per PRACH resource, per BWP, or per TRP, by broadcast or dedicated signaling. The WTRU may decide to operate without beam sweeping (e.g., using a different tx beam, using PRACH resources for legacy WTRUs, or using a local beam set size of 1, and no msg1 202 repetitions) if the WTRU determines that beam correspondence is met. In some embodiments, if the WTRU determines that beam correspondence is met, the WTRU may not select an RO associated with beam sweeping (e.g., a PRACH resource configured with a local beam set size greater than 1). In an embodiment, the WTRU may determine that beam correspondence is satisfied if one or more (e.g., multiple or all) beam pairs in the local beam set satisfy channel measurements and / or are successfully received.

[0167] A WTRU may select a PRACH resource associated with msg1 202 repetition and / or a local beam set of size > 1 to indicate that the WTRU may be beam sweepable (e.g., a PRACH resource configured with msg1 202 repetition using different tx beams, or a resource configured with a local beam set size greater than 1). Conversely, a WTRU that is not configured with or is not capable of msg1 202 repetition and / or a WTRU that is not configured with or is not capable of msg1 202 repetition using different tx beams cannot select a PRACH resource associated with a local beam set size greater than 1.

[0168] The WTRU may be configured to gradually increase the local beam set size (and / or select a different local beam set, e.g., having a larger size than the previous attempt) after one or N configured preamble retransmissions. If no RAR is received after a transmission attempt of msg1 202, the WTRU may consider the preamble a retransmission. For example, the WTRU may start with an initial local beam set size and then increase the set size after expiration of the RAR window for retransmitting msg1 202, after receiving an LBT failure indication from the lower layer, or after a configured number of retransmissions. In an embodiment, the configured number of retransmissions may depend on channel measurements. For example, msg1 202 repetitions may be performed based on channel conditions being below a configured threshold. The number of retransmissions may depend on the channel conditions (e.g., if the channel conditions are below a first threshold, the first number of repetitions may be performed, and if the channel conditions are below a second threshold, the second number of retransmissions may be performed). In this way, worse channel conditions can be used to trigger a larger number of iterations.

[0169] In an embodiment, the WTRU may start with one or more of the initial number of repetitions of msg1 202 transmission. If the LBT fails, the WTRU may increase the receive bundle size for msg1 202 retransmissions by a configured or specified delta number, up to some amount (e.g., a maximum number) of configured repetitions per bundle. The WTRU may continue to use the same UL beam until the LBT is successful for one or more repetition attempt transmissions. In an embodiment, the WTRU may select a local beam set and / or msg1 202 repetition bundle size based on measured RSSI or channel occupancy, or based on the number of past LBT failed attempts for previous msg1 202 retransmissions.

[0170] Figure 3A shows an example of a wide-range SSB. Figure 3A shows three TX beams swept by a gNB, with SSB1 302, SSB2 304, and SSB3 306 swept over a wider range. Figure 3B 301 shows an example of a narrow-range SSB. In a narrow-range SSB (e.g., a local beam set), SSB2-1 303, SSB2-2 305, and SSB2-3 307 may be swept within a narrower range, with "SSB2" being equivalent to SSB2-2. A WTRU may be configured with a narrow range for each SSB within the wide range. For example, the WTRU may receive a configuration NB=3 and [-15, 15] degrees, which indicates that for each SSB in wide range mode, there is an NB SSB beam (e.g., SSB2-1 303, SSB2-2 305, and SSB2-3 307 in FIG. 3B) that can sweep from -15 degrees to 15 degrees at equally spaced beam angles relative to the central SSB.

[0171] Assume there are three Ros, each corresponding to an SSB within the wide-area SSB of 301 in Figure 3A, where Roi corresponds to an SSBi (e.g., RO1 is associated with SSB1). If the WTRU observes an RSRP above a threshold for one of the SSBs, the WTRU may transmit a preamble on the associated RO (e.g., RO2 at t=T 402 if SSB2 is the strongest measured SSB).

[0172] In an embodiment, the WTRU may use the same Ro to indicate the preference of the WTRU for narrowband SSBs. The WTRU may use the PRACH resources associated with the selected SSB to sweep the transmission beam associated with the same selected (e.g., wider) SSB.

[0173] The WTRU may be composed of two types of preambles and / or Ro, where the first type can be used to indicate wideband SSBs and one or more are for indicating narrowband SSBs. The WTRU may receive from the network an indication that the network performs both wideband and narrowband SSB transmissions. For example, as shown in FIGS. 3A and 3B, if the RSRP measured for SSB2 exceeds a threshold, the WTRU may transmit preamble 1 (e.g., the first type of preamble) with RO2 at t = T 402. Note that the relationship between time and RO is shown in FIG. 4. Thereafter, preamble 1 is transmitted. If the RSRP of SSB2-1 exceeds the threshold, the WTRU may transmit preamble 1-1 (e.g., the second type of preamble) with RO1 at t = T' 404 (e.g., T < T') to indicate that the WTRU receives SSB2-1 at a good RSRP level. In an embodiment, the preamble and / or RO for indicating a narrower beam may be configured with a different preamble and / or RO index than that for a wider beam.

[0174] By performing sequential preamble transmissions, the WTRU can indicate its preferred beam in both wide and / or narrow ranges using the same set of Ro by using different preambles. The WTRU can be configured with a first type and / or a second type preamble, such that the first type preamble is used as a request for narrow-range SSB transmission by the gNB. For example, as shown in FIG. 5, after the WTRU transmits preamble 1 502, the WTRU may determine that the gNB will perform local beam sweeping in a narrower range around SSB2. The WTRU may transmit preamble 1-1 504 in association with the local beam sweeping in a narrower range around SSB2 (e.g., SSB2-1 303, SSB2-2 305, SSB2-3 307).

[0175] With respect to determining the local beam set based on channel measurements / selected SSB, local transmit beam sweeping using Msg1 202 iterations may be used herein.

[0176] From multiple configured local beam sets, the WTRU may select a beam set based on measured channel conditions, including, for example, L3 RSRP, L1 RSRP, SINR, channel occupancy, RSSI, and / or SS-RSRP. For a selected local beam set, the WTRU may determine the beam set size, the number of associated SSBs, the number of transmit beams used for msg1 202 repetitions, and / or the number of msg1 202 repetitions from the measured channel conditions and / or from measurements performed on beams (SSB or CSI-RS) associated with the selected local beam set. For example, for a certain RSRP range, the WTRU may be configured or pre-specified to select a configured or predetermined number of SSBs, beam pairs, and / or msg1 202 repetitions. For a higher RSRP range, the WTRU may select a smaller number of SSBs, beam pairs, and / or msg1 202 repetitions.

[0177] One or more SSBs may provide increased coverage over other SSBs, potentially providing coverage (e.g., uniform coverage) across a cell in one or more (e.g., different) directions. In some cases (e.g., small cell boresight or beams), a WTRU may not require msg1 202 repetitions. The WTRU may be configured with the number of msg1 202 repetitions and / or the number of repetitions per selected SSB according to the selected SSB and / or local beam set. The WTRU may be configured with one or more (e.g., several) msg1 202 repetitions and / or one or more (e.g., several) beam pairs as a function of the measured channel quality. For example, below a certain channel condition measurement threshold, the WTRU may sweep using a different number of msg1 202 repetitions and / or one or more beam pairs. The WTRU may determine the quality of the channel condition from measurements (e.g., RSRP or SINR) associated with the selected SSB for the msg1 202 repetition bundle.

[0178] Regarding the termination of beam sweep / msg1 202 repetition in a selected local beam set, local transmit beam sweep with Msg1 202 repetition may be used herein.

[0179] In an embodiment, a WTRU may be configured to perform a local RX or TX beam sweep during a time window having a configured duration (e.g., indicated by the number of ROs, slots, symbols, milliseconds). The WTRU may receive the start and / or end of the time window for the RO or ROs associated with the SSBs for which the WTRU will perform TX / RX beam sweeping. The duration of the time window may be shorter than the number of repetitions (e.g., the size of the selected local beam set) for which the WTRU is configured to repeat msg1 202 transmissions. If the WTRU is configured with both the time window and the number of repetitions, the WTRU may decide to prioritize the configuration related to the time window and / or terminate the msg1 202 repetitions at the end of the time window. In an embodiment, the WTRU may be configured with a timer duration during which the WTRU performs msg1 202 repetitions for RX or TX beam sweeping. The WTRU may start the timer when the WTRU initiates RX or TX beam sweeping and may terminate the sweeping operation when the time expires (e.g., the timer reaches a configured time limit). The WTRU may stop the timer or end the window if the WTRU has successfully completed the LBT for the transmission of one or more msg1 202 repetitions associated with at least one SSB.

[0180] The association between RAR reception time and SSB may be used herein.

[0181] The WTRU may monitor the PDCCH for reception of Msg2 on one or more "RAR reception occasions," where an occasion may be a slot, subslot, or RAR reception time window. The WTRU may be configured with an association between a local beam set and an RAR reception occasion. The WTRU may be configured with an association between PRACH resources and an RAR reception occasion. The WTRU may be configured with an association between an RA-RNTI range and an RAR reception occasion. Upon selection of a local beam set and associated PRACH resources for transmitting msg1 202 repetitions for the selected local beam set, the WTRU may monitor the RAR occasion associated with the msg1 202 transmit RACH occasion. The association between the SSB and the RAR reception occasion and / or the association between the tx beam and the RAR reception occasion may be configured by broadcast or dedicated signaling.

[0182] The WTRU may infer the strongest DL beam (e.g., SSB) from the timing or index of the RAR reception of the RAR occasion in which the RAR was successfully received (e.g., for the RA-RNTI corresponding to the transmitted msg1 202 repetition). The WTRU may assume that the selected SSB is the SSB associated with the RAR occasion in which the RAR was received, for example, for the remainder of the RA procedure (during subsequent msg2 and msg4 receptions until the procedure is successful).

[0183] In an embodiment, the WTRU may be configured with a "representative SSB or beam" for each local beam set, for each set of RAR reception occasions associated with the local beam set, or for each set of PRACH resources associated with the local beam set. The WTRU may assume that the selected SSB is a representative SSB associated with one of the RAR occasions on which an RAR was received, and may use that SSB for the remainder of the RA procedure.

[0184] Repetition within a single RO may be used herein.

[0185] The WTRU may change the UL / DL beam pair selected for transmission of msg1 202 within a single RO. For example, the WTRU may repeat the PRACH sequence within the configured PRACH format using different transmit beams and / or using different preambles associated with different selected DL beams. The WTRU may be configured with one or more repetitions per transmit beam before switching to a different beam. With such a configuration, the WTRU may repeat the sequence for the configured number of repetitions per beam before switching to a different uplink beam. The WTRU may be configured with an association between sequence timing and one or more SSBs or CSI-RS. The WTRU may indicate the selected SSB from the timing of the transmitted sequence within the RO. If the UL and / or DL ​​beam is changed during a msg1 202 repetition bundle, the WTRU may insert (or configure) a guard period between the ROs.

[0186] For an RO configured to be associated with a particular SSB, the WTRU may indicate which sub-beam (e.g., a narrower beam as shown in Figures 3A and 3B) forms the selection of sequence transmission times within the RO.

[0187] The dependency on the PRACH format may be used herein.

[0188] A WTRU may be configured by broadcast (e.g., SI) or RRC signaling with one or more valid PRACH formats per cell, per TRP, and / or per physical cell ID. The WTRU may be configured with a channel quality threshold (e.g., RSRP or RS-SINR threshold) used to evaluate which PRACH format to use. The WTRU may be configured with an association between a PRACH format and a PRACH resource. For each PRACH resource, the WTRU may be configured with the applicable PRACH format, one or more Msg1 202 repetitions, one or more SSBs, associated SSBs, and / or one or more Ros per slot to use for msg1 202 repetitions.

[0189] The WTRU may be configured with a channel measurement range association for each configured PRACH format and / or for each configured RACH resource. The WTRU may select a PRACH resource and / or format according to the measured channel quality. The WTRU may repeat msg1 202 on one or more ROs, e.g., as a combination of repeating the same PRACH sequence within the same RO and / or using multiple ROs for a selected PRACH resource. If the UL and / or DL ​​beams are changed during a msg1 202 repetition bundle, the WTRU may insert (or configure) guard periods between ROs.

[0190] The WTRU may be configured with a PRACH format and / or resource to SSB association. The WTRU may select a PRACH resource for a particular PRACH format if the WTRU is associated with the selected / strongest measured SSB.

[0191] The WTRU may be configured to perform Msg1 202 iterations using multiple panels.

[0192] For a particular WTRU form factor or frequency range, the antenna sphere coverage requirements may be based on two or more panels. The WTRU may use one or more panels for reception and / or possible transmission. Additionally or alternatively, the WTRU beamforming capabilities may be less prolific than gNB beams in terms of granularity and / or beamwidth, and beam alignment from the WTRU's perspective may be less obvious.

[0193] Since the WTRU measures several beams while sweeping the SSB, there may be several options for Msg1 202 repetition based on the measurement results that may be linked to different WTRU panels for initial access.

[0194] Potential issues when using multiple panels for Msg1 202 repetition may be the repetition itself (e.g., more than one panel at the same time), the power allocation along the panels that may measure different SSB and path losses, and the Msg1 202 sequence used, as well as the RACH occasion (RO). Some (e.g., all) of these factors may have importance in the subsequent selection of a receive panel for Msg2.

[0195] The gNB may configure PRACH resources or formats, for example, based on the WTRU capabilities. The WTRU may be configured with an association between the WTRU reporting panel number and PRACH resources. Multi-panel capability reporting may be understood, for example, as spherical coverage based on multiple panels. When this panel-based PRACH partitioning is performed, the WTRU may use the allocated resources for PRACH repetitions on a particular panel.

[0196] When the WTRU measures different SSBs on different panels, the WTRU may be allowed to repeat Msg1 on one or more different panels in a time-multiplexed manner, meaning using RO1 for one panel and RO2 for another. The WTRU may be configured with an association between the panel and the RO and / or preamble index by broadcast or dedicated signaling. The WTRU may select a local beam set for beam sifting such that the beam set includes the SSB associated with the panel on which overwhip msg1 202 may be repeated in the time domain.

[0197] By using two or more different Ro, the reception of Msg2 may be staggered such that the WTRU may receive Msg2 on two or more different RAR reception occasions at two or more different times.

[0198] In an embodiment, one or more Ros may use different RACH sequences. To resolve possible Msg1 202 confusion in the gNB, the association of PRACH sequences with each Ro may be bundled so that the base station knows that it can bundle different ROs and / or PRACH resources of sub-sequences based on the RO and / or PRACH sequence.

[0199] A WTRU configured to utilize a TDM method may be used herein. The TDM method may cycle through the RO and RACH resources associated with the power ramp-up until the WTRU receives a valid Msg2. For example, the TDM method may be associated with a two-panel configuration. Upon receiving a valid Msg2 on a panel, the WTRU may abandon the two-panel repetition and continue the RA procedure using the successful panel (e.g., for transmitting Msg3 206 and receiving Msg4). The two panels may serve a set of three SSBs, and therefore, cycling may be performed for the three SSBs across the two panels by cycling through the RO and RACH resources, resulting in the same Msg2 reception and / or continuation rules.

[0200] In an embodiment, a WTRU may perform simultaneous UL panel transmissions for RACH on different panels within the same RO. PRACH resources may be different and / or associated with different SSBs. For example, a given RO may be configured to be associated with different SSBs from the same TRP or different TRPs within a cell. Simultaneous transmissions may need to consider maximum TRP (total radiated power) requirements. Therefore, the applicability of simultaneous transmissions may be linked to a specific coverage level, where WTRU power ramping on both transmission panels may not be a restriction on Msg1 202 repetition. The network may signal the coverage level via a PRACH-configured RSRP level threshold. Additionally or alternatively, the network may signal separate conditions for simultaneous panel transmissions of Msg1 202 as a maximum RSRP delta between candidate beams. Both conditions may be required for simultaneous PRACH transmissions of Msg1 202 to apply.

[0201] When a WTRU performs Msg1 202 iterations and ramps up power after each failed attempt (e.g., no Msg2 reception), power may be ramped up on both panels for each iteration. Because the WTRU may see different path losses on different beams, one panel may reach maximum power faster than the other. In this case, to resolve the issue when output power is limited by the WTRU max TRP, some embodiments may scale down the power-limited Tx beam so other beams can also transmit. The WTRU may apply different power ramping steps to different panels, for example, depending on the measured path loss and / or power headroom. Additionally or alternatively, some embodiments may drop the power-limited panel transmission and / or potentially perform one or more of the other beam transmissions. Some embodiments may fall back to a single-beam iteration solution after one or more failed Msg1 202 attempts using simultaneous panel transmissions.

[0202] When using two-panel simultaneous PRACH transmission, the WTRU may monitor for Msg2 reception from the gNB according to the RO timeline. Because the resources for the PRACH may be different and / or per SSB, the WTRU may consider the received correct Msg2 as the end of the retransmission / repetition procedure for Msg1 202, and / or the WTRU may continue with the remainder of the RA procedure (e.g., to transmit Msg3 206 or receive Msg4) on the gNB-selected beam for Msg2.

[0203] 6 shows an example of a WTRU performing RACH using message repetition. For example, at 602, the WTRU may receive one or more SSBs (e.g., SSB1, SSB2, SSB3, etc.). The first measured / selected SSB (e.g., SSB1, SSB2, SSB3, etc.) may be a relatively wide area beam (e.g., meant to provide greater signal coverage). The WTRU may select one of the SSBs, e.g., SSB2. The selection may be based on measurements. For example, SSB2 may be the strongest SSB among SSB1, SSB2, SSB3, etc. that is first detected by the WTRU. In one example, the WTRU may receive one or more configurations (e.g., via SIB, dedicated RRC signaling, etc.) associating each SSB with a local beam set.

[0204] For example, at 604, the WTRU may determine that SSB2 is associated with local beam set 2. In one embodiment, local beam set 2 may be associated with other SSBs, such as SSB2-1, SSB2-2, SSB2-3, and SSB2-4. The beams in the local beam set may be relatively narrower than the initially selected SSB (e.g., SSB2). For example, the beams in the local beam set may be configured to provide narrower coverage within the coverage area of ​​the initially measured beam. In other words, SSB2-1, SSB2-2, SSB2-3, SSB2-4, etc. in the local beam set for SSB2 may transmit in the same general area as SSB2, but may provide stronger signal strength in portions of the area based on narrower beamforming. In this embodiment, the local beam set is represented using RSs corresponding to SSBs (e.g., SSB2-1, SSB2-2, SSB2-3, SSB2-4), but the local beam set may also be defined using other reference signals (e.g., CSI-RS).

[0205] In an embodiment, at 606, the WTRU may measure a local beam set for the selected SSB and select a subset of SSBs associated with the local beam set. In some embodiments, the WTRU may sweep Msg1 on tx beams and / or ROs associated with a selected subset of the local beam subsets. For example, at 608, the WTRU may determine that the subset of local beams to use corresponds to SSB2-1, SSB2-2, and SSB2-3. The WTRU may transmit Msg1 on random access resources corresponding to the selected beams. For example, RO2-1, RO2-2, and RO2-3 may be random access resources (e.g., ROs) corresponding to the selected beams SSB2-1, SSB2-2, and SSB2-3, respectively.

[0206] The WTRU may monitor the RAR with the RA-RNTI for Msg1 transmitted at 608. At 610, the WTRU may receive RAR1 and RAR2. For example, RAR1 may correspond to the RAR for Msg1 transmitted on RO2-1, and RAR2 may correspond to the RAR for Msg1 transmitted on RO-2-2. As shown in FIG. 6, an RAR may be received for less than a certain amount (e.g., all) of the transmitted Msg1.

[0207] At 612, the WTRU may transmit Msg3 based on the received RARs. For example, the WTRU may transmit Msg3 using Grant 1 received in RAR1 and may transmit a repetition of Msg3 using Grant 2 received in RAR2. Msg3 may be transmitted using different spatial filters. For example, Msg3 transmitted using Grant 1 from RAR1 may be transmitted using a spatial filter associated with one or more of SSB2-1, RO2-1, a corresponding beam in the local beam set, etc. Msg3 transmitted using Grant 2 from RAR2 may be transmitted using a spatial filter associated with one or more of SSB2-2, RO2-2, a corresponding beam in the local beam set, etc.

[0208] While features and / or elements may be in specific combinations, those skilled in the art will understand that each feature or element may be used alone or in any combination with the other features and / or elements. Additionally or alternatively, the methods used herein may be implemented in a computer program, software, or firmware embodied in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (e.g., transmitted over a wired or wireless connection) and / or computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random-access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, a WTRU, a terminal, a base station, an RNC, or any host computer.

Claims

1. 1. A wireless transmit / receive unit (WTRU) comprising a processor, the processor comprising: selecting a first SSB based on the measurements; receiving configuration information indicating a set of reference signals (RSs) associated with the first SSB and a respective set of random access channel (RACH) occasions (ROs) for each RS in the set; determining a subset of the set of RSs associated with the first SSB; transmitting a first preamble on a first RO associated with a first RS in the determined subset and a second preamble on a second RO associated with a second RS in the determined subset; receiving a first Random Access Response (RAR) including a first grant and a second RAR including a second grant, the first RAR being associated with the first RO and the second RAR being associated with the second RO; and transmitting a message using the first grant and transmitting a repetition of the message using the second grant, wherein the transmission of the message using the first grant uses a spatial filter associated with the first RO and the transmission of the repetition of the message using the second grant uses a spatial filter associated with the second RO.

2. 2. The WTRU of claim 1, wherein the configuration information indicates a respective set of RSs and an associated set of ROs for each of a plurality of SSBs, the plurality of SSBs including at least the first SSB selected by the WTRU.

3. The WTRU of claim 1 , wherein the configuration information comprises one or more SSBs or one or more channel state information reference signals (CSI-RS).

4. The WTRU of claim 1 , wherein the subset of the set of RSs is determined based on measurements associated with the first SSB.

5. 2. The WTRU of claim 1, wherein the first SSB is associated with a wide beam set, and the subset of the set of RSs corresponds to a local beam set determined by the WTRU, and the local beam set is narrower than the wide beam set associated with the first SSB.

6. 6. The WTRU of claim 5, wherein the first SSB is associated with a first transmission beam, the first RS and the second RS are each associated with a respective beam of the local beam set, and the local beam set is determined based on the wide beam set associated with the first SSB.

7. The WTRU of claim 1 , wherein the processor being configured to transmit the message comprises the processor being configured to transmit a RACH message.

8. The WTRU of claim 7 , wherein the processor being configured to transmit the repetitions of the message comprises the processor being configured to transmit the repetitions of the RACH message.

9. 2. The WTRU of claim 1, wherein the processor is further configured to transmit a second iteration of the message using a third grant, the transmission using the third grant using a spatial filter associated with a third RO.

10. 2. The WTRU of claim 1, wherein the processor is further configured to receive an indication from a network, the indication indicating that the WTRU should refrain from using preamble repetition for a subsequent RACH procedure, and the processor is further configured to switch to single-preamble retransmission on condition that the processor receives the indication from the network.

11. 1. A method comprising: selecting a first SSB based on the measurements; receiving configuration information indicating a set of reference signals (RSs) associated with the first SSB and a respective set of random access channel (RACH) occasions (ROs) for each RS in the set; determining a subset of the set of RSs associated with the first SSB; transmitting a first preamble on a first RO associated with a first RS in the determined subset and a second preamble on a second RO associated with a second RS in the determined subset; receiving a first Random Access Response (RAR) including a first grant and a second RAR including a second grant, the first RAR being associated with the first RO and the second RAR being associated with the second RO; transmitting a message using the first grant and transmitting a repetition of the message using the second grant, wherein the transmission of the message using the first grant uses a spatial filter associated with the first RO and the transmission of the repetition of the message using the second grant uses a spatial filter associated with the second RO.

12. 12. The method of claim 11, wherein the configuration information indicates a respective set of RSs and an associated set of ROs for each of a plurality of SSBs, the plurality of SSBs including at least the first SSB selected by a WTRU.

13. The method of claim 11 , wherein the configuration information includes one or more SSBs or one or more channel state information reference signals (CSI-RS).

14. The method of claim 11 , wherein a first subset of the set of RSs is determined based on measurements associated with the first SSB.

15. 12. The method of claim 11, wherein the first SSB is associated with a wide beam set, and the subset of the set of RSs corresponds to a local beam set determined by the WTRU, the local beam set being narrower than the wide beam set associated with the first SSB.

16. 16. The method of claim 15, wherein the first SSB is associated with a first transmission beam, the first RS and the second RS are each associated with a respective beam of the local beam set, and the local beam set is determined based on the wide beam set associated with the first SSB.

17. The method of claim 11 , wherein transmitting the message comprises transmitting a RACH message.

18. 18. The method of claim 17, wherein transmitting the repetition of the message comprises transmitting the repetition of the RACH message.

19. 12. The method of claim 11, further comprising transmitting a second iteration of the message using a third grant, the transmission using the third grant using a spatial filter associated with a third RO.

20. 12. The method of claim 11, further comprising receiving an indication from a network, the indication indicating that the WTRU should refrain from using preamble repetition for subsequent RACH procedures, and the method further comprising switching to single-preamble retransmission on the condition that the indication is received from the network.

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