WO2019195476A1

WO2019195476A1 - Prach structure in nr unlicensed

Info

Publication number: WO2019195476A1
Application number: PCT/US2019/025662
Authority: WO
Inventors: Erdem Bala; Kyle Jung-Lin Pan; Alphan Sahin; Rui Yang; Ahmad Reza HEDAYAT
Original assignee: Idac Holdings, Inc.
Priority date: 2018-04-04
Filing date: 2019-04-03
Publication date: 2019-10-10
Also published as: TW202005455A

Abstract

A wireless transmit/receive unit (WTRU) performing PRACH may adjust a PRACH format based on a different numerology of a channel that the WTRU attempts to access. The PRACH format may be characterized by an upsampling ratio and a sequence length. The WTRU may determine numerology of a channel that the WTRU attempts to access including a subcarrier spacing of the channel. The WTRU may determine a PRACH format based on the determined numerology. The sequence length may be fixed, and the upsampling ratio may vary based on the subcarrier spacing. The upsampling ratio may indicate a set of subcarriers used for a PRACH sequence within a PRACH bandwidth. The WTRU may perform random access using the determined PRACH format.

Description

PRACH STRUCTURE IN NR UNLICENSED

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application Nos. 62/652,647 filed April 04, 2018 and 62/669,091 filed May 9, 2018, the contents of which are incorporated by reference.

BACKGROUND

[0002] Mobile communications using wireless communication continue to evolve. A fifth generation may be referred to as 5G. A previous (legacy) generation of mobile communication may be, for example, fourth generation (4G) long term evolution (LTE).

SUMMARY

[0003] Implementations {e.g., systems, methods, and/or devices) for physical random access channel (PRACH) structure may be disclosed herein. The implementations may be implemented in 3GPP, e.g., in NR. Implementations may include phase aligning parts of a PRACH sequence. Implementations may include Golay construction for a PRACH sequence. Physical uplink share channel (PUSCH) puncturing for adjacent channel interference mitigation may be performed. A common back-off counter for multiple wireless transmit/receive units (WTRUs) may be implemented. Implementations may include interleaved PRACH within a (e.g., one) cluster. Listen before talk (LBT) may be performed in narrowband PRACH.

[0004] A wireless transmit/receive unit (WTRU) performing PRACH may adjust a format of PRACH (e.g., a PRACH format) based on a numerology of a channel that the WTRU attempts to access. The PRACH format may be characterized by an upsampling ratio and a sequence length. The WTRU may determine a numerology of a channel that the WTRU attempts to access. The numerology of the channel may include a subcarrier spacing of the channel. The WTRU may determine a PRACH format based on the determined numerology. The sequence length may be fixed, and the upsampling ratio may vary based on the subcarrier spacing. For example, if a physical random access channel has a first subcarrier spacing, a first upsampling ratio may be used. If the physical random access channel has a second subcarrier spacing that is less than the first subcarrier spacing, a second upsampling ratio that is greater than first upsampling ratio may be used to keep the sequence length at a fixed value. The upsampling ratio may be used to map a PRACH sequence to a set of subcarriers within a PRACH bandwidth. For example, the PRACH sequence may be mapped to a set of contiguous subcarriers if the upsampling ratio is one, and the PRACH sequence may be mapped to alternate subcarriers if the upsampling ratio is two. The WTRU may perform random access using the determined PRACH format.

[0005] A WTRU performing PRACH may adjust a PRACH format based whether a prior attempt to access the channel was successful. The WTRU may determine the success of the prior attempt based on a received indication. A first PRACH format comprising a first upsampling ratio may be used in the prior attempt to access the channel. If the prior attempt was unsuccessful, the WTRU may determine a second PRACH format comprising a second upsampling ratio that is different from the first upsampling ratio and perform random access using the second PRACH format.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Furthermore, like reference numerals in the figures indicate like elements, and wherein:

[0007] FIG. 1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented;

[0008] FIG. 1 B is a system diagram illustrating an example wireless transmit/receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1 A according to an embodiment;

[0009] FIG. 1C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communications system illustrated in FIG. 1 A according to an embodiment;

[0010] FIG. 1 D is a system diagram illustrating a further example RAN and a further example CN that may be used within the communications system illustrated in FIG. 1 A according to an embodiment;

[0011] FIG. 2 shows an example of an interlace.

[0012] FIG. 3 shows an example of a PRACH preamble structure.

[0013] FIG. 4 shows an example of a PRACH resource allocation with block interleave division multiple access (B-IDMA).

[0014] FIG. 5 shows an example of a PRACH sequence mapping.

[0015] FIG. 6 shows an example of a PRACH preamble orthogonal frequency division multiplexing

(OFDM) signal generation. [0016] FIG. 7A shows examples of different numerologies for PRACFI and physical uplink share channel (PUSCH).

[0017] FIG. 7B shows an example of a PRACFI sequence mapping.

[0018] FIG. 7C shows an example of a PRACFI transmission.

[0019] FIG. 7D shows an example of a PRACFI time domain signal.

[0020] FIG. 8 shows an example of puncturing PUSCFI.

[0021] FIG. 9 shows an example of a PRACFI OFDM signal generation using Golay sequences.

[0022] FIG. 10 shows an example of LBT in PRACFI preamble transmission.

[0023] FIG. 11 shows an example of multiple WTRUs performing LBT and PRACFI preamble transmission(s), e.g., in a PTW.

DETAILED DESCRIPTION

[0024] FIG. 1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0025] As shown in FIG. 1A, the communications system 100 may include wireless transmit/receive units (WTRUs) 102a, 102b, 102c, 102d, a RAN 104/113, a ON 106/1 15, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and/or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and/or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a "station” and/or a "STA”, may be configured to transmit and/or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, 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 (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications {e.g., remote surgery), an industrial device and applications {e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c and 102d may be interchangeably referred to as a UE.

[0026] The communications systems 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 communication networks, such as the CN 106/115, the Internet 110, and/or the 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, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller, an access point (AP), a wireless router, and the like. While 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.

[0027] The base station 114a may be part of the RAN 104/113, 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 the base station 114b may be configured to transmit and/or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for a wireless service to a specific geographical area that may be relatively fixed or that may change over time. The cell may further be 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 for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and/or receive signals in desired spatial directions.

[0028] 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).

[0029] 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 CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104/113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 1 15/1 16/1 17 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and/or High-Speed UL Packet Access (HSUPA).

[0030] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/or LTE-Advanced Pro (LTE-A Pro).

[0031] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR Radio Access , which may establish the air interface 1 16 using New Radio (NR).

[0032] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for instance using dual connectivity (DC) principles. Thus, the air interface utilized by WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and/or transmissions sent to/from multiple types of base stations {e.g., a eNB and a gNB).

[0033] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0034] The base station 114b in FIG. 1 A may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a roadway, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. 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 be required to access the Internet 110 via the CN 106/115.

[0035] The RAN 104/113 may be in communication with the CN 106/115, which may be any type of network configured to provide voice, data, applications, and/or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106/115 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and/or perform high-level security functions, such as user authentication. Although not shown in FIG. 1A, it will be appreciated that the RAN 104/113 and/or the CN 106/115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104/113 or a different RAT. For example, in addition to being connected to the RAN 104/113, which may be utilizing a NR radio technology, the CN 106/115 may also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0036] The CN 106/115 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and/or the other networks 112. The PSTN 108 may include circuit- switched telephone networks that provide 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), user datagram protocol (UDP) and/or the internet protocol (IP) in the TCP/IP internet protocol suite. The networks 112 may include wired and/or wireless communications networks owned and/or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104/113 or a different RAT.

[0037] 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. 1 A may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0038] FIG. 1 B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1 B, the WTRU 102 may include 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, among others. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0039] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input/output processing, and/or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit/receive element 122. While FIG. 1 B depicts the processor 118 and the transceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0040] The transmit/receive element 122 may be configured to transmit signals to, or receive signals from, a base station {e.g., the 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 an 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 appreciated that the transmit/receive element 122 may be configured to transmit and/or receive any combination of wireless signals.

[0041] Although the transmit/receive element 122 is depicted in FIG. 1 B 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.

[0042] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit/receive element 122 and to demodulate the signals that are received by the transmit/receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11 , for example.

[0043] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker/microphone 124, the keypad 126, and/or the display /touch pad 128 (e.g., a liquid crystal display (LCD) display unit or 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. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and/or the 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, and the like. 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 a home computer (not shown).

[0044] The processor 118 may receive power from the power source 134, and may be configured to distribute and/or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries {e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0045] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102.

In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station (e.g., base stations 114a, 114b) and/or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by way of any suitable location- determination method while remaining consistent with an embodiment.

[0046] 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 e-compass, a satellite transceiver, a digital camera (for photographs and/or video), 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, and the like. The peripherals 138 may include one or more sensors, the sensors may be one or more of a gyroscope, an accelerometer, a hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor; an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and/or a humidity sensor.

[0047] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the UL (e.g., for transmission) and downlink (e.g., for reception) may be concurrent and/or simultaneous. The full duplex radio may include an interference management unit to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor 1 18). In an embodiment, the WRTU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the downlink (e.g., for reception)).

[0048] FIG. 1 C is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 1 16. The RAN 104 may also be in communication with the CN 106.

[0049] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 1 16. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and/or receive wireless signals from, the WTRU 102a.

[0050] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and/or DL, and the like. As shown in FIG. 1 C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0051] The CN 106 shown in FIG. 1 C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and/or operated by an entity other than the CN operator.

[0052] 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 serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation/deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. 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.

[0053] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the 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 user planes during inter- eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0054] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0055] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may 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 the other networks 112, which may include other wired and/or wireless networks that are owned and/or operated by other service providers.

[0056] Although the WTRU is described in FIGS. 1 A-1 D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (e.g., temporarily or permanently) wired communication interfaces with the communication network.

[0057] In representative embodiments, the other network 112 may be a WLAN.

[0058] A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have an access or an interface to a Distribution System (DS) or another type of wired/wireless network that carries traffic in to and/or out of the BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. The traffic between STAs within a BSS may be considered and/or referred to as peer-to- peer traffic. The peer-to-peer traffic may be sent between (e.g., directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11e DLS or an 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an "ad- hoc” mode of communication.

[0059] When using the 802.11 ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling. The primary channel may be the operating channel of the BSS and may be used by the STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) may be implemented, for example in in 802.11 systems. For CSMA/CA, the STAs (e.g., every STA), including the AP, may sense the primary channel. If the primary channel is sensed/detected and/or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0060] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0061] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately. The streams may be mapped on to the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0062] Sub 1 GHz modes of operation are supported by 802.11 af and 802.11 ah. The channel operating bandwidths, and carriers, are reduced in 802.11 af and 802.11 ah relative to those used in 802.11 h, and 802.11 ac. 802.11 af supports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11 ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non- TVWS spectrum. According to a representative embodiment, 802.11 ah may support Meter Type

Control/Machine-Type Communications, such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, for example, limited capabilities including support for (e.g., only support for) certain and/or limited bandwidths. The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0063] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802.11h, 802.11 ac, 802.11 af, and 802.11 ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and/or limited by a STA, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode.

In the example of 802.1 1 ah, the primary channel may be 1 MHz wide for STAs {e.g., MTC type devices) that support (e.g., only support) a 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) settings may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which supports only a 1 MHz operating mode), transmitting to the AP, the entire available frequency bands may be considered busy even though a majority of the frequency bands remains idle and may be available.

[0064] In the United States, the available frequency bands, which may be used by 802.11 ah, are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11 ah is 6 MHz to 26 MHz depending on the country code.

[0065] FIG. 1 D is a system diagram illustrating the RAN 113 and the CN 1 15 according to an embodiment. As noted above, the RAN 113 may employ an NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the CN 115.

[0066] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 1 13 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and/or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to, and/or receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and/or gNB 180c).

[0067] The WTRUs 102a, 102b, 102c may communicate with 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 gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing varying number of OFDM symbols and/or lasting varying lengths of absolute time).

[0068] 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 the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without also accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with/connect to gNBs 180a, 180b, 180c while also communicating with/connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, 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 the non-standalone configuration, eNode-Bs 160a, 160b, 160c may serve as a mobility anchor for WTRUs 102a, 102b, 102c and gNBs 180a, 180b, 180c may provide additional coverage and/or throughput for servicing WTRUs 102a, 102b, 102c.

[0069] 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 of network slicing, dual connectivity, interworking between NR and E- UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG. 1 D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0070] The CN 1 15 shown in FIG. 1 D 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 each of the foregoing elements are depicted as part of the CN 1 15, it will be appreciated that any of these elements may be owned and/or operated by an entity other than the CN operator.

[0071] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 1 13 via an N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different PDU sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of NAS signaling, mobility management, and the like. Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types of services being utilized 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 machine type communication (MTC) access, and/or the like. The AM F 162 may provide a control plane function for switching between the RAN 1 13 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and/or non-3GPP access technologies such as WiFi.

[0072] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 115 via an N1 1 interface. The SMF 183a, 183b may also be connected to a UPF 184a, 184b in the CN 115 via an N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP address, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notifications, and the like. A PDU session type may be IP-based, non-IP based, Ethernet- based, and the like.

[0073] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet- switched networks, such as the Internet 1 10, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, and the like.

[0074] The CN 115 may facilitate communications with other networks. For example, the CN 1 15 may include, or may communicate with, an IP gateway {e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 1 15 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to the other networks 1 12, which may include other wired and/or wireless networks that are owned and/or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local Data Network (DN) 185a, 185b through the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0075] In view of Figures 1A-1 D, and the corresponding description of Figures 1A-1 D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 1 14a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b,

DN 185a-b, and/or any other device(s) described herein, may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more, or all, of the functions described herein. For example, the emulation devices may be used to test other devices and/or to simulate network and/or WTRU functions. [0076] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and/or in an operator network environment. For example, the one or more emulation devices may perform the one or more, or all, functions while being fully or partially implemented and/or deployed as part of a wired and/or wireless communication network in order to test other devices within the communication network. The one or more emulation devices may perform the one or more, or all, functions while being temporarily implemented/deployed as part of a wired and/or wireless communication network. The emulation device may be directly coupled to another device for purposes of testing and/or may performing testing using over-the-air wireless communications.

[0077] The one or more emulation devices may perform the one or more, including all, functions while not being implemented/deployed as part of a wired and/or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and/or a non-deployed (e.g., testing) wired and/or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and/or wireless communications via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation devices to transmit and/or receive data.

[0078] LTE Licensed Assisted Access (LAA) and enhanced LAA (eLAA) may be implemented. Licensed Assisted Access (LAA) may be used as part of LTE Advanced Pro. eLAA implementations may enable uplink and downlink operation of LTE in unlicensed bands.

[0079] Listen before talk (LBT) may be performed.

[0080] LBT protocol may be implemented in LAA. Categories associated with LBT may include one or more of the following: no LBT; LBT without random back-off; LBT with random back-off with a contention window of fixed size; and LBT with random back-off with a contention window of variable size.

[0081] For the case of no LBT, a transmitting entity may not perform a LBT procedure.

[0082] For the case of LBT without random back-off, the duration of time when the channel is sensed to be idle before the transmitting entity transmits may be deterministic.

[0083] For the case of LBT with random back-off with a contention window of a fixed size, LBT may include one of more of the following. The transmitting entity may draw a random number N within a contention window. The size of the contention window may be specified, for example, by the minimum and maximum value of N. The size of the contention window may be fixed. The random number N may be used in the LBT, e.g., to determine the duration of time when the channel may be sensed to be idle before the transmitting entity transmits on the channel.

[0084] For the case of LBT with random back-off with a contention window of variable size(s), LBT may include one or more of the following. The transmitting entity may draw a random number N within a contention window. The size of the contention window may be specified, for example, by the minimum and maximum value of N. The transmitting entity may vary the size of the contention window, e.g., when drawing the random number N. The random number N may be used in the LBT, e.g., to determine the duration of time when the channel may be sensed to be idle before the transmitting entity transmits on the channel.

[0085] Interlaced resource allocation (e.g., Block (B)-IDMA) may be performed.

[0086] The resource allocation framework in the eLAA system may be implemented. For example, the basic unit of resource allocation for unlicensed data channels may be an interlace. An interlace may include ten equally spaced resource blocks (RBs) within a 20 MHz frequency bandwidth. An interlaced structure in frequency may be used, e.g., due to the regulatory requirements (e.g., occupied bandwidth and 10 dBm/MHz requirement) in unlicensed band. WTRUs may exploit the maximum available transmit power. FIG. 2 shows an example interlace. For example, as shown in FIG. 2, an interlace may include 120 subcarriers of an OFDM symbol. The subcarriers may be distributed in a clustered manner. Cluster sizes (e.g., each cluster size) may be 12, and the clusters may be separated from each other by 9x12 subcarriers.

[0087] Interlaced resource allocation may apply to data channel (e.g., only to data channel). The control channel (e.g., PUCCH) and random access channel (RACH) may be transmitted using a licensed band.

[0088] Random access channel (e.g., as may be illustrated by a physical random access channel) may be used to perform random access.

[0089] A WTRU that attempts to access the network may transmit a random access preamble in the physical random access channel (PRACH), e.g., in NR.

[0090] Sequence may be generated.

[0091] The set of random-access preambles X_{u v} ( 71 ) may be generated according to Eq. 1 and Eq.

2, e.g., in NR.

from which the frequency-domain representation may be generated according to Eq. 3,

where L_RA = 839 or L_RA = 139 depending on the PRACH preamble format (e.g., as given by Table 1 and Table 2). The sequence number U may be obtained from the logical root sequence index, and C_v may be the cyclic shift.

Table 1 PRACH preamble formats for

Table 2 Preamble formats for

[0092] The preamble sequence may be mapped to physical resources according to Eq. 4

where /¾>RACH may be an amplitude scaling factor. The amplitude scaling factor / ACH ^maY be used to conform to a certain transmit power. P = 4000 _may be the antenna port. An OFDM signal may be generated. The PRACH preamble may include a cyclic prefix, repetition of the OFDM symbol, and a guard interval. The duration of the cyclic prefix, guard interval, OFDM symbol, and the number of repetitions may depend on, e.g., the PRACFI preamble format. FIG. 3 shows an example of a PRACFI preamble structure.

[0093] An allocation of frequency resources may be non-contiguous, e.g., when the resource allocation used for PRACFI is B-IDMA. Techniques that improves coverage relative to coverage associated with a contiguous resource allocation and/or reduce the peak-to-average power ratio (PAPR) of a PRACFI preamble may be provided herein.

[0094] Physical uplink shared channel (PUSCH) and PRACFI may interfere with each other due to adjacent channel interference, e.g., when PUSCH and PRACFI use different OFDM numerology {e.g., different subcarrier spacing). Techniques that mitigate the interference between PUSCH and PRACFI may be provided.

[0095] A WTRU may refrain from accessing and/or transmitting in an upcoming PRACFI resource if a LBT procedure fails. This may be due to LBT requirements and/or add to an initial access delay. A gNB may have some delays in scheduling PRACFI resources as often and/or on a periodic basis (e.g., due to unsuccessful LBT at gNB).

[0096] PRACFI sequence(s) may be generated using blocked-interleaved frequency division multiple access (B-IFDMA).

[0097] Zadoff-Chu sequences (e.g., as in NR) may be used to generate a PRACFI preamble. A selected Zadoff-Chu sequence may be transmitted, e.g., using a B-IFDMA approach. For example, a sequence (e.g., Zadoff-Chu sequence) may be partitioned into L parts. L may correspond to the number of chunks in an interlace. A chunk may include (e.g., be defined as) a set of contiguous set of subcarriers. An interlace may include L chunks. Some (e.g., all) of the L chunks may not be adjacent in the frequency domain. In examples, a chunk and a resource block including multiple consecutive subcarriers may be used interchangeably. A resource block may include 12 subcarriers. Parts (e.g., blocks) of the sequence may be mapped to chunks (e.g., resource blocks) of an interlace that is allocated for random access preamble transmission. For example, each part (e.g., each block) of the sequence may be mapped to one chunk {e.g., one resource block) of an interlace allocated for random access preamble transmission.

[0098] FIG. 4 shows an example of PRACFI resource allocation with B-IDMA. As shown in FIG. 4, a sequence may be divided into L parts, and each part of the L parts may be mapped to one resource block of an interlace.

[0099] One resource block (e.g., In NR) may include 12 subcarriers. The size of an interlace (e.g., the interlace as shown in FIG. 4) may be 12L subcarriers. For example, if L = 12, then an allocation size may be 144 subcarriers. If L = 10, then the allocation size may be 120 subcarriers. The allocation size may include, for example, the number of subcarriers allocated to a PRACFI sequence.

[0100] The length of (e.g., the number of subcarriers used for) the sequence may not be equal to the number of available subcarriers. For example, the length of the sequence used may be less than 120 (e.g., 113), less than 144 (e.g., 139), etc. To map the sequence to the available resources (e.g., subcarriers), one or more of the following may be used.

[0101] In examples, a sequence may be divided into parts such that the first L-1 parts may have 12 elements (e.g., coefficients), and the last part may have N - (12 * (L-1)) coefficients, where N may be the sequence length. For example, if L = 10 and N is 113, then the last part may have 5 coefficients. M zeros may be mapped to resources of a resource block that are not used by a sequence (e.g., no coefficients of a sequence are mapped to those resources). In this example, the number of zeros mapped to the last resource block of the interlace may be 12 - 5 = 7. As another example, if L = 12 and N is 139, then the last part may have 7 coefficients. The number of zeros mapped to the last resource block of the interlace may be 12 - 7 = 5.

[0102] In examples, M zeros may be mapped to the last resource block of an interlace or shared between the first resource block and the last resource block of the interlace. The M zeros may be mapped to the last M subcarriers of the last resource block of an interlace. The M zeros may be shared between the first k subcarriers of the first resource block of an interlace and the last n subcarriers of the last resource block of the interlace, where M = k + n. FIG. 5 shows an example of PRACFI sequence mapping. In FIG.

5, it is assumed that N = 113 and L = 10. The first sequence part that may be mapped to the first RB may have 8 coefficients and the last sequence part that may be mapped to the last RB may have 9 coefficients. The remaining sequence parts may be mapped to the remaining 8 RBs, each of which is used to map 12 coefficients of the sequence (e.g., PRACFI sequence).

[0103] A (e.g., each) sequence part of a PRACFI sequence may be multiplied with a phase factor, e.g., before generating the OFDM signal from the PRACFI sequence. Multiplication of the sequence part with a phase factor may reduce the PAPR of the OFDM signal generated from the PRACFI sequence. The phase factors may be selected from a set (e.g., a small set) and/or may be saved in a table for sequences (e.g., each sequence). As an example, the phase factor(s) may be selected from {1 , -1 , i,— i }, or { 1 + i, 1—

[0104] FIG. 6 shows an example of PRACH preamble OFDM signal generation. As shown in FIG. 6, a Discrete Fourier Transform (DFT) block may be used to transform a PRACFI sequence into frequency domain. The DFT block may be skipped for certain sequences, e.g., Zadoff-Chu sequences. The DFT- spread sequence may be divided into L parts, for example, part 1 to part L. A (e.g., each) part may be multiplied with a phase factor, e.g., phase factor 1 to phase factor L. Phase factor 1 to phase factor L may be the same. Some (e.g., all) of phase factors 1 to L may be different. A sequence part (e.g., each sequence part) may be mapped to one resource block of an interlace. An OFDM signal may be generated using Inverse Discrete Fourier Transform (IDFT). The phase factor(s) for a sequence(s) (e.g., each sequence) may be computed off-line and/or saved in a table.

[0105] Examples herein may similarly be applied to other types of sequences, for example sequences derived from Zadoff-Chu sequences. The size of a chunk may or may not be 12 subcarriers. A chunk may include any number of subcarriers, e.g., depending on the specific design.

[0106] One or more examples described herein may be applied when the subcarrier spacing of the PRACFI preamble is different from the subcarrier spacing of PUSCPI. FIG. 7A shows examples of different numerologies for PRACFI and physical uplink share channel (PUSCPI). Three sample cases where PRACFI and PUSCPI resource blocks have different numerologies (e.g., subcarrier spacings, bandwidths etc.) are illustrated in FIG. 7A. For example, PRACFI and PUSCPI resource blocks may have different bandwidths when PRACFI and PUSCPI resource blocks have the same number of subcarriers, and the subcarrier spacing is different for PRACFI and PUSCPI. The size of the PUSCPI RB may be taken as a reference to determine the PRACFI chunk size.

[0107] In FIG. 7A(a), a PUSCPI RB may be of size 12 x 30 kPHz = 360 kHz, and the PRACFI RB may be of size 12 x 15 kHz = 180 kHz. A PRACFI RB (e.g., each PRACFI RB) may belong to a different interlace. For example, each RB may be used (e.g., defined) as one "chunk” of an interlace.

[0108] In FIG. 7A(b), a PUSCPI RB may be of size 12 x 15 kHz = 180 kHz, and the PRACFI RB may be of size 12 x 30 kHz = 360 kHz. The PRACFI RB may belong to one interlace, e.g., the PRACFI RB may be used (e.g., defined) as one "chunk” of an interlace.

[0109] In FIG. 7A(c), a PUSCPI RB may be of size 12 x 15 kHz = 180 kHz, and the PRACFI RB may be of size 12 x 1 .25 kHz = 15 kHz. Multiple PRACFI RBs (e.g., 12 PF ACH RBs) may constitute one "chunk” of an interlace. [0110] Narrowband PRACH sequence may be generated. A PRACH preamble (e.g., including a PRACH sequence) or a PRACH sequence may be generated in a portion of a channel. The PRACH sequence may be contiguous or interlaced within the portion of the channel, e.g., as described herein.

[0111] In examples, a PRACH sequence may be transmitted in at least one portion of a channel bandwidth (e.g., a cluster 720 as shown in FIG. 7B). FIG. 7B shows an example of a PRACH sequence mapping. Although one or more examples described herein may assume one portion/cluster, the one or more examples may be applicable to more than one portions/clusters. A PRACH sequence may be derived from a Zadoff-Chu sequence or another type of sequence (e.g., Golay sequences).

[0112] As shown in FIG. 7B(a) and FIG. 7B(b), some subcarriers in the frequency domain may be utilized for PRACH (e.g., a PRACH sequence). The subcarriers in the frequency domain may be allocated for PRACH. A PRACH sequence may be mapped to the subcarriers (e.g., the allocated subcarriers), for example to one or more of the subcarriers allocated for PRACH. The subcarriers used for the PRACH sequence may be contiguous (e.g., as shown in FIG. 7B (a)) or interlaced (e.g., as shown in FIG. 7B(b)). A PRACH sequence may be processed (e.g., pre-processed), e.g., before being mapped to the allocated subcarriers. One example of the pre-processing may be taking a DFT transform of a sequence (e.g., the PRACH sequence).

[0113] One or more implementations may be used to map a PRACH sequence to resources (e.g., subcarriers). A PRACH sequence may be mapped to a set of contiguous subcarriers (e.g., as shown in FIG. 7B(a)). The channel BW (e.g., available channel BW) may be * Af Hz, where K may be the number of subcarriers (e.g., available subcarriers). Af may be the subcarrier spacing (e.g., for the available subcarriers). For example, may be 1024 and Af may be 60 kHz, resulting in a channel bandwidth (e.g., an available channel bandwidth) of 61.440 MHz. The available channel bandwidth may include PRACH bandwidth. The bandwidth allocated for use by the PRACH sequence (e.g., PRACH bandwidth) may be Lx Af Hz, e.g., excluding any guard bands that may be inserted around the subcarriers used for the PRACH sequence. L may be the sequence length of the PRACH sequence. The sequence length may be a number of resources (e.g., subcarriers) that is allocated and/or mapped to the PRACH sequence. For example, sequence length L may be 139 (e.g. shown as shaded in FIG. 7B(a)), and Af may be 60 kHz, resulting in a PRACH bandwidth of 8.340 MHz.

[0114] FIG. 7B illustrates one or more of the following. A PRACH sequence may be mapped to a set of interlaced subcarriers. The PRACH sequence may be mapped to some subcarriers but not to other subcarriers. As shown FIG. 7B(b), subcarriers used for the PRACH sequence may be interlaced among a number of subcarriers. The PRACH sequence may be mapped to subcarriers 702, 704, 706, 708 and 710. For example, the PRACH sequence may not be mapped to three subcarriers 712, 714, and 716 between subcarriers 702 and 704. FIG. 7B illustrates an example of mapping to every fourth subcarrier, but other mappings may be used {e.g., see the examples in Table 3).

[0115] Af may be the subcarrier spacing between two subcarriers (e.g., two adjacent subcarriers such as 702 and 712). As the subcarrier spacing Af changes, the PRACH sequence may be mapped to different subcarriers. The number of subcarriers (e.g., subcarriers that are not used for a PRACH sequence) between two subcarriers used for the PRACH sequence may change (e.g., see Table 3). For example, the PRACH sequence may be mapped to certain subcarriers such that there may be more than three subcarriers that are not mapped to the PRACH sequence between subcarriers 702 and 704 if the subcarrier spacing Af decreases. For example, the number of subcarriers between two subcarriers used for the PRACH sequence (e.g., subcarriers 702 and 704) may vary in proportion to an upsampling ratio of a PRACH format (e.g., see Table 3). In an example, if the upsampling ratio is one, the number of subcarriers between two subcarriers used for the PRACH sequence (e.g., subcarriers 702 and 704) may become zero. When the number of subcarriers between subcarriers 702 and 704 becomes zero, the subcarriers used for the PRACH sequence may be contiguous (e.g., as shown in FIG. 7B(a)). If the upsampling ratio is two, the subcarriers used for the PRACH sequence may include alternate subcarriers, e.g., in the PRACH bandwidth.

[0116] A WTRU may receive information about a channel (e.g., a channel that the WTRU attempts to access). The information about the channel may include a subcarrier spacing for the channel. The information about the channel may indicate an increase or decrease in subcarrier spacing for the channel.

[0117] In FIG. 7B(b), a smaller subcarrier spacing than the subcarrier spacing in FIG. 7B(a) may be used. If the subcarrier spacing in (a) in FIG. 7B is Af, the subcarrier spacing in FIG. 7B(b) may be M/m, where m is an integer. If m = 4 in FIG. 7B(b), the subcarrier spacing may be 15 kHz (e.g., 60 kHz lm). In examples, the total number of subcarriers available may become ( m*L ) if the subcarrier spacing is M/m.

For example, in FIG. 7B(a), the subcarrier spacing Af may be 60 kHz, K may be 1024, resulting in an available channel bandwidth of 61 .440 MHz. If the subcarrier spacing is 15 kHz in FIG. 7B(b), a total of 4096 (e.g., 1024*m) subcarriers may be available in a channel bandwidth of 61 .440 MHz.

[0118] The total number of subcarriers available in the PRACH bandwidth may increase from FIG. 7B(a) to FIG. 7B(b). The total number of subcarriers available in the PRACH bandwidth may become m*L if the subcarrier spacing is M/m. For example, 556 (m* 139) subcarriers may be available for the PRACH sequence transmission within the PRACH bandwidth of 8.340 MHz. The PRACH bandwidth may not change from FIG. 7B(a) to FIG. 7B(b), e.g., as shown in ( m*L ) * (Af/m) = L*M Hz.

[0119] The PRACH sequence length may be fixed. For example, assuming the PRACH sequence length does not change as the subcarrier spacing changes from FIG. 7B(a) to FIG. 7B(b) (e.g., L in FIG. 7B(a) in and FIG. 713(b)), the PRACH sequence may be mapped to L subcarriers out of the m*L available subcarriers in the PRACH bandwidth {e.g., see Table 3). The L subcarriers may be selected out of the m*L available subcarriers using various techniques.

[0120] L subcarriers (e.g., every m'th subcarrier within the PRACH bandwidth) may be selected for PRACH sequence transmission. For example, the PRACH sequence may be upsampled with a ratio of m, e.g., before being mapping to subcarriers in the PRACH bandwidth, and the PRACH sequence length may be kept fixed by the mapping. In examples, zeros may be inserted between coefficients of the PRACH sequence before the PRACH sequence is mapped to the subcarriers in the PRACH bandwidth.

[0121] The L subcarriers for PRACH sequence transmission may be selected depending on the availability of a channel or the availability of subcarriers in the channel. For example, if not every m'th subcarrier is available within the PRACH bandwidth, the PRACH sequence may not be mapped to every m'th subcarrier. The PRACH sequence may be mapped to some other subcarriers in the PRACH bandwith to keep the sequence length fixed.

[0122] Subcarriers (e.g., within a PRACH bandwidth) may be indexed. Assuming that the subcarriers within the PRACH bandwidth (e.g., subcarriers (e.g., 702, 712, 714, 716, and 704) in FIG. 7B(b)) are denoted with indices 0, 1 , 2, ... , m*L -1 , the indices of the subcarriers to which the PRACH sequence is mapped (e.g., subcarriers (e.g., 702 and 704) in FIG. 7B(b)) may be written as n*m, n = 0 L-1. As an example, if L = 16 and m = 4, then the indices of the subcarriers that may be used for PRACH transmission (e.g., mapped to the PRACH sequence) may be the following set: {0, 4, 8, ...., 60}.

[0123] FIG. 7C shows an example of a PRACH transmission. This PRACH transmission may be equivalent to upsampling the PRACH sequence with a ratio of m and mapping the upsampled PRACH sequence to the IDFT, as shown in FIG. 7C. As shown in FIG. 7C, a PRACH sequence may be pre- processed. The pre-processing may include DFT transform, for example. The pre-processing may be optional. The PRACH sequence (e.g., the pre-processed PRACH sequence) may be upsampled (e.g., based on an upsampling ratio of m). The upsampled PRACH sequence may be mapped to subcarriers, e.g., through subcarrier mapping. The subcarrier mapping may include determining a subset of subcarriers from available subcarriers and mapping the PRACH sequence to the determined subset of subcarriers.

The indices of the subcarriers may be used for subcarrier mapping. For example, k may be the subcarrier index. The available subcarriers may be indexed as k = {0... N... N+ mxL-Ί ... m*K- 1}. The upsampled PRACH sequence may be mapped to subcarriers with index k = {N, L/+1 , ... N+ m*L- 1 }. The mapped subcarriers may be processed using IDFT, e.g., based on the PRACH bandwidth. The output of the IDFT may be a signal(s) with m repetitions (e.g., in m subcarriers). [0124] FIG. 7D illustrates a sample time domain signal (e.g., an output of the IDFT). FIG. 7B(a) illustrates an example of a contiguous PRACFI sequence. FIG. 7B(b) illustrates an example of an interleaved PRACFI sequence. For example, an IDFT of size 16 may be used for FIG. 7B(a). In FIG.

7B(a), the PRACFI sequence s = [1 +1 i -1-1 i -1 +1 i 1 -1 i]/sqrt(2) may be mapped to subcarriers with indices k = 0, 1 , 2, and 3. In this example, an IDFT of size 64 may be used in FIG. 7B (b). In FIG. 7B(b), the PRACFI sequence may be mapped to subcarriers with indices k =0, 4, 8, 12. The subcarrier spacing in FIG. 7B(b) may be Af. The PRACFI bandwidth may be 16DT If the PRACFI bandwidth in FIG. 7B(a) includes 4 subcarriers and m = 4, the PRACFI bandwidth in FIG. 7B(b) may include 16 subcarriers.

[0125] The size of the output signal of an IDFT may be in proportion to the size of the IDFT (e.g., with appropriate scaling). As shown in FIG. 7C, the signal at the output of the IDFT of size 64 may be a 4 times repetition of the signal at the output of the IDFT of the size of 16. The index k of the first subcarrier within the system bandwidth (e.g., the PRACFI bandwidth) to which the first coefficient of the PRACFI sequence is mapped (e.g., N in FIG. 7C) may satisfy the condition mod(A/,m) = 0, e.g., to attain (e.g., maintain) the repetitive signal structure.

[0126] In this example, with appropriate scaling and subcarrier mapping, a first time domain signal generated based on FIG. 7B(a) and a second time domain signal generated based on FIG. 7B(b) may be the same. Time domain properties of the PRACFI sequence in FIG. 7B(a) and FIG. 7B(b) may be the same.

[0127] Properties of an implementation with a smaller subcarrier spacing (e.g., the implementation in (b) of FIG. 7B) may include at least one of the following: the PRACFI may be transmitted with the same subcarrier spacing as other channels (PUSCH); more than one WTRU may be multiplexed in a PRACFI bandwidth; a WTRU may choose corresponding outputs of the IDFT to transmit all or some of the repetitions.

[0128] A wider subcarrier spacing may not be needed for PRACFI, and this may not be exclusive for PRACFI. A PUSCH may support a narrower subcarrier spacing. For example, if the PUSCH supports a narrower subcarrier spacing, the PRACFI may be transmitted with the same subcarrier spacing as PUSCFI. Transmitting the PRACFI and the PUSCFI using the same subcarrier spacing may reduce WTRU complexity.

[0129] More than one WTRU may be multiplexed in a PRACFI bandwidth. For example, up to m WTRUs may be multiplexed within a same PRACFI bandwidth. This may be achieved by introducing a circular shift, for example, after an upsampling block. The circular shift may be between 0 and m-1 . In an example, subcarriers with indices {N+r, AZ+m+r, N+2m+r, ...., N+m(L^)+r} may be populated, r may be a shift value. mod(A/+r,m) may not be equal to 0. The signal may not have a repetitive structure. A WTRU may be configured with the value of r. A WTRU may receive a signaling of the value of r. The WTRU may choose subcarriers to which a PRACH sequence maps. In examples, a first WTRU and a second WTRU may be multiplexed in a PRACH bandwidth. The first WTRU may use a PRACH format associated with a first PRACH sequence having a first cyclic shift, and the second WTRU may use a PRACH format associated with a second PRACH sequence having a second cyclic shift. The PRACH bandwidth may include at least one subcarrier mapped to a first PRACH sequence and at least one subcarrier mapped to a second PRACH sequence.

[0130] A WTRU may choose corresponding outputs of the IDFT to transmit all or some of the repetitions, e.g., after potentially inserting a cyclic prefix and/or a guard interval.

[0131] A WTRU may determine a PRACH format to use, for example, based on the information about the channel. A specific PRACH format may be associated or and/or determined based on one or more of: a subcarrier spacing, an upsampling ratio, a sequence length, or a PRACH bandwidth. For example, a WTRU may generate a PRACH preamble using a wider or narrower subcarrier spacing. A sample PRACH configuration table is provided in Table 3. A WTRU may be configured with one or more PRACH formats. As shown in Table 3, the sequence length may be designed to be fixed from one PRACH format to another PRACH format. One or more of the subsampling ratio, subcarrier spacing, and/or PRACH bandwidth may vary from one PRACH format to another PRACH format. As shown in PRACH formats 1-3, the upsampling ratio may vary based on (e.g., in proportion to) the subcarrier spacing, e.g., to keep the sequence length fixed.

[0132] A PRACH format may be selected and/or used to control the transmit power of a WTRU. For example, a WTRU may be configured with a PRACH format with a narrower PRACH bandwidth (e.g., due to the power spectral density (PSD)/MHz regulations). A narrower transmission bandwidth may result in a lower transmit power. The WTRU may be close to a base station. A WTRU may be configured with the PRACH format having the narrower PRACH bandwidth, for example, when an already connected WTRU is preparing for a handover. A WTRU may be configured with a PRACH format having the narrower PRACH bandwidth and multiple PRACH OFDM symbol repetitions, e.g., to compensate the power loss due to the narrowband PRACH transmission.

[0133] In an example, a WTRU may (e.g., initially) start an attempt to access a channel by transmitting a PRACH preamble using a first PRACH format. The WTRU may determine whether the attempt to access the channel was successful based on an indication. The WTRU may receive the indication along with information about the channel that the WTRU receives. If the random access is not successful (e.g., as determined by the WTRU based on the indication), the WTRU may change the first PRACH format, e.g., so that the WTRU can transmit with a larger power. For example, the WTRU may change the first PRACH format to a second PRACH format having a larger PRACH bandwidth and/or a greater subcarrier spacing {e.g., among PRACH formats listed in Table 3). As an example, a WTRU may use PRACH format 5 in its first attempt; if unsuccessful, the WTRU may try PRACH format 4 in its second attempt, etc. In an example, a WTRU may use PRACH format 5 in its first attempt; if unsuccessful, the WTRU may try PRACH format 3 in its second attempt, etc.

Table 3: Sample PRACH configuration table

[0134] LBT considerations may be used to perform LBT.

[0135] A narrow-band PRACH may be used in relation to channel access and/or LBT. A WTRU may attempt to access a narrow-band PRACH. The WTRU that attempts to access the narrow-band PRACH may perform LBT on a portion (e.g., a sub-set) of a bandwidth in which the PRACH is located (e.g., a sub band LBT). When the sub-band LBT is performed, an energy measurement may be performed across the bandwidth of a PRACH resource or across a minimum bandwidth, for example, whichever is narrower.

The minimum bandwidth may be narrower than the bandwidth of the PRACH resource. The measured energy may be compared to a threshold. The threshold may be scaled, e.g., according to the bandwidth of the sub-band. For example, if a LBT threshold for a 20MHz channel (e.g., in 5GHz spectrum) is -72dBm, the LBT threshold for a 2 MHz sub-band (e.g., in which a narrow-band PRACH fits) may be -62dBm. The 2 MHz sub-band may be the bandwidth in which a narrow-band PRACH fits.

[0136] A WTRU may perform multiple sub-band LBT(s), e.g., in parallel. At least one (e.g., each) of the multiple sub-band LBT(s) may be associated with a scheduled PRACH resource. For example, a gNB may have scheduled multiple narrow-band PRACH resources. The multiple narrow-band PRACH resources may be multiplexed in frequency. A sub-band LBT may be associated with a narrow-band PRACH resource. A WTRU may perform multiple sub-band LBT(s) (e.g., in parallel), and one or multiple sub-band LBT(s) may be completed successfully. In examples, upon the successful completion of one or multiple sub-band LBT(s), the WTRU may access a scheduled PRACH resource(s) associated with a successfully completed sub-band LBT(s) and/or transmit a preamble(s) on the scheduled PRACH resource(s). The WTRU behavior including performing multiple sub-band LBT(s) may increase the chance of a successful channel access by the WTRU. In examples, when performing multiple sub-band LBT(s) in parallel, a WTRU may perform a wideband energy measurement and/or may perform appropriate partitioning, e.g., to obtain measured energy on individual sub-bands. The measured energy may be compared with a sub band LBT threshold, e.g., after the wideband energy measurement and/or appropriate partitioning to obtain measured energy on individual sub-bands.

[0137] An LBT threshold used in a sub-band LBT(s) may be scaled, e.g., according to a bandwidth of a PRACH resource {e.g., a scheduled PRACH resource). In examples, a gNB may schedule multiple PRACH resources (e.g., narrow-band PRACH resources) that are multiplexed in frequency. A (e.g., each) narrow-band PRACH resource may be associated (e.g., scheduled) with one or more pre-configured bandwidth size. A WTRU may perform multiple sub-band LBTs (e.g., in parallel) by comparing a measured energy with an appropriate LBT threshold. A (e.g., each) sub-band LBT(s) may be associated with a scheduled PRACH resource, e.g., a narrow-band PRACH resource associated with one or more pre configured bandwidth size. An appropriate LBT threshold may be a LBT threshold that is scaled, e.g., according to the bandwidth (e.g., one or more pre-configured bandwidth size) of the narrow-band PRACH resource. The WTRU may access the associated PRACH resource(s) and/or transmit the preamble on the associated PRACH resource(s), e.g., upon the successful completion of one or multiple sub-band LBT.

[0138] When a WTRU accesses more than one PRACH resources (e.g., upon a successful LBT completion on each of the more than one PRACH resources), the WTRU may be configured to use a same PRACH sequence across some (e.g., all) of the resources and/or various PRACH sequences across some (e.g., all) of multiple PRACH resources. A configuration of using a same PRACH sequence across some (e.g., all) of the resources may enhance PRACH sequence detection, e.g., at the gNB side. A configuration of using various PRACH sequences across multiple PRACH resources may reduce the chance of PRACH sequence collision, e.g., among WTRUs accessing a same PRACH resource.

[0139] If a WTRU is configured to use various PRACH sequences across multiple PRACH resources, the WTRU's behavior may include one or more of the following. The WTRU may receive multiple random access responses (RARs). A (e.g., each) RAR may be associated with one of the multiple (e.g., transmitted) PRACH resources. For example, each RAR may correspond to one of the multiple (e.g., earlier-transmitted) PRACH resources. If the WTRU receives multiple RARs, the WTRU may take a subsequent action(s) for one of the received multiple RARs. For example, the WTRU may not take a subsequent action for other ones of the received multiple RARs. In examples, the WTRU may take an action(s) for the RAR that is received first and/or ignore RARs that are received later than (e.g., subsequent to) the first-received RAR. The RARs may be associated with earlier transmitted PRACH sequences. The WTRU may take an action for an earliest-received RAR(s) that schedules for a subsequent transmission(s) by the WTRU. The WTRU may not take an action(s) for other received RARs {e.g., ones that schedule for a subsequent transmission(s)) by the WTRU. The WTRU may prepare to send a first scheduled (e.g., in a previously received RAR) transmission that is allowed by an appropriate LBT procedure. In case of LBT failure, the WTRU may prepare to send a second scheduled (e.g., within the subsequent RAR) transmission that is allowed by an appropriate LBT procedure and so on.

[0140] In examples, a gNB may send multiple RAR responses e.g., in response to one PRACH transmission by a WTRU. A RAR may include an indication that the RAR is associated with the PRACH transmission. A (e.g., each) RAR response may provide a scheduled resource for subsequent transmission(s) by the WTRU (e.g., WTRU's response). The WTRU may take an action(s) for one of the received multiple RARs, e.g., following the same behavior as described herein to transmit in, for example, a best resource, the first resource, or the first resource after a successful LBT for the resource.

[0141] PUSCH puncturing may be performed.

[0142] Resource blocks used for PRACH and PUSCH may be adjacent (e.g., as shown in FIG. 7A), e.g., when PRACH uses B-IFDMA. The resource blocks (e.g., for PRACH and PUSCH) may be used by different WTRUs. When the numerology(ies) (e.g., the subcarrier spacing(s)) of PRACH and PUSCH are different, leakage may occur, for example, from the PUSCH signal to the PRACH signal. Applying a filter to a transmission bandwidth (e.g., the whole transmission bandwidth) may or may not reduce leakage, e.g., due to the distributed allocation of RBs. Leakage may be reduced by various techniques. For example, applying windowing to the OFDM signal may reduce leakage. Filtering RBs (e.g., each RB (e.g., individually)) may reduce leakage. Some guard band(s) between the PRACH and PUSCH RBs may be used (e.g., as necessary). In examples, the WTRU transmitting in a PUSCH RB may puncture one or more of edge subcarriers of the PUSCH RB. A WTRU may rate match the WTRU's codeblock, e.g. adjust the WTRU's transmission rate. One or more of edge subcarriers of the PUSCH RB may be nulled out. For example, one or more of edge subcarriers of the PUSCH RB may not be loaded with data symbols. FIG. 8 shows an example of puncturing PUSCH. Subcarriers on one or both of the edges of the PUSCH RB may be punctured (e.g., as required). As shown in FIG. 8, PRACH resources and PUSCH resources may be adjacent. PRACH resources may include multiple PRACH subcarriers. PUSCH resources may include multiple PUSCH subcarriers. PUSCH subcarrier 802 and 804 may be on the edge of the PUSCH resources. In the example shown in FIG. 8, PUSCH subcarrier 802 and 804 may be punctured. The number and location (e.g., identifiers) of the punctured subcarriers in RBs (e.g., each RB of an interlace) may be indicated (e.g., signaled) to a WTRU. The indication may be based on at least one of the following: semi-static configuration; dynamic signaling; or implicit determination by the WTRU. In the example shown in FIG. 8, the number of the punctured subcarriers may be 2. The number of 2 and/or the location of the PUSCH subcarrier 802 and 804 may be indicated to the WTRU.

[0143] In examples, a WTRU may learn {e.g., through an indication) the time/frequency location(s) of PRACH resources (e.g., PRACH RBs in a cell). The WTRU may determine whether PUSCH RBs are adjacent to the PRACH RBs, e.g., when the WTRU is to transmit in the PUSCH. The WTRU may determine whether the frequency domain distance between two types of RBs (e.g., PRACH RBs and PUSCH RBs) is below a threshold. If the frequency domain distance between PRACH RBs and PUSCH RBs is below a threshold, the WTRU may determine that the PRACH RBs and PUSCH RBs are adjacent.

If the WTRU determines that the PRACH RBs and PUSCH RBs are adjacent, the WTRU may puncture certain subcarriers (e.g., PUSCH subcarriers adjacent to the PRACH RBs). The number of subcarriers to be punctured and/or the location(s) of the subcarriers to be punctured may be configured by a central controller or may be fixed and determined, e.g., by a standard. The location(s) of the subcarriers may include left edge, right edge, both left and right edges, etc.

[0144] In examples, a central controller may indicate (e.g., command) a WTRU to apply puncturing, e.g., using a control channel. The central controller may turn on and/or turn off the puncturing, e.g., using the control channel. The central controller may configure the number of the subcarriers to be punctured and/or the location(s) of the subcarriers to be punctured (e.g., left edge, right edge, both edges, etc.).

[0145] In examples, not all of the subcarriers in a chunk allocated to PRACH transmission may be utilized. Some subcarriers may be left as guard subcarriers (e.g., null subcarriers). As an example, as shown in FIG. 7A(a), two PRACH RBs may constitute one PRACH chunk in an interlace. A WTRU that is assigned this interlace for PRACH preamble transmission may leave the edge subcarriers of the chunk(s) unused, and may map sequence coefficients to the middle portion of the chunk(s) (e.g., only). The number of the subcarriers to be left unused and their location (e.g., left edge, right edge, both edges, etc.) may be configured, e.g., by a central controller.

[0146] In examples, a PRACH sequence may be mapped to a portion of the subcarriers (e.g., only a portion of the subcarriers) in a PRACH chunk. The remaining subcarriers may be left empty. For example, the middle subcarriers of a chunk may be used to transmit the sequence, while the edge subcarriers may be null. The length of the PRACH sequence may be chosen such that it is equal to the number of utilized subcarriers. As an example, as shown in FIG. 7A(a), two PRACH RBs may constitute two different PRACH chunks in two PRACH interlaces. If one interlace has 120 subcarriers (e.g., 10 chunks times 12 subcarriers), the length of the sequence may be, for example, chosen to be 59 (e.g., instead of 1 13). In this case, 6 samples (e.g., elements) of the sequence (e.g., the first six samples) may be mapped to the middle subcarriers of the first chunk. Six samples (e.g., samples 7-12) may be mapped to the middle subcarriers of the second chunk. Six samples (e.g., samples 13-18) may be mapped to the middle subcarriers of the third chunk, etc. A chunk (e.g., the last chunk) may be used to transmit samples (e.g., samples 55 to 59) in its middle subcarriers.

[0147] PRACH sequence generation may be performed using Golay sequences.

[0148] Golay sequences may be used as a PRACH sequence, The Golay sequences' PAPR may be limited by 3 dB. Golay sequences may be generated by the Golay's concatenation construction. For example, (a, b) and (c, d) may be complementary Golay sequences of lengths N and M, respectively. A Golay sequence with 2N non-zero parts may be generated, and/or parts (e.g., each part) may be mapped to a (e.g., one) chunk(s) of an interlace, e.g., using B-IDMA resource allocation. For example, a_n c, n =

1, ... , N may be mapped to the (2n— l)’th chunk while b_nd, n = 1, ... , N may be mapped to the (2n)'th chunk. FIG. 9 shows an example of a PRACH OFDM signal generation using Golay sequences.

A sample PRACH OFDM signal generation is shown in FIG. 9 for a = [1 1 1 -1 i 1 i]; b = [1 1 i -1 1 -1 i]; c = [1

shown in FIG. 9, c may be multiplied with a1-5, and the multiplication result may be mapped to different RBs (e.g., as shown in FIG. 9). d may be multiplied with b1 -5, and the multiplication result may be mapped to different RBs (e.g., as shown in FIG. 9).

[0149] The length of the Golay sequence may depend on certain factors. A Golay sequences of a length (e.g., arbitrary length) may be generated. The length of the Golay sequence may depend on the number of subcarriers allocated for a PRACH transmission. For example, if a PRACH interlace includes 10 RBs of 12 subcarriers, a Golay sequence of length-120 may be generated (e.g., as described herein). As another example, if a PRACH interlace includes 12 RBs of 12 subcarriers, a Golay sequence of length-144 may be generated (e.g., as described herein by using (a, b) of length-6 (e.g., N = 6)).

[0150] In some cases, a longer PRACH sequence may be used. For example, a long PRACH sequence (e.g., in NR) may have 839 coefficients and/or use 1.25 or 5 kHz as subcarrier spacing.

[0151] For example, 10 chunks may be used, where the bandwidth of chunks (e.g., each chunk) is 180 kHz. A (e.g., each) chunk may have 144 PRACH subcarriers, e.g., for a 1.25 kHz subcarrier spacing. A sequence with 1440 elements may be transmitted, e.g., if subcarriers (e.g., all subcarriers) are utilized. A shorter sequence may be transmitted, e.g., if chunks are partially utilized. As an example, 96 subcarriers in 10 chunks (e.g., each chunk) may be utilized, resulting in a sequence of 960 elements (e.g., length of the sequence is 960). The sequence of 960 elements may be generated, e.g., using one of construction implementations. For example, the signal generation shown in FIG. 9 may be used, with (c, d) being sequences of length-96.

[0152] A sequence of length-96 may be generated recursively, e.g., using Eq. 5. ( x,y ) ® (.x\y, x\y) Eq. 5 where x|y may refer to concatenation of x and y. y may refer to conjugating and reversing the order of the elements of y . x and y may be a Golay complementary pair of sequences. Given a pair of length-N sequences x and y, Eq. 5 may show how to generate a length-2N pair of sequences. The first sequence of the pair may be x|y, and the second sequence of the pair may be x|y. As an example, if x and y are sequences of length-12, using this recursion three times {e.g., as shown in Eq. 6) may generate sequences c and d of length-96:

(x, y) ® (p = x\ y, q = x\y) Eq. 4

(P, q) ® (t = p\q, r = p\q) Eq. 4

(t, r) ® (c = t\r, d = t\r) Eq. 6

[0153] As an example, if x = [1 1 1 1 -1 -1 -1 1 1i -1i -1 1] and y = [1 1 1i 1i 1 1 -1 1 1 -1 1 -1], recursive construction may generate the following sequences:

c = [1.0000 + 0.0000i 1.0000 + 0.0000Ϊ 1.0000 + 0.0000Ϊ 1.0000 + 0.0000Ϊ -1.0000 + 0.0000Ϊ -1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 + 1.OOOOi 0.0000 - 1.OOOOi -1.0000 + O.OOOOi 1.0000 + 0.0000i 1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 + 1. OOOOi 0.0000 + 1.OOOOi 1.0000 +

O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi

1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 + 1. OOOOi

0.0000 - 1. OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 +

O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 - 1. OOOOi 0.0000 - 1. OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 + 1. OOOOi 0.0000 - 1. OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 + 1.00000 0.0000 + 1.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi - 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 + 1. OOOOi 0.0000 + 1. OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 0.0000 + 1.OOOOi 0.0000 - 1. OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi],

d = [ 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000

+ O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 + 1. OOOOi 0.0000 - 1. OOOOi -1.0000 + O.OOOOi

1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 + 1. OOOOi 0.0000 + 1.OOOOi 1.0000 + O.OOOOi 1.0000 + 0.0000Ϊ -1.0000 + 0.0000Ϊ 1.0000 + 0.0000Ϊ 1.0000 + 0.0000Ϊ -1.0000 + O.OOOOi 1.0000 + 0.0000Ϊ -1.0000 + 0.0000Ϊ 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 + 1.0000Ϊ 0.0000 - LOOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 - LOOOOi 0.0000 - LOOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 + LOOOOi 0.0000 - LOOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 - LOOOOi 0.0000 - LOOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi - 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 0.0000 - LOOOOi 0.0000 - LOOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi 0.0000 + LOOOOi 0.0000 - LOOOOi 1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000 + O.OOOOi -1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi 1.0000 + O.OOOOi],

[0154] The PRACH sequence may be designed off-line using various Golay construction

implementations. The length of the PRACH sequence may be fixed. A central controller may configure a WTRU with parameters including one or more of basic Golay sequences {e.g., a, b, c, and d), a Golay construction implementation, and/or other parameters. The WTRU may construct the sequence of a certain (e.g., required) length offline, e.g., based on the parameters. Sequences may be constructed and/or specified in a standard.

[0155] Common back-off counter-assisted preamble transmission may be performed.

[0156] Transmission of a preamble may be subject to LBT, e.g., in unlicensed spectrum. The availability of RACH time resources (e.g., the OFDM symbols to be used for preamble transmission (PT)) may depend on channel conditions. A preamble transmission window (PTW) may be used (e.g., defined). Defining a PTW may improve a probability of random access transmission. FIG. 10 shows an example of LBT in PRACH preamble transmission. A PTW (e.g., an RACH window between time instance tO and time instance t3, as shown in FIG. 10) may include an interval of time in which a WTRU may transmit a preamble. A PTW may be pre-defined or configured, e.g., by a network.

[0157] As shown in FIG. 10, a WTRU may begin an LBT process when a PTW starts, for example at time instance tO. The WTRU may start transmitting a preamble, for example at time instance t1. Time instance t1 may selected when a channel becomes available. Time instance t1 may be selected such that the OFDM symbols align in time. For example, the time when the preamble is transmitted may align with the OFDM symbols within a slot. The WTRU may transmit a reservation signal to occupy the channel, e.g., if the channel becomes available before time instance t1. Preamble transmission may finish at time instance t2. Time instance t2 may be less or equal to time instance t3. If time instance t2 is determined (e.g., estimated/calculated) to be greater than time instance t3, the WTRU may not start the preamble transmission. For example, the WTRU may not start the preamble transmission if the preamble transmission is determined to exceed the maximum PTW size due to a duration of the preamble (e.g., before the WTRU can finish the preamble transmission).

[0158] Different WTRUs may determine (e.g., find) channel availability at different times, e.g., due to LBT operation. FIG. 11 shows an example of multiple WTRUs performing LBT and PRACFI preamble transmission(s) in a PTW. In FIG. 11 , RACH WTRU 1 and RACH WTRU 2 transmit PTs in a RACH window between time instance tO and time instance t3. As shown in FIG. 11(a), RACFI WTRU 1 may perform LBT-1. RACFI WTRU 1 may start a PT at time instance t1 after RACFI WTRU 1 performs LBT-1 and finish the PT at time instance t2. RACFI WTRU 2 may perform LBT-2. RACFI WTRU 2 may start a PT at time instance t4 after RACFI WTRU 2 performs LBT-2 and finish the PT at time instance t5. As shown in FIG. 11(a), LBT-1 and LBT-2 are different. The PT by RACH WTRU 1 and the PT by RACH WTRU 2 do not completely overlap. Detection performance at the receiver may degrade and/or deteriorate, e.g., if the PRACH preamble transmissions from different WTRUs do not (e.g., completely) overlap.

[0159] Different WTRUs may be configured to use a common back-off counter. For example, by using a common back-off counter, different WTRUs that are configured with a same PTW may align LBTs. The WTRUs may (e.g., all) finish the LBT at the same time, e.g., as shown in FIG. 11 (b). Some or all of the WTRUs may find the channel available and/or may start preamble transmission e.g., simultaneously as shown in FIG. 11 (b). By using a common back-off counter, a WTRU may wait for the next PTW opportunity, e.g., if the channel is not available when the WTRU's counter expires.

[0160] A common back-off counter may be configured using different implementations. Multiple WTRUs may be partitioned into sub-groups. A sub-group (e.g., each sub-group) of WTRUs may be configured with a common back-off counter. WTRU group-specific information may be communicated to the sub-group of WTRUs. WTRU group-specific information may contain the configuration of a common back-off counter. The sub-group of WTRUs may receive the same information regarding the common back-off counter (e.g., for PT). A common back-off counter may allow the WTRUs within the same sub-group to be aligned with each other for PT.

[0161] PTs of WTRUs within a same beam or cross different beams may be aligned using a back-off counter. A beam-specific back-off counter may be used, e.g., in a beam-centric system. A common back off counter may be used for WTRUs within a same beam, e.g., since WTRUs residing in the same beam may receive same information. Different back-off counters or a common back-off counter may be used for WTRUs in different beams. Different back-off counters may be used for WTRUs in different beams based on that the WTRUs in different beams may receive different information and/or may not interfere with each other {e.g., for PT). A common back-off counter may be used to align WTRUs in different beams, e.g., when the different beams interfere (e.g., have mutual interferences). WTRUs in different beams may receive a common back-off counter, e.g., by different information transmitted from a network. The network may dynamically control an individual beam or a group of beams (e.g., all beams), which may be used to transmit a common back-off counter to WTRUs. When (e.g., once) a WTRU receives the information for a common back-off counter, the WTRU may utilize the information for the common back-off counter to align a preamble transmission(s) within the same beam, across some different beams or all different beams.

[0162] Although the features and elements of the devices and/or techniques are described in particular combinations, one or more, or each feature and/or element can be used alone without the other features and/or elements, or in various combinations with or without other features and/or elements.

[0163] Although one or more of the techniques described herein consider LTE, LTE-A, NR, and/or 5G specific protocols, it is understood that the techniques described herein are not restricted to this scenario and are applicable to other wireless systems as well.

[0164] The processes described above may be implemented in a computer program, software, and/or firmware incorporated in a computer-readable medium for execution by a computer and/or processor. Examples of computer-readable media include, but are not limited to, electronic signals (transmitted over wired and/or wireless connections) and/or computer-readable storage media. Examples of computer- readable storage media include, but are not limited to, a read only memory (ROM), a random-access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as, but not limited to, internal hard disks and removable disks, magneto-optical media, and/or optical media such as CD-ROM disks, and/or digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, terminal, base station, RNC, and/or any host computer.

Claims

CLAIMS What is Claimed:

1 . A wireless transmit/receive unit (WTRU) comprising:

a processor configured to:

determine information associated with a physical random access channel, wherein the information comprises a subcarrier spacing associated with the physical random access channel;

determine a format associated with the physical random access channel, wherein the format comprises at least one of an upsampling ratio or a sequence length, wherein the sequence length is fixed and the upsampling ratio varies based on the information associated with the physical random access channel, wherein the processor is configured to:

if the physical random access channel has a first subcarrier spacing, use a first upsampling ratio, and

if the physical random access channel has a second subcarrier spacing, use a second upsampling ratio that keeps the sequence length at a fixed value; and perform random access using the determined format associated with the physical random access channel.

2. The WTRU of claim 1 , wherein the upsampling ratio indicates a set of subcarriers used for a sequence associated with the physical random access channel and the set of subcarriers is within a bandwidth associated with the physical random access channel.

3. The WTRU of claim 1 , wherein the first subcarrier spacing is greater than the second subcarrier spacing and the first upsampling ratio is less than the second upsampling ratio.

4. The WTRU of claim 1 , wherein the processor is further configured to:

determine whether a first attempt to access the channel was successful based on an indication received in the information about the channel, wherein the first attempt was based on a first format comprising an upsampling ratio associated with the first attempt;

determine, for a second attempt, a second format comprising an upsampling ratio associated with the second attempt based on a determination that the first attempt was unsuccessful, wherein the upsampling ratio associated with the first attempt and the upsampling ratio associated with the second attempt are different; and perform random access using the determined second format associated with the physical random access channel.

5. The WTRU of claim 1 , wherein the set of subcarriers comprises contiguous subcarriers in the bandwidth associated with the physical random access channel if the upsampling ratio is one, and the set of subcarriers comprises alternate subcarriers in the bandwidth associated with the physical random access channel if the upsampling ratio is two.

6. The WTRU of claim 1 , wherein the determined PRACH format comprises a subcarrier spacing that is the same as a subcarrier spacing for a physical uplink share channel (PUSCH) to be transmitted by the WTRU.

7. The WTRU of claim 1 , wherein the processor is configured to determine an output of an inverse discrete fourier transform (IDFT) to transmit a PRACH preamble using the determined PRACH format.

8. A method performed by a wireless transmit/receive unit (WTRU), comprising:

determining information associated with a physical random access channel, wherein the information comprises a subcarrier spacing associated with the physical random access channel;

determining a format associated with the physical random access channel, wherein the format comprises at least one of an upsampling ratio or a sequence length, wherein the sequence length is fixed and the upsampling ratio varies based on the information associated with the physical random access channel, wherein:

if the physical random access channel has a first subcarrier spacing, a first upsampling ratio is used, and

if the physical random access channel has a second subcarrier spacing, a second upsampling ratio that keeps the sequence length at a fixed value is used; and

performing random access using the determined format associated with the physical random access channel.

9. The method of claim 8, wherein the upsampling ratio indicates a set of subcarriers used for a sequence associated with the physical random access channel and the set of subcarriers is within a bandwidth associated with the physical random access channel.

10. The method of claim 8, wherein the first subcarrier spacing is greater than the second subcarrier spacing and the first upsampling ratio is less than the second upsampling ratio.

11. The method of claim 8, further comprising:

determining whether a first attempt to access the channel was successful based on an indication received in the information about the channel, wherein the first attempt was based on a first format comprising an upsampling ratio associated with the first attempt;

determining, for a second attempt, a second format comprising an upsampling ratio associated with the second attempt based on a determination that the first attempt was unsuccessful, wherein the upsampling ratio associated with the first attempt and the upsampling ratio associated with the second attempt are different; and

performing random access using the determined second format associated with the physical random access channel.

12. The method of claim 8, wherein the set of subcarriers comprises contiguous subcarriers in the bandwidth associated with the physical random access channel if the upsampling ratio is one, and the set of subcarriers comprises alternate subcarriers in the bandwidth associated with the physical random access channel if the upsampling ratio is two.

13. The method of claim 8, wherein the determined PRACH format comprises a subcarrier spacing that is the same as a subcarrier spacing for a physical uplink share channel (PUSCH) to be transmitted by the WTRU.

14. The method of claim 8, further comprising determining an output of an inverse discrete fourier transform (IDFT) to transmit a PRACH preamble using the determined PRACH format.