WO2019143937A1

WO2019143937A1 - Synchronization signal and paging for new radio-unlicensed (nr-u) band communications

Info

Publication number: WO2019143937A1
Application number: PCT/US2019/014195
Authority: WO
Inventors: Kyle Jung-Lin Pan; Nirav B. Shah; Fengjun Xi
Original assignee: Idac Holdings, Inc.
Priority date: 2018-01-19
Filing date: 2019-01-18
Publication date: 2019-07-25
Also published as: TW201939913A

Abstract

Methods, devices, and systems using a synchronization signal (SS)/Physical Broadcast Channel (PBCH) block are disclosed herein. In an example, a wireless transmit/receive unit (WTRU) may detect an SS/PBCH block. The WTRU may then obtain one or more indications regarding a joint synchronization signal block (SSB) index and a time shift from the detected SS/PBCH block. In an example, one or more indications may be obtained from an SS in the detected SS/PBCH block. In another example, one or more indications may be obtained from a PBCH in the detected SS/PBCH block. Further, the WTRU may derive at least one of frame timing information, slot timing information and symbol timing information based on the obtained joint SSB index and time shift. Also, the WTRU may obtain timing information for detection of a channel access indicator (CAI), an SSB indication or both. Further, the WTRU may perform SSB measurements.

Description

SYNCHRONIZATION SIGNAL AND PAGING FOR NEW RADIO-UNLICENSED (NR-U) BAND

COMMUNICATIONS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/619,673 filed January 19, 2018 and U.S. Provisional Application No. 62/716,077 filed August 8, 2018, which are incorporated by reference as if fully set forth herein.

BACKGROUND

[0002] A broad classification of use cases for emerging fifth generation (5G) wireless systems may be depicted as Enhanced Mobile Broadband (eMBB), Massive Machine Type Communications (mMTC) and Ultra Reliable and Low Latency Communications (URLLC), based on the general requirements set out by the International Telecommunication Union-Radio Communication Sector (ITU-R), the Next Generation Mobile Networks (NGMN) and the 3^rd Generation Partnership Project (3GPP). Different use cases may focus on different requirements such as higher data rate, higher spectrum efficiency, low power and higher energy efficiency, lower latency and higher reliability. A wide range of spectrum bands ranging from 700 megahertz (MHz) to 80 gigahertz (GHz) may be considered for a variety of deployment scenarios. As carrier frequency increases, severe path loss can become a crucial limitation to the ability to guarantee a sufficient coverage area. Transmission in millimeter wave systems could additionally suffer from non-line-of- sight losses, such as, for example, diffraction loss, penetration loss, oxygen absorption loss, foliage loss, and the like. During initial access, a base station and a wireless transmit/receive unit (WTRU) may need to overcome these high path losses and discover each other. Utilizing dozens or even hundreds of antenna elements to generate one or more beam formed signals may provide an effective way to compensate for the severe path loss by providing significant beam forming gain. Beamforming techniques may include digital beamforming, analogue beamforming and hybrid beamforming.

[0003] Cell search is a procedure by which a WTRU may acquire time and frequency synchronization with a cell and may detect the Cell identity (ID) of that cell. Long Term Evolution (LTE) synchronization signals may be transmitted in the 0th and 5th subframes of every radio frame and may be used for time and frequency synchronization during initialization. As part of the system acquisition process, a WTRU may synchronize sequentially to the orthogonal frequency division multiplexing (OFDM) symbol, slot, subframe, half-frame, and radio frame based on the synchronization signals. [0004] Paging may be used for network-initiated connection setup when the terminal is in an RRCJDLE mode. In LTE, the same mechanism as for downlink data transmission on the downlink shared channel (DL-SCH) may be used and the mobile terminal may monitor the L1/L2 control signaling for downlink scheduling assignments related to paging. Since the location of the mobile terminal typically is not known on a cell level, the paging message is typically transmitted across multiple cells in the so-called tracking area.

SUMMARY

[0005] Methods, devices, and systems using a synchronization signal (SS)/Physical

Broadcast Channel (PBCH) block are disclosed herein. In an example, a wireless transmit/receive unit (WTRU) may detect an SS/PBCH block. The WTRU may then obtain one or more indications regarding a joint synchronization signal block (SSB) index and a time shift from the detected SS/PBCH block. In an example, one or more indications may be obtained from an SS in the detected SS/PBCH block. In another example, one or more indications may be obtained from a PBCH in the detected SS/PBCH block. Further, the WTRU may derive at least one of frame timing information, slot timing information and symbol timing information based on the obtained joint SSB index and time shift. Also, the WTRU may obtain timing information for detection of a channel access indicator (CAI), an SSB indication or both. On a condition that the WTRU then successfully detects one or both of the CAI and the SSB indication, the WTRU may derive time locations of SSBs based on the detected one or both of the CAI and the SSB indication. Accordingly, the WTRU may perform SSB measurements for actually transmitted SSBs. On a condition that the WTRU does not successfully detect at least one of the CAI and the SSB indication, the WTRU may search for and measure all SSBs during an SSB sweep. For example, the WTRU may search all SSB time locations during the SSB sweep. The WTRU may also measure all SSBs received during the SSB sweep.

[0006] In a further example, the CAI may have a state of one listen before talk (LBT) procedure for all SSB transmissions during an SSB sweep. In another example, the CAI may have a state of one LBT procedure per synchronization signal block group (SSBG). Moreover, there may be a break between SSBGs. In an additional example, the CAI may have a state of one LBT procedure per SSB. Further, the gNB may perform a widebeam LBT procedure for SSBGs in an synchronization signal burst set (SSBS). The gNB may indicate the performance of this procedure to the WTRU. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, wherein like reference numerals in the figures indicate like elements, and wherein:

[0008] FIG. 1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented;

[0009] FIG. 1B is a system diagram illustrating an example wireless transmit/receive unit

(WTRU) that may be used within the communications system illustrated in FIG. 1A according to an embodiment;

[0010] 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. 1A according to an embodiment;

[0011] FIG. 1D 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. 1A according to an embodiment;

[0012] FIG. 2 is a diagram illustrating an example Channel Access Indicator (CAI), synchronization signal block group (SSBG) indicator and synchronization signal block (SSB) indicator;

[0013] FIG. 3 is a diagram illustrating an example CAI with savings on an SSBG indicator and an SSB indicator;

[0014] FIG. 4 is a diagram illustrating an example CAI and SSBG indicator with savings on an SSB indicator;

[0015] FIG. 5 is a diagram illustrating an example updated SSB and SSBG using dynamic listen before talk (LBT)-based SSB and SSBG indication.

[0016] FIG 6 is a flow diagram illustrating an example of procedures for channel access with SSB, SSBG and synchronization signal burst set (SSBS);

[0017] FIG. 7A is a diagram illustrating an example of LBT for channel access with SSB,

SSBG and SSBS;

[0018] FIG. 7B is a diagram illustrating another example of LBT for channel access with

SSB, SSBG and SSBS;

[0019] FIG. 8 is a flow diagram illustrating an example of LBT for channel accessing using a joint SSB index and a time shift;

[0020] FIG. 9 is a diagram illustrating an example remaining minimum system information

(RMSI) with a partial collision with an SSBS; [0021] FIG. 10 is a diagram illustrating an example RMSI with a full collision with an SSBS;

[0022] FIG. 11 is a diagram illustrating an example LBT, RMSI and SSBS where the SSBS follows the RMSI;

[0023] FIG. 12 is a diagram illustrating an example LBT, RMSI and SSBS where the SSBS may not follow the RMSI;

[0024] FIG. 13 is a diagram illustrating an example RMSI which has a larger periodicity than an SSBS;

[0025] FIG. 14 is a diagram illustrating an example RMSI which has smaller periodicity than an SSBS;

[0026] FIG. 15 is a diagram illustrating an example RMSI which has the same periodicity as an SSBS;

[0027] FIG. 16 is a diagram illustrating an example discovery reference signal (DRS) measurement timing configuration (DMTC) window defined for an entire DRS Sweep;

[0028] Fig. 17 is a diagram illustrating an example DMTC window defined for each DRS location;

[0029] FIG. 18 is a diagram illustrating an example DMTC defined for a set of beams;

[0030] FIG. 19 is a flow diagram illustrating an example method for paging using beam feedback;

[0031] FIG. 20 is a flow diagram illustrating an another example method for paging; and

[0032] FIG. 21 is a diagram illustrating an example of paging in bi-directional slots.

DETAILED DESCRIPTION

[0033] 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.

[0034] 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 106/115, 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 (for example, remote surgery), an industrial device and applications (for example, 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.

[0035] 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.

[0036] 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.

[0037] 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 (for example, 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).

[0038] 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 115/116/117 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and/or Evolved HSPA (FISPA+). HSPA may include High-Speed Downlink (DL) Packet Access (FISDPA) and/or High- Speed UL Packet Access (FISUPA).

[0039] 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).

[0040] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR Radio Access , which may establish the air interface 116 using New Radio (NR).

[0041] 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 (for example, a eNB and a gNB).

[0042] 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.

[0043] The base station 114b in FIG. 1A 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 (for example, 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 (for example, WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR etc.) to establish a picocell orfemtocell. 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.

[0044] 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.

[0045] 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.

[0046] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system

100 may include multi-mode capabilities (for example, the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with 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.

[0047] FIG. 1B is a system diagram illustrating an example WTRU 102. As shown in FIG.

1B, 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 subcombination of the foregoing elements while remaining consistent with an embodiment.

[0048] 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. 1B 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.

[0049] The transmit/receive element 122 may be configured to transmit signals to, or receive signals from, a base station (for example, 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. [0050] Although the transmit/receive element 122 is depicted in FIG. 1B as a single element, the WTRU 102 may include any number of transmit/receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit/receive elements 122 (for example, multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0051] 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.

[0052] 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/touchpad 128 (for example, 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).

[0053] 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 (for example, nickel-cadmium (NiCd), nickel- zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0054] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (for example, 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 (for example, 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.

[0055] 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.

[0056] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (for example, associated with particular subframes for both the UL (for example, for transmission) and downlink (for example, for reception) may be concurrent and/or simultaneous. The full duplex radio may include an interference management unit 139 to reduce and or substantially eliminate self-interference via either hardware (for example, a choke) or signal processing via a processor (for example, a separate processor (not shown) or via processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (for example, associated with particular subframes for either the UL (for example, for transmission) or the downlink (for example, for reception)).

[0057] FIG. 1C 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 116. The RAN 104 may also be in communication with the CN 106.

[0058] 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 116. 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. [0059] 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. 1C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0060] The CN 106 shown in FIG. 1C 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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 (for example, 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.

[0065] Although the WTRU is described in FIGS. 1A-1D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (for example, temporarily or permanently) wired communication interfaces with the communication network. [0066] In representative embodiments, the other network 112 may be a WLAN.

[0067] 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 (for example, directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11 e DLS or an 802.11 z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (for example, 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.

[0068] 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 (for example, 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 (for example, 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 (for example, only one station) may transmit at any given time in a given BSS.

[0069] 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.

[0070] Very High Throughput (VHT) STAs may support 20 MHz, 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 MFIz 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).

[0071] Sub 1 GHz modes of operation are supported by 802.11 af and 802.11ah. The channel operating bandwidths, and carriers, are reduced in 802.11 af and 802.11 ah relative to those used in 802.11h, and 802.11 ac. 802.11 af supports 5 MFIz, 10 MFIz and 20 MFIz bandwidths in the TV White Space (TVWS) spectrum, and 802.11 ah supports 1 MFIz, 2 MFIz, 4 MFIz, 8 MFIz, and 16 MFIz 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 (for example, only support for) certain and/or limited bandwidths. The MTC devices may include a battery with a battery life above a threshold (for example, to maintain a very long battery life).

[0072] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802.11h, 802.11ac, 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 ST As 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 802.11 ah, the primary channel may be 1 MFIz wide for STAs (for example, MTC type devices) that support (for example, only support) a 1 MFIz mode, even if the AP, and other STAs in the BSS support 2 MFIz, 4 MFIz, 8 MFIz, 16 MFIz, 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 MFIz 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.

[0073] In the United States, the available frequency bands, which may be used by

802.11ah, are from 902 MFIz to 928 MFIz. In Korea, the available frequency bands are from 917.5 MFIz to 923.5 MFIz. In Japan, the available frequency bands are from 916.5 MFIz to 927.5 MFIz. The total bandwidth available for 802.11 ah is 6 MFIz to 26 MFIz depending on the country code. [0074] FIG. 1 D is a system diagram illustrating the RAN 113 and the CN 115 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.

[0075] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 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).

[0076] 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 (for example, containing varying number of OFDM symbols and/or lasting varying lengths of absolute time).

[0077] 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 (for example, 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.

[0078] 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. 1D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0079] The CN 115 shown in FIG. 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While each of the foregoing elements are depicted as part of the CN 115, it will be appreciated that any of these elements may be owned and/or operated by an entity other than the CN operator.

[0080] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b,

180c in the RAN 113 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 (for example, 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 AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and/or non-3GPP access technologies such as WiFi.

[0081] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 115 via an N11 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.

[0082] 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 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multihomed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, and the like.

[0083] The CN 115 may facilitate communications with other networks. For example, the

CN 115 may include, or may communicate with, an IP gateway (for example, an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, 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.

[0084] In view of Figures 1A-1D, and the corresponding description of Figures 1A-1D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-ab, 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.

[0085] 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. [0086] 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 (for example, 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 (for example, which may include one or more antennas) may be used by the emulation devices to transmit and/or receive data.

[0087] A broad classification of the use cases for emerging 5G systems may be depicted as Enhanced Mobile Broadband (eMBB), Massive Machine Type Communications (mMTC) and Ultra Reliable and Low Latency Communications (URLLC), based on the general requirements set out by the International Telecommunication Union-Radio Communication Sector (ITU-R), the Next Generation Mobile Networks (NGMN) and the 3^rd Generation Partnership Project (3GPP). Different use cases may focus on different requirements such as higher data rate, higher spectrum efficiency, low power and higher energy efficiency, lower latency and higher reliability. A wide range of spectrum bands ranging from 700 megahertz (MHz) to 80 gigahertz (GHz) may be considered for a variety of deployment scenarios.

[0088] As a carrier frequency increases, the severe path loss can become a crucial limitation to guarantee a sufficient coverage area. Transmission in millimetre wave systems could additionally suffer from non-line-of-sight losses, for example, diffraction loss, penetration loss, oxygen absorption loss, foliage loss, etc. During initial access, a base station and a WTRU may need to overcome these high path losses and discover each other. Utilizing dozens or even hundreds of antenna elements to generated beam formed signal may provide effective way to compensate for the severe path loss by providing significant beam forming gain. Beamforming techniques may include digital, analogue and hybrid beamforming.

[0089] Cell search may be a procedure by which a WTRU, such as, for example, one or more of the WTRUs of Figs. 1A-1D, acquires time and frequency synchronization with a cell and detects the Cell ID of that cell. LTE synchronization signals may be transmitted in the 0th and 5th subframes of every radio frame and are used for time and frequency synchronization during initialization. As part of the system acquisition process, a WTRU synchronizes sequentially to the orthogonal frequency division multiplexing (OFDM) symbol, slot, subframe, half-frame, and radio frame based on the synchronization signals. The two synchronization signals are Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS). PSS may be used to obtain slot, subframe and half-frame boundary. It may also provide physical layer cell identity (PCI) within the cell identity group. SSS may be used to obtain the radio frame boundary. It may also enables the WTRU to determine the cell identity group, which may range from 0 to 167.

[0090] Following a successful synchronization and PCI acquisition, the WTRU may decode the Physical Broadcast Channel (PBCH) with the help of one or more cell-specific reference signals (CRSs) and acquire the master information block (MIB) information regarding system bandwidth, System Frame Number (SFN) and physical hybrid automatic repeat request (ARQ) indicator channel (PHICH) configuration. In an example, the one or more CRSs may be used for channel estimation purposes.

[0091] One having ordinary skill in the art will understand that the LTE synchronization signals and PBCH may be transmitted continuously according to the standardized periodicity. For example, one or more of the PSS and SSS may be transmitted continuously.

[0092] Paging, such as LTE paging, may be used for network-initiated connection setup when the terminal is in RRCJDLE mode. In LTE, the same mechanism as for downlink data transmission on the downlink shared channel (DL-SCH) may be used and the mobile terminal monitors the L1/L2 control signaling for downlink scheduling assignments related to paging. Since the location of the terminal typically is not known on a cell level, the paging message is typically transmitted across multiple cells in the so-called tracking area.

[0093] An efficient paging procedure should allow the terminal to sleep with no receiver processing most of the time and to briefly wake up at predefined time intervals to monitor paging information from the network. Therefore, a paging cycle may be defined, allowing the terminal to sleep most of the time and only briefly wake up to monitor the L1/L2 control signaling. If the terminal detects a group identity used for paging, such as using scrambling of the cyclic redundancy check (CRC) of the downlink control information (DCI) using a paging-radio network temporary identifier (P-RNTI), which represents a paging indication, when it wakes up, it may process the corresponding downlink paging message transmitted on the paging channel PCH. The paging message may include the identity of the terminal(s) being paged, and a terminal not finding its identity will discard the received information and sleep according to the discontinuous reception (DRX) cycle.

[0094] The network may configure subframes for which a terminal should wake up and listen for paging. The configuration may be cell specific, although there is a possibility to complement the setting by terminal-specific configuration. Which frame a given terminal should wake up and search for the P-RNTI on a physical downlink control channel (PDCCH) may be determined by an equation that includes, as an input, the identity of the terminal as well as a cell- specific and, optionally, a terminal specific paging cycle. The paging cycle for a terminal may range from once per 256 frames up to once per 32 frames. The subframe within a frame to monitor for paging is also derived from the international mobile subscriber identity (IMSI), which may be linked to a subscription. Since different terminals have different IMSIs, they will compute different paging instances. Hence, from a network perspective, paging may be transmitted more often than once per 32 frames, although not all terminals can be paged at all paging occasions as they are distributed across the possible paging instances

[0095] Paging messages may only be transmitted in some subframes, ranging from one subframe per 32 frames up to a very high paging capacity with paging in four subframes in every frame. From a network perspective, the cost of a short paging cycle may be minimal as resources not used for paging can be used for normal data transmission and are not wasted. However, from a terminal perspective, a short paging cycle may increase the power consumption, as the terminal needs to wake up frequently to monitor the paging instances.

[0096] In addition to initiating connection to terminals being in RRCJDLE mode, paging may also be used to inform terminals in RRCJDLE mode as well as RRC_CONNECTED mode about changes of system information or about an emergency.

[0097] In unlicensed bands, a gNB or a WTRU may need to perform a listen-before-talk

(LBT) procedure before accessing the unlicensed wireless channel. Depending on the regulatory requirements of the unlicensed channel, the LBT specifics may be different. In general, an LBT procedure may consist of a fixed- and/or random-duration interval where a wireless node (for example a gNB or a WTRU) listens to a medium and if the energy level detected from the medium is more than a threshold, that is specified by the regulator, the gNB or WTRU may refrain from transmitting any wireless signal; otherwise the wireless node may transmit its desired signal after completion of the LBT procedure.

[0098] In some regulatory regimes, LBT procedures may be mandatory for unlicensed channel usage, and as a consequence the various LBT categories were adopted in 3GPP licensed- assisted access (LAA) (Release 13), enhanced licensed-assisted access (eLAA) (Release 14) and further enhancements to licensed-assisted access (feLAA) (Release 15). The LBT Category 4 (CAT 4) scheme, adopted in LAA/eLAA, has been identified as the preferred scheme for most use cases. The LBT CAT 4 procedure starts when an eNB or gNB, and in some cases a WTRU, wants to transmit control or data in an unlicensed channel. The device then conducts an initial clear channel assessment (CCA), where the device checks if the channel is idle for a period of time (that is a sum of a fixed period of time and a pseudo-random duration). The availability of the channel is determined by comparing the level of energy detected (ED) across the bandwidth of the unlicensed channel to an energy threshold that is determined by the regulator. [0099] If the channel is determined to be free, the transmission can proceed. If not, the device may conduct a slotted random back-off procedure, where a random number is selected from a specified interval called the contention window. A back-off countdown is obtained and the channel is verified as idle or not, and the transmission is initiated when the back-off counter goes to zero. After the eNB or gNB has gained access to the channel, it may only be allowed to transmit for a limited duration referred to as the maximum channel occupancy time (MCOT). The CAT 4 LBT procedure with random backoff and variable contention window sizes may be considered to enable fair channel access and good coexistence with other RATs, such as Wi-Fi and other LAA networks.

[0100] In licensed assisted non-standalone access, an unlicensed band operation could rely on the assistance of a primary component carrier in licensed band. In new radio-unlicensed band (NR-U) standalone operation, all functionalities and features should be fulfilled on unlicensed bands including initial access. Initial access may be essential for standalone operation. Due to spectrum characteristics and regulatory requirements, for example, uncertainty of channel availability, the Occupied Channel Bandwidth (OCB) requirement, and the like, designs to enable initial access in an licensed band to be compatible with unlicensed band operation are disclosed herein. In some unlicensed bands (for example, 5 GHz), there may be transmission power spectral density (PSD) limitations. Power boosting of one or more synchronization signals may not be possible in unlicensed bands because of such PSD limitations and may result in reduced synchronization performance.

[0101] For a synchronization signal and New Radio-Physical Broadcast Channel (NR-

PBCH), synchronization signal (SS) blocks are present consecutively per SS burst set for NR licensed band operation. The maximum transmission bandwidths of SS blocks may be 5, 10, 40 and 80 MHz with corresponding 15, 30, 120 and 240 kilohertz (kHz) subcarrier spacing. Due to LBT failure, the SS block locations within a slot may not be optimum for NR unlicensed band operation which may result in performance degradation of SS block detection. Uncertainty of channel availability may also have impact on the SS burst configuration such as the periodicity and time- window size of an SS burst set. In addition, the OCB requirement is not considered for transmission bandwidth of SS blocks, which may be required for NR-U. SS blocks to fulfil LBT and OCB requirements are considered herein for NR-U.

[0102] For paging, a paging cycle may be defined to allow WTRUs to monitor paging messages at predefined times. For paging message transmission on unlicensed bands, the uncertainty of channel availability could cause the failure of a paging DCI or paging message. As a result, WTRUs may not receive the corresponding paging message. Paging occasion could also be blocked due to LBT failure. Enhancements for paging needed for NR-U and studied during NR-U SI are disclosed herein.

[0103] A discovery reference signal (DRS) may need to be integrated with beam-based

NR-U. For systems with a high number of beams, efficient design may be needed. If transmitted without a PDCCH or physical downlink shared channel (PDSCH), a DRS may occupy very small bandwidth. Other devices may sense the medium, may find a spectrum width to be empty and may transmit. This may result in failed DRS transmissions. For a large number of beams, such as in the over 6 GHz spectrum use case, a total DRS measurement timing configuration (DMTC) duration may be prohibitively large. A listen before each DRS beam may be used. Flowever, if there is interference, DRS for a specific beam may be skipped. This may introduce added delays.

[0104] According to an example of the disclosed subject matter, solutions of multi-stage

SS/PBCH transmission based on synchronization signal block (SSB) and SSB group (SSBG) are disclosed herein for NR-U. In NR-U, SS/PBCH transmission may be based on an SSBG and SSB structure. As an example, there may be M SSBGs and each SSBG may have N SSBs. For example, M may be eight and N may be eight. For K actual SSB transmissions, M1 SSBGs and N1 SSBs per SSBG may be used. In order to reduce impact due to LBT, such M1 SSBGs may be transmitted consecutively. For each LBT, M1 consecutive SSBGs may be transmitted to cover K SSBs. To maintain the same SSB pattern for each SSBG, N1 consecutive SSBs per SSBG may be transmitted. In order to avoid gap between SSB and reduce the waste of resource, full SSB per SSBG may be used. For example, N1 may be N, for example, N1 may be eight.

[0105] As an example, L may be the maximum number of SSBs in total per SS burst set

(SSBS). L may be 64. If K is large, for example K is close to or equal to L, then a multi-stage approach may also include SSBS in transmission structure.

[0106] Multi-stage SSBS/SSBG/SSB transmission and channel access may include an

SSBS stage, an SSBG stage, and an SSB stage. LBT may be integrated with a multi-stage structure. For example, multi-stage LBT based on SSBS/SSBG/SSB may be as follows. Stage 1 may include no LBT at the SSB level, in an example. In another example, Stage 1 may include a very fast very short duration LBT at the SSB level. Stage 2 may include Fast LBT for an SSBG. Stage 3 may include Long LBT for an SSBS.

[0107] In an example, if channel occupancy time (COT) is less than a predetermined duration (T1), then LBT may not be performed or very fast LBT (for example, very short LBT duration) may be performed for SS/PBCH transmission. If COT is more than a predetermined duration (T1) but less than a second predetermined duration (T2), then fast LBT may be performed for SS/PBCH transmission. Otherwise if COT is more than the second predetermined duration (T2), then regular or long LBT may be performed for SS/PBCH transmission.

[0108] Multi-stage beam(s) based on SSBS/SSBG/SSB may be implemented using different beamwidths such as widebeam, medium beam and narrow beam. For example, widebeam may be implemented for SSBS, medium beam may be implemented for SSBG and narrow beam may be implemented for SSB.

[0109] A channel access indicator (CAI) may be used in examples. In an example, a Q-bit

CAI may be used in NR-U. For example, a Q=2, two-bit channel access indicator may be used in NR-U such that a CAI for SS/PBCH may be designated by 00 used for SSBS, 01 used for SSBG, 10 used for SSB and 11 used for reserved uses. CAIs may be included in one or more of PSS, SSS, NR-PBCH, remaining minimum system information (RMSI) or the like. For example, if 00 is indicated, a WTRU should expect to receive an SSBS and if 01 is indicated, a WTRU should expect to receive an SSBG. Further, if 10 is indicated, a WTRU should expect to receive an SSB and if 11 is indicated, a WTRU may discard the indicator, use the indicator for another purpose or reserve the indicator for a potential future use.

[0110] Figure 2 is a diagram illustrating an example CAI, an SSBG indicator and an SSB indicator. As shown in Figure 2, a WTRU may receive a CAI 220, an SSBG indicator 230 and an SSB indicator 240. In an example, a WTRU may receive an indication of an SSBG 230 and an SSB 240 for actual SSB transmission, for example, in a RMSI.

[0111] Figure 3 is a diagram illustrating an example CAI with savings on an SSBG indicator and an SSB indicator. In an example, in combination with a CAI 320, if 00 is indicated, a WTRU may expect to receive an SSBS. The WTRU may discard an indication of SSBG 330 and an indication of SSB 340 for actual SSB transmission. In an example, 16 bits may accordingly be freed up to reduce overhead or may be reused for other purposes for efficient bit utilization.

[0112] Figure 4 is a diagram illustrating an example CAI and SSBG indicator with savings on an SSB indicator. In an example, if 01 is indicated, a WTRU should expect to receive an SSBG. The WTRU may utilize an indication of SSBG-only 420 for actual SSB transmission. In an example, 8 bits may be freed up to reduce overhead or may be reused for other purposes for efficient bit utilization. Savings on SSB indicator 440 may thus be realized.

[0113] In a further example, if 10 is indicated, a WTRU may expect to receive an SSB. The

WTRU may utilize indication of joint SSBG and SSB for actual SSB transmission. Accordingly, 0 bits may be freed up to reduce overhead or may be reused for other purposes for efficient bit utilization. In a further example, if 11 is indicated, a WTRU may discard the indicator. [0114] According to examples provided herein, hierarchical LBT-based SS/PBCH Block and SSB Group Indication techniques are used. CAI and WTRU procedures may be provided such that if 00 is indicated, a WTRU should expect to receive an SSBS, which may involve a long LBT procedure. In a further example, if 01 is indicated, a WTRU should expect to receive an SSBG which may involve a fast LBT procedure. Also, if 10 is indicated in an example, a WTRU should expect to receive an SSB and each SSB may involve its own LBT procedure. In another example, if 10 is indicated, a WTRU should expect to receive an SSB which may involve no LBT procedure. Moreover, if 11 is indicated in an example, a WTRU may discard the indicator.

[0115] In the“00” case, a gNB may perform a single widebeam LBT procedure, or multiple directional LBT procedures, for all SSBGs/SSBs in an SSBS. If the gNB succeeds in obtaining channel(s) or spectrum based on the LBT procedure, an entire SSBS may be transmitted without interruption by a further LBT procedure.“00” may be indicated to a WTRU for reception of an entire SSBS. Accordingly, regular, for example, non-LBT-based, SSBG and SSB may indicated for actually transmitted SSBs. In an example, this case may be referred to as a long LBT.

[0116] In the“01” case, a gNB may perform a widebeam LBT procedure, or multiple directional LBT procedure, for an SSBS. If the LBT procedure fails, an entire SSBS may not be transmitted without interruption by a further LBT procedure. Accordingly, gNBs may further perform a separate widebeam LBT procedure, or multiple directional LBT procedures, for each of the SSBGs in the SSBS. Only SSBGs that succeed the LBT procedure be transmitted. Accordingly, in an example, if the gNB succeeds in obtaining channel(s) or spectrum based on the LBT procedure for an SSBG, the gNB may then transmit the SSBG. A gNB may indicate a“01” to a WTRU for SSBG reception. In an example, SSBG and SSB may be indicated for LBT-procedure-based actually transmitted SSBGs and non-LBT-procedure-based actually transmitted SSBs respectively, in which LBT may be taken into account for actually transmitted SSBGs. In an example, this case may be referred to as a fast LBT.

[0117] In the“10” case, a gNB may perform widebeam LBT procedure, or multiple directional LBT procedures, for SSBS. If the LBT procedure fails, the gNB may further perform a widebeam LBT procedure, or multiple directional LBT procedures, for SSBGs in SSBS. Only SSBGs that succeeds the LBT procedure may be transmitted, in which case, all SSBs in that SSBG may be transmitted. However, for an SSBG that fails the LBT procedure, the gNB may further perform LBT procedures for SSBs in the failed SSBG. In this case, some SSBs that succeed the LBT procedure in that SSBG may be transmitted and other SSBs that the fail LBT procedure may not be transmitted.“10” may be indicated to WTRU for LBT-based SSBG reception and LBT-based SSB reception. SSBG and SSB may be indicated for LBT-procedure-based actual transmitted SSBGs and LBT-procedure-based actual transmitted SSBs in which LBT is taken into account for both actual transmitted SSBG and SSB. In an example, this case may be referred to as an each SSB LBT.

[0118] In another example in the“10” case, a gNB may transmit an SSB with no LBT procedure related to the SSB. The gNB may indicate to a WTRU that no LBT procedure is being performed.

[0119] In the“11” case, a gNB may perform widebeam LBT (or multiple directional LBT) for all SSBGs/SSBs in SSBS. If it fails, entire SSBS may not be transmitted at all.

[0120] In an example, a shift indicator may be, for example, an N-bit indicator to indicate

64 shifts, an N1-bit indicator to indicate 8 shifts, or the like, as applicable. The shift may indicate a time location for a transmission in the time domain and may be expressed in certain time units. In an example, a shift may be referred to as a time shift. The shift or time shift may indicate in which slot an SSB may be transmitted. In another example, the shift or time shift may indicate in which OFDM symbol, which SSB candidate location, which mini-slot or which non-slot an SSB may be transmitted. The level of granularity of the shift or time shift may be at the level of OFDM symbols, groups of OFDM symbols or M-OFDM symbols, where M>0 and may be predefined, configurable or indicated, SSBs, groups of SSBs or M-SSBs, where M>0 and may be predefined, configurable or indicated, slots, groups of slots or M-slots, where M>0 and may be predefined, configurable or indicated, SS bursts, SS burst sets, DRS durations, or the like. In an example, the transmissions may be downlink transmissions. In another example, the transmissions may be uplink transmissions. In a further example, the transmissions may be sidelink transmissions, for example, sidelink-SSB (S-SSB) transmissions, for example, for V2X. In addition, the S-SSB transmissions may be used for licensed and/or unlicensed band communications. This method may also be applied to other signal and/or channel transmissions. A shift indicator or time shift indicator may be received in an SS, a PBCH or both. In another example, the shift may indicate a combination of the time units provided above. For example, the shift may indicate a combination of in which slot and which OFDM symbol an SSB may be transmitted.

[0121] According to an example, in order to indicate the actually transmitted SS blocks due to LBT, another indicator for actually transmitted SS blocks for LBT may be used. An SS block indicator, an SSB group indicator or both may be used. For example, an 8-bit SS block indicator and an 8-bit SSB group indicator may be used for LBT. Such indicators may be more dynamic than original indicators since by nature, channel availability may be dynamic due to LBT. A WTRU may receive either or both of two sets of indicators: a set with an original SS block indicator and an SSBG indicator, or a set with an LBT based SS block indicator and an LBT based SSBG indicator. [0122] Figure 5 is diagram illustrating an example updated SSB and SSBG using dynamic

LBT-based SSB and SSBG indication. The original SS block indicator 530 and the SSBG indicator 520 may be semi-static and may be carried in an RMSI, radio resource control (RRC) signaling or the like. The LBT based SS block indicator 550 and the LBT based SSBG indicator 540 may be dynamic and may be carried by an L1/2 control channel, such as a PDCCH, group common- physical downlink control channel (GC-PDCCH) or MAC control information, by a MAC control element (CE) or by the like. The LBT based SS block indicator 550 and SSBG indicator 540 may also be semi-static but with different periodicities as compared with the original SS block indicator 530 and SSBG indicator 520.

[0123] The LBT based SS block indicator 550 and SSBG indicator 540 may override the original SS block indicator 530 and SSBG indicator 520. In an example, a Ί” may indicate that an SS block or SSBG is actually transmitted and“0” may indicate that the SS block or SSBG is not actually transmitted in the original SS block indicator 530 and SSBG indicator 520. Similarly, Ί” may indicate that the SS block or SSBG is actually transmitted and“0” may indicate that the SS block or SSBG is not actually transmitted in the LBT based SS block indicator 550 and SSBG indicator 540. When a WTRU receive both sets of indicators, original and LBT-based, a WTRU may apply an AND operation to derive the final set of actually transmitted and updated SS blocks 570 and SSBGs 560.

[0124] Figure 6 is a diagram illustrating an example of procedures for channel access with

SSB, SSBG and SSBS. A WTRU may receive the first set of SSB and SSBG indications 620. The first set of SSB and SSBG indications may use semi-static signaling. The WTRU may then update SSBs and SSBGs according to the first set of SSB and SSBG indications 630. For example, the WTRU may update the list of SSBs and SSBGs for the purposes of detection and monitoring at the WTRU. WTRU may receive the second set of SSB and SSBG indications 640. The second set of SSB and SSBG indications may be used for one or more LBT procedures and the indications may use dynamic signaling. The WTRU may then further update SSBs and SSBGs based on the second set of SSB and SSBG indication 650. Further, the WTRU may use the latest updated SSBs and SSBGs for monitoring and measurement accordingly 660.

[0125] Figure 7A is a diagram illustrating an example of LBT for channel access with SSB,

SSBG and SSBS. In an example shown in Figure 7A, a hierarchical multi-stage LBT procedure and SSB transmit/receive indication for NR-U is provided. For example, a long LBT procedure may be undertaken. If the long LBT procedure is successful, all the SSBs from slot 702 through slot 708 may be transmitted without the need for another LBT procedure during the SSB sweep stage. Accordingly, there will be no breaks for a further LBT procedure during the SSB sweep stage. In another example shown in Figure 7A, a fast LBT procedure may be undertaken. If the fast LBT procedure is successful, all the SSBs from slot 706 through slot 708 may be transmitted without the need for another LBT procedure during the SSB group stage. Accordingly, there will be no breaks for a further LBT procedure during the SSB group stage. Further, an SSB indicator may indicate which SSB groups may be transmitted. In a further example, a fast LBT procedure may be undertaken and if the fast LBT procedure is successful, all the SSBs from slot 702 through slot 704 may be transmitted without the need for another LBT procedure for that SSB group.

[0126] In a further example not shown in Figure 7A, an LBT procedure may be undertaken for each LBT. For all the SSBs from slot 704 through slot 708, an SSB may be transmitted if the LBT procedure for that SSB was successful. Accordingly, there may be one LBT procedure per SSB. Further, an SSB indicator may indicate which SSBs may be transmitted.

[0127] Figure 7B is a diagram illustrating another example of LBT for channel access with

SSB, SSBG and SSBS. In an example shown in Figure 7B, a hierarchical multi-stage LBT procedure and SSB transmit/receive indication for NR-U is provided. A time shift 710 may be indicated to the WTRU, as described elsewhere herein. In an example, a long LBT procedure may be undertaken. If the long LBT procedure is successful, all the SSBs from slot 720 through slot 770 may be transmitted without the need for another LBT procedure during the SSB sweep stage. Accordingly, there will be no breaks for a further LBT procedure during the SSB sweep stage, as indicated by time period 792. In another example shown in Figure 7B, a fast LBT procedure may be undertaken. If the fast LBT procedure is successful, all the SSBs from slot 720 through slot 740 may be transmitted without the need for another LBT procedure during the SSB group transmission, as indicated by time period 794. Further, all the SSBs from slot 750 through slot 770 may be transmitted without the need for another LBT procedure during the SSB group transmission, as indicated by time period 796. Accordingly, there will be no breaks for a further LBT procedure during the SSB group transmission. Further, an SSB indicator may indicate which SSB groups may be transmitted.

[0128] In a further example shown in Figure 7B, an LBT procedure may be undertaken for each LBT. For all the SSBs from slot 720 through slot 770, an SSB may be transmitted if the LBT procedure for that SSB was successful. Accordingly, there may be one LBT procedure per SSB during time period 798. Further, an SSB indicator may indicate which SSBs may be transmitted [0129] Figure 8 is a diagram illustrating an example of LBT for channel accessing using a joint SSB index and a time shift. In an example shown in Figure 8, a WTRU may detect an SS/PBCH block 810. The WTRU may then obtain one or more indications regarding a joint SSB index and a time shift from the detected SS/PBCH block 820. In an example, one or more indications may be obtained from an SS in the detected SS/PBCH block. In another example, one or more indications may be obtained from a PBCH in the detected SS/PBCH block. Further, the WTRU may derive at least one of frame timing information, slot timing information and symbol timing information based on the obtained joint SSB index and time shift 830. Also, the WTRU may obtain timing information for detection of a CAI, an SSB indication or both 840. On a condition that the WTRU then successfully detects one or both of the CAI and the SSB indication 850, the WTRU may derive time locations of SSBs based on the detected one or both of the CAI and the SSB indication 870. Accordingly, the WTRU may perform SSB measurements for actually transmitted SSBs 880. On a condition that the WTRU does not successfully detect at least one of the CAI and the SSB indication 850, the WTRU may search for and measure all SSBs 860 during an SSB sweep. For example, the WTRU may search all SSB time locations during the SSB sweep. The WTRU may also measure all SSBs received during the SSB sweep.

[0130] In a further example, the CAI may have a state of one LBT procedure for all SSB transmissions during an SSB sweep. In another example, the CAI may have a state of one LBT procedure per SSBG. Moreover, there may be a break between SSBGs. In an additional example, the CAI may have a state of one LBT procedure per SSB. Further, the gNB may perform a widebeam LBT procedure for SSBGs in an SSBS. The gNB may indicate the performance of this procedure to the WTRU.

[0131] According to an example in the disclosed subject matter, flexible COT-based

SS/PBCH transmission is disclosed herein. An network may perform an LBT procedure before SSB transmission. A COT may be based on an SSBG to facilitate the SSB indication. The network may perform an LBT procedure before each SSBG transmission. A WTRU may be provided with an SSBG indication for SSBG transmission. A WTRU may use an SSBG indication for at least one of power saving, rate matching and mobility measurement. The SSBG-based LBT procedure may enable low latency SSB acquisition at the cost of additional resources. To have more flexible SS/PBCH transmission, a COT-based SS/PBCH transmission may be used.

[0132] Further, the network may refine the SSB transmission by an LBT procedure before each SSB transmission. A WTRU may be provided with an SSB indication within each SSBG. If an LBT procedure for each SSBG shows a channel is available, the network may perform an LBT procedure for each SSB within an SSBG.

[0133] In an example, if an LBT procedure for each SSBG shows a channel is not available, the network may skip the LBT procedure for each SSB within an SSBG and disable this SSBG in using an indicator. In another approach, the network may continue the LBT procedure for each SSB within the SSBG and enable or disable this SSB with group in indicator. [0134] If an MCOT can support SSBG or SS burst set, then a COT may be used to cover a whole duration of an SSBG or an SS burst set. Further, an COT may be used to cover a partial duration of an SSBG or an SS burst set.

[0135] Since LBT may have impact on actual SSB transmission, under the constraint of actual SSB indication, solutions may be used such as follows. A first solution may include new channel access method and procedure for SSB transmission in NR-U, and may be introduced to meet the NR actual SSB transmission requirements and constraints. A second solution may include actual SSB transmission requirements and constraints, and may be modified or enhanced in NR-U. One or both of the first solution and the second solution may be used.

[0136] In another example, RAT location profile based SS/PBCH transmission is provided herein. To transmit SS/PBCH more efficiently, obtaining certain information of devices of other RAT(s) may be used. Such information may include but not be limited to, device location, device direction, device beam location, and device beam direction.

[0137] An LBT procedure may be used to obtain some or all of the information above. For example, an LBT procedure may be performed to detect the energy or to detect the signature of the devices of other RATs. Other RATs may include for example, WiFi.

[0138] In a first solution, the gNB may perform an LBT procedure, obtain the profile, and use the profile for SSB indication. In examples where the LBT procedure is a directional LBT procedure, the LBT procedure may provide beam-location profile(s) of other RAT(s), for example, WiFi.

[0139] In an example, different LBT methods may be used alone or in combination. In a first LBT method, only SSBG level LBT succeeds, and then the network may perform SSB level LBT. Otherwise the network may skip this SSBG. This may be compatible with NR. This may cause some waste of resources due to skipping some SSBGs. Accordingly, some SSBGs may fail the LBT procedure but individual SSBs within the failed SSBG may still succeed the LBT procedure.

[0140] In a second method, even an SSBG level fails the LBT procedure, and then the network may perform an SSB level LBT procedure. If more than X SSBs succeed the LBT procedure, the network may turn on this SSBG. Otherwise the network may skip this SSBG. This may be compatible with NR. More LBT procedures may be required to be performed. Accordingly, an SSBG may fail the LBT procedure but individual SSBs within the failed SSBG may still succeed the LBT procedure. The parameter X may be predetermined, configured or indicated. The parameter X may also be derived from other conditions.

[0141] In a third method, if SSBG level succeeds the LBT, then the network may configure an SSB pattern to perform an SSB level LBT procedure. Otherwise, the network may skip this SSBG. This may be compatible with NR. Accordingly, more LBT procedures may be required to be performed.

[0142] Initial LBT for SSBG may be used to determine or preset the SSB pattern within an

SSBG for the following Y SSBGs within COT. The parameter Y may be predetermined, configured or indicated. The parameter Y may also be derived from other conditions.

[0143] According to an example of the disclosed subject matter, an SSB indication in NR-U is disclosed herein. Two types of SSB indications may be introduced for NR-U: Intended SSB locations and Actual SSB locations.

[0144] Intended SSB locations may be the time locations where SSBs intended to be transmitted. Actual SSB locations are the time locations where SSBs are actually transmitted. In NR, Intended SSB locations are the same as actual SSB locations. In NR-U, due to LBT, actual SSB locations are usually less then intended SSB locations. Indication for intended SSB locations and actual SSB locations may be carried in RMSI.

[0145] RMSI may use an entire candidate SSB, instead of an actual SSB, for rate matching. Further, since typically a WTRU has not yet received an SSB indication in RMSI, it may not use the indication to preform rate matching. However, other DL channels, such as other system information (OSI), paging, random access channel (RACH) Msg2&4, PDSCH, and the like, can rate match based on an actual SSB. Subsequent RMSI can also rate match based on a previous actual SSB indication.

[0146] WTRU procedures in NR may be defined such that if a WTRU receives an actual

SSB indication in RMSI, the WTRU may perform rate matching based on an actual SSB indication. Further, if the WTRU does not receive an actual SSB indication in RMSI, the WTRU may perform rate matching based on entire SSB(s).

[0147] WTRU procedures in NR-U may be defined such that if the WTRU receives an intended SSB indication in RMSI, the WTRU may perform rate matching based on an intended SSB indication. Further, if the WTRU receives an actual SSB indication in a signal and/or channel, performance of rate matching may occur based on the actual SSB indication. An actual SSB may be based on an LBT procedure. Further, the actual SSB indication may override the intended SSB. The actual SSB indication may include information regarding how to send actual SSB(s) in NR-U. Further, the actual SSB may include example cases for a moved SSB and a skipped SSB.

[0148] In an example, if a WTRU does not receive an intended SSB or actual SSB indication in RMSI, then perform rate matching may occur based on entire SSB(s).

[0149] WTRU procedures in NR and NR-U may be defined such that if DL channels and

SSB collide or overlap, a WTRU may perform procedures, which may be NR-U procedures, if configured for NR-U. If a WTRU receives intended an SSB indication in RMSI, the WTRU may perform rate matching based on the intended SSB indication. If the WTRU receives an actual SSB indication in a signal and/or channel, the WTRU may perform rate matching based on actual SSB indication. An actual SSB may be based on an LBT procedure. Further, the actual SSB indication may override the intended SSB. The actual SSB indication may include information regarding how to send actual SSB(s) in NR-U. Further, the actual SSB may include example cases for a moved SSB and a skipped SSB. If WTRU does not receive intended SSB or actual SSB indication in RMSI, rate matching may be performed based on entire SSB(s).

[0150] Figure 9 is a diagram illustrating an example RMSI with a partial collision with an

SSBS. In an example shown in Figure 9, if DL channels and SSB collide or overlap, a WTRU procedure may be performed if configured for NR. The WTRU procedure may be an NR procedure. If a WTRU receives an actual SSB indication in RMSI 930, the WTRU may perform rate matching in SSBS 940 based on the actual SSB indication. Further, if the WTRU does not receive actual SSB indication in RMSI 930, rate matching may be performed based on entire SSBs, such as SSB 940.

[0151] Figure 10 is a diagram illustrating an example RMSI with a full collision with an

SSBS. If DL channels and SSB do not collide or overlap, a WTRU procedure may be performed if configured for NR-U. A WTRU may perform rate matching which may be based on intended SSBs if an indication of actual SSB is received. Further, the WTRU may perform rate matching which may be based on actual SSBs if indication of actual SSB is received. Accordingly, an indication of actual SSB override and indication of intended SSB may be received. For example, indications may be received in RMSIs 1030, 1050 and rate matching may be performed accordingly for SSBSs 1040, 1060.

[0152] If DL channels and SSB do not collide or overlap, a WTRU procedure may be performed if configured for NR such that WTRU does not perform rate matching on SSBs. Further, the WTRU may discard an indication of an actual SSB that is received.

[0153] Figure 11 is a diagram illustrating an example LBT, RMSI and SSBS where the

SSBS follows the RMSI. In an example shown in Figure 11, LBT 1120 may be performed before RMSI transmission 1130, which may be followed by SSBS transmission 1140. LBT 1120 may be used to determine the actual SSB transmission within an SSBS 1140. LBT 1120 may be used to determine the RMSI transmission 1130, which may indicate the actual SSB transmission within the SSBS 1140 to WTRUs.

[0154] Figure 12 is a diagram illustrating an example LBT, RMSI and SSBS where the

SSBS may not follow the RMSI. In an example shown in Figure 12, LBT 1220, 1250 may be performed before RMSI transmission 1230, 1260, which may be followed by SSBS transmission 1270 or may not be followed by SSBS transmission 1240. LBT 1250 may be used to determine the actual SSB transmission within SSBS 1270. LBT 1220, 1250 may be used to determine the RMSI transmission 1230, 1260, which may indicate the actual SSB transmission within the SSBS 1270 that immediately follows RMSI transmission 1260.

[0155] In an example, different periodicities and/or time offsets may be applied to SSBSs and RMSIs. An RMSI may or may not have an offset with respective to an SSBS.

[0156] Figure 13 is a diagram illustrating an example RMSI which has a larger periodicity than an SSBS. In an example shown in Figure 13, when an SSBS 1320, 1325, 1340, 1345, 1360, 1365, 1380, 1385 has smaller periodicity than RMS1 1310, 1330, 1350. 1370, a change of an actual SSB transmission may not be able be indicated immediately in a RMSI.

[0157] In an example, an LBT indication based SSBS indication may be used. For short

SS burst set periodicity, a channel access priority class in which the entire SSBS duration, for example less than 5 milliseconds (ms), is reserved after an LBT procedure succeeds may be used. An SSBS indicator, for example, a bitmap, that indicates SS burst sets within RMSI periodicity may be utilized. For 4 SS burst sets within a RMSI periodicity, 4-bit bitmap may be used such that a 1 may represent an enabled SSBS or that an LBT procedure succeeds, and a 0 may represent a disabled SSBS or that an LBT procedure fails.

[0158] The channel access priority class in which the entire N SS burst set duration (N x P) may be reserved after initial an LBT procedure succeeds may be used. In an example, an N may represent a number of SSBS within an RMSI periodicity. Also, a P may represent SS burst periodicity.

[0159] A network may perform an LBT procedure in an example. The first K SSBs or

SSBGs due to a successful LBT procedure may be reserved.

[0160] The union of disabled SSBs across SSBs within RMSI periodicity may be used. If one SSB is disabled due to an LBT procedure failure, all SSBs in the same position in other SSBGs may be disabled even if some SSBs in the same position or other SSBGs may be enabled. In an example, a WTRU may buffer the received signal and process the data accordingly.

[0161] Figure 14 is a diagram illustrating an example RMSI which has smaller periodicity than an SSBS. In an example shown in Figure 14, SSBS 1420, 1440, 1460, 1480 may have larger periodicity than RMS1 1410, 1415, 1430, 1435, 1450, 1455, 1470, 1475. In an example, a RMSI may be used to indicate an SSB/SSBG/SSBS.

[0162] Figure 15 is a diagram illustrating an example RMSI which has the same periodicity as an SSBS. In an example shown in Figure 15, SSBS 1520, 1525, 1540, 1545, 1560, 1565, 1580, 1585 may have the same periodicity as the RMS1 1510, 1515, 1530, 1535, 1550, 1555, 1570, 1575. As in other examples, the RMSI here may be used to indicate an SSB/SSBG/SSBS.

[0163] According to an example in the disclosed subject matter, channel access and reservation mechanisms for SSB are disclosed herein. For example, procedures used for channel access for SSB are disclosed. A WTRU may be provided with an indication of intended SSB transmission. The intended SSB transmission may be indicated in a RMSI. LBT may be performed right before SSB transmission such that, if LBT succeeds, reserve COT is to cover an entire SSBS. This may reduce the number of LBT procedure that need to be performed. If an LBT procedure fails, an entire SSBS may be skipped. This may waste an entire SSBS since some of SSBG or SSB may still succeed an LBT procedure and may be able to be transmitted. Alternatively, an SSBG LBT procedure may be performed and if the SSBG LBT procedure succeeds, an entire SSBG may be transmitted. Otherwise the entire SSBG may be skipped or an SSB LBT procedure may continue. Alternatively, an SSB LBT procedure may be performed. If the SSB LBT procedure succeeds, this SSB may be transmitted, otherwise this SSB may be skipped.

[0164] Due to skipping SSB, SSBG or SSBS, SSB detection performance may degrade.

However resource utilization may be improved.

[0165] The network may reserve the channel for COT duration for SSB or SSBG transmission. The COT may depend on the transmission duration of SSB or SSBG. Short LBT with short channel reservation duration and long LBT with long channel reservation duration may be supported

[0166] Short LBT with short channel reservation duration may be used for SSB transmission. Long LBT with long channel reservation duration may be used for SSBG or SSBS transmission. However, short LBT with short channel reservation duration and long LBT with long channel reservation duration may have relatively low priority channel access.

[0167] A new channel access priority class may also be introduced which may include a short LBT with a long channel reservation duration. This may be used to enable SSB transmission in NR-U. Due to a large number of SSBs, a long duration for SSBS transmission may be required. If a short channel reservation duration is used, SSB transmission may be more subject to channel unavailability and LBT. If a long LBT is used, SSB transmission may be blocked. Reducing the duration of an LBT procedure can increase the chance to access the channel. For high priority class channel access, such as SSB transmission, a short LBT procedure and a long channel reservation duration may be used. A short LBT procedure with a long channel reservation duration may be used for an SSBG or an entire SSBS transmission with high priority channel access. [0168] If an MCOT cannot support SSBG or entire SSBS then COT cover partial SSBG or partial SS burst set may be applied such that if SSBG is partially covered, then this SSBG may be disabled and/or an LBT procedure for each SSB may result in enabling this SSBG. RMSI indication may be based on this partial SSBG for both SSB and SSBG.

[0169] In order to maintain the same number of actual SSB transmission, the following solutions may be used alone or in combination. In a first solution, if LBT fails, the base station may repeat or retransmit this SSB in another candidate location. The RMSI can indicate this change. This may require additional SSB resource(s). In a second solution, the base station may skip this SSB transmission and reduce the number of SSB transmissions. This may cause performance degradation.

[0170] During the gap between SSBs or SSBGs, channel(s) may be reserved during the gap. Some useful DL channels, such as, for example, additional SSB, DRS, PDCCH, PDSCH, RMSI, OSI, RACH Msg2 & 4, paging, and the like, may be transmitted in those gaps instead of dummy signal in order to avoid waste of resource or improve resource utilization.

[0171] Additional SSBs may be configured, in case that an LBT procedure fails, and the network may switch to other SSB locations for SSB transmission. Example solutions may use overprovisioning of SSB indication(s). In over-provisioning SSB, more than one opportunity for SSB and/or SSBG transmission may be provided or configured. If one SSB or SSBG is skipped due to an LBT procedure, other SSBS(s) and/or SSBG(s) may be used. In a further example, SSB diversity can be achieved at the cost of additional resources. Rate matching may be done based on overprovisioning SSB or SSBG instead of actual SSB or SSBG.

[0172] According to an example of the disclosed subject matter, DRS burst set design and construction for NR-U is disclosed herein, including different DRS designs. Different DRS designs (DRS types) may be used in a DRS Burst set based on high coverage or low-overhead. It also may be possible to switch between different designs. Long and short DRS types may be considered. Default DRS type may be used with a default/lower periodicity for initial access for WTRUs. The change in DRS type may be indicated in at least one of RMSI, OSI or RRC signalling. An SS/PBCH block may be used as main constituent to the DRS block. There may or may not have CRS/channel- state-information reference signal (CSI-RS), other reference symbols or other frequency division multiplexing (FDM) physical channels with them to complete the DRS.

[0173] A short DRS may be a lower overhead design. In this design 4 OFDM symbols may be used to generate design similar to similar to the NR SS/PBCH. One of the designs may be the same as an NR design which are mapped in 4 OFDM symbols. This may be considered as a baseline design, such as, for example, the PSS, PBCH, SSS, PBCH design. Symbols of PBCH may also occupy resource elements (REs) on the two sides of SSS as similar to the NR design. Content of a PBCH may be modified according to NR-U requirements and may be applied to all designs disclosed herein.

[0174] In a second example design, wider bandwidth symbols may be used to increase detection capabilities. In a first example, the design may include NRU-PSS, NRU-PBCH, NRU-SSS, NRU-PBCH. The NRU-PSS and NRU-SSS may be generated with longer M/Gold sequences (for example, length 255) and NRU-PBCH may have double the number of REs, for example, 24 REs for each OFDM symbol, coded with a lower code-rate.

[0175] In another example, the design may include NRU-PSS, PBCH, NRU-SSS, PBCH.

This configuration is similar in design to the design above. However, unlike NR, the PBCH may occupy the same number of resource blocks (RBs), which may be 12 RBs, as the PSS/SSS.

[0176] In NRU, a DRS may start anywhere in the DMTC window after an LBT procedure is successful. It may be considered as a floating DRS. This may prevent the waste of spectrum in the cases when time instance when spectrum is assessed to be empty and when the target DRS slot or slot boundary do not align.

[0177] Within DMTC, a DRS may start at any slot, or any symbol within a slot and may be related to misalignment within the slot. The examples herein are related to misalignment for the slot.

[0178] To reduce WTRU complexity, different candidate position to start within a slot may be defined. For example, 2, 4, 6, 8 candidate starting positions within a slot may be defined for designs with 4 OFDM symbols.

[0179] In an example, Long DRS may be a higher overhead design. It may include

SS/PBCH blocks with greater than 4 OFDM symbols. It may increase detection probability because of repetition of symbols and longer transmission duration. A number of designs may be considered such as, for example, according to one design, modified PSS/SSS symbols and repeated PBCH may be included. For example, a design may include NRU-PSS, PBCH, PBCH, NRU-SSS, PBCH, PBCH. Here, NRU-PSS and NRU-SSS may be generated with longer M/Gold sequences. For example, L = 255. As the number of PBCH symbols is doubled, the total number of REs is also double and hence PBCH can be coded with lower code-rate. This may apply to all the examples below with multiple numbers of PBCH symbols. It also may be possible to generate 2 PBCH OFDM symbols and repeat them

[0180] In another design example, each symbol of SS/PBCH block may be repeated two times. For example, a design may include PSS, PSS, PBCH, PBCH, SSS, SSS, PBCH, PBCH. Here, example cases provided elsewhere herein provide different candidates starting positions which may be possible within the slot. [0181] In another design example, PSS/SSS may be repeated twice, and PBCH may use many more symbols, which may be repeated version(s), or more RE(s) using a low code-rate. For example, a design may include PSS, PSS, PBCH, PBCH, PBCH, SSS, SSS, PBCH, PBCH, PBCH. Also, an example a design may include PSS, PSS, PBCH, PBCH, PBCH, PBCH, SSS, SSS PBCH, PBCH, PBCH, PBCH.

[0182] In other designs, it also may be possible to repeat whole block design twice. For example, a design may include PSS, PBCH, SSS, PBCH, PSS, PBCH, SSS, PBCH and PSS, PBCH, PBCH, SSS, PBCH, PBCH, PSS, PBCH, PBCH, SSS, PBCH, PBCH. When a number of OFDM symbol are greater than 8 it may not be beneficial to have more than 2 starting candidate position. However, it may be possible to use 2 candidate positions based on the design.

[0183] It may be possible to use both types, long and short, with a specific selected

SS/PBCH block design in the same system and switch between them. Polarity of PSS / SSS or DMRS of PBCH may be used to indicate long or short type. A WTRU may also be able to detect it blindly using the PSS/SSS pattern and if duplication is detected.

[0184] Wideband SS/PBCH Block may be designed to occupy 24 or even 48 RBs for DRS to meet the regulatory requirement of minimum power. FDM of 2 or more SS/PBCH Blocks may be considered for the wideband design. This may be done with long or short designs.

[0185] X s of LBT may be performed before transmission of DRS, if it does not carry data or if the maximum transmission duration is <Y ms. Here, X may be 25 s for <6GHz (based on LAA) and 8 for >60GHz, as proposed. Y may be 1mS for <6GHz and {0.5, 0.25} ms for >6GHz, as proposed.

[0186] A different number of candidate starting positions in different designs are used in example embodiments above. This offset may be referred to as a DRS-Offset (within the slot), herein. If any of the predetermined starting point for DRS is used, a DRS-Offset may be used to acquire timing information along with synchronization signal block time index (SSBI) included in PBCH.

[0187] PBCH may carry the location index of the first PSS offset (of transmitted DRS). If only one design is used and only two possible candidate locations are used, the DRS-Offset also may be indicated using Polarity of PSS / SSS or DMRS of PBCH. If DRS always starts at a fixed location in the slot, DRS-Offset may be considered 0 for the scope of examples herein.

[0188] In accordance with another design, SSB locations may be used as a reference.

These SSB locations may be identical or different from the NR design. Using the offset from closest SSB Location (SSB-Offset) along with SSBI, the WTRU may be able to acquire the timing. [0189] According to an example of the disclosed subject matter, DRS burst designs and

DMTC windows are disclosed herein. DRS burst design may be used to accommodate a beam- based design of NR. Due to the possibility of LBT failure, a WTRU may not always receive DRS in slot 0 or any pre-configured slot or sub-frame. A DMTC window may be defined, where a DRS of the DRS Burst Set may be transmitted in any slots, or any sub-frames, within the DMTC window. In an example, for a WTRU to accurately acquire timing for the system, the gNB must indicate this Slot- Offset/Subframe-Offset, and DRS-Offset mentioned elsewhere herein, to the WTRU. The method of indication may vary and may depend on the type of DRS burst design. DMTC may be defined for different types of burst design for DRS, which are described below.

[0190] Figure 16 is diagram illustrating an example DMTC window defined for an entire

DRS sweep. In an example shown in Figure 16, a DMTC may be defined for an entire sweep of DRS. One long period of DMTC may be defined for all DRS locations as a group. An LBT procedure may be performed before the start of a DRS sweep. A DRS may be transmitted on all beams at the DRS locations with delay/offset because of initial LBT. The Subframe-Offset, Slot-Offset and DRS- Offset within the slot may be indicated within the DRS, such as explicitly in PBCH, implicitly using the DMRS of PBCH along with SSB, and implicitly using SSS. An LBT procedure may or may not be performed before each DRS transmission. If an LBT procedure is performed for each beam and a channel is found to be busy in specific beams, DRS for those beams may be skipped. A second sweep may occur within same DMTC (after updating the Subframe-Offset, Slot-Offset). A list of SSB(s) may also be updated for rate matching purposes. Example SSBs 1610 through 1690 are shown in Figure 16.

[0191] Figure 17 is a diagram illustrating an example DMTC window defined for each DRS location. In an example shown in Figure 17, a DMTC window may be defined for each DRS location. A DMTC window may be identical for all locations. However, it may vary with subcarrier spacing (SCS) or the carrier frequency. DRS burst set candidate locations along with the actually transmitted DRS/SSB may be used for WTRU to receive data or perform RRC measurements. The current NR candidate SS/PBCH blocks may not be able to support transmission of all the beam with DMTC as many of the candidate locations are adjacent to each other and DMTC for those locations may overlap. The DRS candidate location may have to be modified for NR-U to support individual DMTC for each location such that. For example, 1 DMTC of T_DMTC ms may be defined for each of n DRS locations, where n = 1 to 64 for >6GHz and 1 to 4 or 8 for <6GHz. Further, T_DMTC may be {0.5mS, 1mS, 2mS}. Example SSBs 1710 and 1720 are shown in Figure 17.

[0192] Different patterns (or values of T _DMTC) may be used for different SCS and/or carrier frequency. An LBT procedure may be performed for each beam. If a channel is found to be busy at the OFDM symbol at a candidate location, and the channel clears within the defined/configured DMTC window, a DRS may be transmitted with Subframe-Offset, Slot-Offset and DRS-Offset. During initial access, once a WTRU synchronises using DRS, it may find the SFN, SSBI, Slot-Offset and DRS-Offset from PBCH and acquire the timing of system.

[0193] Figure 18 is a diagram illustrating an example DMTC defined for a set of beams. In an example shown in Figure 18, DMTC may be defined for set of beams, which may be considered to be a hybrid solution between the above two design examples in Figure 16 and Figure 17. Here, DMTC may be defined for set or group of locations. Example SSBs 1810 through 1890 are shown in Figure 1 Different examples of such burst design may include the following.

[0194] As a first example, a DMTC of T_DMTC ms may be defined for SSBs with location {4,

8} + 28^*n and {16, 20} + 28^*n DRS candidate locations. Accordingly, a different DMTC may be used for each slot. They may be located at To + {4, 8} + T_DMTc^*n and To + {16, 20} + T_DMTC ^*n, where To may be a time for a start of a frame, or sub-frame.

[0195] As a second example, 1 DMTC of T_DMTC ms may be defined for SSBs with location

{4, 8, 16, 20} + 28^*n DRS candidate locations (Different DMTC group of 2 Slots). The location also may be modified so that 1 DMTC of T_DMTC ms defined for each n of {4, 8, 12, 16} + 28^*n, candidate locations where the locations in each group are evenly distributed. They may be located at To + {4,

8. 16, 20} +T_DMTc^*n.

[0196] As a third example, 1 DMTC of T_DMTC ms may be defined for SSB with location {8,

12. 16, 20, 32, 36, 40, 44} + 56^*n. (Different DMTC for group of 4 Slots). They may be located at To + {8, 12, 16, 20, 32, 36, 40, 44} +T_DMTc^*n.

[0197] A DRS burst set pattern and DMTC window size may be defined and fixed for a given SCS or carrier frequency. A gNB may perform an LBT procedure before transmitting DRS for each group. gNB may use larger beam to perform an LBT procedure to cover all the beam directions used at the candidate locations in the group.

[0198] If the medium is busy during LBT, the transmission of DRS for all beams at the locations of the group may be delayed until the channel clears. If the channel clears within the defined/configured DMTC window, a DRS for the group may be transmitted with Slot-Offset and DRS-Offset.

[0199] The transmission of DRS may occur at any point within the DMTC window. The offset may correspond with an actually used sub-frame with respect to the subframe of original candidate location where the DRS was scheduled, and may be designated as a Subframe-Offset. The offset of an actually used slot with respect to the slot of original candidate location where the DRS was scheduled may be designated as a Slot-Offset. The candidate location for these DRS also may be referred to as DMTC Occasions.

[0200] A DRS offset may be the offset of the DRS within the slot. A gNB may transmit these Subframe-Offset, Slot-Offset, DRS-Offset to WTRU to acquire exact timing. The Subframe- Offset/ Slot-Offset/D RS-Offset indication may be Implicit or Explicit such that the following examples may be used. A Subframe-Offset/ Slot-Offset may be partly or fully included in NR-PBCH. Also, a Subframe-Offset/ Slot-Offset may also be combined with DRS-Offset within Slot, such as in examples discussed above. In addition, a Subframe-Offset/ Slot-Offset/DRS-Offset may be combined with SSBI. Further, a function of Slot-Offset/Subframe-Offset, DRS-Offset, SSBI or any combination of them may be created and indicated. Other possible ways to indicate may include initialization of sequence for PBCH-DMRS or SSS. Polarities for sequences also may be used to indicate 1 bit of the offset.

[0201] Along with initial access, DRS also are used for RRC measurement. Multiple parameters of a DMTC configuration may be indicated to the WTRU for that. These parameters may be transmitted in RRC signalling. A DRS Configuration type may be indicated if multiple DRS configurations are supported. If multiple types are supported, there may be a default configuration, which is a super set of different configurations, which is used for initial access.

[0202] DMTC duration may be the duration for which a WTRU may look for DRS after the

DMTC occasion. A DMTC duration may be variable based on the type of DRS-configuration, SOS of the system or the carrier frequency system is operating in. In an example, 6 ms may be used in LAA at <6GHz. It also may be able to be dynamically increase or decrease based on interference environment

[0203] A DMTC-Periodicity may be, for example, 40 ms, 80 ms, or 160 ms. The periodicity may also be dependent on configuration type for DMTC. It may be different for different SOS. Frequency locations for DRS may be indicated if they are different than default.

[0204] An opportunistic DRS may be transmitted if spectrum is available at an OFDM symbol part of the DRS burst set at the given periodicity. This may imply the DRS-Offset and Slot- Offset both are 0 for those DRSs. A periodicity of opportunistic DRS may be higher than the DMTC window, but due to LBT rules, the transmission of these opportunistic DRS may not be guaranteed. They may or may not contain RMSI /OSI / Paging FDM. NR-U PBCH may contain flag(s) to indicate a presence of RMSI/OSI/Paging FDM with the opportunistic DRS. It may be possible to have a different frequency for opportunistic DRS for different beams. Location for Opportunistic DRS in different SSB/Beam may be the as the starting point of DMTC defined in examples herein. They may include {4, 8, 16, 20} + 28^*n for 120kHz SCS and {8, 12, 16, 20, 32, 36, 40, 44} + 56^*n for 240kHz SCS.

[0205] According to examples of the disclosed subject matter, RMSI transmission in NR-U is disclosed. An SS block with 60kHz SCS and multiplexing SSB / RMSI may be used. FDM may be used for 30kHz SCS and TDM may be used for 60kHz SCS. This configuration may apply to SSB meeting OCB requirements. RMSI presence or absence may be indicated in PBCH. SS/PBCH block repetition and/or CSI-RS may be used as a reservation signal.

[0206] RMSI may be time or frequency multiplexed with an SS/PBCH block in NR-U.

During cell search, if a WTRU determines that a RMSI control resource set (CORESET) is present, then the WTRU may determine time occasion and frequency resources of the RMSI CORESET using indication bits in the PBCH. These bits may indicate an SFN and slot index. The SFN and slot index may be relative to the NR-U SS/PBCH block or may be absolute based on the timing information acquired from the SS/PBCH block. It may depend on whether the sub-carrier spacing of SS/PBCH and RMSI are the same or different.

[0207] SS/PBCH and RMSI may be TDMed. Separate LBT for a RMSI PDCCH may be required. The LBT procedure may fail and a gNB may not transmit the RMSI PDCCH at the determined slot/location. Accordingly, a window for RMSI CORESET may be defined and the starting location of the window may be indicated, for example, in SSB or PBCH. The length of window for RMSI reception may also be indicated. Within this RMSI reception window, RMSI CORESET may be present. This window may be defined in terms of number of slots or OFDM symbols, such as, for example as A^" slots or OFDM symbols. This example window length may also be constant, predetermined or known to a WTRU. To indicate multiple different configurations of time information (for example, SFN, slot), frequency information (for example, start/offset, number of RBs), duration (for example, in terms of slots or symbols) with small number of bits, multiple tables may be used. These tables may be chosen based on system parameters (for example, SCS, band of operations, and the like). Different indexes of tables may indicate a set of predefined values. A symbol index within the slot may or may not be used to indicate the starting symbol of CORESET. If symbol is specified, the WTRU may monitor that specific symbol for CORESET in each of the A^" slots. If symbol index is not specified, the WTRU may monitor all CORESETs in each of the A^" slots.

[0208] As an example, the SS/PBCH block and CORESET may be multiplexed using

TDM. WTRU may monitor PDCCH in RMSI CORESET over A^" consecutive slots starting from slot For SS/PBCH block with index ^z , the WTRU may determine an index of slot ⁿ° as «o {r · i^m + \i -L7 j)mod

depending

being odd or even. ^M

, slot number and A^" may be provided by tables which may be known to gNB and WTRU.

[0209] As another example, the SS/PBCH block and RMSI CORESET may be multiplexed using FDM. A WTRU may monitor for a PDCCH in RMSI CORESET with periodicity of an SS/PBCH block or an integer multiple of the SS/PBCH block. In these cases the WTRU may determine the slot index "^c and ^SFNc based on a parameter from a table and SCS. The WTRU may also use a band of operations the SS/PBCH block with index ¹.

[0210] According to an example of the disclosed subject matter, while transmitting DRS on

Multiple-BWP, a gNB may follow different procedures. For example, a first multi-BWP access procedure may be configured such that during the DMTC period, the gNB may perform channel access on each BWP individually on all the BWP DRS needs to be transmitted. A gNB may transmit when all BWP are clear to transmit. After an LBT procedure, if the gNB finds some of the BWP to be empty and others busy, the gNB may transmit a reservation signal on the BWP which were available. If the busy BWP becomes available within the DMRC, the gNB may transmit DRS on all the BWP simultaneously. It may include identical DRS-Offset and Slot-Offset in DRS transmitted on all the BWP.

[0211] A second multi-BWP access procedure may be configured such that the gNB may perform an LBT procedure on a primary BWP. If the primary BWP is found to be empty, the gNB may transmit on all the BWP simultaneously such that it transmits identical OSI / RMSI on all BWP and/or transmits a different redundancy version (RV) for OSI/RMSI simultaneously on different

BWP.

[0212] A third multi-BWP access procedure may be configured such that during the DMTC period, the gNB may perform channel access on each BWP individually on all the BWP DRS needs to be transmitted. gNB may transmit DRS on BWPs as they become available. For example, after an LBT procedure, if a gNB finds some of the BWP to be empty and others busy, the gNB may transmit DRS on the BWP, which were available. If the busy BWP becomes available within the DMTC, gNB may transmit DRS on those BWP as well. It may include different DRS-Offset and Slot-Offset in different BWP based on the DRS location.

[0213] To align DRS in different BWPs, different example rules may be used. For example, different DMTC for each BWP may be used, DMTC may be used only for cell-defining SSB, and/or non-cell defining SSB may use only opportunistic DRS. [0214] According to an example disclosed herein, in NR-U, a gNB may perform an LBT procedure before transmission of a paging DCI and paging message. If a channel is not free exactly at the paging occasion time, LBT may fail. Hence a window may be specified, during which a WTRU may continue to observe DCI for P-RNTI. A gNB may perform an LBT procedure and transmit the paging DCI anytime during a paging opportunity window (POW). Paging DCI may indicate the location of the paging message.

[0215] If a paging message is transmitted in a slot (or non-slot) after the paging DCI, then the next slot may be reserved by using a slot-configuration indicator (or non-slot-configuration indicator). In NR-U, frame Structure 3 (FS3) defined for LAA may be modified so a gNB may start from any OFDM symbol (or non-slot). The gNB may include the slot configuration indicator in the PDCCH (on common search space) of the slot. The slot (or non-slot) format indicator may indicate number of OFDM symbols and the direction of transmission for the current or next slot (or mini-slot).

[0216] In NR-U COTS may be defined per LBT category and SCS. If a paging DCI and paging message can be transmitted within one COT duration, the gNB may have to perform only one an LBT procedure. CAT2 (No Back off) / CAT4-P1 (small Back off) LBT may be used for paging transmission.

[0217] COT for CAT2 LBT is 1 mS and CAT4-P1 is 2 mS defined for <6GHz in LAA. COTS may be modified to much smaller number for >6GHz carrier. It may or may not be always possible to put a paging message in the same slot or mini-slot as the paging DCI, and hence this requirement may or may not be met.

[0218] It also may be possible to use two separate LBT procedures. Specifically, a first

LBT procedure may be used for paging DCI and a second LBT procedure may be used for paging message if paging message is scheduled in a later slot, beyond acquired COT boundary. The examples disclosed above may be applied to each beam where paging DCI and paging message is transmitted.

[0219] According to an example of the disclosed subject matter, one NR Paging Occasion

Window (NR-POW) for NR-U may be defined by several consecutive subframes, or slots of minislots, where there may be P-RNTI transmitted on a new radio-physical downlink control channel (NR-PDCCH) addressing the paging message. The NR-POW may start in subframe #0 (or with fixed offset for different beams) and the number of subframes may be determined by the POW-Size. One or more of the following NR parameters may be provided in system information: NR-POW-Size, Pageless-Slots-To-Monitor, and the like. When DRX is used, the WTRU needs only to monitor one POW per DRX cycle. Two example scenarios may be considered depending on paging FDM with SS/PBCH or DRS. [0220] In a first example scenario, using the paging FDM with SS Block, the NR-paging occasion (PO) may be FDM with the DRS, which implies, POW may overlap with DMTC. The POW may be defined as entire duration of DMTC where PDCCFI addressing the paging message may be present on any slots / mini-Slots. In such a scenario, the POW-Size may be identical or lower than the DMTC window size. WTRU may observe the PO for paging DCI for entire POW-Size. It may stop to observe the PO for paging DCI after it receives certain number of slots without P-RNTI (Pageless-Slots-To-Monitor). If in system NR-U the periodicity of DMTC is X and number of paging groups based on IMSI needs to be supported is Y, the periodicity for each PO becomes lower by factor of Y. In NR-U, to increase the periodicity for each PO, it also may be possible to FDM multiple message for different groups. An LBT procedure performed for an SS/PBCH Block can be used for a PO of multiple groups. To enable this, DCI with P-RNTI may also indicate the groups the paging message may be targeted for. Different group based on IMSI may be able to find their paging message based on predefined time-frequency pattern.

[0221] In a second example scenario, a NR-POW may not be FDM with DRS/SSB. In such a scenario, the NR-POW may be defined for (or associated with) each beam (corresponding to each DRS/SSB). The POW may be defined as X number of consecutive Slots / mini-Slots, in which there may be P-RNTI transmitted on PDCCFI addressing the paging message. Paging DCI for NR-POW may be located in Common Search Space. Paging message may be located in same Slot (or nonslot). It also may be located in a later slot or mini-slot.

[0222] Due to the nature of the NR-U system, there may be a problem when a gNB transmits P-DCI after an LBT procedure, but is not heard by a WTRU because of an interfering hidden node. In such cases, the gNB may transmit the paging DCI again in the next PO. Flowever, that approach may increase delays. gNB also may be able to increase or decrease periodicity of POs based on the interference environment. Modification of PO periodicity may be indicated to WTRU by RRC signalling.

[0223] If the paging DCI or paging message is completely transmitted before POW-

Duration is over, a gNB may be able to indicate the end of POW. A gNB slot configuration indicator for paging or Slot Format Indicator to indicate a number of symbols that Paging-DCI and paging message may occupy. A slot configuration indicator may be similar to a subframe configuration indicator defined for LAA (for frame structure type 3), which may indicate total number of OFDM symbol(s) to be transmitted for current or following slot. A WTRU may stop monitoring PDCCFI before the end of the POW if it detects serving cell transmissions without P-RNTI allocation in PDCCFI in Pageless-Slots-To-Monitor number of consecutive slots. Pageless-Slots-To-Monitor might be transmitted to the WTRU in by upper layer signalling. It may also possible to define Pageless-nonSlots-To-Monitor for similar purpose.

[0224] POWs may be defined for multiple Paging-groups and Paging-sub-Groups, in an example. Different POW for different beams and for different groups based on I MSI may start at different slots and system frames. Different RBs may be used for different Paging sub-groups such as different but fixed RB locations may be defined for paging sub-groups, POW for different subgroups may be FDMed together. Further, frequency hopping with repetition during POW, fixed pattern for the frequency hopping, and frequency hopping amongst groups may reduce probability of interference from hidden nodes. In an alternate design, all the groups may be scheduled in FDM and an indication bit map about groups being paged may be used in DCI.

[0225] According to an example of the disclosed subject matter, a paging occasion window computation is disclosed such that, for example, PF for each beam (PF_B) may be computed with PF_B = SFN mod T == (T div N_b)^*(WTRUJD mod N_b). The PO may be computed from i_s = floor(WTRUJD/N_b) mod Ns_b. Ns_b, N_b will be Modified for number of Beams (maximum or actually used) and nB: 4T, 2T, T, T/2, T/4, T/8, T/16, T/32, T/64, ... T/256 ...etc.; N_b: min(T,nB) ^* numBeams; and Ns_b: max(1,nB/T) ^* numBeams.

[0226] POW-Size may dependent on one or more factors such as if STA/ WTRU of other

RATs are present. For example, if WTRUs of other RAT or other service provider are not present, POW of 1 Slot (or non-slot) may be enough. Another factor may be network load such that for low- network load small POW-Size may be used, as medium may be controlled by a gNB. Another factor may be that the unit of POW-Size may be slot of mini-slot or different length of mini-slot, which may be default for paging. Another factor may be that POW-Size may be indicated in RMSI / RRC signalling. APOW may start at the same location as PO computed for NR and last for POW-Size duration.

[0227] According to an example of the disclosed subject matter, alternative techniques for paging for NR-U are disclosed such that, for example, paging may be transmitted in the Initial Active BWP. One Paging Frame (PF) may be one Radio Frame, which may contain one POW if P-RNTI is transmitted on PDCCFI. A first radio frame of POW may contain repetition.

[0228] When DRX is used the WTRU may only need to monitor POW per DRX cycle. If a paging indication is used, a PDCCFI in POW may be monitored only if the paging indication indicates the group of the WTRUs. WTRU Group may be derived from WTRU ID. PF may be provided based on the following equation:

SFN mod T= (T div N + PF_Offset)*(WTRUJD mod N) Equation (1) [0229] Several multiplexing patterns between the CORESET for paging and SS/PBCH block may be used in NR-U. TDM may be used and, accordingly, the paging may occur in a later frame. FDM may be used for a current SS/PBCH block. For TDM the POW may start in slot #0 of the frame and the number of subframes may be determined by the POW-Size. For FDM, the POW may start in slot #0 and the number of subframes may be determined by the POW-Size. A WTRU may stop monitoring PDCCH before the end of the POW if it detects serving cell transmissions without P-RNTI allocation in PDCCH PagelessSfsToMonitor number of consecutive subframes. This PagelessSfsToMonitor may be signaled in RRC signaling.

[0230] To reduce the WTRU power consumption, some physical layer paging indication(s) may be used for paging. This may be a specific signal which may indicate an incoming page for a specific group. A wake up signal (WUS) may be used to indicate a specific group. Cyclic shift of WUS or different versions of WUS may be used. A function of WUS may also be used. The WUS may be transmitted on all the beams as part of SS/PBCH blocks. Advanced paging may be used. This may achieve reduction in WTRU complexity. WTRU may monitor the paging PDCCH only if the paging indicator for its group is present or WUS indicates that the group is present. A paging indicator or WUS may be located before an SS block with certain offset or may be part of SS block. Cyclic shift or orthogonal cover code (OCC) may be used for the indication.

[0231] Figure 19 is a flow diagram illustrating an example method for paging using beam feedback. In an example shown in Figure 19, a WTRU may receive a beam swept paging group indicator 1920. The WTRU may determine whether its group is paged based on the received beam swept paging group indicator 1930. WTRUs in the indicated group may transmit beam feedback to the base station 1940. Specifically, the WTRU and other WTRUs in the indicated group may conduct beam reporting with limited or full beam feedback 1950. The WTRU may check the current procedure and may enhance the procedure during beam reporting. As a result of the beam feedback, the base station may transmit and the WTRU may receive a PDCCH, a PDSCH or both in selected beam directions 1960.

[0232] Figure 20 is a flow diagram illustrating an another example method for paging. In an example shown in Figure 20, a WTRU may receive a beam swept paging group indicator 2020. The WTRU may determine whether its group is paged based on the received beam swept paging group indicator 2030. If the WTRU’s group is not paged, the WTRU will not try and decode a paging PDCCH or a paging PDSCH. This may result in a power savings over time. Further, if the WTRU’s group is paged, the WTRU may try and decode a paging PDCCH, a paging PDSCH or both [0233] In further examples, a combination of methods or hybrid methods that combine the solutions provided herein may be used. For example, paging method examples of Figure 19 and examples of Figure 20 may be combined into a hybrid paging method.

[0234] Power saving mechanisms may be used for paging and PO for NR-U. Wake-up signal may be used for NR-U. LBT may be performed in conjunction with a WUS. Solutions for wakeup signal(s) based paging may use a NR-PSS-like structure, WiFi-like Structure or Hybrid Structure. Repeated structure similar to legacy-long training field (L-LTF) in WiFi may be used. 3 different M/Gold-Sequences may be added in front of SS/PBCH block, for example, a Discovery Symbol before PSS/SSS. M/Gold sequences with WTRU/Group-specific shifts may be used for WUS based paging and for other PDCCFI(s) or the like. Further, Group Based PDCCFI WUS may be used.

[0235] Wakeup signal(s) may be configured in initial active BWP. Time repeated (zeroed sub-carriers) structure similar to L-LTF in WiFi with 3 different M/Gold-Sequences may be added in front of SS/PBCH block. Grouping for WUS in NR-U for example WTRU-ID based may be used. Preamble with or without NAV UL/DL Indicator may be used. This may be used for Multi-cell or multi-TRP operations as well. RMSI Monitoring may be performed for NR-U. For multiple subgroups, multiple WUSs may be tone interlaced and multiplexed. Offset based on WTRU ID may be used. WUS may be used for an FBE structure as it may align with one or more frame boundaries. Both UL and DL WUS may be used. UL WUS may indicate acquired COT and planned transmission to other WTRUs. WUS with different cyclic shift(s) (or OCC) may indicate the quantized load- duration of the transmission that will be followed. For example, DL/UL may be indicated by just simple inverted sequence X/-X sequence. WUS may enable a WTRU to detect a signal, for example, SSS, before going into actual demodulation of PDCCH for for example, paging DCI.

[0236] In the unlicensed operation, there may be no guarantee that a gNB can send a

PDCCH, in the configured PDCCH monitoring occasion, to the corresponding WTRU due to LBT. If the PDCCH monitoring occasions is increased by reducing the periodicity, it may result in more frequent attempts to decode PDCCH and may potentially increase the power consumption of the WTRU. WUS may be considered for NR-unlicensed for paging and other DL channels. The detection of a particular sequence may be performed with a simple correlator block. If WUS is not detected, or detected but indicating IDLE mode, then the WTRU may go back to sleep while not being bothered with decoding the PDCCH. Otherwise, the WTRU may wake up and may perform PDCCH decoding for example, for a paging PDCCH.

[0237] A WUS may be used for paging or other DL signals or channels. A modified version of SSS (or PSS) with group signature may be used. Frequency domain orthogonal sequences (for example Zadoff-Chu (ZC) like sequences) may be used. It or they may span over multi-OFDM symbols but may not be desirable from a power consumption perspective. Two (or Multi) level WUS may be used. For example, a first level may be a cell-specific WUS (with synchronization function) and a second level may be a PO-specific WUS. Group-based or Sub-Group based WUS may be used as well. ZC sequence with a PN sequence cover code may be used for WUS. Both time domain and frequency domain may be considered. PN sequence or code may be M sequence or Gold Sequence. On/off-key (OOK)-based tone signals may be used. Non-coherent energy detection may be considered. Design parameters such as number of tones, number of guard tones, and/or number of OFDM symbols may be considered. Preferably it may be better not to expand over symbols from a power saving perspective. Tone patterns in time/frequency to achieve time/frequency diversity may be used. Tx-Diversity may be used for WUS. WUS length may be one (or more) Slot, MiniSlot, Multiple Slots or one or more OFDM symbols. Variable WUS length may be used. A simplified PDCCFI where the baseband processing is substantially subsampled to allow a lighter version of receiver processing may be used. A WUS based Paging Indication may be used for NR-U. Wakeup signal and actual PDCCFI with paging DCI may be in the same slot or different slots (cross slot). An LBT procedure may be performed for a Wakeup signal and an LBT procedure may be performed for an actual PDCCFI. Further, grouping for WUS may be used in NR-U. A preamble, potentially with a NAV UL/DL Indicator (for example, for multi-cell design), may be used. NAV may be used in UL. If only a gNB sends a NAV indication, the hidden node may not be completely avoided. A preamble that enables asynchronous detection may be considered and used.

[0238] According to an example of the disclosed subject matter, channel access and a reservation mechanism for paging is disclosed such that, for example, for NR-U, an LBT procedure may be performed before transmitting a PDCCFI with paging DCI and potentially paging a message. As paging may be transmitted in multiple beam directions, different listening and transmission combinations for LBT may be considered such as an omni listening directional transmission and directional listening and directional transmission.

[0239] In an omni Listening directional transmission a gNB may change sensitivity for omni listening, as directional transmission may have longer range. As other option, it may perform a single LBT procedure before transmission of paging DCI in all the directions. A gNB may perform CAT4-Priority1 omni LBT to achieve longer COT to transmit in multiple beam-direction. In accordance with this design, all the beams may be part of the same POW (only grouped with WTRUJD). In accordance with a different design, gNB may perform LBT before every directional transmission to avoid problem of creating interference / collision for on-going transmission. [0240] In directional listening and directional transmission, a gNB may perform directional

LBT before transmission in each direction. CAT2 may be used (25uS listening for <6GHz, no back off) as the transmission may be less than 1mS for <6GHz. Here, each LBT procedure may be part of a POW for individual directions. This example method also may avoid an exposed node problem.

[0241] If a paging DCI and/or paging message are FDMed with DRS, a POW may overlap with the DMTC window and hence the LBT procedure performed for DRS may be sufficient to transmit the paging DCI and potentially the paging message. LBT parameters for NR-U paging may be different than regular NR-U LBT parameters. Accordingly, LBT parameters may be modified for directional listening, in an example.

[0242] According to an example of the disclosed subject matter, non-slot based paging and cross-slot scheduling is disclosed. In slot or non-slot based systems, a paging message may be transmitted in different slots or non-slots then slots or non-slot of paging DCI. In such a configuration, a situation may arise if a NR-U gNB can send after LBT the paging DCI (P-DCI). However, the gNB may not send a paging message (PM) in a described time/frequency (T/F) location because of failure (missed transmission) an LBT procedure. There is also a possibility that the gNB may send a PM in a described (T/F) location within COT, but the reception fails because of hidden node interference.

[0243] A rule may be created to solve the issue such that a gNB must schedule paging message within the COTs acquired during the paging DCI. It may be mandated for a gNB to use the same slot or (non-Slot). It also may be a consecutive slot or non-slot, which may be reserved by a slot configuration indicator. It also may be possible to define a window for receiving a paging message in cross-slot scheduling. If such window is defined, a WTRU may continue to observe longer duration, or more T/F resource, for a paging message after receiving the paging DCI.

[0244] According to an example of the disclosed subject matter, in NR-U, a bi-directional slot structure may be used for the advanced paging. An immediate response from the paged WTRU in the same beam may be used.

[0245] Figure 21 is a diagram illustrating an example of paging in bi-directional slots. As shown in an example in Figure 21, a gNB may transmit a paging group indicator along with the paging DCI 2120. After a switching gap 2130, all the WTRUs in that specific PO and in that paging group may send response(s) in the next OFDM symbol(s). Users in these groups may be assigned an RB and/or code to be used for paging response. This may also include feedback. Optional small control/data uplink/HARQ transmission(s) may also piggyback. Depending on the received feedback, a paging message 2150 may or may not be transmitted, else the remaining part of the slot may be used for other data. A slot-configuration indicator may be used to release the medium if no other data is to be transmitted.

[0246] Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements. Although the solutions described herein may consider LTE, LTE-A, New Radio (NR) or 5G specific protocols, it is understood that the solutions described herein are not restricted to this scenario and are applicable to other wireless systems as well.

[0247] In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals

(transmitted over wired or wireless connections) and 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 internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

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Claims

CLAIMS What is claimed is:

1. A method for use in a wireless transmit/receive unit (WTRU), the method comprising:

detecting a synchronization signal (SS)/Physical Broadcast Channel (PBCH) block;

obtaining one or more indications regarding a joint synchronization signal block (SSB) index and a time shift from the detected SS/PBCH block;

deriving at least one of frame, slot and symbol timing information based on the obtained joint SSB index and time shift;

obtaining timing information for detection of at least one of a channel access indicator (CAI) or an SSB indication; and

performing SSB measurements.

2. The method of claim 1 , further comprising:

on a condition that the WTRU successfully detects one or both of the CAI and the SSB indication, deriving one or more time locations of SSBs based on the detected one or both of the CAI and the SSB indication, wherein the SSB measurements are performed for actually transmitted SSBs.

3. The method of claim 1 , further comprising:

on a condition that the WTRU does not successfully detect at least one of the CAI and the SSB indication, searching all SSB time locations during an SSB sweep, wherein the SSB measurements are performed for all SSBs received during an SSB sweep.

4. The method of claim 1, wherein the CAI has a state of one listen before talk (LBT) procedure for all SSB transmissions during an SSB sweep.

5. The method of claim 1 , wherein the CAI has a state of one LBT procedure per SSB group (SSBG).

6. The method of claim 5, wherein a break is located between SSBGs.

7. The method of claim 1 , wherein the CAI has a state of one LBT procedure per SSB.

8. The method of claim 1 , further comprising:

receiving an indication of a widebeam LBT procedure for SSBGs in a synchronization signal burst set (SSBS).

9. The method of claim 1 , wherein one or more indications are obtained from an SS in the detected SS/PBCH block.

10. The method of claim 1, wherein one or more indications may be obtained from a PBCH in the detected SS/PBCH block.

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

a transceiver operatively coupled to a processor, the transceiver and the processor configured to detect a synchronization signal (SS)/Physical Broadcast Channel (PBCH) block; the processor configured to obtain one or more indications regarding a joint synchronization signal block (SSB) index and a time shift from the detected SS/PBCH block;

the processor configured to derive at least one of frame, slot and symbol timing information based on the obtained joint SSB index and time shift;

the processor configured to obtain timing information for detection of at least one of a channel access indicator (CAI) or an SSB indication; and

the transceiver and the processor configured to perform SSB measurements.

12. The WTRU of claim 11 , further comprising:

on a condition that the WTRU successfully detects one or both of the CAI and the SSB indication, the processor configured to derive one or more time locations of SSBs based on the detected one or both of the CAI and the SSB indication, wherein the SSB measurements are performed for actually transmitted SSBs.

13. The WTRU of claim 11 , further comprising:

on a condition that the WTRU does not successfully detect at least one of the CAI and the SSB indication, the transceiver and the processor configured to search all SSB time locations during an SSB sweep, wherein the SSB measurements are performed for all SSBs received during an SSB sweep.

14. The WTRU of claim 11, wherein the CAI has a state of one listen before talk (LBT) procedure for all SSB transmissions during an SSB sweep.

15. The WTRU of claim 11 , wherein the CAI has a state of one LBT procedure per SSB group (SSBG).

16. The WTRU of claim 15, wherein a break is located between SSBGs.

17. The WTRU of claim 11, wherein the CAI has a state of one LBT procedure per

SSB.

18. The WTRU of claim 11 , further comprising:

the transceiver configured to receive an indication of a widebeam LBT procedure for SSBGs in a synchronization signal burst set (SSBS).

19. The WTRU of claim 11 , wherein one or more indications are obtained from an SS in the detected SS/PBCH block.

20. The WTRU of claim 11, wherein one or more indications may be obtained from a

PBCH in the detected SS/PBCH block.