Method and system for efficient uplink synchronization maintenance with deactivated secondary cell groups

Abstract

A wireless transmit / receive unit (WTRU) may receive indication information indicating an uplink (UL) configuration and one or more trigger conditions for transmitting UL signals. Based on receiving a deactivation command or satisfying a condition for the WTRU to trigger deactivation of a secondary cell group (SCG), the WTRU may deactivate the SCG. Based on the satisfaction of the UL configuration and the one or more trigger conditions, the WTRU may transmit the UL signal via the SCG. The WTRU may receive, via a primary cell group (MCG), an indication of synchronization or asynchronization of the SCG. Based on receiving the non-synchronization indication, including a timing advance (TA) delta value, the WTRU may update the UL TA to the SCG based on the TA delta value. Using the updated UL TA to the SCG, the WTRU may transmit one or more subsequent UL signals via the SCG.

Description

[0001] This application is a divisional application of an invention patent application with an application date of January 12, 2022, application number 202280014230.6, and invention name “Method and system for efficient uplink (UL) synchronization maintenance with a deactivated secondary cell group (SCG)”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Application No. 63 / 136,531, filed on January 12, 2021, the contents of which are incorporated herein by reference. Background Art

[0004] A wireless transmit / receive unit (WTRU) may be configured to utilize resources provided by two different nodes connected via a non-ideal backhaul, where the nodes may provide access using the same or different radio access technologies (RATs). The nodes may be base stations. One node may act as a master node (MN), controlling resources associated with one or more cells referred to as a master cell group (MCG), and the other node may act as a secondary node (SN), controlling resources associated with one or more cells referred to as a secondary cell group (SCG). The MN and SN are connected via a network interface, and at least the MN is connected to a core network.

[0005] In case of dual connectivity, the WTRU may be configured to have two medium access control (MAC) entities: one MAC entity for the MCG and one MAC entity for the SCG. The WTRU may be configured to receive and process radio resource control (RRC) reconfiguration messages via the MCG, where the reconfiguration may result in an SCG addition, change / modification, or release. Additionally, the WTRU may be configured to receive and process RRC reconfiguration messages via the SCG, where the reconfiguration may not require coordination with the MN. Summary of the invention

[0006] Examples and implementations of uplink (UL) synchronization maintenance are provided herein. Examples and implementations of secondary cell group (SCG) deactivation, dormancy, or both are provided herein. Examples and implementations may be applied to multi-radio dual connectivity (MR-DC), or may be applied to other wireless communication systems. Examples and implementations used alone or in any combination may include the following. A wireless transmit / receive unit (WTRU) may receive indication information from a network, the indication information indicating a UL configuration of one or more UL signals and indicating one or more trigger conditions for transmitting the one or more UL signals. Based on receiving a deactivation command from the network or satisfying one of the one or more conditions for the WTRU to trigger deactivation of the SCG, the WTRU may deactivate the SCG and may run a time value associated with the SCG. In addition, the WTRU may transmit one or more UL signals to the network via the SCG. Additionally or alternatively, based on the UL configuration and the satisfaction of one or more trigger conditions for transmitting one or more UL signals, the WTRU may transmit one or more UL signals to the network via the SCG. The WTRU may receive one of a synchronization indication of the SCG or an out-of-sync indication of the SCG from the network via a master cell group (MCG). Further, based on receiving the out-of-sync indication from the SCG, including a timing advance (TA) increment value, the WTRU may update the UL TA to the SCG based on the TA increment value and may restart running the time value associated with the SCG. In addition, using the updated UL TA to the SCG, the WTRU may transmit one or more subsequent UL signals to the network via the SCG.

[0007] In one example, one or more UL signals are used to maintain UL synchronization with the SCG when the SCG is deactivated, dormant, in a power saving state, or operating in long discontinuous reception (DRX). In another example, the WTRU may stop monitoring the SCG physical downlink control channel (PDCCH) based on receiving a deactivation command from the network or satisfying one of the one or more conditions for the WTRU to trigger deactivation of the SCG.

[0008] In another example, based on receiving the synchronization indication, the WTRU may restart the time value associated with the SCG. Further, based on receiving the desynchronization indication of the SCG, the WTRU may stop running the time value associated with the SCG and consider the SCG to be out of synchronization with the WTRU, which does not include the TA increment value. In addition, the one or more UL signals may include one or more of a sounding reference signal (SRS) or a random access channel (RACH) preamble.

[0009] Further, one or more trigger conditions for transmitting the UL signal may include one or more of timing information, expiration of a time value associated with the SCG, or a change in a downlink (DL) signal level of the SCG. In addition, the time value associated with the SCG may be a time alignment timer (TAT) value associated with the SCG. In addition, running the time value associated with the SCG may include starting to run the time value associated with the SCG or maintaining running the time value associated with the SCG. Further, based on the time value associated with the SCG, the WTRU may activate the SCG. The WTRU may also transmit UL data via the SCG without using a random access (RA) procedure.

[0010] Examples and embodiments also include a method for use in a wireless transmit / receive unit (WTRU), the method comprising: receiving configuration information about a sounding reference signal (SRS) used with a secondary cell group (SCG) from a network via a master cell group (MCG); and transmitting the SRS to the network via the SCG. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

[0016] Figure 2 is a diagram showing an example of uplink (UL) synchronization maintenance and deactivation of a secondary cell group (SCG);

[0017] Figure 3 is a diagram showing another example of UL synchronization maintenance and deactivation of SCG; and

[0018] Figure 4 is a diagram showing yet another example of UL synchronization maintenance and deactivation of SCG. DETAILED DESCRIPTION

[0019] Figure 1A 1 is a diagram illustrating an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through sharing of system resources (including wireless bandwidth). For example, the communication system 100 may employ one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multi-carrier (FBMC), etc.

[0020] like Figure 1A As shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110 and other networks 112, but it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a station (STA)) may be configured to transmit and / or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0021] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device that is configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an evolved Node B (eNB), a Home Node B, a Home evolved Node B, a next generation Node B such as a gNode B (gNB), a New Radio (NR) Node B, a site controller, an access point (AP), a wireless router, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0022] Base station 114a may be part of RAN 104, which may also include other base stations and / or network elements (not shown), such as base station controllers (BSC), radio network controllers (RNC), relay nodes, etc. Base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as cells (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, a cell associated with base station 114a may be divided into three sectors. Therefore, in an embodiment, base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In an embodiment, base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

[0023] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0024] More specifically, as noted above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 116. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​Uplink (UL) Packet Access (HSUPA).

[0025] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0026] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using NR.

[0027] 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 example using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0028] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), GSM Enhanced Data Rates for Evolution (EDGE), GSM EDGE (GERAN), etc.

[0029] Figure 1A The base station 114b in the may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in local areas such as commercial venues, homes, vehicles, campuses, industrial facilities, sky corridors (e.g., for use by drones), roads, and the like. In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement radio technologies 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 radio technologies such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-APro, NR, etc.) to establish a picocell or a femtocell. As Figure 1A As shown, the base station 114 b may be directly connected to the Internet 110. Therefore, the base station 114 b may not need to access the Internet 110 via the CN 106.

[0030] The RAN 104 may be in communication with the CN 106, which may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, delay requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not described in detail in the specification, the CN 106 may be configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. Figure 1AAlthough not shown in the figure, it will be appreciated that the RAN 104 and / or the CN 106 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may utilize NR radio technology, the CN 106 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0031] The CN 106 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

[0032] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0033] Figure 1B is a system diagram illustrating an exemplary WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any subcombination of the foregoing elements while remaining consistent with an embodiment.

[0034] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functions that enable the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0035] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) via an air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be a transmitter / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive RF and light signals. It should be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0036] Although the transmit / receive element 122 is Figure 1B 1 as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0037] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. For example, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0038] The processor 118 of the WTRU 102 may be coupled to a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit) and may receive user input data therefrom. The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any type of suitable memory, such as a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from and store data in a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0039] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power to other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0040] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0041] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, Module, FM radio unit, digital music player, media player, video game player module, Internet browser, virtual reality and / or augmented reality (VR / AR) device, activity tracker, etc. Peripheral device 138 may include one or more sensors. The sensor may be one or more of the following: gyroscope, accelerometer, Hall effect sensor, magnetometer, orientation sensor, proximity sensor, temperature sensor, time sensor; geographic location sensor, altimeter, light sensor, touch sensor, magnetometer, barometer, gesture sensor, biometric sensor, humidity sensor, etc.

[0042] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) and DL (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit for reducing and / or substantially eliminating self-interference via hardware (e.g., choke) or via signal processing performed by a processor (e.g., a separate processor (not shown) or via the processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) or DL ​​(e.g., for reception)) may be concurrent and / or simultaneous.

[0043] Figure 1C 1 is a system diagram showing the RAN 104 and the CN 106 in accordance with 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.

[0044] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In an embodiment, the evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0045] Each of the evolved Node Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0046] Figure 1C The illustrated CN 106 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. Although the foregoing elements are depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0047] The MME 162 may be connected to each of the evolved Node-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, etc. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0048] The SGW 164 may be connected to each of the evolved Node-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during inter-evolved Node-B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, and the like.

[0049] 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.

[0050] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0051] Although the WTRU Figures 1A to 1D Although described as a wireless terminal, it is contemplated that in certain representative embodiments, such a terminal may (eg, temporarily or permanently) use a wired communications interface with a communications network.

[0052] In a representative embodiment, the other network 112 may be a WLAN.

[0053] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for a BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or carries traffic away from the BSS. Traffic originating from outside the BSS and leading to the STA may be reached by the AP and may be delivered to the STA. Traffic originating from the STA and leading to a destination outside the BSS may be sent to the AP to be delivered to the corresponding destination. Traffic between STAs within the BSS may be sent by the AP, for example, wherein the source STA may send traffic to the AP, and the AP may deliver traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic may be sent between the source and destination STAs (e.g., directly between them) using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs (eg, all STAs) within or using the IBSS may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad-hoc" communication mode.

[0054] When using the 802.11ac infrastructure operating mode or a similar operating mode, the AP may transmit a beacon on a fixed channel (such as a primary channel). The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a dynamically set width. The primary channel may be an operating channel of the BSS and may be used by the STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including the AP) may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0055] High throughput (HT) STAs may communicate using a 40 MHz wide channel, for example, through a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0056] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz and / or 80MHz channels can be formed by combining continuous 20MHz channels. A 160MHz channel can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For the 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and data can be transmitted by transmitting STA. At the receiver of the receiving STA, the above-mentioned operation for the 80+80 configuration can be reversed, and the combined data can be sent to the medium access control (MAC).

[0057] 802.11af and 802.11ah support operating modes below 1GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support meter type control / machine type communication (MTC), such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0058] WLAN systems that can support multiple channels and channel bandwidths such as 802.11n, 802.11ac, 802.11af, and 802.11ah include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA (which supports the minimum bandwidth operating mode) from all STAs operating in the BSS. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (supporting only the 1MHz operating mode) is transmitting to the AP, all available frequency bands may be considered busy even if most of the available frequency bands remain idle.

[0059] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0060] Figure 1D 1 is a system diagram showing the RAN 104 and the CN 106 in accordance with an embodiment. As noted above, the RAN 104 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0061] The RAN 104 may include gNBs 180a, 180b, 180c, although it will be appreciated that the RAN 104 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In an embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, 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 techniques. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on an unlicensed spectrum, while the remaining component carriers may be on a licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) techniques. For example, the WTRU 102a may receive coordinated transmissions from the gNB 180a and the gNB 180b (and / or the gNB 180c).

[0062] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable parameter sets. For example, OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmit spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or Transmission Time Intervals (TTIs) of varying or scalable lengths (e.g., containing varying numbers of OFDM symbols and / or varying absolute time lengths over time).

[0063] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c while also not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate or connect with the gNBs 180a, 180b, 180c while also communicating or connecting with other RANs, such as the eNode-Bs 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-Bs 160a, 160b, 160c may serve as mobility anchors for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0064] Each of the gNBs 180a, 180b, 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, support of network slicing, interworking between DC, NR, and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b, routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0065] Figure 1DThe CN 106 shown in FIG. 1 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possibly a data network (DN) 185a, 185b. Although the aforementioned elements are depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0066] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via the N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of non-access stratum (NAS) signaling, mobility management, etc. The AMF 182a, 182b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c based on the type of services used by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced mobile broadband (eMBB) access, services for MTC access, etc. The AMF 182a, 182b may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as WiFi.

[0067] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 106 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 106 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0068] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, etc.

[0069] The CN 106 may facilitate communications with other networks. For example, the CN 106 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to the DNs 185a, 185b via the UPFs 184a, 184b via the N3 interfaces to the UPFs 184a, 184b and the N6 interfaces between the UPFs 184a, 184b and the local DNs 185a, 185b.

[0070] Given that Figures 1A to 1D as well as Figures 1A to 1D Corresponding to the description of the present invention, one or more or all of the functions described herein with reference to one or more of the following may be performed by one or more simulation devices (not shown): WTRU102a-d, base station 114a-b, evolved Node B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b and / or any other device described herein. The simulation device may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the simulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0071] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, the one or more simulation devices may perform one or more or all functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. The one or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device may be directly coupled to another device for testing purposes and / or perform testing using over-the-air wireless communications.

[0072] The one or more simulation devices may perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device may be used in a test scenario in a test lab and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. The one or more simulation devices may be test equipment. Direct RF coupling and / or wireless communication performed via an RF circuit system (e.g., which may include one or more antennas) may be used by the simulation device to transmit and / or receive data.

[0073] The description herein is for exemplary purposes and is not intended to limit in any way the applicability of the methods further described herein to other wireless technologies and / or wireless technologies using different principles where applicable. In the examples and implementations provided herein, the term "network" may refer to one or more gNBs (which in turn may be associated with one or more transmit / receive points (TRPs)), one or more base stations, or any other node in a radio access network. Further, in the examples and implementations provided herein, the term "multi-radio dual connectivity" (MR-DC) may indicate a dual connectivity between an E-UTRA and an NR node or between two NR nodes.

[0074] Examples, implementations, and principles of multi-connectivity are provided herein. A WTRU may be configured to utilize resources provided by two different nodes connected via a non-ideal backhaul, where the nodes may provide access using the same or different RATs. These nodes may be base stations. One node may act as a master node (MN), controlling resources associated with one or more cells referred to as a master cell group (MCG), and another node may act as a secondary node (SN), controlling resources associated with one or more cells referred to as a secondary cell group (SCG). The MN and SN are connected via a network interface, and at least the MN is connected to a core network.

[0075] In case of dual connectivity, the WTRU may be configured to have two medium access control (MAC) entities: one MAC entity for the MCG and one MAC entity for the SCG. The WTRU may be configured to receive and process radio resource control (RRC) reconfiguration messages via the MCG, where the reconfiguration may result in an SCG addition, change / modification, or release. Additionally, the WTRU may be configured to receive and process RRC reconfiguration messages via the SCG, where the reconfiguration may not require coordination with the MN.

[0076] Examples and implementations of UL synchronization maintenance are provided herein. Examples and implementations of SCG deactivation, sleep, or both are provided herein. Examples and implementations used alone or in any combination may include the following. The WTRU may be configured to send UL signals (sounding reference signal (SRS), random access channel (RACH) preamble, etc.) to the SCG and to the network via the SN when the SCG is deactivated / sleep to maintain UL synchronization. In addition, the WTRU may be configured to maintain / start / restart running a time value or time alignment timer (TAT) associated with the SCG when the SCG is deactivated / sleep. Further, the WTRU may be configured to receive a response to a UL signal sent for synchronization purposes from the network via the MCG. And / or the WTRU may be configured to monitor the SCG physical downlink control channel (PDCCH) / physical downlink shared channel (PDSCH) at a specified time / duration / resource when the SCG is deactivated / sleep to obtain a response from the network via the SN and SCG. In addition, the WTRU may be configured to receive a response from the network (via a timing advance command (TAC), a random access response (RAR), etc.) to a UL signal sent for synchronization purposes, the response indicating whether it is in UL synchronization with the SCG; if it is not in synchronization, it optionally includes a timing advance (TA) update / increment value. In addition, if a TA update is indicated, the WTRU may be configured to update the UL TA using the SCG. In addition, if it is in UL synchronization with the SCG (or a TA update is performed), the WTRU may be configured to restart running the TAT associated with the SCG. In addition, if it is not in UL synchronization with the SCG (and no TA update is indicated / performed), the WTRU may be configured to stop running the TAT associated with the SCG. When the WTRU is instructed to perform SCG activation or when the WTRU itself triggers SCG activation, if the TAT associated with the SCG is still running, the WTRU may be configured to perform SCG activation without first performing a random access (RA) procedure on the SCG. When the WTRU is instructed to perform SCG activation or when the WTRU itself triggers SCG activation, if the TAT associated with the SCG is not running, the WTRU may also be configured to perform a RA on the SCG when the SCG is activated.

[0077] Examples and implementations of direct UL synchronization status indication from the network via SCG are provided herein. A WTRU configured for MR-DC with MCG and SCG may perform one or more of the following examples and implementations alone or in any combination. The WTRU may receive from the network an UL configuration indicating UL signals (SRS, RACH preamble, etc.) for maintaining UL synchronization with the SCG when the SCG is deactivated / sleep. Further, the UL configuration may include information about when / how to send the UL signal (e.g., time / frequency information, power level to be used, number of times the UL signal may need to be repeated, etc.), and about when / how to receive a response to the UL signal (e.g., time / frequency information, indication of receiving a response from the network via the SN and SCG, etc.). In addition, the WTRU may deactivate the SCG based on receiving a deactivation command from the network or based on satisfying the conditions for SCG deactivation triggered by the WTRU. In addition, the WTRU may stop monitoring the SCG PDDCH. In addition, the WTRU may start / restart running the TAT associated with the SCG. In addition, the WTRU may send a configured UL signal to the SCG and to the network via the SN when it is determined that the transmission time has arrived and the SCG is still deactivated. Further, the WTRU may start monitoring the SCG PDCCH / PDSCH or SCG to receive an indication as to whether it is in a UL synchronization state with the SCG. In addition, the WTRU may stop monitoring the SCG PDCCH / PDSCH after receiving an indication as to whether it is in a UL synchronization state with the SCG. If the indication is a synchronization indication, the WTRU may restart running the TAT associated with the SCG. If the indication is an out-of-sync indication, the WTRU may stop running the TAT associated with the SCG. If the indication includes a TA increment value, the WTRU may update the UL TA to the SCG based on the indicated value and restart running the TAT associated with the SCG. When the WTRU is instructed to perform SCG activation or when the WTRU itself triggers SCG activation, if the TAT associated with the SCG is still running, the WTRU may be configured to perform SCG activation without first performing a RA process on the SCG. When the WTRU is instructed to perform SCG activation or when the WTRU itself triggers SCG activation, if the TAT associated with the SCG is not running, the WTRU may also be configured to perform a RA on the SCG when the SCG is activated.

[0078] Examples and implementations of UL synchronization status indication via MCG are provided herein. A WTRU configured for MR-DC with MCG and SCG may perform one or more of the following examples and implementations alone or in any combination. The WTRU may receive from the network an UL configuration indicating UL signals (SRS, RACH preamble, etc.) for maintaining UL synchronization with the SCG when the SCG is deactivated / sleep. Further, the UL configuration may include information about when / how to send the UL signal (e.g., time / frequency information, power level to be used, number of times the UL signal may need to be repeated, etc.), and about when / how to receive a response to the UL signal (e.g., time / frequency information, indication of receiving a response from the network via MN and MCG, etc.). In addition, the WTRU may deactivate the SCG based on receiving a deactivation command from the network or based on satisfying the conditions for SCG deactivation triggered by the WTRU. In addition, the WTRU may stop monitoring the SCG PDDCH. In addition, the WTRU may start / restart running the TAT associated with the SCG. In addition, the WTRU may send a configured UL signal to the SCG and to the network via the SN when it is determined that the transmission time has arrived and the SCG is still deactivated. Further, the WTRU may receive an indication from the network via the MCG as to whether it is in a UL synchronization state with the SCG. If the indication is a synchronization indication, the WTRU may restart the TAT associated with the SCG. If the indication is an out-of-sync indication, the WTRU may stop running the TAT associated with the SCG. If the indication includes a TA increment value, the WTRU may update the UL TA to the SCG based on the indicated value and restart the TAT associated with the SCG. When the WTRU is instructed to perform SCG activation or when the WTRU itself triggers SCG activation, if the TAT associated with the SCG is still running, the WTRU may be configured to perform SCG activation without first performing a RA process on the SCG. When the WTRU is instructed to perform SCG activation or when the WTRU itself triggers SCG activation, if the TAT associated with the SCG is not running, the WTRU may also be configured to perform a RA on the SCG when the SCG is activated.

[0079] Examples and implementations of activation, deactivation, or both of a secondary cell (SCell) in a NR are provided herein. NR supports activation, deactivation, or both of a SCell via a MAC control element (CE). If the SCell is deactivated, the WTRU will not perform the following operations: transmit SRS on the SCell; report channel state information (CSI) of the SCell; transmit on the uplink shared channel (UL-SCH) on the SCell; transmit on the RACH on the SCell; monitor the PDCCH on the SCell or the SCell (via another activated SCell); or transmit data on the physical uplink control channel (PUCCH) on the SCell. The WTRU may be activated, deactivated, or both via a MAC CE activation, deactivation, or both command. For example, the WTRU may be activated via a MAC CE activation command. In addition, the WTRU may be deactivated via a MAC CE deactivation command. The WTRU may also change from activation to deactivation after the SCell deactivation timer or SCell deactivation time value expires. In one example, the WTRU may also change from activation to deactivation after determining that the SCell deactivation time has passed.

[0080] In order to have a more dynamic mechanism to support power saving on the SCell, the network generally also supports the concept of dormancy. For dormancy, the WTRU may maintain some of the functions of the activated SCell while saving power by not performing PDCCH monitoring. In addition, dormancy is achieved by switching the WTRU to a dormant bandwidth part (BWP). The switching may be performed via layer 1 (L1) signaling using DCI. When in a dormant BWP, the WTRU does not transmit SRS. Further, when in a dormant BWP, the WTRU reports CSI, but may only report periodic CSI, may only report semi-static CSI, or report both. In addition, when in a dormant BWP, the WTRU does not monitor the PDCCH on or of the SCell. In addition, when in a dormant BWP, the WTRU performs beam management and beam failure recovery procedures. However, when in a dormant BWP, the WTRU does not transmit on the PUCCH. In addition, when in a dormant BWP, the WTRU does not transmit on the RACH. Dormancy is associated with an activated SCell state—when the WTRU is in an SCell activated state, the WTRU may be changed to a dormant BWP. However, when in SCell deactivated state, the WTRU may not be changed to / from the dormant BWP. A DCI on another SCell may change the SCell from the dormant BWP to the non-dormant BWP.

[0081] One or more concepts of SCG dormancy may be standardized. SCG dormancy may also be referred to as a deactivated SCG / primary cell of a secondary cell group (PSCell), and remains consistent with the examples provided herein. The concept is to put the entire SCG (e.g., PSCell and SCG SCell) into a power saving state when the WTRU does not need the SCG, and to reactivate the SCG as quickly as possible when needed. In one example, the WTRU may not need the SCG when the aggregate data rate carried by the WTRU is below a certain level or when the SCG radio quality is not good enough. There are several ways to achieve placing the entire SCG in a power saving state and reactivating the SCG as quickly as possible. For example, one method may be to adopt SCell dormancy behavior for the PSCell as well. In one example, this method may include associating a dormant BWP with the PSCell. Another method may include enabling the WTRU to operate efficiently in a single connection, wherein the SCG configuration is stored and prepared to be activated / applied when needed. Yet another method may include operating the SCG in long discontinuous reception (DRX).

[0082] Various mechanisms may be applied to SCG deactivation / sleep. Exemplary aspects of SCG deactivation / sleep may include considering only a single deactivated SCG. Other exemplary aspects of SCG deactivation / sleep may include not monitoring the PDCCH when the SCG is deactivated. Additionally or alternatively, during SCG deactivation / sleep, the WTRU may maintain execution, limit, or relax radio resource management (RRM) measurements / reports regarding the MN / SN configuration of the SCG when the SCG is deactivated / sleep. Further, when the SCG is deactivated, the SCG deactivation / sleep may support mobility procedures, etc. In an example, the mobility procedure may include MCG changes, SCG changes / modifications, etc. In an example, the modification of the SCG may include maintaining the SCG while changing one or more parameters of the SCG, changing one or more configurations of the SCG, adding one or more SCells to the SCG, or removing one or more of one or more SCells from the SCG. Further, the SCG may be modified while also maintaining the PSCell.

[0083] When the SCG is in a deactivated state, the WTRU may send measurement results of the SN configuration. The measurement results may be embedded in the MCG ULInformationTransferMRDC message and sent via signaling radio bearer 1 (SRB1). In addition, when the SCG is in a deactivated state, the WTRU may receive an SCG RRCReconfiguration message embedded in the MCG RRC (Connection) Reconfiguration message on SRB1. Further, when the SCG is in a deactivated state, the SCG SCell cannot be in an activated state. In one example, the SCG SCell may only be deactivated. In several examples, dormancy may be allowed. In addition, several examples may include whether the SCell may be added / reconfigured / released.

[0084] In NR, a WTRU must be synchronized with the base station in the DL in order to be able to receive data, and must be synchronized in the UL in order for the base station to be able to receive data from the WTRU. For the DL, the WTRU is considered to have synchronization or be in synchronization in the DL if the exact timing at the start of the radio frame and the exact timing at the start of the OFDM symbol have been correctly detected. This is done by detecting and analyzing the synchronization signal (SS) blocks.

[0085] In order to be in sync in the UL, the WTRU must calculate the exact timing at which it should send uplink data. The uplink data may be sent on various channels including, for example, PUSCH, PUCCH, or both. Since the gNB is handling multiple WTRUs, the network must ensure that the UL signal from each WTRU should be aligned with the network's common receiver timer or the network's common receiver time value. Thus, UL synchronization basically adjusts the WTRU's uplink Tx timing and is done via the RACH procedure.

[0086] For the RACH procedure, the WTRU transmits a Physical Random Access Channel (PRACH) preamble and the network responds with a RAR including the TA information. In addition, additional information such as the WTRU identity Cell Radio Network Temporary Identity (C-RNTI), UL grant for subsequent messages from the WTRU, etc. may be included in the RAR. The WTRU will use the indicated TA to adjust its UL transmit timing. If the WTRU does not receive a RAR within a given time called the ra-ResponseWindow, it will attempt a new RA procedure.

[0087] The RACH process or procedure can be contention-based or contention-free. In contention-based random access (CBRA), the WTRU randomly selects a PRACH preamble from a set of possible preambles specified in the 3GPP standard, while for contention-free random access (CFRA), the WTRU is provided with a specific preamble that it must use when performing RACH. In one example, the WTRU may obtain a specific preamble when the WTRU is in a connected state. In the case of CBRA, conflicts may occur where more than one WTRU attempts RACH using the same preamble and contention resolution must be performed. For example, if two WTRUs send a random access request with the same PRACH, the two WTRUs will receive the same C-RNTI and resource allocation, and the two WTRUs will send L2 / L3 signals or messages to the network with the same resource allocation. The network may not be able to decode either signal (e.g., the two signals may interfere / cancel each other), or the network may only decode one of the signals. In the former case, both WTRUs will consider the RACH process failed (because the WTRU did not receive the HARQ-ACK for the signal or message that the WTRU had sent) and will try again or retry. In the latter case, the network will only provide HARQ-ACK to the WTRU whose signal was correctly decoded, and the other WTRU may therefore have to try the RACH process again.

[0088] To maintain UL time alignment, an ongoing TAC may be sent by the gNB when the WTRU is in connected mode. For example, this may be based on the timing of the SRS or channel quality indicator (CQI) received from the WTRU. Each time a TAC is received, the WTRU may restart a running time value or timer referred to as the TAT. From a higher layer perspective, the WTRU considers it to be synchronized in the UL while the TAT is running; if the TAT has expired or passed, it is considered to be out of synchronization. If out of synchronization in the UL, the WTRU must resynchronize the UL before it can transmit data again (e.g., via a RACH procedure as described above).

[0089] SCG deactivation is intended primarily for WTRU power savings. When there is a need for the SCG to be reactivated (e.g., increased data usage by the WTRU, arrival of UL / DL data for bearers associated with the SCG, etc.), the SCG must be used as quickly as possible. If fast reactivation is not possible, then SCG deactivation / reactivation will not have an advantage over releasing / adding an SCG (perhaps with the exception of some signaling reduction, since in the former case the SCG configuration may not need to be sent to the WTRU). Therefore, it is beneficial to keep the WTRU synchronized with the SCG in the UL when the SCG is deactivated to avoid the need to perform a RACH procedure every time the SCG is reactivated.

[0090] Several exemplary methods may be applied in this regard, and one example includes keeping the WTRU running the TAT when the SCG is deactivated. If the TAT has expired when the SCG is reactivated, the WTRU may have to first perform a RA procedure on the SCG before reactivating; otherwise, it may attempt to reactivate without performing a RA. A disadvantage of this approach may include that the WTRU may still be in a synchronized state even after the TAT expires. For example, the WTRU may still be in a synchronized state because the WTRU is stationary or has little mobility when the SCG is deactivated. In these cases, the RA procedure is not necessary and therefore will result in unnecessary delays in SCG reactivation. A further disadvantage of this approach may include that the WTRU may be out of sync even before the TAT expires. In this case, the WTRU will first attempt to reactivate without performing a RA (possibly multiple times), which will not succeed, and then must fall back to a RA, thereby increasing the SCG reactivation time compared to always performing a RA upon reactivation.

[0091] Provided herein are exemplary methods for efficient UL synchronization maintenance with a deactivated SCG. As provided herein, several methods are proposed to efficiently maintain UL synchronization of the WTRU with the PSCell when the SCG is deactivated so that the SCG can be activated more quickly. Although the examples provided herein mainly focus on the scenarios of SCG deactivation / activation, most of the methods are also applicable to normal operations, for example, maintaining SCG UL synchronization when the SCG is activated but no data transmission / reception occurs on the SCG, maintaining MCG UL synchronization when no data transmission / reception occurs on the MCG, etc. The exemplary methods for UL synchronization maintenance with a deactivated SCG provided herein improve efficiency in wireless communications by maintaining the power savings of SCG deactivation, but also allowing the SCG to be reactivated as quickly as possible.

[0092] In the examples provided herein, the terms "deactivated SCG" and "dormant SCG" are used interchangeably. In the examples provided herein, the terms "signal" and "message" are used interchangeably.

[0093] The examples provided herein include WTRU configurations for maintaining UL synchronization. In one exemplary method, an UL configuration is provided to the WTRU, which the WTRU uses to maintain UL synchronization with a deactivated SCG. The configuration may specify an UL signal / message that the WTRU must send to the network when the SCG is deactivated. The configuration may also specify how the signal must be sent to the network. For example, the configuration may specify the frequency resources, repetitions, power levels, etc. used when the signal is sent to the network. Further, the configuration may specify when the signal must be sent to the network. For example, the configuration may specify timing information about the signal. The timing information may be specified in absolute time (e.g., frame / time slot number), or relative to a TAT associated with the SCG (e.g., when the SCG has been deactivated for a duration equivalent to x% of the TAT). When the timing conditions for sending the UL signal are met, if the SCG is still in deactivation / sleep mode, the WTRU sends a UL signal to the SCG.

[0094] In another exemplary method, the UL configuration includes timing information about when the WTRU expects to receive a response from the network, starting from the time when the WTRU has sent the UL signal. The timing information may be exact timing information, such as a frame / time slot number. The timing information may also be relative time information, such as x ms after sending the UL signal. Further, the timing information may be a time window within which the WTRU may receive a response, such as between x ms and y ms after sending the UL signal.

[0095] In another exemplary method, the UL signal is an SRS signal. In this case, the UL configuration may include additional information, such as the number of SRSs that must be sent, the exact timing of each SRS, the relative time between SRSs, the power level to be used, etc.

[0096] In yet another exemplary method, the UL signal is a random access request. In this case, the UL configuration may include additional information, such as a PRACH preamble, RA response window time, number of RA attempts, power ramp configuration, etc. If no PRACH preamble is provided, the WTRU may use contention-based RA by randomly selecting a preamble. The selection of the preamble may be done in the same manner as the normal RACH procedure, or may be done in a different manner. For example, the WTRU may use only a subset of the possible PRACH preambles for RA.

[0097] In one exemplary method, the UL configuration includes an indication of whether a response from the network regarding a UL signal is to be received via the MCG or via the SCG. If the response from the network is to be received via the SCG, the UL configuration may include additional information regarding when / how the WTRU should monitor the SCG PDCCH to receive the response. For example, the additional information may include time / duration relative to when the UL signal is sent, absolute time / duration information, frequency information, etc.

[0098] The UL configuration may be received with the SCG deactivation command or provided to the WTRU in a separate configuration message before or after SCG deactivation. In one method, in response to receiving the UL configuration message, the WTRU resumes running the TAT associated with the SCG.

[0099] In one method, upon receiving the UL Configuration message, the WTRU maintains the TAT associated with the SCG. In another method, upon the SCG being deactivated, the WTRU restarts the TAT associated with the SCG. In yet another method, upon the SCG being deactivated, the WTRU maintains the TAT associated with the SCG.

[0100] Examples provided herein include receiving a synchronization indication and associated WTRU actions. If the WTRU is in synchronization, the network may indicate this to the WTRU implicitly or explicitly. An implicit indication may be that no response message is received from the network within a given duration after sending an UL signal. An explicit indication may be that a message is received. Exemplary messages include a new synchronization message in response to SRS reception, a RAR with a TA value of 0 in response to a RACH preamble, etc.

[0101] In one exemplary method, the synchronization indication is sent to the WTRU via the MCG. In another method, the synchronization indication is sent directly to the WTRU via the SCG. To achieve this, the WTRU may be configured with an additional configuration that indicates the timing / frequency configuration of when / where to expect the indication from the SCG. In the example, the additional configuration may be sent in addition to or as an alternative to the UL configuration that configures the SRS configuration. The WTRU may then monitor the PDCCH of the SCG only at that moment (or moments) to read the synchronization indication. If the WTRU does not receive the PDCCH at the moment (or moments) when it is configured to receive the TA increment value, the WTRU may consider it to be an implicit synchronization indication.

[0102] In one exemplary method, upon receiving the Sync Indication, the WTRU shall restart running the TAT. In yet another exemplary method, after receiving the Sync Indication, the WTRU maintains running the TAT. In another exemplary method, the next time the WTRU receives an SCG activation command, or activates the SCG based on the satisfaction of a WTRU-triggered SCG activation (e.g., arrival of UL data associated with an SCG bearer), the WTRU may send an SRS if the TAT has not expired, but may send an RA if the TAT has expired.

[0103] In another exemplary method, the next time the WTRU receives an SCG activation command, or activates the SCG based on satisfaction of a WTRU-triggered SCG activation (e.g., arrival of UL data associated with an SCG bearer), the WTRU may perform a RA even if the TAT has not expired, depending on how much TAT is still remaining. For example, if only 10% of the TAT is remaining, the WTRU may decide to perform a RA with a probability of 90% (i.e., 1-0.1). For example, the WTRU may extract a random value from a uniform distribution between 0 and 1, and if the extracted value is less than 0.9, decide to perform a RA.

[0104] In one exemplary method, after the WTRU resumes running TAT due to receiving a synchronization indication, the WTRU may operate in the same manner as it did immediately after SCG deactivation or receiving UL signal configuration. For example, when x% of the TAT has passed, the WTRU may send UL signals again.

[0105] Examples provided herein include receiving an out-of-sync indication and associated WTRU actions. If the WTRU is not in sync, the network may indicate this to the WTRU implicitly or explicitly. An implicit indication may be that no response message is received from the network within a given duration after sending the UL signal. An explicit indication may be the receipt of a message. For example, an explicit indication may be a new or modified "out-of-sync" message received in response to an SRS. Additionally, an explicit indication may be the receipt of a message containing a TA increment value. As an example, an explicit indication may be a TA value received in the RAR in response to a RACH preamble, a TAC or a new timing advance adjustment message received in response to an SRS, and the like.

[0106] In one exemplary method, an out-of-sync indication or TA increment value is sent to the WTRU via the MCG. For example, the message may be a TAC command sent from the network via the MN using the MCG, including an indication that the TA adjustment involves the SCG.

[0107] Figure 2200 is a diagram illustrating an example of UL synchronization maintenance and deactivation of an SCG. In the example shown in diagram 200, the WTRU may be configured with a configuration for sending one or more UL signals for maintaining UL synchronization with the SCG when the SCG is deactivated, dormant, or both (210). The configuration may include information about SRS, RACH preamble, etc. The configuration may also include trigger conditions for sending the UL signal. The trigger conditions may include timing information, etc. In an example, the configuration may include configuration resources for the WTRU to send the UL signal.

[0108] In addition, the WTRU may receive an indication to deactivate the SCG (220). Further, the WTRU may deactivate the SCG and may stop monitoring the SCG PDCCH (230). If the WTRU is already running, the WTRU may also keep running the SCG TAT; otherwise, the WTRU may start running the SCG TAT.

[0109] In addition, the WTRU may monitor for satisfaction of a condition, which may be a trigger condition (240), for sending an UL signal to resynchronize with the SCG when the SCG is deactivated, dormant, or both. The condition may include one or more of TAT expiration, SCG TAT expiration, another type of timer expiration, time value expiration, determination that the SCG time has passed, etc.

[0110] In an example, the WTRU may check or may determine whether the condition is met. In one example, the condition is met (250), and the WTRU may accordingly send a configured UL signal to the SCG using the configured resources (260). In one example, the condition may be met when the SCG TAT has expired. In another example, the condition is met when another type of timer has expired, another type of time value has expired, or it is determined that another type of time has passed. In another example, the condition is not met (250), and the WTRU may accordingly continue to monitor for satisfaction of the condition (240). The WTRU may continue to monitor until the condition is met (250), until a specific time has expired, or until the WTRU receives instructions to the contrary.

[0111] Further, the WTRU may receive a synchronization indication (270) regarding the SCG from the network via the MN using the MCG. Additionally or alternatively, the WTRU may receive an out-of-sync indication (270) having a TA value applied to the SCG from the network via the MN using the MCG. In one example, the TA value may be a TA delta value.

[0112] Additionally, if a TA value or a TA increment value is received, the WTRU may update the TA for the SCG (280). Additionally, the WTRU may restart running the SCG TAT (290). Further, the WTRU may then continue to monitor for the satisfaction of a condition to send an UL signal to resynchronize with the SCG when the SCG is deactivated, dormant, or both. In one example, the condition may be a trigger condition.

[0113] Therefore, when the SCG is reactivated, the WTRU will already be synchronized with the SCG. Therefore, the WTRU can use the SCG without the need for a RACH procedure. This method can achieve more efficient wireless communications, power savings for the WTRU, and faster use of the SCG by the WTRU when the SCG is reactivated. For example, this method can achieve more efficient UL synchronization maintenance, including UL synchronization maintenance with a deactivated SCG.

[0114] In an exemplary method, an out-of-sync indication or TA increment value is sent directly from the network to the WTRU via the SCG. To achieve this, the WTRU may be configured with an additional configuration that indicates the timing / frequency configuration regarding when / where to expect the out-of-sync indication or TA increment value from the network via the SCG. In one example, the additional configuration may be sent to the WTRU along with the UL configuration that configures the SRS configuration. The WTRU may then monitor the PDCCH of the SCG only at that moment or moments to read the out-of-sync indication or TA increment value. If the WTRU does not receive a signal on the SCG PDCCH at the moment or moments when it is configured to receive the TA increment value, the WTRU may consider it an implicit out-of-sync indication.

[0115] In yet another exemplary method, TA adjustment may be performed in two steps to avoid unnecessary monitoring of the SCG PDCCH for TA increment values ​​while the WTRU is in sync. The WTRU may monitor the SCG's PDCCH to obtain the TA increment only if it first receives an explicit out-of-sync indication via the MCG.

[0116] In an exemplary method, when the WTRU receives an implicit / explicit out-of-sync message but does not receive a TA increment value, the WTRU may initiate a RA procedure to the PSCell to bring the UL back into sync. Afterwards, the WTRU may deactivate the SCG and restart running TAT.

[0117] In yet another exemplary method, the WTRU treats the receipt of an implicit / explicit out-of-sync message (but no TA increment value) as an implicit SCG reactivation message. The WTRU may perform a RA upon SCG reactivation and may keep the SCG activated. In an example, the WTRU may keep the SCG activated until an explicit SCG deactivation message is received from the network, until a certain configurable duration has elapsed, until a condition for WTRU-triggered SCG deactivation is met (e.g., no DL / UL data for the SCG bearer for a certain configurable duration, etc.), etc.

[0118] In another exemplary method, when the WTRU receives an implicit / explicit out-of-sync message but does not receive a TA increment value, the WTRU may stop running the TAT. For example, the WTRU may consider the TAT to be expired. In yet another example, the WTRU may consider that the time has passed. The next time the WTRU receives an SCG activation command, or activates the SCG based on the satisfaction of the WTRU-triggered SCG activation (e.g., UL data associated with the SCG bearer arrives), the WTRU may perform a RA.

[0119] In another exemplary method, when the WTRU receives an implicit / explicit out-of-sync message but does not receive a TA increment value, the WTRU may stop running the TAT. For example, the WTRU may consider the TAT to be expired. In yet another example, the WTRU may consider that the time has passed. The next time the WTRU receives an SCG activation command, or activates the SCG based on the satisfaction of the WTRU-triggered SCG activation (e.g., UL data associated with the SCG bearer arrives), the WTRU may send an SRS.

[0120] In an exemplary method, when the WTRU receives an implicit / explicit out-of-sync message but does not receive a TA increment value. Therefore, the WTRU may keep the TAT running. The next time the WTRU receives an SCG activation command, or activates the SCG based on the satisfaction of the WTRU-triggered SCG activation (e.g., UL data associated with the SCG bearer arrives), the WTRU may send an SRS if the TAT has not expired; but if the TAT has expired, the WTRU may send an RA. For example, the WTRU may send an SRS when it is determined that the time has not passed, but the WTRU may send an RA when it is determined that the time has passed.

[0121] Figure 3is a diagram showing another example of UL synchronization maintenance and deactivation of an SCG. In the example shown in diagram 300, the WTRU may receive indication information from the network indicating the UL configuration of one or more UL signals and indicating one or more trigger conditions for transmitting the one or more UL signals (310). Based on receiving a deactivation command from the network or satisfying one of the one or more conditions for the WTRU to trigger deactivation of the SCG, the WTRU may deactivate the SCG and may run a timer associated with the SCG or run a time value associated with the SCG (320). In addition, the WTRU may transmit one or more UL signals to the network via the SCG (330). In one example, the transmission may be based on the UL configuration and the satisfaction of one or more trigger conditions for transmitting the one or more UL signals.

[0122] The WTRU may receive one of a synchronization indication of the SCG or an out-of-sync indication of the SCG from the network via the MCG (340). Further, based on receiving the out-of-sync indication of the SCG, including a TA increment value, the WTRU may update the ULTA to the SCG based on the TA increment value, and may restart a timer associated with the SCG or restart a time value associated with the SCG (350). In addition, using the updated UL TA to the SCG, the WTRU may transmit one or more subsequent UL signals to the network via the SCG (360). Additionally or alternatively, the WTRU may transmit UL data using the updated UL TA to the SCG. Further, additionally or alternatively, the WTRU may transmit UL transmissions using the updated UL TA to the SCG.

[0123] In one example, one or more UL signals are used to maintain UL synchronization with the SCG when the SCG is deactivated, dormant, in a power saving state, or operating in long DRX. In another example, the WTRU may stop monitoring the SCG PDCCH based on receiving a deactivation command from the network or satisfying one of the one or more conditions for the WTRU to trigger deactivation of the SCG.

[0124] In another example, based on receiving a synchronization indication, the WTRU may restart a timer associated with the SCG or restart a time value associated with the SCG. Additionally or alternatively, based on receiving a synchronization indication, the WTRU may restart a different timer associated with the SCG or a second timer associated with the SCG. In another example or in an alternative example, based on receiving a synchronization indication, the WTRU may restart a different time value associated with the SCG or a second time value associated with the SCG. Further, based on receiving an out-of-sync indication from the SCG, the WTRU may stop running a timer associated with the SCG or stop running a time value associated with the SCG and consider the SCG to be out of sync with the WTRU, which does not include a TA increment value. In addition, one or more UL signals may include one or more of an SRS or a RACH preamble.

[0125] Further, one or more trigger conditions for transmitting the UL signal may include one or more of timing information, expiration of a timer associated with the SCG, expiration of a time value associated with the SCG, a determination that a time associated with the SCG has passed, or a change in the SCG DL signal level. In an example, further trigger conditions may include a need to send UL data or a change in the UL signal level.

[0126] In addition, the timer associated with the SCG may be a TAT timer associated with the SCG. In addition, running the timer associated with the SCG may include starting to run the timer associated with the SCG or maintaining one of the timers associated with the SCG. Further, based on the timer associated with the SCG, the WTRU may activate the SCG. The WTRU may also transmit UL data via the SCG without using the RA procedure.

[0127] Additionally or alternatively, the time value associated with the SCG may be a TAT value associated with the SCG. Further, running the time value associated with the SCG may include starting running the time value associated with the SCG or maintaining running the time value associated with the SCG. Further, based on the time value associated with the SCG, the WTRU may activate the SCG. The WTRU may also transmit UL data via the SCG without using the RA procedure.

[0128] Additionally or alternatively, the time associated with the SCG may be a TAT time associated with the SCG. Further, based on a determination that the time associated with the SCG has passed, the WTRU may activate the SCG. In an example, the time associated with the SCG may be an activation time or an activation time associated with the SCG. The WTRU may also transmit UL data via the SCG without using a RA procedure.

[0129] In one exemplary method, when the WTRU receives the TA increment value, the WTRU may adjust the TA associated with the SCG accordingly and restart the running TAT. In another exemplary method, when the WTRU receives the TA increment value, the WTRU may adjust the TA associated with the SCG accordingly, but maintain the running TAT.

[0130] Figure 4 400 is a diagram illustrating yet another example of UL synchronization maintenance and deactivation of an SCG. In the example shown in diagram 400, the WTRU may deactivate the SCG and may run a timer associated with the SCG or a time value associated with the SCG (420). Further, based on satisfying a trigger condition for transmitting a UL signal, the WTRU may transmit a UL signal to the network via the SCG (430).

[0131] Additionally, the WTRU may receive from the network via the MCG one of a synchronization indication of the SCG or an out-of-sync indication of the SCG (440). Additionally, based on receiving the out-of-sync indication of the SCG, including the TA increment value, the WTRU may update the UL TA to the SCG based on the TA increment value and may restart a timer associated with the SCG or restart a time value associated with the SCG (450). Additionally, based on the updated UL TA to the SCG, the WTRU may transmit one or more subsequent UL signals to the network via the SCG (460).

[0132] In one exemplary method, the WTRU may be configured with a conditional SRS configuration that configures the WTRU to send one or more additional SRSs to the SCG if the WTRU receives a TA increment value. Similarly, the WTRU may be configured with a conditional SRS configuration that configures the WTRU to send one or more additional SRSs to the SCG if the WTRU receives a TA increment value.

[0133] In another exemplary method, the WTRU may be configured with a conditional SRS configuration that configures the WTRU to send one or more additional SRS to the SCG if the WTRU receives an explicit or implicit out-of-sync indication that does not include a TA increment value. Similarly, the WTRU may be configured with a conditional SRS configuration that configures the WTRU to send one or more additional SRS to the SCG if the WTRU receives an explicit or implicit out-of-sync indication that does not include a TA increment value.

[0134] In yet another exemplary method, after the WTRU has restarted running the TAT after applying the TA increment, the WTRU may operate in the same manner as it did immediately after SCG deactivation or receiving the UL signal configuration. For example, when a certain percentage (e.g., x%) of the TAT has passed, the WTRU may send the UL signal again.

[0135] Examples of selecting between SRS and RACH preamble signals based on downlink measurements are provided herein. The WTRU may maintain its SCG measurements during its SCG deactivation or sleep period. Since downlink measurements (e.g., RRM, radio link monitoring (RLM), etc.) may still be running, an assumed in-sync / out-of-sync estimate may be made and scaled based on the measurement interval (e.g., RLM in the case of DRX). The assumed in-sync and out-of-sync monitoring conditions for the UL synchronization signal selection method may be limited to a specific evaluation time window (e.g., the current RLM process), or based on the last available SCG measurement relative to a threshold.

[0136] During this SCG measurement process, and based on the defined in-sync / out-of-sync thresholds, the WTRU may select the UL signal according to the following rules: If the WTRU SCG measurement indicates that the WTRU is in assumed in-sync state, the WTRU may select the SRS signal to perform UL transmission for UL synchronization maintenance and follow any network responses described in the above paragraphs.

[0137] If the WTRU SCG measurements indicate that the WTRU is in a presumed out-of-sync state, the WTRU may select the RA method for UL synchronization maintenance and follow any network responses described in the above paragraphs.

[0138] Examples of scaling TAT based on WTRU mobility are provided herein. In one method, the WTRU is configured to scale TAT based on its mobility, its speed, or both. For example, the WTRU may be configured to increase the TAT value if the WTRU decreases its speed or stops moving, or to shorten the TAT if the WTRU increases its speed or starts moving.

[0139] Although features and elements are described above in specific combinations, it will be understood by those of ordinary skill in the art that each feature or element may be used alone or in any combination with other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via a wired or wireless connection) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media (such as built-in hard disks and removable disks), magneto-optical media, and optical media (such as CD-ROM disks and digital versatile disks (DVDs)). A processor associated with software may be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A method for use in a wireless transmit / receive unit (WTRU), the method comprising: receiving indication information from a first node, the indication information indicating a UL configuration of one or more first uplink (UL) signals; transmitting the one or more first UL signals to a second node; receiving, via the first node, a synchronization indication from the second node; based on receiving the synchronization indication from the second node, wherein the synchronization indication from the second node includes timing advance (TA) information, updating a UL TA to the second node based on the TA information; as well as One or more second UL signals are transmitted to the second node using the updated UL TA to the second node.

2. The method of claim 1, wherein the TA information is a timing advance command (TAC) and includes a TA increment value. The method of claim 1 , wherein the in-sync indication is one of an in-sync indication or an out-of-sync indication.

4. The method according to claim 3, further comprising: Based on receiving the synchronization indication, a time value associated with the second node is restarted.

5. The method according to claim 3, further comprising: Based on receiving the out-of-sync indication from the second node, stopping running a time value associated with the second node and deeming the second node out of sync with the WTRU, wherein the out-of-sync indication from the second node does not include a TA increment value.

6. The method according to claim 1, further comprising: Running the time value associated with the second node includes one of starting to run the time value associated with the second node or maintaining running the time value associated with the second node.

7. The method according to claim 4, further comprising: Based on the time value associated with the second node, UL data is transmitted to the second node without using a random access (RA) procedure.

8. The method of claim 1, wherein the one or more first UL signals comprise a random access channel (RACH) preamble. 9 . The method according to claim 1 , wherein the indication information further indicates one or more trigger conditions for transmitting the first UL signal, wherein the one or more trigger conditions for transmitting the one or more first UL signals include timing information.

10. The method of claim 9, wherein transmitting the one or more first UL signals to the second node is based on the UL configuration and satisfaction of the one or more triggering conditions for transmitting the one or more first UL signals.

11. A wireless transmit receive unit (WTRU), the WTRU comprising: Transceiver; and a processor operatively coupled to the transceiver; wherein: The transceiver is configured to receive indication information from a first node, the indication information indicating a UL configuration of one or more first uplink (UL) signals; The processor and the transceiver are configured to transmit the one or more first UL signals to a second node; The transceiver is configured to receive a synchronization indication of the second node via the first node; The processor and the transceiver are configured to, based on receiving the synchronization indication of the second node, wherein the synchronization indication of the second node includes timing advance (TA) information, update the ULTA to the second node based on the TA information; and The processor and the transceiver are configured to transmit one or more second UL signals to the second node using the updated UL TA to the second node.

12. The WTRU of claim 11, wherein the TA information is a timing advance command (TAC) and includes a TA increment value.

13. The WTRU of claim 11, wherein the synchronization indication is one of an in-sync indication or an out-of-sync indication.

14. The WTRU of claim 13, wherein the processor and the transceiver are further configured to restart a time value associated with the second node based on receiving the synchronization indication.

15. The WTRU of claim 13, wherein the processor and the transceiver are further configured to, based on receiving the out-of-sync indication from the second node, stop running a time value associated with the second node and consider the second node to be out of synchronization with the WTRU, wherein the out-of-sync indication from the second node does not include a TA increment value.

16. The WTRU of claim 11, wherein the processor is further configured to run the time value associated with the second node, including starting to run the time value associated with the second node or maintaining running the time value associated with the second node.

17. The WTRU of claim 14, wherein the processor and the transceiver are further configured to transmit UL data to the second node without using a random access (RA) procedure based on the time value associated with the second node.

18. The WTRU of claim 11, wherein the one or more first UL signals include a random access channel (RACH) preamble.

19. The WTRU of claim 11, wherein the indication information further indicates one or more trigger conditions for transmitting the first UL signal, wherein the one or more trigger conditions for transmitting the one or more first UL signals include timing information.

20. The WTRU of claim 19, wherein transmitting the one or more first UL signals to the second node is based on the UL configuration and satisfaction of the one or more triggering conditions for transmitting the one or more first UL signals.

21. A method for use in a wireless transmit / receive unit (WTRU), the method comprising: receiving configuration information about a sounding reference signal (SRS) used with a secondary cell group (SCG) from a network via a primary cell group (MCG); as well as The SRS is transmitted to the network via the SCG.

22. The method according to claim 21, further comprising: A channel quality indicator (CQI) for the MCG is transmitted to the network via the SCG.

23. The method according to claim 21, further comprising: A channel quality indicator (CQI) for the SCG is transmitted to the network via the MCG.

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