Device operation mode change

Abstract

A method for a wireless device includes determining to transition into a low-power mode in a network and sending a request message to the network requesting a change to operate in the low-power mode. The wireless device receives a response message from the network indicating the wireless device may transition to the low-power mode and the wireless device transitions to the low-power mode based on the received response message. The device may further receive a requested action signal from the network indicating the wireless device should transition from the low-power mode to perform an action. The device sends a request response signal indicating whether the wireless device will perform the action of the requested action signal and transitioning from low-power mode to perform the action. Messages to and from the device in low-power mode may use backscattering transmissions. Additional embodiments are disclosed.

Description

DEVICE OPERATION MODE CHANGECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 583,490, filed September 18, 2023, the contents of which are incorporated herein by reference.BACKGROUND

[0002] A device such as a smart phone may be capable of operating in a low-power mode and a “normal” mode. In the low-power mode, the device may only communicate with the network via back-scattering methods. In the low-power mode, the device will not listen for paging from the network. Such a device may switch into this low-power mode, for example, when its battery level is less than a certain threshold For example, the device may switch out of this low-power mode and into “normal” mode when its battery is sufficiently charged. In normal mode, the device may be capable of reading the paging channel, sending and receiving non-access stratum (NAS) messages, and / or sending and receiving data via a protocol data unit (PDU) session.

[0003] Third Generation Partnership Program (3GPP) system enhancements are desired to support how a device determines to switch between low-power and “normal” modes. Since the device does not listen to the paging channel when operating in low-power mode, the network needs to be aware of whether the device is in low-power mode or “normal” mode, because, when operating in low-power mode, if downlink data needs to be sent to the device, the downlink data delivery attempt will fail since the device is not listening to the paging channel. Thus, 3GPP system enhancements are desired to support: (I) how a client device, such as a user equipment (UE), determines to switch between low-power and “normal” modes; (ii) how the network determines whether the device is in low-power or “normal” mode; and / or (iii) how the network can attempt to change the device’s operating mode from low-power to "normal” mode when desired or needed.SUMMARY

[0004] Aspects, features and advantages of the disclosed embodiments may address one or more of the foregoing needs including how a device can determine to change what operating mode it is using and communicate this decision to the network In other aspects, embodiments are disclosed for how and why the network (e.g., the access and mobility management function (AMF)) may decide to request that the UE change what operating mode the device is using.

[0005] Whether the change of operation mode is initiated by the device or the AMF, the mode change may be triggered when a change in device power level, roaming status, or location is detected. Furthermore, the change by be triggered by the device when a user of the device requests that the device change the device’s operating mode. According to certain aspects, the user may use a graphic user interface (GUI), attention (AT) Command or application programing interface (API) to request the change in mode of operation.

[0006] According to one aspect, a wireless device (e.g. a user equipment (UE), also referenced herein as a wireless transmit receive unit (WTRU)), may operate in an ambient low-power mode where it cannot independently transmit a signal and it can only reflect received signals via back-scattering. The device may receive an indication that it should transition out of the low-power state so that the device can receive or transmit data from or to the network. The format of the received signal indicates to the device if the device should listen to a paging channel in idle mode or send a service request to the network in connected mode.

[0007] In one example, a method for a wireless transmit receive unit (WTRU) may generally include transitioning to an ambient low-power mode based on an indication received from a network. When the network desires to send or receive data the network sends, and the WTRU receives, a first signal having a first format indicating the WTRU should transition from the ambient low-power mode to perform a requested action. In response to the first signal, the WTRU may send a second signal, which may be generated by a reflection of the first signal, and having a second format indicating the WTRU will or will not perform the requested action. In some examples, the first signal may further indicate one or more of: how much downlink data needs to be sent to the WTRU, that data will need to be sent from the WTRU and how long the WTRU will need to stay in the CM-CONNECTED state. According to one aspect, the received first signal and is a backscattering transmission and the second signal is generated by WTRU reflecting the backscattering transmission.

[0008] In response to receiving the first signal, the WTRU may also transition from the ambient low-power mode and perform the requested action which, as an example, may include one of transitioning to a connection management idle (CM-IDLE) state to listen to a paging channel or transitioning to a connection management connected (CM-CONNECTED) state to initiate a non-access stratum (NAS) service request procedure

[0009] In certain aspects, prior to transitioning to the ambient low-power mode, the WTRU makes a determination to enter into the ambient low-power mode and sends a request message to the network requesting to operate in the ambient low-power mode. When the WTRU receives a response message from the network indicating he WTRU may transition to the ambient low-power mode, the WTRU may enter the ambient low-power mode. In one aspect, the request and response messages are NAS messages exchanged with an access and mobility management function (AMF). In another aspect, the response message may also an indication of a duration of time the WTRU may remain in ambient low-power mode.

[0010] According to various aspects, the determination to transition into the ambient low-power is based on one or more of a battery level of the WTRU being below a threshold, a detected time of day, detected congestion of the network, a location of the WTRU, a roaming status of the WTRU, or a user’s input via a graphical user interface (GUI) or ATtention command (AT).

[0011] According to different aspects, a network node / function (e.g., access and mobility management function (AMF)) may determine when a device should enter the low-power state and initiate a procedure to trigger the device to leave the low-power state when mobile terminated (MT) data needs to be sent to the device. The AMF may receive an indication from the device that the device cannot leave the low-power state(e g. due to low battery) and indicate to another network function (e.g. the session management function (SMF)) that data cannot be sent to the device.

[0012] In one example, a network node including a network function, such as an AMF, may determine that a WTRU in a wireless network should switch to an ambient low-power mode and send a message indicating the WTRU should transition to the ambient low-power mode. Next, the AMF may receive a request from a session management function (SMF) to activate user plane (UP) resources for the WTRU to receive downlink data and the AMF sends a base station a backscattering transmission request for the WTRU to transition from the ambient low-power mode and perform a requested action. The AMF receives from the base station, a backscattering transmission response including information the base station received from the WTRU in response to a backscattering signal sent by the base station to the WTRU.

[0013] In one aspect, the backscattering transmission request indicates one or more of: (i) an amount of the downlink data to be received by the WTRU; (ii) that uplink data will be required to be sent by the WTRU; and / or (iii) how long the WTRU may need to stay in a connected mode In another aspect, determining that the wireless device should switch to the ambient low-power mode may be based on one or more of: (i) receiving a mode change request message from the WTRU; (ii) detecting a location of the wireless device; (iii) determining a roaming status of the WTRU; and / or (iv) detecting network congestion.

[0014] In another aspect, the backscattering transmission response from the base station includes an indication that the WTRU will not exit the ambient low-power mode, and AMF sends indication that the WTRU is unavailable to receive the downlink data to the SMF. In other aspects, the requested action by the AMF is that the WTRU should transition to a CM-IDLE state and begin to listen to a paging channel or that the WTRU should transition to a CM-CONNECTED state and initiate a Service Request procedure in order to receive the downlink data indicated by the SMF. Additional aspects, advantages and / or features are also disclosed in the detailed embodiments that follow.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, wherein like reference numerals in the figures indicate like elements, and wherein:

[0016] FIG. 1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented;

[0017] FIG. 1 B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A according to an embodiment;

[0018] FIG. 1C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communications system illustrated in FIG. 1A according to an embodiment;

[0019] FIG. 1D is a system diagram illustrating a further example RAN and a further example CN that may be used within the communications system illustrated in FIG. 1A according to an embodiment;

[0020] FIG. 2 is a flow chart detailing a method implemented by a wireless transmit receive unit (WTRU) to change between a low-power mode and a “normal mode” according to an embodiment;

[0021] FIG. 3 is a flow diagram detailing a method for a network function to change a WTRU between a low-power mode and a “normal mode” according to one embodiment; and

[0022] FIG. 4 is a network message sequence diagram detailing example embodiments of the disclosure.DETAILED DESCRIPTION

[0023] FIG. 1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), singlecarrier FDMA (SC-FDMA), zero-tail unique-word discrete Fourier transform Spread OFDM (ZT-UW-DFT-S- OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0024] As shown in FIG. 1A, the communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though itwill be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a station (STA), may be configured to transmit and / or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fl device, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c and 102d may be interchangeably referred to as a UE.

[0025] The communications systems 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at leastone 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 the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a NodeB, an eNode B (eNB), a Home Node B, a Home eNode B, a next generation NodeB, such as a gNode B (gNB), a new radio (NR) NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0026] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, and the like. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum A cell may provide coverage for a wireless service to a specific geographical area that may be relatively fixed or that may change over time. The cell may further be divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in desired spatial directions.

[0027] 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).

[0028] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 116 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed Uplink (UL) Packet Access (HSUPA).

[0029] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0030] 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.

[0031] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for instance using dual connectivity (DC) principles. Thus, the air interface utilized by WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g , an eNB and a gNB).

[0032] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e , Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0033] The base station 114b in FIG 1A may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a roadway, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not be required to access the Internet 110 via the CN 106.

[0034] 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 varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not shown in FIG. 1 A, 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 be utilizing a NR radio technology, the CN 106 may also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0035] The CN 106 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or the other networks 112. The PSTN 108 may include circuit-switched telephone networks that provide plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and / or the internet protocol (IP) in the TCP / IP internet protocol suite. The networks 112 may include wired and / or wireless communications networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

[0036] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1 A may be configured to communicate with the base station 114a, which may employ a cellularbased radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0037] FIG. 1 B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1 B, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138, among others. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0038] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1 B depicts the processor 118 and the transceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0039] The transmit / receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In an embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0040] Although the transmit / receive element 122 is depicted in FIG. 1 B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0041] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit / receive element 122 and to demodulate the signals that are received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11 , for example.

[0042] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit) The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and / or the removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0043] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li- ion), etc.), solar cells, fuel cells, and the like.

[0044] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station (e.g., base stations 114a, 114b) and / or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by way of any suitable location-determination method while remaining consistent with an embodiment

[0045] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellitetransceiver, a digital camera (for photographs and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a Virtual Reality and / or Augmented Reality (VR / AR) device, an activity tracker, and the like. The peripherals 138 may include one or more sensors. The sensors may be one or more of a gyroscope, an accelerometer, a hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, a humidity sensor and the like.

[0046] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e g., associated with particular subframes for both the UL (e.g., for transmission) and DL (e.g., for reception) may be concurrent and / or simultaneous. The full duplex radio may include an interference management unit to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e g., for transmission) or the DL (e g., for reception)).

[0047] FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the ON 106.

[0048] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0049] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, and the like. As shown in FIG. 1 C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0050] The ON 106 shown in FIG. 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. While the foregoing elements are depicted as part of the ON 106, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0051] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticatingusers of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA

[0052] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring user planes during inter-eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0053] 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.

[0054] The ON 106 may facilitate communications with other networks For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers.

[0055] Although the WTRU is described in FIGS. 1A-1 D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (e.g., temporarily or permanently) wired communication interfaces with the communication network.

[0056] In representative embodiments, the other network 112 may be a WLAN.

[0057] A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic in to and / or out of the BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA The traffic between STAs within a BSS may be considered and / or referred to as peer-to-peer traffic. The peer-to- peer traffic may be sent between (e.g., directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11e DLS or an 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (e.g., allof the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an “ad-hoc” mode of communication.

[0058] When using the 802.11 ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width. The primary channel may be the operating channel of the BSS and may be used by the STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example in 802.11 systems. For CSMA / CA, the STAs (e.g., every STA), including the AP, may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0059] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0060] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels The 40 MHz, and / or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels, or by combining two noncontiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately The streams may be mapped on to the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0061] Sub 1 GHz modes of operation are supported by 802.11 af and 802.11 ah. The channel operating bandwidths, and carriers, are reduced in 802.11 af and 802.11ah relative to those used in 802.11n, and 802.11ac. 802.11 af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11 ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11 ah may support Meter Type Control / Machine- Type Communications (MTC), such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, for example, limited capabilities including support for (e.g , only support for) certain and / or limited bandwidths The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0062] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802 11 n, 802.11ac, 802.11 af, and 802.11 ah, include a channel which may be designated as the primary channel. Theprimary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11 ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 1 MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) settings may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which supports only a 1 MHz operating mode) transmitting to the AP, all available frequency bands may be considered busy even though a majority of the available frequency bands remains idle.

[0063] In the United States, the available frequency bands, which may be used by 802.11 ah, are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11 ah is 6 MHz to 26 MHz depending on the country code.

[0064] FIG. 1 D is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an 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.

[0065] The RAN 104 may include gNBs 180a, 180b, 180c, though 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 one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0066] The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing a varying number of OFDM symbols and / or lasting varying lengths of absolute time).

[0067] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without also accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with / connect to gNBs 180a, 180b, 180c while also communicating with / connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In the non- standalone configuration, eNode-Bs 160a, 160b, 160c may serve as a mobility anchor for WTRUs 102a, 102b, 102c and gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for servicing WTRUs 102a, 102b, 102c.

[0068] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support of network slicing, DC, interworking between NR and E-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG. 1D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0069] The CN 106 shown in FIG. 1 D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0070] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of non-access stratum (NAS) signaling, mobility management, and the like. Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types of services being utilized WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for MTC access, and the like 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.

[0071] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 106 via an N11 interface. The SMF 183a, 183b may also be connected to a UPF 184a, 184b in the CN 106 via an N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP address, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, and the like. A PDU session type may be IP-based, non-IP based, Ethernet-based, and the like.

[0072] 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, and the like.

[0073] 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 the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local DN 185a, 185b through the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0074] In view of FIGs. 1A-1 D, and the corresponding description of FIGs. 1A-1 D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b, and / or any other device(s) described herein, may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more, or all, of the functions described herein. For example, the emulation devices may be used to test other devices and / or to simulate network and / or WTRU functions.

[0075] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or in an operator network environment. For example, the one or more emulation devices may perform the one or more, or all, functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. The one or more emulation devices may perform the one or more, or all, functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network The emulation device may be directly coupled to another device for purposes of testing and / or performing testing using over-the-air wireless communications.

[0076] The one or more emulation devices may perform the one or more, including all, functions while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communications via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0077] Embodiments for low-power mode initiation and termination of a WTRU will now be described. As used herein, the terms “low-power mode (LPM),” “ambient mode,” “ambient low-power mode” and / or “backscattering mode (BM)” may be used interchangeably in this disclosure. A LPM according to the embodiments disclosed herein refer to a device in a mode which is not capable of reading the paging channel and / or sending and receiving NAS messages. Furthermore, the terms “operation mode” and “operating mode” may be used interchangeably in this disclosure Examples of operating modes are low-power mode and normal mode. As used herein, normal mode refers to a state where the WTRU may listen to a paging channel and be capable of sending and receiving data via a PDU session and / or NAS messaging. The terms UE, WTRU and device may be used interchangeably in described embodiments.

[0078] Registration Request, Registration Reject, Registration Accept, Service Request, Service Reject, and Service Accept are all types of Non-Access Stratum Mobility Management (NAS-MM) messages. A NAS- MM message may be a message that is sent from a WTRU to an access and mobility management function (AMF) or a message that is sent from an AMF to a WTRU.

[0079] Ambient loT Device Types There are three types of ambient devices presently discussed. The first type of device is called a Type-A device. A Type-A device has no energy storage and no independent signal generation, i.e., it transmits by using backscattering transmission.

[0080] The second type of device is called a Type-B device A Type-B device has energy storage but does not have the capability to perform independent signal generation, i.e., it transmits by using backscattering transmission. Use of stored energy can include amplification for reflected signals.

[0081] The third type of device is called a Type-C device. A Type-C device has energy storage and has the ability to perform independent signal generation, i.e., the device has active RF components for transmission.

[0082] Network Triggered Service Request When a WTRU is in connection management (CM)-IDLE mode and the network has downlink data to send the WTRU, the network will page the WTRU. Receiving the page will cause the WTRU to send a Service Request message to the network, to enter the CM-CONNECTED state and receive the downlink data. Examples of downlink data are NAS messages, Mobile Terminated (MT) short message service (SMS), and user plane (UP) data. Note that when the WTRU is in CM-IDLE mode it needs to listen to the paging channel so that it can detect that a service request message needs to be sent by the WTRU.

[0083] As mentioned previously, a device such as a smart phone may be capable of operating in an ambient low-power mode and a “normal” mode. In the ambient low-power mode, the device may only communicate with the network via back scattering methods. In the ambient low-power mode, the device will not listen for paging from the network. Such a device may switch into this ambient low-power mode, for example, when its battery level is low. For example, the device may switch out of this mode and into “normal” mode when its battery is sufficiently charged. In normal mode, the device may be capable of reading the paging channel, sending and receiving NAS messages, and sending and receiving data via a PDU Session. 3GPP System enhancements are desired to support how the device determines to switch between ambient low-power and “normal” modes.

[0084] Furthermore, since the device does not listen to the paging channel when operating in ambient low- power mode, the network needs to be aware of whether the device is in low-power mode or “normal” mode. The network needs to be aware of whether the device is operating in low-power mode because, if downlink data needs to be sent to the device, the downlink data delivery attempt will fail since the WTRU is not listening to the paging channel. Thus, 3GPP System enhancements are desired to support how the network determines whether the device is in and ambient low-power mode or “normal” mode. In order to account for the case where the device is in ambient low-power mode and downlink data or control signaling needs to be sent to the device, 3GPP System enhancements are also needed so that the network can attempt to change the device’s operating mode from ambient low-power to “normal” mode.

[0085] A device may operate in an ambient low-power mode where the device may only communicate with the network via back scattering methods. In the low-power mode, the device will not listen for pages from the network. In the low-power mode, the device’s Connection Management (CM) state may be CM-IDLE. In the low-power mode, the device’s Registration Management (RM) state may be RM-REGISTERED. Alternatively, a device may also operate in the low-power mode when in the RM-DEREGISTERED state.

[0086] Example embodiments discussed herein may relate to how a device can determine to change what operating mode it is using and communicate this decision to the network. Furthermore, the following embodiments disclose how and / or why the network (e.g., the AMF) may decide to request that the device change what operating mode the device is using.

[0087] Whether the change of operation mode is initiated by the device or the AMF, the mode change may be triggered when a change occurs, e.g., in device power level, roaming status, or location is detected. Furthermore, is some examples, the change may be triggered by the device when a user of the device requests that the device change the device’s operating mode. For example, in various embodiments, the user may use a GUI, AT Command or application program interface (API) to request the change in operating mode.

[0088] Referring to FIG. 2, an example method 200 is shown for a WTRU changing operation between a normal mode (NM) and an ambient low-power mode (LPM) according to one embodiment. In method 200, the WTRU may determine 205 to switch its mode to a LPM. In one example, determination 205 may be based the on the battery level being below a threshold level, or for example, based on detecting a time of day or nightwhen data connection to a network may generally be low or zero. In other examples, the device may make the determination 205 to enter LPM based on detecting network congestion, the location of the WTRU, the device’s roaming status and / or based on a user request, e.g., via a graphic user interface (GUI) or ATtention (AT) commands.

[0089] In this example embodiment, the WTRU may next transmit 210 a message to a network, e.g., a network node including a network function such as an AMF, or a base station, indicating that the device is requesting to change to the ambient low-power mode. In one example, the message may also include a reason why the device is requesting to change to low-power mode, e.g., battery level, time of day, etc. In one example, the message may be a non-access stratum (NAS) message to the AMF such as a Registration Request message.

[0090] In response, the WTRU may receive 215 a mode change response message sent by the network indicating that the device may transition to ambient low-power mode (LPM). In one example, this response message may be a NAS message such as a Registration Accept message from the AMF, and may include additional indications regarding the WTRU’s LPM, such as how long the device may stay in ambient low-power mode, one or more locations where the device is allowed to operate in ambient low-power mode and / or other information which may be pertinent to allowing / limiting the WTRU operation in LPM. Based on receiving the indication that the WTRU may transition to LPM, the WTRU transitions 220 to the ambient low-power mode.

[0091] The WTRU continues in LPM and may receive 225 a signal, whose format indicates that the device is requested to perform an action As one example, the requested action may be that the device should transition to the CM-CONNECTED state and initiate a Service Request procedure. In another example, the requested action may be that the device should transition to the CM-IDLE state and begin to listen to the paging channel. In yet a further example, the requested action may be that the device should transition to the CM- CONNECTED state and initiate a Service Request procedure in order to send uplink data.

[0092] In certain embodiments, the device may transmit a response to the received signal action request. In one example, the response signal may be generated by reflecting the received signal action request. In one example, the format of the response signal may indicate whether the device will attempt to perform the requested action.

[0093] Next, the device may stop operating in the ambient low-power mode where the determination to stop operating in low-power mode may be based on receiving the signal that requests that the device perform an action. In method 200, the action request 225 prompts the device to exit LPM and send 230 a NAS Service Request procedure to the network. The device may trigger the NAS Service Request procedure based on receiving the message that requests that the device perform an action or based on receiving a paging message. Method 200 is merely an illustrative example and steps shown or described may be modified, added, omitted and / or combined with any other method described herein.

[0094] Referring to FIG. 3, an example method 300 is shown for changing a low-power operation mode of a WTRU by a network node, e.g., a network node having a network function such as the AMF, via an N1 interface through a gNB. The network may determine 305 to indicate to a device that the device should switch to ambient low-power mode (LPM). In one example, the determination 305 by the network may be triggered by previously receiving a message from the device that indicates that the device requests to operate in low- power mode. In other examples, the determination by the network may be triggered by the network detecting the device’s location, the device’s roaming status, or detecting network congestion.

[0095] Based on determination 305, the network function sends 310 an indication to the device to transition to low-power mode. If / when 315, the network function, e.g., AMF, receives a request from a session management function (SMF) to activate user plane (UP) resources for the device, the network determines to transmit 320 a signal, e.g., an action request signal, indicating that the device should transition out of the ambient low-power mode. In certain embodiments, this signal may further indicate that downlink data needs to be sent to the device. In some examples, the signal may indicate: (i) how much downlink data needs to be sent to the device; (ii) that data will need to be sent from the device; and / or (iii) how long the device will need to stay in the CM-CONNECTED state. As mentioned in the previous embodiment, the format of the signaling from the network may provide the described indication(s) to the device.

[0096] In response to receiving the action request signaling from the network, the device may exit 330 low- power mode (LPM). Alternatively, if / when 325 the network function may receive an indication from the device, e.g., via backscattering, or the network makes its own determination, that the device will not exit low-power mode, and the network function sends 335 a message to the SMF that indicates that the device is not reachable / unable to exit LPM. Method 300 is merely an illustrative example and steps shown or described may be modified, added, omitted and / or combined with any other method described herein

[0097] Turning to FIG. 4, an example method 400 is shown for operation mode changing of a device in a network between a normal mode and an ambient low-power mode according to one embodiment. Entities involved in method 400 may include one or more of a device / UE / WTRU, an access network (AN) such as a radio access network (RAN), an access and mobility management function (AMF), a session management function (SMF), an authentication server function (AUSF), unified data management (UDM)Zunified data repository (UDR) functions and. / or a user plane function (UPF). The functions described are logical entities and may be individually located at a network node, or co-located with other network functions, depending on the specific network architecture involved.

[0098] In one example described, the device may indicate to the network that the device supports operation mode changes, and the network responds to the device. The network’s response to the device may indicate whether the device is permitted to initiate operation mode changes. The example method 400 of FIG. 4 shows a series of steps, e.g., 402 through 428, that the network and device may perform when downlink data needs to be sent to the device when the device is operating in normal mode. The example method 400 also shows a series of steps, e.g., 430 through 440, that the network and device may use in switching the device to a “low-power” mode. Example 400 further shows a series of steps, e.g., 442 through 466 that the network and device may use when downlink data needs to be sent to the device when the device is operating in “low-power” mode.

[0099] In one embodiment, an indication that the device supports operation mode changes may be sent 402 to the network, e.g., to the AMF in a Registration Request message, although the operation mode change capability indication may be sent in any uplink NAS transport message. In this example, the network may send 408 the device information about whether the device is permitted to initiate operation mode changes, e g., in a Registration Response / Accept message or any downlink NAS transport message

[0100] In one example, the device may determine to send an indication to the network that the device would like to transition from a low-power mode to a normal mode. Additionally, or alternatively, the device may determine to send an indication to the network to indicate that the device would like to transition from a normal mode to a low-power mode.

[0101] The device may determine to change modes based on detecting one or more events or conditions. One example condition, or event, that may trigger the device to determine to change modes is detecting the amount of energy stored in the device (e.g. in the device’s battery or capacitor) has passed a threshold. For example, the device may determine to transition to low-power mode when the amount of energy stored in a battery is below a threshold. Another example condition, or event, that may trigger the device to determine to change modes is detecting that the device has registered in a particular public land mobile network (PLMN) or location. For example, the PLMN may be a visited PLMN (VPLMN) and the device may be considered to be roaming. The location may be a location where the device’s agreement with the operator states that the WTRU should not consume certain types, or amounts, of network resources. The device may be configured to transition to a low-power mode when the device is registered in certain PLMNs, whenever the device is roaming, or when the device is in certain locations. One advantage of transitioning to a low-power mode when in certain PLMN(s), in certain locations, or when roaming, is that the device may consume less network resources while, at the same time, the device’s presence and location in the network may be known to a degree that is greater than if the device was not registered.

[0102] In some examples, the device might request to change the operation mode back to “normal” mode because the device has determined to initiate a procedure that cannot be performed in low-power mode. For example, it may not be possible to perform a service request procedure and receive downlink data in low-power mode. For example, it may not be possible to transmit / receive data, or large amounts of data in low-power mode and the device may determine to enter normal mode because of the amount of data that needs to be transmitted / received.

[0103] In other examples, the device might request to change the operation mode back to “normal” mode based on receiving an indication from the network that the network requests the device to enter, or use, normal mode. The device might request to change the operation mode back to “normal” mode based a timer expiring. For example, the device may have been configured to stay in low-power mode only for a limited time duration.

[0104] When the AMF receives a request from the device to change the device’s operation mode, the AMF may use one or more pieces of information to determine whether to allow a change in the device’s operation mode. One example of information that the AMF may use to determine whether to allow a change in the device’s operation mode is the device’s subscription information. For example, the AMF may receive the device’s subscription information from the UDM / UDR and the subscription information may indicate what operation modes the device is allowed to use.

[0105] Another example of information that the AMF may use to determine whether to allow a change in the device’s operation mode is the device’s location. For example, the AMF may determine that the device should not operate in low-power mode in the device’s current location. The AMF may determine that the device should not operate in low-power mode in the device’s current location because it is unlikely that the network would be able to use backscattering techniques to initiate communication in the device’s current location. The network might be unlikely to be able to use backscattering techniques to initiate communication with the device in the device’s current location because the equipment necessary for communicating via backscattering methods might not be installed near the device’s current location. For example, the AMF may determine that the device should operate in low-power mode in the device’s current location because the equipment necessary for communicating via backscattering methods is installed near the device’s current location.

[0106] If the AMF decides to allow the device’s request for operation mode change, the AMF may send a message / indication to the device what operation mode the device should use. In one example, the indication may be sent in a Registration Accept message or any DL NAS Transport message.

[0107] Method 400 details an example how to handle the case where downlink data is received for the device when the device is in the “low-power” mode. Method 400 further details an example of how the AMF may trigger the WTRU to leave the “low-power” mode and enter the “normal” mode Once the device has entered the “normal" mode, it may receive the downlink data

[0108] In one example solution, the user plane function (UPF) receives downlink data and sends a downlink data notification to the SMF. The received downlink data notification from the UPF triggers the SMF to notify the AMF that there is a downlink data available for the WTRU. The AMF sends a message towards the access network (AN), the message from the AMF may include the device’s identity, device’s operation mode, information about the device’s last known location, and / or information about the device’s expected current location.

[0109] When the message indicates to the AN that the device is in “low-power” mode, the AN may send a backscattering signal in the area where the device is expected to be located. The format of the backscattering signal may indicate to the device that downlink data needs to be sent to the device. In one example, the format of the backscattering signal may indicate to the device that device should perform a procedure with the network such as a Registration procedure. The device may reflect the received signal back to the AN. In one example, the device may reflect the signal such that the format, or properties, of the reflected signal may indicate to thenetwork if the device is capable of receiving downlink data or performing a procedure with the network. For example, the device may indicate to the network that it is not capable of performing a procedure with the network or receiving downlink data from the network because the device does not have enough energy stored. In one example, the device indicates to the network, e.g., by virtue of the reflected backscattering signal format, that it is capable of performing a procedure with the network or receiving downlink data from the network. When the device is capable of performing a procedure with the network or receiving downlink data from the network, the device may subsequently initiate the procedure (e.g. by sending a Registration Request message) or initiate the reception of downlink data by sending a Service Request message.

[0110] Referring again to FIG. 4, a method 400 for a WTRU initiated operation mode change is shown. Steps 402 through 408 show an example of how a WTRU may indicate its “low-power” capability and preferred operation mode during a registration procedure. Indicating a “low-power” capability may mean that the device sends a “low-power capable” indication to the AMF. The “low-power capable” indication indicates to the AMF that the device is capable of operating in a “low-power” mode. Indicating a “preferred operation mode” may mean that the device sends a “preferred operation mode” indication to the AMF. The ““preferred operation mode” may indicate to the AMF if the device prefers to operate in “low-power” mode or if the device prefers to operate in a “normal” mode.

[0111] In step 402 of FIG. 4, the WTRU sends a NAS Registration Request to the AMF. The request may include the identity of the WTRU, the operation modes (e.g., Normal, Ambient Low-Power) that are supported by the WTRU, and / or the operation mode that the WTRU prefers to use. A Registration Request is one example of NAS message that may be used to send the WTRU’s capabilities and preferred operation modes, although other types of NAS messages may be used to send this information (e.g. an UL NAS Transport Message).

[0112] The AMF may request 404 the device’s subscription data from the unified data management (UDM) / user data repository (UDR) and the AMF receives 406 the device’s subscription data from the UDM / UDR. In one example, the subscription data may indicate to the AMF which operation modes the device is allowed to use. The AMF may then determine what operation mode to indicate that the WTRU should use.

[0113] The determination of what operation mode the WTRU should use may be based on the operation modes that the WTRU indicated that it can support, the operation mode that the WTRU indicated that it prefers to use, and / or the operation mode(s) that the device’s subscription data indicated are supported by the device. In one example, the determination of what operation mode the WTRU should use may also be based on analytics information received from a Network Data Analytics Function (NWDAF) (not shown). For example, analytics from the NWDAF may indicate an expected device trajectory or communication pattern. In another example, the expected device trajectory or communication pattern may be received from the UDM / UDR as part of the device’s subscription information. Combinations of the foregoing information and / or other relevant information to determine what operation mode should be used for the device may also be used

[0114] The AMF may send 408 a response message to the device, e.g., a Registration Response message. In one example, the Registration Response message may be a Registration Accept message and may include an indication of what operation mode in which the device should operate. Alternatively, the Registration Request Response message may be a Registration Reject message and may include an indication that the registration request was rejected because the preferred operation mode that was indicated by the WTRU in step 402 is not supported by the network or not authorized to be used by the device. In the example method 400 of FIG. 4, the AMF may determine and indicate, via the response message, that the device should operate in normal mode and the WTRU may enter 410 the CM-IDLE state.

[0115] Method 400 steps 412 through 428 show an example procedure of how the device may receive downlink data. In this example, the device is operating in “normal mode” and in the CM-IDLE state when the downlink data arrives at the network. Since the device is in normal mode and in the CM-IDLE state, the network is able to page the device in order to trigger the device to transition to the CM-CONNECTED state so that the device can receive the downlink data. For example, at step 412, the user plane function (UPF) receives downlink data for a PDU session of the device and the UPF sends 414 a downlink data notification message to the SMF. A purpose of this message is to notify the SMF that downlink data is available for a PDU Session of the device.

[0116] At step 416, the AMF receives an activate user plane (UP) request from the SMF regarding the downlink data The request indicates to the AMF that downlink data needs to be delivered to the device. Since, in this example, the device is in the CM-IDLE state, the AMF responds 418 to the SMF with an activate UP response that the AMF will attempt to page the device .

[0117] In the example shown, since the WTRU is in a RM-REGISTERED state and a CM-IDLE state, the AMF sends 420 a paging request to the RAN Node, e.g., a base station, of the access network (AN) and the RAN node begins 422 a paging procedure. The paging procedure targets the device and takes place in one or more cell(s) where the WTRU is expected to be located

[0118] Upon receiving the paging request, the device initiates 424 a NAS Service Request procedure and, as a result of the Service Request procedure, at step 426, the device enters the CM-CONNECTED state. The device entering the CM-CONNECTED state triggers the downlink data to be sent 428 from the UPF to the WTRU, e.g., via the RAN node.

[0119] FIG. 4 method 400 steps 430 through 440 show an example procedure of how the WTRU may change operation mode from a “normal” mode to a low-power mode (LPM). In step 430, the device may determine to trigger a change in operating mode from “normal” mode to LPM. There are several options for making the determination 430 including one or more of the following options (1 )-(5):

[0120] (1) Detecting that its battery level is below a threshold;

[0121] (2) Detecting the time of day (For example, a policy that is configured in the device may indicate that the device should preferably operate in low-power mode at certain times. The policy may have been received from the network or entered via a user interface of the device (e.g., a GUI));

[0122] (3) Detecting network congestion (For example, the device may detect network congestion based on a receiving broadcasted information by the RAN Node. In an example, a policy that is configured in the device may indicate that the device should preferably operate in low-power mode under certain congestion conditions and the policy may have been received from the network);

[0123] (4) Detecting or determining the device’s location (For example, a policy that is configured in the device may indicate that the device should / should not preferably operate in low-power mode when the device is in certain locations. The policy may have been received from the network or entered via a user interface of the device (e.g., a GUI). In one example, the policy may indicate that the device should operate in low-power mode when roaming); and / or

[0124] (5) Receiving a user request via an AT Command or a GUI

[0125] At step 432, the device sends an operation mode change request to network The request may include an indication that the device is requesting a change of the device’s operation mode from “normal” mode to “low-power” mode. In one example, the indication may be sent in a Registration Request message. In some embodiments, the request may also indicate the reason the device determined to request to operate in “low- power” mode. For example, the request may indicate one of the reasons that is listed in step 430 (e.g. the device’s batter level is low). The network (e.g., AMF) may use this information in determining whether to allow the device to operate in “low-power” mode (at step 434)

[0126] The AMF determines 434 to change the device’s operation mode to “low-power” mode, which may be triggered by the request that was received from the device in step 432 In some cases, this determination 434 may be triggered by the AMF without receiving an indication, or request, from the device. For example, the AMF may make the determination 434 on its own, e.g., based on detecting the device’s location, the device’s roaming status, detecting network congestion, etc.

[0127] When the AMF receives the request 432, or indication, from the device, the AMF may consider the following information when determining 434 whether to allow the device to transition to low-power mode: (i) the device’s permitted operation modes that are part of the device’s subscription information and were received in step 406; and / or (ii) whether communication in low-power mode is available in the device’s current location or is possible via the RAN node.

[0128] Based on the determination 434, the AMF sends 436 a transmission mode change response message with an indication for the device to operate in low-power mode. If the determination 434 was triggered by the device’s request at step 432, then the indication may be sent in a NAS message such as a Registration Accept Message. If the determination 434 was triggered independent of a device request in step 432, then the indication may be sent in a NAS message such as WTRU Configuration Update command or other type ofmessage / command. In some embodiments, the transmission mode change response message used to indicate the LPM mode change to the device, may also indicate how long the device should operate in low- power mode before transitioning back to a normal power mode of operation. In certain embodiments, the message may alternatively, or additionally, indicate in what locations the device is allowed to operate in low- power mode. For example, the message may indicate that the device should transition to normal mode when entering or leaving an identified location.

[0129] Based on receiving the mode change response 436 to operate in low-power mode, the device transitions 438 to the low-power mode and the AMF considers / updates 440 the status of the device to be in low-power mode. While not shown, the AMF may also update other relevant network entities, as to the LPM status of the device.

[0130] FIG. 4 steps 442 through 462 show an example procedure of how a device in low-power mode may transition to normal power mode to receive downlink data. In the example procedure of steps 442 through 362, the device is initially operating in low-power mode when the downlink data for the device arrives at the network. Since the device is in low-power mode, the network is able to use a backscattering signal to indicate to the device that the network needs to send downlink data to the device. The network may also use the backscattering signal to indicate additional information to the device such as how much data needs to be sent to the device. The additional information may be used by the device to determine whether it is capable of transitioning to normal mode and receive the downlink data.

[0131] In step 442, the UPF receives downlink data for a PDU session of the device and the UPF sends 444 a downlink data notification message to the SMF. A purpose of this message is to notify the SMF that downlink data is available for a PDU Session of the device.

[0132] Next, the SMF sends 446 an activate user plane (UP) request, indicating to the AMF that downlink data needs to be delivered to the device, and the AMF responds 448 to the SMF with an activate UP response indicating that the device is not in the CM-CONNECTED state and that the AMF will attempt to initiate a procedure to transition the device into the CM-CONNECTED state. In step 450, the AMF determines to initiate a procedure to cause the device to leave the low-power state and enter the CM-CONNECTED state so that the device can receive the downlink data. The AMF determines to initiate this procedure based on receiving the indication from the SMF that downlink data needs to be sent to the device and based on determining that that the device is in low-power state in step 440. Alternatively, instead of downlink data from the UPF and SMF in steps 442 through 448, the AMF may determine 450 on its own, to initiate this procedure based on, for example, needing to send a NAS message or mobile terminated (MT) SMS message to the device.

[0133] In one example, to initiate the device change from LPM to NM, the AMF sends 452 an N2 interface message to the RAN Node, i.e., a base station. The N2 message may indicate to the RAN Node that downlink data needs to be sent to the device and, if not already updated to the RAN node, that the device is in low-power mode. In some embodiments, the N2 Message may also include a payload including information that needs tobe sent to the device For example, the payload may indicate: (i) how much downlink data needs to be sent to the device; (ii) that data will need to be sent from the device; and / or (iii) how long the device will need to stay in the CM-CONNECTED state. As shown in FIG. 4, the message sent 452 from the AMF may be referred to as a request for backscattering transmission.

[0134] At step 454, the RAN Node sends a signal to the device. Based on its own status information about the device, or receiving an indication that the device is in low-power mode from the AMF, the RAN Node may determine that the type of signal that needs to be sent to the device is a backscattering signal. In some embodiments, the RAN Node signal to the device may carry the payload that was provided by the AMF in step 452. Alternatively, the format of the backscattering signal by the RAN Node may indicate the content of the payload that was received from the AMF. In various embodiments, the format of the backscattering signal may indicate that the device should: (i) transition to the CM-CONNECTED state and initiate a Service Request procedure in order to receive downlink data (where initiating a Service Request procedure means the device should send a Service Request message); (ii) transition to the CM-IDLE state and begin to listen to the paging channel (e.g., in which the device may then receive a page and initiate a Service Request procedure; and / or (iii) transition to the CM-CONNECTED state and initiate a Service Request procedure in order to send uplink data

[0135] At step 456, the device sends a response message to the RAN Node. In certain embodiments, the response message may be sent by reflecting the signal that was received in step 454. The format of the reflected signal may indicate if the device will comply with any action that was requested in the received request signal. For example, if the request signal of step 454 indicated that the device is requested to leave low-power mode and enter the CM-CONNECTED state, then the response signal that is sent in step 456 may indicate if the device will, or will not, leave low-power mode and enter the CM-CONNECTED state.

[0136] If the device response message of step 454 indicates that the device will not leave low-power mode and enter the CM-CONNECTED state, then the message may additionally indicate a cause value indicating why the device will not leave low-power mode and enter the CM-CONNECTED state. For example, the response message may indicate that the device’s stored energy (i.e., battery level) is too low. In one example, the response message may indicate how long the network should wait, e.g., if the device is charging, before again requesting the device to leave low-power mode and enter the CM-CONNECTED state. The network may use the information about why the device will not leave low-power mode and enter the CM-CONNECTED state to determine how long to wait before again requesting that that device leave low-power mode and enter the CM-CONNECTED state. In the example shown in FIG. 4, the device sends 456 a backscattering response indicating the device will transition to normal mode of operation, e.g., via a backscattering response to the base station

[0137] In step 458, the RAN Node sends an N2 message to the AMF. The N2 message provides information from the device’s response of step 456 to the AMF. For example, the N2 message may indicate tothe AMF that the device’s response indicated that the device will, or will not, exit low-power mode and begin to transition to the normal mode.

[0138] If the device indicated that it will not exit low-power mode and begin to transition to ’’normal mode’’ and the device provided additional information that indicates why the device will not exit low-power mode and begin to transition to ’’normal mode”, then the additional information may be included in the N2 backscattering response message from the RAN Node to the AMF. The AMF may use the information about why the device will not leave low-power mode and will not enter the CM-CONNECTED state to determine how long to wait before again requesting that that device leave low-power mode and enter the CM-CONNECTED state.

[0139] If the device indicated that it will not leave low-power mode and enter the CM-CONNECTED state, the AMF indicates 460 to the SMF that the device is not reachable and optionally an expected next step. The SMF may use this information to determine that the downlink data can be dropped or buffered. Alternatively, if the device indicated that the device will leave low-power mode and enter the CM-CONNECTED state, then this message does not need to be sent at step 460 because the SMF will receive a notification that the device is available in the device-triggered Service Request procedure of later step 464. In step 462, the WTRU transitions from low-power mode and enters the normal mode of operation. The decision to leave low-power mode and enter normal mode may be based on the signal that was received in step 454.

[0140] In order to enter normal mode, the WTRU may send a request to the network. The request includes an indication that the device is requesting change the device’s operation mode from low-power mode to “normal” mode. In one example, the indication by the device may be sent in a Registration Request message. If the device does send an indication to the network, then the device may also receive a response from the network that indicates that the WTRU may transition to normal mode. Alternatively, the device may send no indication to the network and the device-triggered Service Request sent 464 by the device may serve an implicit request to enter the normal state.

[0141] As an alternative to being triggered to transition to normal mode by the message of step 454, in certain embodiments, the device may have determined to transition to normal mode based on a timer expiring, as discussed in previous embodiments. For example, the device may have been configured with a policy that indicates a maximum amount of time that the device should stay in low-power mode and the time value may have been used to configure the timer. In step 464, the device sends a NAS Service Request procedure to the network and the WTRU Triggered Service Request procedure is initiated, which results in the device transitioning to the CM-CONNECTED state. The device may trigger the NAS Service Request procedure based on receiving the message of step 454 or based on receiving a paging message (not shown). In step 466, the downlink data is sent from the UPF to the WTRU via the RAN node.

[0142] In certain alternative embodiments in the example procedure of FIG. 4, the device may be in “normal” mode when communicating with the RAN Node in steps 402, 408, 410, 422, 424, 426, 428, 462, 464 and 466. Also, in the example method 400 of FIG. 4, the device may be in “low-power” mode when communicating withthe same RAN Node in steps, 430, 432, 436, 438, 454, and 456. Thus, in the example method 400 of FIG. 4, the RAN node is capable of communicating with devices that are in normal mode or low-power mode It should be understood that the same principles could be applied to a system where a first type of RAN Node is used to communicate with a device that is normal mode and a second type of RAN Node is used to communicate with a device that is low-power mode. For example, the first type of device may be an NG-RAN node or a gNodeB (gNB). The second type of RAN node may be a RAN node, or even a relay device, that is capable of communicating with devices by using backscattering techniques.

[0143] In step 452, the AMF sends a request to the RAN Node to request that the RAN Node use backscattering techniques to send information to the device. In step 458, the AMF receives a response. It should be understood that the AMF may request that a different Network Function perform steps 452 and 458. For example, a Network Function may perform Mobility Management for low-power devices. Such a Network Function may be called an Ambient loT Mobility Management Function (AIMMF). In these alternative embodiments, the AIMMF may track, or store, the last known location of the device. The AIMMF may use the stored device location information to determine what RAN Node should be used to communicate with the device when the device is in low-power mode.

[0144] In steps 412 and 442 of the example method 400 of FIG. 4, downlink data arrives at the UPF and triggers a downlink data notification Alternatively, the A F may determine that the AMF needs to send a control plane (i.e. , NAS) message to the device and this determination by the AMF may trigger steps 420 or 452.

[0145] In steps 428 and 466 of the example method of FIG. 4, downlink data is sent to the device via a PDU Session. It should be noted that the data may be sent via a Data Radio Bearer (DRB) or a Signaling Radio Bearer (SRB). If a SRB is used to send the data, the data may be carried in a NAS message rather than a PDU session. Method 400 is merely an illustrative example and steps shown or described may be modified, added, omitted and / or combined with any other method described herein.

[0146] Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magnetooptical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

CLAIMSWhat is Claimed:

1. A method for a wireless transmit receive unit (WTRU), the method comprising: transitioning to an ambient low-power mode based on a mode change indication received from a network; receiving, from the network, a first signal having a first format indicating the WTRU should transition from the ambient low-power mode to perform a requested action; sending, to the network in response to the first signal, a second signal having a second format indicating the WTRU will perform the requested action; and in response to receiving the first signal, transitioning from the ambient low-power mode and performing the requested action, wherein the requested action comprises one of transitioning to a connection management idle (CM-IDLE) state to listen to a paging channel or transitioning to a connection management connected (CM-CONNECTED) state to initiate a non-access stratum (NAS) service request procedure2. The method of claim 1, wherein the first signal comprises a backscattering transmission and wherein the second signal is generated by reflecting the backscattering transmission.

3. The method of claim 1 or 2, wherein prior to transitioning to the ambient low-power mode, the method further comprising determining to transition into the ambient low-power mode; sending, to the network, a request message to operate in the ambient low-power mode; and receiving, from the network, a response message including the mode change indication.

4. The method of claim 3, wherein the request message and the response message comprise NAS messages.

5. The method of claim 3 or 4, wherein determining to transition into the ambient low-power mode is based on one or more of a battery level of the WTRU being below a threshold, a detected time of day, a detected congestion of the network, a location of the WTRU, a roaming status of the WTRU, or a user input.

6. The method of any one of claims 3-5, wherein the response message further includes an indication of a duration of time the WTRU may remain in the ambient low-power mode.

7. The method of any one of claims 1-6, wherein the first signal further indicates one or more of: how much downlink data needs to be sent to the WTRU, that data will need to be sent from the WTRU and how long the WTRU will need to stay in the CM-CONNECTED state.

8. A wireless transmit receive unit (WTRU) comprising:a transceiver and a processor operatively coupled to the transceiver, the transceiver and processor configured to: transition to an ambient low-power mode based on a mode change indication received from a network; receive, from the network, a first signal having a first format indicating the WTRU should transition from the ambient low-power mode to perform a requested action; send, to the network in response to the first signal, a second signal having a second format indicating the WTRU will perform the requested action; and in response to receiving the first signal, transition from the ambient low-power mode and perform the requested action, wherein the requested action comprises one of transitioning to a connection management idle (CM-IDLE) state to listen to a paging channel or transitioning to a connection management connected (CM-CONNECTED) state to initiate a non-access stratum (NAS) service request procedure.

9. The WTRU of claim 8, wherein the first signal comprises a backscattering transmission and wherein the second signal is generated by reflecting the backscattering transmission.

10. The WTRU of claim 8 or 9, wherein prior to transitioning to the ambient low-power mode, the transceiver and processor are further configured to: determine to transition into the ambient low-power mode; send, to the network, a request message to operate in the ambient low-power mode; and receive, from the network, a response message including the mode change indication.

11. The WTRU of claim 10, wherein the request message and the response message comprise NAS messages.

12. The WTRU of claim 10, wherein determining to transition into the ambient low-power mode is based on one or more of a battery level of the WTRU being below a threshold, a detected time of day, a detected congestion of the network, a location of the WTRU, a roaming status of the WTRU, or a user input.

13. The WTRU of any one of claims 10-12, wherein the response message further includes indication of a duration of time the WTRU may remain in the ambient low-power mode.

14. The WTRU of any one of claims 8-13, wherein the first signal further indicates one or more of: how much downlink data needs to be sent to the WTRU, that data will need to be sent from the WTRU and how long the WTRU will need to stay in the CM-CONNECTED state.

15. A method for a network node implementing a network function, the method comprising: determining that a wireless transmit receive unit (WTRU) in a wireless network should switch to an ambient low-power mode;sending, to the WTRU, a message including an indication to transition to the ambient low-power mode; receiving a request from a session management function (SMF) to activate user plane (UP) resources for the WTRU to receive downlink data; and sending, to a base station, a backscattering transmission request for the WTRU to transition from the ambient low-power mode and perform a requested action; and receiving, from the base station, a backscattering transmission response including information the base station received from the WTRU in response to a backscattering signal sent by the base station to the WTRU16. The method of claim 15, wherein the backscattering transmission request indicates one or more of: an amount of the downlink data to be received by the WTRU, that uplink data will be required to be sent by the WTRU and how long the WTRU may need to stay in a connected mode.

17. The method of claim 15 or 16, wherein determining that the WTRU should switch to the ambient low- power mode is based on one or more of receiving a mode change request message from the WTRU, detecting a location of the WTRU, determining a roaming status of the WTRU or detecting network congestion.

18. The method of any of claims 15 to 17, wherein the backscattering transmission response includes indication that the WTRU will not exit the ambient low-power mode, and wherein the method further comprises: sending, to the SMF, a message that the WTRU is unavailable to receive the downlink data.

19. The method of any one of claims 15-18, wherein the network function comprises an access and mobility management function (AMF).

20. The method of any one of claims 15-19, wherein the requested action comprises that the WTRU should transition to a connection management idle (CM-IDLE) state and begin to listen to a paging channel or that the WTRU should transition to a connection management connected (CM-CONNECTED) state and initiate a Service Request procedure in order to receive the downlink data.

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