Method for cell reselection with ze radio receiver

Abstract

The invention discloses a method for cell reselection with a ZE radio receiver, and specifically discloses a method for idle mode operation of a wireless transmit / receive unit (WTRU) having a zero energy (ZE) receiver. A WTRU operating in an idle mode may receive an energy harvesting (EH) configuration over a Uu interface for use over a ZE air interface using a primary transceiver. The primary transceiver may be turned off and, as part of ZE idle mode operation, the ZE receiver may detect over the ZE air interface and harvest energy from the ZE reference signal. The WTRU may calculate an amount of energy harvested from the ZE reference signal for a first time period. The WTRU may calculate a ZE idle mode operation energy consumption for a first time period. Under the condition that the ZE idle mode operation energy consumption is greater than the harvested energy, the primary transceiver may be turned on and the WTRU may enter a Uu interface idle mode operation.

Description

[0001] This application is a divisional application of Chinese patent application No. 201980091485.0, whose application date is December 17, 2019 and whose invention name is “Method for cell (re)selection using zero energy (ZE) radio receiver”. The contents of the parent application are incorporated herein by reference.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Application No. 62 / 780,639 filed on December 17, 2018 and U.S. Provisional Application No. 62 / 886,103 filed on August 13, 2019, the contents of which are incorporated herein by reference. Background Art

[0004] A passive receiver or zero energy (ZE) receiver is a type of radio frequency (RF) circuit that can process a received RF waveform without an active power source. For example, such a device can harvest energy from a received RF waveform to run the necessary circuits to process the received signal. A passive receiver can use RF components (e.g., cascaded capacitors, zero bias Schottky diodes, and / or microelectromechanical systems (MEMS)) to implement the functions required for a voltage multiplier or rectifier, a charge pump, and a signal detector. Therefore, when a passive receiver is used in a user device, the reduction in power consumption can be considerable. For example, when the user device stays in idle mode, the power consumption in the user device can be reduced to less than 1 mW.

[0005] A user equipment equipped with a passive receiver can receive a paging message or a wake-up signal when it is in idle mode. Therefore, a user equipment equipped with a passive receiver is expected to support cell measurement or cell (re)selection without incurring expensive power consumption. However, when applied to a user equipment equipped with a passive receiver, the existing cell measurement or cell (re)selection procedures typically used for cellular networks are not suitable. Therefore, there is a need for a method and apparatus that allows a user equipment to efficiently perform cell measurement and cell (re)selection in conjunction with a tracking area update procedure. Summary of the invention

[0006] A method for idle mode operation of a wireless transmit / receive unit (WTRU) with a zero energy (ZE) receiver is disclosed herein. A WTRU operating in idle mode may receive an energy harvesting (EH) configuration for use over a ZE air interface using a primary transceiver over a Uu interface. The primary transceiver may be turned off, and a ZE receiver as part of the ZE idle mode operation may detect a ZE reference signal over the ZE air interface and harvest energy from the ZE reference signal. The WTRU may calculate an amount of energy harvested from the ZE reference signal over a first time period. The WTRU may calculate a ZE idle mode operation energy consumption over the first time period. In the event that the ZE idle mode operation energy consumption is greater than the harvested energy, the primary transceiver may be turned on and the WTRU may enter Uu interface idle mode operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present invention may be understood in more detail from the following description given by way of example in conjunction with the accompanying drawings, in which like reference numerals represent like elements, and in which:

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

[0009] Figure 1B is a diagram showing that according to an embodiment, Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) for use within a communication system is shown;

[0010] Figure 1C is a diagram showing that according to an embodiment, Figure 1A A system diagram of an example radio access network (RAN) and an example core network (CN) used within the communication system shown;

[0011] Figure 1D is a diagram showing that according to an embodiment, Figure 1A A system diagram of another example RAN and another example CN used within the communication system shown;

[0012] Figure 2 A frame format diagram showing an example ZE signal frame format;

[0013] Figure 3 Shown according to Figure 2 FIG. 1 is a diagram of an exemplary multi-tone transmission with a power optimized waveform (POWS) of 1 tone, 4 tones, and 8 tones in a frame format of FIG. 1 ;

[0014] Figure 4A diagram showing an example ZE (wake-up) signal structure and a corresponding energy harvesting profile at a WTRU receiving the ZE signal;

[0015] Figure 5 A state diagram showing an example state machine of a ZE receiver;

[0016] Figure 6 An example of simultaneously transmitting power and information at a WTRU with a ZE receiver is shown;

[0017] Fig. 7A A signaling diagram showing an example ZE transmission format or signature;

[0018] Figure 7B A signaling diagram showing another example ZE transmission format or indicia;

[0019] Figure 7C A signaling diagram showing another example ZE transmission format or indicia;

[0020] Fig.7D A signaling diagram showing another example ZE transmission format or indicia;

[0021] Figure 8 A network diagram of an example communication network 800 is shown, which includes a WTRU equipped with a ZE (passive) receiver, and an example detection sequence when the WTRU processes a known ZE reference transmission format;

[0022] Fig. 9 A network architecture diagram of an example communication network including a WTRU equipped with a cellular transceiver (TRX) and a passive receiver is shown;

[0023] Fig.10 A flow chart illustrating an example WTRU autonomous fallback procedure for idle mode operation using a passive receiver is shown;

[0024] Fig.11 shows a frame format of an example ZE measurement signal frame format with explicit cell ID indication;

[0025] Fig.12 shows a frame format of an example ZE measurement signal frame format with implicit cell ID indication;

[0026] Fig.13A shows a frame format of another example ZE measurement signal frame format with implicit cell ID indication;

[0027] Fig. 13B shows a frame format of another example ZE measurement signal frame format with implicit cell ID indication;

[0028] Fig. 13C shows a frame format of another example ZE measurement signal frame format with implicit cell ID indication;

[0029] Fig.13D shows a frame format of another example ZE measurement signal frame format with implicit cell ID indication;

[0030] Fig.14 shows a flow chart of an example ZE idle mode cell (re)selection process;

[0031] Fig.15 shows a flow chart of another example ZE idle mode cell (re)selection process;

[0032] Fig.16 A flow chart illustrating an example ZE-AI to Uu-AI fallback procedure for a WTRU operating in idle mode with Uu / ZE air interface support;

[0033] Fig.17 A flow chart illustrating another example ZE-AI to Uu-AI fallback procedure for a WTRU operating in idle mode with Uu / ZE air interface support;

[0034] Fig.18 a flow chart showing an example of an idle mode operation determination process; and

[0035] Fig.19 A flow chart illustrating an example of another idle mode operation determination process. DETAILED DESCRIPTION

[0036] Figure 1A 1 is a diagram showing an example communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content by sharing system resources including wireless bandwidth. For example, the communication system 100 may use one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word discrete Fourier transform spread OFDM (ZT-UW-DTS-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, and filter bank multi-carrier (FBMC), etc.

[0037] like Figure 1AAs shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it should be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each WTRU 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. For example, any of the WTRUs 102a, 102b, 102c, 102d may be referred to as a station (STA), which 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 phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices working in an industrial and / or automated process chain environment), consumer electronic devices, and devices working on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, 102d may be interchangeably referred to as UEs.

[0038] The communication system 100 may also include a base station 114a and / or a base station 114b. Each base station 114a, 114b may be any type of device configured to facilitate access to one or more communication networks (e.g., the CN 106, the Internet 110, and / or other networks 112) by wirelessly interfacing with at least one of the WTRUs 102a, 102b, 102c, 102d. For example, the base stations 114a, 114b may be base transceiver stations (BTS), Node Bs, eNode Bs (eNBs), Home Node Bs, Home eNode Bs, Next Generation Node Bs such as gNode Bs (gNBs), New Radio (NR) Node Bs, site controllers, access points (APs), wireless routers, and the like. Although each base station 114a, 114b is depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0039] The base station 114a may be part of the RAN 104, and the RAN may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), a relay node, 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 called cells (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage for a specific geographic area that is relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, a 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, that is, each transceiver corresponds to a sector of the cell. The base station 114a may use multiple-input multiple-output (MIMO) technology and may use multiple transceivers for each sector of the cell. For example, by using beamforming, signals may be transmitted and / or received in a desired spatial direction.

[0040] 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, millimeter wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0041] More specifically, as described above, the communication system 100 may be a multiple access system and may use 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 use Wideband CDMA (WCDMA) to establish the air interface 116. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​UL Packet Access (HSUPA).

[0042] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0043] 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.

[0044] 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 jointly implement LTE radio access and NR radio access (e.g., using dual connectivity (DC) principles). Thus, the air interface used by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0045] 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 (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), and GSM EDGE (GERAN), among others.

[0046] Figure 1AThe base station 114b in the example may be a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may use any appropriate RAT to facilitate wireless connectivity in a local area, such as a business location, a residence, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may establish a wireless local area network (WLAN) by implementing a radio technology such as IEEE 802.11. In an embodiment, the base station 114b and the WTRUs 102c, 102d may establish a wireless personal area network (WPAN) by implementing a radio technology such as IEEE 802.15. In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may establish a picocell or a femtocell by using a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, and the like). Figure 1A As shown, the base station 114b may be directly connected to the Internet 110. Thus, the base station 114b does not need to access the Internet 110 via the CN 106.

[0047] 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 WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, fault tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or may perform advanced security functions such as user authentication. Although in Figure 1A Although not shown, 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 or a different RAT as the RAN 104. For example, in addition to being connected to the RAN 104 employing NR radio technology, the CN 106 may also be in communication with another RAN (not shown) employing GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0048] The CN 106 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer network devices that use common communication protocols, such as TCP, User Datagram Protocol (UDP), and / or IP in the Transmission Control Protocol / Internet Protocol (TCP / IP) Internet protocol suite. The networks 112 may include wired or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, where the one or more RANs may use the same RAT or a different RAT as the RAN 104.

[0049] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0050] Figure 1B is a system diagram showing an example WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a numeric keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It should be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0051] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, 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. Although Figure 1B The processor 118 and the transceiver 120 are described as separate components, however, it should be understood that the processor 118 and the transceiver 120 may also be integrated together in an electronic component or chip. Although not shown in FIG. 1, the transceiver 120 may include a passive transceiver (or passive receiver) and a main transceiver (or main receiver) operatively coupled to the processor 118 and the transmit / receive element 122.

[0052] The transmit / receive element 122 may be configured to transmit or receive signals to or from a base station (e.g., base station 114a) via 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. As an example, 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. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and receive RF and light signals. It should be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0053] Although in Figure 1B 102 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 radio signals over the air interface 116.

[0054] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As described above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers that allow the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0055] The processor 118 of the WTRU 102 may be coupled to a speaker / microphone 124, a numeric keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit), and may receive user input data from these elements. The processor 118 may also output user data to the speaker / microphone 124, the numeric keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any suitable memory such as the non-removable memory 106 and / or the removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as, for example, on a server or a home computer (not shown).

[0056] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power for use by 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 (Ni-Cd), nickel-zinc (Ni-Zn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0057] 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) related to the current location of the WTRU 102. In addition to or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) via the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It should be appreciated that the WTRU 102 may acquire location information via any suitable positioning method while remaining consistent with an embodiment.

[0058] The processor 118 may be further coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, Modules, frequency modulation (FM) radio units, digital music players, media players, video game console modules, Internet browsers, virtual reality and / or augmented reality (VR / AR) devices, and activity trackers, etc. Peripheral device 138 may include one or more sensors, which may be one or more of the following: gyroscopes, accelerometers, Hall effect sensors, magnetometers, orientation sensors, proximity sensors, temperature sensors, time sensors, geolocation sensors, altimeters, light sensors, touch sensors, magnetometers, barometers, gesture sensors, biometric sensors, and humidity sensors, etc.

[0059] The WTRU 102 may include a full-duplex radio in which the reception or transmission of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and / or simultaneous for the radio. The full-duplex radio may include an interface management unit 139 that reduces and / or substantially eliminates self-interference by means of hardware (e.g., chokes) or by signal processing by a processor (e.g., a separate processor (not shown) or by the processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio that transmits or receives some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) or downlink (e.g., for reception)).

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

[0061] The RAN 104 may include eNode-Bs 160a, 160b, 160c, however it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. Each of the eNode-Bs 160a, 160b, 160c may 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, for example, the eNode-B 160a may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0062] Each eNodeB 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with each other via an X2 interface.

[0063] Figure 1C The illustrated CN 106 may include a mobility management gateway (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. Although each of the foregoing elements are described as being part of the CN 106, it should be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0064] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, performing bearer activation / deactivation processing, and selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c. The MME 162 may also provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM or WCDMA.

[0065] The SGW 164 may be connected to each of the eNode-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may also perform other functions, such as anchoring the user plane during inter-eNode-B handovers, triggering paging processing when DL data is available for the WTRUs 102a, 102b, 102c, and managing and storing the contexts of the WTRUs 102a, 102b, 102c, and the like.

[0066] 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.

[0067] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include or communicate with an IP gateway, such as an IP Multimedia Subsystem (IMS) server, and the IP gateway may serve as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired or wireless networks that are owned and / or operated by other service providers.

[0068] Although in Figures 1A-1D The WTRU is described as a wireless terminal, however it should be appreciated that in certain typical embodiments such a terminal may use a (eg, temporary or permanent) wired communication interface with a communication network.

[0069] In a typical embodiment, the other network 112 may be a WLAN.

[0070] A WLAN using an 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 access or be connected to a distributed system (DS) or other types of wired / wireless networks that send traffic into and / or out of the BSS. Traffic originating from outside the BSS and destined for the STA may arrive through the AP and be delivered to the STA. Traffic originating from the STA and destined for a destination outside the BSS may be sent to the AP for delivery to the corresponding destination. Traffic between STAs within the BSS may be sent through the AP, for example, when the source STA may send traffic to the AP and the AP may deliver traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. The point-to-point traffic may be sent between the source and destination STAs (e.g., directly therebetween) using a direct link establishment (DLS). In certain typical embodiments, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS)). For example, a WLAN using an independent BSS (IBSS) mode does not have an AP, and STAs (eg, all STAs) within or using the IBSS can communicate directly with each other. Here, the IBSS communication mode may sometimes be referred to as an "ad hoc" communication mode.

[0071] When using the 802.11ac infrastructure operating mode or a similar operating mode, the AP can transmit beacons on a fixed channel (e.g., a primary channel). The primary channel can have a fixed width (e.g., a bandwidth of 20 MHz) or a width that is dynamically set by means of signaling. The primary channel can be a working channel of the BSS and can be used by the STA to establish a connection with the AP. In certain typical embodiments, carrier sense multiple access (CSMA / CA) with collision avoidance (e.g., in an 802.11 system) can be implemented. For CSMA / CA, STAs including the AP (e.g., each STA) can sense the primary channel. If a particular STA senses / detects and / or determines that the primary channel is busy, the particular STA can back off. In a given BSS, there is one STA (e.g., only one station) transmitting at any given time.

[0072] A high throughput (HT) STA may communicate using a 40 MHz wide channel, for example, by combining a 20 MHz wide primary channel with an adjacent or non-adjacent 20 MHz wide channel to form a 40 MHz wide channel.

[0073] Very high throughput (VHT) STA can support channels with widths of 20MHz, 40MHz, 80MHz and / or 160MHz. 40MHz and / or 80MHz channels can be formed by combining continuous 20MHz channels. A 160MHz channel can be formed by combining 8 continuous 20MHz channels or by combining two discontinuous 80MHz channels (this combination can be referred to as an 80+80 configuration). For the 80+80 configuration, after channel coding, the data can be transmitted and passed through a segment parser, which can separate the data into two streams. Inverse fast Fourier transform (IFFT) processing and time domain processing can be performed separately on each stream. The stream can be mapped on two 80MHz channels, and the data can be transmitted by the STA performing the transmission. At the receiver of the STA performing the reception, the above operations for the 80+80 configuration can be reversed, and the combined data can be sent to the media access control (MAC).

[0074] 802.11af and 802.11ah support sub-1 GHz operating modes. Compared to 802.11n and 802.11ac, the channel operating bandwidth and carrier used in 802.11af and 802.11ah are reduced. 802.11af supports 5MHz, 10MHz and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz and 16MHz bandwidths using non-TVWS spectrum. According to typical embodiments, 802.11ah can support meter type control / machine type communication (e.g., MTC devices in macro coverage areas). MTC devices can have certain capabilities, such as limited capabilities including support (e.g., only support) certain and / or limited bandwidths. MTC devices can include a battery, and the battery life of the battery is above a threshold (e.g., to maintain a very long battery life).

[0075] For WLAN systems that can support multiple channels and channel bandwidths (e.g., 802.11n, 802.11ac, 802.11af, and 802.11ah), these systems include channels that can be designated as primary channels. The bandwidth of the primary channel can be equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be set and / or limited by a certain STA, wherein the STA originates from all STAs operating in the BSS and supports the minimum bandwidth operating mode. In the example of 802.11ah, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the width of the primary channel can be 1MHz. Carrier sensing and / or network allocation vector (NAV) settings can depend on the state of the primary channel. If the primary channel is busy (e.g., because a STA (which only supports a 1MHz operating mode) transmits to the AP), then even if most of the band remains idle and available for use, the entire available band can be considered busy.

[0076] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. Depending on the country code, the total bandwidth available for 802.11ah is 6MHz to 26MHz.

[0077] Figure 1D 1 is a system diagram showing the RAN 104 and the CN 106 according to an embodiment. As described above, the RAN 104 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0078] 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. Each of the gNBs 180a, 180b, 180c may include one or more transceivers to communicate 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, the gNBs 180a, 180b, 180c may use beamforming processing to transmit and / or receive signals to and / or from the gNBs 180a, 180b, 180c. Thus, for example, the gNB 180a may use multiple antennas to transmit wireless signals to, and receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation techniques. For example, the gNB 180a may transmit multiple component carriers (not shown) to the WTRU 102a. A subset of these component carriers may be on an unlicensed spectrum, while the remaining component carriers may be on a licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) techniques. For example, the WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0079] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with the scalable parameter configurations. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may be different for different transmissions, different cells, and / or different portions of the radio transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of different or scalable lengths (e.g., containing different numbers of OFDM symbols and / or lasting different absolute time lengths).

[0080] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c without accessing other RANs (e.g., the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchors. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRU 102a, 102b, 102c may communicate / connect to the gNB 180a, 180b, 180c while communicating / connecting to another RAN (e.g., the eNode-B 160a, 160b, 160c). For example, the WTRU 102a, 102b, 102c may communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c in a substantially simultaneous manner by implementing the DC principle. In a non-standalone configuration, the eNode-B 160a, 160b, 160c may act as a mobility anchor for the WTRU 102a, 102b, 102c, and the gNB 180a, 180b, 180c may provide additional coverage and / or throughput to serve the WTRU 102a, 102b, 102c.

[0081] Each gNB 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, support network slicing, implement dual connectivity, implement interworking between NR and E-UTRA, route user plane data to user plane functions (UPFs) 184a, 184b, and route control plane information to access and mobility management functions (AMFs) 182a, 182b, and the like. Figure 1D As shown, gNBs 180a, 180b, and 180c can communicate with each other through the Xn interface.

[0082] Figure 1DThe illustrated CN 106 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and may include a data network (DN) 185a, 185b. Although each of the aforementioned elements is described as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by entities other than the CN operator.

[0083] The AMF 182a, 182b may be connected to one or more gNBs 180a, 180b, 180c in the RAN 104 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, supporting network slicing (e.g., handling different PDU sessions with different requirements), selecting a specific SMF 183a, 183b, managing registration areas, terminating non-access stratum (NAS) signaling, and mobility management, etc. The AMF 182a, 182b may use network slicing processing to customize the CN support provided to the WTRU 102a, 102b, 102c based on the type of service used by the WTRU 102a, 102b, 102c. As an 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, and / or services for machine type communication (MTC) access, etc. The AMF 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) using other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0084] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 106 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 106 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and may configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating WTRU IP addresses, managing PDU sessions, controlling policy enforcement and QoS, and providing downlink data notifications, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0085] The UPF 184a, 184b may be connected to one or more gNBs 180a, 180b, 180c in the RAN 104 via the 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, and providing mobility anchoring processing, among others.

[0086] 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 acts as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to the local data network (DN) 185a, 185b via an N3 interface connected to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b and through the UPF 184a, 184b.

[0087] In view of Figures 1A-1D and about Figures 1A-1D , one or more or all of the functions described herein with respect to one or more of the following may be performed by one or more emulation devices (not shown): WTRU 102a-d, base station 114a-b, eNodeB 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. An emulation device may be one or more devices configured to emulate one or more or all of the functions described herein. For example, an emulation device may be used to test other devices and / or emulate network and / or WTRU functions.

[0088] The simulation device can be designed to implement one or more tests about other devices in a laboratory environment and / or an operator network environment. For example, the one or more simulation devices can perform one or more or all functions while being implemented and / or deployed as a part of a wired and / or wireless communication network in whole or in part to test other devices inside the communication network. The one or more simulation devices can perform one or more or all functions while being temporarily implemented or deployed as a part of a wired and / or wireless communication network. The simulation device can be directly coupled to other devices to perform the test, and / or can use over-the-air wireless communication to perform the test.

[0089] One or more simulation devices can perform one or more functions, including all functions, while not being implemented or deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test lab and / or a test scenario of a wired and / or wireless communication network that is not deployed (e.g., testing) to implement tests on one or more components. The one or more simulation devices can be test devices. The simulation device can transmit and / or receive data using direct RF coupling and / or wireless communication with the aid of RF circuits (as an example, the circuits can include one or more antennas).

[0090] In existing wireless technologies such as cellular and WLAN, the RF front end can be a mix of passive and active components. For example, passive components may include a receive (Rx) antenna, a transmit / receive (Tx / Rx) path switch, and / or a filter. These passive components may require little power (if any) to function. In contrast, active components require power to function. For example, an oscillator tuned to a carrier frequency, a low noise amplifier, and an analog-to-digital (A / D) converter in the Rx path are active components.

[0091] Advances in RF component design over the past few years have made it possible to use RF circuit types such as passive receivers (ZE receivers), which can process received RF waveforms harvested by the receiving device through the antenna front end without active power. For example, a device equipped with a passive receiver can harvest energy from the received RF waveform to run the necessary circuits to process the signal. These passive receivers can use RF components such as cascade capacitors, zero-bias Schottky diodes, microelectromechanical systems (MEMS) to implement the functions required for voltage multipliers or rectifiers, charge pumps, and signal detectors. With these RF components, passive receivers can operate in the far field of the antenna and support a large link budget. These features enable passive receivers to receive radio signals over considerable distances.

[0092] Unlike passive receivers, radio frequency identification (RFID) and near field communication (NFC) technologies in the low frequency (LF) and high frequency (HF) bands operate in the near field region of the reader antenna. The RFID or NFC tag and the reader antenna are separated by a small percentage of the carrier wavelength. Therefore, for these technologies, communication is possible only over short distances. In the near field region, the RFID or NFC tag is tightly coupled to the transmitter on the reader. The tag then modulates the electromagnetic (EM) field generated by the reader to the transmitting reader antenna by changing the impedance value represented by the tag. By switching between lower and higher relative impedance loads, the tag produces changes that the reader in turn detects. At ultra-high frequency (UHF) and even higher frequencies, the tag is more than one radio wavelength away from the reader, which requires a different approach. Backscatter can be used by the tag to modulate the signal.

[0093] Passive receivers can perform basic signal detection, such as correlation for known marker waveforms, and / or they can be placed in energy harvesting mode by accumulating energy from RF waveforms entering the receiver front end through the Rx antenna. Link budget characteristics of small or medium area cellular base stations can be supported. For example, a passive receiver can be used as a wake-up radio (WUR) to trigger a device internal wake-up and signaling interrupt after detecting wake-up signaling, and then prompt the main modem receiver (primary connectivity radio, PCR) using active RF components to start. In this document, the terms passive receiver, passive transceiver, ZE receiver, ZE transceiver, wake-up receiver, wake-up transceiver, companion receiver, companion radio and wake-up radio can be used interchangeably. Here, the terms main receiver, main transceiver, main modem receiver and primary connectivity radio (PAR or PCR) can be used interchangeably.

[0094] When using a passive receiver, the reduction in WTRU power consumption is considerable. A typical cellular 3G, 4G or 5G modem transceiver can easily use up to hundreds of mW to demodulate and process received signals during active reception such as connected mode (e.g., RRC_Connected). Power consumption typically scales with the number of RF front-end chains active on the WTRU, the channel bandwidth used for reception, and the received data rate. When the WTRU is in RRC_Idle mode and no data is being received or transmitted, cellular radio power saving protocols such as discontinuous reception (DRX) or enhanced DRX (eDRX) ensure that the receiver only needs to be powered up a few times per second at most. The WTRU can then perform tasks such as measuring the received signal strength of the serving and / or neighboring cells for the purpose of cell (re)selection procedures and paging channel reception. In addition, the WTRU can perform automatic frequency control (AFC) and channel estimation to support coherent demodulation. In these cases, the WTRU power consumption can be on the order of several mW when in idle mode (e.g., RRC_Idle). In the case of R15 enhanced machine type communication (eMTC) and narrowband Internet of Things (NB-IoT), the sequence detection circuit for handling the in-band wake-up signal in RRC_idle mode can also be implemented in the form of a dedicated wake-up receiver or a passive receiver. This allows the A / D converter and important parts of the digital baseband processor to be powered off. However, several active components are still used in the RF front end, such as low noise amplifiers and oscillators. With a passive receiver, the power consumption of the WTRU in idle mode (e.g., RRC_idle) can be reduced to, for example, about 1mW.

[0095] When in RRC_IDLE mode, a WTRU implementing one or any combination of 2G, 3G, 4G and / or 5G radio access technologies (RATs) may perform public land mobile network (PLMN) selection, cell selection / reselection, and location registration procedures. Depending on capabilities, some devices (WTRUs) may also support manual closed subscriber group (CSG) selection or multimedia broadcast multicast service (MBMS) frequency priority in RRC_IDLE mode. 5G devices (WTRUs) may support RAN-level notification area (RNA) updates and operation in RRC_INACTIVE state.

[0096] When the WTRU is turned on, the WTRU selects a PLMN. For the selected PLMN, the associated RAT(s) may be set. With cell selection, the WTRU searches for a suitable cell of the selected PLMN, picks the cell to provide available services, and monitors its control channels. The WTRU may register its presence by means of a NAS registration procedure in the tracking area of ​​the selected cell.

[0097] While in RRC_IDLE, the WTRU performs received signal strength measurements on the serving and / or neighboring cells. If the WTRU finds a more suitable cell according to the cell reselection criteria, it may reselect to that cell and camp on it. If the new cell does not belong to at least one tracking area (TA) to which the WTRU is registered, a location registration may be performed. The WTRU may also search for a higher priority PLMN at regular time intervals and search for a suitable cell if another PLMN has been selected by its non-access stratum (NAS).

[0098] If the WTRU loses coverage of the registered PLMN, a new PLMN is automatically selected or an indication of the available PLMNs is given to the WTRU (user) so that a manual selection can be performed. There may be various control means by the network to prioritize cell selection over certain RATs, control the rate at which low, medium, or high mobility WTRUs perform cell reselection, and prevent the selected tracking area from being reselected by the WTRU.

[0099] When a WTRU is camped on a cell that is in the RRC_IDLE state or in the RRC_INACTIVE state, the WTRU may perform any of the following actions: receive system information (e.g., system information block (SIB)) from the PLMN; establish an RRC connection or resume a suspended RRC connection; and / or receive an Earthquake and Tsunami Warning System (ETWS) or Commercial Mobile Alert System (CMAS) notification. In addition, if the network needs to send a control message or deliver data to a registered WTRU, in most cases the network knows the set of tracking areas that the WTRU is camped on. A paging message may then be sent to the WTRU on the control channels of all cells in the corresponding set of areas. The WTRU may then receive the paging message and may respond to the paging message.

[0100] A WTRU equipped with and operating a passive receiver in addition to its primary receiver may benefit from near zero power consumption when the WTRU is not actively performing transmissions or receptions for the purpose of exchanging data and control signaling with the network. Assuming that the WTRU is mobile, the network tracks the approximate location of the WTRU implementing the passive receiver at least at the tracking area level. The transmission of paging messages and wake-up signaling may require the network to use DL transmission resources in terms of power, spectrum resources and / or time resources, thereby generating DL interference and reducing DL system capacity. If paging and wake-up signaling were to be transmitted to the WTRU over the entire PLMN or a significant portion of its geographic coverage without knowing where the WTRU is located, the use of DL transmission resources would quickly become excessive. Therefore, the mechanisms disclosed herein enable the WTRU to implement a passive receiver that supports cell (re)selection in idle mode and in conjunction with tracking area update procedure(s).

[0101] When operating in an idle mode (e.g., RRC_IDLE and / or RRC_INACTIVE mode), a WTRU implementing a passive receiver may also be expected to shut down all or significant portions of a primary cellular modem receiver. When the network transmits paging or wake-up signaling to a passive receiver in a WTRU, the WTRU may need to turn on its primary modem transceiver, which may incur significant time delays and may be costly in terms of battery power consumption. For example, cold start delays may be caused by the WTRU determining a cell to camp on during initial cell selection, which may include measuring many different frequencies and operating bands over an extended period of time, even if a PLMN has been pre-selected. Thus, the mechanisms disclosed herein enable WTRUs implementing passive receivers to support cell (re)selection in order to significantly reduce the startup time and power consumption of their primary modem transceivers to start up.

[0102] When applied to a WTRU equipped with a passive receiver, the existing cell (re)selection procedures for cellular networks are not applicable in their existing forms. For example, for a passive receiver, there is no DL signal to perform signal strength measurements as an input to the cell selection criteria evaluation. For example, in LTE, channel-specific reference signals (CRS) are used, and in NR, synchronization signal blocks (SSBs) are used. In their current forms, these DL signals do not enable energy accumulation by the passive receiver to perform measurements. In another example, a passive receiver DL waveform typically allows a configurable and controllable tradeoff between energy harvesting and / or information-bearing signal characteristics. The peak-to-average power ratio (PAPR) of a passive receiver DL waveform may be intentionally set high in order to allow the passive receiver to accumulate energy. Therefore, the concept of received signal strength measurement cannot be applied where the DL reference signal is typically transmitted with equal RF power and constant envelope properties (as is done with the DL reference signals in LTE or NR). In another example, the prior art cell reselection evaluation process assumes deterministic and known DL transmission settings for DL ​​reference signals transmitted by neighboring cells, so that these different cells are directly comparable to each other even when accounting for various adjustment factors. This assumption may not hold when using waveforms suitable for passive receivers.

[0103] In view of these considerations, the methods and apparatus disclosed herein are designed to enable a WTRU with a passive receiver to perform cell measurements, cell (re)selection procedures, and tracking area update procedures in a manner adapted to the specific needs and characteristics of the passive receiver technology.

[0104] As used herein, a WTRU equipped with a passive receiver may refer to a multi-mode RAT device that supports one or any combination of the following technologies: 2G GSM / EGPRS, 3G WCDMA / HSPA, 4G LTE / eMTC / NB-IoT, 5G NR, or any other wireless standard. A WTRU equipped with a passive receiver device may also include Wi-Fi, Bluetooth, GPS, or other communication technologies. In an example, a passive receiver in a WTRU may operate in-band and / or on a dedicated frequency band. In-band operation may refer to ZE signaling for a passive receiver carried in or within a portion of an operating band / frequency channel in which a primary modem receiver also operates. For example, a ZE signal and a primary radio air (e.g., Uu) interface signal may be sent in a 20 MHz channel (e.g., in LTE / NR Band 1). Dedicated band operation may refer to ZE signaling carried in a frequency channel that is different from the primary modem cellular downlink (DL) or uplink (UL) operating band / frequency channel. For example, ZE signaling may be sent in a 1 MHz wide portion of a 700 MHz band, while the primary modem receiver operates in a 20 MHz wide channel (e.g., of LTE / NR Band 1).

[0105] The example mechanisms disclosed herein describe how to derive meaningful measurements suitable for the specific properties of a ZE waveform that requires RF energy harvesting for decoding. The example mechanisms disclosed herein describe how to enable a WTRU using a passive receiver to operate as a multi-RAT device in the presence of a cell reselection process.

[0106] Figure 2 A frame format diagram showing an example ZE signal frame format 200 is shown. Figure 2 As shown, a passive receiver in a WTRU may process a transmitted ZE waveform comprising one or more power optimized waveform portions (one or more) and a signaling portion (one or more). For example, transmission of the power optimized waveform (POW) portion may be accomplished with the aid of a preamble portion 202, wherein a selected sinusoidal (one or more) or multi-tone transmission is transmitted over a portion of a frequency spectrum. Figure 3 Shown according to Figure 2200 with 1 tone, 4 tones, and 8 tones of a power optimized waveform (POWS) in FIG. 201. A modulation or multiplexing scheme may be used to send the frame body 210 (which may include, for example, a training sequence 204 and / or a broadcast / multicast / unicast message or payload 206). Example modulation or multiplexing schemes for sending the frame body 210 may include, but are not limited to, any of the following schemes: on-off keying (OOK), multi-level on-off keying (M-OOK), frequency shift keying (FSK), binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), and TDMA, FDMA, CDMA, or OFDM. A passive receiver may use the frame body 210 to determine and process control signaling and / or data signaling. The ZE waveform may be used by a WTRU using a passive receiver to determine channel status and / or reception conditions.

[0107] Figure 4 A diagram showing an example ZE (wake-up) signal structure and the corresponding energy harvesting curve at a WTRU receiving the ZE signal. The preamble portion may be optimized for power transfer and the ZE (WUR) receiver is in an energy harvesting state for the preamble portion, and the frame body may be used for power and information transfer and the ZE (WUR) receiver is in a training and decoding state for the frame body. A passive receiver may receive power optimized waveforms and / or signaling portions such as Figure 4 The ZE signal structure and energy harvesting curve shown in FIG. 1 , harvesting or accumulating energy. The POW and / or signaling portion may be associated with a measured or observed energy signature or sequence. Figure 5 A state diagram of an example state machine 500 of a ZE receiver is shown. Figure 5 As shown, the signal processing state (energy harvesting S1, receiver training S2 and signal decoding S3) and the transition conditions between these states (C xx ), processing of received ZE signaling by the passive receiver may occur. For example, the energy harvesting state S1 and the decoding state S3 may represent passive receiver processing of accumulating energy prior to processing the information bearing signal(s). Figure 6 An example of simultaneously transmitting power and information at a WTRU with a ZE receiver is shown. Figure 6 As shown, transmission of the power optimized waveform and / or signaling portion may occur according to TDM, FDM, SDM and / or power domain multiplexing principles (including time segmentation 601, power segmentation 602 and / or use of multiple antennas 603), wherein the ZE signaling portion may or may not be continuous.

[0108] Examples of reference signal design using ZE waveforms are disclosed herein. In an example, a WTRU with a passive receiver may process an instance of a ZE reference signal suitable for transmission for cell measurement purposes based on a known ZE reference signal transmission format with known transmission characteristics.

[0109] For example, when processing a ZE reference signal, any one or more of the following transmission characteristics associated with the ZE reference signal waveform or one or more of its ZE waveform portions may be known by the passive receiver: transmission duration(s), such as an absolute duration or a relative duration compared to a reference value; transmission format, such as a modulation scheme and its parameterization, modulation order, number and / or placement of tones, sequence and composition of ZE waveform portions included as part of the transmission; power profile, such as peak power, average power, values ​​representing first-order or N-order power curve statistics, such as PAPR, including the possibility of adjustment factors in calculating these; energy profile or signature, such as energy accumulation, threshold events, number, distribution and / or separation of energy accumulation windows or POWs; and / or transmission settings used by the transmitter of the ZE reference signal, such as frequency location, transmission mode or sequence, if one or more transmission parameters are changed to randomize interference contributions and / or improve the robustness of the transmission.

[0110] In an example, transmission characteristics associated with a ZE signal waveform to be used for cell measurements by a passive receiver may be preconfigured and / or known in the WTRU. In another example, these transmission characteristics may be signaled in the WTRU and may be configurable. For example, a network node such as an MME or eNB may use control signaling in the form of NAS, radio resource control (RRC), medium access control (MAC) control element (CE), or layer 1 (L1) signaling to configure and / or indicate a transmission format for the purpose of the WTRU performing cell measurements using a passive receiver.

[0111] In an example, a WTRU processing a received ZE reference signal waveform or portion thereof may determine an applicable decoding format to be processed. In an example, the WTRU may determine that the POW portion has a duration of 0.4 ms transmitted using 4 tones, followed by a frame body of duration 0.2 ms using OOK carrying a cell identifier. The WTRU may then configure its passive receiver to process any received ZE reference waveform based on the configured POW portion. For example, the WTRU accumulates energy from the received POW to meet a specified minimum threshold level of X nanojoules (nJ), thereby allowing the WTRU to subsequently decode the remaining signaling. If the threshold level is exceeded and a determined processing duration that determines the decoding format is exceeded, the WTRU may configure its passive receiver to process the signal portion that carries the information. In the event that the WTRU knows the transmission characteristics of the ZE reference signal to be measured, receiver processing is simplified and / or measurement capture delays are reduced.

[0112] Figures 7A-7D A signaling diagram of an example ZE transmission format or signature is shown. The POW may be a two-tone signal in the frequency domain and is transmitted on subcarrier frequency f1 and subcarrier frequency f2. The transmission sequence may include multiple symbol intervals, for example, up to 9 symbol intervals in time. A known ZE reference signal defined for the POW portion of the ZE signal may use transmission signature 1, such as Fig. 7A and 7C As shown, the WTRU knows that the transmission signature uses 3 symbol intervals at subcarrier frequency f1 and 3 symbol intervals at subcarrier frequency f2. The known ZE reference signal defined for the POW portion of the ZE signal may use transmission signature 2, such as Figure 7B and 7D As shown, the WTRU knows that the transmission signature uses 3 symbol intervals at subcarrier frequency f1 and 9 symbol intervals at subcarrier frequency f2. The overall resulting time domain waveform (not shown) may allow the WTRU to perform energy harvesting due to its PAPR.

[0113] Figure 8 A network diagram of an example LTE or NR communication network 800 is shown, which includes a WTRU 801 equipped with a ZE (passive) receiver 804, and an example detection sequence when the WTRU 801 processes a known ZE reference transmission format. Figure 8As shown, the WTRU 801 is equipped with a cellular transceiver (TRX) 810 for communicating with the eNB 802 via a Uu interface, and a passive receiver 804 for receiving ZE signals from the eNB 802 via a ZE air interface. The cellular transceiver 810 and / or the passive receiver 804 may be powered by a battery 806. The passive receiver 804 may include, but is not limited to, any one or more of the following components: an (operational) amplifier 812, a signal command interpreter 814, a processor 816, and / or a regulator 818, as well as other possible circuits and components (e.g., switches, resistors, capacitors, antennas, etc.). FE is the ZE signal received after indirect down conversion using a diode / envelope detector. P represents the detected / decoded bit stream. Y is a bit representation of one of a number of commands that can be interpreted by the passive receiver 804 using the signal command interpreter 814. X can be a simple wake-up interrupt telling the cellular TRX 810 to wake up, or a signal that defines the action that the cellular TRX 810 should take based on the interpreted command. The passive receiver 804 can detect a signal with a known transmission characteristic (e.g., Figure 7B or the presence of a received signal r(t) having the transmission characteristic 2) shown in 7D. Upon detecting the received signature, the processor 816 of the passive receiver 804 may determine a measurement sample.

[0114] In another example, a WTRU with a passive receiver may process one or more instances of one or more ZE reference signals suitable for cell measurement purposes based on ZE signal transmissions occurring according to a known transmission schedule. For example, a transmission schedule for processing a ZE reference signal may include one or a combination of the following features associated with a ZE reference signal waveform, or one or more of its ZE waveform portions. Examples of transmission schedules for ZE signals include, but are not limited to, any of the following schedules: a repetition period or duration; a number of occurrences of the ZE reference signal(s); and / or a timer value. The repetition period or duration may include a specified time interval where the ZE reference signal(s) may or may not be transmitted. For example, one occurrence of a ZE reference signal may be transmitted every N ms, or N occurrences that are equally spaced in time or according to a specified occurrence pattern may be transmitted every N ms, or a first period of duration T1 of N occurrences of the ZE reference signal(s) may be followed by a second period of duration T2 of no occurrences until the beginning of the next duration T1, and the sequence repeats.

[0115] In an example, for a number of occurrences of the ZE reference signal(s), the ZE reference signal may be sent once and indicated as such. In another example, the ZE reference signal may be sent N1 times according to a specified time interval(s) or a sequence thereof separating respective occurrences of the ZE reference signal. In an example, for a timer value, the WTRU may determine an expected occurrence for processing the ZE reference signal based on one or more timer values ​​and at least one second parameter. For example, based on a timer value of 3 seconds, and a known or derived start time and repetition period of every 0.5 seconds, the WTRU may determine that the ZE reference signal is transmitted 6 times.

[0116] In an example, a transmission schedule associated with a ZE reference signal for cell measurement by a passive receiver may be fixed and known to the WTRU. In another example, the transmission schedule may be configurable in the WTRU. For example, a network node such as an MME or an eNB may use control signaling (e.g., NAS, RRC, MAC CE, or L1 signaling) to configure and / or indicate parameters associated with a ZE signal transmission schedule for the purpose of the WTRU performing cell measurement using a passive receiver.

[0117] A WTRU processing a received ZE reference signal waveform or portion thereof may determine a transmission schedule to process. For example, the WTRU may determine that instances of the ZE reference signal will occur based on a sequence of time instances. The WTRU may then configure its passive receiver to process any received ZE reference waveform based on the configured sequence of determined time instances. For example, the WTRU accumulates energy from a received POW to satisfy a specified minimum threshold level of X nJ, thereby allowing the WTRU to decode subsequent signaling at the determined time instance at which the ZE reference signal portion expires. Detection of the ZE reference signal using a known schedule at the WTRU may be more robust because more signaling instances are available, allowing more energy accumulation, and because it allows the WTRU to tune and / or match its passive receiver to the specific transmission settings used by the ZE reference signal to achieve an energy accumulation rate that matches the POW characteristics of such transmission. In addition, when a WTRU processing a received ZE reference signal waveform uses a configurable schedule, the parameterization may be adjusted based on the needs of the specific device. For example, to prevent energy leakage as a function of time, the WTRU may be configured to have a more appropriate (e.g., shorter) repetition period. A WTRU based on a different implementation that results in less leakage during the same amount of time may use a longer repetition period. Detection of the ZE reference signal with a known schedule at the WTRU may be more robust also because the scheduled transmissions may be designed to support certain mobility modes (e.g., normal, medium, and / or high mobility modes) without any further signaling requirements between network nodes.

[0118] In an example, a WTRU with a passive receiver may use ZE signal detection or signaling indications such as on-demand transmissions to determine the reception and / or presence of instances of ZE reference signals (one or more) for cell measurements. In an example, the WTRU may determine the presence of ZE reference signals by configuring its passive receiver according to a determined or known ZE reference signal transmission format.

[0119] For example, the WTRU may assume a specific transmission format of the POW portion of the ZE signal waveform. The WTRU may determine the energy accumulation rate or the number of threshold events within a determined time period. If the energy accumulation rate value exceeds a specified value (e.g., a predefined threshold), the WTRU with a passive receiver may process the received ZE signal assuming that the reference signal was transmitted. The WTRU using a passive receiver may determine that the ZE reference signal waveform or a portion thereof exists from the reception of a signaling indication carried as part of a ZE reference signal transmission or a second signal. In an example, in the event that the WTRU detects the second signal, the WTRU may determine the presence or absence of the ZE reference signal. The indication to transmit the ZE reference signal may be processed by the WTRU as part of the ZE signaling portion in the frame body field. In another example, the indication may be implicitly communicated to the WTRU, for example, given by selecting a specific transmission configuration for the ZE reference signal. The WTRU using a passive receiver may determine that a ZE reference signal waveform is received that is intended to be processed by decoding an identifier. The identifier may be carried and encoded as part of the ZE reference signal transmission or the second signal.

[0120] A WTRU using a passive receiver may determine the presence of a ZE reference signal waveform. For example, the WTRU may determine that the number of POW threshold events of cumulative energy in a given time period exceeds a reference value or threshold. The WTRU may assume a known transmission format for the POW portion of the ZE signaling. The WTRU may then determine whether the ZE reference waveform is indicated using signaling received in the second signal portion. For example, the WTRU may determine a specific sequence value encoded as part of the modulation format received in the frame body of the ZE waveform. If the WTRU indicates that the ZE waveform currently being processed is a ZE reference signal, the WTRU may determine a measured sample value representing a receiver level of the ZE waveform.

[0121] For any of the example mechanisms disclosed herein, one or more ZE reference signals may be sent, for example, based on need. For example, a WTRU in a very high mobility mode moving through a certain tracking area may trigger a tracking area update and signal cells in that area to initiate on-demand ZE reference signal transmissions. The specific format of a given ZE reference signal instance may be adopted to meet the specific needs of WTRUs in the coverage area (e.g., by adjusting the POW portion to allow for an increased energy accumulation rate for a given transmission). For example, devices near or at a cell border may be configured with a more appropriate (e.g., longer) energy accumulation period than devices closer to a transmission point.

[0122] Mechanisms and processes for cell measurement using a ZE signal waveform are disclosed herein. In an example, the process for cell measurement using a ZE signal waveform may be power domain based. A WTRU with a passive receiver may determine a received power level of a ZE reference signal based on processed power characteristics of one or more ZE signaling portions (one or more). Exemplary power domain characteristics may include, but are not limited to, any of the following characteristics: peak power of a POW, signaling portion, or a specified resource element; average power of a POW, signaling portion, or a specified resource element; and / or a value representing a first or Nth order power distribution statistic (e.g., PAPR) of a POW, signaling portion, or a specified resource element.

[0123] In another example, a process for cell measurement using a ZE signal waveform may be time domain based. A WTRU with a passive receiver may determine a receiver power level of a ZE reference signal based on a time domain characteristic (e.g., a rate of change observed in energy accumulation) when processing a ZE signaling portion. A passive receiver in a WTRU may determine a cell measurement using any one or more of the following example time domain characteristics associated with a received ZE reference signal waveform, a POW, or one or more ZE reference signal portions when processing a received ZE reference signal (or one of its portions). An example time domain characteristic may include a time to accumulate ZE energy such that the accumulated energy level reaches a threshold level X1. Another example time domain characteristic may include an average value of a distribution of times for which energy levels reach a threshold level X2 for a number of measurement samples taken on the ZE waveform. Another example time domain characteristic may include a value representing a first or Nth order time distribution statistic for reaching a threshold level X3 for a number of measurement samples taken on the ZE waveform. Another example time domain characteristic may include a maximum or minimum value for which energy levels reach a threshold level X4 for a number of measurement samples taken on the ZE waveform. Another example time domain characteristic may include the number of threshold events observed to reach threshold level N1. Another example time domain characteristic may include the average of the number of threshold events observed for energy levels reaching threshold level N2 for a plurality of measurement samples taken on the ZE waveform. Another example time domain characteristic may include a value representing a first or Nth order time distribution statistic of the number of threshold events. Another example time domain characteristic may include a maximum or minimum value of the number of threshold events observed to reach threshold level N4 when measurement samples are taken on the ZE waveform. Any of the example time domain characteristics may be measured or derived using a configurable or adjustable observation interval (e.g., a measurement window).

[0124] When the number of threshold events reaching the threshold level N1 is observed, assuming that the number is harvested over a fixed time window, the number of threshold events may correspond to a value representing a first or Nth order power distribution statistic. Therefore, the power metric may be considered as a discretization of the power level. A WTRU implementing a passive receiver may derive a metric that directly represents the ZE signaling waveform. As the distance from the transmitter increases, for a given PAPR and duration of the POW portion, the energy accumulation rate per time unit may decrease, affected by propagation conditions and / or by interference on the channel (e.g., depending on the transmission method).

[0125] In another example, a cell measurement procedure using a ZE signal waveform may include a WTRU with a passive receiver determining a received power level of a ZE reference signal based on observed time differences between energy transfer events (e.g., clicks) while processing a ZE signaling portion. In this case, any one or more of the following characteristics associated with one or more of the received ZE reference signal waveform or its signal portion may be used by the passive receiver to determine the cell measurement while processing the ZE reference signal using the POW or signaling portion of the ZE waveform. Examples of time domain characteristics based on energy transfer events may include, but are not limited to, any of the following characteristics: a time difference ΔTj between the (j-1)th and jth (consecutive) transfer events (clicks), where energy from a first storage element of preconfigured first capacity is transferred to a second storage element of preconfigured second capacity when the accumulated energy in an empty first storage element exceeds a preconfigured threshold; an average time difference between N consecutive clicks measured over a preconfigured duration on a ZE waveform or portion of a ZE waveform; and / or a value representing a first or Nth order time distribution statistic of consecutive clicks measured over a preconfigured duration on a ZE waveform or portion of a ZE waveform. A WTRU implementing a passive receiver may derive a metric that directly represents a ZE signaling waveform. As the distance to the transmitter increases, for a given PAPR and duration of the POW portion, the average time difference between consecutive clicks may increase with propagation conditions.

[0126] An example measurement evaluation procedure is disclosed herein. In an example, a WTRU that determines the Rx level (received power level) of a ZE reference signal may combine multiple sampled values ​​into one value for evaluation purposes. For example, the WTRU may obtain Rx level samples of the ZE reference signal determined at a given event (e.g., using the above-described methods based on power and / or time domain) and then determine whether the cell selection (re)criteria are met by combining these samples through a filter such as an averaging filter, a linear filter, or an exponential filter.

[0127] A WTRU determining an Rx level of a ZE reference signal may take into account an adjustment factor when determining whether a cell (re)selection criterion is met. These selected adjustment and / or offset values ​​may be applied per Rx level sample, per filter value, and / or when determining the applicability of the criterion itself. In an example, the adjustment and / or offset values ​​associated with the use of ZE reference signal(s) for evaluating the cell (re)selection criterion for a passive receiver may be fixed and known to the WTRU. In another example, the adjustment and / or offset values ​​may be configurable in the WTRU. For example, a network node such as an MME or an eNB may configure and / or indicate such adjustment and / or offset values ​​using control signaling (e.g., in the form of NAS, RRC, MAC CE, or L1 signaling) for the purpose of evaluating the cell (re)selection criterion to be used by a WTRU implementing a passive receiver. Such an offset value may be associated with a specific RAT, tracking area, routing area, cell, and / or cell group. The WTRU passive receiver may use this offset value if the serving cell is strong enough so that measurements on neighboring cells do not need to be considered.

[0128] When transmitting and / or receiving a ZE reference signal, a WTRU determining the Rx level of the ZE reference signal may take into account multiple antenna transmissions. A WTRU processing a received ZE reference signal may use an observation time to determine sample values ​​representing the Rx level of the ZE waveform to accumulate energy up to a threshold X1 of the POW portion of the ZE reference signal. The WTRU may then repeat the process, each time using the last obtained sample as a new input to obtain a single filtered exponentially weighted average. A WTRU implementing a passive receiver may then use the derived weighted average (representing the RX level of the ZE waveform) in conjunction with an offset value to calculate a cell (re)selection criterion to determine the signal level at which measurements of neighboring cells should begin. By using adjustment and / or offset values, the number of evaluations and / or the number of measurement samples on neighboring cells to be included may be controlled and ultimately reduced by appropriate network settings. A WTRU with a passive receiver may benefit from a longer energy accumulation duration if only the serving cell is measured. As a result, the measurement samples become more reliable and / or more accumulated energy may be used to decode the information bearing signal.

[0129] An example measurement evaluation process may include comparing a cellular measurement to a ZE measurement. The received power level of a ZE reference signal generated by the WTRU using a passive receiver may be correlated to a cellular Rx level (received power level) measurement (e.g., reference signal received power (RSRP) using a lookup table). The WTRU may use any one or more of the following example measurements, where the measurements are made on one or more of the received ZE reference signal waveforms or signal portions thereof using a passive receiver, to approximate the cellular RSRP measurement using a lookup table. For example, the ZE measurement may include a single power domain or time domain ZE measurement. In another example, the ZE measurement may be a weighted sum of multiple power domain ZE measurements or may represent a first or Nth order time distribution statistic of multiple power domain ZE measurements. In another example, the ZE measurement may be a weighted sum of multiple time domain ZE measurements or may represent a first or Nth order time distribution statistic of multiple time domain ZE measurements. In another example, the ZE measurement may be a weighted sum of multiple power domain and time domain measurements or may represent a first or Nth order time distribution statistic of multiple power domain and time domain ZE measurements. A WTRU in idle mode may use a passive receiver to derive metrics that are directly representative of the cell (eg, RSRP measurements), thereby reducing the number of cellular measurements required in idle mode and ultimately improving the battery life of the WTRU.

[0130] Fig. 9 A network diagram of an example LTE or NR communication network 900 is shown, which includes WTRUs 901 and 902 equipped with cellular transceivers (TRXs) for communicating with eNBs 904, 906 over a Uu interface, and passive receivers for receiving ZE signals from eNBs 904, 906 over the ZE air interface when in range to successfully receive the ZE waveform signal. The WTRUs 901, 902 may communicate with the CN (and the Internet) 910 over a backhaul link via the eNBs 904, 906, and the eNBs may exchange messages over an X2 interface.

[0131] An example process for cell (re)selection of a WTRU with a passive receiver is disclosed herein. In an example, a WTRU with a passive receiver may indicate the operating bands and / or band combinations supported by its passive receiver through signaling with the RAN and / or CN (e.g., through a WTRU capability indication). For example, when a WTRU implementing a passive receiver registers its presence in the RAN and / or CN during a connection establishment and authentication / security process, the WTRU may use a primary cellular modem to indicate the WTRU capabilities supported by the WTRU associated with the passive receiver as part of its signaling exchange. In another example, WTRU radio access capability information associated with a WTRU with a passive receiver may be transmitted by the WTRU using a WTRU capability query procedure.

[0132] A WTRU implementing a passive receiver may indicate whether the passive receiver is capable of operating on one or more specified operating (frequency) bands. The WTRU may indicate whether a particular receiver sensitivity is associated with passive receiver operation on a given supported (frequency) band. The WTRU may indicate whether a particular minimum or reference energy accumulation rate is associated with passive receiver operation for one or more supported operating (frequency) bands.

[0133] When the WTRU passive receiver capability is made known to the network, the WTRU may intentionally interact with idle mode operation using a passive receiver with little to no power consumption, rather than interacting with cellular radio idle mode operation which requires device power. Identifying the operating bands may simplify the implementation of the passive receiver. Per-band indication may be useful since RF coexistence considerations may make it more costly or prohibitive to use passive receiver technology in certain operating bands.

[0134] In another example, a WTRU with a passive receiver may use a primary cellular transceiver to determine a configuration of the WTRU, such as whether the WTRU should operate in idle mode, according to a cellular procedure, and / or according to a passive receiver cell (re)selection procedure. A WTRU with a passive receiver and a primary cellular transceiver may receive configuration signaling from a network indicating whether the WTRU should enter idle mode (e.g., RRC_IDLE) and use the passive receiver (without using the primary cellular transceiver) or whether the WTRU should enter idle mode (e.g., RRC_IDLE) using the primary cellular transceiver. In an example, a WTRU that initially connects or reconnects to a network using its primary cellular transceiver (PCR) (e.g., for connection establishment, authentication / security procedures, and / or tracking update procedures) may receive an idle mode signaling indication or an idle mode configuration as part of a signaling exchange with a RAN or CN node. For example, RRC or Mobility Management (MM) signaling carried in a (dedicated per-WTRU or broadcast) DL control signaling message may be used to configure and parameterize a WTRU with a passive receiver in a passive receiver mode or a cellular mode upon transition to RRC_IDLE.

[0135] For example, a WTRU entering, selecting, or reselecting a cell under network coverage may receive idle mode signaling by decoding system broadcast information carried on a DL signaling channel decoded using a primary cellular transceiver, or may receive idle mode signaling from a DL signaling channel decoded by a passive receiver. In another example, the WTRU may determine whether to use a passive receiver or a primary cellular transceiver based on pre-stored and known information, such as a particular cell, PLMN, frequency band, and / or information stored from previously received signaling, control information, or measurements.

[0136] The idle mode configuration using passive radio mode or cellular radio mode in RRC_IDLE, signaled and / or determined by the WTRU, may be associated with any one or more of the following parameters or criteria. In an example standard, the use of a passive receiver may be allowed, not allowed, enabled, disabled, preferred, or conditionally per cell or per cell group. In another example standard, the use of a passive receiver may be allowed, not allowed, enabled, disabled, preferred, or conditionally per tracking, positioning, or routing defined at the RAN or CN level or a RAN notification area. In another example standard, the use of a passive receiver may be allowed, not allowed, enabled, disabled, preferred, or conditionally per frequency layer or operating band(s). In another example standard, the use of a passive receiver may be allowed, not allowed, enabled, disabled, preferred, or conditionally per PLMN or a list of PLMNs or equivalent PLMNs. In another example standard, the use of a passive receiver may be allowed, not allowed, enabled, disabled, preferred, or conditionally per RAT. In another example criterion, the use of a passive receiver may be allowed, not allowed, enabled, disabled, preferred, or conditionally based on a mobility state or mobility state list. Another example parameter may include Rx signal level and threshold, offset, and hysteresis value (one or more). Another example parameter may include a duration, a counter, an allowed off-channel period, or a reconnection period. Another example parameter may include a device category or class. Another example parameter may include a prohibited cell, a reserved cell, or a restricted cell for use by an operator. Another example parameter may include unified access control.

[0137] For example, the WTRU may be configured such that upon entering RRC_IDLE, use of its passive receiver is enabled and the primary cellular transceiver is enabled. In another example, the WTRU may be configured to enter RRC_IDLE using a passive receiver if the Rx level (received power level) determined by the passive receiver is above a minimum (threshold) value R1. Fig.10A flow chart of an example WTRU autonomous fallback procedure 1000 for idle mode operation using a passive receiver is shown. At 1002, the WTRU may receive cell (re)selection (CR) parameters over the Uu interface using a primary transceiver and locally store the CR parameters (e.g., any of the parameters disclosed herein). At 1004, the WTRU may enter idle mode using only a ZE receiver and disable its cellular transceiver. At 1006, the WTRU may measure the Rx level (received power level) of the received signal using the ZE receiver and continue such measurements until the Rx level drops below a critical value or threshold. Once the Rx level drops below the critical value or threshold (e.g., for time T and hysteresis H), at 1009, the WTRU may activate its primary cellular transceiver. At 1010, the WTRU camps on a cell, e.g., using a cellular RRC_IDLE procedure, and remains in the RRC_IDLE state using its cellular transceiver, e.g., until condition C occurs.

[0138] In another example, the WTRU may receive an indication that the WTRU should reconnect to the network so that the WTRU periodically indicates its location area (e.g., every H1 hour or every M1 minute). In another example, the WTRU may be configured such that use of its passive receiver is enabled as long as the tracking area identifier decoded from the ZE signaling waveform is included in the list of specified CN tracking area codes. In an example, information such as the tracking area identifier (or any other information disclosed herein) may be encoded in the POW portion of the ZE signal waveform with the number and interval of configured threshold events. In another example, the tracking area identifier (or any other information disclosed herein) may be encoded as part of the information carrying portion (e.g., frame body) of the ZE signal.

[0139] The present invention discloses a qualification mechanism for WTRU passive receiver operation. In an example, a WTRU entering RRC_idle may determine whether a passive receiver mode or a cellular receiver mode should be used. In an example, the determination may be based on DL control signaling, system information, and / or stored information. If a passive receiver mode is configured, the WTRU may determine applicable conditions under which the use of a passive receiver is allowed or enabled. The determination may be based on any one or more of the following parameters specified above. An example parameter may be based on an Rx signal level threshold, offset, and hysteresis configured for a specific cell accumulated over a specific time interval. Another example parameter may be based on the number of threshold events measured for a specific tracking area or a list of equivalent PLMNs within a specified time interval. Another example parameter may be based on a device class, an Rx signal level threshold, an offset, and / or an access class for unified access control. A WTRU using a passive receiver in idle mode may check whether applicable conditions for passive receiver operation are met. In an example, the WTRU may determine whether the Rx level measured from the ZE reference signal is above a minimum reception threshold and / or whether the most recently determined tracking area identifier is part of the allowed set. In another example, the WTRU may determine the number of threshold events measured at a specified time interval for a particular tracking area or equivalent PLMN list. If any of the conditions for allowing or enabling the use of a passive receiver are not met, the WTRU may start the primary modem transceiver and reconnect to the network or resume operation using the primary cellular transceiver.

[0140] The WTRU's use of a passive receiver (and the benefit of little or no power consumption in RRC_IDLE) is possible even if the coverage of ZE signaling in a geographic area is less than that provided by DL cellular coverage. For devices within radio range of the passive receiver technology, paging may have significantly reduced latency, standby time may be significantly increased, and for devices that leave passive receiver coverage under mobility conditions, reconnection to the network using the primary modem receiver may be invoked.

[0141] Mechanisms for mobility based ZE reference signal configuration are disclosed herein. A WTRU may determine a mobility state for use in idle mode for use with passive receiver operation. In an example, one or more mobility states (e.g., nearly stationary, normal, medium, high, or very high mobility) may be defined, signaled, and / or configured. The mobility states may be valid in some cells, or a cell may only support a subset or the full set of these mobility states on a per-cell level, per-tracking level, location, or routing area level.

[0142] Some or all of the cells associated with a certain tracking area, location area, and / or routing area may consider any one or a combination of the following ZE reference signal transmission configurations based on the supported mobility states and the mobility states of the WTRUs in the corresponding cell coverage area. Examples of such transmission configurations include, but are not limited to, the following example configurations: scheduled transmissions, where ZE reference signal transmissions occur according to a known schedule with a repetition period selected to ensure support for all WTRU mobility states up to a certain level or speed (e.g., up to medium or high mobility); and / or on-demand transmissions, where reference signal transmissions may or may not follow a known schedule and the number of occurrences within a certain time period may support a certain mobility state (e.g., nearly stationary mobility).

[0143] In an example, during a location update / registration procedure for a new WTRU, a cellular network (e.g., an eNB) may update a reference signal configuration for some or all cells within a tracking area, location area, and / or routing area, and based on the current WTRU's mobility state associated with the corresponding area. For example, one or more tracking areas that are configured to support all mobility states and currently have some or all of their cells consider on-demand ZE reference signal transmission to support nearly stationary WTRUs may receive a request to switch to scheduled ZE reference signal transmission supporting a normal mobility state. The switch request may be the result of a mobility state signal from the WTRU during a location registration procedure and based on its most recently detected mobility state. In another example, a reference signal configuration update may be triggered by a change in the mobility state of one or more WTRUs within a tracking area, location area, or routing area. For example, one of the WTRUs in an area whose cells are configured with on-demand reference signal transmission to support nearly stationary mobility may detect a change in mobility state to normal mobility. The WTRU may then wake up the primary cellular transceiver to signal the mobility state change, and based on the network response, the WTRU may decide to return to RRC_IDLE using the primary cellular transceiver or the passive receiver.

[0144] In an example, a combination of scheduled and on-demand ZE reference signal transmissions may be an option for some or all cells in a certain tracking area, location area, or routing area. For example, an area may be considered where all cells are configured with scheduled reference signal transmissions that support normal mobility WTRUs. A new WTRU may initiate a tracking, positioning, or routing area update for the area, and the WTRU may signal very high mobility as its most recently detected state. The network may then signal the cells in the area to supplement the currently considered scheduled transmissions with on-demand transmissions that support very high mobility states for a certain amount of time or until another signal is received. The WTRU may use a passive receiver procedure to check if a change in the tracking area identifier (which requires a tracking area update procedure) or a change in the mobility state is detected. The WTRU may wake up the primary cellular transceiver to perform a tracking area update or mobility state update procedure, signaling its most recently detected mobility state to the network. Based on the network response, the WTRU may decide whether to use the primary cellular transceiver or a passive receiver to return to RRC_idle mode. A network that employs adaptive ZE reference signal transmission to support WTRUs with passive receiver implementations may optimize their power consumption based on the various mobility requirements of the served WTRUs.

[0145] Example WTRU procedures for cell (re)selection over a ZE air interface are disclosed herein. In an example, a WTRU with a passive receiver implementation in ZE idle mode may perform any one or more of the following operations (in addition to other passive receiver idle mode procedures described herein): cell measurements (serving cell and / or neighbor cells); evaluation of cell selection and reselection criteria; camping on a cell picked according to the cell (re)selection criteria; and / or fallback to a Uu receiver if a fallback trigger is detected.

[0146] Example WTRU procedures for cell identification and cell measurements performed by a passive receiver based on an explicit indication of a cell ID are disclosed herein.According to the example procedures for cell identification and cell measurements, a WTRU using a passive receiver may use a ZE reference signal, as described above, to perform cell measurements. Fig.11 1 shows a frame format of an example ZE measurement signal frame format 1100 with an explicit cell ID indication 1106 (eg, based on M-OOK or OFDM). Fig.11As shown, the ZE signal format 1100 for cell measurement may be a format such that the cell ID 1106 is explicitly indicated to the WTRU, and other fields of the ZE signal format 1100 may include, but are not limited to, a preamble 1102, an end of preamble indication 1104, and / or a unique sequence 1108 reflecting cell power (e.g., based on M-OOK or OFDM). Based on the cell ID 1106, the ZE receiver may know the cell for which it is performing cell measurement, and may store the measurement of each cell for later use as a cell reselection criterion.

[0147] According to an example procedure of cell identification and cell measurement performed by a passive receiver, a WTRU may detect a POW preamble (1102) and an end of preamble indication (1104) in a ZE measurement reference signal (having a ZE measurement signal frame format 1100). The WTRU may start decoding the cell ID (1106) after the preamble (1102 / 1104) is transmitted. The WTRU may measure the signal strength of the cell using a known sequence that may or may not be unique to the detected cell. The transmission order of the different fields in the ZE measurement reference signal may be the same as Fig.11 , so that the process may be performed in the order in which these fields appear in the ZE measurement reference signal frame format. The WTRU may store the signal strength measurement samples for further processing, or directly evaluate the measurements using cell (re)selection criteria. When processing a received ZE reference signal, any one or more of the following transmission characteristics associated with any of the ZE reference signal waveforms or ZE waveform portions may be known to the passive receiver at the WTRU: a priori knowledge of the frame format of the ZE measurement reference signal (e.g., the modulation format, duration, and / or period of the ZE reference signal); a known preamble format with an end-of-preamble indication used as a POW; a signaling portion indicating the transmitting cell ID; and / or a sequence suitable for cell signal strength measurements (which may be unique to each cell or common between groups of cells).

[0148] To ensure efficient decoding of the ZE measurement reference signal, the network may coordinate the transmission of the ZE measurement reference signal between neighboring cells in such a way that a passive receiver at the WTRU can distinguish between the ZE reference signal or a portion thereof received from each different cell. In an example, the coordination may be such that a portion of the ZE measurement reference signal used for cell ID identification and signal strength measurement may be transmitted in a time division multiplexed manner such that at any moment only a single cell transmits the reference signal portion corresponding to the cell ID and the strength measurement sequence. In another example, the cell ID and the signal strength measurement portion may be transmitted in different frequencies in a frequency multiplexed manner such that a passive receiver may tune to a different frequency to decode those signals for each cell. In another example, the network may coordinate the transmission of the ZE measurement reference signal between neighboring cells in such a way that only the cell ID portion of the ZE measurement reference signal may be transmitted in a time multiplexed manner such that at any one time only one cell transmits its cell ID. In another example, the cell ID may be transmitted in different frequencies in a frequency multiplexed manner such that a passive receiver will tune to a different frequency to decode the cell ID. After decoding the cell ID part, the passive receiver can determine the information of the unique sequence of each cell to be applied to the reception of the signal strength measurement part of each cell.

[0149] An example process of cell identification and cell measurements performed by a passive receiver may be based on an implicit indication of a cell ID. Fig.12 A frame format of an example ZE measurement signal frame format 1200 with implicit cell ID indication is shown. A WTRU with a passive receiver may use a ZE measurement reference signal (with ZE measurement signal frame format 1200) for cell measurement that implicitly indicates the cell ID to the WTRU. The WTRU may need to decode the cell ID in order to know the cell for which it is performing cell measurement and may store the measurement of each cell for use in cell reselection criteria. The WTRU may detect the POW preamble (1202). The WTRU may use a list of preconfigured identifiers to blindly decode the NID in the ZE measurement reference signal (with ZE measurement signal frame format 1200). (2) sequence (1204), and cell signal strength measurement may be performed.

[0150] Identifier NID (2) (1204) may correspond to a portion of a physical cell identifier (ie, or any other part thereof), or it may correspond to a unique ZE identifier (ID) in the ZE tracking area of ​​the ZE air interface. (2) (1204) can be used to indicate the NID that can be used for the cell (1)(1206) Another finite set of possible preconfigured identifiers for blind decoding. NID (1) (1206) may correspond to a physical cell identifier and NID (2) A different part (i.e. or any other part), or it may correspond to a ZE identifier (ID), which may or may not be unique within a ZE tracking area. (1) and NID (2) The WTRU may use the NID to map the cell signal strength to a unique physical cell identifier. (1) and / or NID (2) to determine the ZE and physical cell ID. The WTRU may store the cell signal measurement sample for further processing or use it to directly evaluate the measurement using cell (re)selection criteria. In an example, there may be a unique mapping between the ZE cell ID and the physical cell ID within a specific ZE tracking area, and this unique mapping may be signaled to the WTRU (e.g., by the eNB over the Uu air interface). This mapping may be used by Uu idle mode operation to initiate cell selection and reselection. The transmission order of the different fields in the ZE measurement reference signal may be similar to Fig.12 , so that the steps of the process will be performed in the order in which these fields appear in the ZE measurement reference signal frame format 1200.

[0151] When processing the ZE reference signal, any one or more of the following example transmission characteristics associated with one or more of the ZE measurement reference signal waveform or ZE waveform portions thereof may be known by the passive receiver: a priori knowledge of the frame format of the ZE measurement reference signal (e.g., the modulation format, duration, and / or period of the ZE reference signal); a known preamble format used as a POW; and / or a NID (1) , NID (2) As a list / table of identifiers to be tracked within a specific region.

[0152] An example process of cell identification and cell measurement performed by a passive receiver may be based on an implicit indication of the cell ID such that the preamble format used for the POW is unique for each neighboring cell, or a sequence unique for each cell is sent after the common POW transmission. In an example, the sequence after the POW in the ZE measurement reference signal may be constructed by masking a known signal / sequence with a unique cell ID. Figures 13A-13D 1300A, 1300B, 1300C, 1300D are shown with example ZE measurement signal frame formats with implicit cell ID indication. For example, the implicit cell ID may be provided by a unique POW preamble 1302 ( Fig.13A ), a unique sequence 1308 for each cell for signal strength after the POW preamble 1306 ( Fig. 13B ), POW 1304 masked with cell ID ( Fig. 13C ), or a unique sequence 1312 for signal strength masked with a cell ID after the POW preamble 1310 ( Fig.13D ). The unique cell ID may correspond to a physical cell ID or it may correspond to a ZE cell ID which is unique within a ZE tracking area of ​​the ZE air interface. There may be a unique mapping between a ZE cell ID and a physical cell ID within a specific ZE tracking area which is signaled to the WTRU via the Uu air interface. This mapping may be used by the Uu idle mode operation to start the cell selection and reselection process. The WTRU may use a list of (ZE or physical) cell identifiers and blindly decode the cell ID by mapping to a unique sequence / signature in order to know the cell for which the WTRU is performing cell measurements. The WTRU may store the measurements for each cell for use in cell (re)selection criteria evaluation.

[0153] In an example, the WTRU may use the POW preamble ( Fig.13A In another example, if POW is used as a unique sequence representing a cell ID ( Fig. 13C 1304 in ), the WTRU may utilize the POW preamble to blindly decode the cell identifier while harvesting energy and / or measuring the signal strength of the identified cell. If the POW is common to all considered cells (e.g., serving and / or neighboring) and is not masked with a unique sequence, the WTRU may utilize the cell ID ( Fig. 13B The WTRU may blindly decode the cell identifiers using a unique sequence (in 1308) and simultaneously measure the signal strengths of the identified cells. The WTRU may map the measured signal strengths to their corresponding cell identifiers and use them directly to evaluate the cell (re)selection criteria and / or store them together with their mapping for further processing prior to evaluation. The unique sequence representing the cell identifier may be defined as the (ZE or physical) cell identifier itself, or a known sequence masked with the cell identifier, or may be mapped (e.g., by a lookup table) to a specific unique sequence of cell identifiers.

[0154] When processing the ZE reference signal, any one or more of the following example transmission characteristics associated with one or more of the ZE measurement reference signal waveform or its ZE waveform portion may be known by the passive receiver: a priori knowledge of the frame format of the ZE measurement reference signal (e.g., the modulation format, duration and / or period of the ZE reference signal); a known preamble format used as a POW for harvesting energy or a list of preamble sequences; a physical cell ID, a ZE cell ID and / or a list of unique sequences mapped to cell identifiers; and / or the composition of the POW signal and the measurement sequence (e.g., with a specified unique sequence mapped to a cell identifier or a known sequence masked with a cell identifier).

[0155] According to the disclosure herein, cell selection and reselection procedures may be performed by a passive receiver.A WTRU with a passive receiver in a passive receiver idle mode may perform cell selection / reselection based on cell measurements that the WTRU shall make using any one or more of the ZE measurement reference signals described herein. Fig.14 1404. A flow chart of an example ZE idle mode cell (re)selection process 1400 is shown, which may be performed by a WTRU with a passive receiver. At 1402, the WTRU may be in ZE idle mode (i.e., in ZE mode during idle mode with the cellular transceiver turned off). At 1404, the WTRU may measure the signal strength of its own serving cell. At 1406, the WTRU may determine whether the signal strength is greater than a cell quality threshold (Thresh cellQ If the signal strength is greater than the cell quality threshold, then at 1404, the passive receiver may continue to monitor and measure the serving cell. If the serving cell signal strength is less than the cell quality threshold (Thresh cellQ ), then at 1408, the WTRU may determine its ability to monitor neighboring cells (i.e., perform neighboring cell measurements). If the WTRU is able to monitor neighboring cells, then at 1412, the WTRU may measure the signal strength of the neighboring cells. If a passive receiver is used to perform neighboring cell measurements, then at 1414, the WTRU may use the recorded measurements to evaluate the cell (re)selection criteria. If the WTRU finds a suitable cell after the cell (re)selection criteria evaluation using the passive receiver, then at 1416, the WTRU selects the best new cell to camp on (e.g., based on the neighboring cell with the strongest signal) and receives and / or updates the cell reselection configuration using the passive (ZE) receiver. If the WTRU does not find a suitable cell after the cell (re)selection criteria evaluation (1414), or if the WTRU determines that it does not have the ability to monitor neighboring cells (1408), then at 1410, the WTRU may trigger Uu idle mode operation, thereby activating the cellular transceiver of the WTRU in idle mode.

[0156] Fig.15 1 is a flow chart showing an example passive receiver based ZE idle mode cell (re)selection process 1500 that may be performed by a WTRU having a passive receiver. Fig.15 As shown, when using a passive receiver to make signal strength measurements of serving and neighboring cells, the WTRU may perform a cell (re)selection decision based on an example cell (re)selection criterion. For the example ZE idle mode cell (re)selection process 1500, it may be assumed that any one or more of the following transmission characteristics associated with one or more of the ZE reference signal waveform or its ZE waveform portion are known to the passive receiver when processing a ZE reference signal from a neighboring / camped cell: a threshold value for cell quality, which may be used to determine whether the cell is suitable for camping or to determine whether the serving cell is suitable for remaining camped; a minimum threshold that the signal strengths of different cells must meet for the cell (re)selection criterion; a list of prohibited cells, reserved cells, and / or restricted cells for use by the operator; knowledge of the cells associated with the tracking area (TA) of the ZE reference signal; a list of neighboring cells; and / or offset and hysteresis values ​​associated with mobility or energy leakage factors. A WTRU with a passive receiver may process an instance of a transmitted ZE reference signal assuming a well-defined transmission format with known transmission characteristics (e.g., energy signature, energy-based threshold sequence). The WTRU may determine the Rx level of the ZE reference signal based on the observed rate of change of energy accumulation or rate of change between energy transfer events (clicks) when processing the ZE signaling waveform. The WTRU may determine the cell identity from which the ZE reference signal is received by decoding / receiving the cell identity embedded / transmitted with the ZE reference signal. The WTRU may determine the equivalent observed RSRP level(s) for DL ​​cellular RSRP measurement(s) of the serving cell and / or neighboring cells based on the Rx level from the ZE reference signal and use it for cell selection (re)criteria evaluation.

[0157] according to Fig.15 Example ZE Idle Mode Cell (Re)Selection Procedure 1500, at 1502, the WTRU may determine a representative amount of signal strength of neighboring cells and pre-occupied cells. At 1504, the WTRU may sort the neighboring / pre-occupied cells in the candidate list in descending order of signal strength, which may be used for cell (re)selection. At 1506, the WTRU may determine whether the neighboring or pre-occupied cell with the strongest signal strength has a signal strength above a minimum threshold (Thresh minQ ) signal strength. If the neighboring or pre-occupied cell in the candidate list has a signal strength above the minimum threshold (Thresh minQ), then at 1510, the WTRU may remove the prohibited and retained cells from the candidate list. At 1512, the WTRU may further remove cells that are not part of the ZE reference signal tracking area (TA) from the candidate list. At 1514, it is determined whether at least one cell remains in the candidate list. If at least one cell remains in the candidate list, then at 1516, the WTRU may determine whether the remaining selected cells (with the maximum signal strength) from the candidate list have a cell quality threshold (Thresh cellQ ). If the signal strength is greater than the cell quality threshold, the WTRU may camp on the selected cell (with the strongest signal strength). If the remaining selected cells do not have a signal strength greater than the cell quality threshold (1516), or if no cells remain in the candidate list (1514), or if no neighboring or camped cells have a signal strength above a minimum threshold (Thresh minQ )(1506), then at 1508, the WTRU may trigger Uu idle mode operation, thereby activating the cellular transceiver of the WTRU in idle mode.

[0158] Any of the following example procedures may be used for a WTRU with a pass-through receiver operating in idle mode to fall back from a ZE air interface to a Uu interface (by turning on its primary transceiver). As described herein, ZE idle mode operation may mean that the WTRU is in idle mode with its primary transceiver turned off and monitoring the ZE air interface, and Uu idle mode operation may mean that the WTRU is in idle mode with its primary transceiver (PCR) turned on.

[0159] In order to save battery power, a WTRU equipped with a passive receiver may choose to use the passive receiver for idle mode operations / procedures (e.g., cell (re)selection procedures) over the ZE air interface instead of using the primary cellular transceiver over the Uu air interface. When operating in ZE idle mode using a passive receiver, the WTRU may determine / detect a trigger that may indicate that the passive receiver is unable to perform the desired idle mode operations / procedures. Example triggers and criteria are described below. Based on the trigger, the WTRU may decide to fall back to idle mode operation over the Uu air interface (AI) using the primary transceiver, thereby turning on its primary transceiver. Fig.16 A flow chart of an example ZE-AI to Uu-AI fallback procedure 1600 is shown for a WTRU operating in idle mode with Uu / ZE air interface support. Fig.16An example of interaction between the ZE (passive receiver) air interface and the Uu (primary transceiver) air interface of a WTRU operating in idle / inactive mode is shown. At 1602, a WTRU operating in Uu idle mode may register with the network and report its capabilities to the network over the Uu interface. At 1604, the WTRU may receive Uu AI and / or ZE AI related configuration updates over the Uu AI. At 1608, the WTRU may check for a trigger or trigger indication to enter ZE idle mode (using only a passive receiver on the ZE air interface) and / or may evaluate network configuration for ZE idle mode operation criteria. At 1610, based on the trigger and / or criteria, the WTRU may enter ZE idle mode operation over the ZE air interface or continue idle mode operation over the Uu air interface at 1612. At 1614, while operating in ZE idle mode over the ZE air interface, the WTRU may continue to check for a trigger (or trigger indication) to transition to idle mode operation over the Uu air interface (1612). While in Uu idle mode, the WTRU may continue to receive Uu and / or ZE AI configuration updates (1604).

[0160] Fig.17A flow chart of another example ZE-AI to Uu-AI fallback procedure 1700 is shown for a WTRU operating in idle mode with Uu / ZE air interface support. At 1702, a WTRU operating in Uu idle mode may register with the network and report its capabilities to the network over the Uu interface. At 1704, the WTRU may receive Uu AI and / or ZE AI related configuration and / or updates over the Uu AI. At 1708, the WTRU may check for a trigger or trigger indication to enter ZE idle mode (using only a passive receiver over the ZE air interface) and / or may evaluate network configuration for ZE idle mode operation criteria. Based on the trigger and criteria, the WTRU may enter ZE idle mode operation over the ZE air interface at 1710 or continue idle mode operation over the Uu air interface at 1718. During ZE idle mode operation 1710, the WTRU may enter passive receiver idle mode at 1712 by turning off its primary transceiver. During ZE idle mode operation 1710, the WTRU may evaluate cell (re)selection criteria via the ZE-AI at 1714. During ZE idle mode operation 1710, the WTRU using its ZE receiver may select a new cell to camp on at 1716 and the WTRU may receive and update cell reselection (CR) configuration via the ZE AI. At 1720, while the WTRU is operating in ZE idle mode over the ZE air interface, it may continue to check for triggers (or trigger indications) to switch (fall back) to idle mode operation over the Uu air interface (1718). While in Uu idle mode, the WTRU may continue to receive Uu and / or ZE AI configuration updates (1704).

[0161] A WTRU equipped with a capable passive receiver may choose to initiate a transition or fallback procedure from the ZE air interface to the Uu air interface based on any one or more of the following example triggers or criteria. According to the example triggers / criteria, the WTRU may receive a common control signaling message (e.g., a system information update message) indicating that the current serving cell cannot support idle mode operation over the ZE air interface (e.g., due to limited availability of resources) and requesting the WTRU currently operating in idle mode with its passive receiver to wake up its primary transceiver and initiate idle mode operation over the Uu air interface. The WTRU may then initiate idle mode operation over the Uu air interface within a hysteresis / offset timer T. off,t After expiration, idle mode operation is performed over the Uu air interface. The timer value may be signaled as part of an air interface request message and / or may be associated with a specific cell, tracking area, or notification area. If the WTRU exceeds the timer T off,t If a new serving cell, tracking area, or notification area is detected before expiration, the WTRU may decide not to transition to idle mode operation over the Uu air interface.

[0162] According to another example trigger / criteria, the WTRU may receive a common control message over the ZE air interface that specifies a battery level threshold and / or hysteresis value above which the WTRU should consider transitioning idle mode operation from the ZE air interface to the Uu air interface, potentially limiting the number of devices that are not necessarily operating over the ZE air interface. The threshold and hysteresis values ​​may also be pre-configured or internally defined by the WTRU to potentially improve the overall user experience. The WTRU may then monitor its battery level and compare it to the provided / defined threshold and / or hysteresis value and switch between idle mode operation over the ZE and Uu air interfaces accordingly.

[0163] According to another example trigger / criteria, a WTRU operating in idle mode using a passive receiver over a ZE air interface may track the signal strength of the current serving cell. The WTRU may then detect if the serving cell signal strength is within a specified time period T. serv,p falls below a certain threshold H serv,p , whereby the thresholds and timer values ​​may be preconfigured at the WTRU and / or dynamically signaled / configured by the network. The WTRU may then decide to switch to idle mode operation over the Uu air interface (because the current serving cell cannot support the WTRU's operation in idle mode over the ZE air interface) or select a new cell based on the network configuration (i.e., cell (re)selection criteria and parameters). In an example, since the WTRU fails to detect a cell that meets the ZE cell (re)selection criteria (e.g., the cell is barred, reserved, or restricted for ZE air interface access), the WTRU may decide to switch directly to idle mode operation over the Uu air interface.

[0164] According to another example trigger / criteria, when the primary transceiver is active over the Uu air interface or dynamically updated / signaled by the network over the ZE air interface, a WTRU performing a cell (re)selection procedure over the ZE air interface may detect a cell identifier that does not belong to a list of identifiers pre-configured at the WTRU. In an example, the WTRU may detect a cell, tracking area, or notification area identifier that is different from the pre-configured or dynamically signaled identifier (or set thereof) of the cell, tracking area, or notification area. Then, in a next step, the WTRU may determine that the WTRU needs to update its location in the network and / or that the newly detected cell, tracking area, or notification area does not support idle mode operation over the ZE air interface. The WTRU may then wake up the primary transceiver and initiate idle mode operation over the Uu air interface.

[0165] According to another example trigger / criteria, the WTRU may first enter idle mode over the ZE air interface using a passive receiver and initialize a validity timer T that is preconfigured at the WTRU or dynamically signaled / configured by the network. ZE,valid The WTRU may then wake up the primary transceiver and initiate idle mode operation over the Uu air interface upon expiration of the validity timer. The purpose of the timer is to limit idle / inactive mode operation of the WTRU using a passive receiver over the ZE air interface and / or to periodically update the network with the passive receiver status.

[0166] According to another example trigger / criteria, a WTRU performing idle mode operation / procedure over a ZE air interface using a passive receiver may be delayed by a failure timer T ZE-RS,period A ZE signal identified by a particular transport format is not detected within a defined total time period. In the example, the WTRU may not be able to detect a ZE signal identified by a particular transport format within a defined total time period. ZE-RS,inst The failure timer T is a time interval in which a ZE signal identified by a specific scheduling identifier is detected in consecutive time instances of . For example, the ZE signal may be a notification message (e.g., a paging message) or a measurement reference signal. ZE-RS,period and the number of failed instances N ZE-RS,inst It may be pre-configured at the WTRU or dynamically signaled / configured by the network.

[0167] According to another example trigger / criteria, the WTRU may rely on the harvested energy to perform idle mode operation using a passive receiver over the ZE air interface. When considering the harvested energy to decide on idle mode operation, the WTRU may perform any one or more of the following steps. The WTRU may detect a specified period of time T EH,period The harvested energy charging rate is less than the specified threshold H EH,rate In an example, the WTRU may detect a harvested energy efficiency associated with reception of a signal / POW / preamble of known format or characteristics that is less than a specified threshold η EH,eff , which may be defined internally in the WTRU, preconfigured at the WTRU, or dynamically signaled / configured by the network. The WTRU may then determine the duration T EH,evalIn this case, the WTRU may decide to limit idle mode operation over the ZE air interface to reduce power consumption requirements. The WTRU may evaluate a tradeoff metric between passive receiver and active transceiver operation in idle mode, for example, by evaluating overall power consumption and / or idle mode operation performance. The WTRU may compare the evaluated tradeoff metric to a threshold value H that is preconfigured at the WTRU or dynamically signaled / configured by the network. ZE-Uu,trade-off In an example, the WTRU may determine whether the passive receiver has access to the WTRU's primary battery (i.e., the battery used by the primary transceiver), or is limited to a limited battery / capacitor that requires RF energy to charge. Based on any of the above triggers or criteria, if the tradeoff metric is above a specified threshold, the WTRU may decide to continue idle mode operation over the ZE air interface, or the WTRU may decide to wake up the primary transceiver and initiate idle mode operation over the Uu air interface.

[0168] Fig.18 A flow chart of an example idle mode operation decision process 1800 performed by a WTRU with a passive receiver is shown. The example idle mode operation decision process 1800 may be used by the WTRU to determine when to switch (or fall back) between ZE idle mode operation with the primary transceiver turned off and Uu idle mode operation with the primary transceiver turned on. At 1802, the WTRU may enter ZE idle mode operation via the ZE-AI (and the primary transceiver is turned off). At 1804, the WTRU may harvest energy via the ZE-AI using the passive (ZE) receiver. At 1806, the WTRU may measure the quality of the harvested energy (EH) and / or may monitor the battery level of the ZE receiver. At 1808, the WTRU may determine the energy requirements of idle mode operations and processes (e.g., cell (re)selection processes) based on the above parameters and criteria. At 1810, the WTRU may harvest the energy EH harvested in the ZE idle mode operation. h The energy consumed E c For comparison, if the energy harvested E h Exceeds the energy consumed E c , then the WTRU may decide to remain in ZE idle mode operation (e.g., return to 1804). h Lower than the energy consumed E c(meaning that the battery level will decrease over time in ZE idle mode because energy is consumed faster than it is harvested), then a decision may be made in one of the following: at 1812, the WTRU may decide to remain in ZE idle mode, but limit idle mode operation via ZE-AI; or, at 1814, the WTRU may additionally check the ZE receiver to access the primary battery. For example, the WTRU may limit idle mode operation by reducing the measurement frequency at the expense of measurement quality, and / or by using duty cycle paging reception instead of on-demand paging reception. If the WTRU has access to the primary WTRU battery, then at 1816 the WTRU may continue to perform ZE idle mode operation (without turning on the primary transceiver) and use the primary battery via ZE-AI. If the WTRU does not have access to the primary WTRU battery, then at 1818, the WTRU may switch / fall back to Uu idle mode operation and turn on its primary transceiver.

[0169] In an example, the WTRU may save battery power by deciding to continue idle mode operation over the ZE air interface as long as the WTRU operates energy efficiently and the performance tradeoff metric is above a specified threshold; otherwise, the WTRU initiates idle mode operation by waking up or turning on its primary transceiver and over the Uu air interface.

[0170] Fig.19 A flow chart of another embodiment of an idle mode operation determination process 1900 is shown, which is performed by a WTRU with a passive receiver. The example idle mode operation determination process 1900 may be used by a WTRU to determine when to switch (or fall back) between ZE idle mode operation with the primary transceiver turned off and Uu idle mode operation with the primary transceiver turned on. At 1902, the WTRU may receive energy harvesting (EH) related configuration information via the ZE-AI, such as for cell (re)selection operation, and may enter ZE idle mode operation via the ZE-AI, turning off the primary transceiver. At 1904, the WTRU may detect ZE reference signal(s) (e.g., (transmitted by the eNB)) via the ZE-AI, for example, based on a time sequence of energy accumulation events (e.g., using an energy curve or marker, such as the number, distribution or interval of threshold events), and may harvest energy from the ZE reference signal(s). At 1906, the WTRU may measure the energy accumulated over a specified duration T. m The amount of energy E harvested using the received ZE reference signal(s) h At 1908, the WTRU may determine that while supporting ZE idle mode operation, the WTRU may also determine that during the same specified duration or period T m The amount of energy consumed by c At 1910, the WTRU can harvest the energy E h The energy consumed in idle mode operation isc For comparison, if the energy harvested E h Exceeding the energy consumed E c , the WTRU may decide to remain in ZE idle mode operation (e.g., return to 1904). h Lower than the energy consumed E c , (implying that the battery level will decrease over time in ZE idle mode because the measure of energy consumed is faster than the measure of it harvested), at 1912, the WTRU may evaluate an operational tradeoff metric (any of the example operational tradeoff metrics described herein). This evaluation may be based on relative to a threshold H ZE-Uu,trade-off (Threshold H ZE-Uu,trade-off The overall energy consumption and / or WTRU performance of the WTRU may be signaled to the WTRU or pre-configured at the WTRU). If the tradeoff metric is determined to be below a specified threshold, the WTRU may switch (fall back) to the Uu air interface and initiate Uu-AI idle mode operation at 1914, which includes turning on the primary transceiver. If the tradeoff metric is determined to be above a specified threshold, the WTRU may remain in ZE idle mode operation (e.g., returning to 1904).

[0171] Although the features and elements are described above in specific combinations, it will be understood by those skilled in the art that each feature or element can be used alone or in any combination with other features and elements. In addition, the methods described herein can be implemented in a computer program, software, or firmware, which is incorporated into a computer-readable medium to be executed by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via a wired or wireless connection) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor associated with the software can be used to implement a radio frequency transceiver used in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A method performed by a wireless transmit / receive unit (WTRU) operating in an idle mode, the method comprising: receiving, by a master transceiver over a Uu interface, information indicating an energy harvesting (EH) configuration for use over a zero energy (ZE) air interface; Turning off the main transceiver; detecting, by a ZE receiver, a ZE reference signal over the ZE air interface in accordance with the EH configuration and as part of a ZE idle mode operation, and harvesting, by the ZE receiver, energy from the ZE reference signal detected over the ZE air interface; as well as The master transceiver is turned on under the condition that the energy consumption in a first time period is greater than the amount of energy harvested in the first time period.

2. The method according to claim 1, further comprising: Under the condition that the energy consumption during the first time period is less than the amount of energy harvested during the first time period, energy is continued to be harvested by the ZE receiver from a ZE reference signal detected over the ZE air interface.

3. The method according to claim 1, further comprising: Under the condition that the energy consumption in the first time period is greater than the amount of energy harvested in the first time period and a measured performance value is greater than a first threshold, energy is continued to be harvested by the ZE receiver from a ZE reference signal detected over the ZE air interface.

4. The method according to claim 1, further comprising: The ZE receiver continues to harvest energy from a ZE reference signal detected over the ZE air interface under the condition that the energy consumption during the first time period is greater than the amount of energy harvested during the first time period and the ZE receiver is connected to a battery.

5. The method according to claim 1, wherein: The ZE reference signal is detected based on the time series of energy accumulation events using energy curves or markers.

6. The method according to claim 1, wherein: Each of the ZE reference signals includes a power optimized waveform (POW) portion.

7. The method according to claim 6, wherein: The energy is harvested from the ZE reference signal based on the POW portion.

8. The method according to claim 1, wherein: Each of the ZE reference signals includes an information carrying portion including at least a sequence, and wherein the energy is harvested from the ZE reference signal based on the information carrying portion.

9. The method according to claim 1, further comprising: According to the EH configuration, cell selection and cell reselection procedures are performed over the ZE air interface.

10. The method according to claim 9, wherein: Further comprising, as part of said cell selection and cell reselection process: measuring the signal strength of a signal from a serving cell; as well as Under the condition that the signal strength of the signal from the serving cell is lower than a first threshold, signal strengths of signals from a plurality of neighboring cells are measured, a cell is selected from the plurality of neighboring cells based on a cell selection and reselection criterion, and the selected cell is pre-occupied.

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