Methods and apparatuses for enabling device synchronization

Abstract

Methods, readers and devices are disclosed for configuring and aligning activity cycles of multiple devices with unknown synchronization states are disclosed. In one embodiment, a method for an Internet-of-Things (IoT) reader includes determining a target activity cycle for a group of IoT devices based on received configuration signaling, transmitting a first type of synchronization signal at a first on-period of the determined target activity cycle and repeatedly transmitting a second type of synchronization signal between transmissions of the first type of synchronization signal, indicating a period of time from transmission of each second type of synchronization signal until a next transmission of the first synchronization signal and a maximum duty rate required for the target activity cycle. Methods for an ambient Internet-of-Things (AIoT) device to synchronize with the reader based on the synchronization signals are also disclosed.

Description

METHODS AND APPARATUSES FOR ENABLING DEVICE SYNCHRONIZATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 573,271 , filed April 2, 2024, the contents of which are incorporated herein by reference.BACKGROUND

[0002] Internet-of-things (loT) systems include connected devices / things (e.g., sensors) that can communicate with a network using small data payload and low transmission power. 3GPP introduced loT service in both long term evolution (LTE) and new radio (NR). The type of devices and the deployment scenario for loT keeps evolving as the demand for connected things increases. Recently, high interest was shown to support a very low power consumption type of loT devices in cellular systems, which led the 3GPP community to evaluate how Ambient loT (AloT) type of devices can be deployed and supported in cellular networks. The 3GPP study item focus on three types of devices:

[0003] (1) A first type of AloT device that is capable of a peak power consumption around one micro watt, has energy storage and the device is not capable of DL or UL amplification. The device’s UL transmission is backscattered on a carrier wave provided externally;

[0004] (2) A second type of AloT device that is capable of peak power consumption around a few hundred micro watts, has energy storage and the device is capable of DL or UL amplification. The device’s UL transmission is backscattered on carrier wave provided externally; and

[0005] (3) A third type of device that is capable of peak power consumption around a few hundred micro watts, has energy storage and the device is capable of DL or UL amplification. The device’s UL transmission is generated internally by the device.

[0006] The first and the second type of AloT devices are characterized by poor synchronization performance leading to high synchronization frequency offset (SFO). This impacts the transmission timing from device to the reader (D2R). Furthermore, the first and second type of device are expected to have an energy harvester module to charge its battery. During high energy level, the device may be capable of longer transmission duration and / or more transmissions whereas in low energy level the device may not be capable to transmit. The third type of device is the more capable of the three and it is expected to have higher synchronization accuracy and have higher level of energy.

[0007] The AloT devices are expected to be deployed on two different topologies:

[0008] -Topology 1 : the AloT device can communicate directly with the base station, e.g., gNB (where the gNB is the reader); and

[0009] -Topology 2: the AloT can communicate with an intermediate node that transfers the communication to the base station, e.g., gNB (i.e. intermediate node is the reader). Such an intermediate node can be a user equipment (UE), repeater or integrated access backhaul (IAB) node.

[0010] In order to maximize supported distance between reader and device, it has been proposed that devices can operate according to a duty cycle of alternating On and Off time periods. During an Off time period, a device harvests energy and runs a low power clock without attempting to receive signals. Configuring Off time periods much longerthan On time periods enables communication between reader and devices that take a long time to charge when relatively far from sources of RF energy.

[0011] If a device operates according to a duty cycle, the reader needs to have knowledge and / or have control over the timing of the On-periods during which communication between device and reader is possible. Before the first interaction between a reader and a AloT device, the reader has no knowledge of the timing of the On-periods used by the AloT device. In addition, the reader has no knowledge of the duration of the charging time (Off period) as it depends on the distance of the device to an RF source that can be used for energy harvesting. AloT devices also have no knowledge of the timing of possible transmissions from the reader. As a result, communication between device and reader can incur high latency and / or overhead. In a worst-case scenario, the reader may fail to communicate with the device indefinitely. A closely related further problem is that a device and reader that are initially synchronized may subsequently lose synchronization due to timing drift. Solutions to address these issues are desirable.SUMMARY

[0012] Aspects of the disclosed embodiments may address one or more of the foregoing issues by implementing methods for configuring and aligning activity cycles of multiple AloT devices with unknown synchronization states. To this end, aspects are described in the following embodiments to enable efficient acquisition, maintenance and / or reacquisition of synchronization between a reader and an ambient loT device. In this context, “synchronization” from a reader perspective can mean that the reader has knowledge of the periods during which a device receives or can receive a transmission from the reader.

[0013] According to certain aspects for a reader, a method may include the reader determining a target activity cycle for a group of devices. In this respect, an activity cycle includes a set of periods during which a device can receive and / or transmit (on-periods). A reader receives configuration for a target activity cycle from signaling (e.g. from a base station, e.g., gNB or an Ambient loT controlling entity). The configuration may include periodicity, time offset, duration of on-periods with reference to the timing of the serving cell of the reader.

[0014] An example method may further include the reader transmitting a first type of Sync transmission (“Sync- Start”) at the beginning of each on-period of the target activity cycle. In certain aspects, the Sync-Start transmission may include a pre-defined sequence of modulated symbols. As an example, the sequence may be dependent on a parameter of the target activity cycle such as periodicity.

[0015] The reader initiates an Active alignment procedure by transmitting a second type of Sync transmission (“Sync-Align”) multiple times within an Alignment period. In certain aspects the Sync-Align transmission may include a pre-defined sequence of modulated symbols and / or a payload. In an example, each Sync-Align transmission includes an indication of a duration of period from this transmission until transmission of a Sync-Start transmission. According to certain aspects, each Sync-Align transmission may include information on the applicable range of maximum duty rate for the activity cycle of a device. In this regard, a maximum duty rate is the maximum fraction of time a device can be in an on-period.

[0016] In one aspect, the reader may receive a feedback transmission from device(s) receiving the Sync-Align transmission. The reader may transmit Sync-Align transmissions repeatedly in quick succession within the Alignment period except during periods where it transmits a Sync-Start or may receive feedback from devices. The reader mayset the duration of an Alignment period to a multiple of the target activity cycle periodicity. In some examples, the reader may receive this duration of Alignment period from signaling (e.g. from a base station, e.g., gNB or an Ambient loT controlling entity).

[0017] In other aspects, the disclosed embodiments define methods for the AloT device. In one example method, an AloT device determines a maximum duty rate based on factors such as available power for energy harvesting. The AloT device determines an activity cycle compatible with the maximum duty rate. The AloT device selects a start time of on-period randomly. The AloT device receives a Sync-Align transmission from a reader indicating an applicable range of the maximum duty rate and a duration of period until transmission of a Sync-Start transmission. Under a condition that the maximum duty rate of the device is within the applicable range, the AloT device modifies its activity cycle such that the on-period overlaps with the timing of the Sync-Start transmission, to ensure the Sync-Start transmission from a reader is received. In this manner, multiple AloT devices in proximity can rapidly have their activity cycles synchronized to a target timing. Additional aspects, features and / or advantages may be described in the embodiments which follow.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, wherein like reference numerals in the figures indicate like elements, and wherein:

[0019] FIG. 1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented;

[0020] FIG. 1B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A according to an embodiment;

[0021] FIG. 1C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communications system illustrated in FIG. 1A according to an embodiment;

[0022] FIG. 1 D is a system diagram illustrating a further example RAN and a further example CN that may be used within the communications system illustrated in FIG. 1A according to an embodiment;

[0023] FIG. 2 is a timing diagram showing an example synchronization of Ambient loT (AloT) device(s) on- periods over a target activity cycle according to example embodiments;

[0024] FIG. 3 is a flow diagram illustrating an example method for a reader according to an embodiment; and

[0025] FIG. 4 is a flow diagram illustrating an example method of an AloT device according to an embodiment.DETAILED DESCRIPTION

[0026] FIG. 1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, includingwireless bandwidth. For example, the communications systems 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word discrete Fourier transform Spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0027] As shown in FIG. 1 A, the communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (ON) 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a station (STA), may be configured to transmit and / or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c and 102d may be interchangeably referred to as a UE.

[0028] The communications systems 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106, the Internet 110, and / or the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a NodeB, an eNode B (eNB), a Home Node B, a Home eNode B, a next generation NodeB, such as a gNode B (gNB), a new radio (NR) NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0029] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, and the like. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for a wireless service to a specific geographical area that may be relatively fixed or that may change over time. The cell may further be divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in desired spatial directions.

[0030] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0031] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 116 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed Uplink (UL) Packet Access (HSUPA).

[0032] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0033] 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.

[0034] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for instance using dual connectivity (DC) principles. Thus, the air interface utilized by WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., an eNB and a gNB).

[0035] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0036] The base station 114b in FIG. 1 A may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a roadway, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellularbased RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not be required to access the Internet 110 via the CN 106.

[0037] The RAN 104 may be in communication with the CN 106, which may be any type of network configured to provide voice, data, applications, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not shown in FIG. 1A, it will be appreciated that the RAN 104 and / or the CN 106 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may be utilizing a NR radio technology, the CN 106 may also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0038] The CN 106 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or the other networks 112. The PSTN 108 may include circuit-switched telephone networks that provide plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and / or the internet protocol (IP) in the TCP / IP internet protocol suite. The networks 112 may include wired and / or wireless communications networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

[0039] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multimode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0040] FIG. 1B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1B, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138, among others. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0041] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1 B depicts the processor 118 and thetransceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0042] The transmit / receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In an embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0043] Although the transmit / receive element 122 is depicted in FIG. 1B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0044] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit / receive element 122 and to demodulate the signals that are received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11 , for example.

[0045] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and / or the removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0046] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0047] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station (e.g., base stations 114a, 114b) and / ordetermine its location based on the timing of the signalsbeing received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by way of any suitable location-determination method while remaining consistent with an embodiment.

[0048] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a Virtual Reality and / or Augmented Reality (VR / AR) device, an activity tracker, and the like. The peripherals 138 may include one or more sensors. The sensors may be one or more of a gyroscope, an accelerometer, a hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, a humidity sensor and the like.

[0049] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the UL (e.g., for transmission) and DL (e.g., for reception) may be concurrent and / or simultaneous. The full duplex radio may include an interference management unit to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WTRU 102 may include a halfduplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the DL (e.g., for reception)).

[0050] FIG. 1 C is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0051] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c overthe air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0052] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, and the like. As shown in FIG. 10, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0053] The CN 106 shown in FIG. 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. While the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0054] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0055] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring user planes during inter-eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0056] 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.

[0057] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers.

[0058] Although the WTRU is described in FIGS. 1A-1 D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (e.g., temporarily or permanently) wired communication interfaces with the communication network.

[0059] In representative embodiments, the other network 112 may be a WLAN.

[0060] A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic in to and / or out of the BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. The traffic between STAs within a BSS may be considered and / or referred to as peer-to-peer traffic. The peer-to-peer traffic may be sent between (e.g., directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11e DLS or an 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an “ad-hoc” mode of communication.

[0061] When using the 802.11ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width. The primary channel may be the operating channel of the BSS and may be used by the STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example in 802.11 systems. For CSMA / CA, the STAs (e.g., every STA), including the AP, may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0062] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0063] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. The 40 MHz, and / or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately. The streams may be mapped on to the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0064] Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. The channel operating bandwidths, and carriers, are reduced in 802.11af and 802.11ah relative to those used in 802.11 n, and 802.11ac. 802.11 af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11 ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11 ah may support Meter Type Control / Machine-Type Communications (MTC), such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, forexample, limited capabilities including support for (e.g., only support for) certain and / or limited bandwidths. The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0065] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802.11n, 802.11ac, 802.11 af, and 802.11 ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 1 MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) settings may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which supports only a 1 MHz operating mode) transmitting to theAP , all available frequency bands may be considered busy even though a majority of the available frequency bands remains idle.

[0066] In the United States, the available frequency bands, which may be used by 802.11 ah, are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11ah is 6 MHz to 26 MHz depending on the country code.

[0067] FIG. 1 D is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0068] The RAN 104 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 104 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0069] The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing a varying number of OFDM symbols and / or lasting varying lengths of absolute time).

[0070] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without also accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with / connect to gNBs 180a, 180b, 180c while also communicating with / connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In the non-standalone configuration, eNode-Bs 160a, 160b, 160c may serve as a mobilityanchor for WTRUs 102a, 102b, 102c and gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for servicing WTRUs 102a, 102b, 102c.

[0071] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support of network slicing, DC, interworking between NR and E-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG. 1 D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0072] The CN 106 shown in FIG. 1 D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0073] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of non-access stratum (NAS) signaling, mobility management, and the like. Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types ofservices being utilized WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for MTC access, and the like. The AMF 182a, 182b may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0074] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 106 via an N11 interface. The SMF 183a, 183b may also be connected to a UPF 184a, 184b in the CN 106 via an N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP address, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, and the like. A PDU session type may be IPbased, non-IP based, Ethernet-based, and the like.

[0075] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, and the like.

[0076] The CN 106 may facilitate communications with other networks. For example, the CN 106 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local DN 185a, 185b through the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0077] In view of FIGs. 1A-1 D, and the corresponding description of FIGs. 1A-1 D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b, and / or any other device(s) described herein, may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more, or all, of the functions described herein. For example, the emulation devices may be used to test other devices and / or to simulate network and / or WTRU functions.

[0078] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or in an operator network environment. For example, the one or more emulation devices may perform the one or more, or all, functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. The one or more emulation devices may perform the one or more, or all, functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation device may be directly coupled to another device for purposes of testing and / or performing testing using over-the-air wireless communications.

[0079] The one or more emulation devices may perform the one or more, including all, functions while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communications via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0080] As mentioned previously, an Internet of Things (loT) system is based on connected devices / things (e.g., sensors) that can communicate with the network using small data payload and low transmission power. A 3GPP study item has recently focused on three types of Ambient loT (AloT) devices:

[0081] (1) A first type of AloT device that is capable of a peak power consumption around one micro watt, has energy storage and the device is not capable of DL or UL amplification. The AloT device’s UL transmission is backscattered on a carrier wave provided externally;

[0082] (2) A second type of AloT device that is capable of peak power consumption around a few hundred micro watts, has energy storage and the device is capable of DL or UL amplification. This type of AloT device’s UL transmission is also backscattered on a carrier wave provided externally; and

[0083] (3) A third type of device that is capable of peak power consumption around a few hundred micro watts, has energy storage and the device is capable of DL or UL amplification. This type of AloT device’s UL transmission is generated internally by the device.

[0084] The first and the second type of AloT device are characterized by poor synchronization performance leading to high synchronization frequency offset (SFO). This impacts the transmission timing from device to the reader (D2R). Furthermore, the first and second type of device are expected to have an energy harvester module to charge its battery. During high energy level, the devices may be capable of longer transmission duration and / or more transmissions whereas in low energy level the devices may not be capable of transmitting. The third type of AloT device is the more capable and it is expected to have higher synchronization accuracy and have higher level of energy.

[0085] The AloT devices are expected to be deployed on two different topologies:

[0086] -Topology 1 : the AloT device can communicate directly with the base station, e.g., gNB (i.e. gNB is the reader); and

[0087] -Topology 2: the AloT can communicate with an intermediate node that transfers the communication to the base station, e.g., gNB (i.e. intermediate node is the reader). Such an intermediate node can be a UE, also referred to herein as a wireless transmit receive unit (WTRU), a repeater, an integrated access backhaul (IAB) node and / or or similarly functioning devices.

[0088] To maximize supported distance between reader and device, it has been proposed that devices can operate according to a duty cycle of alternating on and off time periods. During an off time period, an AloT device harvests energy and runs a low power clock without attempting to receive signals. Configuring Off time periods much longer than on time periods enables communication between reader and devices that take a long time to charge when relatively far from harvest sources of RF energy.

[0089] If an AloT device operates according to a duty cycle, the reader should have knowledge and / or potentially have some control over the timing of the on-periods during which communication between device and reader is possible.

[0090] Before a first interaction between a reader and a device, the reader has no knowledge of the timing of the on-periods used by a respective AloT device. In addition, the reader has no knowledge of the duration of the charging time (Off period) of an AloT device, as it depends on the distance of the device to an RF source that can be used for energy harvesting. AloT devices also have no knowledge of the timing of possible transmissions from the reader. As a result, communication between device and reader can incur high latency and / or overhead. In a worst-case scenario, the reader may fail to communicate with the device indefinitely. A closely-related further problem is that an AloT device and reader that are initially synchronized, may subsequently lose synchronization due to timing drift.

[0091] Example embodiments may relate to methods for configuring and aligning activity cycles of multiple devices with unknown synchronization states.

[0092] In certain embodiments, a method for an AloT reader device, referred to herein as “reader,” may initially include the reader determining a target activity cycle for one or more, e.g., a group of AloT devices. In one example, an activity cycle includes a set of periods during which an AloT device can receive and / or transmit, referred to as “On- periods” “on periods” “on-periods” or the like. In an example, a reader, e.g., a WTRU, may receive a configuration for a target activity cycle from signaling (e.g. from the base station, e.g., gNB or an Ambient loT controlling entity). In various embodiments, the configuration may include a periodicity, time offset, and / or a duration of on-periods, for example with reference to the timing of the serving cell of the reader.

[0093] In an example embodiment, the reader transmits a first type of Sync transmission, referred to herein as “Sync-Start,” at the beginning of each on-period of the target activity cycle. In one example, the Sync-Start may include a pre-defined sequence of modulated symbols. As an example the sequence may be dependent on a parameter of the target activity cycle such as periodicity.

[0094] Next, the reader may initiate an Active alignment procedure by transmitting a second type of Sync transmission, referred to herein as “Sync-Align,” multiple times within an Alignment period. In one example, the Sync- Align may include a pre-defined sequence of modulated symbols and / or a payload. In various embodiments, each Sync-Align transmission may include an indication of a duration of period from this transmission until a next transmission of a Sync-Start. In certain examples, each Sync-Align transmission may include information on the applicable range of maximum duty rate for the activity cycle of an AloT device. A maximum duty rate is the maximum fraction of time an AloT device can be in an on-period.

[0095] The reader may receive a feedback transmission from device(s) receiving the Sync-Align transmission. In example embodiments, the reader may transmit Sync-Align transmissions repeatedly in quick succession within the Alignment period, except during periods where it transmits a Sync-Start and / or expects to potentially receive feedback from AloT devices. In one example, the reader may set the duration of an Alignment period to a multiple of the target activity cycle periodicity. In some embodiments, the reader may receive this duration from signaling (e.g. from the base station, e.g., gNB or an Ambient loT controlling entity / function).

[0096] In certain embodiments, a method for an AloT device, also referred to herein as “loT device,” or simply “device,” may initially include the device determining its maximum duty rate based on factors such as available power for energy harvesting and / or energy storage capability. The AloT device may next determine an activity cycle compatible with the determined maximum duty rate. In an example, the AloT device selects a start time of its on-period randomly.

[0097] The AloT device receives a Sync-Align transmission from a reader indicating an applicable range of maximum duty rate and a duration of a period until the reader transmits a Sync-Start transmission. Under a condition that the maximum duty rate of the device is within the applicable range indicated by the reader, the AloT device modifies its activity cycle such that its on-period overlaps with the timing of the Sync-Start transmission by the reader. In this manner, multiple AloT devices in proximity can rapidly have their activity cycles synchronized to a target timing.

[0098] The embodiments described in the following disclosure enable efficient acquisition, maintenance and / or reacquisition of synchronization between a reader and an ambient loT device. In this context, “synchronization” from a reader perspective can mean that the reader has knowledge of the periods during which an AloT device receives or can receive a transmission from the reader.

[0099] As used herein, a “device” may generally refer to an Ambient loT device, an loT device, a machine type communication (MTC) device or a WTRU with reduced capability (e.g., reduced power capability). A “reader” may generally refer to a base station, e.g., gNB, an Integrated Access Backhaul (IAB), a device acting as relay or an intermediate WTRU acting as a relay between the base station and the device.

[0100] In certain scenarios, a reader may be a base station, e.g., gNB. In other scenarios, a reader may be a WTRU under control or coverage of a base station. When the reader is a WTRU, it may receive configurations relatedto AloT operation from a gNB or from another entity / function controlling AloT operations, e.g. an AloT controller. Such a configuration may be received by physical layer, MAC or higher-layer signaling (RRC or other protocol). Unless otherwise specified, any parameter or configuration utilized by a reader may be obtained using such signaling.

[0101] Synchronization capability. In some examples, a synchronization capability can be associated with sampling frequency offset (SFO). For example, a first value of SFO can be associated with a first synchronization capability and a second value of SFO can be associated with a second synchronization capability. In another example, a synchronization capability can be associated with a jitter value. For example, a first value of jitter can be associated with a first synchronization capability and a second value of jitter capability can be associated with a second synchronization capability.

[0102] In the following embodiments, a transmission from a device to reader (D2R) can be a transmission of data information, transmission of control information or preamble / midamble / postamble / reference signal transmission. A D2R transmission can include an identify associated to the device. A D2R transmission can be transmitted following receiving a scheduling from a reader or alternatively initiated by the device. For example, a device can initiate a transmission for initial access.

[0103] In certain embodiments, the device can be pre-configured with one or multiple preamble / midamble / postamble / reference signal transmission parameters and the reader indicates to the device which preamble to use for the transmission. In one example, each preamble can be configured with a different sequence. A transmission from reader to device (R2D) can be transmission of control and / or data information.

[0104] As used herein, a time unit may refer to a pre-defined duration in terms of an absolute unit of time such as a second, millisecond and the like. Alternatively, a time unit may refer to a pre-defined duration in terms of a certain number of symbols, slots or frames. Alternatively, a time unit may refer to a time period indicated dynamically by a transmission such as a synchronization signal, sync transmission, preamble, midamble or postamble transmission.

[0105] Duty cycled operation is described. In various embodiments, a device may operate according to alternating first and second periods characterized by the following examples.

[0106] A first period (“On” or “active time”) during which the device enables reception and / or transmission capabilities.

[0107] A second period (“Off) during which the device disables reception and / or transmission capabilities for at least some types of receptions and / or transmissions. During this second period, the device may, for example, set its circuitry to enable energy harvesting from a radio source.

[0108] A duty cycle or duty cycle ratio may be defined as the ratio between on and off periods.

[0109] During the on-period, a device consumes energy accumulated in energy storage (e.g. capacitor or battery) according to a first (discharging) rate while during the off-period, a device may accumulate energy according to a second (charging) rate. The discharging and charging rates may depend on various factors. For example, the charging rate may depend on the received power available from a radio source which varies depending on the distance from the radio source.

[0110] A maximum on-duration may be defined as the maximum duration of an on-period such that there is remaining energy at the end of the on-period. The maximum on-duration may depend on factors such as energy storage capacity and discharging rate.

[0111] A maximum duty cycle may be defined as the maximum duty cycle such that a device always has some remaining energy (i.e. more than zero) at the end of an on-period. The maximum duty cycle may be different for different devices, and for a same device the maximum duty cycle may vary over time depending on any of the above- mentioned factors for the charging and discharging rates.

[0112] An activity cycle may include a specific time pattern defining On and Off periods for a device. In example embodiments, an activity cycle may be characterized by at least one of the following:

[0113] -A periodicity, defined as a time difference between the start of two successive On-periods (or two successive Off periods);

[0114] -The duration of the On-period, or maximum thereof, or minimum thereof;

[0115] -The duration of the Off period, or maximum thereof, or minimum thereof;

[0116] -An offset, defined as a time difference between a reference time and the start of an On-period (or alternatively of an Off-period). In this regard a reference time may be derived from, or correspond to, the transmission time of a synchronization signal; and / or

[0117] -A set of start times, where each start time corresponds to the start of an On-period (or of an Off period). In various examples, a start time may be identified by, for example,, a time index.

[0118] Embodiments of device operations are now described in the following examples (1)-(9).

[0119] (1) Determination of an activity cycle. A device may select at least one parameter determining an activity cycle from a set of pre-defined parameters. For example, the device may select a periodicity from a defined set of {2, 4, 8, 16, 32} or a defined set of {10, 20, 40} time units. In another example, the device may select the maximum duration of the On-period from a defined set such as {1 , 2, 4} time units, or the maximum duration of the Off period from a defined set such as {9, 19, 39} time units. The device may be pre-configured with the defined set(s). The device may subsequently receive signaling explicitly configuring at least one defined set and / or adding at least one element to at least one defined set.

[0120] In an example embodiment, a device may select at least one parameter determining an activity cycle from an estimation or measurement of the maximum duty cycle or of the charging time or of the minimum number of time units required to maximize its energy storage from zero under prevailing conditions. For example, the device may select the duration of the Off period as the smallest period from the defined set that is greater than the charging time. In case there is no period from the defined set that is greater than the charging time, the device may select the longest Off period and an On-period (or maximum On-period) such that the amount of energy depleted during the On-period is no larger than the energy that can be charged during the longest Off period.

[0121] The device may determine that an activity cycle is supported if operating according to the activity cycle under certain assumptions would guarantee that the device would have sufficient energy during an On-period. An example assumption may include, e.g., a percentage of an On-period during which the device may transmit.

[0122] (2) Early interruption of On-period. In certain embodiments, a device may shorten the duration of an On- period if it has not detected a signal such as an applicable sync transmission or other applicable transmission after a maximum detection time from the start of the On-period, where the maximum detection time may be less than the duration or maximum duration of the On-period. In this case, the device may then turn off reception and extend the Off period accordingly.

[0123] (3) Flexible On-period. In some embodiments, a device may be configured with more than one On- period. For example, a device may be configured with a minimum On-period and a maximum On-period. The device may decide to use either the minimum On-period or the maximum On-period based on any of the conditions described herein. For example, the device may operate with at least a minimum On-period, and may decide to extend to a maximum On-period based on any of: (i) Transmissions (or lack thereof) in the minimum On-period (e.g., synchronization signal, data explicit indication from the reader); and / or (ii) past measurements of the activity within the minimum On-period or past decisions of whether a minimum or maximum On-period was used.

[0124] (4) Determination of synchronized or unsynchronized state. In certain embodiments, a device may determine that it is in a synchronized state if the period since reception of a last applicable sync transmission, or other applicable transmission, is not higher than a threshold. In examples, the threshold may be a pre-defined number of time units or a pre-defined factor times the periodicity of the current activity cycle or the periodicity of the applicable sync transmission. Otherwise, the device may determine that it is in an unsynchronized state. The device may also determine that it is in an unsynchronized state upon reception of signaling from a reader indicating the same.

[0125] An applicable sync transmission may include of any sync transmission detected by the device, or of any sync transmission indicating a periodicity and / or offset corresponding to the periodicity and / or offset of the current activity cycle, or of a sync transmission indicating change of activity cycle or indicating timing of a subsequent sync transmission as described in later paragraphs. An applicable transmission may consist of a transmission such as a pre-defined preamble or a transmission including payload that can be decoded by the device.

[0126] (5) Activity cycle dependency on synchronized / unsynchronized state. In example embodiments, a device may receive based on an activity cycle that depends on whether the device is in a synchronized or an unsynchronized state. For example, while in an unsynchronized state the device may use a periodicity from a defined set of periodicities and / or On-period durations applicable to an unsynchronized state. Such a set of periodicities may be selected in a way to maximize the probability that at least one of the unsynchronized device On-periods would overlap with a sync transmission from the reader. For example, if a defined set of periodicities for a sync transmission or for activity cycle in synchronized state would be {8, 16, 32} time units, a defined set of periodicities applicable to unsynchronized state may be {7, 15, 31} time units. In another example, while in unsynchronized state, the duration of the On-period and the periodicities may be reduced by a pre-defined fraction to maximize the likelihood of detecting an applicable sync transmission from the reader. In another example, while in an unsynchronized state, the device may shift the start of each On-period (or Off-period) by a randomly selected number of time units.

[0127] (6) Synchronization request. In some embodiments, a device in an unsynchronized state may, under at least one condition, transmit a request to trigger transmission of (additional) sync messages by reader(s) that may be in proximity to the device. Examples of the at least one condition may include:

[0128] -Duration since the last time the device was in a synchronized state above a pre-defined first threshold and / or below a pre-defined second threshold;

[0129] -Duration since a last transmission of the synch request being above a pre-defined third threshold;

[0130] -The device detected an RF source such as a continuous wave (CW) with a signal strength above a threshold;

[0131] -The device detected RF energy (e.g. received signal strength indicator) or a signal from another device being above a corresponding threshold.

[0132] -The device detected a sync transmission, such as any sync transmission or a sync transmission for the purpose of triggering the synchronization request by the device.

[0133] In some embodiments, the device may transmit the synch request on a pre-defined frequency resource. In case the device detected a sync transmission from a reader, the device may transmit the synch request after a predefined period following reception of the detected sync transmission. In certain examples, the synch request may indicate information on supported activity cyde(s) and / or maximum duty cycle and / or charging time. The device may indicate this information by selecting one of a pre-defined set of frequency resources. For example, the device may transmit on a first (or second) frequency resource if the maximum duty cycle is above (or below) a pre-defined threshold.

[0134] (7) Indication of activity cycle information to the reader. In some embodiments, a device may provide at least one parameter defining a current activity cycle or used for the determination of an activity cycle (such as charging time or maximum duty cycle) in a transmission to the reader. In some embodiments, a device may provide information on at least one supported activity cycle as defined in the above. For example, the device may provide the information following a request by a reader to provide a set of supported activity cycles or possibly a maximum duty cycle.

[0135] In some cases, a device may report that its current activity cycle is not (or no longer) supported. At least one of the above information may be transmitted by the device: (i) when the device performs D2R transmission or following a request by the reader, e.g., addressed to the device or addressed to any device as part of a contentionbased procedure.

[0136] The reader request may include information or condition on applicable activity cycles or supported activity cycles or maximum duty cycle. In one example, the device may report the information only if satisfies the condition included in the request. The information reported by the device may be included, for example, in a stand-alone control message or may be appended or included in a control portion of a D2R message.

[0137] In some embodiments, the device may report information only if the information was not previously provided or if the information has changed or has changed by more than threshold since the last time it was provided. In some embodiments, the device may report information only if it was in unsynchronized state, or only if it is in synchronized state. The applicable synchronization state of the device may be included in the synchronization request.

[0138] Embodiments for modification of activity cycle may be utilized. In certain examples, the device may modify its activity cycle if the current activity cycle is no longer supported, e.g., due to a change of maximum duty cycle. In such case, the device may select a new activity cycle from a set of supported activity cycles.

[0139] In certain embodiments, a device may modify its activity cycle if a supported activity cycle with a higher duty cycle is available. In one example, the device may select the new activity cycle such that the On-periods of the new activity cycle overlap with On-periods of the previous activity cycle.

[0140] According to some embodiments, a device may modify its activity cycle after reception of a sync transmission, as described in following paragraphs (sync-align). After reception of the sync-align transmission, the device may perform a transmission following the end of the sync-align transmission to acknowledge reception and indicate that the device is modifying its active cycle. In one example, the device may perform such a modification under a condition that the period since last modification of the activity cycle due to reception of a sync transmission, is above a pre-defined threshold. Alternatively, in case the device receives two sync transmissions resulting or indicating modification of the activity cycle within a period less than a threshold, the device may revert to a pre-defined activity cycle and determine that it is in an unsynchronized state. After modification of its activity cycle, the device may include information on the modified activity cycle in a subsequent D2R transmission or upon request by the reader as described in the above.

[0141] (8) Transmission of synchronization signal by device. A device may transmit signals such as preamble, midamble, postamble as part of a D2R transmission for the purpose of providing timing information to the reader. The device may also transmit a D2R transmission containing only a sequence for the purpose of providing timing information (including possible drift) to the reader. Such sequence may be a pre-defined sequence, such as sequence alternating “high” and “low” amplitudes.

[0142] (9) Timing acquisition correction by device. In some embodiments, a device may first acquire synchronization information such as the duration of a time unit based on reception of a sync transmission or other synchronization signal (such as preamble, midamble, postamble) transmitted by a reader. The device may determine the durations of On and Off periods based on the determined duration of the time unit and the selected activity cycle defined in terms of a number of time units. A device may subsequently receive further synchronization information to update or correct the duration of a time unit or “clock drift”. After updating the duration of a time unit, the device may also update the durations of On and Off periods of its activity cycle accordingly.

[0143] In one embodiment, a device may correct the Start time of On-periods (and / or Off periods) and possibly the duration of a time unit based on determining the duration between the start of an On-period and the start of a Sync transmission, and comparing this duration to a pre-defined or configured duration. For example, if the device determines that the Sync transmission is received 3 ms after the start of the On-period and the configured duration is 1 ms, the device may delay the start time of subsequent On durations by 2 ms.

[0144] According to one embodiment, a device may correct the duration of a time unit using, for example, one of following examples. The device may use phase-locked loop (PLL) or frequency-locked loop (FLL) (if so equipped) applied to, e.g., a synchronization sequence. Alternatively, the device may receive a calibration signal with phase difference or frequency difference between the uncorrected (drifted) synchronization or clock signal and the correct synchronization signal. Such a calibration signal may correspond to the output of an error detected in PLL and FLL circuits. The device may use the amplitude of the signal to correct the duration of a time unit.

[0145] Embodiments for provision of synchronization information are now described. In some examples, the reader may transmit at least one signal or message to provide synchronization information to devices. Such signal or message is referred to as “Sync” transmission. In various embodiments, synchronization information may include at least one of the following:

[0146] -Indication to modify the activity cycle;

[0147] -Indication of a reference time for the activity cycle;

[0148] -Indication of the timing of subsequent synchronization transmission(s);

[0149] -Indication of the duration of a time unit;

[0150] -Indication of applicable duty cycle or maximum duty cycle;

[0151] -Indication of applicable periodicity of the activity cycle;

[0152] -Indication of a time index;

[0153] -Synchronization request;

[0154] -Indication of a timing correction; and / or

[0155] -Indication of targeted devices;

[0156] In various examples, a sync transmission may be combined with, or be part of, an R2D transmission that provides other information or control to device(s). For example, a sync transmission may be combined with an R2D transmission triggering contention-based access (e.g. “query”) or indicating that a counter for access should be decremented (e.g. “query rep”), if applicable.

[0157] Embodiments for a reader to provide indication to a device to modify the activity cycle of the device are disclosed. A Sync transmission that includes indication to modify the activity cycle may be referred to as a “Sync-al ign” or “Align” transmission. The information for modifying the activity cycle may include at least one of the following examples (1)-(3):

[0158] (1) The modification information may include a time offset. The time offset may be positive or negative. The device may modify its activity cycle to a delay / advance of the start of a next On-period or by an indicated time offset or set the start of next On-period to a time corresponding to a reference time plus the indicated time offset. As examples, the reference time may correspond to the reception time of the start or end of the sync transmission containing the modification of activity cycle (Sync-align) or the reception time of the start or end of another sync transmission, such as the sync transmission received during a previous On-period.

[0159] (2) The modification information may include a periodicity. For example, the device may modify its activity cycle such that the periodicity after the modification is the indicated periodicity.

[0160] (3) The modification information may include a duration for the On-period (e.g. subsequent On-periods). For example, the device may modify its activity cycle such that the duration of its On-period after the modification, is the indicated duration.

[0161] In case the sync-align transmission is associated to or contained within a R2D transmission initiating a contention-based procedure, a device may respond to this procedure under a condition that it was in an unsynchronized state prior to reception of the sync-align transmission. The device may update its activity cycleaccording to the sync-align transmission prior to selecting a time resource (possibly random time resource) for responding to the R2D transmission.

[0162] In various embodiments, the reader provides indication of an applicable duty cycle or maximum duty cycle. In this regard, the information indicated by the reader may include an applicable range of duty cycles or maximum duty cycles. In one example, the device may only modify its activity cycle if its maximum duty cycle is within the applicable range. In some examples, the range(s) may be expressed by the reader using one or more thresholds. For example, the information may include a single threshold (say 5%). In this case, the modification of activity cycle may be applicable only to those devices for which their current maximum duty cycle is 5% or more. In another example, the information may include two thresholds (say 2% and 5%). In this case, the modification of activity cycle may be applicable only to those devices for which their current maximum duty cycle is between 2% and 5%. Various alternatives for this example modification information are also possible.

[0163] The information provided by the reader may include more than one applicable range of duty cycles. In such case, the information may include activity cycle information for each of the more than one applicable ranges. For example, the information may indicate a first offset and period for a duty cycle above a first threshold but below second threshold, and a second offset and period for a duty cycle above second threshold. Various alternatives for this example modification information are also possible.

[0164] Embodiments for a reader to select the synchronization information based on suggestion by the device are also disclosed. In one example, the reader may receive one or more suggested duty cycles, activity cycle, etc.,, from the device(s). In one example, such suggestion by the device(s) may come while using a first synchronization information for operation (e.g., default or preconfigured). The reader may select one or more of the suggested synchronization information suggested by a device. Such selection may also be performed by a network node separate from the reader. Such selection may be determined by the properties and / or amount of data buffered or expected at the reader, knowledge of the location of the device relative to the reader, channel measurements, etc. Following such selection, the reader may send the selected synchronization information to the device for defining the devices duty cycle, activity cycle, etc. Alternatively, the reader may select a compatible synchronization information to one or more of the suggested synchronization information from the device(s). For example, the reader may select a compatible synchronization information from a table of preconfigured or specified equivalences. For example, such table may further be specific to the device type or capabilities of the device. Specifically, based on the device capabilities and the suggested synchronization, the reader may select an equivalent synchronization from a capability-specific table, and send the determined synchronization to the device.

[0165] In certain example embodiments, the reader provides indication of the start time of an On-period to a device. The transmission timing of a sync transmission may indicate the start time of an On-period for a device. Such sync transmission may be referred to as a “Sync-Start” transmission. In one example, a device may target that a Sync-Start transmission is received within a pre-defined or configured time window at the beginning of an On-period. In some examples, the device may perform timing corrections for the activity cycle and / or its clock when the Sync-Start transmission is received outside of this time window, such that subsequent Sync-Start transmissions fall within the window in subsequent On-periods.

[0166] In some embodiments, the reader provides information indicating the timing of subsequent synchronization transmission(s). The information may include an indication of when a subsequent transmission such as a synchronization transmission will occur. For example, the information may indicate a duration in time units between the reception of the sync transmission containing the indication and the next sync transmission.

[0167] In some embodiments, the reader provides information indicating the periodicity applicable to the sync transmission. The information may include an indication of a periodicity applicable to the sync transmission. In this case, a device may determine that it is synchronized only if it receives a sync transmission that indicates a periodicity that matches the periodicity of its active cycle. In various other embodiments, information may be provided indicating applicable maximum duty rate, minimum charging time, or any other factor that may be used to determine an activity cycle.

[0168] In some embodiments, the reader provides information indicating a time index applicable to the sync transmission. The information may include a time index such as a slot number or the like. A device may determine that it is synchronized only if it receives a sync transmission that indicates a time index included in the set of time indices for the start of the On-period, if the active cycle is defined in this way.

[0169] According to certain embodiments, the reader provides synchronization request to the device(s). The information may include a synchronization request by the device, as described in previous paragraphs. In response, a device may report information on its current activity cycle, supported activity cyde(s), maximum duty rate, minimum charging time and the like. The device may also transmit a synchronization sequence such as midamble, preamble, postamble for the purpose of calibration.

[0170] The reader synchronization request may be applicable to any device in an unsynchronized state. Alternatively, the synchronization request may be applicable to a specific device identified in the request. In one example, the reader may transmit such request only under a condition that the signal strength received from the device is above a threshold. In one example, the reader may receive configuration for this threshold from a base station, e.g., gNB or AloT controller / function.

[0171] In example embodiments, the reader provides information by a property of the sync transmission or as payload. The reader may indicate at least one of the above information, including the type of information provided and / or the type of sync transmission, by using one of the following example examples.

[0172] In one example embodiment, the reader may select one of a set of pre-defined sequences for the sync transmission. A sequence may be defined, for example, by a specific sequence of high and low values (in terms of e.g. amplitude) or a specific sequence of bits encoded using a line code. In another example, the reader may encode the information as a payload in the sync transmission, e.g. using a same example as for other R2D transmissions.

[0173] According to some embodiments, the reader provides information indicative of a timing correction to the device(s). In one example, the reader may indicate a timing correction in a sync transmission. For example, the reader may transmit a sync transmission indicating that the start of an On-period should be delayed by a certain number of time units or advanced by a certain number of time units. The number of time units may be pre-defined, e.g. one (1) time unit. For example, the reader may transmit a first sync transmission containing a timing correction indicating “delay” before transmitting a second sync transmission indicating the targeted start of an On-period. The reader maythen transmit a third sync transmission containing a timing correction indicating “advance.” A device that starts its On- period too early due to timing drift may receive the first sync transmission and adjust the start of the On-period accordingly, while a device that starts its On-period too late due to timing drift may receive the third sync transmission and adjust the start of the On-period accordingly.

[0174] In some examples, the reader may indicate a timing correction specific to a device in a sync transmission. In this case, the sync transmission may include the identity of the device to which the timing correction applies. The reader may first receive a D2R transmission from the device containing synchronization signal such as preamble, midamble, postamble or a standalone synchronization sequence. The reader may receive this transmission as part of a contention-based access procedure. Alternatively, the reader may transmit a synchronization request to receive the D2R transmission containing a synchronization sequence from the device and determine a timing drift (such as a difference in duration between a time unit at the reader and a time unit at the device). For some devices, the reader may provide a timing correction using a calibration signal corresponding to the output of an error detected in PLL or FLL circuits.

[0175] In some example embodiments, the reader provides information indicating the duration of a time unit. The information may include an indication of the duration of a time unit applicable to at least synchronization procedures. For example, the sync transmission may consist of a pre-defined sequence of high and low values (in terms of e.g. amplitude). The device may determine the duration of a time unit as the time difference between successive low-to- high transitions (or high-to-low transmissions) or between a low-to-high transition and a high-to-low transition. For example, the reader may send a calibration signal to the device wherein the calibration signal may contain at least one symbol encoded in a specific coding scheme. For example, the calibration signal may contain bit 0 encoded with Manchester encoding (e.g., bit 0 may be encoded as a symbol consisting of a high value (e.g., high voltage) followed by a low value (e.g., low voltage)). In another example, the calibration signal may contain bit 0 encoded with Pulse Interval Encoding.

[0176] The reader may indicate to the device the alignment value (e.g., n, m, etc., in FIG. 2) in terms of the duration of the calibration signal or in terms of a value computed from the calibration signal. For example, n may be n = MTs wherein Ts may be the duration of the calibration signal and M may be an integer. M may be pre-determined and / or configured / signaled.

[0177] In one method, the reader may indicate to the device the alignment value during a random-access procedure. In a random-access procedure, the reader may receive from a device an initial signal and / or message such as a (random) device ID. The reader may transmit to the device an alignment value as part of the response to the initial transmission, for example, as part of an acknowledgment message. Alternatively, the reader may send to the device the alignment value in a separate signal / message. The reference time the device uses to measure the time duration indicated by the alignment value may be pre-determined and known to both the reader and the device. For example, the duration corresponding to the alignment value (e.g., n, m, etc.) may start from the end of the alignment message or the message containing the alignment value.

[0178] Referring to FIG. 2, an example timing diagram 200 is shown for a method of synchronizing a reader with one or more AloT devices or other power-restrained device. FIG. 3 shows a method 300 for a reader performing adevice synchronization that corresponds with the FIG. 2 example timing diagram 200. Accordingly, details of both FIG. 2 diagram 200 and FIG. 3 method 300 will be described together with reference numerals that correspond to the respective figure, i.e. , 2## referring to FIG. 2, and 3## referring to FIG. 3.

[0179] In FIG. 3, an active alignment procedure 300 using sync-align transmissions (e.g., FIG. 2; 210, 212, 214, 215 and 217) is shown. A reader may initiate procedure 300 to accelerate acquisition of synchronization by devices in its proximity by transmitting at least one type of Sync transmission.

[0180] Initially, a reader determines 305 a target activity cycle (e.g., FIG. 2; 205) to receive / read information from one or more, or a group of loT devices. Determination 305 can be based on configuration or signaling from a base station, e.g., gNB or AloT controller as previously described. For example, the reader may determine a configuration for the target activity cycle 205 (e.g. periodicity, On-period duration) from higher layer signaling. If the reader is a WTRU, parameters of the target activity cycle 205 may be expressed in terms of new radio (NR) time units such as frame, subframe, slot, and may be referred to the timing (e.g. system frame number) of the serving cell of the WTRU. Next, the reader may transmit first and second types of Sync transmissions according to the following examples (1) and (2):

[0181] (1) A first type of Sync transmission (e.g., “Sync-Start” 215, 217) may be transmitted 310 with a first periodicity (T). The first periodicity (T) may correspond to the periodicity of the target activity cycle 205. Each Sync- Start transmission 215. 215 may be transmitted 310 at the beginning of an On-period of the target activity cycle, plus possibly a short time offset. Upon reception of Sync-Start transmission during an On-period (not shown), a device may determine that it is synchronized.

[0182] (2) A second type of Sync transmission (e.g., “Align” or “Sync-Align” 210, 212, 214) may be transmitted 315 multiple times within the period (T) between two successive Sync-Start transmissions 215, 217 of the first type. In certain embodiments, each such Sync-Align transmission 210, 212, 214 may indicate a duration of the period between the transmission of the current Sync-Align transmission and the transmission of the next Sync-Align transmission, or possibly a subsequent Sync-Start transmission. In some embodiments, each Sync-Align transmission may indicate a different value for this duration. In some examples, the reader may receive 320 device to reader (D2R) transmissions / feedback, e.g., 230, 232, from the device(s) following each Sync-Align transmission, confirming that the Sync-Align transmission was received by at least one device.

[0183] In the embodiment of FIGs. 2-3, the reader may transmit 310 a Sync-Start message / signal 215, 217 at, or offset in, the beginning of each On-period of the determined activity cycle 205. For unsynchronized devices, which happen to be in an On-period (not shown), the device(s) receiving the Sync-Start transmission 215 may synchronize their activity cycle, if not already synchronized, based on the Start-Sync transmission 215. In one embodiment, the Sync-Start transmission 215, 217 may be the same as a Sync-Align transmission 210, 212, 214, but indicating a duration of zero (0). The device(s) receiving the Start-Sync transmission 215, 217 may determine that it is synchronized when it receives such transmission during an On-period. As shown in FIG. 2, this is not the case and initial On-periods of the device(s) are represented by dashed lines 220.

[0184] The reader may next transmit 315 successive Sync-Align transmissions 210, 212, 214, continuously or regularly, over a period T, except possibly during periods reserved for feedback from devices, if supported, and duringperiods where Sync-Start transmissions are transmitted. Such period may be referred to as an alignment period and may be set to a multiple of the first periodicity of the Start-Sync transmission 215, 217. The successive sync-align transmissions 210, 212, 214 allow reception by most or all devices in proximity of the reader, that may be in an unsynchronized state and using an “initial” activity cycle and On-period 220. Such devices may modify their activity cycle such that their On-periods match a target On-period starting with the reception of a Sync transmission, as shown in the FIG. 2. The reader may set the alignment period based on a maximum periodicity of an activity cycle expected for the devices in proximity. In some embodiments, the reader may receive a configuration for such maximum periodicity and / or alignment period. In various embodiments, the Sync-Start and Sync-Align transmissions may indicate an applicable maximum duty rate (or range of duty rates) for the activity cycle of the device(s) as described previously. This enables devices that are not capable of a duty cycle compatible with the reader’s target activity cycle to ignore / not participate in synchronization attempts.

[0185] In various embodiments, the reader awaits / receives 320 feedback from devices receiving the first and / or second type of sync signals, and based on received feedback, may provide adjustment information to devices if needed as described previously.

[0186] In some examples, the reader may transmit first and second Sync-align transmissions with corresponding first and second offsets and possibly first and second applicable periodicities, such that the times indicated by the first and second Sync-align transmissions correspond to different instances of a Sync-Start transmission. This approach may enable balancing the number of devices between different Sync transmissions.

[0187] In some embodiments, a condition for initiating an active alignment procedure is used. A reader may initiate an active alignment procedure as described above when at least one of the following conditions occurs:

[0188] -After a period since the last initiation (or completion) of an active alignment procedure. The reader may receive the duration of this period from higher layer signaling;

[0189] -Upon reception of signaling from gNB or AloT controller requesting such procedure;

[0190] -After completion of an inventory procedure or contention-based access procedure;

[0191] -If the number of Sync-align transmissions for which feedback from devices was received is above a threshold. This threshold may be configured by higher layers;

[0192] -If the position of the reader has changed by more than a certain distance threshold since the last active alignment procedure; and / or

[0193] -If a measurement such as RSRP, RSRQ at the reader has changed by more than a threshold since the last active alignment procedure. In the above, the reader may receive configuration for the value of any threshold or may use pre-defined value.

[0194] In other embodiments, a reader may also initiate the active alignment procedure with non-continuous transmission of Sync-align transmissions within a period. The transmission times of the sync-align transmissions may be determined randomly (e.g. according to a Poisson process).

[0195] Referring to FIG. 4, a example method 400 for an AloT device participating in an active alignment procedure with a reader is shown. Initially, an AloT device may determine 405 a maximum duty rate based on device capabilities and / or energy factors such as available power for energy harvesting. The AloT device next determines 410 an activitycyde of On and Off periods compatible with the determined maximum duty rate and selects a start time of an On- period, e.g., randomly. During an On-period, the AloT device receives 415 a Sync transmission (e.g., Sync-Start or Sync-Align depending on when the device On-period and the target activity cycle of the reader transmitting them) from a reader indicating an applicable range of the maximum duty rate and a duration of period until transmission of a next Sync transmission, (e.g., Sync-Start transmission) by the reader. Under a condition 420 that the device’s determined maximum duty rate at step 405 is within the applicable range indicated by the reader, the AloT device modifies 425 its activity cycle such that one of its On-periods overlaps with the timing of the reader’s Sync-Start transmission, to ensure the Sync-Start transmission from the reader is received. In this manner, multiple AloT devices in proximity can rapidly have their activity cycles synchronized to a target timing.

[0196] Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer- readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

CLAIMSWhat is Claimed:1 . A method for a reader, the method comprising: performing an alignment process to synchronize one or more Internet-of-Things (loT) devices to a target activity cycle of the reader that includes a set of on-periods in a time interval, wherein each on-period of the set of on-periods is a duration in which the one or more loT devices may communicate with the reader when synchronized, wherein the alignment process is performed over one or multiples of the time interval, the alignment process comprising, transmitting a first type of synchronization signal at a first on-period of the set of on-periods in the target activity cycle; and periodically transmitting a second type of synchronization signal during each subsequent on-period of the set of on-periods, wherein the second type of synchronization signal indicates a time duration until a next transmission of the first type of synchronization signal.

2. The method of claim 1 , wherein the second type of synchronization signal further indicates a duty rate of on-time for an loT device to meet the determined target activity cycle.

3. The method of claim 1 , wherein the alignment process further comprises: receiving, in response to the transmitted first type or the second type of synchronization signal, feedback of data or control information from at least one loT device.

4. The method of claim 1 , wherein the first type of synchronization signal comprises a sync-start signal and wherein the second type of synchronization signal comprises a sync-align signal.

5. The method of claim 1 , wherein the target activity cycle is determined from configuration information received from one of a base station or an loT controlling entity, wherein the configuration information indicates a duration of the target activity cycle and one or more of, a duration and periodicity of each on-period of the set of on-periods or a time offset of each on-period of the set of on-periods.

6. The method of claim 1 , wherein the one or more loT devices are ambient loT (AloT) devices.

7. A reader comprising: a processor; and a transceiver communicatively coupled with the processor, wherein the processor and the transceiver are configured to: perform an alignment process to synchronize one or more Internet-of-Things (loT) devices to a target activity cycle of the reader that includes a set of on-periods in a time interval, wherein each on-period of the set of on-periods is a duration in which the one or more loT devices may communicate with the reader when synchronized, wherein the alignment process is performed over one or multiples of the time interval, the alignment process comprising,transmitting a first type of synchronization signal at a first on-period of the set of on-periods in the target activity cycle; and periodically transmitting a second type of synchronization signal during each subsequent on-period of the set of on-periods, wherein the second type of synchronization signal indicates a time duration until a next transmission of the first type of synchronization signal.

8. The reader of claim 7, wherein the second type of synchronization signal further indicates a duty rate of on-time for an loT device to meet the determined target activity cycle.

9. The reader of claim 7, wherein the alignment process further includes the processor and the transceiver configured to: receive, in response to the transmitted first type or the second type of synchronization signal, feedback of data or control information from at least one loT device.

10. The reader of claim 7, wherein the first type of synchronization signal comprises a sync-start signal and wherein the second type of synchronization signal comprises a sync-align signal.

11. The reader of claim 7, wherein the target activity cycle is determined from configuration information received from one of a base station or an loT controlling entity, wherein the configuration information indicates a duration of the target activity cycle and one or more of, a duration and periodicity of each on-period of the set of on-periods or a time offset of each on-period of the set of on-periods.

12. The reader of claim 7, where the one or more loT devices are ambient loT (AloT) devices.

13. A method for an ambient Internet-of-Things (AloT) device, the method comprising: determining a maximum duty rate of on-periods for one or both of receiving or transmitting over a time interval, determining an activity cycle of a plurality of on-periods and off periods during the time interval compatible with the determined maximum duty rate and randomly selecting a start time of an on-period; receiving, from an AloT device reader during one of the plurality of on-periods, a synchronization alignment transmission indicating a range of maximum duty rates required for a target activity cycle of the AloT device reader and indicating a duration of a time period until a synchronization start transmission will be sent by the AloT device reader; comparing the determined maximum duty rate with the indicated range of duty rates to determine the AloT device may participate in the target activity cycle of the AloT device reader; and modifying the activity cycle such that the start time of the on-period overlap with the indicated timing of the synchronization start transmission.

14. The method of claim 13, further comprising: sending, to the AloT device reader in response to the synchronization alignment transmission, feedback comprising data or control information.

15. The method of claim 13, wherein the maximum duty rate is determined based on available power from energy harvesting.

16. The method of claim 13, wherein the maximum duty rate is a maximum fraction of time the AloT device can be in on during the time interval.

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