Disorganized communications at the rear

Abstract

A system, method, and device for backscatter-based wireless transmission. A backscatter instruction message (BID) is received from an access point (AP). An interrogation signal is received. Uplink data is transmitted to the AP based on the BID and the interrogation signal. In some implementations, the interrogation signal is received from the AP. In some implementations, the BID indicates a backscatter duration, and the uplink data is transmitted to the AP during the backscatter duration. In some implementations, the uplink data is transmitted to the AP simultaneously with receiving the interrogation signal. In some implementations, energy is harvested from the interrogation signal. In some implementations, the uplink data is transmitted to the AP following the interrogation signal based on the energy harvested from the interrogation signal. In some implementations, the interrogation signal includes a compensation signal based on channel conditions and / or based on backscatter from the WTRU.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 147,079, filed on February 8, 2021, and U.S. Provisional Patent Application No. 63 / 235,469, filed on August 20, 2021, the contents of which are incorporated herein by reference.

Background Art

[0002] The power - saving function is implemented in IEEE and 3GPP standards for end - user devices to save power in the device. The backscatter transmitter mimics on - off keying by reflecting or absorbing the incident waveform.

Summary of the Invention

[0003] Some implementations provide a system, method, and / or device for wireless transmission based on backscatter. A backscatter indication message (BID) is received from an access point (AP). An interrogation signal is received. Uplink data is transmitted to the AP based on the BID and the interrogation signal. In some implementations, the interrogation signal is received from the AP. In some implementations, the BID indicates a backscatter duration, and the uplink data is transmitted to the AP during the backscatter duration. In some implementations, the uplink data is transmitted to the AP simultaneously with receiving the interrogation signal. In some implementations, energy is harvested from the interrogation signal. In some implementations, the uplink data is transmitted to the AP following the interrogation signal based on the energy harvested from the interrogation signal. In some implementations, the interrogation signal includes a compensation signal based on the channel state and / or based on backscatter from a WTRU.

Brief Description of the Drawings

[0004] A more detailed understanding can be obtained from the following description, which is given as an example in conjunction with the attached drawings, where similar reference numbers in the drawings indicate similar elements. [Figure 1A] This is a system diagram showing an exemplary communication system in which one or more disclosed embodiments may be implemented. [Figure 1B] This is a system diagram showing an exemplary wireless transmit / receive unit (WTRU) that may be used in the communication system shown in Figure 1A, according to one embodiment. [Figure 1C] This is a system diagram showing an exemplary radio access network (RAN) and an exemplary core network (CN) that may be used in the communication system shown in Figure 1A according to one embodiment. [Figure 1D] This is a system diagram showing further exemplary RAN and further exemplary CN that may be used in the communication system shown in Figure 1A according to one embodiment. [Figure 2] This figure shows an example of backscattering in the 802.11ah framework. [Figure 3] This is a table illustrating an example BID message format. [Figure 4] This is a block containing example messages and related formats. [Figure 5] This figure shows an example of backscattering in an 802.11 system. [Figure 6A] Exemplary energy harvesting and backscattering are shown. [Figure 6B] The continuation of Figure 6A is shown. [Figure 7] This demonstrates an example of communication that enables backscatter communication in an 802.11ax system. [Figure 8] This flowchart illustrates the operation of the BSTA when the DL received signal exceeds or falls below a first threshold based on QoS requirements. [Figure 9] This is a system diagram illustrating an example of interference in backscatter transmission. [Figure 10] This document presents an exemplary framework for learning DL channel states via inverse estimation. [Figure 11] This shows the sender's compensation for channel failure. [Figure 12] This shows an exemplary control loop in AP for channel estimation. [Figure 13] An exemplary control loop for multi-carrier, multi-STA estimation is shown. [Figure 14] This shows an exemplary buffer estimation of BSTA using AP. [Modes for carrying out the invention]

[0005] Several implementations provide methods for implementation in a wireless station (STA). The STA receives a backscatter instruction (BID) message indicating the backscatter opportunity and the downlink (DL) signal strength threshold. Based on the signal strength of the DL transmission received on the resource unit (RU) indicated in the BID message exceeding the DL signal strength threshold, the STA backscatters the DL transmission to generate a backscatter transmission.

[0006] In some implementations, backscattering of a DL transmission occurs based on the DL signal duration exceeding the payload transmission requirements associated with the backscatter transmission. Some implementations include backscattering an uplink (UL) transmission from another STA received on the resource unit indicated in the BID message to generate another backscatter transmission, based on the DL transmission intensity not exceeding the DL signal intensity threshold. In some implementations, backscattering of a UL transmission occurs based on the UL transmission intensity exceeding the UL signal intensity threshold and the UL transmission duration exceeding the payload transmission requirements associated with the other backscatter transmission. Some implementations include measuring the signal intensity of a DL transmission based on the BID message, the preamble in the DL frame, or a dedicated reference signal. In some implementations, the DL signal intensity threshold and the UL signal intensity threshold are the same threshold. In some implementations, the BID message includes a management message. In some implementations, the BID message includes an acknowledgment message. In some implementations, the DL signal intensity threshold is associated with quality of service (QoS). In some implementations, backscatter transmission is generated based on the fact that the DL transmission signal strength exceeds the DL signal strength threshold and the DL transmission exceeds the payload transmission requirements.

[0007] Several implementations provide an STA. An STA includes a receiver configured to receive a BID message indicating the backscatter opportunity and the DL signal strength threshold. The STA also includes a transmitter configured to backscatter DL transmissions to generate a backscatter transmission based on whether the signal strength of the DL transmission received on the RU indicated in the BID message exceeds the DL signal strength threshold.

[0008] In some implementations, the transmitter is also configured to backscatter DL transmissions based on the duration of the DL signal exceeding the payload transmission requirements associated with the backscatter transmission. In some implementations, the transmitter is also configured to backscatter UL transmissions from another STA received on the resource unit indicated in the BID message to generate another backscatter transmission, based on the intensity of the DL transmission not exceeding the DL signal intensity threshold. In some implementations, the transmitter is also configured to backscatter UL transmissions based on the signal intensity of the UL transmission exceeding the UL signal intensity threshold and the duration of the UL transmission exceeding the payload transmission requirements associated with the other backscatter transmission. In some implementations, the receiver is also configured to measure the signal intensity of DL transmissions based on the BID message, the preamble in the DL frame, or a dedicated reference signal. In some implementations, the DL signal intensity threshold and the UL signal intensity threshold are the same threshold. In some implementations, the BID message includes a management message. In some implementations, the BID message includes an acknowledgment message. In some implementations, the DL signal intensity threshold is associated with QoS. In some implementations, the transmitter is also configured to generate backscattered transmissions based on the fact that the DL transmission signal strength exceeds the DL signal strength threshold and the DL transmission exceeds the payload transmission requirements.

[0009] Figure 1A shows an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, message transmission, and broadcast to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communication system 100 may use one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filter OFDM, and filter bank multicarrier (FBMC).

[0010] As shown in Figure 1A, the communication system 100 may include radio transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the internet 110, and other networks 112, but it will be understood that the disclosed embodiments intend any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, and 102d may be any type of device configured to operate and / or communicate in a radio environment. For example, WTRU102a, 102b, 102c, and 102d, all of which may be referred to as stations (STA), may be configured to transmit and / or receive radio signals and may include user equipment (UE), mobile stations, fixed or mobile subscriber units, subscriber-based units, pagers, mobile phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearables, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated processing chain context), consumer electronic devices, and devices operating on commercial and / or industrial wireless networks. Any of WTRU102a, 102b, 102c, and 102d may interchangeably be referred to as UE.

[0011] The communication system 100 may also include base stations 114a and / or base stations 114b. Each of the base stations 114a and 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, and 102d to facilitate access to one or more communication networks such as CN 106, the Internet 110, and / or other networks 112. As an example, base stations 114a and 114b may be next-generation node B such as base transceiver station (BTS), node B, eNode B (eNB), home node B, home eNode B, gNode B (gNB), new radio (NR) node B, site controller, access point (AP), wireless router, etc. Although base stations 114a and 114b are shown as single elements, it will be understood that base stations 114a and 114b may include any number of interconnected base stations and / or network elements.

[0012] Base station 114a may be part of RAN 104, which may also include other base stations such as a base station controller (BSC), a radio network controller (RNC), relay nodes, and / or network elements (not shown). Base station 114a and / or base station 114b may be configured to transmit and / or receive radio signals on one or more carrier frequencies which may be referred to as cells (not shown). These frequencies may be licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. Cells may provide coverage of radio services to a particular geographic area which may be relatively fixed or change over time. Cells may be further divided into cell sectors. For example, a cell associated with base station 114a may be divided into three sectors. Thus, in one embodiment, base station 114a may include three transceivers, i.e., one transceiver per sector of the cell. In one embodiment, the base station 114a may use multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

[0013] Base stations 114a and 114b may communicate with one or more WTRUs 102a, 102b, 102c, and 102d via an air interface 116, which may be any suitable radio 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).

[0014] More specifically, as described above, the communication system 100 can be a multiple access system and can use one or more channel access schemes such as, for example, CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base stations 114a of the RAN 104 and the WTRUs 102a, 102b, 102c can implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA) that can establish an air interface 116 using wideband CDMA (WCDMA). WCDMA can include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA can include High-Speed Downlink Packet Access (HSDPA) and / or High-Speed Uplink Packet Access (HSUPA).

[0015] In one embodiment, the base stations 114a and the WTRUs 102a, 102b, 102c can implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which can establish an air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0016] In one embodiment, the base stations 114a and the WTRUs 102a, 102b, 102c can implement a radio technology such as NR radio access, which can establish an air interface 116 using NR.

[0017] In one embodiment, base station 114a and WTRU 102a, 102b, 102c may implement multiple radio access technologies. For example, base station 114a and WTRU 102a, 102b, 102c may implement LTE radio access and NR radio access together, for example, using the dual connectivity (DC) principle. Thus, the air interface utilized by WTRU 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions transmitted to and from multiple types of base stations (e.g., eNB and gNB).

[0018] In other embodiments, base stations 114a and WTRUs 102a, 102b, and 102c may implement wireless 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, Provisional Standard 2000 (IS-2000), Provisional Standard 95 (IS-95), Provisional Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), and GSM EDGE (GERAN).

[0019] The base station 114b in Figure 1A may be, for example, a wireless router, home node B, home e-node B, or access point, and may utilize any suitable RAT to facilitate wireless connectivity in local areas such as offices, homes, vehicles, campuses, industrial facilities, aerial corridors (for use by drones), roads, etc. In one embodiment, the base station 114b and WTRU 102c, 102d may implement wireless technologies such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and WTRU 102c, 102d may implement wireless technologies such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, base stations 114b and WTRUs 102c, 102d may establish picocells or femtocells using cellular-based RATs (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.). As shown in Figure 1A, base station 114b may have a direct connection to the internet 110. Therefore, base station 114b may not need to access the internet 110 via CN 106.

[0020] RAN104 may communicate with CN106, 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 WTRU102a, 102b, 102c, and 102d. The data may have various quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, and mobility requirements. CN106 may provide call control, billing services, mobile location-based services, prepaid calls, internet connectivity, video distribution, etc., and / or implement high-level security functions such as user authentication. Although not shown in Figure 1A, it will be understood that RAN104 and / or CN106 may communicate directly or indirectly with other RANs using the same RAT or different RAT as RAN104. For example, in addition to being connected to RAN104 which may utilize NR radio technology, CN106 may also communicate with another RAN (not shown) using GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0021] CN106 may also function as a gateway for WTRU102a, 102b, 102c, and 102d to access PSTN108, the Internet 110, and / or other networks 112. PSTN108 may include a public switched telephone network providing plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices, where these networks and devices use common communication protocols such as the transmission control protocol (TCP), the user datagram protocol (UDP), and / or the Internet protocol (IP) of the TCP / IP Internet Protocol suite. Network 112 may include wired and / or wireless networks owned and / or operated by other service providers. For example, network 112 may include another CN connected to one or more RANs that may use the same RAT as RAN104 or a different RAT.

[0022] Some or all of the WTRUs 102a, 102b, 102c, and 102d in the communication system 100 may include multimode capability (for example, WTRUs 102a, 102b, 102c, and 102d may include multiple transceivers for communicating with different radio networks via different radio links). For example, WTRU 102c shown in Figure 1A may be configured to communicate with base station 114a, which may use cellular-based radio technology, and base station 114b, which may use IEEE 802 radio technology.

[0023] Figure 1B is a system diagram showing an exemplary WTRU102. As shown in Figure 1B, the WTRU102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power supply 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be understood that the WTRU102 may include any partial combination of the aforementioned elements while maintaining consistency with one embodiment.

[0024] The processor 118 may be a general-purpose processor, a dedicated processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to a transceiver 120 which may be coupled to a transmit / receive element 122. Figure 1B shows the processor 118 and transceiver 120 as separate components, but it will be understood that the processor 118 and transceiver 120 may be integrated together in an electronic package or chip.

[0025] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) via 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 one embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF signals and optical signals. It will be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of radio signals.

[0026] Although the transmit / receive element 122 is shown as a single element in Figure 1B, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may utilize MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving radio signals via the air interface 116.

[0027] The transceiver 120 may be configured to modulate the signal transmitted by the transmit / receive element 122 and demodulate the signal received by the transmit / receive element 122. As described above, the WTRU 102 may have multimode capability. Therefore, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0028] The processor 118 of the WTRU102 may be coupled to a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light-emitting diode (OLED) display unit) and may receive user input from these. 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 any type of suitable memory, such as non-removable memory 130 and / or removable memory 132, and store data in such memory. 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 memory not physically located on the WTRU 102, such as on a server or home computer (not shown), and store data in such memory.

[0029] The processor 118 may receive power from the power supply 134, but may also be configured to distribute and / or control power to other components in the WTRU 102. The power supply 134 may be any suitable device for supplying power to the WTRU 102. For example, the power supply 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.), a solar cell, a fuel cell, etc.

[0030] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) about the current location of the WTRU 102. In addition to or instead of the information from the GPS chipset 136, the WTRU 102 may receive location information from base stations (e.g., base stations 114a, 114b) via the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be understood that the WTRU 102 may acquire location information by any preferred location determination method while maintaining consistency with one embodiment.

[0031] The processor 118 may be further coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functions, and / or wired or wireless connectivity. For example, peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or videos), 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. Peripherals 138 may include one or more sensors. The sensor may be one or more of the following: gyroscope, accelerometer, Hall effect sensor, magnetometer, orientation sensor, proximity sensor, temperature sensor, time sensor, geolocation sensor, altimeter, light sensor, touch sensor, barometer, gesture sensor, biometric sensor, humidity sensor, etc.

[0032] WTRU102 may include a full-duplex radio in which the transmission and reception of some or all of a signal (for example, associated with specific subframes of both UL (for example, for transmission) and DL (for example, for reception) may be simultaneous and / or together. The full-duplex radio may include an interference management unit for reducing and / or substantially eliminating self-interference either through hardware (e.g., chokes) or signal processing via a processor (e.g., via a separate processor (not shown) or processor 118). In one embodiment, WTRU102 may include a half-duplex radio for the transmission and reception of some or all of a signal (for example, associated with specific subframes of either UL (for example, for transmission) or DL ​​(for example, for reception)).

[0033] Figure 1C is a system diagram illustrating RAN104 and CN106 according to one embodiment. As described above, RAN104 can communicate with WTRU102a, 102b, and 102c via the air interface 116 using E-UTRA wireless technology. RAN104 can also communicate with CN106.

[0034] RAN104 may include e-nodes-B160a, 160b, and 160c, but it will be understood that RAN104 may include any number of e-nodes-B while maintaining consistency with one embodiment. Each of e-nodes-B160a, 160b, and 160c may include one or more transceivers for communicating with WTRU102a, 102b, and 102c via the air interface 116. In one embodiment, e-nodes-B160a, 160b, and 160c may implement MIMO technology. Thus, e-node-B160a may, for example, use multiple antennas to transmit radio signals to and / or receive radio signals from WTRU102a.

[0035] Each of the e-nodes-B160a, 160b, and 160c may be associated with a specific cell (not shown) and may be configured to handle wireless resource management decisions, handover decisions, user scheduling, etc., in UL and / or DL. As shown in Figure 1C, the e-nodes-B160a, 160b, and 160c may communicate with each other via the X2 interface.

[0036] The CN106 shown in Figure 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. Although these elements are shown as part of CN106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0037] The MME162 can be connected to each of the e-nodes B162a, 162b, and 162c in RAN104 via the S1 interface and can function as a control node. For example, the MME162 may perform roles such as authenticating users of WTRU102a, 102b, and 102c, activating / deactivating bearers, and selecting gateways for specific services during the initial attachment of WTRU102a, 102b, and 102c. The MME162 may provide control plane functionality for switching between RAN104 and other RANs (not shown) employing other radio technologies such as GSM and / or WCDMA.

[0038] The SGW164 can be connected to each of the e-nodes B160a, 160b, and 160c in RAN104 via the S1 interface. The SGW164 can generally route and forward user data packets to and from WTRU102a, 102b, and 102c. The SGW164 can perform other functions, such as anchoring the user plane during e-node B handovers, triggering paging when DL data is available to WTRU102a, 102b, and 102c, and managing and remembering the context of WTRU102a, 102b, and 102c.

[0039] SGW164 may be connected to PGW166, which may provide WTRU102a, 102b, and 102c with access to a packet-switched network such as the Internet 110 to facilitate communication between WTRU102a, 102b, and 102c and IP-enabled devices.

[0040] CN106 can facilitate communication with other networks. For example, CN106 can provide WTRU102a, 102b, and 102c with access to a circuit-switched network such as PSTN108 to facilitate communication between WTRU102a, 102b, and 102c and conventional terrestrial line communication devices. For example, CN106 may include, or communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that functions as an interface between CN106 and PSTN108. In addition, CN106 may provide WTRU102a, 102b, and 102c with access to another network 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0041] Although the WTRU is shown as a wireless terminal in Figures 1A to 1D, in certain representative embodiments, such a terminal is intended to be able to use a wired communication interface (e.g., temporary or permanent) with a communication network.

[0042] In a typical embodiment, the other network 112 may be a WLAN.

[0043] A WLAN in Basic Service Set (BSS) mode may have an Access Point (AP) of the BSS and one or more stations (STAs) associated with the AP. An AP may have access to or an interface with a Distribution System (DS) or another type of wired / wireless network that carries traffic within and / or outside the BSS. Traffic originating outside the BSS and destined for an STA may reach and be delivered to the STA via an AP. Traffic originating from an STA to a destination outside the BSS may be transmitted to an AP and delivered to its respective destination. Traffic between STAs within the BSS may be transmitted, for example, via an AP; a source STA may transmit traffic to an AP, and the AP may deliver the traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic may be transmitted between a source STA and a destination STA (for example, directly between them) in a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS). A WLAN using Independent BSS (IBSS) mode may not have APs, and STAs within or using IBSS (e.g., all STAs) may communicate directly with each other. The IBSS mode of communication may be referred to herein as “ad hoc” communication mode.

[0044] When using the 802.11ac infrastructure operating mode or a similar operating mode, an AP may transmit beacons on a fixed channel, such as the primary channel. The primary channel may have a fixed width (e.g., a 20 MHz bandwidth) or a dynamically set width. The primary channel may be the operating channel of the BSS and may be used by the STA to establish a connection with the AP. In certain typical embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. In the case of CSMA / CA, the STA, including the AP (e.g., all STAs), may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, that STA may be backed off. A single STA (e.g., only one station) may transmit at any given time in a given BSS.

[0045] High-throughput (HT) STAs may use a 40 MHz wide channel for communication, which may be formed, for example, through a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels.

[0046] Very High Throughput (VHT) STAs can support channels with widths of 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz. The 40 MHz and / or 80 MHz channels mentioned above can be formed by combining multiple consecutive 20 MHz channels. A 160 MHz channel can be formed by combining eight consecutive 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. In the 80+80 configuration, after channel coding, the data can pass through a segment parser that can split the data into two streams. Inverse Fast Fourier Transform (IFFT) and time-domain processing can be performed separately for each stream. The streams may be mapped to two 80 MHz channels, and the data can be transmitted by a transmitting STA. At the receiver of a receiving STA, the operation described above for the 80+80 configuration may be reversed, and the combined data may be transmitted to Medium Access Control (MAC).

[0047] Sub-1 GHz operating modes are supported by 802.11af and 802.11ah. Channel operating bandwidth and carrier are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports bandwidths of 5 MHz, 10 MHz, and 20 MHz in the TV White Space (TVWS) spectrum, while 802.11ah supports bandwidths of 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz using the non-TVWS spectrum. According to a typical embodiment, 802.11ah may support meter-type control / machine-type communications (MTC), such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, including support for specific and / or limited bandwidths (e.g., support only for that). MTC devices may include batteries with battery life exceeding a threshold (e.g., to maintain very long battery life).

[0048] A WLAN system capable of supporting multiple channels and channel bandwidths such as 802.11n, 802.11ac, 802.11af, and 802.11ah includes a channel that can be designated as the primary channel. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by an STA from among all STAs operating in a BSS that support the minimum bandwidth operating mode. In the 802.11ah example, the primary channel may be 1 MHz wide for an STA (e.g., an MTC type device) that supports (e.g., only) the 1 MHz mode, even if other STAs in the AP and 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 state of the primary channel. For example, if the primary channel is busy, an STA (which only supports 1MHz operating mode) sending to the AP may consider the entire available frequency band to be busy, even if most of the available frequency band is idle.

[0049] In the United States, the available frequency band that can be used by 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0050] Figure 1D is a system diagram showing RAN104 and CN106 according to one embodiment. As described above, RAN104 can communicate with WTRU102a, 102b, and 102c via the air interface 116 using NR radio technology. RAN104 can also communicate with CN106.

[0051] RAN104 may include gNB180a, 180b, and 180c, but it will be understood that RAN104 may include any number of gNBs while maintaining consistency with one embodiment. Each of gNB180a, 180b, and 180c may include one or more transceivers for communicating with WTRU102a, 102b, and 102c via the air interface 116. In one embodiment, gNB180a, 180b, and 180c may implement MIMO technology. For example, gNB180a and 180b may use beamforming to transmit and / or receive signals to gNB180a, 180b, and 180c. Thus, gNB180a may, for example, use multiple antennas to transmit and / or receive radio signals from WTRU102a. In one embodiment, gNB180a, 180b, and 180c may implement carrier aggregation technology. For example, gNB180a may transmit multiple component carriers to WTRU102a (not shown). A subset of these component carriers may be on the unauthorized spectrum, and the remaining component carriers may be on the authorized spectrum. In one embodiment, gNB180a, 180b, and 180c may implement coordinated multi-point (CoMP) technology. For example, WTRU102a may receive coordinated transmissions from gNB180a and gNB180b (and / or gNB180c).

[0052] WTRU102a, 102b, and 102c may communicate with gNB180a, 180b, and 180c using transmissions associated with an expandable numerology. For example, OFDM symbol intervals and / or OFDM subcarrier intervals may vary for different transmissions, different cells, and / or different portions of the radio transmission spectrum. WTRU102a, 102b, and 102c may communicate with gNB180a, 180b, and 180c using subframes or transmission time intervals (TTIs) of varying or expandable lengths (e.g., varying numbers of OFDM symbols and / or varying durations of absolute time).

[0053] gNB180a, 180b, and 180c can be configured to communicate with WTRU102a, 102b, and 102c in standalone and / or non-standalone configurations. In a standalone configuration, WTRU102a, 102b, and 102c can communicate with gNB180a, 180b, and 180c without accessing other RANs (e.g., e-node-B160a, 160b, and 160c). In a standalone configuration, WTRU102a, 102b, and 102c can utilize one or more of gNB180a, 180b, and 180c as mobility anchor points. In a standalone configuration, WTRU102a, 102b, and 102c can communicate with gNB180a, 180b, and 180c using signals in unlicensed bands. In a non-standalone configuration, WTRU102a, 102b, and 102c can communicate with and connect to gNB180a, 180b, and 180c, while also communicating with and connecting to other RANs such as e-nodes-B160a, 160b, and 160c. For example, WTRU102a, 102b, and 102c can implement DC principles for substantially simultaneous communication with one or more gNB180a, 180b, and 180c and one or more e-nodes-B160a, 160b, and 160c. In a non-standalone configuration, e-nodes B160a, 160b, and 160c can function as mobility anchors for WTRU102a, 102b, and 102c, while gNB180a, 180b, and 180c can provide additional coverage and / or throughput to service WTRU102a, 102b, and 102c.

[0054] Each of the gNB180a, 180b, and 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, support for network slices, interaction between DC, NR and E-UTRA, routing of user plane data to User Plane Functions (UPFs) 184a and 184b, routing of control plane information to Access and Mobility Management Functions (AMFs) 182a and 182b, and so on. As shown in Figure 1D, the gNB180a, 180b, and 180c may communicate with each other via the Xn interface.

[0055] The CN106 shown in Figure 1D may include at least one AMF182a, 182b, at least one UPF184a, 184b, at least one Session Management Function (SMF)183a, 183b, and possibly a Data Network (DN)185a, 185b. Although the aforementioned elements are shown as part of CN106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0056] AMF182a and 182b can be connected to one or more of gNB180a, 180b, and 180c in RAN104 via the N2 interface and can function as control nodes. For example, AMF182a and 182b may play roles such as user authentication for WTRU102a, 102b, and 102c, support for network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selection of SMF183a and 183b for registration, management of registration areas, termination of non-access stratum (NAS) signaling, and mobility management. Network slicing can be used by AMF182a and 182b to customize CN support for WTRU102a, 102b, and 102c based on the type of service utilizing WTRU102a, 102b, and 102c. For example, different network slices may be established for different use cases, such as services that rely on ultra-reliable low latency (URLLC) access, services that rely on enhanced massive mobile broadband (eMBB) access, and services for MTC access. AMF182a, 182b may provide control plane functionality for switching between RAN104 and other RANs (not shown) using other radio technologies such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0057] SMF183a and 183b may be connected to AMF182a and 182b in CN106 via the N11 interface. SMF183a and 183b may also be connected to UPF184a and 184b in CN106 via the N4 interface. SMF183a and 183b may select and control UPF184a and 184b and configure the routing of traffic through UPF184a and 184b. SMF183a and 183b may perform other functions such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, and providing DL data notifications. PDU session types may be IP-based, non-IP-based, Ethernet-based, etc.

[0058] UPF184a and 184b may be connected via the N3 interface to one or more gNB180a, 180b, and 180c within RAN104, thereby providing WTRU102a, 102b, and 102c with access to a packet-switched network such as the Internet 110 to facilitate communication between WTRU102a, 102b, and 102c and IP-enabled devices. UPF184 and 184b may perform other functions such as packet routing and forwarding, enforcement of user plane policies, support for multi-homed PDU sessions, processing of user plane QoS, buffering of DL packets, and mobility anchoring.

[0059] CN106 can facilitate communication with other networks. For example, CN106 may include, or communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that functions as an interface between CN106 and PSTN108. In addition, CN106 may provide WTRU102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, WTRU102a, 102b, 102c may be connected to local DN185a, 185b via UPF184a, 184b through N3 interfaces to UPF184a, 184b and N6 interfaces between UPF184a, 184b and DN185a, 185b.

[0060] In view of Figures 1A to 1D and their corresponding descriptions, one or more of the functions described herein with respect to one or more of the WTRU102a to d, base stations 114a to b, e-node-B 160a to c, MME162, SGW164, PGW166, gNB180a to c, AMF182a to b, UPF184a to b, SMF183a to b, DN185a to b, and / or any other devices described herein may be implemented by one or more emulation devices (not shown). An emulation device may be one or more devices configured to emulate one or more of the functions described herein. For example, an emulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0061] Emulation devices may be designed to implement testing of one or more other devices in a laboratory and / or operator network environment. For example, one or more emulation devices may perform one or more or all functions while fully or partially implemented and / or deployed as part of a wired and / or wireless network to test other devices in a communications network. One or more emulation devices may perform one or more or all functions while temporarily implemented / deployed as part of a wired and / or wireless network. Emulation devices may be directly coupled to another device for the purpose of testing and / or performing testing using over-the-air wireless communication.

[0062] One or more emulation devices may perform one or more functions, including all of the above, while not implemented / deployed as part of a wired and / or wireless communication network. For example, an emulation device may be used in a test laboratory test scenario, and / or in a wired and / or wireless communication network that is not deployed (e.g., for testing), to implement testing of one or more components. One or more emulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation device to transmit and / or receive data. In this specification, the following acronyms are used in particular: Access Point (AP), Backscatter Instruction (BID), Backscatter STA (BSTA), Clear To Send (CTS), Downlink (DL), Internet of Things (IoT), Interrogation Signal (INT_SIG), Internet Protocol (IP), Media Access Control (MAC), Multiple Input Multiple Output (MIMO), Orthogonal Frequency Division Multiplexing (OFDM), Physical Layer (PHY), Paging Opportunity (PO), Power-Optimized Waveform (POW), Power Save Mode (PSM), Restricted Access Window (RAW), Request To Send (RTS), Target Wakeup Time (TWT), Wake-Up Receiver (WuR), Wake-Up Packet (WuP), Radio Access Technology (RAT), Radio Frontend (Radio) Front-end (RF), Transmission Request (RTS), Station (WiFi device) (STA), Transmit / Receive (TX / RX), Transmission Information Map (TIM), User Equipment (UE), Uplink (UL), and Zero-energy (ZE).

[0063] Both IEEE and 3GPP include power-saving features for end-user devices (e.g., 802.11 STA, 3GPP UE) that obtain services from access devices (e.g., 802.11 access points (APs) or 3GPP eNBs). Note that while STAs and UEs are used herein as exemplary end-user devices, any suitable end-user device may be used instead of these examples. Similarly, while APs and eNBs are used herein as exemplary access devices, any suitable access device may be used instead of these examples. Devices that implement power-saving features can be said to be operating in power-saving mode (PSM). A typical PSM procedure involves the end-user device negotiating a sleep cycle with the access device, going to sleep after each sleep cycle (e.g., entering PSM), waking up after each pre-negotiated condition (e.g., periodicity or event occurrence), displaying buffered data for reception or transmission after entering the "wake period," performing data transmission or reception during the "wake period," and resuming PSM (e.g., when there is a lull in data transmission or reception). In some cases, a periodic, finite, but relatively long duration can be considered a "wake cycle," and a portion of that cycle can be considered the end-user device's "wake period."

[0064] When a device is woken, the duration of the wake cycle, which is the period during which the device is active, may depend on the amount of pending data in the queue for receiving or transmitting. In some cases, after an end-user device wakes up, it may remain active for the entire duration of the wake cycle. If there is no indication that data is pending for receiving and / or transmitting during the "wake period," the end-user device may resume sleep at the end of the wake period (e.g., resume PSM). Entering PSM is typically for energy-saving purposes. In some cases, the longer a device can sleep, the longer the end-user device will be powered down.

[0065] Newer versions of the 802.11 specification incorporate Target Wake-Up Time (TWT). TWT implementations may include features that allow an AP to define a specific time or set of times for individual stations to access the medium. STAs and APs may exchange information indicating expected activity durations to allow the AP to control the amount of contention and overlap between competing STAs. The use of TWTs may be negotiated between the AP and STAs. In some implementations, TWTs are involved in Restricted Access Window (RAW). RAWs facilitate grouping stations within a Basic Service Set (BSS) by restricting channel access to only stations belonging to a given group during a specific time period (called the RAW). In other words, only a specific STA or group of STAs (or other devices) is allowed to access the channel during the RAW. In some cases, this has the advantage of reducing contention and / or avoiding simultaneous transmissions from many stations.

[0066] In some implementations, STAs grouped within a RAW compete for access slots to gain access to the medium. An access slot is a period of time within the RAW that is restricted to a specific STA and can be selected for channel access by a specific STA or group of STAs. In some implementations, the amount of competition for access slots is, on average, proportional to the number of STAs grouped within the RAW and the call model requirements per STA. The term call model refers to a process that can be applied to an STA that determines session arrival (the time when data arrives), association duration, and per-session data requirements. In some cases, TWTs may be used to reduce network energy consumption, for example, by facilitating an STA sleep state until those TWTs arrive.

[0067] The above features can typically be implemented to provide power savings for STAs. Such STAs can be incorporated into any suitable device, such as Internet of Things (IoT) devices. Exemplary IoT devices include chemical sensors (e.g., oil leak sensors, haze detectors, etc.), environmental monitors (e.g., temperature and / or pressure sensors, embedded seismic monitors, etc.), and event reporting meters (e.g., parking meter expiration, electricity usage reporting, etc.). Such devices may have relatively low data rate requirements (e.g., compared to a typical 802.11 STA) and may transmit bursty data traffic (e.g., once every few hours / days, or even once every few weeks, e.g., several hundred bits / second to several kilobits / second).

[0068] Such devices may remain in PSM mode most of the time, wake up to perform tasks (e.g., periodic monitoring), and engage in wireless data communication to report information (e.g., measurements or other data) to a server at specified times. Such IoT sensors may be deployed in inaccessible locations (e.g., wall-mounted seismic monitors used in California and Japan to estimate earthquake damage) where periodically switching the power supply within those devices would be impractical. Therefore, devices that can harvest energy from various power sources and use their power reserves for transmitting and receiving functions may have the advantage of extending availability. Devices capable of harvesting energy to power RX and TX chains may become more common in the future. Architectures with transmitting chains that do not consume large amounts of power may also become ubiquitous in the future. In some implementations, backscatter transmitters support such architectures.

[0069] Backscattering is a technique by which an STA, WTRU, or other radio communication device uses an incident RF signal / waveform to (a) harvest the energy needed to power its uplink transmission and / or (b) modulate the reflected / backscattered RF signal / waveform through a set of antenna loads. In some implementations, the term backscattering does not necessarily involve energy harvesting, although some implementations may define energy harvesting as part of backscattering. Backscattering typically involves reflecting or absorbing the incident waveform to mimic on-off keying. Note that different implementations include variations of the backscattering concept. For example, an incident waveform, which may be called a query signal, carrier wave generator, etc., may be provided specifically for backscattering (i.e., dedicated to backscattering) or not specifically for backscattering (i.e., for opportunistic backscattering). A dedicated query signal may be provided by any suitable source such as an STA, UE, AP, node B, WTRU, etc. Such a source may be called a dedicated source. Opportunistic query signals may include any suitable signal that is not specifically provided for backscattering by any suitable source, such as ambient sources (e.g., Wi-Fi, TV signals, etc.), and signals from other devices that are not specifically provided for backscattering (e.g., STA, UE, AP, Node B, WTRU, etc.). Such sources may be called opportunistic sources.

[0070] With increasing attention to sustainability, there is great interest in the areas of power saving and energy efficiency. For example, a widespread ambient source is Wi-Fi. In some implementations, it is preferable to use backscattering with a source that can be integrated into an existing framework, for example, to enable widespread adoption. In other words, in some implementations, it is beneficial for non-backscattering legacy devices and backscattering devices to coexist in the environment without disrupting the legacy devices and / or requiring updates to the legacy device software or hardware.

[0071] Some implementations include existing, new, or reused messages or other signals. Some exemplary messages are defined herein using specific names, but note that these specific names are illustrative only. Some implementations include preferred signals with different names that provide the same, similar, or overlapping functionality.

[0072] In some implementations, a backscatter station (BSTA) is a device that can transmit information by backscattering a signal. In some implementations, a BSTA may include an ultra-low power or zero-energy device. In some implementations, a Clear To Send Type A (CTSA) message may be used as a response from the receiver to the initiator, indicating successful reception of the RTSB and acceptance of a communication commencement request, as indicated by the RTSB (Ready to Send / Request to Send signal). In some implementations, the CTSA defers the BSTA indefinitely from transmission responsibility. In some implementations, the CTSA is addressed to a single initiator, and the same message assigns the initiator abbreviated identification information, which may be called a mnemonic. In some implementations, if the BSTA has not received the CTSA, the BSTA may be compelled not to transmit the RTSB later.

[0073] In some implementations, a Request to Send Type B (RTSB) message is sent by a BSTA requesting an opportunity for backscattering. In some implementations, the RTSB message includes a duration field or other indication specifying the requested duration for backscattering, and / or a flag, which may be called a backscatter indicator flag, indicating that only backscattering is possible. In some implementations, the receiver responds with a CTSA to the message initiator (i.e., the BSTA sending the RTSB) that accepts the request.

[0074] In some implementations, a Transmittable Type B (CTSB) message may be sent in response to an RTSB. In some implementations, the receiver responds with a CTSB message to force all BSTAs to backoff from requesting the initiation of backscatter transmission (i.e., refrain from sending / transmitting a Request to Transmit (RTSB) for a certain period of time). In some implementations, the CTSB message is transmitted to a broadcast address. In some implementations, the CTSB may be part of a backoff mechanism based on an existing backoff mechanism (e.g., the backoff method in the Distributed Coordination Function, DCF, already used in the 802.11 framework).

[0075] In some implementations, a Backscatter Instruction Message (BID) message is sent by the AP to one or more identified BSTAs. In some implementations, the BID is addressed to the BSTA based on abbreviated identification information (e.g., a mnemonic). In some implementations, the BID message is sent to a BSTA that has previously transmitted an RTSB to the AP and has deferred a CTSA. In some implementations, the BID message is sent to a BSTA that is expected to wake up at a certain time (e.g., a priori) due to, for example, a TWT configuration. In some implementations, the BID message indicates the backscatter duration, which may or may not be equal to the duration requested in the RTSB.

[0076] In some implementations, the AP sends a Buffer Status Report Request (BSR REQ) to the BSTA to instruct the BSTA to transmit the BSR to the AP. In some implementations, a particular BSTA is addressed by a nominal 6-byte MAC address. In some implementations, the BSTA is not directly addressed; rather, it is addressed to a broadcast address. In some implementations, (for example, to limit the number of responses, control access to the medium, or determine (i.e., filter) the content of the buffer status report,) the AP may also include a mask and / or K-bit value (i.e., a value that the AP can use to instruct the BSTA to include only specific content in the buffer status report), thereby allowing the BSTA to filter those responses.

[0077] In some implementations, a Buffer Status Report (BSR RPT) is sent by the BSTA in response to a BSR Request (e.g., as a request response). In some implementations, the BSR RPT is sent by the BSTA upon request (e.g., after receiving a BSR Request), regardless of whether the BSTA's data buffer has any content. In some implementations, if the buffer is non-zero, the BSTA indicates the quantized buffer state during the BSR RPT, for example, by keeping certain bits (e.g., N bits of the MSB (e.g., 4 bits)) to 0. In some implementations, if the buffer is zero, the BSTA instead indicates the link quality metric during the BSR RPT, for example, by keeping certain bits (e.g., N bits of the MSB (e.g., 4 bits)) set to 1. In some implementations, the AP interprets the N bits of the MSB to detect whether the BSR is valid (i.e., includes the buffer state) or whether the BSR reflects the link quality of the BSTA.

[0078] In some implementations, a Clear BID (CLR BID) message is sent by the AP to the BSTA to clear the mnemonics assigned to one or more of the BSTAs. In some implementations, the AP includes a list of one or more BSTAs to which mnemonics have been assigned, and the BSTAs on the list clear those mnemonics. In some implementations, the AP does not specify the receiver's mnemonics in the CLR BID message, and all BSTAs receiving the CLR BID message clear those mnemonics.

[0079] In some implementations, a BID abbreviated ACK (BIDA) is an abbreviated block acknowledgment for one or more BSTAs to which a mnemonic is assigned. The abbreviated block ack is a hexadecimal representation where each bit position represents an ACK or NACK for the corresponding mnemonic that matches their exact position in the header. In other words, abbreviated block ACK 0xFA refers to an ACK for all mnemonics except the BSTAs at indices 8 and 6.

[0080] In some implementations, the query signal (INT_SIG) (also called the carrier wave (CW)) is an arbitrary electronic signal transmitted to a receiver to trigger a specific response. In the context of backscattering, in some implementations, INT_SIG is a signal that a receiver can use to backscatter information to some intended recipient. In some implementations, an AP, node B, WTRU, or other suitable device transmits INT_SIG for backscattering by another device such as an STA, UE, WTRU, or other suitable device.

[0081] In some implementations, BSTA can be backscattered on the UL, for example, based on ambient signals or dedicated signals such as INT_SIG or CW.

[0082] In some implementations, existing fields (e.g., duration fields) within existing frames (e.g., 802.11 MAC frames) can be overloaded, for example, by using spare fields within existing frames or by signaling values ​​in existing fields of existing frames not specified in the standard. This may have the advantage of providing backward compatibility, for example, because the definition of the frame format does not change. In some implementations, older devices see a valid frame but have values ​​that cannot be deciphered, while newer devices see a valid frame and decipherable values.

[0083] In some implementations, a mnemonic is a temporary substitute identifier for more permanent identifiers. For example, in some implementations, the transmitter address (TA) mnemonic is a temporary substitute identifier for the transmitter, and the receiver address (RA) mnemonic is a temporary substitute identifier for the receiver. In some implementations, the RA and TA mnemonics may be the same for devices. In some implementations, mnemonics are shorter than permanent identifiers. In some implementations, this has the advantage of lower signal transmission overhead. In some implementations, a mnemonic is unique for the lifetime that the AP considers the mnemonic to be valid. In some implementations, the device that assigns the mnemonic (the AP in this example) is responsible for ensuring that the mnemonic does not conflict (i.e., is not used by two or more devices served by the same AP). In some implementations, the assigned party is responsible for resolving ambiguity regarding which device is addressed by a mnemonic when the mnemonic conflicts (i.e., is used by two or more devices served by the same AP).

[0084] In some implementations, the Organizationally Unique Identifier (OUI) is an identifier that uniquely identifies an organization, such as a manufacturer (e.g., the first three bytes of the MAC address). For example, in some implementations, the Aruba OUI is set to the first three bytes of any MAC address of a device manufactured for Aruba (e.g., original design manufactured (ODM), original equipment manufactured (OEM), or manufactured in-house). For example, the Aruba OUI is different from, for example, the Cisco (trademark) or MediaTek (trademark) OUI.

[0085] In some implementations, an epoch is a term that refers to a finite, periodic duration maintained, for example, by an infrastructure node. In some implementations, an infrastructure node can apply (or perform) similar functions during each epoch within a clearly defined network (i.e., a centralized network with a central controller such as an AP or infrastructure node). In some implementations, an epoch is a time frame that an infrastructure node can apply to perform normal functions without allowing them to complete the function. In other words, in some implementations, an epoch allows an infrastructure node to preempt and reclaim system resources even if a particular task cannot be completed within an epoch. In some implementations, pending activities may, in some cases, wait to occur in the next epoch.

[0086] In some implementations, a trice is a variable subunit within an epoch. In some implementations, an epoch contains a certain number (e.g., T) trices. In some implementations, an infrastructure node assigns one trice to one activity and another to another. For example, a single trice may be dedicated to, optimized for, or otherwise designated for energy harvesting by a BSTA served by an infrastructure node. In some implementations, the determination and assignment of each trice to activities that can be performed by a serviced STA is implementation-specific. In some implementations, the determination and assignment of each trice to activities that can be performed by a serviced STA is made by the infrastructure node (i.e., the AP in this context).

[0087] Some implementations involve backscattering in the 802.11ah framework. In some implementations, a backscattering device (sometimes referred to herein as a backscattering STA or BSTA) utilizes various aspects of the 802.11 specification to perform uplink transmissions.

[0088] Figure 2 shows an exemplary backscatter in the 802.11ah framework. Figure 2 shows messages in an exemplary network including an AP, several legacy STAs (i.e., STAs not configured to backscatter), and several backscattering STAs grouped into groups 1 and 2 (BSTA1 and BSTA2). In the figure, blocks above the line associated with an entity represent transmissions by the corresponding entity, and blocks below the line represent receptions by the corresponding entity.

[0089] Although not explicitly stated, BSTA1 and BSTA2 may or may not be configured with a TWT and may be grouped by AP to have a restricted set of access slots (e.g., consecutive or discontinuous) within a RAW window. In some implementations, the BSTA recognizes the slots and their respective RAWs and / or periodicity, if any, when creating the association. In some implementations, a BSTA with a TWT may be configured to sleep until the TWT start time. In some implementations, such a BSTA may skip reading some beacons (e.g., beacons outside the TWT window and / or wake duration). Some BSTAs may not have a configured TWT, and such a BSTA may periodically receive beacons and may be configured with RAW slots during the association time.

[0090] The AP maintains a wake-up schedule for all devices configured and associated with the AP using a TWT. In this illustrative Figure 2, before the start of the RAW window, the AP performs the necessary conflict resolution and gains access to the medium by transmitting a self-addressed CTS, indicating to the devices that the medium is occupied only for the duration indicated in the self-addressed CTS. Figure 2 shows an illustrative modification that may be made on an existing network (e.g., supporting IEEE 802.11ah) to enable backscatter communication.

[0091] In Figure 2, the AP senses the medium during the backoff period following the DCF Inter-Frame Space (DIFS) and then sends a self-addressed CTS message. In some implementations, the legacy STA also senses the medium and backoffs during the DCF Inter-Frame Space (DCFS).

[0092] After the AP sends a self-addressed CTS, the legacy STA sets its NAV vector based on the reception of the self-addressed CTS from the AP, indicating the time period during which the medium is busy. The BSTA seeks the opportunity to be within the legacy STA's NAV due to backscattering.

[0093] In this example, a BSTA with a TWT configured may wake up within the time frame marked as RAW in Figure 1. Other BSTAs without a TWT configured may attempt to read the beacon and look for reception opportunities for themselves or other BSTAs / STAs in the vicinity.

[0094] In either case, to facilitate BSTA transmission, the AP transmits a BID message indicating the identification information of one or more BSTAs and their associated durations. In some implementations, the AP can trade off the amount of competition that will exist when it transmits the BID. Thus, in some implementations, the AP may limit the BID message and signal only the number of BSTA identification information and / or durations long enough to achieve the desired amount of competition. For example, in some implementations, if only a small number of BSTAs may be indicated in a BID message (e.g., due to BID message size limitations), the AP may keep the backscatter opportunity to a smaller duration so that it can give an opportunity to an orthogonal set of BSTAs when the AP next transmits a BID message.

[0095] In some implementations, APs may introduce more channel overhead by sending BID messages more frequently, but this can effectively reduce the competition rate, for example, because the AP is targeting a narrower set of BSTAs.

[0096] In Figure 2, the AP is effectively shown operating in full-duplex in the sense that it transmits a carrier wave (marked "carrier") as an INT_SIG for the BSTA to backscatter, and receives the backscattered signal from the BSTA. Note that in some implementations, this type of operation is not necessary, for example, if the AP can use another transmit-receive point (TRP), antenna, or other entity, or ambient RF signal, to provide an INT_SIG for the BSTA to use, and the AP can receive the corresponding backscattered signal.

[0097] In some implementations, if the AP configures a TWT on at least some of the BSTAs, anticipating the possibility of some BSTA being transmitted within the RAW, for example, the AP gains access to the channel and sends an INT_SIG. In some implementations, the query signal is used by the backscatter STAs (BSTA1, BSTA2) to send uplink data to the AP. Note that in some implementations, those BSTAs with TWTs configured may also be in contention for resources, for example, only within their designated RAW slots.

[0098] In some implementations, a BSTA without a configured TWT will perform DCF, but since the channel is secured earlier by the AP (e.g., by a self-addressed CTS), the BSTA may treat the channel as busy for a duration set by the NAV vector. However, in some implementations, if a self-addressed CTS is transmitted by the AP, the BSTA may ignore the CTS duration and seek a backscatter opportunity. To facilitate backscattering, in some implementations, the AP may alternate sending backscatter instruction (BID) messages and INT_SIG. This is reflected in Figure 2, for example, with alternating carrier and BID messages. In some cases (e.g., as shown), after the AP has received one or more backscatter transmissions, the AP may transmit a BIDA instead of a BID message to acknowledge one or more backscatter transmissions. The BIDA message may be followed by a short inter-frame space (SIFS) duration, and a guard interval may be introduced between consecutive RAWs. Each time a BID is transmitted, one or more identifiers of the backscattering STAs may be indicated in the BID message. In some implementations, if no identification information is provided in the BID message, the AP may allow any BSTA to be sent on that occasion. In some implementations, the AP may do so if it determines that the probability of a conflict is zero or low (e.g., the conflict is below a threshold conflict). In some implementations, the BSTA is identified in the BID message instruction by a shortened mnemonic (e.g., as described above) rather than by the full 6-byte MAC addressing scheme.

[0099] Figure 3 is a table illustrating an exemplary format for a BID message. In some implementations, the BID message is modeled after the 802.11 management message. For example, an 802.11 MAC message has a 2-bit type field and a 4-bit control subtype field. Thus, in this example, there are 16 possible control subtypes. These 16 subtypes are already fully utilized in the 802.11 specification, and it is not possible to add any new subtypes. However, in some implementations, it is possible to overload specific subtypes by interpreting other fields in the 802.11 MAC header.

[0100] The table in Figure 3 reflects section 8.2.4.2 of the 802.11 standard and describes the duration / ID field that can be used in several implementations as part of the BID message format. In some implementations, the field shown in Figure 3 is used instead of the duration / ID field in the 802.11 management frame. According to the 802.11 standard, the duration field is 16 bits, with 2 bits reserved. Furthermore, not all of the available 14 bits are defined. The 802.11 specification indicates that any value not in the table may be ignored by the STA, or that the maximum duration NAV vector will be set when a MAC payload with an uninterpretable duration (e.g., a value not included in the table) is received. Therefore, in some implementations, it is possible to specify and / or add new entries to this table so that newer devices conforming to newer versions of the standard interpret those versions correctly, while older devices that have not been upgraded to the latest version of the standard ignore MAC frames (due to an uninterpretable duration field).

[0101] Some implementations enable backscattering using MAC frames in 802.11. The example of duration fields shown in Figure 3 is illustrative and does not exclude other fields. For example, alternative and / or unused fields can be overloaded or used to achieve the same or similar objectives.

[0102] Figure 4 identifies several exemplary messages that may be available to STAs (e.g., those described herein) that are capable of applying the backscattering principle within the 802.11 framework in several implementations. Each exemplary message includes exemplary fields and an indication (in parentheses) of the exemplary length of each field in bytes. Such devices may implement the latest version of the 802.11 specification in several implementations. If the implemented 802.11 version incorporates backscattering techniques, such as those described below, then in some implementations, a backscattering STA may be able to correctly interpret the message (e.g., by interpreting the duration field) and share a medium with legacy STAs that either ignore the message (e.g., by setting the maximum duration NAV as considered herein) or interpret it by default as undecipherable or undefined.

[0103] The exemplary value in the exemplary duration field of the exemplary BID shown in Figure 4 includes a value that is "newly" specified (i.e., not defined in previous versions of the 802.11 standard) (in this example, 0x3E87), and therefore, legacy devices will interpret the MAC message by default, such as ignoring this MAC message or setting a maximum length NAV. In some implementations, if an AP determines that another STA requires UL transmission resources, or if an AP decides to send INT_SIG to facilitate backscattering of a BSTA, the AP may send a BID message that includes an actual (i.e., defined in previous versions of the 802.11 standard) 802.11 duration value (e.g., field number 3 "Duration 802.11 data" after the new interpretable duration field).

[0104] In some implementations, when an STA is associated with an AP, if the STA exhibits backscattering capability, the AP assigns a shortened address (e.g., 1 byte) to the device (e.g., during or at the time of association). This shortened address may be called a TA mnemonic. In some implementations, a BID message includes one or more transmitter address mnemonics (e.g., TA mnemonic 1(1)...TA mnemonic (1) in Figure 4) which may contain the hash value or shortened value of a 6-byte TA MAC address.

[0105] In some implementations, the TA mnemonic is one byte, but not all bits are used. In other words, the "actual TA mnemonic" or the identifying portion of the TA mnemonic may be less than one byte in length in some implementations. For example, in some implementations, the AP may reserve some of the TA mnemonic bits (e.g., non-identifying bits) for future use. In some implementations, the TA mnemonic is a temporary identifier for a BSTA that is uniquely identifiable within a session. The term session here refers to a specific duration for which devices participate in data communication. In some implementations, the AP adjusts the allocation of the TA mnemonic so that the AP recognizes the identifier of the BSTA that is being addressed or communicating (e.g., in TX and / or RX).

[0106] For example, in some implementations, a full set of N BSTAs in a system can be grouped into M smaller groups, each having (K=N / M) BSTAs. Each of the K BSTAs may be assigned one or more slots within a RAW window with an exemplary size of K ≤ 256. In this example, the AP can assign a TA mnemonic to each BSTA in a smaller group, making it unique within that smaller group, but the same TA mnemonic can be reused in other smaller groups, since the BSTAs do not wake up outside their TWTs, for example. In some implementations, the size of the TA mnemonic is such that the MAC frame size is not too large for the device to decode (or, for example, conveniently decode, decode within a threshold time, or decode using less than a threshold amount of resources) a MAC frame (e.g., a threshold-sized MAC frame) that has several mnemonics. In some implementations, several TA mnemonics may be concatenated and signaled within the same MAC PDU, and the BID message will be interpreted by each received TA mnemonic. In some implementations, BSTAs not constructed using TWTs can always compete with and access the medium, and therefore those BSTAs are not restricted by TWTs. For such BSTAs, the AP can reserve a subset of K mnemonics, or the AP can handle them using long forms.

[0107] In some implementations, for example, as shown in Figure 2, an 802.11ah-compliant device participates and obtains services from the AP. In some implementations, the AP and BSTA devices can interpret newly specified values ​​in the duration field and interpret messages differently from non-BSTA devices. In some implementations, DL transmission and UL transmission with the BSTA occur within the framework of the 802.11ah network.

[0108] Figure 4 is a block diagram showing exemplary messages and their associated formats across several implementations. In some implementations, these messages are control subtype messages. Because the subtype is 4 bits, in some implementations it is not possible to define new control subtype messages in 802.11. Therefore, in some implementations, the duration field (16-bit value) is modified to specify how the message payload should be interpreted. For example, in some implementations, if the subtype is control and the duration field is set to the hexadecimal 0x1F63, the message is interpreted as a CTSA with the format shown in Figure 4. The messages shown in Figure 4 are discussed above and also discussed where appropriate throughout this specification.

[0109] Figure 4 shows exemplary CTSA, CTSB, RTSB, BID, BSR RPT, BSR REQ, two exemplary CLRBID, and BIDA frames.

[0110] An exemplary CTSA frame includes a frame control field, a duration field, an RA field, an RA mnemonic field, and an FCS field. The frame control field is used to identify the IEEE 802.11 frame type and subtype; the duration field is used to define the backscatter-specific frame format; the RA field indicates the receiving STA address; and the RA mnemonic field is a short-length address assigned for the receiving STA having address RA. The FCS (frame check sequence) is used for error detection. As shown, these fields are located in the first, second, third, fourth, and fifth positions within the frame, respectively. These exemplary fields are 2 bytes, 2 bytes, 6 bytes, 4 bytes, and 4 bytes long, respectively. Note that in some implementations, a CTSA frame may include other fields, subsets of these fields, fields of different sizes, and / or order these fields differently. In some implementations, a frame performing the function of a CTSA frame may be referred to by any other preferred name. In this example, CTSA frames are identified by a duration field, such as the value 0x1F63.

[0111] An exemplary CTSB frame includes a frame control field, a duration field, an RA field, and an FCS field. As shown, these fields are located in the first, second, third, and fourth positions within the frame, respectively. These exemplary fields are 2 bytes, 2 bytes, 6 bytes, and 4 bytes long, respectively. Note that in some implementations, a CTSB frame includes other fields, subsets of these fields, fields of different sizes, and / or orders these fields differently. In some implementations, a frame that performs the function of a CTSB frame is called by any other suitable name. In this example, the CTSB frame is identified by the duration field, which is represented by the value 0x1F63, and the RA is represented by the value ff:ff:ff:ff:ff:ff. In this example, the RA value, ff:ff:ff:ff:ff:ff (i.e., all binary 1), indicates broadcast (i.e., all receivers are addressable). Individual receivers are addressable by this field in other implementations.

[0112] An exemplary RTSB frame includes a frame control field, two duration fields, an RA field, a TA field, a bind field, and an FCS field. Here, the second duration field indicates the time required to transmit the subsequent frame. The RA and TA fields indicate the receiving STA address and the transmitting STA address, respectively. The bind field is a flag indicating whether the BSTA requires INT_SIG. As shown, these fields are located in the 1st, 2nd, 3rd, 4th, 5th, 6th, and 7th positions in the frame, respectively. These exemplary fields are 2 bytes, 2 bytes, 2 bytes, 6 bytes, 6 bytes, 1 bit, and 4 bytes in length, respectively. Note that in some implementations, an RTSB frame includes other fields, subsets of these fields, fields of different sizes, and / or orders these fields differently. In some implementations, a frame that performs the function of an RTSB frame is called by any other suitable name. In this example, the RTSB frame is identified by the duration field, as indicated by the value 0x3E83.

[0113] An exemplary BID frame includes a frame control field, a duration field, a duration 802.11 data field, TA mnemonic fields 1-n, and an FCS field. Here, the duration 802.11 data field indicates the backscatter opportunity duration of each addressed BSTA identified by TA mnemonic fields 1-n. TA mnemonic fields 1-n indicate short-length addresses assigned to the transmit (i.e., backscatter) STA. As shown, these fields are located in the 1st, 2nd, 3rd, 4th-6th, and 7th positions in the frame, respectively. These exemplary fields are 2 bytes, 2 bytes, 2 bytes, 1 byte each, and 4 bytes long, respectively. Note that in some implementations, a BID frame includes other fields, subsets of these fields, fields of different sizes, and / or orders these fields differently. In some implementations, a frame that performs the function of a BID frame is referred to by any other preferred name. In this example, the BID frame is identified by a duration field, which is represented by the value 0x3E87.

[0114] An exemplary BSR RPT frame includes a frame control field, a duration field, a duration BS data field, a TA field, and an FCS field, where the duration BS data field indicates information about the buffer state or link quality. As shown, these fields are located in the first, second, third, fourth, and fifth positions within the frame, respectively. These exemplary fields are 2 bytes, 2 bytes, 2 bytes, 6 bytes, and 4 bytes long, respectively. Note that in some implementations, a BSR RPT frame may include other fields, subsets of these fields, fields of different sizes, and / or order these fields differently. In some implementations, a frame that performs the function of a BSR RPT frame may be called by any other preferred name. In this example, the BSR RPT frame is identified by the duration field, which is indicated by the value 0x3E8B.

[0115] The first exemplary BSR REQ frame includes a frame control field, a duration field, an RA field, a TA field, and an FCS field. As shown, these fields are located in the first, second, third, fourth, and fifth positions within the frame, respectively. These exemplary fields are 2 bytes, 2 bytes, 6 bytes, 6 bytes, and 4 bytes long, respectively. Note that in some implementations, a BSR REQ frame may include other fields, subsets of these fields, fields of different sizes, and / or order these fields differently. In some implementations, the frame that performs the function of a BSR REQ frame may be called by any other preferred name. In this example, the BSR REQ frame is identified by the duration field, which is represented by the value 0x3E8F.

[0116] The second listed exemplary BSR REQ frame includes a frame control field, a duration field, an RA field, a mask field, and an FCS field, where the mask field indicates a specific type of BSR report (e.g., a filtered report). As shown, these fields are located in the first, second, third, fourth, and fifth positions within the frame, respectively. These exemplary fields are 2 bytes, 2 bytes, 6 bytes, 6 bytes, and 4 bytes in length, respectively. Note that in some implementations, a BSR REQ frame may include other fields, subsets of these fields, fields of different sizes, and / or order these fields differently. In some implementations, the frame performing the function of a BSR REQ frame may be called by any other preferred name. In this example, the BSR REQ frame is identified by a duration field, such as the value 0x3E8F, and the RA is indicated by the value ff:ff:ff:ff:ff:ff. In this example, the RA value, ff:ff:ff:ff:ff:ff (i.e., all binary 1), indicates broadcast, meaning all receivers are addressable. Individual receivers can be addressed by this field in other implementations.

[0117] The first listed exemplary CLRBID frame includes a frame control field, a duration field, TA mnemonic fields 1-m, and an FCS field. Here, the TA mnemonic fields are used to identify the BSTA addressed by their abbreviated temporary IDs. As shown, these fields are located in the 1st, 2nd, 3rd-5th, and 6th positions in the frame, respectively. These exemplary fields are 2 bytes, 2 bytes, 1 byte each, and 4 bytes long, respectively. Note that in some implementations, a CLRBID frame includes other fields, subsets of these fields, fields of different sizes, and / or orders these fields differently. In some implementations, the frame that performs the function of a CLRBID frame is called by any other preferred name. In this example, the CLRBID frame is identified by the duration field, as indicated by the value 0x3EE3.

[0118] The second exemplary CLRBID frame includes a frame control field, a duration field, and an FCS field. As shown, these fields are located in the first, second, and third positions within the frame, respectively. These exemplary fields are 2 bytes, 2 bytes, and 4 bytes long, respectively. Note that in some implementations, a CLRBID frame may include other fields, subsets of these fields, fields of different sizes, and / or order these fields differently. In some implementations, a frame that performs the function of a CLRBID frame may be called by any other preferred name. In this example, the CLRBID frame is identified by the duration field, which is indicated by the value 0x3EE7.

[0119] An exemplary BIDA frame includes a frame control field, a duration field, a duration 802.11 data field, TA mnemonic fields 1-n, a shortened block ack field, and an FCS field. Here, the shortened block ack field indicates an acknowledgment for one or more recently received backscatter transmissions from one or more backscatterers. As shown, these fields are located in the 1st, 2nd, 3rd, 4th-6th, 7th, and 8th positions in the frame, respectively. These exemplary fields are 2 bytes, 2 bytes, 2 bytes, 1 byte each, ? bytes, and 4 bytes in length, respectively. Here, (?) indicates that the length of the shortened block ack may be dynamic and depend on the number of backscatter transmissions that have been acknowledged. For example, in some implementations, the shortened block ack field is 1 byte in length. Note that in some implementations, a CLRBID frame includes other fields, subsets of these fields, fields of different sizes, and / or orders these fields differently. In some implementations, a frame that performs the function of a CLRBID frame is called by any other preferred name. In this example, the CLRBID frame is identified by a duration field, which is represented by the value 0x3EE3.

[0120] In some implementations, the BSTA receiving the BID message scans the BID message for the presence of a send address mnemonic (TA mnemonic) to determine if it can access the medium immediately after SIFS. In some implementations, the TA mnemonic is a 1-byte shortened address instead of a 6-byte TA MAC address. In some implementations, the TA mnemonic is assigned to the BSTA by the AP within the CTSA message. In some implementations, the BID message indicates to the receiving BSTA the available duration for backscattering, for example, in the "Duration 802.11 Data" field. In some implementations, the number of TA mnemonics included in the BID message is 1 to n. In some implementations, the number of TA mnemonics included in the BID message is controllable by the AP, for example, depending on how much contention the AP allows in the network. In some implementations, in a fully scheduled network or a congested network, the AP may limit the number of TA mnemonics to exactly 1 in the BID message, for example. In some implementations, a BID message is a deferred acknowledgment for a transmission by an AP to one or more BSTAs that were previously requested but deferred using a CTSA. In some implementations, the AP is implemented with in-band full-duplex functionality and can receive backscatter communications. In some implementations, if the reception of a backscatter transmission is successful, the AP sends an acknowledgment piggybacked in the BID message in a BID acknowledgment (BIDA) message. An exemplary format of a BIDA message is shown in Figure 4. In some implementations, the BIDA is similar to a BID message except that it also includes an ACK (e.g., a block ACK) for a previously received transmission.

[0121] It should be noted that in a typical 802.11 system, CTS and RTS are used to address the hidden node problem. The hidden node problem occurs when a receiving STA (e.g., the STA sending the CTS in this example) is experiencing interference from a nearby STA that is not detected by the transmitting STA (e.g., the STA sending the RTS in this example). At a global level, CTS and RTS can be conceived not necessarily as a mechanism for avoiding interference, but as a mechanism for polling and reserving the medium. As discussed herein, CTS and RTS can be conceptualized as a polling and reservation mechanism in which a device is acknowledging the corresponding request. However, it should be noted that CTS and RTS are existing control messages and are not modifiable in the context of existing 802.11 systems. Therefore, in some implementations, new CTS and RSTS (e.g., CTS type A (CTSA) and RTS type B (RTSB)) are introduced as overloaded messages via the control format. In some implementations, the RTSB includes a BID flag to indicate to the receiver that the transmission requires assistance in the form of a query signal (i.e., INT_SIG or carrier wave) for backscatter. In some implementations, the CTSB is addressed to a broadcast address instead of a unicast address.

[0122] In current 802.11 networks, the transmitter and receiver addresses (TA and RA) are 6 bytes long. In current examples of CTS and RTS, the TA and RA are singular (i.e., CTS and RTS address only a single TA and RA). In some implementations, CTS and RTS generate overhead that may not be necessary in some deployments. Therefore, in some implementations, a BID message may address several TA addresses simultaneously. In some implementations, a BIDA is an acknowledgment message piggybacked on a BID message with a similar format. In some implementations, legacy addressing in 802.11 networks is via a 6-byte MAC address. In some implementations, the first 3 bytes are the OUI, and the remaining 3 bytes are the unique addressing under the OUI. In some implementations, the mnemonic is temporary identification information given by the AP to any STA or BSTA.

[0123] In some implementations, the mnemonic is a one-byte value assigned to the STA for short-term transactions (e.g., below a threshold time or threshold number of messages). In some implementations, the identification information is unique within the AP's service area for the duration of the transaction. In 802.11 systems prior to 802.11ah (i.e., non-compliant with 802.11ah), access to the medium is, in some cases, via DCF, Enhanced Distributed Channel Access (EDCA), or Point Coordination Function (PCF). In some such systems, legacy devices transmit and receive by performing a clear channel assessment and following a predetermined method. In some implementations, such legacy devices are unaffected by the various changes proposed herein and are seamlessly serviced by the AP (e.g., not adversely affected by the changes proposed herein).

[0124] Figure 5 shows an exemplary backscatter in an 802.11 system. Figure 5 shows messages in an exemplary network including APs, legacy STAs (i.e., STAs that are not configured to backscatter or do not support backscatter communication / transmission), and backscattering STAs. In the figure, blocks above the lines associated with entities represent transmissions by the corresponding entities, and blocks below the lines represent receptions by the corresponding entities.

[0125] In the example in Figure 5, the AP enables backscattering for backscattering STAs by placing a dedicated carrier. For example, after gaining access to the medium by sending the indicated self-addressed CTS message, the AP indicates to all legacy STAs that the channel will be occupied for the duration indicated in the duration field. In this example, the self-addressed CTS message is addressed to 0xFF:0xFF:0xFF:0xFF:0xFF:0xFF (i.e., broadcast to all STAs). Sending the self-addressed CTS forces legacy devices (e.g., the indicated legacy STAs) to set their NAV vectors for the duration indicated in the duration field of the self-addressed CTS. In some implementations, this address (i.e., the broadcast address 0xFF:0xFF:0xFF:0xFF:0xFF:0xFF) also indicates to BSTAs (e.g., the indicated backscattering STAs) to monitor for backscattering opportunities (i.e., that backscattering opportunities will occur in the near future during the identified duration). In some implementations, BSTA monitors backscatter opportunities by monitoring BID, for example, after SIFS.

[0126] In some implementations, the BSTA searches for the BID message in the appropriate slot after the CTSB. In some implementations, the request for transmission is via the RTSB and CTSA, even if not explicitly highlighted in the diagram (for example, the transmission of the RTSB and CTSA / B may precede those shown in the diagram). In some implementations, the CTSA / B is followed by the BID message monitored by the BSTA that transmitted the RTSB.

[0127] In the example in Figure 5, the backscatter STA detects a self-addressed CTS message sent by the serving AP indicating the availability of a dedicated backscatter opportunity and monitors the channel for a BID message carrying the backscatter opportunity configuration. In this example, the backscatter STA detects its identification information via a mnemonic in the BID and receives the relevant duration of the backscatter window in the BID. The backscatter STA competes for the backscatter channel within the identified window and receives an acknowledgment from the serving AP. In some implementations, the exemplary BTSA includes circuitry configured and / or programmed to perform these actions. In the example in Figure 5, the backscatter STA acquires the backscatter channel during the duration of the backscatter window and causes the AP to backscatter data on carriers sent by the AP for that purpose during the backscatter window. In this example, the AP acknowledges receipt of the backscatter data after SIFS from the end of the backscatter window.

[0128] In some implementations, knowing the identification information of the device that sent the RTSB and the device for which the CTSA was issued, the AP sends a BID message that is read by the BSTA, and the identified BSTA uses INT_SIG(carrier) to backscatter to the AP. In some implementations, the BID message includes an indication of the duration of the backscatter opportunity.

[0129] Several implementations include both energy harvesting and backscattering in 802.11 systems. For example, Figures 6A and 6B illustrate exemplary energy harvesting and backscattering. Figure 6B is a continuation of the figure shown in Figure 6A. In particular, Figures 6A and 6B show exemplary schemas that AP can apply to enable a power-optimized device to both harvest energy from the incident signal and use the query signal for backscattered data.

[0130] Figures 6A and 6B illustrate messaging in an exemplary network including an AP, a legacy STA, and three backscattering STAs: backscattering STA1, backscattering STA2, and backscattering STA3. In the figures, blocks above the lines associated with an entity represent transmissions by the corresponding entity, and blocks below the lines represent receptions by the corresponding entity. Note that the messaging in different trices in Figures 6A and 6B is illustrative and does not necessarily mean that it should be interpreted as a chronological event. In other words, Figures 6A and 6B do not mean that they should be interpreted as a cascaded sequence of events moving from one trice to another.

[0131] In the examples in Figures 6A and 6B, AP operates periodically, defined by one epoch. Each epoch is divided into k time trices. Each time trice t, 1 ≤ t ≤ k, can be selected by AP for a particular purpose. Each of the four exemplary trices in Figures 6A and 6B is considered below.

[0132] In some implementations, the network is deployed to support legacy STAs that employ various 802.11 protocols, and APs and BSTAs coexist with these legacy STAs.

[0133] Figures 6A and 6B show an exemplary epoch n in which the AP first performs DCF and acquires the medium. For example, it is assumed that in time trial 1, the AP first acquires access to the medium by listening to the channel during the DCF interframe space (DIFS) interval and backing off as appropriate.

[0134] Epoch n includes four exemplary time trises: time trise 1, time trise 2, time trise k-1, and time trise k. Note that an epoch may contain any number of preferred trises. In this example, time trise 1 can be used, for example, to schedule transmissions from a BSTA while a legacy STA is blocked by its NAV; time trise 2 can be used, for example, to transmit uplink data from a legacy STA while a BSTA is harvesting energy; time trise k-1 can be used, for example, for a BSTA to transmit data scheduled in time trise 1 to an AP (or harvest energy if those BSTAs have no data to transmit) while a legacy STA is blocked by its NAV; time trise k can be used to transmit downlink data to a legacy STA while a BSTA is harvesting energy.

[0135] In this example, time trial 1 is used to schedule the transmission of BSTAs. After the AP gains access to the medium, the AP sends a self-addressed CTS to cause the legacy devices to set their NAV vectors. Thus, the legacy STAs receive the self-addressed CTS message and set their NAVs based on the self-addressed CTS message. In this case, the NAV indicates to the legacy STAs that the medium is busy for the duration of time trial 1. In time trial 1 in the figure, the NAV indicates that the legacy STAs are treating the medium as busy for the entire duration of time trial 1, and therefore the legacy STAs neither transmit nor receive during this time period. The AP then transmits a BSR REQ message in the appropriate TWT of the BSTAs. In this example, the AP sends a single BSR REQ as shown in the figure. These BSTAs with BSRs send a BSR RPT to the AP. In this example, the BSR RPT is not shown, indicating that the BSTAs either do not have a BSR to transmit or do not have a TWT. In this example, the BSTA does not have a configured TWT and therefore competes for a channel to send the RTSB. In this example, each BSTA performs DCF by waiting only for DIFS and backing off as needed (as shown by the dashed line) before sending the RTSB message.

[0136] In some implementations, the BSTA is a low-power device that transmits these RTSB messages to the AP via backscatter. In some implementations, the RTSB messages are transmitted using a primary transmitter, but subsequent and / or later uplink transmissions (e.g., primary payload) are backscattered to the AP. In some implementations, such a hybrid approach may have the advantage of resulting in a significant reduction in the overall power consumption of the device. In some implementations, such a hybrid approach may have the advantage of increasing the resilience of RTSB transmissions by requiring the AP to grant reliable access to the channel without backscatter, whereas the primary transmission of the payload is transmitted via backscatter. In such implementations, similar approaches may be applied to avoid or minimize interference from nearby STAs.

[0137] In some implementations, BSTAs backscatter their RTSBs if available (e.g., matching) ambient signals exist. In some implementations, BTSAs do not transmit their RTSBs if there are no matching ambient signals. In this example, BSTAs can transmit RTSBs without INT_SIG (e.g., based on available ambient signals) to indicate that they have pending data in their buffers, the required duration, and whether backscattering needs to be enabled for further transmission. The RTSB message may also include a bind flag indicating to the AP that the BSTA requires INT_SIG to transmit on the UL.

[0138] In some implementations, the AP responds to the BSTA with a CTSA (after an appropriate delay, e.g., SFIS), indicating, for example, the RA of those BSTAs and the RA mnemonic that will be used for signaling and / or addressing for a temporary duration. In some implementations, the CTSA message defines the mapping from RA to RA mnemonic. In some implementations, the AP assigns a temporarily unique RA mnemonic and indicates, for example, the temporarily unique RA mnemonic in the CTSA message to the receiving BSTA. In some implementations, the BSTA is addressed by the RA mnemonic instead of being addressed by its full RA. In some implementations, the mnemonic is used by the receiving entity for both transmitting and receiving functions. In some implementations, the mnemonic identifies the BSTA as either a transmitter (TA mnemonic) or a receiver (RA mnemonic). In some implementations, the CTSA message indicates to the device addressed by the RA (and RA mnemonic) that its request has been received and queued. In some implementations, the CTSA message does not indicate to the BSTA that it is permitted to immediately transmit the payload and / or traffic. In some implementations, the AP transmits a CTSB message instead of a CTSA message. In some implementations, if a receiving BSTA receives a CTSB message with the RA address set to 0xFF:0xFF:0xFF:0xFF:0xFF:0xFF (i.e., broadcast), all BSTAs are backed off from transmission (for example, for a specified time period or until the BSTA detects a BID message).

[0139] In some implementations, if a CTSB message is sent by the AP, the BSTA attempts to detect a BID message indicating an opportunity to transmit on the UL. If a BID message is received, the BSTA attempts to detect and backscatter their RA mnemonics using the INT_SIG sent by the AP. The INT_SIG is shown as the carrier wave CW in the figure and is shown as Trice k-1 in Figures 6A and 6B.

[0140] In some implementations, the BSTA identifies a highly contested or hidden node-prone environment (e.g., based on detected self-addressed CTS messages and / or failures to receive CTSA / CTSB for a consecutive number of attempts and / or opportunities), transmits an RTSB message using the EDCA and main transceiver, receives a CTSA / CTSB, determines the RA mnemonic corresponding to its RA, monitors and detects a BID including an assigned TA mnemonic and an indication of the backscatter opportunity duration (e.g., indicated by the duration field in the BID), and backscatters its data in the assigned backscatter window using a dedicated carrier wave. In some implementations, the exemplary BTSA includes circuitry configured and / or programmed to perform these actions. In some implementations, the backscatter opportunity duration begins when the BID is received and continues for the time indicated by the duration field. In some implementations, the duration takes into account overhead (e.g., related to interframe space, e.g., switching, searching, etc.).

[0141] Time Trice 2 is used to schedule and transmit uplink data from the legacy STA while the BSTA harvests energy. After the NAV set in Trice 1 expires, the legacy STA performs DIFS and backoff to acquire medium, then transmits uplink data to the AP, which sends an ACK to acknowledge the uplink data. This is repeated in this example. While the uplink data is being scheduled and transmitted from the legacy STA, energy present in the RF waves on the channel is opportunistically harvested by the BSTA. In some implementations, CTSA / B in Trice 1 may indicate to the BSTA that it should backoff from transmission for a certain period of time, or until the BSTA detects a BID, so that the BSTA is resorted for energy harvesting.

[0142] Time trial k-1 is used for BSTAs to transmit data scheduled in time trial 1 to the AP (or harvest energy if those BSTAs have no data to transmit) while legacy STAs are blocked by their NAV. In this example, the AP sends a BID scheduling transmissions from the BSTAs and sets the NAV for the legacy STAs. Backscatter STA1 and backscatter STA3 backscatter data to the AP according to the schedule received in the BID, based on a dedicated INT_SIG (referred to as CW in the diagram) provided by the AP. Backscatter STA2, which has no data to transmit or is not scheduled to transmit data, opportunistically harvests energy present in the RF waves on the channel.

[0143] Time trial K involves transmitting downlink data to the legacy STA while the BSTA harvests energy. In this example, the AP sends a BID indicating that the downlink transmission is being sent to the legacy STA and that the BSTA should opportunistically harvest the energy. After DIFS and backoff, the AP transmits downlink data to the legacy STA. The legacy STA sends an ACK to acknowledge receipt of the downlink data. This is repeated in this example. While transmitting downlink data to the legacy STA, energy present in the RF wave on the channel is opportunistically harvested by the BSTA.

[0144] In some implementations, the AP selects a specific trice for scheduling downlink messages to a legacy STA. For example, in some implementations, a particular trice is deterministically better for the BSTA to harvest energy, which may be indicated in the BID message. In some implementations, the absence of a BID message at the beginning or "front" of a trice indicates to the BSTA that there may be an opportunistic interval for energy harvesting in that time trice. In some implementations, this is true regardless of whether the energy comes from a DL transmission from the AP to the STA or from a UL transmission from the STA to the AP. This occurs, for example, in trice 2 and trice k. As previously mentioned, the AP assigns a mnemonic to address the BSTA to keep overhead low.

[0145] In some implementations, the BSRRPT message is used to report the buffer state of the BSTA. In some implementations, the BSR RPT is 2 bytes, but the MSB4 bits are always set to 0. In some implementations, the BSR is a quantized representation and is represented by 12 bits. For example, the value signaled in the BSR RPT may be a truncated value mathematically represented as FLOOR(ACTUAL VALUE / BSC_SCALAR in bytes), where the FLOOR() function returns the truncated integer value. In some implementations, BSR_SCALAR is signaled by the AP during association. In some implementations, if the BSTA has no buffered data to send, it will need to send a BSR of 0. However, instead of sending a BSR of 0, the BSR RPT contains a quality measurement. In some implementations, the BSTA sends the quality report after prefixing the BSR data with 0xF in the MSB4 bits so that the AP understands that the data is not 0. In some implementations, the last 12 bits contain a measurement such as SINR or RSSI. As mentioned earlier, a mnemonic is temporary and unique within a subgroup until it is cleared. In some implementations, the AP transmits a message (e.g., a CLEARBID message) to all BSTAs in the subgroup to indicate that a previously assigned mnemonic via CTSA has been cleared and is addressable. In some implementations, the AP may then assign these mnemonics to other BSTAs, for example, at time epoch N+1.

[0146] Some implementations include one or more of the following concepts: Some implementations include a device that interprets existing fields in the media header to determine a backscatter control message subtype. Some implementations include addressing the device by a semi-permanent but locally unique mnemonic (identification information) instead of a permanent identification information (e.g., MAC address), where the mnemonic is an abbreviated identification information. Some implementations include a device that receives a signal from an infrastructure node with a mnemonic indicating that there is an opportunity for backscatter for a specified duration. Some implementations include a device that receives a measurement mask, a device that applies the measurement mask to its own mnemonic to determine whether the report should be transmitted to the infrastructure node, and a device that determines whether a quality measurement should be transmitted instead, for example, based on a buffer hold state. Some implementations include a device that receives a signal to postpone UL transmission for a specific or indefinite duration. Some implementations include a device that receives a time envelope and instructions for access subtypes to be permitted and / or denied within the envelope, where the envelope maintains a specific periodicity. Some implementations include a device that receives backscattering opportunities and duration limits, in conjunction with indicating the presence of an ambient signal source or a dedicated query signal. Some implementations include the AP determining the need to transmit non-message carriers at a specific time or time period to facilitate backscattering. Some implementations include the AP determining the need to transmit energy carriers over a specific duration to facilitate energy harvesting.

[0147] Figure 7 shows an exemplary multi-user backscatter in the 802.11 OFDMA framework. For example, Figure 7 shows an exemplary communication that enables backscatter communication for an 802.11ax system. Figure 7 shows messages in an exemplary network including APs, backscatter STAs, and legacy STAs.

[0148] In Figure 7, during the first time period 700, the AP first performs DIFS and backoff, then transmits the MU RTSB and receives the MU CTSB. Scheduling information for the legacy STAs is not provided in this frame, but as previously considered, this frame can be used to show the BSTA an EH opportunity. After SIFS, the AP transmits the preamble and HE field (described later) and transmits downlink transmissions to the legacy STAs, STA1, STA2, STA3, STA4, STA5, STA6, STA7, STA8, STA9, and STA11, on the downlink resource as scheduled. The legacy STAs receive these signals and transmit multi-user block acknowledgements (MU-BAs) to the AP. During the downlink transmissions to the legacy STAs, the backscattering STAs, BSTA1, BSTA2, BSTA3, and BSTA4, opportunistically harvest energy from the RF waves on the channel. After receiving the MU-BA, during the second time period 702, the AP transmits a trigger frame and, after SIFS, receives uplink transmissions from the legacy STAs, STA1 and STA3. STA1 pads its transmission to fill its allocated time resources. During these transmissions, BSTA2 opportunistically harvests energy. The AP transmits a MU-BA to acknowledge the uplink transmission. After transmitting the MU-BA, during the third time period 704, the AP performs DCIF and backoff, then transmits a MU RTSB and receives a MU CTSB. After SIFS, the AP transmits a preamble and HE field (described later) and transmits downlink transmissions to the legacy STAs, STA1, STA4, STA5, STA7, STA8, and STA9 on the downlink resources as scheduled. The AP also transmits a dedicated INT_SIG (CW in the figure) and a power-optimized waveform (dedicated POW in the figure). The legacy STA receives these signals and sends a Multi-User Block Acknowledgment (MU-BA) to the AP.During downlink transmission from the AP, the backscattering STAs BSTA1, BSTA2, and BSTA3 backscatter over the CW signal, while BSTA5 harvests energy from the RF wave of the power-optimized signal (dedicated POW). A more detailed explanation of the various techniques involved in Figure 7 follows below.

[0149] In some deployments, such as those implementing 802.11ax, DL and UL transmissions are typically centrally controlled and scheduled by APs. In earlier versions of 802.11 networks, STAs could access the media by performing conflict resolution in any time slot or within a limited access window (RAW). In such networks, APs could capture the media and preemptively transmit a CTS to a selected STA, eliminating the need for the STA to perform DCF. With 802.11ax, APs can have more powerful control over the media and enable multi-user transmissions over DL and UL.

[0150] Figure 7 shows an exemplary implementation in which the AP controls DL and UL transmissions while also enabling backscatter communication. Note that in the example in Figure 7, the AP still performs DCF to access the channel, and legacy devices similarly perform the same task and can claim the medium. In this example, the 802.11ax frame begins with a “legacy” preamble for backward compatibility. In some implementations, these fields allow older devices to recognize the presence of an 802.11 frame on the radio. In some implementations, this allows the CSMA / CA protocol to continue functioning in the presence of 802.11ax transmissions. In some implementations, the “legacy” preamble and Repeated Legacy-SIG (RL-SIG) fields are transmitted in parallel across all 20 MHz subchannels used for subsequent transmissions for backward compatibility. In some implementations, the subsequent field is used for 802.11ax purposes, using a mix of symbol formats, while "legacy" modulation is used for low-rate fields and backward compatibility, while other fields use closer subcarrier spacing and longer OFDMA symbols from 802.11ax.

[0151] In some implementations, the HE-SIG-A field (High Efficiency SIG) (referred to as the "HE field" in the diagram) contains information about the subsequent packet, including whether the packet is downlink or uplink, BSS color, modulation MCS rate, bandwidth and spatial stream information, and remaining time in the transmission opportunity. In some implementations, this field has different content for single-user frames, multi-user frames, and trigger-based frames, and is repeated in 802.11ax's "extended range mode". In some implementations, the HE-SIG-B field (also referred to as the "HE field" in the diagram) is included only for multi-user packets. In some implementations, the HE-SIG-B field contains information common to all receivers and other user-specific fields, and therefore its length depends on the number of users receiving the transmission. In some implementations, when OFDMA is used, the HE-SIG-B client-specific field is transmitted simultaneously in each subchannel used for subsequent packet transmissions. In some implementations, HE-SIG-B is a separate complex field. In some implementations, HE-SIG-B has a variable length depending on the number of clients addressed by the AP, as well as two different types of information: common and user-specific.

[0152] In some implementations, a common field (part of the “preamble” and / or “HE field” in the diagram) identifies the structure of the OFDMA subchannel or resource unit (RU) to be used, e.g., 18×26RU or 2×242RU. In some implementations, the common field includes other information common to all transmissions. In some implementations, several user-specific fields follow the common field. In some implementations, the AP uses these fields to identify how to transmit to each client, including, for example, the number of spatial streams, the MCS used by the AP, and / or whether the AP uses beamforming. In some implementations, the 802.11ax specification requires the transmitter to form HE-SIG-B fields simultaneously on multiple 20MHz channels, occupying the total bandwidth of the allocated channels. Therefore, if the AP is using an 80MHz channel, it will transmit four HE-SIG-B fields, one in each 20MHz subchannel.

[0153] In 802.11ax, the following terms apply and are used herein: Basic trigger frame: Specifies how and when a client device should respond. Multi-user Block Ack Request (MU-BAR): This trigger frame requests a block acknowledgment from multiple client devices simultaneously. The user information field specifies the frame to be acknowledged. Multi-user Request To Send (MU-RTS): This trigger frame is used to clear the radio before transmission, similar to a single-user RTS-CTS.

[0154] In some implementations, on the DL, the AP schedules multiple users, fills the HE header (i.e., the AP determines the content of the preamble / HE fields), and transmits the DL data on the RU. In some implementations, on the UL, the AP signals to devices that they have UL authorization to use. In some implementations, for this purpose, the AP transmits a trigger frame and transmits identification information of STAs that have UL authorization to use. Downlink packets may include ACKs and triggers, and uplink transmissions may similarly include trigger-based frames carrying ACKs. In some implementations, all of these signals are controlled and organized by the AP.

[0155] In some implementations, to enable backscattering in the 802.11ax framework, the AP sends a trigger frame containing an assist BSR flag and the locations of one or more RUs for assist BSR signaling. The AP may periodically send queries to the BSTA to determine the transmission rate on the UL and whether the BSTA has pending data to transmit.

[0156] In some implementations, if the receiving BSTA has pending data in its buffer, the receiving BSTA selects a designated RU marked for assist BSR (e.g., uniformly randomly). In some implementations, on the current frame following the trigger frame, the BSTA sends a BSR concatenated with its mnemonic on the selected RU, if the assist BSR flag was set to true. In some implementations, since the identification information of the BSTA sending the BSR is unknown (similar to the RACH process), the mnemonic is used for conflict resolution. In some implementations, the mnemonic is appended to the quantized BSR, and the entire content is scrambled by the mnemonic, for example, for additional protection.

[0157] In some implementations, the AP and / or coordinating TRP provide INT_SIG (CW in the figure) on the assisting BSR RU so that the devices can backscatter their BSRs. After the BSR is received from the BSTA (and from another STA that requires a UL transmission, e.g., using a RACH slot), the AP determines the identification information of the STA that has a UL transmission to send and matches their UL transmission opportunities and resource requirements (e.g., RU requirements) with the BSR requirements received from the BSTA. If sufficient capacity is available on the next frame, the AP sends the BSTA mnemonic and corresponding RU mapping for backscattering on the subsequent trigger frame. The BID flag may or may not be set to true.

[0158] In some implementations, if the BID flag is set to true, the AP ensures that there is another STA with a transmission on a UL on a designated set of RUs that the BSTA can use for backscattering. In some implementations, this is typical in moderately loaded networks, as the regular STA has a higher need to transmit and the BSTA is less likely to have a high demand. In some implementations, the BSTA receives a subsequent trigger frame, a BSTA mnemonic to RU mapping for backscattering, and a BID flag set to true, and backscatters on a specific RU.

[0159] In some cases, the AP may determine that there is no regular STA to transmit to and therefore select one or more TRPs (or antennas) to provide the INT_SIG. In such cases, the AP (or associated TRP) may assign any RU to provide a dedicated INT_SIG, and is not limited to the specific RU that will be assigned for the UL transmission of a particular STA. In some implementations, the AP transmits a subsequent trigger frame and a BSTA mnemonic mapped to one or more RUs for backscatter, and sets a BID flag to indicate that the BSTA can select any RU and is not limited to a specific RU. In this scenario, the BSTA selects a RU that maps to its mnemonic for backscatter (e.g., uniformly randomly).

[0160] In some implementations, the AP receives energy statistics from the BSTA within the UL transmission, and these statistics may indicate that the BSTA needs to harvest energy. In some implementations, the AP may be operating on a larger bandwidth (e.g., larger than a single 20MHz channel). In some implementations, the AP transmits, for example, a BSTA mnemonic, an index to one or more 20MHz subchannels assigned to the BSTA, an index to an energy carrier RU, and a time schedule in a common field within the HE-SIG-B field. In some implementations, the time schedule may indicate a start time offset and duration, implying possible periodic service. In some implementations, the AP may indicate that the power-optimized waveform (POW) time schedule is periodic, or the AP may decide on a different schedule for POW delivery and cancel the currently valid time schedule. In some implementations, if the AP indicates these in a common field within the HE-SIG-B header, it applies to any BSTA that may wish to consume its opportunity. In some cases, the frequency of periodic POWs may be too low, requiring a dedicated POW opportunity for the BSTA. In some implementations, the BSTA may receive from the AP, for example, an index to one subchannel, an index to the energy-carrying RU, a start time offset, and / or the duration of the dedicated POW opportunity, along with the BSTA's mnemonic, in a user-specific field within the HE-SIG-B field.

[0161] In some implementations, the AP may need to determine whether the BSTA and participating devices have the ability to filter out interference when the BSTA backscatters over normal downlink transmissions. In some implementations, the AP may, for example, determine, based on device capabilities, whether a dedicated INT_SIG (CW in the diagram) is required rather than opportunistic piggyback transmission over normal traffic.

[0162] For example, in Figure 7, after performing DIFS and backoff, the AP transmits a Multi-user RTSB (MU-RTSB) to indicate the STA on which the DL will be transmitted. The STA indicates acceptance by transmitting MU-CTS, MU-CTSA, or MU-CTSB (not shown). The AP schedules a highly efficient multi-user transmission to the STA using the OFDMA and / or MIMO paradigm. The transmission occurs on one or more resource units (RUs) for various STAs covering the operating bandwidth. The transmission is opportunistically used by the BSTA to harvest energy, as shown in Figure 7.

[0163] In some implementations, the BSTA opportunistically utilizes UL transmissions on the channel to backscatter its own transmissions, for example, based on the measured signal strength. For example, in some implementations, the BSTA receives a BID message indicating the availability of DL-assisted backscattering opportunities and UL-assisted backscattering opportunities, includes a corresponding configuration (e.g., a configuration optionally including measurement filtering rules), measures the DL received signal strength (e.g., based on the received BID message, the preamble in the DL frame, and / or a dedicated reference signal), applies the filtering rules to the measured DL received signal, determines that the received signal strength is below a first threshold, receives a trigger frame and / or a corresponding BID message from the serving AP, determines that the RUs are eligible for opportunistic UL-assisted backscattering and the corresponding multiple common or STA-specific measurement thresholds (e.g., including a lower second threshold and / or a higher third threshold), determines one or more sub-thresholds between the second and third thresholds (e.g., based on desired QoS requirements), measures the subband and broadband received signal strengths on the eligible RUs in the first portion of the UL frame, or alternatively, the same S The TA measures the subband and broadband received signal strength on eligible RUs during a previous UL frame or multiple previous UL frames transmitted by the TA, and based on the desired QoS requirements, selects one or more RUs with measured signal strengths that fall between two consecutive subthresholds within a lower second threshold and a higher third threshold, and transmits and / or reflects the selected one or more RUs using backscattering techniques. In some implementations, the exemplary BTSA includes circuitry configured and / or programmed to perform these actions. Since the backscattering here is based on UL transmission, in some implementations, the BSTA selects RUs (e.g., and the corresponding transmit STA) with measured signal strengths above a lower second threshold to ensure that the backscattered signal received at the AP is of reasonable strength. In some implementations, to reduce collisions between BSTAs, the BSTA may limit RU selection to those that satisfy received signal strengths below a higher third threshold.

[0164] Since transmission is OFDMA, certain tones are transmitted with higher power than others. Therefore, in some implementations, the AP may indicate to the BSTA (e.g., in the trigger frame or scheduling frame) which RU is best suited for energy harvesting for the appropriate BSTA in the MU-RTSB. Depending on the harvesting needs, in some implementations, the BSTA may harvest energy from information and power-carrying RUs intended for other STAs.

[0165] In some implementations, the AP transmits a trigger frame along with the transmission schedule on the UL and associated STA identification information. In some implementations, the schedule may also allow for random access opportunities on the UL. UL transmissions from the STA carry energy, which the BSTA can use to perform energy harvesting.

[0166] In some implementations, the AP (Application Platform) enables simultaneous DL (Deep Load) transmission and backscatter UL (Ultra Load) transmission by employing in-band full-duplex communication.

[0167] In some implementations, the BSTA receives a BID message indicating the availability of DL-assisted backscattering opportunities and UL-assisted backscattering opportunities, a configuration including a first threshold for DL-assisted backscattering, a configuration including a lower first threshold, one or more additional thresholds above the lower first threshold, and associated QoS for each additional threshold, determines a second threshold above the first threshold (e.g., based on desired QoS requirements), measures the DL received signal strength (e.g., based on the received BID message, the preamble in the DL frame, and / or a dedicated reference signal), and determines whether the received signal strength is above the lower first threshold, or whether, based on desired QoS, the received signal strength is above an additional threshold above the lower first threshold (e.g., based on the received BID message and / or DL ​​frame In some implementations, an exemplary BTSA includes circuitry configured and / or programmed to perform these actions. Based on the preamble, it selects one or more RUs in a DL frame for backscattering from a determined set of eligible RUs, and transmits and / or reflects the selected one or more RUs using backscattering techniques. In some implementations, the AP performs in-band receive operations for RUs received via self-interference rejection. In some implementations, the configuration may include a first threshold used by the BSTA to determine whether the BSTA should consider DL-assisted backscattering or UL-assisted backscattering. A lower first threshold and a higher second threshold may be used to limit competition between BSTAs during RU selection based on their required QoS.

[0168] In the examples described above, in some implementations, both the DL signal and / or UL signal may be ongoing active transmissions to and from STAs serviced by APs, and may be opportunistically used by BSTAs to modulate their information in addition to existing transmissions (e.g., to modulate their information bits on existing carriers and / or RUs currently allocated to other STAs). In some implementations, for example, alternatively, both the DL signal and / or UL signal may be dedicated power-optimized signal transmissions (e.g., sinusoidal transmissions transmitted directly from APs or requested by APs in coordination with the relevant STAs).

[0169] Figure 8 is a flowchart 800 illustrating exemplary backscattering by, for example, BSTA.

[0170] In step 802, the BSTA receives a BID message indicating DL and / or UL-assisted backscatter opportunities and may indicate a corresponding configuration. In some implementations, the configuration may indicate a signal intensity threshold, RUs eligible for backscatter transmission, and / or UL signal measurement configuration. In some implementations, the configuration includes a first threshold used by the BSTA to determine whether the BSTA should consider DL-assisted backscatter or UL-assisted backscatter. Lower first thresholds (e.g., second thresholds) and higher second thresholds (e.g., third thresholds) may be used to limit competition between BSTAs during the selection of RUs based on their required QoS, as will be further discussed herein.

[0171] In step 804, the BSTA measures the received signal strength of the DL signal that may be potentially used for backscattering. In some implementations, the DL received signal strength is determined based on the received BID message, the preamble in the DL frame, or a dedicated reference signal.

[0172] In condition 806, where the DL received signal strength exceeds a threshold (for example, a threshold associated with quality of service (QoS) requirements for backscatter transmission), the BSTA selects one or more resource units (RUs) of the DL frame for backscatter in step 808. In some implementations, the RUs are selected from a set of eligible RUs. In some implementations, the BSTA determines the set of eligible RUs based on the BID message, the preamble in the DL frame, or in any other preferred way.

[0173] In step 810, the BSTA modulates the DL signal on the selected RU in order to backscatter the signal.

[0174] Under condition 806, where the DL received signal strength does not exceed the threshold, the BSTA waits in step 812 to receive a trigger frame or further BID messages.

[0175] In step 814, the BSTA determines one or more eligible RUs for the UL frame for backscattering. In some implementations, the RUs are selected from a set of eligible RUs. In some implementations, the BSTA determines the set of eligible RUs based on the trigger frame or BID message, or in any other preferred manner.

[0176] In step 816, the BSTA measures the received signal strength of a UL transmission from another STA on a qualified RU. In some implementations, the BSTA measures the received signal strength of a UL transmission during the first portion of the UL frame, or the measurement is based on a previous measurement of a previous UL frame from the same STA.

[0177] In step 818, the BSTA selects one or more eligible RUs of the UL frame, for example, based on the measured received signal strength.

[0178] Under condition 820, that the UL received signal strength exceeds a threshold (e.g., a threshold related to quality of service (QoS) requirements for backscatter transmission), the BSTA modulates the UL signal on the selected RU to backscatter the signal. If the threshold is not exceeded, the flow returns to step 802. In some implementations, this condition evaluates the UL signal strength that should fall between a second and a third threshold (e.g., because the STA does not know the source location of the UL transmission).

[0179] Flowchart 800 illustrates the operation of the BSTA when the DL received signal is above or below a first threshold based on QoS requirements. In some implementations, if there are no eligible RUs that meet the criteria during the current transmission interval, the BSTA falls back to a future opportunity where a backscatter opportunity may occur.

[0180] MU-RTSB indicates the DL schedule for STA on a specific RU, and shows the BSTA the specific RU with INT_SIG. DL transmissions to STA on a specific RU are not interfered with. The query signal INT_SIG on a specific RU (indicated as CW) is used by the BSTA to backscatter to the AP. The AP performs in-band reception on these specific RUs. The AP transmits a power-optimized waveform (POW) specifically for the BSTA.

[0181] Some implementations include one or more of the following concepts: Some implementations include a device that receives a trigger frame, which is an index to one or more time-frequency resources to indicate backscattering requirements, and a competition opportunity signal within the trigger frame. Some implementations include a device that uniformly and randomly selects a time-frequency resource (e.g., RU) to transmit a competition-based backscattering request. Some implementations include a device that, on the current frame following the trigger frame, transmits a transmit request concatenated with its mnemonic on the selected time-frequency resource. Some implementations include an AP that provides a query signal on a time-frequency resource, or an AP that secures an ambient source (e.g., another STA received from the AP on the DL) on the indicated competition-based time-frequency resource. Some implementations include an AP that determines identification information for non-backscattering devices having DL transmits and matches their opportunity and resource requirements with transmit requirements received from backscattering devices. Some implementations include a device that receives a subsequent trigger frame, a mnemonic for the resource mapping, and a backscattering flag set to true. Some implementations include a backscatter device that backscatters on the current frame following a trigger frame on a specific RU mapped to a mnemonic. Some implementations include the backscatter device receiving an index (or more indices) to one or more energy carrier frequency resources and a time schedule in a common field in the header. In some implementations, the time schedule indicates a start time offset and / or duration. Some implementations include the backscatter device receiving an index to an energy carrier resource and a time schedule, along with its mnemonic, in a user-specific field in the 802.11 header, including a start time offset and duration.

[0182] Some implementations involve backscattering in OFDMA networks. In the 802.11 framework using CDMA-based waveforms, backscattering may be easier because the number of different codeword types used is very small, and that knowledge can be utilized when backscattering CDMA incident waveforms. However, most deployed 802.11 networks use OFDM waveforms, and backscattering modulated waveforms such as OFDM is difficult because much of the information is unknown. Nevertheless, it is possible to enable backscattering in the OFDM framework.

[0183] Figure 9 is a system diagram showing two exemplary systems illustrating different aspects of backscattering. The top-level system includes BSTAs a, b, c, d, and APs AP1 and AP2. In this example, BSTAb has bitstream 10101 for transmission to AP1. AP1 transmits DL data (A-MPDU) to participating cooperating AP (AP2) by determining a schedule for when BSTAb needs to transmit over the UL and forming an aggregated MAC PDU (A-MPDU) with a fixed smaller payload size and associated CRC (e.g., using the techniques described herein). AP2 transmits block ACK 11111 to AP1. In some implementations, this technique is suitable for low-rate reliable backscattering. In some implementations, while AP1 is transmitting DL data (A-MPDU), BSTAb uses backscattering to constructively or destructively interfere with the transmission received by AP2 (i.e., based on information blocks that need to be delivered to AP1). Subsequently, the block ACK received by AP1 from AP2 should effectively carry the information block from BSTAb (unless, for example, the channel has already corrupted some MPDUs).

[0184] The lowest level system includes a BSTA consisting of w, x, y, z, and APs AP1 and AP2. In this example, BSTAx has a bitstream 10101 for transmission to AP3. To backscatter the bitstream, BSTAx causes or avoids causing interference in the DL data from AP3 to AP4 in proportion to the duration of each MPDU in the A-MPDU. In this example, the channel changes sufficiently during the time BSTAx needs to signal 1, and the channel remains unchanged during the time BSTAx needs to signal 0. The zigzag lines represent these periods (e.g., one MPDU duration) when the channel remains unbroken, and the spaces between the black zigzag lines (e.g., one MPDU duration) indicate when the BSTA breaks the channel. The intermittent interference to the channel carries the information payload 10101 that BSTA is trying to transmit to AP3. In this example, AP4 demodulates the DL A-MPDU and finds CRC passes for the 1st, 3rd, and 5th MPDUs, and CRC failures for the 2nd and 4th MPDUs. AP4 transmits a block ACK to AP1 (indicating 10101), which AP1 interprets as backscatter data from BSTAb.

[0185] In this example, bistatic backscattering is enabled by utilizing numerous legacy STAs that may exist in the network without the need for modification. In some implementations, the backscatter data itself may include an FCS or CRC field to ensure, for example, that the failure to detect an STA is due to intentional interference and not to a degraded channel state. In some implementations, this is only applicable if the BSTA is close enough to the legacy STA to cause significant destructive interference. In some implementations, there are deployment scenarios where this is practical.

[0186] In some implementations, the BSTA detects a self-addressed CTS message indicating a dedicated backscatter opportunity, determines that the received signal strength falls below a first threshold, monitors UL transmissions from neighboring STAs and detects received signal strengths from the first STA that exceed a second threshold, transmits an RTSB requesting bistatic transmission to the first STA using the main transceiver, receives acknowledgment and bistatic backscatter opportunity configuration (e.g., information regarding the number of MPDUs in the A-MPDU addressed to the first STA), and determines the number of available MPDUs in the A-MPDU. The BTSA involves determining the total number of information bits available for transmission (e.g., including overhead bits) based on the number of backscatter opportunities, which may be singular or plural; and utilizing a bistatic backscatter opportunity configuration to modulate a DL signal by causing canceling interference to a specific MPDU within the A-MPDU transmitted to a first STA and / or constructive interference to the remaining MPDUs, wherein each success or failure in receiving the MPDU corresponds to backscatter bit-1 if it is an ACK from the BSTA and backscatter bit-0 if it is a NACK. In some implementations, the exemplary BTSA includes circuitry configured and / or programmed to perform these actions.

[0187] The example in Figure 9 shows an AP transmitting to a coordinating AP in a time instance where there is no DL data addressed to any given STA. However, in Figure 9, the coordinating AP (e.g., AP2 or AP4) can also represent an STA. In an exemplary case where there is data that coincidentally matches the STA, in some implementations, AP3 can transmit to the STA and the BSTA performs the same procedure as above. In this case, in some implementations, the STA transmits a block ACK indicating CRC failures for two MPDUs in the A-MPDU, and in some implementations, AP3 retransmits that information to the STA. Note that in some implementations, this use case covers BSTAs with very low transmission rates and very infrequent backscattering needs. In such cases, in some implementations, intentionally inducing interference to the channel to enable backscattering results in a very minimal increase in the retransmission rate, which can be ignored as overhead. In some implementations, this technique may be sufficient to support a system with several STAs and a small number of coordinating APs to support an IoT sensor (which is a BSTA) with minimal data rate requirements. In some implementations, the resulting aggregate system capacity is not significantly reduced, and the number of STAs supported by the AP also increases significantly.

[0188] Figure 10 shows an exemplary system 1000 configured to determine the DL channel state via inverse estimation. In the example in Figure 10, a low-power BSTA 1004 uses energy harvesting to operate an electronic circuit. Here, BSTA 1004 performs energy harvesting, and AP 1006 determines the harvesting rate of BSTA 1004. To facilitate this, in this example, AP 1006 measures the backscatter uplink 1008 from BSTA 1004 in the presence of (e.g., potentially intentional) distortion 1010. In some implementations, a downlink query signal 1012 is received by BSTA 1004 at significantly higher power than the backscatter uplink 1008. In some implementations, if a receiver 1014 on the AP can estimate the downlink incident waveform, the receiver 1014 may implement a control feedback loop 1016 and direct it to the transmitter 1018 on the AP to compensate during transmission.

[0189] Figure 11 is a line graph 1100 illustrating exemplary transmit-side compensation for channel fault. For example, in Figure 11, the transmitted signal 1102 from the AP is depicted as the amplitude of several tones. Signal 1104 shows the actual incident signal in a BSTA, also called a zero-energy (ZE) device (ZE in the figure). Note that if the purpose is to demonstrate frequency-selective fault, the incident INT_SIG will be received at unequal power levels. If this is the input signal for backscatter, the actual backscattered signal 1106 will be further degraded, which reduces the reliability of the communication. If the AP can estimate the incident signal in the BSTA / ZE device, the AP can pre-compensate the transmit to achieve a higher quality incident waveform in the BSTA. The compensated transmitted signal 1108 shows the result of the AP pre-compensating the transmitted waveform, for example, based on its ability to inversely estimate the channel. The compensated incident signal 1110 in ZE shows the actual incident signal following a channel fault when compensated transmit occurs. In some implementations, the method shown in Figure 11 enables the incident waveform at each ZE by compensating for multipath and distortion that may exist on non-LOS channels. In some implementations, a control loop is required in the AP to modify the phase and amplitude by estimating faults in the channel. In some implementations, the AP compensates for fluctuating channel gain by changing the energy harvest target and / or the transmitted waveform. Alternatively, if the AP can estimate the channel fault, the AP uses a predetermined and / or stored waveform appropriate for the channel that represents the best waveform. In some implementations, the AP uses a specific waveform that has historically been best performed for the channel that has been specifically estimated. In some implementations, stored and / or predetermined waveforms are used by the AP that represents the best waveform if the channel can be sufficiently inversely estimated.

[0190] Figure 12 shows an exemplary control loop 1200 implemented in AP1202 for channel estimation. AP1202 includes a controller 1210 and a filter 1212. Controller 1210 selects the waveform transmitted over radio channel 1204 and powers the backscatterer 1206. A reference vector 1214 is input for comparison of the harvested energy estimate with a reference Ref(y) 1232 encoded into a backscatter vector by the backscatterer 1204.

[0191] The wireless channel 1204 incorporates the effects of fading, as indicated by the downlink gain matrix 1220 and the uplink gain matrix 1222, noise 1224, and distortion 1226.

[0192] The backscatterer 1206 includes Inc(y) 1230, which stores and / or harvests the energy of the received signal y, and Ref(y) 1232, which is a reference signal modulated into a backscatter vector over the received signal y to help the access point perform inverse channel estimation.

[0193] In some implementations, compensation is performed at the AP to adapt to changing propagation conditions and distortions that may occur on the radio channel 1204, for example, due to the presence of other devices near the AP. In some implementations, the received waveform at the ZE backscatterer 1206 can be modeled as a linear combination of attenuated control vectors and distortions, for example, as shown in Figure 12. In some implementations, this allows the AP to make several decisions. For example, the AP may decide to use the RF spectrum as divided into constant-width subcarriers and / or as variable-width subcarriers. In some implementations, the gain matrix shown in Figure 12 may be sparse, for example, because the radio channel 1204 is memoryless and linear. In some implementations, mathematically, for this reason, the off-diagonal elements (cross product between tones) are zero.

[0194] Figure 13 shows an exemplary control loop 1300 for multi-carrier, multi-STA estimation of channel 1304, including BSTA 1306.

[0195] AP1302 includes a controller 1310 and a filter 1312. The controller 1310 selects the waveform transmitted over the radio channel 1304 and powers the backscatterer 1306. A reference vector 1314 is input for comparison of the harvested energy estimate with a reference Ref(y) 1332 encoded into a backscatter vector by the backscatterer 1304.

[0196] The wireless channel 1304 incorporates the effects of fading, as indicated by the downlink gain matrix 1320, the uplink gain matrix 1322, noise 1324, and distortion 1326.

[0197] The backscatterer 1306 includes Inc(y) 1330 for storing and / or harvesting the energy of the received signals y1, y2, and yk, and Ref(y) 1332, which is a reference signal modulated to a backscatter vector on the received signal y to help the access point perform inverse channel estimation.

[0198] In some implementations, the control loop 1300 allows AP1302 to model the control loop so that it is decoupled from K subcarriers, one for each BSTA. In some implementations, the waveform closed-loop tracking system is decoupled from subcarrier tracking. In some implementations, the subcarriers are coupled at the receiver level of the BSTA via a power harvesting circuit. Figure 13 shows an exemplary multicarrier extension in which multiple BSTAs can be back-channel estimated. Thus, in some implementations, a framework is established so that AP1302 can catalog waveforms or patterns and associated estimated channels that can be used at future times. In some implementations, AP1302 determines whether energy harvesting is necessary based on the harvesting rate estimate in BSTA1306. In some implementations, AP1302 estimates the energy harvesting rate of BSTA1306 (e.g., autonomously, without feedback from the BSTA) by back-estimating the backscattered channels and propagation state. In some implementations, the AP1302 implements a control loop to modify the phase and amplitude of carriers or subcarriers by estimating faults in the backscatter channel. In some implementations, the AP1302 adaptively compensates for fluctuating channel gain by changing the energy harvesting target. In some implementations, the AP1302 catalogs waveforms appropriate for the estimated channel and uses a predetermined or cataloged set of waveforms appropriate for the currently estimated channel that represent the best incident waveform in the BSTA. In some implementations, the AP1302 uses control vectors to determine the RF spectrum divided into constant-width subcarriers and / or variable-width subcarriers to maximize the energy harvesting rate.

[0199] Figure 14 shows an exemplary buffer estimation of BSTAs by AP. Figure 14 also shows an example of how masks can be used to limit the number of BSR requests that can be addressed individually. For example, applying the mask (0011) indicates that a (single) BSR request will be addressed to all BSTAs that have a mnemonic defined under branch (##11) which includes (1111, 0111, 1011, 0011). Alternatively, if the mask (0111) is applied, a (single) BSR request will be addressed only to BSTAs that have a mnemonic defined under branch (#111) which includes (1111, 0111).

[0200] In some implementations, as described herein for example, the AP decides when to control the channel for backscatter transmission. In some implementations, the AP does this by performing a DCF, sending a self-addressed CTS, and reserving the medium for the duration of BSTA activity. In some implementations, the AP decides whether there is a need to protect the medium in those cases. In some implementations, the AP periodically polls the BSTAs and requests them to send buffer status reports. In some implementations, transmitting a BSR to each BSTA is overhead, and some BSTAs may have nothing to send and have 0 bytes in their buffers.

[0201] To minimize this, in some implementations, the AP groups BSTAs into several homogeneous sets, where the combined requirements for UL transmission from BSTAs are approximately equal in each set. In some implementations, this is estimated from historical activity or based on device capabilities. In other words, in some implementations, the AP promotes homogeneous groups so that no group overwhelms the AP with a greater need for backscattering compared to others.

[0202] To enable this, in some implementations, the AP assigns a mnemonic as detailed in the previous section. In some implementations, a predetermined number of bits are used as a unique identification number. In some implementations, a second predetermined number of bits are used for a random value used by the AP for probing. In some implementations, the AP sends a command requesting each BSTA to respond with a random value within a specified group of random values.

[0203] In some implementations, as shown in Figure 14, for example, the AP sends an arbitration value, sometimes called Arbit_Val, e.g., a mask, and the BSTA performs bitwise logical operations to determine whether it needs to respond. For example, in some implementations, if the expression (mnemonic & Arbit_Val) > 0 evaluates to "0" (false), the BSTA does not respond because arbitration is not involved. Note that in some implementations, the AP can determine the arbitration value and a previously assigned mnemonic so that more than N% of the devices do not need to access the medium simultaneously. In some implementations, if the expression evaluates to greater than 0 and the BSTA has data in the buffer, the BSTA sends the buffer state. In some implementations, if the above expression evaluates to greater than 0 but the BSTA does not have data in the buffer, the BSTA does not send the buffer state. In some implementations, by doing this in a structured manner, the number of bits in the Arbit_Val mask is incremented by 1 each time, and eventually, the BSRs of all BSTAs over the decision interval are known without collisions. In some implementations, the AP can be configured to employ tree search and Aloha techniques to determine a unique identification number.

[0204] Some implementations include a device that receives a backscatter window of time and access subtypes allowed within an envelope, where the envelope maintains a specific periodicity. Some implementations include a device that implements competition-based access requests by backscattering an incident signal over a set of time-frequency resources. Some implementations include a device that receives an acknowledgment that postpones uplink data transmission for future backscatter opportunities. Some implementations include a device that is addressed by a locally unique mnemonic (identification information) for future opportunities, rather than by permanent identification information (e.g., MAC address), where the mnemonic is an abbreviated identification information. Some implementations include a device that receives from an infrastructure node a duration limit with a signal and its mnemonic indicating that an opportunity for backscatter exists for a specified duration. Some implementations include a device that implements non-compete access by backscattering an incident signal over a set of time-frequency resources. Some implementations include a device that receives a measurement mask and applies the measurement mask to its mnemonic to determine whether the report should be transmitted to an infrastructure node, while in some implementations the device determines, based on a buffer hold state, whether quality measurements should be transmitted instead. Some implementations include a device that receives energy carriers over a specific duration to facilitate energy harvesting.

[0205] While features and elements are described above in specific combinations, those skilled in the art will understand that each feature or element can be used alone or in any combination with other features and elements. In addition, the methods described herein can be implemented in computer programs, software, or firmware embedded in computer-readable media for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor associated with software can be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A method implemented in a wireless station (STA), Receiving backscatter instruction (BID) messages indicating backscatter opportunity, resource unit (RU), and downlink (DL) signal intensity thresholds, A method comprising backscattering a DL transmission to generate a backscattered transmission, based on the fact that the signal intensity of the DL transmission received on the RU as indicated in the BID message exceeds the DL signal intensity threshold.

2. The method according to claim 1, wherein the backscatter of the DL transmission occurs on the basis that the duration of the DL transmission exceeds the payload transmission requirements associated with the backscatter transmission.

3. The method according to claim 1, further comprising backscattering an uplink (UL) transmission from another STA received on the RU, indicated in the BID message, in order to generate another backscatter transmission, based on the fact that the intensity of the DL transmission does not exceed the DL signal intensity threshold.

4. The method according to claim 3, wherein the backscattering of the UL transmission occurs based on the fact that the signal intensity of the UL transmission exceeds a UL signal intensity threshold and the duration of the UL transmission exceeds the payload transmission requirements associated with other backscattering transmissions.

5. The method according to claim 1, further comprising measuring the signal strength of the DL transmission based on the BID message, the preamble in the DL frame, or a dedicated reference signal.

6. The method according to claim 4, wherein the DL signal intensity threshold and the UL signal intensity threshold are the same threshold.

7. The method according to claim 1, wherein the BID message includes a management message.

8. The method according to claim 1, wherein the BID message includes an affirmative response message.

9. The method according to claim 1, wherein the DL signal intensity threshold is associated with quality of service (QoS).

10. The method according to claim 1, wherein the backscatter transmission is generated based on the fact that the signal intensity of the DL transmission exceeds the DL signal intensity threshold and the duration of the DL transmission exceeds the payload transmission requirements.

11. It is a wireless station (STA), A receiver configured to receive backscatter instruction (BID) messages indicating backscatter opportunity, resource unit (RU), and downlink (DL) signal intensity thresholds, STA comprises a transmitter configured to backscatter a DL transmission in order to generate a backscatter transmission based on the fact that the signal strength of the DL transmission received on the RU as indicated in the BID message exceeds the DL signal strength threshold.

12. The STA according to claim 11, wherein the transmitter is further configured to backscatter the DL transmission based on the duration of the DL transmission exceeding the payload transmission requirements associated with the backscatter transmission.

13. The STA according to claim 11, wherein the transmitter is further configured to backscatter an uplink (UL) transmission from another STA received on the RU, indicated in the BID message, in order to generate another backscatter transmission based on the fact that the intensity of the DL transmission does not exceed the DL signal intensity threshold.

14. The STA according to claim 13, wherein the transmitter is further configured to backscatter the UL transmission based on the fact that the signal intensity of the UL transmission exceeds a UL signal intensity threshold and the duration of the UL transmission exceeds the payload transmission requirements associated with other backscatter transmissions.

15. The STA according to claim 11, wherein the receiver is further configured to measure the signal strength of the DL transmission based on the BID message, the preamble in the DL frame, or a dedicated reference signal.

16. The STA according to claim 14, wherein the DL signal intensity threshold and the UL signal intensity threshold are the same threshold.

17. The STA according to claim 11, wherein the BID message includes a management message or an acknowledgment message.

18. The STA according to claim 11, wherein the DL signal intensity threshold is associated with quality of service (QoS).

19. The STA according to claim 11, wherein the transmitter is further configured to generate the backscatter transmission based on the fact that the signal intensity of the DL transmission exceeds the DL signal intensity threshold and the duration of the DL transmission exceeds the payload transmission requirements.

20. A method implemented in a wireless station (STA), Receiving backscatter instruction (BID) messages indicating backscatter opportunity, resource unit (RU), and downlink (DL) signal intensity thresholds, This includes, in order to generate a backscattered transmission based on the signal strength of the DL transmission, backscattering the transmission received on the RU as indicated in the BID message, If the signal strength of the DL transmission exceeds the DL signal strength threshold, the transmission is backscattered based on the received DL signal. A method wherein, if the signal strength of the DL transmission does not exceed the DL signal strength threshold, the transmission is backscattered based on the received uplink (UL) signal.

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