Method and apparatus for adaptive indirect carrier modulation

Abstract

To provide an indirect carrier modulation transmission system.SOLUTION: A wireless transmit / receive unit, i.e., WTRU, selects a constellation from a set of constellations corresponding to a symbol configuration of indirect carrier modulation, i.e., ICM, on the basis of at least one constellation performance validity indicator, each constellation performance validity indicator corresponding to a constellation in the set of constellations, and can transmit data while harvesting energy using the selected constellation and symbol configuration.SELECTED DRAWING: Figure 15

Description

[Background technology]

[0001] Indirect carrier modulation has the potential to enable ultra-low power transmitters that can be deployed on a large scale. Existing systems that employ indirect carrier modulation include near-field communication (NFC) and radio-frequency identification (RFID).

[0002] In RFID, a so-called reader can interact with multiple devices ("tags"). The reader supplies radio frequency (RF) power and data to the tags via the downlink (DL). The tags transmit data back using the RF power provided by the reader. The tags transmit data by modulating the antenna load using simple schemes such as on-off keying (OOK) and binary phase shift keying (BPSK), which reflects the RF carrier transmitted by the reader back to the reader. Passive RFID devices generally use OOK modulation in the uplink, which is suitable for energy harvesting in the downlink, while semi-passive and active devices employ, for example, BPSK, which is suitable for transmitting high energy per bit in an indirect carrier modulation framework. A particular product supports one frequency band and communication mode. The reader and all tags communicate via the same frequency channel. Therefore, the tags simultaneously receive power in the DL and transmit data in the uplink (UL) using the same carrier frequency.

[0003] RFID systems use indirect carrier-modulated transmission between backscatter-coupled devices, where the reader and tag are in the far field of each other's antennas. RFID tags can be passive (i.e., have no independent power source), semi-passive (i.e., have a small battery), or active (i.e., have an independent power source such as a battery). Existing RFID standards specify only one communication mode: the reader / writer mode, in which the reader initiates all communication by interrogating the tag. The tag responds only when interrogated by the reader. Existing RFID standards specify several frequency bands, ranging from low frequency (125 kHz) to super-high frequency (SHF) (5.8 GHz). RFID communication distances can extend up to 100 m.

[0004] NFC can be considered an improved version of RFID. NFC is used in a variety of applications, such as home automation, consumer electronics, and smart meters. NFC systems use indirect carrier-modulated transmission between inductively coupled devices, with the reader and tag in the near field of each other's transducers. NFC devices can be passive, semi-passive, or active. Existing NFC standards specify a single frequency band of 13.56 MHz and three communication modes: "reader / writer," "card emulation," and "peer-to-peer." NFC communication ranges from approximately 1 cm up to 1 m. Summary of the Invention

[0005] A method and apparatus for operation by a wireless transmit / receive unit (WTRU) that can select a constellation from a set of constellations corresponding to symbol configurations of indirect carrier modulation (ICM) based on at least one constellation performance validity metric, each constellation performance validity metric corresponding to a constellation from the set of constellations, and can transmit data while harvesting energy using the selected constellation and symbol configuration. [Brief explanation of the drawings]

[0006] Additionally, like reference numbers in the figures refer to like elements. [Figure 1A] FIG. 1 is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented. [Figure 1B] 1B is a system diagram illustrating an exemplary wireless transmit / receive unit (WTRU) that may be used within the communication system shown in FIG. 1A, according to one embodiment. [Figure 1C] 1B is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communication system shown in FIG. 1A, according to one embodiment. [Figure 1D] FIG. 1B is a system diagram illustrating a further exemplary RAN and a further exemplary CN that may be used within the communication system shown in FIG. 1A, according to one embodiment. [Figure 2A] FIG. 1 illustrates a primary indirect carrier modulation scheme using OOK and BPSK and an associated two-point constellation. [Figure 2B] FIG. 1 illustrates a primary indirect carrier modulation scheme using OOK and BPSK and an associated two-point constellation. [Figure 3A]FIG. 1 illustrates an example of a secondary indirect carrier modulation scheme and associated four-point constellation using QPSK and 4-QAM. [Figure 3B] FIG. 1 illustrates an example of a secondary indirect carrier modulation scheme and associated four-point constellation using QPSK and 4-QAM. [Figure 4A] FIG. 1 illustrates ICM state transitions and transmit waveforms associated with the commonly used Manchester coded OOK indirect carrier modulation scheme. [Figure 4B] 1 is a chart illustrating ICM state transitions and transmit waveforms associated with the commonly used Manchester coded OOK indirect carrier modulation scheme. [Figure 5A] FIG. 1 is a diagram illustrating another example of a Manchester coded indirect carrier modulation scheme employing BPSK to transmit one bit per symbol. [Figure 5B] 1 is a chart illustrating another example of a Manchester coded indirect carrier modulation scheme employing BPSK to transmit one bit per symbol. [Figure 6A] FIG. 1 shows a hybrid phase-amplitude indirect carrier modulation scheme in accordance with an embodiment of the present principles; [Figure 6B] 1 is a chart illustrating a hybrid phase-amplitude indirect carrier modulation scheme in accordance with an embodiment of the present principles; [Figure 7A] 1 is a chart illustrating a decoding scheme for hybrid phase-amplitude indirect carrier modulation transmission, in accordance with an embodiment of the present principles; [Figure 7B] 1 is a chart illustrating a decoding scheme for hybrid phase-amplitude indirect carrier modulation transmission, in accordance with an embodiment of the present principles; [Figure 8A] 1 is a table illustrating an example of a sparse block code. [Figure 8B] FIG. 1 illustrates an example of a sparse block code. [Figure 8C] 1 is a table illustrating an example of a sparse block code. [Figure 9A] 1 is a table illustrating a sparse block code in accordance with an embodiment of the present principles; [Figure 9B] FIG. 1 illustrates a sparse block code, in accordance with an embodiment of the present principles; [Figure 9C] 1 is a table illustrating a sparse block code in accordance with an embodiment of the present principles; [Figure 10] FIG. 1 illustrates one embodiment of a method according to the present principles. [Figure 11] FIG. 10 illustrates a further embodiment of a method according to the present principles. [Figure 12] FIG. 10 illustrates a further embodiment of a method according to the present principles. [Figure 13] FIG. 10 illustrates a further embodiment of a method according to the present principles. [Figure 14] 1 shows an example of a possible transmission method in accordance with an embodiment of the present principles; [Figure 15] 1 shows an example of a possible transmission method in accordance with an embodiment of the present principles; [Figure 16] 1 shows an example of a possible transmission method in accordance with an embodiment of the present principles; [Figure 17] 1 shows an example of a possible transmission method in accordance with an embodiment of the present principles; [Figure 18] 1 shows an example of a possible transmission method in accordance with an embodiment of the present principles; [Figure 19] 1 shows an example of a possible transmission method in accordance with an embodiment of the present principles; [Figure 20A] 1 is a table illustrating an embodiment of a sparse block coding scheme. [Figure 20B] 1 is a table illustrating an embodiment of a sparse block coding scheme. [Figure 21A] 1 is a table showing examples of high density block codes and associated carrier modulation schemes. [Figure 21B] FIG. 1 illustrates an example of a high-density block code and associated carrier modulation scheme. [Figure 22] 1 is a table showing a time domain description of a transmit waveform corresponding to a particular high density block code. [Figure 23A] 1 is a table illustrating an embodiment of a high density block coding scheme. [Figure 23B]1 is a table illustrating an embodiment of a high density block coding scheme. [Figure 24] FIG. 10 illustrates a further embodiment of a method according to the present principles. [Figure 25] FIG. 10 illustrates a further embodiment of a method according to the present principles. DETAILED DESCRIPTION OF THE INVENTION

[0007] (Exemplary Network for Implementing the Embodiments) 1A illustrates an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. Communication system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcasts, etc., to multiple wireless users. 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 employ one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multicarrier (FBMC), etc.

[0008] 1A, communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a “station” and / or “STA,” may be configured to transmit and / or receive wireless signals and may include user equipment (UE), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, cellular 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 industrial and / or automated processing chain contexts), consumer electronics devices, devices operating in commercial and / or industrial wireless networks, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be referred to interchangeably as a UE.

[0009] The communications system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communications networks, such as the CN 106, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNodeB, a Home Node B, a Home eNodeB, a gNB, an NR Node B, a site controller, an access point (AP), a wireless router, etc. Although the base stations 114a, 114b are each shown as a single element, it will be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0010] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), a relay node, etc. The 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 a cell (not shown). These frequencies may be licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage for a particular geographic area, which may be relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one for each sector of the cell. In one embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell, for example, using beamforming to transmit and / or receive signals in desired spatial directions.

[0011] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over the air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0012] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base stations 114a of the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 116 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed Uplink (UL) Packet Access (HSUPA).

[0013] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c in the RAN 104 may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-APro).

[0014] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c in the RAN 104 may implement a radio technology such as NR radio access, which may establish the air interface 116 using New Radio (NR).

[0015] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c in the RAN 104 may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may jointly implement LTE radio access and NR radio access, e.g., using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0016] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement a wireless technology such as IEEE 802.11 (i.e., Wireless Fidelity, WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), GSM Evolution (Enhanced Data rates for GSM Evolution, EDGE), GSM EDGE (GERAN), or the like.

[0017] 1A may be, for example, a wireless router, a Home Node B, a Home eNode B, or an access point and may utilize any suitable RAT to facilitate wireless connectivity in a local area such as a location such as a business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, etc. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may establish a picocell or a femtocell using a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-APro, NR, etc.). As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not need to access the Internet 110 through the CN 106.

[0018] The RAN 104 may communicate with the CN 106, which may be any type of network configured to provide voice, data, application, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 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, mobility requirements, etc. The CN 106 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions such as user authentication. Although not shown in FIG. 1A , it will be understood that the RAN 104 and / or CN 106 may communicate directly or indirectly with other RANs that use the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may utilize NR radio technology, the CN 106 may also communicate with another RAN (not shown) using GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0019] The CN 106 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 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 that 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. The other networks 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the other networks 112 may include another CN connected to one or more RANs, which may use the same RAT as the RAN 104 or a different RAT.

[0020] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links.) For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with a base station 114a that can use cellular-based wireless technology and a base station 114b that can use IEEE 802 wireless technology.

[0021] 1B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1B, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a positioning system chipset 136, such as a Global Positioning System (GPS), and / or other elements 138. It will be understood that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0022] The processor 118 may be a general-purpose processor, a special-purpose 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) circuit, 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 the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1B depicts the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0023] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., the base station 114a in FIG. 1A) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0024] 1B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0025] The transceiver 120 may be configured to modulate signals transmitted by the transmit / receive element 122 and demodulate signals received by the transmit / receive element 122. As mentioned above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0026] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from 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). The processor 118 may also output user data to the speaker / microphone 124 and / or the display / touchpad 128. Furthermore, the processor 118 may access information from and store data in any type of suitable memory, such as non-removable memory 130 and / or removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, etc. In other embodiments, the processor 118 may access information from and store data in memory that is not physically located on the WTRU 102, such as on a server or home computer (not shown).

[0027] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control the power to other components in the WTRU 102. The power source 134 may be any suitable device for providing power to the WTRU 102. For example, the power source 134 may include one or more dry batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0028] 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) regarding the current location of the WTRU 102. In addition to or instead of information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may obtain location information by way of any suitable location-determination method while remaining consistent with an embodiment.

[0029] The processor 118 may be further coupled to other elements 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the elements 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, etc. Element 138 may include one or more sensors, which may be one or more of a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor, a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0030] The WTRU 102 may include a full-duplex radio where transmission and reception of some or all of the signals (e.g., associated with a particular subframe for both the UL (e.g., for transmission) and downlink (e.g., for reception)) may be parallel and / or simultaneous. The full-duplex radio may include an interference management unit to reduce and or substantially eliminate self-interference through hardware (e.g., chokes) or processor-based signal processing (e.g., via a separate processor (not shown) or processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for transmission and reception of either some or all of the signals (e.g., associated with a particular subframe for either the UL (e.g., for transmission) or downlink (e.g., for reception)).

[0031] 1C is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As mentioned above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using E-UTRA radio technology. The RAN 104 may also communicate with the CN 106.

[0032] The RAN 104 may include eNode-Bs 160a, 160b, and 160c, although it will be understood that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, and 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In an embodiment, the eNode-Bs 160a, 160b, and 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0033] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling, etc. in the UL and / or DL. As shown in FIG. 1C, the eNode-Bs 160a, 160b, 160c may communicate with each other via an X2 interface.

[0034] 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. Although each of the foregoing elements is depicted as part of the CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0035] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may function as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, and selecting a particular serving gateway during initial attach of the WTRUs 102a, 102b, 102c. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0036] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to and from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions such as anchoring the user plane during inter-eNode B handovers, triggering paging when DL data is available to the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

[0037] The SGW 164 may be connected to a PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0038] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional landline communications devices. For example, the CN 106 may include or communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. Furthermore, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0039] Although the WTRU is depicted in FIGS. 1A-1D as a wireless terminal, it is contemplated that in certain representative embodiments, such a terminal may use a wired communication interface (e.g., temporarily or permanently) with the communication network.

[0040] In a representative embodiment, the other network 112 may be a WLAN.

[0041] A WLAN in infrastructure Basic Service Set (BSS) mode may have an access point (AP) of the BSS and one or more stations (STAs) associated with the AP. The AP may have access to or interface with a distribution system (DS) or another type of wired / wireless network that carries traffic within and / or outside the BSS. Traffic to a STA originating from outside the BSS may arrive through the AP and be delivered to the STA. Traffic originating from a STA to a destination outside the BSS may be sent to the AP and transmitted to the respective destination. Traffic between STAs within a BSS may be transmitted, for example, through the AP, where the source STA may send traffic to the AP, which may deliver the traffic to the destination STA. Traffic between STAs within a BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic may be transmitted between (e.g., directly between) a source STA and a destination STA via 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 an Independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (e.g., all of the STAs) may communicate directly with each other. The IBSS mode of communication may be referred to herein as an "ad hoc" communication mode.

[0042] When using the 802.11ac infrastructure mode of operation or a similar mode of operation, an AP may transmit beacons on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a width that is dynamically set via signaling. The primary channel may be the operating channel of the BSS and may be used by STAs to establish a connection with the AP. In some representative embodiments, for example, in an 802.11 system, Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) with collision avoidance may be implemented. With CSMA / CA, STAs (e.g., all STAs), including the AP, may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0043] High Throughput (HT) STAs may, for example, use 40 MHz wide channels for communication via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0044] A Very High Throughput (VHT) STA may support channels of 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz width. 40 MHz and / or 80 MHz may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining eight contiguous 20 MHz channels or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, after channel encoding, the data may pass through a segment parser that may split the data into two streams. Inverse Fast Fourier Transform (IFFT) processing and time-domain processing may be performed separately on each stream. The streams may be mapped to two 80 MHz channels, and the data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations described above for the 80+80 configuration may be reversed, and the combined data may be transmitted to the Medium Access Control (MAC).

[0045] Sub-1 GHz operating modes are supported by 802.11af and 802.11ah. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, while 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to representative embodiments, 802.11ah may support meter-type control / machine-type communications (MTC), such as MTC devices in macro coverage areas. MTC devices may have limited capabilities, including, for example, support for (e.g., only support for) specific and / or limited bandwidths. MTC devices may include batteries with above-threshold battery life (e.g., to maintain very long battery life).

[0046] WLAN systems that can support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include a channel that can be designated as a primary channel. The primary channel can have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be configured and / or limited by the STA among all STAs operating in the BSS that support the minimum bandwidth operating mode. In an 802.11ah example, the primary channel can be 1 MHz wide for STAs (e.g., MTC-type devices) that support (e.g., only) the 1 MHz mode, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) configuration can depend on the conditions of the primary channel. For example, if the primary channel is busy due to a STA (that only supports 1 MHz mode of operation) transmitting to the AP, the entire available frequency band may be considered busy, even though most of the frequency band may remain idle and be available for use.

[0047] 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.

[0048] 1D is a system diagram illustrating the RAN 113 and the CN 115 according to one embodiment. As mentioned above, the RAN 113 may communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using NR radio technology. The RAN 113 may also communicate with the CN 115.

[0049] The RAN 113 may include gNBs 180a, 180b, and 180c, although it will be understood that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, and 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In an embodiment, the gNBs 180a, 180b, and 180c may implement MIMO technology. For example, the gNBs 180a, 180b, and 180c may utilize beamforming to transmit and / or receive signals to the WTRUs 102a, 102b, and 102c. Thus, the gNB 180a may, for example, use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a. In one embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers (not shown) to the WTRU 102a. A subset of these component carriers may be on unlicensed spectrum, and the remaining component carriers may be on licensed spectrum. In one embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNBs 180a and 180b (and / or 180c).

[0050] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of different or scalable lengths (e.g., including different numbers of OFDM symbols and / or lasting different lengths of absolute time).

[0051] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c without accessing another RAN (e.g., eNode-Bs 160a, 160b, 160c in FIG. 1C ). In a standalone configuration, the WTRUs 102a, 102b, 102c may utilize one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in unlicensed bands. The non-standalone configured WTRUs 102a, 102b, 102c may communicate with and connect to gNBs 180a, 180b, 180c while also communicating with and connecting to another RAN, such as eNode-Bs 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-Bs 160a, 160b, 160c may act as mobility anchors for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0052] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support for network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data to User Plane Functions (UPFs) 184a, 184b, routing of control plane information to Access and Mobility Management Functions (AMFs) 182a, 182b, etc. As shown in FIG. 1D , the gNBs 180a, 180b, 180c may communicate with each other via an Xn interface.

[0053] 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While each of the foregoing elements is depicted as part of the CN 115, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0054] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may function as a control node. For example, the AMF 182a, 182b may be responsible for user authentication of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selecting a particular SMF 183a, 183b, managing registration areas, terminating NAS signaling, mobility management, etc. Network slicing may be used by the AMF 182a, 182b to customize the CN support of the WTRUs 102a, 102b, 102c based on the type of service utilizing the WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for MTC access, etc. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as WiFi.

[0055] The SMFs 183a, 183b may be connected to the AMFs 182a, 182b in the CN 115 via an N11 interface. The SMFs 183a, 183b may also be connected to the UPFs 184a, 184b in the CN 115 via an N4 interface. The SMFs 183a, 183b may select and control the UPFs 184a, 184b and configure the routing of traffic through the UPFs 184a, 184b. The SMFs 183a, 183b may perform other functions, such as managing and assigning UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0056] The UPFs 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks such as the Internet 110 to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPFs 184, 184b may perform other functions such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, etc.

[0057] The CN 115 may facilitate communication with other networks. For example, the CN 115 may include or communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 115 and the PSTN 108. Additionally, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to local data networks (DNs) 185a, 185b through the UPFs 184a, 184b via an N3 interface to the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b.

[0058] 1A-1D and their corresponding descriptions, one or more or all of the functions described herein with respect to one or more of the WTRUs 102a-d, base stations 114a-b, eNode-Bs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMFs 182a-b, UPFs 184a-b, SMFs 183a-b, DNs 185a-b, and / or any other devices described herein may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation devices may be used to test other devices and / or simulate network and / or WTRU functions.

[0059] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or an 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 communication network to test other devices in the communication 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 communication network. The emulation devices may be directly coupled to another device for testing purposes and / or may perform testing using terrestrial wireless communication.

[0060] One or more emulation devices may perform one or more functions, inclusive, while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in test scenarios in a test lab and / or in an undeployed (e.g., test) wired and / or wireless communication network 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 (which may include, e.g., one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0061] (Detailed explanation) A key challenge for future cellular communications is the need to support trillions of connected, highly mobile devices. While cellular data rates have increased dramatically over the past 30 years (by nearly six orders of magnitude), battery energy density has improved less than tenfold from 1990 to 2015. This poses a significant challenge to scaling to one trillion devices. As an example, assuming one trillion deployed devices, each with a 10-year battery life, would require an average of 274 million battery replacements per day. Furthermore, battery replacement may be difficult, if not impossible, in some cases. Therefore, scaling to one trillion devices may benefit from rethinking the radio transceiver, air interface, and the entire system.

[0062] Key advances that are expected to support this expansion include ultra-low power RF transmitters that can support at least small cell-like link budgets; a zero-energy uplink air interface that is not powered by the device's battery, enabling "perpetual" batteries in the near term and targeting battery-less operation of devices in the long term; and a scalable system framework that can support a variety of deployment scenarios and device types.

[0063] For example, the indirect carrier modulation-based backscatter coupling communication framework used in long-range RFID systems could be useful in integrating a large number of mobile connected devices into mobile communication networks (e.g., future 3GPP and IEEE networks). To this end, ultra-low power transponders for terminal devices, enabling communication distances of tens to hundreds of meters, would be useful. These transponders would support multiple operating modes and dynamically adapt to different operating environments. Such devices would benefit from more advanced coding and modulation schemes (e.g., compared to those currently specified for RFID systems) while being limited in power consumption and cost. Furthermore, these devices would also benefit from being wirelessly powered by the network.

[0064] A somewhat simplified transponder using indirect carrier modulation can include an antenna, an indirect carrier modulator (ICM) with a programmable antenna load and load modulator, a memory module to store the payload, an energy harvester, and a battery (possibly with a level indicator). Data is transmitted over the UL by reflecting an incident wave according to the payload. The antenna load of the ICM can be set to different impedance states, and the antenna load modulator can dynamically set the antenna load according to the specified modulation type and payload.

[0065] The antenna load determines both the transmitted and harvested energy. Let the power of the incident RF signal be P IN If the antenna load is set to a power reflection coefficient of Γ, the harvested power is (1-Γ)P IN λ, where λ<1 is the power conversion efficiency of the energy harvester. The transmitted or reflected energy is IN is.

[0066] Currently deployed indirect carrier modulation transmission systems (e.g., inductively coupled NFC and backscatter coupled RFID) face a constant trade-off between UL throughput and reliability and DL energy harvesting efficiency. Each specified device class is optimized for either DL energy harvesting efficiency (i.e., battery-less passive class devices) or UL throughput and reliability (i.e., semi-passive class devices with on-board batteries). Existing products are designed to support only a single operating class, and all classes support relatively low data rates.

[0067] Inductively coupled indirect carrier modulation transmission In inductively coupled indirect carrier modulation transmission systems (e.g., NFC), there is an inherent trade-off between communication range and throughput: increasing UL throughput by reducing the data symbol duration reduces communication range.

[0068] Increasing the coupling quality factor between the reader and transponder reduces the link bandwidth. This limits the minimum achievable duration of a UL data symbol and therefore the maximum UL throughput, but improves DL power transfer efficiency. Reducing the coupling quality factor to increase the link bandwidth and allow for shorter symbol durations to support higher UL throughput reduces DL power transfer efficiency. In this case, the reader and transponder must be closer to each other to support fully passive or semi-passive operation.

[0069] This trade-off between UL communication range and throughput can be alleviated by using higher-order modulation (e.g., QPSK, 16-QAM). However, in transmission systems employing indirect carrier modulation, enabling higher-order modulation using conventional methods results in a trade-off between throughput and transponder complexity.

[0070] Currently proposed approaches map points from the UL constellation to individual reflection states of the antenna load modulator. This means, for example, that 16 different reflection states are required to support 16-QAM. Because the number of reflection states increases with modulation order, the complexity of the antenna load modulator can become impractical, especially for passive and semi-passive transponders supporting higher-order modulation (e.g., 64-QAM). The complexity of passive and semi-passive transponders must be considered, as it directly impacts the cost of the transponder.

[0071] Backscatter-coupled indirect carrier modulation transmission In a backscatter coupled indirect carrier modulation system, there is an inherent trade-off between reflected power in the UL and harvested power in the DL. The performance of the UL is tied to the DL through the energy harvesting capabilities of the backscatter system (e.g., RFID) which exchanges data in the UL while simultaneously providing power in the DL.

[0072] The choice of UL constellation (number and spacing of constellation points) affects both UL performance (e.g., throughput, BER) and DL power harvesting efficiency. Improving the UL signal-to-noise ratio, and therefore the BER, by increasing the spacing of constellation points reduces DL power harvesting efficiency. Improving UL throughput and spectral efficiency by using higher-order modulation for a specified minimum BER performance also reduces DL power harvesting efficiency.

[0073] For example, many of the emerging ultra-low power use cases envisioned for 5G NR are expected to employ backscatter-coupled indirect carrier modulation transmission in terminal devices. These devices must support multiple operating modes to provide improved data rates and link reliability or long battery life, as needed. Such terminal devices can benefit from improved coding and modulation schemes and constellation adaptation procedures for inductively coupled and backscatter-coupled indirect carrier modulation transmission systems.

[0074] Constellation Adaptation In an indirect carrier modulation (ICM) transmission system, the performance of the UL is tied to the DL through energy harvesting. For example, a backscatter transponder (e.g., RFID) transmits data on the UL while simultaneously harvesting energy on the DL using the same RF carrier. Two commonly used first-order indirect carrier modulation schemes and associated two-point constellations are shown in Figures 2A and 2B, respectively. The constellation in Figure 2A utilizes on-off keying (OOK) with the ICM's zero-reflection (100% absorption) state S0 and zero-absorption (100% reflection) state S1 as the constellation points, while the constellation in Figure 2B utilizes binary phase-shift keying (BPSK) with two zero-absorption (100% reflection) states S1 and S2. The approach in Figure 2B has 0% DL energy harvesting efficiency but transmits higher energy per symbol on the UL compared to the approach in Figure 2A. On the other hand, the approach in Figure 2A has better DL energy harvesting efficiency but transmits lower energy per symbol on the UL.

[0075] Figures 3A and 3B show two examples of secondary indirect carrier modulation schemes and associated four-point constellations. The constellation in Figure 3A utilizes quadrature phase-shift keying (QPSK) with four states S1 to S4, while the constellation in Figure 3B utilizes four-point quadrature amplitude modulation (4-QAM) with the zero-reflection (100% absorption) state S0 of the ICM as a point in the constellation. If the vector distance r of the return loss circle between the constellation points is held constant, the scheme in Figure 3A can transmit higher energy per bit and ensure a relatively large minimum spacing between constellation points, while the scheme in Figure 3B can provide better DL energy harvesting efficiency but requires a relatively small minimum spacing between constellation points.

[0076] In one embodiment of the present principles, the WTRU may use an adaptive method that can select the placement of constellation points for a given modulation order.

[0077] In such an adaptive method, the WTRU can adapt a signal constellation for a specified uplink modulation order. The UE can meet DL power reception requirements by utilizing an ICM zero reflection state (i.e., transmit muting) as a point in the UL signal constellation. The UE can increase UL reliability by increasing the radius of a return loss circle that includes an ICM reflection state that represents a point in the UL signal constellation. The WTRU can also perform signal constellation adaptation based on the combined requirements of energy harvesting and payload reliability requirements for UL transmissions, and can further select an uplink signal constellation configuration based on, for example, at least one of a current battery level indicator, downlink power reception efficiency, and uplink payload reliability.

[0078] The trade-off between energy harvesting and UL reliability can be achieved by determining the placement of constellation points for a corresponding modulation order (i.e., a specific number of constellation points). The device can perform automatic constellation adaptation, triggered by, for example, a data retransmission request from the network, as described below.

[0079] 14 shows an example of a possible transmission method 1400, in accordance with an embodiment of the present principles. In this example, a network 1402 and a WTRU 1404 are in communication.

[0080] In step S1401, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU reflects a capability report back to the network, including, for example, a list of supported constellation constellations for each supported modulation order.

[0081] In step S1403, the network sends a modulated transmission to the WTRU that includes a WTRU configuration with priorities for at least a portion of the list of supported constellations.

[0082] In step S1405, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU uses the highest priority constellation for that modulation order when reflecting the data.

[0083] In step S1407, the network sends a modulated transmission including the first retransmission request to the WTRU.

[0084] In step S1409, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU uses the next (i.e., second) highest priority constellation for that modulation order when reflecting the data for retransmission.

[0085] In step S1411, the network sends a modulated transmission including a second retransmission request to the WTRU.

[0086] In step S1413, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU uses the next (i.e., third) highest priority constellation for that modulation order when reflecting the data for retransmission.

[0087] In one embodiment, a device may report a list of supported constellation constellations for each supported modulation order using a pre-specified or pre-configured modulation type and modulation order with a pre-specified or pre-configured placement of points in the constellation. As an example, a device may report a list of supported constellation constellations for each supported modulation using the standard constellation for OOK modulation shown in FIG. 2A. As a further example, a list of constellation constellations supported by a device for, for example, a second modulation including the standard constellation for QPSK is shown in FIG. 3A, and a second constellation utilizing a zero-reflection state (S0) is shown in FIG. 3B.

[0088] In another embodiment, the device receives a configuration including a priority or ranking for the list of reported constellation configurations for each reported modulation order. For example, the default constellation type (e.g., highest priority) for a battery-less passive device may be the constellation type that provides the highest supported DL energy harvesting efficiency. An example of a default constellation type for a secondary modulation is the constellation utilizing the zero reflection state (S0) shown in FIG. 3B. For example, the lowest priority constellation for a battery-less passive device may be the constellation that provides the highest UL transmission energy per bit for a given modulation order. An example of the lowest priority constellation type for a secondary modulation is the standard constellation for QPSK shown in FIG. 3A.

[0089] In one embodiment, the device transmitting data uses the highest priority constellation that provides the highest supported DL energy harvesting efficiency.

[0090] In one embodiment, the device receives a data retransmission request from the network or fails to receive an ACK within a pre-specified time window for a specified, signaled, or pre-configured consecutive number of times.

[0091] In one embodiment, when a device receives a data retransmission request from the network, it switches to the next configured constellation and modulation type on the priority list to retransmit the data.

[0092] In one embodiment, the device continues transmitting data using the selected constellation and modulation type unless it receives additional data retransmission requests from the network. Otherwise, the device selects the next configured constellation and modulation type on the priority list to retransmit the data. The device can repeat this process until it has exhausted the constellations on the priority list or reached a signaled or preset total number of retransmissions, at which point the device can declare a failure of the data transmission / connection.

[0093] Next, the following embodiments describe a network-assisted procedure in which the WTRU has full control over which constellation constellation to use for a given modulation order, assuming that the network can blindly detect which transmission configuration is used for data transmission by the WTRU.

[0094] FIG. 15 shows an example of a possible transmission method 1500, in accordance with an embodiment of the present principles. In this example, a network 1502 and a WTRU 1504 are in communication.

[0095] In step S1501, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU reflects a capability report back to the network, including, for example, a list of supported constellation constellations for each supported modulation order.

[0096] In step S1503, the network sends a modulated transmission to the WTRU that includes a Channel-Quality Indicator (CQI) mapping that includes a mapping between CQI values and supported constellation constellations in the reported list.

[0097] In step S1505, the network sends a modulated transmission to the WTRU that includes a unique ID and a CQI measurement assistance configuration that includes the unique ID transmission opportunity (e.g., timing and frequency configuration). The unique ID is utilized for transmissions by the device and enables the network to identify the transmitting device and measure the channel quality associated with the transmitting device.

[0098] In step S1507, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU reflects a unique ID transmission back to the network.

[0099] In step S1509, the network sends a modulated transmission including the CQI measurement report to the WTRU.

[0100] In step S1511, the WTRU selects a constellation arrangement based on the CQI value reported by the network and the configured CQI mapping.

[0101] In step S1513, the network sends an unmodulated (CW) transmission to the WTRU, which reflects the data back to the network using the selected constellation.

[0102] In one embodiment, the WTRU reports a list of supported constellation constellations for each supported modulation order using a pre-specified or pre-configured modulation type and modulation order with a pre-specified or pre-configured placement of the points of the constellation. As an example, the WTRU may report a list of supported constellation constellations for each supported modulation using the standard constellation for OOK modulation shown in Figure 2A. As a further example, a list of constellation constellations supported by the WTRU for, e.g., a secondary modulation, may include the standard constellation for QPSK shown in Figure 3A and a second constellation utilizing the zero reflection state (S0) shown in Figure 3B.

[0103] In one embodiment, the WTRU receives a mapping between channel quality indicator (CQI) values and a list of reported constellation constellations for each reported modulation order.

[0104] In one embodiment, the WTRU receives a CQI measurement support configuration, eg, a unique ID, a periodicity of the unique ID transmission opportunity.

[0105] In one embodiment, the WTRU periodically transmits a configured unique ID using the signaled modulation type / modulation order and constellation / symbol configuration to facilitate CQI measurements by the network.

[0106] In one embodiment, the WTRU periodically or Q i is related

[0107]

number

[0108] In one embodiment, the WTRU selects a constellation constellation from a pre-configured list based on the CQI value reported by the network and a pre-configured mapping.

[0109] In one embodiment, the WTRU continues transmitting data using the selected new constellation and modulation order.

[0110] In the following embodiment, a fully autonomous procedure is described in which the WTRU performs constellation adaptation based on an evaluation of the performance metrics.

[0111] FIG. 16 shows an example of a possible transmission method 1600, in accordance with an embodiment of the present principles. In this example, it is assumed that the network 1602 and the WTRU 1604 are in communication and that the network can blindly detect which transmission configuration is used for data transmission by the WTRU.

[0112] In step S1601, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU reflects a capability report back to the network, including, for example, a list of supported constellation constellations for each supported modulation order.

[0113] In step S1603, the network sends a modulated transmission to the WTRU including a Received Interrogation Signal Strength (RISS) Measurement Assistance Setup message that includes a CW transmission opportunity to enable RISS measurements.

[0114] In step S1605, the network sends an unmodulated (CW) transmission to the WTRU, which reflects the data back to the network.

[0115] In step S1607, the network sends an unmodulated transmission to the WTRU as announced in the RISS Measurement Assistance Setup message.

[0116] In step S1609, the WTRU measures its DL energy harvesting efficiency η.

[0117] In step S1611, the network sends a modulated transmission containing a retransmission request to the WTRU.

[0118] In step S1613, the WTRU receives a performance metric, e.g.

[0119]

number

[0120] In step S1615, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU reflects a transmission adaptation indication to the network using a pre-configured or pre-specified modulation type.

[0121] In step S1617, the network sends an unmodulated (CW) transmission to the WTRU, which reflects the data back to the network using the newly selected constellation.

[0122] In one embodiment, the WTRU reports a list of supported constellation constellations for each supported modulation order using a pre-specified or pre-configured modulation type and modulation order with a pre-specified or pre-configured placement of the points of the constellation. As an example, the WTRU reports a list of supported constellation constellations for each supported modulation using the standard constellation for OOK modulation shown in Figure 2A. As a further example, a list of constellation constellations supported by the device for, for example, a secondary modulation includes the standard constellation for QPSK shown in Figure 3A and a second constellation utilizing the zero reflection state (S0) shown in Figure 3B.

[0123] In one embodiment, the WTRU receives a set of opportunities for measuring received interrogation signal strength (RISS).

[0124] In one embodiment, the WTRU receives a CW transmission from the network, measures the RISS over one or more measurement occasions, and determines the DL energy harvesting efficiency (η) associated with the current UL transmission configuration.

[0125] In one embodiment, the WTRU receives a data retransmission request from the network or a notification from the PMU.

[0126] In one embodiment, the WTRU may H -E TX )={ηRISS-P ICM}(N / R)>δ and E TX Select a new constellation from the list of pre-specified UL constellation constellations such that P ICM is the power consumption of the ICM when configured for the new constellation, N is the UL data packet size, R is the UL data rate, and E TX is the UL transmit energy per symbol, and δ, Δ are optimization targets that may be pre-configured in the WTRU or signaled by the network as part of the trigger criteria.

[0127] In one embodiment, the WTRU transmits a UL Transmission Adaptation Notification message indicating the newly selected transmission configuration to be used in subsequent UL data packets using a pre-specified / pre-configured modulation type and modulation order with a pre-specified / pre-configured placement of points in the constellation. Assuming that the network can blindly detect which transmission configuration has been used for data transmission by the WTRU, this embodiment may be omitted in the sequence of steps performed by the WTRU as shown in FIG. 15.

[0128] In one embodiment, the WTRU transmits the UL data packet using a new transmission configuration that includes a new constellation arrangement.

[0129] Hybrid Phase-Amplitude Indirect Carrier Modulation In an indirect carrier modulation transmission system, the performance of the UL is tied to the DL through energy harvesting. For example, a backscatter transponder (e.g., RFID) transmits data on the UL while simultaneously harvesting energy on the DL using the same RF carrier. Figures 4A and 4B show the ICM state transitions and transmit waveforms associated with the commonly used Manchester-coded on-off keying (OOK) indirect carrier modulation scheme. The scheme shown is used to transmit one bit per symbol. This scheme employs a 50% duty cycle factor and divides the symbol period into two equal sections. When transmitting a "0," the ICM remains in the reflective state S1 for the first half of the symbol and transitions to the zero-reflective state S0 for the second half of the symbol. When transmitting a "1," the ICM state transitions are reversed, as shown on the right.

[0130] The DL energy harvesting efficiency is defined as the fraction of incident RF energy that is harvested and stored in the transponder's battery. The normalized energy harvesting efficiency of DL is η = E H / E0, where E0 is the available incident energy and E H is the harvested energy. Harvested energy E H is defined as follows:

[0131]

number

[0132] T is the symbol duration and Γ k is the power reflection coefficient associated with the ICM state used to represent each symbol. Note that in the example shown in FIG. 4A, Γ=0 for S0, Γ=1 for S1, and E H =TP IN / 2. E0 is calculated assuming that the ICM remains in state S0 (Γ=0) for the entire duration T, so E0=TP INand the normalized energy harvesting efficiency η = 50%. Using a similar approach, the transmitted energy per symbol E TX can be obtained and is defined as follows:

[0133]

number

[0134] In the example shown in Figure 4A, Γ = 0 for S0, Γ = 1 for S1, and E TX =TP IN / 2. The gNB receiver decoder uses a data slicer that includes a carrier threshold detector. Because the bit duration and duty cycle factor are specified by the standard, the gNB receiver decoder knows the sampling positions of the received waveform.

[0135] 5A and 5B show another example of a Manchester coded indirect carrier modulation scheme employing binary phase shift keying (BPSK) to transmit one bit per symbol. This scheme employs a 50% duty cycle factor and divides the symbol period into two equal sections. When transmitting a "0", the ICM is in state S1 during the first half of the symbol and transitions to state S2 during the second half of the symbol. When transmitting a "1", the ICM state transitions are reversed, as shown in Figures 5A and 5B. Note that in the example shown in Figure 5A, Γ = 1 for both S1 and S2. Therefore, the harvested energy E H = 0, the normalized energy harvesting efficiency η = 0 and all incident RF energy is reflected, so E TX =TP IN The gNB receiver decoder uses a phase discriminator. Because the bit duration and duty cycle coefficients are specified by the standard, the gNB receiver decoder knows where the phase transitions are in the received waveform.

[0136] In comparison, the coded indirect carrier modulation scheme shown in Figures 4A and 4B employing OOK provides better energy harvesting efficiency, while the scheme shown in Figures 5A and 5B employing BPSK provides higher transmission energy per bit. This represents a certain trade-off between DL energy harvesting efficiency and UL reliability. Thus, a flexible coded modulation scheme that can provide additional degrees of freedom may be desired so that the trade-off between DL energy harvesting and UL reliability can be made according to the requirements of different use cases and deployment scenarios.

[0137] 6A and 6B illustrate a hybrid phase-amplitude indirect carrier modulation scheme in accordance with an embodiment of the present principles. The illustrated scheme is for transmitting one bit per symbol.

[0138] Generally, such a hybrid phase-amplitude indirect carrier modulation scheme can be achieved by using hybrid phase-amplitude indirect RF carrier modulation, in which the UE has two degrees of freedom for coded data transmission, which can be the duty cycle coefficient and modulation depth. The UE can use carrier amplitude and carrier phase variations to encode data symbols and symbol boundaries. The ICM states can be arranged into two sets of antipodal reflection states {S1, S2} and {S3, S4}, where the first symbol can be coded using the duty cycle coefficient and the transition from state S4 to S1, and the second symbol can be coded using the duty cycle coefficient and the transition from state S2 to S3.

[0139] As mentioned before, one of the degrees of freedom is the configurable duty cycle factor ξ, where 0<ξ<1. This means that the data symbol is divided into two parts, ξT and (1-ξ)T. When transmitting a "0", the ICM stays in state S4 for the first ξT part of the symbol and transitions to state S1 for the remaining (1-ξ)T part of the symbol. When the ICM transmits a "1", it remains in state S2 for the first (1-ξ)T portion of the symbol and transitions to state S3 for the remaining ξT portion of the symbol, although it should be understood that the significance of the state transitions may be different, e.g., reversed.

[0140] States S1 and S2 have the same power reflection coefficient Γ 1,2 can be implemented, and states S3 and S4 have the same power reflection coefficient Γ 3,4 Note that the reflected waveforms associated with states S1 and S2 have a 180 degree phase difference, and similarly the reflected waveforms associated with states S3 and S4 have a 180 degree phase difference. The modulation depth δ is the sum of the two power reflection coefficients Γ 1,2 and Г 3,4 Specifically, δ = Γ 1,2 / Г 3,4 is defined as:

[0141] The normalized energy harvesting efficiency of DL is η = E H / E0, where E0=TP IN is the available incident energy, E H is the harvested energy. Harvested energy E H is as follows:

[0142]

number

[0143]

number

[0144]

number

[0145] In the example shown in Figure 6A, Γ 1,2 = 1 / 2, ξ = 0.25, the transmitted energy per symbol is

[0146]

number

[0147] Based on the UL transmission reliability and power harvesting requirements, the duty cycle factor ξ and modulation depth δ can be selected as follows:

[0148] The DL energy harvesting efficiency can be improved by decreasing the duty cycle factor and increasing the modulation depth.

[0149] The UL reliability (ie, transmitted energy per bit) can be improved by increasing the duty cycle factor and decreasing the modulation depth.

[0150] Figures 7A and 7B show a decoding scheme for hybrid phase-amplitude indirect carrier modulation transmission, in accordance with an embodiment of the present principles. Figure 7A shows a transmit waveform similar to Figure 6B, and Figure 7B shows the output waveform of a receiver decoder employing an amplitude detector and a phase detector.

[0151] The WTRU may use a data slicer (e.g., an amplitude detector) that includes a carrier threshold detector and a phase detector to detect boundaries between and within data symbols. The standard may specify allowable settings for the duty cycle factor ξ and modulation depth δ so that the UE knows how to set the data slicer threshold and where to sample the data slicer output.

[0152] The trade-off between energy harvesting and UL reliability can be achieved by determining an appropriate combination of values for the parameter pair {ξ, δ}, which describes the modulation scheme and includes the duty cycle factor ξ and the modulation depth δ. The WTRU can use the following embodiments to perform automatic constellation adaptation triggered by, for example, a data retransmission request from the network.

[0153] FIG. 17 shows an example of a possible transmission method 1700, in accordance with an embodiment of the present principles. In this example, a network 1702 and a WTRU 1704 are in communication.

[0154] In step S1701, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU reflects a capability report back to the network, including, for example, a list of supported duty cycle factors ξ and modulation indices δ.

[0155] In step S1703, the network sends a modulated transmission to the WTRU that includes a WTRU configuration with priorities for at least a portion of the list of supported values of the parameter pair {ξ, δ}.

[0156] In step S1705, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU uses the highest priority setting of the parameter pair {ξ, δ} when reflecting the data.

[0157] In step S1707, the network sends a modulated transmission including the first retransmission request to the WTRU.

[0158] In step S1709, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU uses the next (ie, second) highest priority setting of the parameter pair {ξ, δ} when reflecting the data for retransmission.

[0159] In step S1711, the network sends a modulated transmission including a second retransmission request to the WTRU.

[0160] In step S1713, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU uses the next (ie, third) highest priority setting of the parameter pair {ξ, δ} when reflecting the data for retransmission.

[0161] In one embodiment, the WTRU utilizes a pre-specified / pre-configured modulation type to report a list of supported duty cycle factors ξ and modulation depths δ for hybrid phase-amplitude indirect carrier modulation.

[0162] In one embodiment, the WTRU receives a priority or ranking for the reported list of supported values of the parameter pair {ξ, δ}, e.g., a default (highest priority) set of values for the parameter pair {ξ, δ} for a passive device is one that provides the highest supported DL energy harvesting efficiency, e.g., the default (highest priority) value for the parameter pair {ξ, δ} is the lowest supported duty cycle factor and the highest supported modulation index for optimizing DL energy harvesting. For example, a lowest priority set of values for the parameter pair {ξ, δ} for a passive device is one that provides the highest UL transmit energy per bit, e.g., the lowest priority value for the parameter pair {ξ, δ} is the highest supported duty cycle factor and the lowest supported modulation index for optimizing UL reliability (transmit energy per bit).

[0163] In one embodiment, the WTRU initiates data transmission using the default (highest priority) setting of the parameter pair {ξ, δ}.

[0164] In one embodiment, the WTRU receives a data retransmission request or fails to receive an ACK within a pre-specified time window for a specified, signaled, or pre-configured number of consecutive times.

[0165] In one embodiment, the WTRU switches to the next configured setting of the parameter pair {ξ, δ} on the priority list and retransmits the data.

[0166] In one embodiment, the WTRU continues transmitting data using the selected new setting of the parameter pair {ξ, δ} unless it receives additional data retransmission requests from the network. Otherwise, the device selects the next configured value for the parameter pair {ξ, δ} on the priority list and retransmits the data. The WTRU continues this process until it exhausts the constellations in the priority list or reaches a signaled or preconfigured total number of retransmissions, after which the WTRU declares a failure of the data transmission / connection.

[0167] In the following embodiments, a network-assisted procedure is described in which the WTRU has full control over which values of the parameter pair {ξ, δ} to use, assuming that the network can blindly detect which transmission configuration has been utilized for data transmission by the WTRU.

[0168] FIG. 18 shows an example of a possible transmission method 1800, in accordance with an embodiment of the present principles. In this example, a network 1802 and a WTRU 1804 are in communication.

[0169] In step S1801, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU reflects a capability report back to the network, including, for example, a list of supported duty cycle factors ξ and modulation indices δ.

[0170] In step S1803, the network sends a modulated transmission to the WTRU that includes a channel quality indicator (CQI) mapping that includes a mapping between a CQI value and at least a portion of a list of supported values for the parameter pair {ξ, δ}.

[0171] In step S1805, the network sends a modulated transmission to the WTRU that includes a unique ID and a CQI measurement assistance configuration that includes the unique ID transmission opportunity (e.g., timing and frequency configuration). The unique ID is utilized for transmissions by the device and enables the network to identify the transmitting device and measure the channel quality associated with the transmitting device.

[0172] In step S1807, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU reflects a unique ID transmission back to the network.

[0173] In step S1809, the network sends a modulated transmission including the CQI measurement report to the WTRU.

[0174] In step S1811, the WTRU selects a parameter pair {ξ, δ} based on the CQI value reported by the network and the configured CQI mapping.

[0175] In step S1813, the network sends an unmodulated (CW) transmission to the WTRU, which reflects the data back to the network using the selected parameter pair {ξ, δ}.

[0176] In one embodiment, the WTRU utilizes a pre-specified / pre-configured modulation type to report a list of supported duty cycle factors ξ and modulation depths δ for hybrid phase-amplitude indirect carrier modulation.

[0177] In one embodiment, the WTRU receives a mapping between CQI values and a list of reported values of the parameter pair {ξ, δ}.

[0178] In one embodiment, the WTRU receives a CQI measurement support configuration, eg, a unique ID, a periodicity of the unique ID transmission opportunity.

[0179] In one embodiment, the WTRU periodically transmits a configured unique ID using the signaled modulation type / modulation order and constellation / symbol configuration to facilitate CQI measurements by the network.

[0180] In one embodiment, the WTRU periodically or Q i The following relationship exists:

[0181]

number

[0182] In one embodiment, the WTRU selects the value of the parameter pair {ξ, δ} from the reported list in the first embodiment based on the CQI value reported by the network and a received pre-configured mapping between the CQI value and the list of reported values for the parameter pair {ξ, δ}.

[0183] In one embodiment, the WTRU continues data transmission using the selected new values of the parameter pair {ξ, δ}.

[0184] In the following embodiment, a fully autonomous procedure is described in which the WTRU performs constellation adaptation based on an evaluation of the performance metrics.

[0185] FIG. 19 shows an example of a possible transmission method 1900, in accordance with an embodiment of the present principles. In this example, it is assumed that the network 1902 and the WTRU 1904 are in communication and that the network can blindly detect which transmission configuration is used for data transmission by the WTRU.

[0186] In step S1901, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU reflects a capability report back to the network, including, for example, a list of supported duty cycle factors ξ and modulation indices δ.

[0187] In step S1903, the network sends a modulated transmission to the WTRU including a RISS (Received Inquiry Signal Strength) Measurement Assistance Setup message that includes a CW transmission opportunity to enable RISS measurements.

[0188] In step S1905, the network sends an unmodulated (CW) transmission to the WTRU, which reflects the data back to the network.

[0189] In step S1907, the network sends an unmodulated transmission to the WTRU as announced in the RISS Measurement Assistance Setup message.

[0190] In step S1909, the WTRU measures its DL energy harvesting efficiency η.

[0191] In step S1911, the network sends a modulated transmission containing a retransmission request to the WTRU.

[0192] In step S1913, the WTRU receives a performance metric, e.g.

[0193]

number

[0194] In step S1915, the network sends an unmodulated (CW) transmission to the WTRU, and the WTRU reflects a transmission adaptation indication to the network using a pre-configured or pre-specified modulation type.

[0195] In step S1917, the network sends an unmodulated (CW) transmission to the WTRU, which reflects the data back to the network using the newly selected constellation.

[0196] In one embodiment, the WTRU utilizes a pre-specified / pre-configured modulation type to report a list of supported duty cycle factors ξ and modulation depths δ for hybrid phase-amplitude indirect carrier modulation.

[0197] In one embodiment, the WTRU receives a set of opportunities for measuring received interrogation signal strength (RISS).

[0198] In one embodiment, the WTRU receives a CW transmission from the network, measures the RISS over one or more measurement occasions, and determines the DL energy harvesting efficiency (η) associated with the current UL transmission configuration.

[0199] In one embodiment, the WTRU receives a data retransmission request from the network or a notification from the PMU.

[0200] In one embodiment, the WTRU may H -E TX )={ηRISS-P ICM}(N / R)>δ and E TX Select new values for the parameter pair {ξ, δ} from the list reported in the first embodiment so that P ICM is the power consumption of the ICM when configured for the new constellation, N is the UL data packet size, R is the UL data rate, and E TX is the UL transmit energy per symbol, and δ, Δ are optimization targets that may be pre-configured in the UE or signaled by the network as part of the trigger criteria.

[0201] In one embodiment, the WTRU transmits a Transmission Adaptation Notification message indicating the newly selected transmission configuration to be used in subsequent UL data packets using a pre-specified / pre-configured modulation type and modulation order with a pre-specified / pre-configured placement of points in the constellation. This embodiment may be omitted in the sequence of steps performed by the WTRU shown in Figure 19 if it is assumed that the network can blindly detect which transmission configuration has been used for data transmission by the UE.

[0202] In one embodiment, the WTRU transmits the UL data packet using a new transmission configuration that includes a new set of values for the parameter pair {ξ, δ}.

[0203] Sparse Block Code Based Indirect Carrier Modulation In ICM transmission systems, UL performance is tied to DL through energy harvesting capabilities. For example, a backscatter transponder (e.g., RFID) transmits data in the UL while simultaneously harvesting energy in the DL using the same RF carrier. The use of sparse block codes in the UL can improve DL energy harvesting efficiency if transmit muting is used to represent "0" entries in the code.

[0204] 8A-8C show an example of a sparse block code (FIG. 8A) and an associated carrier modulation scheme, where n bits of data are packed into each symbol, and each symbol has N=2 n In Figure 8A, n=2 and N=4. The code representing each data symbol contains only one non-zero entry.

[0205] A rough description of the ICM state transitions associated with the code sequences is shown in Figure 8B. A "0" entry in the code is represented by setting the ICM to state S0. As shown in Figure 8B, when the ICM is set to state S0, the load applied to the antenna can be set to match the antenna impedance (e.g., 50 ohms). When the ICM is in state S0, the RF carrier can be completely absorbed. Therefore, during the transmission of a "0" entry in the code, all or most of the incident RF energy can be absorbed, resulting in maximum DL energy harvesting efficiency, referred to as transmit muting. The ICM transitions, for example, from state S0 to state S1 when transmitting a "1" entry in the code. State S1 in FIG. 8B represents a short circuit, and therefore the incident RF energy is reflected. Therefore, during the transmission of a "1" entry in the code, all of the incident RF energy can be reflected, resulting in maximum transmission energy.

[0206] Figure 8C shows the time-domain description of the transmit waveform corresponding to each of the {n=2,N=4} sparse block codes. DL energy harvesting efficiency is defined as the fraction of the incident RF energy that is harvested and stored in the transponder battery. The normalized energy harvesting efficiency of DL is η = E H / E0, where E0 is the available incident energy, E H is the harvested energy. Harvested energy E H is as follows:

[0207]

number

[0208]

number

[0209] In the example shown in FIG. 8B, Γ=0 for S0, Γ=1 for S1, and E TX =T C P IN is.

[0210] Two alternative embodiments of the sparse block coding scheme are shown in Figures 20A and 20B. Figure 20A shows the DL energy harvesting efficiency η = 75% and the transmitted UL energy per symbol E TX =T C P IN Figure 20B shows a code that implements maximal sparsity (code rate = 1 / 2) that provides a DL energy harvesting efficiency η = 60% and a transmitted UL energy per symbol E TX =(2 / 5)T C P IN 1 shows a rate 2 / 5 sparse block code that provides

[0211] Indirect carrier modulated transmission may require flexible coding schemes that introduce multiple degrees of freedom to allow a trade-off between DL energy harvesting and UL reliability depending on the requirements of different use cases and deployment scenarios. Below we provide a rough outline of how this trade-off can be achieved using sparse block codes.

[0212] A device may increase the sparseness level, or equivalently the rate, of a sparse block code to increase DL energy harvesting efficiency.

[0213] Conversely, a device can increase the transmitted energy per UL symbol, and therefore the UL reliability, by decreasing the sparseness level, or equivalently the rate, of the sparse block code.

[0214] The reliability of UL employing sparse block code-based ICM transmission can be improved by introducing additional degrees of freedom into the sparse block code-based indirect carrier modulation scheme. Figures 9A-9C illustrate a sparse block code in accordance with one embodiment of the present principles. Figure 9A illustrates the coding scheme, and Figure 9 illustrates the ICM state transitions.

[0215] Generally, according to this embodiment, the UE uses phase reversals of the RF carrier to represent non-zero entries of the sparse block code and transitions between antipodal reflection state pairs {S1, S2} of the ICM to transmit phase reversals in the data encoding sequence. By mapping the antipodal reflection states of the ICM to open and short terminations of the antenna, transmission reliability can be improved. The UE can use one of the reflection states from the antipodal pair to transmit a reference phase for phase-coherent indirect carrier modulation transmissions and can use directional transitions between the antipodal reflection state pairs {S1, S2} to indicate changes in phase reversal direction.

[0216] A "0" entry of the code can be represented by setting the ICM to state S0. When transmitting a "1" entry of the code, the ICM can transition from state S0 to state S1 and then to state S2. State S1 in FIG. 9B can represent a short circuit, and state S2 can represent an open circuit. Both states S1 and S2 can reflect all of the incident RF energy, but the transition from state S1 to state S2 results in a carrier phase reversal. FIG. 9C shows a time-domain description of the transmit waveform corresponding to each of the {n=2, N=4} sparse block codes.

[0217] In the first-order case, the harvesting efficiency η and the transmitted energy per symbol E TX Note that is the same for the two approaches described in Figures 8A-8C and 9A-9C. However, the transmission scheme described in Figures 9A-9C can improve UL reliability by introducing an additional degree of freedom by introducing a phase reversal in the middle of the sinusoidal packet representing a "1" entry of the sparse block code. The UE can then use a decoder that employs both an amplitude detector and a phase detector. Because the load modulator in the UE transponder performs three antenna load state transitions instead of two while transmitting a "1" entry of the sparse block code, power consumption is expected to increase, which may slightly reduce the overall energy efficiency of the UE.

[0218] High-Density Block Code-Based Indirect Carrier Modulation In an indirect carrier modulation transmission system, the performance of the UL is tied to the DL through energy harvesting. For example, a backscatter transponder (e.g., RFID) transmits data on the UL while simultaneously harvesting energy on the DL using the same RF carrier. Using a high-density block code, in which a fully reflective state (e.g., S1 in Figure 21B, which illustrates the ICM state transitions) is used to represent a "1" entry in the high-density block code, can improve the reliability of the UL by increasing the transmitted energy per symbol. An example of a high-density block code and associated carrier modulation scheme is shown in Figures 21A and 21B, where n bits of data are packed into each symbol, and each symbol is represented by a sequence of N=2n code bits. In Figure 21A, n=2 and N=4. The code representing each data symbol contains only one zero entry.

[0219] A general description of the ICM state transitions associated with a code sequence is shown in Figure 21B. A "0" entry in the code is represented by setting the ICM to state S0. As shown in Figure 6.4-1(b), when the ICM is set to state S0, the load applied to the antenna is set to match the antenna impedance (e.g., 50 ohms). When the ICM is in state S0, the RF carrier is completely absorbed. Therefore, during the transmission of a "0" entry in the code, all or most of the incident RF energy is absorbed. The ICM transitions, for example, from state S0 to state S1 when transmitting a "1" entry in the code. State S1 in Figure 21B represents a short circuit, and therefore all of the incident RF energy is reflected. Therefore, during the transmission of a "1" entry in the code, all of the incident RF energy is reflected, resulting in maximum transmitted energy.

[0220] The time domain description of the transmitted waveform corresponding to each of the {n=2, N=4} high density block codes is shown in Figure 22. The DL energy harvesting efficiency is defined as the fraction of the incident RF energy that is harvested and stored in the transponder battery. The normalized energy harvesting efficiency of DL is η = E H / E0, where E0 is the available incident energy, E H is the harvested energy. Harvested energy E H is defined as follows:

[0221]

number

[0222] T C is the duration of each element of the dense block code, and Γ k is the power reflection coefficient associated with the ICM state used to represent each code entry. For the example shown in FIG. 21B, Γ=0 for S0, Γ=1 for S1, and E H =T C P IN E0 is calculated assuming that the ICM remains in state S0 (Γ=0) for all four code entries, so E0=4T C P IN and the normalized energy harvesting efficiency η = 25%. Using a similar approach, the transmitted energy per symbol E TX can be found as follows:

[0223]

number

[0224] In the example shown in FIG. 21B, Γ=0 for S0, Γ=1 for S1, and E TX =(3 / 4)T C P IN is.

[0225] Two alternative embodiments of the high-density block coding scheme are shown in Figures 23A and 23B. Figure 23A shows the DL energy harvesting efficiency η = 25% and the transmitted UL energy per symbol E TX =(3 / 4)T C P INFigure 23B shows a code that implements maximum density (code rate = 1 / 2) that provides a DL energy harvesting efficiency η = 40% and a transmitted UL energy per symbol E TX =(3 / 5)T C P IN 1 shows a rate=2 / 5 dense block code that provides

[0226] Indirect carrier modulated transmission may require flexible coding schemes that introduce multiple degrees of freedom to allow a trade-off between DL energy harvesting and UL reliability depending on the requirements of different use cases and deployment scenarios. Below we provide a rough outline of how this trade-off can be achieved using high-density block codes.

[0227] A device can increase the density level, or equivalently the rate, of a high-density block code to increase the transmitted energy per UL symbol and therefore the UL reliability. Conversely, a device can decrease the density level, or equivalently the rate, of a high-density block code to improve DL energy harvesting efficiency.

[0228] UE Procedures As previously described, a UE can simultaneously receive power and transmit information on the same RF carrier. In an ICM transmission system, the UE can operate to simultaneously enable efficient DL energy harvesting (EH) and reliable UL data transmission. A desired tradeoff between EH and UL reliability can be achieved by determining a constellation type (e.g., ICM, hybrid phase-amplitude ICM, sparse block code ICM, dense block code ICM) for a corresponding modulation order (i.e., a specific number of constellation points) and selecting a constellation / symbol configuration that optimizes DL EH efficiency for a specified UL transmission reliability. This can be broadly network-controlled or UE-controlled.

[0229] In an embodiment of a method 1000 according to the present principles shown in FIG. 10, the UE may perform constellation adaptation after a data retransmission request from the network.

[0230] In step S1002, the UE uses the required standardized modulation type / modulation order with a specific constellation / symbol configuration to report a list of supported class(es) or supported modulation type(s) / modulation order(s) and the corresponding constellation / symbol configuration to the network.

[0231] In step S1004, the UE receives a priority or ranking (per modulation order) for the list of reported modulation and constellation configurations, where the default constellation type (i.e., with the highest priority) is the one that offers the highest supported DL energy harvesting efficiency, and the lowest priority constellation is the one that offers the highest UL transmission energy per bit for a given modulation order.

[0232] In step S1006, the UE transmits data using the highest priority constellation that provides the highest supported DL energy harvesting efficiency.

[0233] In step S1008, the UE receives a data retransmission request or fails to receive an ACK within a pre-specified time window for a specified signaling / pre-configured number of consecutive times.

[0234] In step S1010, the UE switches to the next configured constellation and modulation type on the priority list and retransmits the data.

[0235] In step S1012, the UE continues transmitting data using the selected constellation and modulation type as long as it does not receive a retransmission request or receives an ACK (see step S1008), otherwise the UE repeats step S1010 until it has exhausted the constellations on its priority list or reached the signaled / preconfigured total number of retransmissions, at which point the UE declares a failure of the data transmission / connection.

[0236] The default (i.e., highest priority) constellation configuration in step S1004 may utilize ICM zero reflection states as points in the UL signal constellation for efficient DL EH, and this constellation configuration may be a hybrid phase-amplitude indirect carrier modulation scheme with the lowest supported duty cycle factor and highest supported modulation depth for efficient DL EH, or a sparse block code-based indirect carrier modulation scheme with the maximum number of supported zero reflection states per code.

[0237] The lowest priority constellation in step S1004 may be a hybrid phase-amplitude indirect carrier modulation scheme with the highest supported duty cycle coefficient and the lowest supported modulation depth, or a sparse block code based indirect carrier modulation scheme including phase reversals of sinusoidal packets representing non-zero code entries.

[0238] In the method shown in Figure 10, the UE decides which modulation type / modulation order and associated constellation configuration to use based on assistance information from the network in the form of a priority / ranking list.

[0239] 11 shows a method 1100 in accordance with an embodiment of the present principles in which the UE has full control over which modulation type / modulation order and constellation configuration to use without any assistance from the network. We assume that the network can blindly detect which transmission configuration has been utilized for data transmission by the UE. In this embodiment, the UE can perform constellation adaptation based on channel quality indicator (CQI) measurements reported by the network.

[0240] In step S1102, the UE reports a list of supported class(es) or supported modulation type(s) / modulation order(s) and the corresponding received constellation / symbol configuration for each supported modulation type using the required standardized modulation type / modulation order with a specific constellation / symbol configuration.

[0241] In step S1104, the UE receives a mapping between the CQI value and the modulation type / modulation order and the corresponding constellation / symbol configuration based on the reported value.

[0242] In step S1106, the UE receives a CQI measurement support configuration, for example, a unique ID, a period of a unique ID transmission opportunity, and a modulation type / modulation order and constellation / symbol configuration.

[0243] In step S1108, the UE uses the signaled modulation type / modulation order and constellation / symbol configuration to transmit the configured unique ID, for example periodically, to facilitate CQI measurement by the network.

[0244] In step S1110, the UE receives the current measured CQI value (Q i ) periodically, or Q i is the following relationship

[0245]

number

[0246] In step S1112, the UE selects a constellation type from the pre-configured list based on the CQI value reported by the network and the pre-configured mapping.

[0247] In step S1114, the UE continues data transmission using the selected modulation type / modulation order and constellation setting.

[0248] FIG. 12 shows a method 1200 for performing constellation adaptation based on the constellation type configuration received by the UE from the network, in accordance with an embodiment of the present principles.

[0249] In step S1202, the UE reports a list of supported class(es) or supported modulation type(s) / modulation order(s) and corresponding constellation / symbol configurations using required standardized modulation types / modulation orders with specific constellation / symbol configurations.

[0250] In step S1204, the UE receives a priority or ranking (per modulation order) for the list of reported modulation and constellation configurations, where the default constellation type (highest priority) may be the one that provides the highest supported DL energy harvesting efficiency, and the lowest priority constellation may be the one that provides the highest UL transmission energy per bit for a given modulation order.

[0251] In step S1206, the UE receives a CQI measurement occasion configuration, such as a unique ID, modulation type / modulation order, and constellation / symbol configuration, for facilitating CQI measurement by the network.

[0252] In step S1208, the UE transmits the configured unique ID in the assigned measurement occasion using the signaled modulation type / modulation order and constellation / symbol configuration.

[0253] In step S1210, the UE receives a priority value from the network indicating the modulation type / modulation order and constellation configuration that should be first used for data transmission.

[0254] In step S1212, the UE receives a data retransmission request or fails to receive an ACK within a pre-specified time window for a specified signaling / pre-configured number of consecutive times.

[0255] In step S1214, the UE switches to the next configured constellation and modulation type on the priority list and retransmits the data.

[0256] In step S1216, the UE continues transmitting data using the selected constellation and modulation type as long as it does not receive a retransmission request or fails to receive an ACK (see step S1212). Otherwise, it repeats step S1214 until it has exhausted all constellations on its priority list or has reached a signaled or preset total number of retransmissions, at which point it declares a failure of the data transmission / connection. The method can then return to step S1206.

[0257] The default (highest priority) constellation configuration (see S1204) may utilize ICM zero reflection states as points in the UL signal constellation for efficient DL EH, and this constellation configuration may be a hybrid phase-amplitude indirect carrier modulation scheme with the lowest supported duty cycle factor and highest supported modulation depth for efficient DL EH, or a sparse block code based indirect carrier modulation scheme with the maximum number of supported zero reflection states per code.

[0258] The lowest priority constellation (see step S1204) may be a hybrid phase-amplitude indirect carrier modulation scheme with the highest supported duty cycle coefficient and the lowest supported modulation depth, or a sparse block code based indirect carrier modulation scheme with phase reversals of sinusoidal packets representing non-zero code entries.

[0259] FIG. 13 shows a method 1300 in accordance with an embodiment of the present principles in which a UE performs constellation adaptation based on an evaluation of a performance metric.

[0260] In step S1302, the UE reports a list of supported class(es) or supported modulation type(s) / modulation order(s) and corresponding constellation / symbol configurations using required standardized modulation types / modulation orders with specific constellation / symbol configurations.

[0261] In step S1304, the UE receives a transmission adaptation notification message configuration, such as a transmission period or trigger criteria and related parameters, modulation type / modulation order, and constellation configuration.

[0262] In step S1306, the UE receives configuration of the occasions for measuring the received inquiry signal strength (RISS), such as the type of occasion (single measurement occasion or non-single, i.e., resources are used for both measurement and UL data transmission), period of the occasion, modulation type / modulation order and constellation configuration associated with UL transmission in non-single occasions.

[0263] In step S1308, the UE measures the RISS over one or more measurement occasions to determine the DL energy harvesting efficiency (η) associated with the current UL transmission configuration.

[0264] In step S1310, the UE receives a data retransmission request from the network or a notification from a power management unit (PMU), and calculates a performance indicator (E H -E TX )={ηRISS-P ICM}(N / R)>δ and E TX Select a new constellation from the list of pre-specified UL constellation types such that P ICM is the power consumption of the ICM when configured for the new constellation, N is the UL data packet size, R is the UL data rate, and E TX is the UL transmit energy per symbol, and δ, Δ are optimization targets that may be pre-configured in the UE or signaled by the network as part of the trigger criteria.

[0265] In step S1312, the UE uses the pre-configured / signaled transmission configuration and sends a transmission adaptation notification message indicating the newly selected transmission configuration to be used in subsequent UL data packets.

[0266] In step S1314, the UE transmits the UL data packet using the new transmission configuration.

[0267] In one embodiment of a method 2400 according to the present principles, shown in FIG. 24, the UE may perform constellation adaptation after a data retransmission request from the network.

[0268] In step S2402, the UE uses the required standardized modulation type / modulation order with a specific constellation / symbol configuration to report a list of supported class(es) or supported modulation type(s) / modulation order(s) and the corresponding constellation / symbol configuration to the network.

[0269] In step S2404, the UE receives a priority or ranking (per modulation order) for the list of reported modulation and constellation configurations, where the default constellation type (i.e., with the highest priority) is the one that provides the highest supported DL energy harvesting efficiency, and the lowest priority constellation is the one that provides the highest UL transmission energy per bit for a given modulation order.

[0270] In step S2406, the UE transmits data using the highest priority constellation that provides the highest supported DL energy harvesting efficiency.

[0271] In step S2408, the UE receives a data retransmission request or fails to receive an ACK within a pre-specified time window for a specified signaling / pre-configured number of consecutive times.

[0272] In step S2410, the UE switches to the next configured constellation and modulation type on the priority list and retransmits the data.

[0273] In step S2412, the UE continues data transmission using the selected constellation and modulation type as long as it does not receive a retransmission request or receives an ACK (see step S1008), otherwise the UE repeats step S2410 until it has exhausted the constellations on its priority list or reached the signaled / preconfigured total number of retransmissions, at which point the UE declares a failure of the data transmission / connection.

[0274] In step S2404, for example, the default (highest priority) constellation setting for a passive device may utilize the zero reflection state of the ICM as a point in the UL signal constellation for efficient DL EH.

[0275] In step S2404, for example, the default (highest priority) constellation setting for a passive device may be a hybrid phase-amplitude indirect carrier modulation scheme with the lowest supported duty cycle factor and the highest supported modulation depth for efficient DL EH.

[0276] In step S2404, for example, the default (highest priority) constellation setting for a passive device may be a sparse block code-based indirect carrier modulation scheme with the maximum number of supported zero reflection states per code (i.e., maximum sparsity, highest code rate).

[0277] In step S2404, for example, the default (highest priority) constellation setting for a passive device may be a high-density block code-based indirect carrier modulation scheme with the maximum number of supported zero-reflection states per code (i.e., lowest density, lowest code rate).

[0278] In step S2404, for example, the lowest priority constellation for a passive device may be a hybrid phase-amplitude indirect carrier modulation scheme with the highest supported duty cycle coefficient and the lowest supported modulation depth.

[0279] In step S2404, for example, the lowest priority constellation setting for a passive device may be a high-density block code-based indirect carrier modulation scheme with the maximum supported number of full reflection states per code (i.e., maximum density, highest code rate).

[0280] In step S2404, the lowest priority constellation configuration, for example for a passive device, may be a sparse block code-based indirect carrier modulation scheme with the maximum supported number of fully reflective states per code (i.e., minimum sparsity, lowest code rate).

[0281] The lowest priority constellation in step S2404, for example for a passive device, may be a sparse block code based indirect carrier modulation scheme that includes phase reversals of sinusoidal packets representing non-zero code entries.

[0282] In the method shown in Figure 24, the UE decides which modulation type / modulation order and associated constellation configuration to use based on assistance information from the network in the form of a priority / ranking list.

[0283] FIG. 25 shows a method 2500 for performing constellation adaptation based on the constellation type configuration received by the UE from the network, in accordance with an embodiment of the present principles.

[0284] In step S2502, the UE reports a list of supported class(es) or supported modulation type(s) / modulation order(s) and corresponding constellation / symbol configurations using required standardized modulation types / modulation orders with specific constellation / symbol configurations.

[0285] In step S2504, the UE receives a priority or ranking for the list of reported modulation and constellation configurations (by modulation order).

[0286] The priority or ranking may include a default modulation / constellation type (highest priority) that provides the highest supported DL energy harvesting efficiency, e.g., suitable for battery-less passive devices. Alternatively, the priority or ranking may include a default modulation / constellation type (highest priority) that provides the highest UL transmit energy per bit for a given modulation order, e.g., suitable for active devices with on-board batteries.

[0287] The priority or ranking may include the lowest priority constellation that provides the highest UL transmission energy per bit for a given modulation order, e.g., suitable for battery-less passive devices, or the priority or ranking may include the lowest priority constellation that provides the highest supported DL energy harvesting efficiency, e.g., suitable for active devices with on-board batteries.

[0288] In step S2506, the UE receives a CQI measurement occasion configuration, such as a unique ID, modulation type / modulation order, and constellation / symbol configuration, for facilitating CQI measurement by the network.

[0289] In step S2508, the UE transmits the configured unique ID in the assigned measurement occasion using the signaled modulation type / modulation order and constellation / symbol configuration.

[0290] In step S2510, the UE receives a priority value from the network indicating the modulation type / modulation order and constellation configuration that should be first used for data transmission.

[0291] In step S2512, the UE receives a data retransmission request or fails to receive an ACK within a pre-specified time window for a specified signaling / pre-configured number of consecutive times.

[0292] In step S2514, the UE switches to the next configured constellation and modulation type on the priority list and retransmits the data.

[0293] In step S2516, the UE continues transmitting data using the selected constellation and modulation type as long as it does not receive a retransmission request or fails to receive an ACK (see step S2512). Otherwise, the UE repeats step S2514 until it has exhausted the constellations on its priority list or reached the signaled / preconfigured total number of retransmissions, at which point it declares a failure of the data transmission / connection. The method can then return to step S2506.

[0294] For example, the default (highest priority) constellation setting for a passive device (see step S2504) may utilize the ICM zero reflection state as a point in the UL signal constellation for efficient DL EH, and this constellation setting may be a hybrid phase-amplitude indirect carrier modulation scheme with the lowest supported duty cycle coefficient and the highest supported modulation depth for efficient DL EH, or a sparse block code-based indirect carrier modulation scheme with the maximum number of supported zero reflection states per code (i.e., maximum sparsity, highest code rate), or a dense block code-based indirect carrier modulation scheme with the maximum number of supported zero reflection states per code (i.e., minimum density, lowest code rate).

[0295] For example, the lowest priority constellation for a passive device (see step S2504) may be a hybrid phase-amplitude indirect carrier modulation scheme with the highest supported duty cycle coefficient and the lowest supported modulation depth, or a dense block code-based indirect carrier modulation scheme with the maximum supported number of fully reflective states per code (i.e., highest density, highest code rate), or a sparse block code-based indirect carrier modulation scheme with the maximum supported number of fully reflective states per code (i.e., minimum sparsity, lowest code rate), or a sparse block code-based indirect carrier modulation scheme that includes phase reversals of sinusoidal packets representing non-zero code entries.

[0296] Although features and elements are described above in particular combinations, those skilled in the art will understand that each feature or element may be used alone or in any combination with the other features and elements. Furthermore, the methods described herein may be implemented in a computer program, software, or firmware embodied in a computer-readable medium 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 in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A wireless transmit / receive unit, or WTRU, comprising: a transmitting and receiving element; an energy harvester; at least one hardware processor reversibly coupled to the transmit / receive element and configured to select a duty cycle factor and a modulation depth from a plurality of possible values of a modulation scheme; Equipped with The WTRU is configured to harvest energy from at least one received downlink transmission using the energy harvester while transmitting at least one uplink transmission using the transmit / receive element.

2. The WTRU of claim 1 , wherein the duty cycle factor is greater than 0 and less than 1.

3. The WTRU of claim 1 , wherein the duty cycle coefficient is selected from a set of duty cycle coefficients and the modulation index is selected from a set of modulation indices.

4. 4. The WTRU of claim 3, wherein the at least one hardware processor is configured to select the duty cycle coefficient and the modulation index by selecting a pair from a list of ordered pairs, each pair in the ordered list including a respective duty cycle coefficient and a respective modulation index.

5. 5. The WTRU of claim 4, wherein the at least one hardware processor is configured, upon receiving a retransmission request from an external device, to change the duty cycle coefficient and the modulation index from a currently selected pair to a pair following the currently selected pair in the ordered list of pairs.

6. The WTRU of claim 1 , wherein the at least one hardware processor is further configured to receive supported duty cycle factors and modulation depth values via the transmit / receive element.

7. The WTRU of claim 6 , wherein the supported duty cycle factor and modulation depth values are received in pairs comprising a duty cycle factor and a modulation depth.

8. The WTRU of claim 7, wherein each pair is associated with a channel quality value.

9. The WTRU of claim 8 , wherein the at least one hardware processor is further configured to receive a channel quality measurement and select the pair based on its associated channel quality value and the channel quality measurement.

10. The WTRU of claim 7 , wherein the at least one hardware processor is further configured to measure energy harvesting efficiency of the energy harvester and select the pair based on the measured energy harvesting efficiency.

11. The WTRU of claim 1 , wherein the modulation scheme is a Manchester coded on-off keying indirect carrier modulation scheme.

12. 1. A method in a wireless transmit / receive unit, or WTRU, comprising: a selection means for selecting a duty cycle factor and a modulation depth from a plurality of possible values of a modulation scheme; harvesting energy from at least one received downlink transmission using an energy harvesting means while transmitting at least one uplink transmission using a transmitting means; A method comprising:

13. 13. The method of claim 12, wherein the duty cycle coefficient is selected from a set of duty cycle coefficients and the modulation depth is selected from a set of modulation depths.

14. 14. The method of claim 13, wherein the duty cycle coefficient and the modulation depth are selected by selecting a pair from a list of ordered pairs, each pair in the ordered list including a respective duty cycle coefficient and a respective modulation depth.

15. 15. The method of claim 14, further comprising: upon receiving a retransmission request from an external device, the changing means changing from the duty cycle coefficient and the modulation index of a currently selected pair to a second duty cycle coefficient and a second modulation index of a pair following the currently selected pair in the list of ordered pairs.

16. 13. The method of claim 12, wherein the receiving means further comprises receiving supported duty cycle coefficients and modulation depth values.

17. 17. The method of claim 16, wherein the supported duty cycle factor and modulation depth values are received in pairs comprising a duty cycle factor and a modulation depth.

18. 20. The method of claim 17, wherein each pair is associated with a channel quality value.

19. the measuring means further comprising measuring an energy harvesting efficiency of the energy harvesting means; the pair is selected based on the measured energy harvesting efficiency.

18. The method of claim 17.

20. 13. The method of claim 12, wherein the modulation scheme is a Manchester coded on-off keying indirect carrier modulation scheme.

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