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WO2025201620A1 - Radio à rétrodiffusion basée sur l'ofdm avec déplacement de fréquence et de temps - Google Patents

Radio à rétrodiffusion basée sur l'ofdm avec déplacement de fréquence et de temps

Info

Publication number
WO2025201620A1
WO2025201620A1 PCT/EP2024/057939 EP2024057939W WO2025201620A1 WO 2025201620 A1 WO2025201620 A1 WO 2025201620A1 EP 2024057939 W EP2024057939 W EP 2024057939W WO 2025201620 A1 WO2025201620 A1 WO 2025201620A1
Authority
WO
WIPO (PCT)
Prior art keywords
ofdm
signal
network node
frequency
ofdm signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/EP2024/057939
Other languages
English (en)
Inventor
Miguel Lopez
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
Priority to PCT/EP2024/057939 priority Critical patent/WO2025201620A1/fr
Publication of WO2025201620A1 publication Critical patent/WO2025201620A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators
    • H04L27/2634—Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/76—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein pulse-type signals are transmitted
    • G01S13/765—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein pulse-type signals are transmitted with exchange of information between interrogator and responder
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2697—Multicarrier modulation systems in combination with other modulation techniques

Definitions

  • the present disclosure relates to wireless communications, and in particular, to differential modulation and demodulation for backscatter radio.
  • the Third Generation Partnership Project (3GPP) has developed and is developing standards for Fourth Generation (4G) (also referred to as Long Term Evolution (LTE)) and Fifth Generation (5G) (also referred to as New Radio (NR)) wireless communication systems. Such systems provide, among other features, broadband communication between network nodes, such as base stations, and mobile wireless devices (WD), as well as communication between network nodes and between WDs.
  • 4G Fourth Generation
  • 5G Fifth Generation
  • NR New Radio
  • Such systems provide, among other features, broadband communication between network nodes, such as base stations, and mobile wireless devices (WD), as well as communication between network nodes and between WDs.
  • the 3GPP is also developing standards for Sixth Generation (6G) wireless communication networks.
  • WLANs Wireless Local Area Networks
  • AP STAs access points
  • non-AP STAs non-access point stations
  • IEEE 802.1 la/b/g/n/ac/ax/be IEEE 802.15.
  • Backscatter radio is a technology well suited for ultra-low power and low-cost radios. For example, it is used in radio frequency identification (RFID) tags to track products, and it is being considered as a candidate technology for ultra-low power loT devices in both 3GPP and IEEE 802.11.
  • RFID radio frequency identification
  • FIG. 1 illustrates an example of a baseband representation of a bistatic backscattering scenario.
  • a transmitter TX sends an unmodulated carrier c 0 , which illuminates a backscatter tag.
  • the carrier signal c 0 is reflected by the tag and has the form c 0 ⁇ x, where x is a complex-valued reflection coefficient.
  • the receiver RX receives the superposition of the carrier signal c 0 (often called the direct link or direct path) and the backscattered signal c 0 ⁇ x.
  • FIG. 1 illustrates bistatic backscattering where c 0 is the complex baseband representation of the carrier and x is a complex-valued reflection coefficient. In practice the backscattered signal is often much weaker than the carrier.
  • the receiver may filter out the interference from c 0 by means of a channel selective filter. This is illustrated in FIG. 2.
  • FIG. 2 illustrates bistatic backscattering with frequency shift, where c 0 is the complex baseband representation of the carrier, x is a complex-valued reflection coefficient and is a baseband representation of a carrier at a different frequency from the carrier c 0 .
  • Backscattering may also be used in more complex scenarios where the transmitter sends communications signals (i.e., the carrier c 0 is modulated), and as in FIG. 2, the tag may introduce a frequency shift to the reflected signal, as illustrated in FIG. 3.
  • s is the symbol modulating the carrier, while c 0 , and x are the same as shown in FIGS. 1 and 2.
  • FIG. 3 illustrates bistatic backscattering where the transmitter sends a modulated carrier.
  • c 0 is the complex baseband representation of the carrier
  • 5 is a complex symbol modulating the carrier
  • x is a complex-valued reflection coefficient and represents a carrier at a frequency different from c 0 .
  • the TX and RX are co-located in the same node, so that the above description needs to be suitably modified.
  • the TX and RX are operating simultaneously in the same node, so that the TX self-jams the RX.
  • the signals from the TX to the tag, and the reflection from the tag to the RX may be described as in FIGS. 1-3.
  • TX nodes in backscattering systems such as RFID send continuous waves.
  • backscattering technologies are to be supported by communication nodes in broadband systems such as NR or Wi-Fi
  • OFDM orthogonal frequency division multiplexed
  • One reason is that there may be local regulatory constraints on the TX power for narrowband signals so that peak output power may only be used with wideband signals.
  • Another reason is that it may be desirable to share the band between backscattering devices and broadband devices.
  • a pure carrier does not carry information so that a TX that sends only a continuous wave may not utilize the spectrum for communications while backscattering is ongoing.
  • backscattering broadband signals e.g., backscattered OFDM signals.
  • Reception of backscattered OFDM signals is an extremely challenging problem and it is very difficult for the RX to handle the interference from the TX.
  • Some embodiments advantageously provide methods, backscattering devices and network nodes for differential modulation and demodulation for backscatter radio.
  • the TX illuminates the tag with an ordinary OFDM signal that may carry information addressed to broadband users.
  • the tag modulates the reflections of the impinging OFDM signal in such a way that the reflected RF signal is shifted in frequency and does not overlap in the frequency domain with the signal sent by the TX.
  • the RX may separate filter the direct link signal from the TX and reflect a backscattered signal at a frequency that is different than the frequency of the direct link signal.
  • the RX first decodes the direct link OFDM signal. Afterwards it analyzes the backscattered signal in the frequency domain, and uses the decoded OFDM signal to remove the effect of the OFDM modulation symbols on the backscattered signal.
  • the resulting signal is an OFDM signal including repetitions in time and frequency of the modulation symbols sent by the backscattering tag.
  • the receiver is not a typical successive interference receiver because the interference to be removed is not additive but rather multiplicative. Also, if the direct link signal is decoded correctly, the impact of the interference may be perfectly suppressed because the removal process does not depend on channel estimates.
  • Some embodiments include simultaneous transmission of data from a TX node and from a backscattering tag.
  • the backscattered signals are well suited for reception by OFDM broadband receivers (as opposed to specialized receivers as in RFID). Since the backscattered signal is a slightly modified OFDM signal, the receiver may benefit from frequency diversity.
  • a method in a backscattering device configured to reflect signals received from a network node.
  • the method includes receiving an orthogonal frequency division multiplexed, OFDM, signal in a first radio frequency channel from the network node.
  • the method includes frequency shifting the received OFDM signal to a second radio frequency channel different from the first radio frequency channel.
  • the method also includes reflecting the frequency shifted received OFDM signal.
  • the method further includes synchronizing reflecting of the frequency shifted received OFDM signal to an OFDM time grid.
  • an amount of the frequency shifting is determined by a parameter received from the network node.
  • synchronizing reflecting of the frequency shifted OFDM signal to an OFDM time grid includes synchronizing to a timing signal received from the network node.
  • synchronizing to the OFDM time grid causes modulation symbols to start within a cyclic prefix of OFDM symbols in the received OFDM signal.
  • a duration of a reflected modulation symbol is not less than an OFDM symbol duration.
  • a backscattering device configured to reflect signals received from a network node.
  • the backscattering device is configured to receive an orthogonal frequency division multiplexed, OFDM, signal in a first radio frequency channel from the network node.
  • the backscattering device is configured to frequency shift the received OFDM signal to a second radio frequency channel different from the first radio frequency channel.
  • the backscattered device is also configured to reflect the frequency shifted received OFDM signal, and synchronize reflecting of the frequency shifted received OFDM signal to an OFDM time grid.
  • an amount of the frequency shifting is determined by a parameter received from the network node.
  • synchronizing reflecting of the frequency shifted OFDM signal to an OFDM time grid includes synchronizing to a timing signal received from the network node.
  • synchronizing to the OFDM time grid causes modulation symbols to start within a cyclic prefix of OFDM symbols in the received OFDM signal.
  • a duration of a reflected modulation symbol is not less than an OFDM symbol duration.
  • a method in a network node configured to illuminate a backscattering device includes configuring the backscattering device with a frequency shift parameter indicating an amount by which to frequency shift a received orthogonal frequency division multiplexed, OFDM, signal from a first carrier frequency to a second carrier frequency to be reflected by the backscattering device in synchronization with an OFDM time grid.
  • a frequency shift parameter indicating an amount by which to frequency shift a received orthogonal frequency division multiplexed, OFDM, signal from a first carrier frequency to a second carrier frequency to be reflected by the backscattering device in synchronization with an OFDM time grid.
  • the first and second carrier frequencies are selected to coincide with subcarrier frequencies of a frequency raster of an OFDM configuration.
  • the method includes configuring the backscattering device to reflect the received OFDM signal with a symbol duration that is an integer multiple of an OFDM symbol duration of the received OFDM signal.
  • the method includes transmitting an illumination signal at the first carrier frequency, the illumination signal comprising OFDM symbols.
  • the method includes configuring the backscattering device with an indication of a time to start a reflection of a received OFDM signal.
  • a network node configured to illuminate a backscattering device.
  • the network node is configured to configure the backscattering device with a frequency shift parameter indicating an amount by which to frequency shift a received orthogonal frequency division multiplexed, OFDM, signal from a first carrier frequency to a second carrier frequency to be reflected by the backscattering device in synchronization with an OFDM time grid.
  • OFDM orthogonal frequency division multiplexed
  • the first and second carrier frequencies are selected to coincide with subcarrier frequencies of a frequency raster of an OFDM configuration.
  • the network node is further configured to configure the backscattering device to reflect the received OFDM signal with a symbol duration that is an integer multiple of an OFDM symbol duration of the received OFDM signal.
  • the network node is further configured to transmit an illumination signal at the first carrier frequency, the illumination signal comprising OFDM symbols.
  • the network node is further configured to configure the backscattering device with an indication of a time to start a reflection of a received OFDM signal.
  • a method in a first network node includes simultaneously receiving a first orthogonal frequency division multiplexed, OFDM, signal, from a second network node at a first carrier frequency and a second OFDM signal reflected from a backscattering device at a second carrier frequency, the second OFDM signal being a frequency shifted reflection of the first OFDM signal.
  • the method includes separating the first and second OFDM signals.
  • the method also includes determining samples of OFDM symbols in the second OFDM signal based at least in part on samples of OFDM symbols in the first OFDM signal.
  • determining samples of the OFDM symbols in the second OFDM signal includes estimating samples of corresponding OFDM symbols in the first OFDM signal. In some embodiments, determining samples of the OFDM symbols in the second OFDM signal includes dividing OFDM samples in the second OFDM signal by corresponding estimates of the samples of OFDM symbols in the first OFDM signal. In some embodiments, a first symbol rate of the first OFDM signal is an integer multiple of a second symbol rate of the second OFDM signal. In some embodiments, the first and second carrier frequencies are selected to coincide with subcarrier frequencies of a frequency raster of an OFDM configuration.
  • a first network node is configured to: simultaneously receive a first orthogonal frequency division multiplexed, OFDM, signal, from a second network node at a first carrier frequency and a second OFDM signal reflected from a backscattering device at a second carrier frequency, the second OFDM signal being a frequency shifted reflection of the first OFDM signal.
  • the first network node is configured to separate the first and second OFDM signals.
  • the network node is also configured to determine samples of OFDM symbols in the second OFDM signal based at least in part on samples of OFDM symbols in the first OFDM signal.
  • determining samples of the OFDM symbols in the second OFDM signal includes estimating samples of corresponding OFDM symbols in the first OFDM signal. In some embodiments, determining samples of the OFDM symbols in the second OFDM signal includes dividing OFDM samples in the second OFDM signal by corresponding estimates of the samples of OFDM symbols in the first OFDM signal. In some embodiments, a first symbol rate of the first OFDM signal is an integer multiple of a second symbol rate of the second OFDM signal. In some embodiments, the first and second carrier frequencies are selected to coincide with subcarrier frequencies of a frequency raster of an OFDM configuration.
  • FIG. 1 illustrates a baseband representation of a bistatic backscattering scenario
  • FIG. 2 illustrates bistatic backscattering with frequency shift
  • FIG. 3 illustrates bistatic backscattering where the transmitter sends a modulated carrier
  • FIG. 4 is a schematic diagram of an example network architecture illustrating a communication system according to principles disclosed herein;
  • FIG. 5 is a block diagram of a network node in communication with a wireless device over a wireless connection according to some embodiments of the present disclosure
  • FIG. 6 is a flowchart of an example process in a backscattering device for differential modulation and demodulation for backscatter radio;
  • FIG. 7 is a flowchart of an example process in a network node for differential modulation and demodulation for backscatter radio;
  • FIG. 8 is a flowchart of an example process in a network node for differential modulation and demodulation for backscatter radio.
  • FIG. 9 illustrates frequency shifting according to principles disclosed herein.
  • relational terms such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements.
  • the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein.
  • the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
  • the joining term, “in communication with” and the like may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example.
  • electrical or data communication may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example.
  • Coupled may be used herein to indicate a connection, although not necessarily directly, and may include wired and/or wireless connections.
  • network node may be any kind of network node included in a radio network which may further include any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi-standard radio (MSR) radio node such as MSR BS, multi-cell/multicast coordination entity (MCE), relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self- organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node,
  • BS base station
  • wireless device or a user equipment (UE) are used interchangeably.
  • the WD herein may be any type of wireless device capable of communicating with a network node or another WD over radio signals, such as wireless device (WD).
  • the WD may also be a radio communication device, target device, device to device (D2D) WD, machine type WD or WD capable of machine to machine communication (M2M), low-cost and/or low-complexity WD, a sensor equipped with WD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), an Internet of Things (loT) device, or a Narrowband loT (NB-IOT) device etc.
  • D2D device to device
  • M2M machine to machine communication
  • M2M machine to machine communication
  • Tablet mobile terminals
  • smart phone laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles
  • CPE Customer Premises Equipment
  • LME Customer Premises Equipment
  • NB-IOT Narrowband loT
  • WCDMA Wide Band Code Division Multiple Access
  • WiMax Worldwide Interoperability for Microwave Access
  • UMB Ultra Mobile Broadband
  • GSM Global System for Mobile Communications
  • functions described herein as being performed by a wireless device or a network node may be distributed over a plurality of wireless devices and/or network nodes.
  • the functions of the network node and wireless device described herein are not limited to performance by a single physical device and, in fact, may be distributed among several physical devices.
  • Some embodiments are directed to differential modulation and demodulation for backscatter radio.
  • FIG. 4 a schematic diagram of a communication system 10, according to an embodiment, such as a 3 GPP -type cellular network that may support standards such as LTE and/or NR (5G), which includes an access network 12, such as a radio access network, and a core network 14.
  • the access network 12 includes a plurality of network nodes 16a, 16b, 16c (referred to collectively as network nodes 16), such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (referred to collectively as coverage areas 18).
  • Each network node 16a, 16b, 16c is connectable to the core network 14 over a wired or wireless connection 20.
  • a first wireless device (WD) 22a located in coverage area 18a is configured to wirelessly connect to, or be paged by, the corresponding network node 16a.
  • a second WD 22b in coverage area 18b is wirelessly connectable to the corresponding network node 16b. While a plurality of WDs 22a, 22b (collectively referred to as wireless devices 22) are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole WD is in the coverage area or where a sole WD is connecting to the corresponding network node 16. Note that although only two WDs 22 and three network nodes 16 are shown for convenience, the communication system may include many more WDs 22 and network nodes 16.
  • a WD 22 may be in simultaneous communication and/or configured to separately communicate with more than one network node 16 and more than one type of network node 16.
  • a WD 22 may have dual connectivity with a network node 16 that supports LTE and the same or a different network node 16 that supports NR.
  • WD 22 may be in communication with an eNB for LTE/E-UTRAN and a gNB for NR/NG-RAN.
  • a network node 16 (eNB or gNB) may be configured to include an OFDM unit
  • the OFDM unit 24 may be configured to configure a backscattering device 26 with a frequency shift parameter indicating an amount by which to frequency shift a received orthogonal frequency division multiplexed, OFDM, signal from a first carrier frequency to a second carrier frequency to be reflected by the backscattering device 26 in synchronization with an OFDM time grid.
  • the controller may be configured to configure a backscattering device 26 with a frequency shift parameter indicating an amount by which to frequency shift a received orthogonal frequency division multiplexed, OFDM, signal from a first carrier frequency to a second carrier frequency to be reflected by the backscattering device 26 in synchronization with an OFDM time grid.
  • the 25 may be configured to separate the first and second OFDM signals, the first OFDM signal being received from another network node and the second OFDM signal being received from a backscattering device 26.
  • the backscattering device 26 may be configured to include a frequency converter 60 and an OFDM synchronizer 62.
  • the frequency converter 60 may be configured to frequency shift the received OFDM signal to a second radio frequency channel different from the first radio frequency channel.
  • the OFDM synchronizer 62 may be configured to synchronize reflections of the backscattering device 36 with an OFDM time grid.
  • Example implementations, in accordance with an embodiment, of the WD 22 and network node 16 discussed in the preceding paragraphs will now be described with reference to FIG. 5.
  • the communication system 10 includes a network node 16 provided in a communication system 10 and including hardware 28 enabling it to communicate with the WD 22.
  • the hardware 28 may include a radio interface 30 for setting up and maintaining at least a wireless connection 32 with a WD 22 located in a coverage area 18 served by the network node 16.
  • the radio interface 30 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and/or one or more RF transceivers.
  • the radio interface 30 includes an array of antennas 34 to radiate and receive signal(s) carrying electromagnetic waves.
  • the communication system 10 further includes the WD 22 already referred to.
  • the WD 22 may have hardware 44 that may include a radio interface 46 configured to set up and maintain a wireless connection 32 with a network node 16 serving a coverage area 18 in which the WD 22 is currently located.
  • the radio interface 46 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and/or one or more RF transceivers.
  • the radio interface 46 includes an array of antennas 48 to radiate and receive signal(s) carrying electromagnetic waves.
  • the hardware 44 of the WD 22 further includes processing circuitry 50.
  • the processing circuitry 50 may include a processor 52 and memory 54.
  • the processing circuitry 50 may include integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions.
  • processors and/or processor cores and/or FPGAs Field Programmable Gate Array
  • ASICs Application Specific Integrated Circuitry
  • the processor 52 may be configured to access (e.g., write to and/or read from) memory 54, which may include any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read-Only Memory).
  • memory 54 may include any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read-Only Memory).
  • the WD 22 may further include software 56, which is stored in, for example, memory 54 at the WD 22, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the WD 22.
  • the software 56 may be executable by the processing circuitry 50.
  • the software 56 may include a client application 58.
  • the client application 58 may be operable to provide a service to a human or non-human user via the WD 22.
  • the processing circuitry 50 may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by WD 22.
  • the processor 52 corresponds to one or more processors 52 for performing WD 22 functions described herein.
  • the WD 22 includes memory 54 that is configured to store data, programmatic software code and/or other information described herein.
  • the software 56 and/or the client application 58 may include instructions that, when executed by the processor 52 and/or processing circuitry 50, causes the processor 52 and/or processing circuitry 50 to perform the processes described herein with respect to WD 22.
  • the inner workings of the network node 16 and WD 22 may be as shown in FIG. 5 and independently, the surrounding network topology may be that of FIG. 4.
  • the wireless connection 32 between the WD 22 and the network node 16 is in accordance with the teachings of the embodiments described throughout this disclosure. More precisely, the teachings of some of these embodiments may improve the data rate, latency, and/or power consumption and thereby provide benefits such as reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime, etc. In some embodiments, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve.
  • FIGS. 4 and 5 show various “units” such as OFDM unit 24 and controller 25 as being within a respective processor, it is contemplated that these units may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuitry. In other words, the units may be implemented in hardware or in a combination of hardware and software within the processing circuitry.
  • an amount of the frequency shifting is determined by a parameter received from the network node 16.
  • synchronizing reflecting of the frequency shifted OFDM signal to an OFDM time grid includes synchronizing to a timing signal received from the network node 16.
  • synchronizing to the OFDM time grid causes modulation symbols to start within a cyclic prefix of OFDM symbols in the received OFDM signal.
  • a duration of a reflected modulation symbol is not less than an OFDM symbol duration.
  • FIG. 8 is a flowchart of an example process in a first network node 16 according to some embodiments of the present disclosure.
  • One or more blocks described herein may be performed by one or more elements of network node 16 such as by one or more of processing circuitry 36 (including the OFDM unit 24 and/or controller 25), processor 38, and/or radio interface 30.
  • determining samples of the OFDM symbols in the second OFDM signal includes estimating samples of corresponding OFDM symbols in the first OFDM signal. In some embodiments, determining samples of the OFDM symbols in the second OFDM signal includes dividing OFDM samples in the second OFDM signal by corresponding estimates of the samples of OFDM symbols in the first OFDM signal. In some embodiments, a first symbol rate of the first OFDM signal is an integer multiple of a second symbol rate of the second OFDM signal. In some embodiments, the first and second carrier frequencies are selected to coincide with subcarrier frequencies of a frequency raster of an OFDM configuration.
  • Embodiments disclosed herein involve modulation of the symbols transmitted by the backscattering device 26 and decoding these symbols at the receiver.
  • the signal p m may be a conventional signal (e.g., it may be considered as a simple OFDM signal with only one active subcarrier) so that the receiver may estimate the channel and the transmitted symbols using any known method (e.g., by using zeroforcing or minimum mean square error (MMSE) equalizers).
  • MMSE minimum mean square error
  • the receiver may employ the signal corresponding to the subcarrier c 0 to compute estimates s m of the transmitted symbols.
  • the network node 16b may use it to produce estimates of the transmitted symbols. Also as before, assume that due to channel coding and the CRC, the receiver may determine with high probability the exact value of the transmitted symbols s n k .
  • the signal from the backscattering device 26 may be modeled as the superposition of several narrowband signals, each of which may be analyzed as described above.
  • the OFDM signal sent by the network node 16a includes K subcarriers. Further, suppose that the signal is sampled K times in every OFDM symbol.
  • the transmission of the first data symbol x ⁇ by the backscattering device 26 This symbol is spread over the first N OFDM symbols in the OFDM signal sent by the network node 16a.
  • the received samples arise from a superposition of subcarriers, and the reflection coefficient x affects equally the phase and amplitude of all the subcarriers in a group of N consecutive OFDM symbols.
  • DFT discrete Fourier transform
  • the network node 16b may perform channel estimation and synchronization with the help of some pilot symbols x lt ... , x m .
  • the backscattering device 26 may determine when to start its transmission by, for example receiving an explicit control message from the network node indicating the time to start the backscatter transmission. Alternatively, or in addition, the backscattering device 26 may use its receiver to determine the timings of the start of the CP. For example, the network may send a command instructing the backscattering device 26 to initiate backscattering at a given clock tick with respect to a time base counter(s). Then, at a few clock ticks before the intended initiation time, the backscattering device 26 may use its receiver to detect the arrival of the illuminating OFDM signal (e.g., using an energy detector), and use this detection to determine the time boundaries of the OFDM time grid. Then it may align its transmission to the determined grid.
  • the network may send a command instructing the backscattering device 26 to initiate backscattering at a given clock tick with respect to a time base counter(s). Then, at a few clock ticks before the
  • Some embodiments may include one or more of the following:
  • the controller selects a center frequency and bandwidth for an OFDM transmission from the network node 16a, a receiver bandwidth for the network node 16b, and a frequency shift and modulation symbol duration parameters for the backscattering device 26;
  • the backscattering device 26 backscatters the OFDM signal and imparts a frequency shift to it, as indicated by the frequency shift parameter, and the duration of the backscattered modulation symbol, as indicated by the duration parameter, is equal or exceeds the OFDM symbol duration;
  • Embodiment 2 As in Embodiment 1, where the backscattering device synchronizes in time its transmissions to the OFDM time grid, such that the modulation symbols start within the cyclic prefix of the OFDM symbols.
  • Any suitable tangible computer readable medium may be utilized including hard disks, CD- ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.
  • These computer program instructions may be provided to a processor of a general purpose computer (to thereby create a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
  • These computer program instructions may also be stored in a computer readable memory or storage medium that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks.

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Signal Processing (AREA)
  • Discrete Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un procédé, un dispositif de rétrodiffusion et des nœuds de réseau pour une modulation et une démodulation différentielles pour une radio à rétrodiffusion. Selon un aspect, un procédé dans un dispositif de rétrodiffusion consiste à recevoir un signal multiplexé par répartition orthogonale de la fréquence (OFDM) dans un premier canal de radiofréquence provenant du nœud de réseau. Le procédé consiste à appliquer un déplacement de fréquence au signal OFDM reçu vers un second canal de radiofréquence différent du premier canal de radiofréquence. Le procédé consiste en outre à réfléchir le signal OFDM reçu ayant subi un déplacement de fréquence. Le procédé consiste également à synchroniser la réflexion du signal OFDM reçu ayant subi un déplacement de fréquence sur un réseau temporel OFDM.
PCT/EP2024/057939 2024-03-25 2024-03-25 Radio à rétrodiffusion basée sur l'ofdm avec déplacement de fréquence et de temps Pending WO2025201620A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2024/057939 WO2025201620A1 (fr) 2024-03-25 2024-03-25 Radio à rétrodiffusion basée sur l'ofdm avec déplacement de fréquence et de temps

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2024/057939 WO2025201620A1 (fr) 2024-03-25 2024-03-25 Radio à rétrodiffusion basée sur l'ofdm avec déplacement de fréquence et de temps

Publications (1)

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WO2025201620A1 true WO2025201620A1 (fr) 2025-10-02

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PCT/EP2024/057939 Pending WO2025201620A1 (fr) 2024-03-25 2024-03-25 Radio à rétrodiffusion basée sur l'ofdm avec déplacement de fréquence et de temps

Country Status (1)

Country Link
WO (1) WO2025201620A1 (fr)

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
CHI ZICHENG ZICHENG1@UMBC EDU ET AL: "Leveraging Ambient LTE Traffic for Ubiquitous Passive Communication", PROCEEDINGS OF THE ANNUAL CONFERENCE OF THE ACM SPECIAL INTEREST GROUP ON DATA COMMUNICATION ON THE APPLICATIONS, TECHNOLOGIES, ARCHITECTURES, AND PROTOCOLS FOR COMPUTER COMMUNICATION, ACMPUB27, NEW YORK, NY, USA, 30 July 2020 (2020-07-30), pages 172 - 185, XP058475986, ISBN: 978-1-4503-7955-7, DOI: 10.1145/3387514.3405861 *
YU JIHONG ET AL: "SubScatter: Subcarrier-Level OFDM Backscatter", IEEE INFOCOM 2023 - IEEE CONFERENCE ON COMPUTER COMMUNICATIONS, IEEE, 17 May 2023 (2023-05-17), pages 1 - 10, XP034412457, DOI: 10.1109/INFOCOM53939.2023.10228918 *
ZHU FENGYUAN ET AL: "Enabling OFDMA in Wi-Fi Backscatter", IEEE /ACM TRANSACTIONS ON NETWORKING, IEEE / ACM, NEW YORK, NY, US, vol. 32, no. 1, 1 February 2024 (2024-02-01), pages 427 - 444, XP011960925, ISSN: 1063-6692, [retrieved on 20230710], DOI: 10.1109/TNET.2023.3290370 *

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