Coexistence of backscattering transmission and active transmission

Abstract

A wireless communication device (59) receives, during a transmission interval (906) and using an active transmission (199), a signal (51) from another wireless communication device (61). The wireless communication device also obtains information for reducing an interference signal (55) affecting the signal (51) during the transmission interval (906), the interference signal (55) stemming from a backscattering transmission (190).

Description

[0001] D E S C R I P T I O N

[0002] COEXISTENCE OF BACKSCATTERING TRANSMISSION AND ACTIVE TRANSMISSION

[0003] TECHNICAL FIELD

[0004] Various examples of the disclosure generally pertain to facilitating coexistence of a backscattering transmission and an active transmission. Various examples of the disclosure specifically pertain to techniques of mitigating interference present in the active transmission and stemming from the backscattering transmission.

[0005] BACKGROUND

[0006] Conventional active transmission requires generating radio signals at a wireless device acting as data source, i.e., at a wireless device that intends to deliver the data to another device (data sink). The radio signals are generated using active radio-frequency (RF) components such as digital-to-analog converters (DACs), mixers, oscillators, and power amplifiers. Usually, such wireless devices are battery powered and the aforementioned RF components consume a substantial amount of the energy provided by the battery. Hence, the batteries will have to be recharged or replaced regularly. This is inconvenient. The demand for new batteries has to be reduced, too, in view of the limited natural resources required for battery production.

[0007] To reduce power consumption at the wireless communication device (WD) implementing the data source, the Third Generation Partnership Project (3GPP) studies so-called Ambient Internet Of Things (AIOT) WDs. AIOT WDs are a particular implementation of low-power WDs. See 3GPP Technical Report (TR) 38.848 V18.0.0 (2023-09). AIOT WDs may be pure batteryless devices with no energy storage capability at all, and completely dependent on the availability of an external source of energy. AIOT WDs may also have a limited energy storage capability that do not need to be replaced or recharged manually.

[0008] To facilitate the reduced power consumption, AIOT WDs (or more generally low-power WDs) may employ a backscattering (BSc) transmission. Here, the low-power WD, i.e., the data source, implements a BSc node that modulates an excitation signal transmitted by a transmitting node of the BSc transmission. This modulation is done by selectively suppressing reflection (load modulation); this is achieved by adjusting an impedance coupled to the antenna. Thereby, an information-carrying signal (BSc signal) that is modulated to carry the information can be received at another WD of the BSc transmission that implements a receiving node of the BSc transmission.

[0009] Such load modulation typically requires significantly less energy at the low-power WD acting as data source if compared to the active transmission where radio waves are generated using power-hungry RF transmitter chains. It is estimated to have 1 pW in peak power consumption at the low-power WD. On the other hand, coverage is significantly reduced if compared to conventional active wireless transmission. Coverage for ambient wireless transmissions is expected to be in a range of 10 meters to 50 meters.

[0010] It has been observed that a BSc transmission can cause interference at a nearby WD participating in an active transmission.

[0011] One option to mitigate such interference is to separate the BSc transmission and the active transmission in frequency domain. One or more bands of the BSc transmission can be separated from one or more bands of the active transmission by guard bands See Third Generation Partnership Project (3GPP) R1 -2403487.

[0012] However, employing guard bands and thereby separating the BSc transmission and the active transmission in frequency domain reduces the resources available for the active transmission. Thus, the data throughput of the active transmission is reduced.

[0013] SUMMARY

[0014] Accordingly, a need exists for advanced techniques of facilitating coexistence of a BSc transmission and an active transmission. A need exists for advanced techniques of mitigating interference between a BSc transmission and an active transmission. More specifically, a need exists for interference-mitigation techniques that make better use of the available radio resources, i.e. , have a reduced resource overhead.

[0015] This need is met by the features of the independent claims. The features of the dependent claims define embodiments.

[0016] A method for use in a wireless communication device is disclosed. The wireless communication device is associated with a wireless communication network. The method includes receiving a signal from another wireless communication device. The signal is received during a transmission interval. The signal is received using an active transmission. The another wireless communication device is associated with the wireless communication network. The method also includes obtaining information for reducing an interference signal. The interference signal affects the signal during the transmission interval. The interference signal stems from a backscattering transmission.

[0017] The backscattering transmission may be regulated by the wireless communication network. The wireless communication network may be a cellular network, e.g., a 3GPP 5G or 6G network.

[0018] A wireless communication device for association with a wireless communication network is disclosed. The wireless communication device includes a processor and a memory. The processor is configured to load program code from the memory. The processor is further configured to execute the program code. The processor, upon loading and executing the program code, is configured to receive a signal from another wireless communication device that is also associated with the wireless communication network during a transmission interval and using an active transmission. The processor, upon loading and executing the program code, is further configured to obtain information for reducing an interference signal. The interference signal affects the signal during the transmission interval. The interference signal stems from a backscattering transmission.

[0019] A method for use in a wireless communication device is disclosed. The wireless communication device is associated with a wireless communication network. The method includes providing, to another wireless communication device associated with the wireless communication network, information for reducing interference signal. The interference signal affects a signal that is received by the another wireless communication device during a transmission interval. The interference signal stems from a backscattering transmission. The method may furthermore include the wireless communication device transmitting the signal to the another wireless communication device during the transmission interval. It would also be possible that the signal is transmitted by yet another wireless communication device during the transmission interval.

[0020] A wireless communication device for association with a wireless communication network is disclosed. The wireless communication device includes a processor and a memory. The processor is configured to load program code from the memory. The processor is further configured to execute the program code. The processor, upon loading and executing the program code, is configured to provide, to another wireless communication device associated with the wireless communication network, information for reducing an interference signal affecting a signal received by the another wireless communication device during the transmission interval during a transmission interval the interference signal stems from a backscattering transmission. The processor, upon loading and executing the program code, may be further configured to transmit the signal during the transmission interval to the another wireless communication device.

[0021] It is to be understood that the features mentioned above and those yet to be explained below may be used not only in the respective combinations indicated, but also in other combinations or in isolation without departing from the scope of the invention.

[0022] BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 schematically illustrates a deployment scenario of a backscattering communication system and interference of the backscattering transmission to an active transmission.

[0024] FIG. 2 schematically illustrates another deployment scenario of a backscattering communication system and interference of the backscattering transmission to an active transmission.

[0025] FIG. 3 schematically further illustrates the interference of the backscattering transmission to the active transmission.

[0026] FIG. 4 is a schematic illustration of a radio-frequency circuitry for modulating an incident excitation signal at a low-power WD.

[0027] FIG. 5 schematically illustrates On-Off-Keying modulation employed for a backscattering transmission according to various examples.

[0028] FIG. 6A schematically illustrates frequency bands of an active transmission in frequency bands of a backscattering transmission, wherein in FIG. 6A guard bands are used.

[0029] FIG. 6B schematically illustrates frequency bands of an active transmission in frequency bands of a backscattering transmission, wherein in FIG. 6B guard bands are not used.

[0030] FIG. 7 schematically illustrates a WD according to various examples.

[0031] FIG. 8 is a flowchart of a method for use in a WD according to various examples, wherein the WD implements a receiving node of an active transmission.

[0032] FIG. 9 is a flowchart of a method according to various examples, wherein FIG. 9 is an example implementation of the method of FIG. 8.

[0033] FIG. 10 is a flowchart of a method according to various examples.

[0034] FIG. 11 is a flowchart of a method according to various examples, wherein FIG. 11 is an example implementation of the method of FIG. 8.

[0035] FIG. 12 is a flowchart of a method according to various examples, wherein FIG. 12 is an example implementation of the method of FIG. 8.

[0036] FIG. 13 is a signaling diagram according to various examples. FIG. 14 is a signaling diagram according to various examples.

[0037] FIG. 15 is a signaling diagram according to various examples.

[0038] FIG. 16 is a signaling diagram according to various examples.

[0039] FIG. 17 is a flowchart of a method for use in a WD according to various examples, wherein the WD implements a transmitting node of an active transmission.

[0040] DETAILED DESCRIPTION

[0041] Some examples of the present disclosure generally provide for a plurality of circuits or other electrical devices. All references to the circuits and other electrical devices and the functionality provided by each are not intended to be limited to encompassing only what is illustrated and described herein. While particular labels may be assigned to the various circuits or other electrical devices disclosed, such labels are not intended to limit the scope of operation for the circuits and the other electrical devices. Such circuits and other electrical devices may be combined with each other and / or separated in any manner based on the particular type of electrical implementation that is desired. It is recognized that any circuit or other electrical device disclosed herein may include any number of microcontrollers, a graphics processor unit (GPU), integrated circuits, memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or other suitable variants thereof), and software which co-act with one another to perform operation(s) disclosed herein. In addition, any one or more of the electrical devices may be configured to execute a program code that is embodied in a non-transitory computer readable medium programmed to perform any number of the functions as disclosed.

[0042] In the following, embodiments of the invention will be described in detail with reference to the accompanying drawings. It is to be understood that the following description of embodiments is not to be taken in a limiting sense. The scope of the invention is not intended to be limited by the embodiments described hereinafter or by the drawings, which are taken to be illustrative only.

[0043] The drawings are to be regarded as being schematic representations and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose become apparent to a person skilled in the art. Any connection or coupling between functional blocks, devices, components, or other physical or functional units shown in the drawings or described herein may also be implemented by an indirect connection or coupling. A coupling between components may also be established over a wireless connection. Functional blocks may be implemented in hardware, firmware, software, or a combination thereof.

[0044] Hereinafter, techniques with respect to interference mitigation between a BSc transmission and an active transmission are disclosed. For sake of simplicity, it is hereinafter assumed that the active transmission is an Orthogonal Frequency Division Multiplex (OFDM) transmission, e.g., a downlink (DL) OFDM transmission from a base station (BS) of a wireless communication network, e.g., a cellular network (NW), to a UE connected to the cellular NW via the BS; an interference signal is superimposed on a signal of the OFDM transmission, or more generally affecting the signal of the OFDM transmission. “Superposition” refers to two or more signals being added together to form new signal that contains the characteristics of the two or more constituent signals. The UE thus receives a signal that has two constituents: first, the signal of the OFDM transmission; second the interference signal. The interference signal is caused by the BSc transmission. The BSc transmission may be between multiple nearby WDs. It would also be possible that the UE implements a receiving node of the BSc transmission.

[0045] FIG. 1 illustrates aspects with respect to a BSc transmission 190. FIG. 1 schematically illustrates a BSc communication system 160 (bi-static deployment) according to various examples. The bi-static BSc communication system 160 includes a BS 61 , a low-power WD 65, and a UE 69. In the scenario of FIG. 1 , the BS 61 implements a transmitting node 101 of the BSc transmission 190 as well as a control node 110 of the BSc transmission 190. The transmitting node 101 transmits an excitation signal 111 of the BSc transmission 190.

[0046] The low-power WD 65 implements a BSc node 105 of the BSc transmission 190. The excitation signal 111 is reflected and modulated to carry information, which yields an BSc signal 113. The UE 69 implements a receiving node 109 of the BSc transmission 190 that is configured to receive an BSc signal 113 and to demodulate the BSc signal 113, to retrieve the information.

[0047] FIG. 1 is only one example configuration of a communication system that can benefit from the techniques disclosed herein. Another scenario is illustrated in FIG. 2. In the BSc communication system 161 of FIG. 2 (mono-static deployment), the BS 61 implements, both, the transmitting node 101 as well as the receiving node 109 of the BSc transmission 190.

[0048] As a general rule, in the various disclosed examples, any of the deployment configurations illustrated in FIG. 1 in FIG. 2 may be used. It would also be possible to use deployment configurations not illustrated in FIG. 1 in FIG. 2, e.g., employing other WDs implementing the receiving node 109 and / or the transmitting node 101.

[0049] While in the scenarios of FIG. 1 and FIG. 2, the BS 61 implements the control node 110 of the BSc transmission 190, in other scenarios, other devices or nodes can implement the control node 110. Generally, the control node 110 can be responsible for configuring the BSc transmission 190; for instance, the control node 110 may configure sounding intervals, as will be described later in connection with, e.g., FIG. 9: block 3004. Accordingly, the control node 110 can determine a configuration and provide the configuration to the other nodes of the BSc transmission 190 and / or informs other WDs or nodes of the cellular NW accordingly. However, it is not required in all scenarios that a dedicated control node 110 is available. Thus, the control node 110 is optional. For instance, sometimes the transmitting node 101 or the receiving node 109 or the BSc node 105 may determine the configuration and optionally provide the configuration - e.g., as part of a control message - to one or more of the other nodes.

[0050] Furthermore, above, scenarios have been disclosed in which a dedicated transmitting node 101 of the BSc transmission 190 is present. That transmitting node 101 transmits a dedicated excitation signal 111 , having certain well-defined properties such as amplitude, polarization, etc. In other examples, an ambient excitation signal may be used. Here, a dedicated transmitting node 101 is not required. The ambient excitation signal does not have well-defined properties. Typically, a random polarization is observed. The amplitude may be random.

[0051] In FIG. 1 and FIG. 2, an interference signal 55 is superimposed on an OFDM signal 51 of an OFDM transmission 199. For instance, the OFDM transmission 199 may be between two WDs of the cellular NW. For instance, the OFDM transmission 199 may be an uplink (UL) or a downlink (DL) or a sidelink OFDM transmission. A particular scenario is illustrated in FIG. 3.

[0052] FIG. 3 schematically illustrates a deployment configuration for a BSc transmission 190 and an OFDM transmission 199. In this non-limiting example of FIG. 3, the BS 61 implements the transmitting node 101 of the BSc transmission 190. The low-power WD 65 implements the BSc node 105 of the BSc transmission 190 and the respective BSc signal 113 is received by the BS 61 , also implementing the receiving node 109 of the BSc transmission 190. Furthermore, the OFDM transmission 199 is a DL transmission from the BS 61 to another UE 59.

[0053] This deployment configuration is only one example and other deployment configurations are conceivable. For instance, it would be conceivable that the OFDM transmission 199 is an UL transmission to the BS 61. It would be possible that the receiving node 109 of the BSc transmission 190 is implemented by another UE or even the UE 59.

[0054] For sake of simplicity and generality, hereinafter, the following notation will be adhered:

[0055] TAB. 1 : Overview of terms used in the following description. Further, as will be appreciated from FIG. 3, the interference signal 55, in the illustrated scenario, equals the BSc signal 113 of the BSc transmission 190, but affected by the channel from the low-power WD 65 to the UE 59 (implementing the OFDM-RX WD).

[0056] Next, further aspects related to the BSc transmission 190 and the nature of the BSc signal 113 are explained. FIG. 4 illustrates an RF circuitry 313 of a WD capable of implementing a BSc node of a BSc transmission such as the BSc transmission 190. For instance, the wireless interface of the low-power WD 65 may include the RF circuitry 313. The RF circuitry 313 enables a passive spectrum access. An BSc signal 113 (obtained from the excitation signal picked-up via an antenna circuitry) is either absorbed (OFF-duration) or reflected (ON-duration). Reflection can be achieved by setting the switch 302 to the position in which it is connected to the impedance-mismatched load 321 ; in this scenario, there is an impedance mismatch between the antenna circuitry and the load 321 , leading to the reflection. Absorption can be achieved by setting the switch 302 to the position in which it is connected to the impedance-matched load 303. The switch is actuated by a circuitry 304 that applies an On-Off-Keying (OOK) modulation based on an incoming bitstream of BSc data 305 that represents the information to be communicated. In some cases, a reflective amplifier may be provided that can boost the reflected signal (not shown in FIG. 4). Then, not only OOK modulation is possible, but also Pulse Amplitude modulation. In general, Pulse Amplitude Modulation (PAM) may describe a modulation technique used to encode information onto a carrier signal by varying the amplitude of the pulses that make up the signal. In PAM, the amplitude of each pulse is proportional to the instantaneous value of the modulating signal, which in this case is the incoming bitstream of the BSc data 305 encoding the information to be communicated. The resulting modulated signal includes of a series of pulses with varying amplitudes, where the amplitude of each pulse represents a specific value or symbol from the original information signal. In the context of a backscattering transmission, PAM can be used in conjunction with a reflective amplifier to boost the reflected signal and improve the overall efficiency of the transmission.

[0057] FIG. 5 illustrates aspects related to the BSc signal 113. FIG. 5 illustrates modulation of the excitation signal 111 , denoted in FIG. 5 as c(t), depending on the BSc data 305 to be transmitted. FIG. 5 illustrates an OOK modulation. The patterns shown are merely examples, and other symbol constellations, repetition factors, etc. may be adopted. The BSc data 305 may be obtained from encoding upper-layer data using error-protection.

[0058] FIG. 6A, upper part illustrates multiple bands 605, 606, 607 occupied by the OFDM transmission 199. As illustrated in FIG. 6A, according to reference implementations, these bands 605, 606, 607 are interrupted by guard bands 608, 609; multiple carriers 611 , 612, 613 forming the excitation signal 111 of the BSc transmission 190 are located in the guard bands 608, 609. The resulting OOK modulation causes the BSc signal 113 to occupy certain frequency bands 621 , 622. The OOK modulation distorts the frequency content of the reflected BSc signal, and results in interference beyond the dedicated carriers 611 , 612. In the illustrated reference implementation, the frequency bands are residing in the guard bands 608, 609; i.e., the guard bands 608, 609 are sufficiently large so that the OFDM transmission 199 and the BSc transmission 190 are separated in frequency domain.

[0059] As will be appreciated, the larger the guard bands 608, 609, the smaller the available frequency bandwidth for the OFDM transmission 199.

[0060] According to various examples, the guard bands 608, 609 are not required altogether or smaller guard bands are sufficient, not fully separating, in the frequency domain, the band or bands of the OFDM transmission 199 on the one hand and that the BSc transmission 190 on the other hand. Such a scenario is illustrated in FIG. 6B. In FIG. 6B, the band 609 of the OFDM transmission 199 overlaps with the bands 621 , 622 of the BSc transmission 190. The OFDM transmission 199 and the BSc transmission 190 are not separated by guard bands.

[0061] In the scenario FIG. 6B, due to the overlap, in frequency domain, between the band 609 and the bands 621 , 622 of the BSc transmission 190, there is significant interference present in the signal received by the OFDM-Rx WD. To mitigate this, the OFDM-RX WD obtains information (interference mitigation information, IM information) for reducing an interference signal stemming from the BSc transmission 190 and superimposed on the received signal. This is explained in further detail below.

[0062] Various disclosed techniques are based on the finding that the data rate of the BSc transmission 190 is comparatively small in relation with the data rate of the OFDM transmission 199. However, the time duration, TIOT, for transmitting one bit may be on the order of one OFDM symbol duration, T0FDM, for the OFDM transmission 199. This implies that the data rate of the OFDM transmission 199 is, on the order of, N times that of the BSc transmission 190, where N is the number of subcarriers. Typically, N « 512 - 2048, so there is a substantial difference in rates. The larger the number of subcarriers, the larger the difference in rates. In some situations, TIOT» TQFDM . but this only amplifies the rate difference. In some scenarios, it may be that TIOT< T0FDM, in which case the rate-ratio is less than N. But even in this case, it is foreseeable that TIOT is a substantial fraction of TOFDM . say, I / 2or 1 / 3 which implies that the rate-ratio is N / 2 orN / 3. Thus, as will be appreciated, the data rate of the BSc transmission 190 is generally significantly smaller than the data rate of the OFDM transmission 199. This significantly smaller data rate of the BSc transmission 190 if compared to the OFDM transmission 199 enables that the OFDM-Rx WD is provided with the IM information that enables canceling the interference signal 55 form the received signal, by subtracting an estimated waveform of the interference signal 55 from the received waveform.

[0063] In detail, the BSc signal r(t) is decoded at the BSc-Rx WD. According to various examples, the BSc-RX WD generates the IM information for reducing an interference signal that is superimposed on a signal of the OFDM transmission 199. The OFDM-RX WD (cf. TAB. 1) may then obtain the IM Information from the BSc-RX WD.

[0064] As a general rule, such IM information may be included in one or more control messages that are obtained at the OFDM-RX WD. For instance, different control messages may include different parts of the IM information. For instance, a certain part of the IM information may be provided prior to a certain transmission interval during which interference occurs and for which that part of the IM information is then employed for reducing the interference. On the other hand, another part of the IM information may be provided during or after the certain transmission interval for which that part of the IM information is then employed for reducing the interference; in the latter scenario, the OFDM-RX WD may be required to buffer the OFDM signal received during the transmission interval until that part of the IM information becomes available.

[0065] For instance, control messages including (at least parts) of the IM information may be Layer 3 Radio Resource Control (RRC) control messages. It would also be possible to use Layer 2 Data Link Layer control messages.

[0066] The IM information may include an indication of the BSc signals transmitted during a certain interval. For instance, the BSc-RX WD may recreate the BSc data encoded by the BSc signal 113 and relay an indication of the BSc data to the OFDM-RX WD, as the IM information. The OFDM-RX WD is then able to reconstruct the transmitted BSc signals based on the data, e.g., using knowledge of the excitation signal of the BSc transmission, knowledge of one or more properties of a signal coding process of the BSc transmission 190, knowledge of the modulation of the BSc transmission employed at the low-power WD, e.g., the OOK symbols used, etc. In general, such and / or other transmitter properties employed by the low-power WD implementing the BSc node of the BSc transmission 190 may be indicated by the IM information, e.g., in a separate control message.

[0067] For instance, the low-power WD may employ error-correction encoding. In this case, the OFDM-RX WD may still require - for subsequent interference cancellation - the encoded data bits (including error protection), not the true information bits. It would be alternatively possible that the OFDM-RX WD has knowledge of the error protection process / coding properties.

[0068] Typically, providing such indication of the data encoded by the BSc signal 113 requires few resources as the data rate of the BSc transmission 190 is low on an absolute scale; in fact, it consumes less resources than those required for insertion of guard bands. Furthermore, since the data rate of the BSc transmission 190 is low also on a relative scale if compared to the data rate of the OFDM transmission 199, the latency of decoding the OFDM data is not significantly increased.

[0069] In some scenarios, the BSc-RX WD may pro-actively provide the IM information to the OFDM-RX WD - e.g., upon the OFDM-RX WD having indicated a need for interference mitigation assistance. Thus, it would be possible that the OFDM-RX WD once requests (ahead of any specific transmission interval during which the interference is present) the IM information. Such proactive request may request may then be valid for multiple transmission intervals. For example, such proactive request may be valid indefinitely, e.g., until revoked.

[0070] In other scenarios, the IM information may be provided by the BSc-RX WD only conditionally, e.g., on a case-by-case basis. For instance, the IM information indicative of the BSc signals 113 transmitted during the transmission interval may be requested by the OFDM-RX WD. For instance, such request for the IM information may be valid for a certain transmission interval. The request may be provided during or after the transmission interval. I.e., a case-by-case request may be provided. For instance, the OFDM-RX WD may provide a request, to the cellular NW, to provide the indication of the BSc signals. For instance, the OFDM-RX WD may request the IM information indicative of the BSc signals in a certain transmission interval instead of providing, to the OFDM-TX WD a negative acknowledgement (NACK) of an automatic repeat request (ARQ) scheme for that transmission interval. Thus, such request may be provided upon a failure of a decoding attempt of decoding the OFDM data. The request may delay a NACK of an ARQ scheme.

[0071] In general, an ARQ scheme may describe a protocol or technique used in digital communication systems for error detection and correction. It involves the receiver sending positive acknowledgments (PACKs) or NACKs to the transmitter based on whether received data packets are correct or contain errors. The PACKs and NACKs in the context of ARQ schemes are typically at the data link layer. Specifically, they are typically part of the Media Access Control (MAC) protocols that manage frame transmission and error detection / correction within a NW. To be more precise, these ACK / NACK messages are usually handled by the MAC sublayer, which is responsible for framing, error detection, and control of access to the physical medium.

[0072] For instance, in a scenario in which the IM information is not pro-actively provided, the OFDM-RX UE may try to decode the OFDM data without knowledge interference signal 55, i.e. , without knowledge of the BSc data encoded by the BSc signal r(t) 113. I.e., at the time of decoding the data encoded by the OFDM transmission 199, the OFDM-Rx WD may not have obtained that part of the IM information that enables to reconstruct the BSc signal 113. Such decoding attempt may be done blindly or by more sophisticated means. For example, the OFDM- Rx WD may test all possibilities of the BSc data (which are not very many as compared to the OFDM data) and decide the OFDM data for each one. The most likely signal may then be taken as output; this equates to a maximum likelihood decoding attempt. In a case where the error checksum of the OFDM data fails, the OFDM-Rx WD may request the IM information - instead of providing a NACK.

[0073] In general, maximum likelihood decoding attempt may describe an approach where the OFDM-RX WD attempts to determine the most probable received signal based on the observed channel outputs and prior knowledge of the transmission process. This method relies on statistical principles to, under assumption of equiprobable inputs, maximize the probability of correctly identifying the transmitted information. In the present case, the knowledge of the transmission process may include a guess of the backscattering signals; this guess may be in a relative limited result space, due to the limited data rate of the BSc transmission 190.

[0074] If the OFDM-RX WD has a channel estimate of the propagation channel from the low- power WD to the OFDM-RX WD (cf. FIG. 3), the OFDM-Rx WD may recreate the received waveform of r(t) - this is the interference signal 55 - and cancel it from the total received waveform during the transmission interval. Thus, the interference is mitigated. Naturally, there is a delay of at least one OFDM symbol, so the OFDM-RX WD buffers the received signal of the OFDM transmission 199 until it is able to cancel the interference signal 55.

[0075] Generally, canceling the interference signal from a signal may mean that a contribution of the interference signal in the signal is reduced or even completely removed.

[0076] Next, it is discussed how such channel estimate of the channel from the low-power WD to the OFDM-RX WD used to determine the interference signal 55 is obtained. This may be done in two stages: (A) initial estimation including a dedicated sounding procedure, and (B) tracking stage. Details are provided below.

[0077] In the (A) initial estimation stage, during a sounding interval, guard bands to separate the band(s) of the OFDM transmission 199 and the band(s) of the BSc transmission 190 may be used. It would - alternatively or additionally - be possible to temporarily silent the OFDM transmission 199. More generally, during the sounding intervals, the BSc signals are protected against interference from the OFDM transmission. The OFDM-Rx UE may be informed (e.g., upon request ) about properties of the BSc signal r(t), such as the backscatter pattern I modulation scheme and / or the location of the dedicated carriers of the BSc transmission 190. The low-power WD is either using a pilot BSc signal that is pre-defined and thus known to the OFDM-Rx UE or a symbol carrying data which is decoded by the BSc-Rx WD; then, an indication of the BSc data can be provided to the OFDM-Rx WD as part of the IM information. Based on a receive waveform of the BSc signals at the OFDM-RX WD and during the sounding interval, the OFDM-RX WD may then estimate the propagation channel from the low-power WD to the OFDM-RX WD. This is possible since the signal r(t) can be recreated based on the indicated properties and is not disturbed by the OFDM transmission.

[0078] Next, details of the (B) tracking stage are discussed. Assume that the OFDM-Rx UE has an earlier channel estimate of the interfering propagation channel (a-priori estimate; i.e., an estimate valid prior to the interference cancellation) and that the OFDM-Rx UE receives an OFDM signal to be decoded. The OFDM-Rx UE buffers such OFDM signal (e.g., a transport block) until it has been provided with the IM information indicative of the BSc data during the respective transmission interval. Once such IM information is available, the OFDM-Rx UE re-constructs the interference signal 55 based on the a-priori channel estimate and the BSc data. In other words: The UE determines an a-priori estimate of the interference signal. The OFDM-Rx UE then cancels the interference signal 55 from the total received signal. In other words: the a-priori estimate of the interference signal (i.e., a waveform) is subtracted from the received signal (i.e., another waveform). The OFDM-Rx UE next performs a decoding attempt, i.e., decodes the interference- canceled modified signal. If successful (i.e., error-checksums are ok), it is in turn possible to cancel the modified signal x(t) from the total received signal. The result is an a-posteriori estimate of the interference signal 55 (plus some noise); i.e., an estimate after the decoding attempt. The OFDM-Rx UE may then update its a-priori channel estimate based on that interference signal, by concluding back on the radio channel. In other words, the a-priori estimate of the radio channel is then replaced based on the a-posteriori estimate of the radio channel, for further use in subsequent interference cancellation processes. If, on the other hand, the error-checksums are not ok, then the OFDM-Rx UE may choose to request to move to (A) initial estimation stage. Thus, it would be possible to request, at the cellular NW, the sounding interval and / or an indication of the sounding interval (e.g., start time, stop time, duration etc.) and / or an indication of the BSc signals transmitted during the sounding interval. This may be responsive to a certain number of error-checksum fails so that the current channel estimate is outdated.

[0079] FIG. 7 schematically illustrates a WD 200 according to examples. For instance, the WD 200 may implement a BS of a cellular NW, e.g., the BS 61 as previously discussed. The WD 200 may implement a UE, e.g., the UE 69 or the UE 59 as previously discussed. The WD 200 may also implement a low-power WD such as the low-power WD 65 previously discussed. The WD 200 includes a processor 211 and a memory 212. The WD 200 also includes a communication interface 213. The communication interface 213 can include one or more RF transmitter and / or receiver elements. For instance, if the WD 200 engages in an active transmission, the communication interface 213 includes a DAC and / or an analog-to-digital converter, and (for transmitting) an RF signal source. If the WD 200 implements a BSc node of a BSc transmission, the communication interface may include RF circuitry as discussed in connection with FIG. 4. The processor 211 loads program code from the memory 212 and execute the program code. The processor, upon loading and executing the program code, performs techniques as disclosed herein. For instance, one or more of the methods disclosed below may be executed by the processor 211. FIG. 8 is a flowchart of a method according to various examples. The method of FIG. 8 is for use in a WD. The method of FIG. 8 is for use in an OFDM-RX WD. For instance, the method of FIG. 8 may be used in a UE, e.g., a smart phone, a handheld device, etc. The UE may be connected to a cellular NW through a serving BS. The method of FIG. 8 may be executed by a processor upon loading program code from a memory (cf. FIG. 7).

[0080] At box 3905, a signal is received. The signal is received from another WD. For instance, it would be possible that the WD that executes the method of FIG. 8 as well as the other WD are associated with the same cellular NW. For instance, it would be possible that a signal is received from the serving BS. The signal is received during a transmission interval.

[0081] As a general rule, in the disclosed scenarios, a transmission interval may define a certain duration or number of transmission units, e.g., transmission frames or subframes, etc. The transmission interval may define a transmission block. The transmission interval may define a number of symbols (e.g., OFDM symbols) that are jointly demodulated and / or decoded. A transmission interval may define an activity period of the low-power WD. e.g., a certain contiguous time span during which the low-power WD modulates the excitation signal of the BSc transmission.

[0082] The signal is received using an active transmission. An active transmission is different than a BSc transmission. This means that for the active transmission the node generating the RF signal is also modulating the RF signal. For instance, the active transmission may be an OFDM transmission. For instance, the active transmission may be a 3GPP NR transmission.

[0083] The signal encodes data, e.g., OFDM data. The data may be error protected. Alternatively or additionally, the data may be encrypted.

[0084] At box 3910, information for reducing an interference signal that is superimposed to the signal that is received at box 3905 is obtained. IM information is obtained.

[0085] The interference signal is superimposed on a signal during the same transmission interval for which the signal is received at box 3905. The interference signal as stemming from a BSc transmission. The BSc transmission is in the cellular NW. The BSc transmission is employing time and / or frequency resources subject to scheduling of the cellular NW. In particular, one or more active transmissions may and the BSc transmission may be subject to the same scheduling process.

[0086] The BSc transmission may be between other WDs; i.e. , in other words, it is possible that the WD that executes the method of FIG. 8 does not participate in the BSc transmission. In some scenarios, it would also be possible that the WD that executes the method of FIG. 8 participates in the BSc communication. For instance, the WD that executes the method of FIG. 8 may implement a receiving node of the BSc communication; i.e., the method of FIG. 8 may be executed by a WD that is both an OFDM-RX WD and a BSc-RX WD. In such case, it would be possible that obtaining the information at box 3910 is locally executed, i.e., without obtaining any control messages from other WDs. However, it would also be possible that obtaining the IM information at box 3910 includes obtaining one more control messages from the cellular NW, i.e., from one or other WDs.

[0087] As a general rule, even though box 3910 is illustrated to be executed after box 3905, it would be possible that at least parts of the IM information are obtained prior to receiving the signal at box 3905. In other words, it would be possible that box 3910 is executed prior to box 3905 or the box 3905 and box 3910 overlap.

[0088] For instance, if obtaining the IM information includes obtaining one or more control messages from the cellular NW, then it would be possible that at least one of the one or more control messages is obtained prior to the transmission interval during which the signal is received at box 3905 and / or it would be possible that at least one of the one or more control messages is obtained during or after the transmission interval.

[0089] FIG. 9 is a flowchart of a method according to various examples. The method of FIG. 9 is for use in a WD. For instance, the method of FIG. 9 may be used in a UE, e.g., a smart phone, a handheld device, etc. The method of FIG. 9 may be executed by a processor upon loading program code from a memory.

[0090] The method of FIG. 9 is a specific implementation of the method of FIG. 8 according to various examples.

[0091] The method of FIG. 9 may be executed by an OFDM-RX WD.

[0092] For sake of simplicity, it is assumed that the method of FIG. 9 is executed by a UE that receives, from a serving BS of a cellular NW, OFDM signals of a DL OFDM transmission. It would, however, be possible that the method of FIG. 9 is executed by, e.g., a BS.

[0093] The DL OFDM transmission (cf. OFDM transmission 199) suffers from interference from a BSc transmission (cf. BSc transmission 190). A low-power WD is in the vicinity of the UE. An interference signal stemming from the BSc transmission is superimposed on the OFDM signal, during a certain transmission interval. Thus, the received signal in a certain transmission interval includes a first contribution from the OFDM transmission and a second contribution from the BSc transmission. The interference signal is the BSc signal of the BSc transmission affected by the radio channel from the low-power WD to the UE.

[0094] At block 3004, an initial estimate of that radio channel is determined. A sounding procedure is executed at block 3004. Block 3004 includes boxes 3005, 3010, 3015, and 3020.

[0095] At box 3005, the UE obtains a control message from the cellular NW, e.g., from a serving BS, that is indicative of an indication of a sounding interval. This control message may be part of IM information for reducing interference from the BSc transmission. For instance, a start time and / or stop time of the sounding interval may be signaled. Start time and / or stop time may be expressed in terms of frame numbers of transmission frames or otherwise.

[0096] At box 3010 - this box is generally optional -, the UE may obtain an indication of BSc signals that are transmitted during the sounding interval. For instance, the UE may specifically request such information (not shown in FIG. 9).

[0097] Then, the sounding interval commences and, at box 3015, the UE receives the BSc signals. Those BSc signals are protected against interference from the OFDM transmission. This means that the BSc signals that are received at box 3015 are not (significantly) interfered with OFDM signals of the OFDM transmission. Such protection can be achieved by provisioning guard bands and separating the OFDM transmission from the BSc transmission in frequency domain (e.g., as discussed previously in connection with FIG. 6A) and / or temporarily muting the OFDM transmission during the sounding interval. Then, at box 3020, the UE determines a channel estimate of the radio channel from the low-power WD to the UE. This is based on the receive waveform of the BSc signals received at box 3015, i.e., transmitted during the sounding interval. In particular, the receive waveform of the BSc signals reflects the initial transmit waveform of the BSc signal plus the radio channel. Because the initial transmit waveform of the BSc signals is known from the indication of box 3010 or because predefined pilot BSc signals are transmitted (in this case box 3010 may not be required, since the pilot BSc signals are anyway known), it is possible to conclude back on the radio channel. This completes the sounding procedure of blocks 3004. The channel estimate may be labeled “a-priori” channel estimate, because it is determined prior to a transmission interval and an associated decoding attempt.

[0098] At box 3025, the UE receives - during the transmission interval - an OFDM signal that encodes OFDM data. The UE buffers the received OFDM signal. I.e., the UE does not immediately attempt decoding the OFDM signal.

[0099] At box 3030, the UE obtains an indication of BSc signals of the BSc transmission that are transmitted during the transmission interval. Such control message may be part of IM information for reducing interference from the BSc transmission.

[0100] Box 3030 is typically executed after the end of the transmission interval. For instance, the IM information obtained at box 3030 can include an indication of BSc data (i.e., a sequence of data bits) that is encoded by the BSc signals transmitted during the transmission interval. Alternatively or additionally, the IM information may include one or more transmitter properties of the low-power WD implementing the BSc node and used for transmitting the BSc signals during the transmission interval. Examples include one or more properties of an excitation signal of the BSc transmission, e.g., carrier frequencies, amplitude, etc.; one or more properties of a modulation scheme of the BSc transmission; and / or one or more properties of a signal coding process of the BSc transmission. Based on such transmitter properties and the knowledge of the BSc data, it is possible to reconstruct the BSc signal. Then, based on the BSc signal and the a- priori channel estimate obtained from box 3020, at box 3035, an (a-priori) estimate of the interference signal is determined.

[0101] At box 3040, the interference signal can be canceled from the signal received at box 3025 (this signal is in a buffer, as explained above). I.e., the waveform of the interference signal can be subtracted from the received waveform. This is based on the respective a-priori estimate. This operation yields a modified signal that ideally includes a reduced interference from the BSc transmission (assuming that the a-priori channel estimate is still up-to-date).

[0102] At box 3041 , a decoding attempt of decoding the OFDM data from the modified signal is executed. The decoding attempt may include OFDM demodulation.

[0103] In general, OFDM demodulation may describe the process of extracting the original data from an OFDM signal that has been received. This involves reversing the modulation process used to transmit the data over multiple subcarriers in the frequency domain. During OFDM demodulation, the received signal is processed to separate the individual subcarriers and extract the original data symbols from each subcarrier. The demodulated data symbols are then reassembled into a single stream of OFDM data, which can be further processed for error correction, decoding, and other post-processing operations. At box 3045, it is determined whether the decoding attempt at box 3041 is successful. For instance, error protection techniques can be employed in a checksum (CRC) can be determined and verified. If the decoding was unsuccessful, this can have multiple reasons: for instance, significant interference (from arbitrary sources) can be present on the radio channel from the BS to the UE and impact the OFDM transmission. It would also be possible that the a-priori channel estimate of the radio channel from the low-power WD of the UE is outdated so that the interference mitigation at box 3040 yields poor results.

[0104] For decoding success, the method commences at box 3055. Here, it would be possible to send a PACK of an ARQ scheme. The PACK can signal, to the BS implementing the OFDM-TX WD, that the OFDM data was successfully decoded.

[0105] It would also be possible at box 3060, to determine an a-posteriori channel estimate of the radio channel from the low-power WD to the UE. For this, the modified signal obtained from box 3040 (only including the contribution of the OFDM signal transmitted by the BS as well as the radio channel from the BS to the UE; but not including significant interference from the BSc transmission) is canceled from the signal originally received at box 3025 (buffered until this point); this operation yields an a-posteriori estimate of the interference signal. Then, the a-posteriori estimate of the radio channel from the low-power WD to the UE can be determined based on that a-posteriori estimate of the interference signal. In particular, because the interference signal is the transmitted waveform of the BSc signal plus the radio channel and the transmitted waveform is known (cf. box 3030), it is possible to conclude back on the radio channel. This a-posteriori estimate of the radio channel (determined after successful decoding) can be used in a further decoding attempt for a subsequent transmission interval (at this occasion, it is labeled “a-priori estimate” again).

[0106] If the decoding is unsuccessful at box 3045, at box 3050 it would be possible to transmit a NACK of the ARQ scheme to the BS.

[0107] Box 3050 is only one example. In detail, instead of directly transmitting the NACK at box 3050, a more complicated procedure may be executed that attempts to correct the a-priori channel estimate of the radio channel from the low-power WD to the UE using a sounding procedure, prior to transmitting the NACK. For instance, the procedure according to FIG. 10 could be executed upon determining, at box 3045 of FIG. 9 that the decoding was unsuccessful.

[0108] In FIG. 10, at box 3805, it is determined whether a further iteration 3804 is to be executed, prior to transmitting the NACK at box 3806 ("no"-branch exiting box 3805).

[0109] Various decision criteria can be employed in box 3805. For instance, at box 3805, it can be checked whether the number of previous iterations 3804 exceeds a certain predefined threshold. It would also be possible to make dynamic judgements based on, e.g., a mobility level of the UE and / or channel state information for the radio channel from the BS to the UE.

[0110] In each iteration 3804, the UE (or more generally the OFDM-RX WD) initially requests, at box 3810, a sounding procedure, e.g., by transmitting a respective control message to the cellular NW, e.g., to the serving BS. The UE may even request a specific sounding interval and / or an indication of the BSc signals.

[0111] Then, at box 3815, the sounding procedure is executed. Box 3815 can correspond to block 3004 as previously discussed in connection with FIG. 9. The outcome of box 3815 is an updated estimate of the radio channel from the low-power WD to the UE. Box 3820 then corresponds to box 3035, wherein the updated estimate of the radio channel is employed. Box 3825 corresponds to box 3040 and box 3830 corresponds to box 3041.

[0112] At box 3835, the current decoding success can be judged. If decoding was successful, the PACK may be transmitted at box 3840. If decoding was unsuccessful, a further iteration 3804 above 3805 is executed.

[0113] FIG. 11 is a flowchart of a method according to various examples. The method of FIG. 11 is for use in a WD. For instance, the method of FIG. 11 may be used in a UE, e.g., a smart phone, a handheld device, etc. The method of FIG. 11 may be executed by a processor upon loading program code from a memory.

[0114] The method of FIG. 11 is a specific implementation of the method of FIG. 8 according to various examples.

[0115] Further, the method of FIG. 11 is a variant of the method of FIG. 9. In the method of FIG. 11 , the pre-emptive sounding procedure (block 3004 in FIG. 9) is dispensed with. This may further reduce signaling overhead, at least for relatively stable channel conditions.

[0116] Box 3105 corresponds to box 3025. Box 3110 corresponds to box 3030. Box 3115 corresponds to box 3035. At box 3115, an a-priori channel estimate otherwise available is employed, e.g., from an earlier point in time or a preceding transmission interval. Box 3120 then corresponds to box 3040 and box 3121 corresponds to box 3041. Box 3125 corresponds to box 3045. If decoding is judged to be successful, box 3155 is executed. Box 3155 corresponds to box 3055. Then, it would be optionally possible to execute box 3160 corresponding to box 3060. If, on the other hand, decoding is judged, at box 3125, to not be successful, the procedure of FIG. 10 can follow.

[0117] FIG. 12 is a flowchart of a method according to various examples. The method of FIG. 12 is for use in a WD. For instance, the method of FIG. 12 may be used in a UE, e.g., a smart phone, a handheld device, etc. The method of FIG. 12 may be executed by a processor upon loading program code from a memory.

[0118] The method of FIG. 12 is a specific implementation of the method of FIG. 8 according to various examples.

[0119] The method of FIG. 12 is a variant of the method of FIG. 11. In the method of FIG. 12, the UE does not obtain an indication of the BSc signals prior to the first decoding attempt. This may further reduce signaling overhead, at for transmission intervals that are sufficiently short (i.e. , the number of candidates of BSc signals is relatively small).

[0120] In FIG. 12, box 3205 corresponds to box 3105.

[0121] The method then commences at box 3215, where the UE determines one or more estimates of the interference signal, e.g., for one or more guesses of the BSc signals. For instance, the UE make one or more guesses of BSc data and re-created respective BSc signals. This is sometimes possible, because the data rate and, accordingly, the number of variants of the BSc signals is limited.

[0122] Box 3220 then corresponds to box 3120; wherein in box 3220 the UE cancels each of the one or more a-priori estimates of interference signals of box 3215 from the received signal of box 3205. At box 3221 - corresponding to box 3121 - the UE then makes respective decoding attempts. At box 3225, it is determined whether any of the one or more decoding attempts of box 3221 was successful; in the affirmative, box 3255 and optionally box 3260 - corresponding to boxes 3155 and 3160 - are executed. Otherwise, the method commences at box 3230.

[0123] At box 3230, the UE provides, to the cellular NW- e.g., to the serving BS -, a request to provide the indication of the BSc signals transmitted during the transmission interval of box 3205. i.e., the request is provided after the transmission interval, the The request is provided upon a failure of the decoding attempt of decoding the data.

[0124] Then, the UE obtains at box 3231 , the indication of the BSc signals; box 3231 , accordingly, corresponds to box 3110 of the method of FIG. 11. It would also be possible that, at box 3231 , the UE obtains an indication of any changes to one or more transmitter properties of the low- power WD. For instance, the excitation signal may have changed. It would be possible that the transmission mode has been switched, e.g., from OOK modulation of pulse amplitude modulation.

[0125] Then, box 3235 is executed; here, a new estimate of the interference signal is determined, employing the knowledge on the BSc signal is obtained at box 3231. Box 3240 and box 3245 then correspond to box 3220 and box 3221 , respectively. At box 3250, it can be judged whether the decoding attempt was successful; if not, it would be possible to execute the process of FIG. 10, to update the channel estimate.

[0126] It is noted that the method of FIG. 12 may be modified in various manners. For instance, a sounding procedure may be executed ahead of box 3205, e.g., as previously discussed in connection with box 3005 preceding box 3025 in the method of FIG. 9.

[0127] FIG. 13 is a signaling diagram of communication between the BS 61 , the low-power WD 65 and the UE 59. FIG. 13 illustrates signaling for a deployment scenario is illustrated in FIG. 3. I.e., the low-power WD 65 implements a BSc node of a BSc transmission 190 that interferes with a downlink OFDM transmission 199 from the BS 61 (OFDM-TX WD) to the UE 59 (OFDM-RX WD). The BS 61 may implement a receiving node of the BSc transmission (BSc-RX WD), or, at least, a control node 110 of the BSc transmission 190.

[0128] The signaling diagram of FIG. 13 pertains to a sounding procedure for sounding the channel from the low-power WD 65 to the UE 59. For instance, the signaling of FIG. 13 may implement block 3004 of FIG. 9.

[0129] At 5005, the UE 59 provides a request 4005 to the BS 61 . The request 4005 requests the sounding procedure. For instance, the request could be provided upon a negative decoding attempt of decoding OFDM data (cf. FIG. 10: box 3810).

[0130] The BS 61 then provides a configuration message 4010 to the low-power WD 65, at 5010. This configuration message 4010 informs the low-power WD 65 of the sounding procedure, e.g., includes a start time and / or stop time of the sounding interval. Furthermore, it would be possible that the configuration message 4010 requests the low-power WD 65 to transmit pilot BSc signals 113 during the sounding interval 905 (rather than BSc signals encoding, e.g., Layer 3 or higher- layer BSc data).

[0131] Then, a respective configuration message 4015 is provided by the BS 61 to the UE 59 at 5015. Again, the configuration message 4015 can inform the UE 59 of the start and / or stop time of the sounding interval. The configuration message 4015 may inform the UE 59 that the low- power WD 65, during the sounding interval 905, will transmit pilot BSc signals 4025. Then, the sounding interval 905 commences. It is optionally possible that the BS 61 , during the sounding interval 905, transmits OFDM signals 51 encoding OFDM data, at 5020. Alternatively, it would also be possible to mute the OFDM transmission 199 during the sounding interval 905, to protect the BSc signals 413 from interference from the OFDM transmission 199. During the sounding interval 905, the low-power WD 65 modulates the excitation signal 111 , so that the BSc signals 113 are transmitted at 5025. The UE 59 can then measure these BSc signals 4025, as previously explained in connection with box 3015 in FIG. 9. If pilot BSc signals 113 are used, these are already known to the UE 59. Otherwise, it would be possible to provide an indication of the BSc data encoded by the BSc signals 113 transmitted during the sounding interval 905 to the UE 59 (not shown).

[0132] Note that the pilot BSc signals 113 may also be measured by the BS 61 ; this enables the BS 61 to sound the radio channel from the low-power WD 65 to the BS 61.

[0133] FIG. 14 is a signaling diagram of communication between the BS 61 , the low-power WD 65 and the UE 59. FIG. 14 illustrates signaling for the same deployment scenario discussed in connection with FIG. 13 above.

[0134] In FIG. 14, the band(s) of the BSc transmission 190 overlap with the band(s) of the OFDM transmission 199. Guard bands are not used; or, if guard bands are used, they are smaller than the guard bands used, e.g., in FIG. 13.

[0135] The signaling of FIG. 14 may implement box 3025 and box 3030 of the method of FIG. 9. During a transmission interval 906, the BS 61 transmits OFDM signals 51 that carry OFDM data, at 5105. Concurrently, the BSc transmission 190 takes place, i.e., the low-power WD 65 transmits a BSc signal 113, at 5111 ; for this, the low-power WD 65 modulates the excitation signal 111.

[0136] In the illustrated scenario, the BS 61 implements the receiving node of the BSc transmission 190 and receives the information-carrying BSc signal 113. However, the BSc signal 113 also is received at the UE 59, here in form of an interference signal 55, superimposed on the OFDM signal 51.

[0137] At 5115, the BS 61 sends a control message 4125 (e.g., a Layer 1 or Layer 2 control message, to have low latency) that is obtained by the UE 59. The control message 5115 includes an indicator indicative of the BSc data encoded by the BSc signal 113, as previously explained in connection with box 3030 of the method of FIG. 9.

[0138] In the scenario of FIG. 14, the provisioning of the control message 4125 at 5115 is proactively triggered by reception of the BSc signal 113 and the subsequent decoding of the BSc data at the BS 61 , implementing the BSc-RX WD. This is only one option. A variant is illustrated in FIG. 15.

[0139] FIG. 15 is a signaling diagram of communication between the BS 61 , the low-power WD 65 and the UE 59. FIG. 15 illustrates signaling for the same deployment scenario discussed in connection with FIG. 14 above.

[0140] The signaling of FIG. 15 generally corresponds to the signaling of FIG. 14. However, in FIG. 15 a variant with respect to the control message 4125 is illustrated.

[0141] At 5190, a decoding attempt is executed (cf. FIG. 12: box 3221); decoding of the OFDM data carried by the OFDM signal 51 that is received at 5105 fails (cf. FIG. 12, box 3225; "no"- branch) and, accordingly, the UE 59, at 5212 provides a request 4230 to the BS 61 , the request 4230 requesting provisioning of an indication of the BSc signal 113 (cf. FIG. 12: box 3230).

[0142] Thus, at 5215, the BS 61 provides the control message 4125 that includes the indicator indicative of the BSc data to the UE 59; the control message 4125 is only provided upon request.

[0143] In the illustrated example of FIG. 15, a further unsuccessful decoding attempt occurs at 5191 and, accordingly, the UE 59 and provides a NACK 4235 to the BS (cf. FIG. 10: box 3806).

[0144] The scenario FIG. 15 has the advantage that the decoding attempt at 5190 is not delayed until obtaining the control message 4125. Thus, the overall latency of the OFDM transmission 199 may be slightly reduced.

[0145] FIG. 16 is a signaling diagram of communication between the BS 61 , the low-power WD 65 and the UE 59. FIG. 16 illustrates signaling for the same deployment scenario discussed in connection with FIG. 14 above.

[0146] The signaling of FIG. 16 may implement box 3025 and box 3030 of the method of FIG. 9.

[0147] The signaling of FIG. 16 is a variant of the signaling of FIG. 14. In particular, the UE 59 provides a request 4505 ahead of the transmission interval 906. The request 4505 is for providing the IM information that is indicative of the BSc data; the respective control message 4125 is then provided later on, after the transmission interval 906, at 5515 (without being requested during or after the transmission interval 906). Other than that, 5505 corresponds to 5105; 5511 corresponds to 5111. The request 4505 can be valid for any subsequent transmission interval 906 during which, both, the BSc transmission 190 and the OFDM transmission 199 are concurrently active; for instance, the request may be valid until revoked.

[0148] FIG. 17 is a flowchart of a method according to various examples. The method of FIG. 17 is for use in a WD. The method of FIG. 17 is for use in an OFDM-TX WD. For instance, the method of FIG. 17 may be used in a BS of a cellular NW, e.g., the BS 61 . The BS may serve a UE. The method of FIG. 17 may be executed by a processor upon loading program code from a memory (cf. FIG. 7).

[0149] The method of FIG. 17 is inter-related with the method of FIG. 8.

[0150] At box 8905, the WD transmits a signal using an active transmission, e.g., an OFDM transmission, to another WD (e.g., a UE). For instance, a DL signal encoding data, e.g., Layer 3 data or higher-layer data, may be transmitted to the UE. Box 8905 is inter-related with box 3905 of the method of FIG. 8.

[0151] At box 8910, the WD provides IM information to another WD. The IM information is for mitigating interference present in the OFDM signal received at another WD. That interference stems from a BSc transmission. Box 8910 is intra-related with box 3910.

[0152] Providing the IM information may include transmitting one or more control messages. Providing the IM information may be, at least partly, upon request. Various scenarios of providing such IM information have been discussed above from the perspective of the recipient obtaining that information; these scenarios are equally applicable to box 8910.

[0153] For instance, considering that the method of FIG. 17 is executed by a BS, the BS may also implement the receiving node of the backscattering transmission (cf. deployment scenario of FIG. 3; also cf. FIG. 2). In such case, the BS can readily generate the IM information. For instance, the BS has knowledge of the BSc data upon decoding the received BSc signal. However, scenarios are conceivable in which the BS or, more generally, the WD executing the method of FIG. 17, does not implement the receiving node of the BSc transmission. In such a scenario, the WD implementing the method of FIG. 17 may obtain the IM information from the WD implementing the receiving node of the backscattering transmission and then relay that IM information to the another WD. It would also be possible that the WD implementing the method of FIG. 17 implements a control node of the backscattering transmission (cf. FIG. 1 and FIG. 2 where the BS 61 implements a control node 110 of the BSc transmission 190).

[0154] Summarizing, techniques for mitigating interference from a BSc transmission in an OFDM transmission have been disclosed. This involves obtaining, at an OFDM-RX WD, IM information for mitigating interference present in a received OFDM signal. The IM information is indicative of BSc data encoded by a BSc signal transmitted concurrently with the OFDM signal by a another low-power WD. The BSc transmission interferes with the OFDM transmission. By employing the IM information, an estimate of an interference signal can be determined and canceled from the received OFDM signal, thereby improving decoding performance of the OFDM data. Typically, the loss of having to provide the IM information to the OFDM-RX WD is smaller than the associated loss of introducing a guard band. To perform interference cancellation, channel state information is required. Details of determining an estimate of the radio channel from the low-power WD to the OFDM-RX WD are disclosed.

[0155] According to various examples, a BS may provide decoded data from an AIOT device to an NR device suffering from interference caused by said AIOT device. The BS may indicate operations of the AIOT device, including its backscattering pattern and location of dedicated carriers.

[0156] In some example, the BS sends the AIOT data to the NR device.

[0157] In some examples, the BS sends the AIOT data only upon request, implementing a low overhead version of HARQ (Hybrid Automatic Repeat Request). This approach enables efficient communication while minimizing unnecessary transmissions.

[0158] Summarizing, at least the following EXAMPLES have been disclosed.

[0159] EXAMPLE 1. A method for use in a wireless communication device (59) associated with a wireless communication network, the method comprising:

[0160] - during a transmission interval (906) and using an active transmission (199), receiving (3905) a signal (51) from another wireless communication device (61) associated with the wireless communication network, and

[0161] - obtaining (3910) information for reducing an interference signal (55) affecting the signal (51) during the transmission interval (906), the interference signal (55) stemming from a backscattering transmission (190).

[0162] EXAMPLE 2. The method of EXAMPLE 1 , wherein the information for reducing the interference signal (55) comprises an indication of a sounding interval (905) before or after the transmission interval (906).

[0163] EXAMPLE S. The method of EXAMPLE 2, wherein backscattering signals (113) of the backscattering transmission (190) transmitted by a backscattering device (65) of the backscattering transmission (190) are protected against interference from the active transmission (199) during the sounding interval (905), to thereby enable the wireless communication device (59) to determine, based on a receive waveform of the backscattering signals (113) transmitted during the sounding interval (905), an estimate of a radio channel from the backscattering device (65) to the wireless communication device (59).

[0164] EXAMPLE 4. The method of EXAMPLE 3, wherein the information for reducing the interference signal (55) comprises an indication of the backscattering signals transmitted during the sounding interval.

[0165] EXAMPLE S. The method of EXAMPLE 4, wherein the backscattering signals (113) transmitted by the backscattering device (65) during the sounding interval (905) comprise predefined pilot backscattering signals.

[0166] EXAMPLE 6. The method of any one of EXAMPLES 2 to 5, further comprising:

[0167] - providing, to the wireless communication network, a request (4005) for at least one of the sounding interval, the indication of the sounding interval, or an indication of backscattering signals transmitted during the sounding interval.

[0168] EXAMPLE 7. The method of any one of the preceding EXAMPLES, wherein the information for reducing the interference signal (55) comprises an indication of backscattering signals (113) transmitted by a backscattering device (65) of the backscattering transmission (190) during the transmission interval (906).

[0169] EXAMPLE 8. The method of EXAMPLE 7, wherein the indication of the backscattering signals (113) transmitted during the transmission interval comprises an indication (4125) of data (305) encoded by the backscattering signals (113) transmitted during the transmission interval (906).

[0170] EXAMPLE 9. The method of EXAMPLE 7 or 8, wherein the indication of the backscattering signals (113) transmitted during the transmission interval (906) comprises one or more transmitter properties of the backscattering device (65) used for transmitting the backscattering signals (113) during the transmission interval (906).

[0171] EXAMPLE 10. The method of EXAMPLE 9, wherein the one or more transmitter properties are selected from the group comprising: one or more properties of an excitation signal (111) of the backscattering transmission (190); one or more properties of a modulation scheme of the backscattering transmission (190); or one or more properties of a signal coding process of the backscattering transmission (190).

[0172] EXAMPLE 11 .The method of any one of EXAMPLES 7 to 10, further comprising:

[0173] - providing, to the wireless communication network, a request (4230, 4505) to provide the indication of the backscattering signals (113) transmitted during the transmission interval (906).

[0174] EXAMPLE 12. The method of EXAMPLE 11 , wherein the request (4505) for providing the indication of the backscattering signals (113) transmitted during the transmission interval (906) is provided ahead of the transmission interval (906) and is valid for multiple transmission intervals.

[0175] EXAMPLE 13. The method of EXAMPLE 11 , wherein the request (4230) for providing the indication of the backscattering signals (113) transmitted during the transmission interval (906) is provided during or after the transmission interval (906) and is valid only for that transmission interval (906). EXAMPLE 14. The method of EXAMPLE 13, wherein the request for providing the indication of the backscattering signals transmitted during the transmission interval is provided upon a failure of a decoding attempt of decoding data encoded by the signal (51).

[0176] EXAMPLE 15. The method of any one of the preceding EXAMPLES, wherein said obtaining of the information for reducing the interference signal (55) comprises obtaining one or more control messages (4015, 4125, 4225) from the wireless communication network.

[0177] EXAMPLE 16. The method of EXAMPLE 15, wherein at least one (4015) of the one or more control messages is obtained prior to the transmission interval (906).

[0178] EXAMPLE 17. The method of EXAMPLE 15 or 16, wherein at least one (4125, 4225) of the one or more control messages is obtained during or after the transmission interval (906).

[0179] EXAMPLE 18. The method of any one of the preceding EXAMPLES, further comprising:

[0180] - buffering the signal received during the transmission interval (906) until the information for reducing the interference signal (55) is obtained.

[0181] EXAMPLE 19. The method of any one of the preceding EXAMPLES, further comprising:

[0182] - based on an a-priori radio channel estimate of a radio channel from a backscattering device (65) of the backscattering transmission (190) to the wireless communication device (59), determining an a-priori estimate of the interference signal (55),

[0183] - based on the a-priori estimate of the interference signal (55), canceling the interference signal (55) from the signal (51), to obtain a modified signal, and

[0184] - performing a decoding attempt for decoding data from the modified signal.

[0185] EXAMPLE 20. The method of EXAMPLE 19,

[0186] - upon success of the decoding attempt for decoding the data from the modified signal: canceling the modified signal from the signal, to obtain an a-posteriori estimate of the interference signal, and

[0187] - determining an a-posteriori estimate of the radio channel from the backscattering device to the wireless communication device based on the a-posteriori estimate of the interference signal.

[0188] EXAMPLE 21 .The method of EXAMPLE 19 or 20, wherein the a-priori estimate interference signal is further determined based on at least one of an indication or a guess of backscattering signals transmitted by the backscattering device during the transmission interval.

[0189] EXAMPLE 22. The method of EXAMPLE 21 , further comprising:

[0190] - upon failure of the decoding attempt based on the guess of the backscattering signals, requesting the indication of the backscattering signals transmitted during the transmission interval.

[0191] EXAMPLE 23. The method of any one of the preceding EXAMPLES, wherein the wireless communication device is a user equipment connected to the wireless communication network through a base station, wherein the active transmission is a downlink Orthogonal Frequency Division Multiplex transmission from the base station to the user equipment.

[0192] EXAMPLE 24. A method for use in a wireless communication device associated with a wireless communication network, the method comprising:

[0193] - during a transmission interval (906) and using an active transmission (199), transmitting (8905) a signal to another wireless communication device associated with the wireless communication network, and

[0194] - providing (8910), to another wireless communication device, information for reducing an interference signal affecting the signal during the transmission interval, the interference signal stemming from a backscattering transmission.

[0195] EXAMPLE 25. The method of EXAMPLE 24, wherein the wireless communication device is a base station of a wireless communication network, wherein another wireless communication device is a user equipment connected through the wireless communication network through the base station, wherein the active transmission is a downlink Orthogonal Frequency Division Multiplex transmission from the base station to the user equipment.

[0196] EXAMPLE 26. The method of EXAMPLE 24 or 25, wherein the wireless communication device implements a control node of the backscattering transmission.

[0197] EXAMPLE 27. The method of any one of EXAMPLES 24 to 26, wherein the wireless communication device implements a receiving node of the backscattering transmission.

[0198] EXAMPLE 28. A wireless communication device (59) for association with a wireless communication network, the wireless communication device comprising a processor and a memory, the processor being configured to load program code from the memory and to execute the program code, the processor, upon loading and executing the program code, being configured to:

[0199] - during a transmission interval (906) and using an active transmission (199), receive (3905) a signal (51) from another wireless communication device (61) associated with the wireless communication network, and

[0200] - obtain (3910) information for reducing an interference signal (55) affecting the signal (51) during the transmission interval (906), the interference signal (55) stemming from a backscattering transmission (190).

[0201] EXAMPLE 29. The wireless communication device (59) of EXAMPLE 28, wherein the processor, upon loading and executing the program code, is configured to perform the method of any one of EXAMPLES 1 to 23.

[0202] EXAMPLE 30. A wireless communication device for association with a wireless communication network, the wireless communication device comprising a processor and a memory, the processor being configured to load program code from the memory and to execute the program code, the processor, upon loading and executing the program code, being configured to: - during a transmission interval (906) and using an active transmission (199), transmit (8905) a signal to another wireless communication device associated with the wireless communication network, and

[0203] - provide (8910), to another wireless communication device, information for reducing an interference signal affecting the signal during the transmission interval, the interference signal stemming from a backscattering transmission.

[0204] EXAMPLE 31. The wireless communication device of EXAMPLE 30, wherein the processor, upon loading and executing the program code, is configured to perform the method of any one of EXAMPLES 24 to 27.

[0205] Although the invention has been shown and described with respect to certain preferred embodiments, equivalents and modifications will occur to others skilled in the art upon the reading and understanding of the specification. The present invention includes all such equivalents and modifications and is limited only by the scope of the appended claims.

[0206] For illustrative purposes, while scenarios have been disclosed in the context of an implementation of the active transmission by an OFDM transmission, The concepts disclosed for OFDM transmissions can be extended not only to other types of active transmission, but also to various modulation schemes and access methods. For instance, the interference mitigation techniques can be applied to Single Carrier Frequency Division Multiple Access (SC-FDMA) transmissions, which are used in uplink communications in 3GPP 4G NWs. In SC-FDMA, a single carrier is modulated by a block of data, similar to OFDM, but with a single-carrier waveform.

[0207] For further illustration, while techniques have been disclosed for a BS that implements, both, a receiving node of the backscattering transmission as well as a transmitting node of the active transmission, as a general rule, the receiving node of the BSc transmission and the transmitting node of the active transmission may be implemented by different WDs. Then, these two WDs may communicate with each other, to enable the IM information to be delivered to the WD that implements the receiving node of the active transmission. This also means that the IM information may be generated by another WD of the cellular NW than the WD transmitting the signal that is then modified based on the IM information.

[0208] For still further illustration, above, scenarios have been disclosed for a wireless communication NW implemented by a cellular NW. A cellular NW generally describes A type of wireless communication NW that provides wireless connectivity over a wide geographic area that is divided into “cells” served by individual BSs.

Claims

C L A I M S1 . A method for use in a wireless communication device associated with a wireless communication network, the method comprising:- during a transmission interval and using an active transmission, receiving a signal from another wireless communication device associated with the wireless communication network, and- obtaining information for reducing an interference signal affecting the signal during the transmission interval, the interference signal stemming from a backscattering transmission.

2. The method of claim 1 , wherein the information for reducing the interference signal comprises an indication of a sounding interval before or after the transmission interval.

3. The method of claim 2, wherein backscattering signals of the backscattering transmission transmitted by a backscattering device of the backscattering transmission are protected against interference from the active transmission during the sounding interval, to thereby enable the wireless communication device to determine, based on a receive waveform of the backscattering signals transmitted during the sounding interval, an estimate of a radio channel from the backscattering device to the wireless communication device.

4. The method of claim 1 , wherein the information for reducing the interference signal comprises an indication of backscattering signals transmitted by a backscattering device of the backscattering transmission during the transmission interval.

5. The method of claim 4, wherein the indication of the backscattering signals transmitted during the transmission interval comprises an indication of data encoded by the backscattering signals transmitted during the transmission interval.

6. The method of claim 4, wherein the indication of the backscattering signals transmitted during the transmission interval comprises one or more transmitter properties of the backscattering device used for transmitting the backscattering signals during the transmission interval.

7. The method of claim 6, wherein the one or more transmitter properties are selected from the group comprising: one or more properties of an excitation signal of the backscattering transmission; one or more properties of a modulation scheme of the backscattering transmission; or one or more properties of a signal coding process of the backscattering transmission.

8. The method of claim 1 , further comprising:- buffering the signal received during the transmission interval until the information for reducing the interference signal is obtained.

9. The method of claim 1 , further comprising:- based on an a-priori radio channel estimate of a radio channel from a backscattering device of the backscattering transmission to the wireless communication device, determining an a-priori estimate of the interference signal,- based on the a-priori estimate of the interference signal, canceling the interference signal from the signal, to obtain a modified signal, and- performing a decoding attempt for decoding data from the modified signal.

10. The method of claim 9,- upon success of the decoding attempt for decoding the data from the modified signal: canceling the modified signal from the signal, to obtain an a-posteriori estimate of the interference signal, and- determining an a-posteriori estimate of the radio channel from the backscattering device to the wireless communication device based on the a-posteriori estimate of the interference signal.

11. The method of claim 9, wherein the a-priori estimate interference signal is further determined based on at least one of an indication or a guess of backscattering signals transmitted by the backscattering device during the transmission interval.

12. The method of claim 11 , further comprising:- upon failure of the decoding attempt based on the guess of the backscattering signals, requesting the indication of the backscattering signals transmitted during the transmission interval.

13. The method of claim 1 , wherein said obtaining of the information for reducing the interference signal comprises obtaining one or more control messages from the wireless communication network.

14. The method of claim 13, wherein at least one of the one or more control messages is obtained during or after the transmission interval.

15. The method of claim 1 , further comprising:- based on an a-priori radio channel estimate of a radio channel from a backscattering device of the backscattering transmission to the wireless communication device, determining an a-priori estimate of the interference signal,- based on the a-priori estimate of the interference signal, canceling the interference signal from the signal, to obtain a modified signal, and- performing a decoding attempt for decoding data from the modified signal.

16. The method of claim 15,- upon success of the decoding attempt for decoding the data from the modified signal: canceling the modified signal from the signal, to obtain an a-posteriori estimate of the interference signal, and- determining an a-posteriori estimate of the radio channel from the backscattering device to the wireless communication device based on the a-posteriori estimate of the interference signal.

17. A method for use in a wireless communication device associated with a wireless communication network, the method comprising:- during a transmission interval and using an active transmission, transmitting a signal to another wireless communication device associated with the wireless communication network, and- providing, to another wireless communication device, information for reducing an interference signal affecting the signal during the transmission interval, the interference signal stemming from a backscattering transmission.

18. The method of claim 17, wherein the wireless communication device implements a control node of the backscattering transmission and / or a receiving node of the backscattering transmission.

19. A wireless communication device for association with a wireless communication network, the wireless communication device comprising a processor and a memory, the processor being configured to load program code from the memory and to execute the program code, the processor, upon loading and executing the program code, being configured to:- during a transmission interval and using an active transmission, receive a signal from another wireless communication device associated with the wireless communication network, and- obtain information for reducing an interference signal affecting the signal during the transmission interval, the interference signal stemming from a backscattering transmission.

20. A wireless communication device for association with a wireless communication network, the wireless communication device comprising a processor and a memory, the processor being configured to load program code from the memory and to execute the program code, the processor, upon loading and executing the program code, being configured to:- during a transmission interval and using an active transmission, transmit a signal to another wireless communication device associated with the wireless communication network, and- provide, to another wireless communication device, information for reducing an interference signal affecting the signal during the transmission interval, the interference signal stemming from a backscattering transmission.

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