Backscatter signal strength by constructive addition of harmonics

Abstract

In an embodiment, a method and device for backscattering an incident signal is provided. The method includes filtering intermodulation products generated by non-linearities in a rectifier or an envelope detector when the device is subjected to the incident signal and generating a signal that matches a subcarrier spacing of the incident signal or that matches an integer multiple 5 of the subcarrier spacing of the incident signal. The method also includes switching impedance states of an antenna based on the generated signal to create a backscattered signal that is transmitted through the antenna, wherein the filtered intermodulation products are combined with the incident signal such that third order intermodulation products are added constructively to the incident signal in the backscattered signal. 0 Fig. 1A for publication

Description

BACKSCATTER SIGNAL STRENGTH BY CONSTRUCTIVE ADDITION OF HARMONICS RELATED APPLICATIONS

[0001] This application claims the benefit of provisional patent application serial number 63 / 552,825, filed February 13, 2024, the disclosure of which is hereby incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present disclosure relates to improving a backscatter signal strength of a backscatter transmission from a passive Internet of Things (IOT) device by the constructive addition or interference of harmonics caused by intermodulation products. BACKGROUND Zero Energy Internet of Things (IOT) and Ambient-IOT

[0003] Wireless IoT devices are often battery powered and both the need to change battery and the battery lifetime may be concerns for many potential applications such as asset tracking or environmental / industrial sensors. For this reason, the wireless communications industry has been interested in so-called zero-energy (ZE) devices. ZE devices refer to wireless IoT devices that do not require battery replacement, and often harvest energy from the environment. In some use cases, such as monitoring the temperature of foodstuffs, the ZE devices may have small batteries that are disposable (e.g., organic, compostable batteries), rechargeable or have very limited capacity.

[0004] These ZE-IoT devices can in addition be of very small form factor and could even be printable and they target ultra-low power consumption to enable operation based on either energy-harvesting from an ambient sources or back-scattering communication (cf. Radio Frequency Identification - RFID). That is, instead of relying on energy for communication being provided by a battery it is instead harvested from an ambient source, such as vibrations, solar power, Radio Frequency (RF), etc. (harvesting), or a charge carrier wave is provided to the device which is modulated and reflected back to a reader (in the back-scattering communication case). This enables energy autonomous operation during the lifetime of the devices without need for either manual replacement or charging of the batteries. Compared to existing radio access technologies this puts new requirements on the radio interface and the protocols.

[0005] Recently, work on this has been performed in Third Generation Partnership Program (3GPP), referred to as ‘Ambient-IoT’. Ambient IoT devices are characterized in the study according to their energy storage capacity, and capability of generating RF signals for their transmissions. Relying on these storage capacities, the study considers the following set of Ambient IoT devices. Types of Devices

[0006] Device A and B: Has energy storage, no independent signal generation, i.e. backscattering transmission. Use of stored energy can include amplification for reflected signals. Peak power consumption for device A is extremely small while device B can afford slightly higher peak power consumption.

[0007] Device C: Has energy storage, has independent signal generation, i.e., active RF components for transmission.

[0008] A limited energy storage can be different among implementations within Device B or implementations within Device C, and different between Device B and Device C. Such storage is expected to be order(s) of magnitude smaller than an NB-IoT device would typically include. RFID BackScatter and Access Protocols

[0009] Ambient IoT devices A and B inherit the principle of RFID backscatter, where an always on carrier wave generated by a RFID reader illuminates (powers) the transponder tag. The tag further transmits its stored information by modulating the same carrier wave signal that it receives from the reader. The modulation here is done by adjusting the antenna impedances and radar cross section of the tag, and the whole process of modulating the carrier wave and reflecting the modulated carrier back to the reader is called backscatter.

[0010] The actual data transmission between the reader and the tag can involve multiple back and forth communication; either initiated by the tag called tag-initiated transmissions or initiated by the reader called reader-initiated transmissions.

[0011] In tag-initiated transmissions, the reader keeps broadcasting a carrier signal, but the tag initiates data transmissions by encoding its data on the carrier wave and reflecting this back as a backscatter reflection. Aloha protocol, carrier sense protocols, etc. are typically used for this kind of transmission. The reader can further respond back to this communication. These are typically best effort transmissions with increased chances of collision.

[0012] In reader-initiated transmissions, the reader sends packets on the carrier wave to the tag, and the tag responds back by backscattering the carrier wave from the reader. There aremultiple protocols available in RFID literature to control the communication behavior between the tag and the reader in this case, and the most recent widely accepted standard on this is the EPC C1G2 protocol (ISO 18000-6C) standard.

[0013] EPC G1C2 follows a slotted aloha protocol. Here, the Interrogator(reader) communicates with one or more Tags by modulating an RF carrier using DSB-ASK, SSB-ASK, or PR-ASK with PIE encoding. The procedure takes place over three main phases: 1. Select / Challenge phase: This allows selecting a subset of tags that match a selection criterion- e.g.: Electronic Product Code. Tags that match this respond to the Select / Challenge command, while others remain silent. 2. Inventory phase: This allows the reader to obtain a tag’s handle which can be used for further ‘access’ type communication. The following are the steps for the communication in the inventory phase. a. Reader sends a Query command to the selected tags. Query command contains a Q-parameter (value ranging from 0 – 15) to specify frame size (equal to 2^Q-1) b. As response, each selected tag picks a random number between 0 and 2^Q-1 and put it into its slot counter. Tag also picks a random number RN16, which is a random number between 0 and 2^16. c. Each tag is allowed to respond to the reader when its slot counter becomes zero. If there is a collision, a Negative Acknowledgement (NACK) from the reader tells the tags to wait for another query until they respond again. d. A correctly acknowledged tag allows access when the reader uses the correct access password. When the reader polls the tag with the correct access password, the tag responds with a handle that allows the reader to perform access commands on the tag. 3. Access: Once the tag is identified, the reader may perform a core operation such as reading, writing, locking, or killing the Tag; a security-related operation such as authenticating the Tag; or a file-related operation such as opening a particular file in the Tag’s User memory Radio Access Network Plenary Discussion

[0014] The general scope for Ambient IoT as part of the RAN meeting #102 covers the following. A. The overall objective shall be to study a harmonized air interface design with minimized differences (where necessary) for Ambient IoT to enable the following devices:i. ~1 µW peak power consumption, has energy storage, initial sampling frequency offset (SFO) up to 10Xppm, neither DL nor UL amplification in the device. The device’s UL transmission is backscattered on a carrier wave provided externally. ii. ≤ a few hundred µW peak power consumption1, has energy storage, initial sampling frequency offset (SFO) up to 10Xppm, both DL and / or UL amplification in the device. The device’s UL transmission may be generated internally by the device, or be backscattered on a carrier wave provided externally. • X is to be decided in WGs. • Coverage design target: Maximum distance of 10-50 m with device indoors as per TR 38.848: “…a range that WGs can sub-select within”. • For Topologies 1 & 2 (UE as intermediate node under NW control) per TR 38.848, with no RRC states, no mobility (i.e. at least no cell selection / re-selection -like function), no Hybrid Automatic Repeat Request (HARQ), no Automatic Repeat Request (ARQ). NOTE 1: It is to be understood that “≤ a few hundred µW” means workgroups (WGs) are not tasked with setting a particular value, and that it will be for WG discussions to determine if a presented design with corresponding power consumption satisfies the “≤ a few hundred µW” requirement.’ B. Deployment Scenarios with the following characteristics, referenced to the tables in Clause 4.2.2 of TR 38.848: • Deployment scenario 1 with Topology 1 o Basestation and coexistence characteristics: Micro-cell, co-site • Deployment scenario 2 with Topology 2 and UE as intermediate node, under network control o Basestation and coexistence characteristics: Macro-cell, co-site o The location of intermediate node is indoor C. FR1 licensed spectrum in Frequency Division Duplex (FDD). D. Spectrum deployment in-band to NR, in guard-band to Long Term Evolution / New Radio (LTE / NR), in standalone band(s). E. Traffic types Device Originated Device Terminated Triggered (DO-DTT) Device Triggered (DT), with focus on rUC1 (indoor inventory) and rUC4 (indoor command). • From RAN#104, the study will assess whether the harmonized air interface design (per bullet ‘A’ above) can address the DO-A (Device-originated autonomous) usecase, only to identify which part(s) of the harmonized air interface design (per bullet ‘A’ above) is / are not sufficient for the DO-A use case. Transmission from Ambient IoT device (including backscattering when used) can occur at least in UL spectrum. From the above notes, the following assumptions are made: • A harmonized air interface needs to be assumed for all the devices considered in the study • A(i) refers to a passive type A(+) device, and A(ii) refers to passive type B device as well as type C device • A coverage range of 10-50m needs to be achieved for all the three types of devices • Device Originated- Downlink Triggered Transmission (DO-DTT) traffic. SUMMARY

[0015] Various embodiments provide for a passive Internet of Things (IOT) device, which can use constructive interference between a backscattered transmission and intermodulation products in order to improve the amplitude of the backscattered transmission, which boosts the signal power without any additional hardware complexity. This can be achieved by modifying a frequency of a baseband signal generator that controls the impedance switching of an antenna to match a sub-carrier spacing of the incident transmission. The intermodulation products created by non-linearities in the rectifying antenna can then be mixed with the signal from the baseband signal generator, and then constructively combined with the backscattered reflection of the incident transmission to create an enhanced backscattered transmission where intermodulation products constructively interfere with the fundamental frequencies of the original tone.

[0016] In an embodiment, a method performed by a device for backscattering an incident signal is provided, where the method includes filtering intermodulation products generated by non-linearities in a rectifier or an envelope detector when the device is subjected to the incident signal. The method also includes generating a signal that matches a subcarrier spacing of the incident signal or that matches an integer multiple of the subcarrier spacing of the incident signal and switching impedance states of an antenna based on the generated signal to create a backscattered signal that is transmitted through the antenna, wherein the filtered intermodulation products are combined with the incident signal such that third order intermodulation products are added constructively to the incident signal in the backscattered signal.

[0017] In an embodiment, the filtering comprises filtering the intermodulation products to suppress frequency components outside of a fundamental frequency band of the incident signal.

[0018] In an embodiment, the generated signal is a baseband signal.

[0019] In an embodiment, the incident signal is received from a first node, wherein the backscattered signal is transmitted to the first node or to a second node.

[0020] In an embodiment, the intermodulation products are generated by non-linearities in the rectifier or the envelope detector when said antenna is subjected to the incident signal; or the device comprises a second antenna, wherein the intermodulation products are generated by non- linearities in the rectifier or the envelope detector when the second antenna is subjected to the incident signal.

[0021] In an embodiment, the method further includes receiving signaling, wherein the generated signal is generated based on said signaling.

[0022] In an embodiment, the received signaling indicates the subcarrier spacing of the incident signal and / or a frequency of the generated signal.

[0023] In an embodiment, the signaling is received from a node from which the incident signal is received or the signaling is received from a node to which the backscattered signal is transmitted.

[0024] In an embodiment, the backscattered signal also comprises odd-numbered ordered intermodulation products higher than third order intermodulation products.

[0025] In an embodiment, a device is provided that is configured to perform any of the embodiments described above. In an embodiment, device may further include a bandpass filter that performs the filtering.

[0026] In an embodiment, device may further include a baseband processor that performs the generating.

[0027] In an embodiment, device may further include a radio frequency (RF) switch that performs the switching.

[0028] In an embodiment, a method is provided that is performed by a receiver node for receiving a backscattered signal. The method includes receiving the backscattered signal comprising intermodulation products or harmonics, filtering frequency components of the backscattered signal in respective bandpass filters, performing channel estimation on the filtered frequency components of the backscattered signal to generate coherent intermodulation products or harmonics, and combining the coherent intermodulation products or harmonics to increase a signal to noise ratio of the backscattered signal.

[0029] In an embodiment, the filtering comprises filtering the intermodulation products to suppress frequency components outside of a fundamental frequency band of the backscattered signal.

[0030] In an embodiment, a receiver node is provided for receiving a backscattered signal, wherein the receiver node is configured to perform the method of any of the embodiments described above. In an embodiment, the receiver node can include an antenna that performs the receiving. In an embodiment, the receiver node can include a plurality of bandpass filters that perform the filtering. In an embodiment, the receiver node can include a plurality of channel estimators that perform the channel estimation. In an embodiment, the receiver node can include a mixer that performs the combining. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0032] Figure 1A shows an example of a passive Internet of Things (IOT) device in accordance with some embodiments of the present disclosure;

[0033] Figure 1B shows an example of fundamental frequencies of an incident carrier wave and the third order intermodulation components in accordance with some embodiments of the present disclosure;

[0034] Figure 2 shows a flowchart of a method performed by a passive IOT device for improving backscattering by the constructive addition of harmonics in accordance with some embodiments of the present disclosure;

[0035] Figure 3 shows an example of a receiver device in accordance with some embodiments of the present disclosure;

[0036] Figure 4 shows a flowchart of a method performed by a receiver device for receiving a backscattered signal in accordance with some embodiments of the present disclosure;

[0037] Figure 5 shows an example of a communication system in accordance with some embodiments of the present disclosure;

[0038] Figure 6 shows a User Equipment device (UE) in accordance with some embodiments of the present disclosure; and

[0039] Figure 7 shows a network node in accordance with some embodiments of the present disclosure. DETAILED DESCRIPTION

[0040] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments.Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure.

[0041] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0042] There currently exist certain challenge(s). Passive ambient Internet of Things (IoT) devices (type A, A+ and B) rely on backscattering the carrier wave incident on the device for transmission. Backscattering involves adjusting the antenna impedance of the device so as to modulate and reflect an incident carrier wave.

[0043] Backscatter devices are equipped with a rectifying antenna which is typically optimized for maximum DC output power. The non-linearity of the diode element in the rectifier circuit leads to generation of harmonic frequencies. This results in losing some Radio Frequency to Direct Current (RF-to-DC) conversion efficiency.

[0044] The current Ambient IoT study item focuses on Frequency Division Duplex (FDD) systems on topology 1 and 2 for both monostatic and bistatic setups. A monostatic setup means that the same node (for example a gNB) transmits the carrier wave and receives the backscattered version of the carrier wave from the IoT device. A bistatic setup means that a node (typically not a gNB) generates the carrier wave and another node (for example a gNB) receives the backscattered version of the carrier wave from the IoT device.

[0045] There can be a strong interference between the transmit path and the receive path, particularly in the monostatic setups. However, it is important to note that these harmonics can be of even lower power than the primary component at the center frequency.

[0046] With a power constraint in the order of less than 1uW especially for type A / A+ device, the devices cannot support a power amplifier as well. This means achieving a transmission range of 10-50m with self-interference cancellation possible at the reader can be quite challenging.

[0047] Certain aspects of the disclosure and their embodiments may provide solutions to these or other challenges. The proposed techniques disclosed herein involve constructive addition of intermodulation products due to harmonics at the reader. The constructive addition is at the IOT device when the third order intermodulation products (IM3) components of the rectifier or the envelope detector are added instead of filtering them out (short circuiting it) as in conventional rectifier design which aim at maximizing the output DC power. This allowsboosting the signal power of the backscattered transmission without any additional hardware complexity. This improves the range and decoding capability of backscattered reflections and reduces near far effects in a multi-device scenario.

[0048] Due to hardware non-linearity, a backscatter reflection in practice comprises of repeated reflections which are equally spaced apart at ‘nf’, f being the fundamental frequency of the incident carrier wave of the reflected signal and n being the harmonics number. The total power of the reflected signal is distributed among each of these harmonics, with reflected power reducing continuously across each increasing harmonics; for example, the power of backscatter reflection at nth harmonics is higher than that at (n+1) th harmonics.

[0049] In the present disclosure are described techniques to filter the harmonics due to the non-linearity of the rectifier / or the enveloped detector present in the device at the fundamental frequency of the incident carrier wave, combine with the input signal from the antenna to the backscatter modulator and mix it with a switching frequency that results in shifting the intermodulation frequencies with a configured frequency offset. This enables a constructive addition within the harmonics, such that the overall power of the backscattered reflection can be considerably boosted.

[0050] Certain embodiments may provide one or more of the following technical advantage(s). With the techniques disclosed herein, the backscattered harmonics from the Ambient IoT devices can be decoded more efficiently. In addition, this improves the range of backscattered receptions, and reduces near far effects, where the near far effect is the effect of a strong signal from a near signal source making it hard for a receiver to hear a weaker signal from a further source due to adjacent-channel interference, co-channel interference, distortion, capture effect, dynamic range limitation, or the like.

[0051] Assuming an ideal hardware, a single-tone carrier wave transmitted at frequency ^^when incident on an A-IoT device generating a rectangular pulse at a baseband frequency ∆^^results in the backscatter signal being received as two mirrored reflections at frequencies ^^−∆^^ and ^^ + ∆^^. Note that achieving this rectangular pulse requires the backscatter device toswitch its impedance rate at ∆^^.

[0052] However, due to imperfections / non-linearity in A-IoT device hardware, a receiver,instead of obtaining backscatter reflections at just ^^ − ∆^^ and ^^ + ∆^^ will also receiveharmonics at frequencies that are integer multiples of the carrier frequencies as well asbackscatter frequencies. Therefore, a receiver receives backscatter reflections at n*^^ ± ^ ∗ ∆^^ ,n and m being integers unless the A-IoT hardware filters out some of these harmonic components.

[0053] While harmonics is periodic in nature, for multi-tone carrier wave (a more generalized case), there can also be intermodulation products which are aperiodic. For example, for a 2-tone carrier wave (CW) with tones f1 and f2, the intermodulation products of second order comes at f1+f2, f1-f2, the third order intermodulation products IM3 come at 2f1-f2, 2f2-f1,2f1+f2, 2f2+f1, etc. This means backscattered reflections would be seen at ±^ ∗ ∆^^ for each ofthese components. The intermodulation products could also be other odd numbered intermodulation products higher than third order, such as fifth order, seventh order, etc.

[0054] The embodiments described herein depict techniques that enable constructive addition within backscatter harmonics, which enables the signals to add up coherently. Note that in all these cases, the noise part, which is random and independent, adds up incoherently resulting in an overall increase in the combined signal to noise ratio (SNR), allowing the reader / gNB to decode the backscatter reflection more efficiently, which may not otherwise be decodable. With higher signal power achieved through this technique, the transmission range of backscattered reflections increase as well. Note that ‘devices’ here refers to backscattering enabled Passive ambient IoT devices.

[0055] Figure 1A shows an example of a passive Internet of Things (IOT) device 100 in accordance with some embodiments of the present disclosure.

[0056] In the main embodiment, the rate of switching the impedance states (e.g., reflection or absorption) connected to an antenna 104 of the passive IOT device 100 is selected to match the subcarrier spacing of the impinging signal 114 or match an integer multiple of the subcarrier spacing. In addition, the harmonics due to the non-linear components present in the device 100 are filtered and mixed with the same baseband frequency of the switch 106 (fed to the same antenna 104 used for backscattering). It is to be appreciated that whilst Figure 1A depicts a device 100 with a single antenna, in other embodiments, the device 100 could include two or more antennas.

[0057] Filtering refers to a bandpass filter 116 at an output of the rectifier 118, then RF combining with the path of the incoming carrier wave from the antenna. The result of this combination is connected to an impedance switch 106 that is controlled by a baseband signal generator / processing 108. The result of this switching would be equivalent to mixing with the baseband frequency delta_f. If this delta_f is selected to be an integer multiple of the subcarrier spacing this would result in enhancing the strength of a number of tones in the backscattered signal which might increase the read range for selected tags.

[0058] This results in constructive addition of the intermodulation products due to harmonics at the fundamental frequency and the backscattered signal as explained below.

[0059] Assume a multi-tone signal illuminating the backscatter device given by: ^^^^ = ∑^ ^^^ ^^ cos^2^^^^ + ^^^ Eqn. 1

[0060] and / or an envelopedetector 120 which include a diode element (non-linear component) and generates harmonics. In general, one can express the output signal due to this non-linearity, when the IOT device is not switching impedance as a memoryless polynomial function as follows [Eqn.1]. ^^^^ = ^^ + ^^^^^^ + ^ ^ ^^^ ^^^ + ^^^ ^^^ + ⋯ Eqn. 2

[0061] The above equation is terminated to the third harmonic since the higher order harmonics typically have insignificant power and can be neglected.

[0062] Assume a uniform narrow spacing between the tones, i.e., ^^ = ^^ + !∆^ , with ∆^ ≪^^being the subcarrier spacing. The third order modulation (IM3) products (i.e., ^^^^^ in Eq.2) would generate tones in the fundamental frequency. In general, the third order modulation products can be expressed as: ^#$^ = ±^^%±&^' ± (^) Eqn. 3with ^, & and ( being integers such that ^ + & + ( = 3 , and +, ^, ^ ∈ / 1, 12. Where N is thetotal number of tones. X, y, z can take any value from 1 to N since IM3 can be any tone f1+f2+f3 for example or 2*f1-f2 or 2*f3-f1 or 2*f3-f2 or 2*f2+f1.

[0063] As an example, consider two tones where ^^ = ^^, and ^^ = ^^ + ∆^ , where the IM3products which lie at the fundamental frequencycan be expressed as: ^^,^ = 2^^ − ^^ = ^^ − ∆^ Eqn. 4^^,^ = 2^^ − ^^ = ^^ + 2∆^ Eqn. 5

[0064] These frequencies are depicted in Figure 1B. Backscattering is typically realized by modulating the incident signal 114 at the fundamental frequency by switching the impedance state of the antenna as illustrated in Figure 1A. The incident carrier signal has a frequency equal to the fundamental frequency.

[0065] If the switch 106 is modulated with a baseband signal (e.g., square wave or a sine wave of frequency ∆^^) generated by baseband signal generator 108, the resulting effect is the mixing of the frequency of the impinging RF signal with the baseband frequency ∆^^. This yields the reflection of two images of the impinging waves, having frequency offsets ±∆^^added to the frequency of the impinging waves.

[0066] The main idea of this present disclosure here is to filter the harmonics due to the rectifier 118 or the envelope detector 120 at the fundamental frequency and mix it with a switching frequency that results in shifting the IM3 frequencies with a frequency offset of ±∆^^.In the case where ∆^^ = ∆^ (i.e., the switching frequency rate is equal to the subcarrier spacing),the harmonics add constructively with the fundamental frequencies of the original tones leading to an increase in the amplitude of the enhanced backscattered transmission 112 that is transmitted back to a first node 102. The IOT device 100 can also receive an incident signal 114 from a first node 102 and reflect the backscattered transmission 112 to a second node 103.

[0067] The table below summarizes the result of mixing the impinging wave and the IM3 products with a baseband frequency ∆^. Frequency components at the fundamental Frequency components at the frequency before switching (mixing with fundamental frequency after ∆^) switching ^^ = ^^ ^^ − ∆^ , ^^ + ∆^^^ = ^^ + ∆^ ^^ , ^^ + 2∆^^^,^ = ^^ − ∆^ ^^ − 2∆^ , ^^^^,^ = ^^ + 2∆^ ^^ + ∆^, ^^ + 3∆^Table 1. Constructive addition of frequency components by mixing with ∆^

[0068] The frequency components underlined are added constructively resulting in an increase in the strength of the backscattered signal. The same analysis can be extended to more than two tones.

[0069] In another embodiment, in order to add harmonics constructively, where ^^ = ^^ +!∆^ , with ∆^ ≪ ^^, phase 4_! should be set aligned. The harmonic frequencies are:^^, ^^ + 6^, ^^ + 26^, … Eqn. 6and ^^and ∆^ should be set such that: 89:;8 89:^;8 89,89 , … Eqn. 7which is are both integers, and thedenominator is not zero. Additionally, the numerator and denominator should have no common factors other than one.

[0070] In an embodiment, the above approach can be used selectively to amplify certain backscatter devices while leaving the other backscattered reflections from the devices unchanged without modifying the circuit hardware in anyway. For instance, consider a case where device1 is far to the first node 102, while device 2 is closer. Therefore, device 1’s data is harder to decode, and using the approach in Table 1 the intermodulation components in device1 canachieve boosted power at ^^ + ∆^ and ^^. By configuring the switching rate of device 2 to, forexample, 2∆^ it can be ensured that device 2’s amplitude remains the same and stays almostorthogonal to device 1. In this case, the result of mixing the impinging wave and the IM3 products with a baseband frequency 2∆^ is given as follows: Frequency components at the Frequency components at the fundamental frequency before fundamental frequency after switching (mixing with 2∆^) switching ^^ = ^^ ^^ − 2∆^ , ^^ + 2∆^^^ = ^^ + ∆^ ^^ − ∆^ , ^^ + 3∆^^^,^ = ^^ − ∆^ ^^ − 3∆^ , ^^+∆^^^,^ = ^^ + 2∆^ ^^, ^^ + 4∆^Table 2

[0071] Note that in Table 2, the frequency components for device 2 at ^^ + ∆^ and ^^ stayswith the same amplitude, while device 1’s amplitude was boosted in these frequency components. By adjusting configuring for multiple devices based on the above principle, near far effects can be minimized. By ensuring that the modulation rate of device 2 is 2∆^, device 2’s intermodulation components can be adjusted to interfere minimally with device 1.

[0072] To control the passive IOT devices, the first node 102 may send an indication to the passive IOT device 100 to modulate the frequencies of the baseband signal. Processing circuitry 110 at the passive IOT device 100 can control the baseband signal generator 108 to modulate the frequency based on the indication from the IOT reader. In other embodiments, the processing circuitry 110 can be configured to determine the subcarrier spacing of the incident transmission 114, based on an earlier transmission, and thus modulate the frequency of the baseband signal generator 108 based on the determination.

[0073] Figure 2 shows a flowchart of a method 200 performed by a passive IOT device for improving backscattering by the constructive addition of harmonics in accordance with some embodiments of the present disclosure;

[0074] The flow chart can begin at step 202 where the method optionally includes receiving signaling. The signaling can arrive from a first node 102 or a second node 103, and include instructions or indications as to what the sub-carrier spacing of the incident transmission will be. In other embodiments, the signaling may include instructions to activate the device or generate the signal by the baseband signal generator that matches the subcarrier spacing of the incident signal. The signaling could also include the subcarrier spacing of the incident signal or a frequency of the generated signal.

[0075] In an embodiment, the incident signal is received from a first node, wherein the backscattered signal is transmitted to the first node or to a second node.

[0076] At step 204, the method includes filtering intermodulation products generated by non-linearities in a rectifier or an envelope detector when the device is subjected to the incident signal. In an embodiment, the filtering comprises filtering the intermodulation products to suppress frequency components outside of a fundamental frequency band of the incident signal.

[0077] In an embodiment, the intermodulation products are generated by non-linearities in the rectifier or the envelope detector when said antenna is subjected to the incident signal. In an embodiment, the device comprises a second antenna, wherein the intermodulation products are generated by non-linearities in the rectifier or the envelope detector when the second antenna is subjected to the incident signal.

[0078] At step 206, the method includes generating a signal that matches a subcarrier spacing of the incident signal or that matches an integer multiple of the subcarrier spacing of the incident signal. In an embodiment, the generated signal is a baseband signal.

[0079] At step 208, the method includes switching impedance states of an antenna based on the generated signal to create a backscattered signal that is transmitted through the antenna, wherein the filtered intermodulation products are combined with the incident signal such that third order intermodulation products are added constructively to the incident signal in the backscattered signal.

[0080] In another embodiment, constructive addition can be performed at a receiver (e.g. 102 or 103) as shown in Fig.3 that receives the backscattered transmission 112 (e.g., by second node 103). The second node 102 or 103 can receive the harmonic components in the backscattered signal 112 from the device 100 at RF front end 302 which includes at least one antenna 304. Filtering is performed at Bandpass Filters (BPF) 306-1, 306-2, etc. to filter thefrequency components ^^ + !∆^. Channel estimation is done by Channel Estimators 308-1,308-2 on each of these harmonic components thereby making them coherent. This allows constructive addition of frequency components at mixer 310, boosting their signal power significantly.

[0081] For example, consider the frequency components filtered around the CW frequency^^ which contains harmonics at ^^ ± ! ∗ ∆^, i being an integer value and ∆^ being the basebandfrequency of the A-IoT device.

[0082] In order to add harmonic components ^^ = ^^ + !∆^ at the A-IoT receiverconstructively, with ∆^ ≪ ^^, the phase of their channel 4_! needs to be set aligned. For this, atharmonic frequencies:^^ + 6^, ^^ + 26^, … Eqn. 8

[0083] ^^and ∆^ are set such that 89:;8 89:^;8 89,89 , … Eqn. 9are simple integers, and thedenominator is not zero. Additionally, the numerator and denominator should have no common factors other than one. The main reason for the simple fraction condition above is to avoid destructive addition when there is phase alignment.

[0084] Figure 4 shows a flowchart of a method 400 performed by a receiver device (e.g., device 102 or 103) for receiving a backscattered signal 112 in accordance with some embodiments of the present disclosure.

[0085] It should be appreciated that the backscattering device 100 of Figure 1A and the method of Figure 2 can be used independently of the receiver device (e.g., receiver node 102 or 103). The backscattering device 100 can transmit to any type of receiver device, while the receiver device of Figure 3 (and the following methods steps in Figure 4) can operate based on transmissions received from any transmitter, including backscattering device 100. The most efficient usage, where energy usage is minimized and range is maximized, can be when backscattering device 100 and the receiver of Figures 3 and 4 are used in tandem.

[0086] The flow chart can begin at step 402 where the method includes receiving, the backscattered signal (112) comprising intermodulation products or harmonics.

[0087] At 404 the method includes filtering frequency components of the backscattered signal (112) in respective bandpass filters. In an embodiment, the filtering includes filtering the intermodulation products to suppress frequency components outside of a fundamental frequencyband of the incident signal. In an embodiment, each frequency component ^^ + !∆^ is filteredby passing through separate BPF (306-1, 306-2).

[0088] At step 406, the method includes performing channel estimation on the filtered frequency components of the backscattered signal to generate coherent intermodulation products or harmonics, where the channel 4_! is extracted from each of the frequency components.

[0089] At step 408, the method includes constructively combining the coherent intermodulation products or harmonics to increase a signal to noise ratio or a signal strength of the backscattered signal, thereby compensating for 4_! in each of the frequency components.

[0090] Figure 5 shows an example of a communication system 500 in accordance with some embodiments.

[0091] In the example, the communication system 500 includes a telecommunication network 502 that includes an access network 504, such as a Radio Access Network (RAN), and acore network 506, which includes one or more core network nodes 508. The access network 504 includes one or more access network nodes, such as network nodes 510A and 510B (one or more of which may be generally referred to as network nodes 510), or any other similar Third Generation Partnership Project (3GPP) access nodes or non-3GPP Access Points (APs). Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, the telecommunication network 502 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in the telecommunication network 502 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in the telecommunication network 502, including one or more network nodes 510 and / or core network nodes 508.

[0092] Examples of an ORAN network node include an Open Radio Unit (O-RU), an Open Distributed Unit (O-DU), an Open Central Unit (O-CU), including an O-CU Control Plane (O- CU-CP) or an O-CU User Plane (O-CU-UP), a RAN intelligent controller (near-real time or non- real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp), or any combination thereof (the adjective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an A1, F1, W1, E1, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an O-2 interface defined by the O-RAN Alliance or comparable technologies. The network nodes 510 facilitate direct or indirect connection of User Equipment (UE), such as by connecting UEs 512A, 512B, 512C, and 512D (one or more of which may be generally referred to as UEs 512) to the core network 506 over one or more wireless connections.

[0093] Example wireless communications over a wireless connection include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information without the use of wires, cables,or other material conductors. Moreover, in different embodiments, the communication system 500 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that may facilitate or participate in the communication of data and / or signals whether via wired or wireless connections. The communication system 500 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0094] The UEs 512 may be any of a wide variety of communication devices, including the passive IOT device 100 described herein arranged, configured, and / or operable to communicate wirelessly with the network nodes 510 and other communication devices. Similarly, the network nodes 510 are arranged, capable, configured, and / or operable to communicate directly or indirectly with the UEs 512 and / or with other network nodes or equipment in the telecommunication network 502 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in the telecommunication network 502. In an embodiment, the network nodes 510 or the hub 514 could be examples of the IOT reader 102 described herein.

[0095] In the depicted example, the core network 506 connects the network nodes 510 to one or more hosts, such as host 516. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 506 includes one more core network nodes (e.g., core network node 508) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and / or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 508. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-Concealing Function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and / or a User Plane Function (UPF).

[0096] The host 516 may be under the ownership or control of a service provider other than an operator or provider of the access network 504 and / or the telecommunication network 502, and may be operated by the service provider or on behalf of the service provider. The host 516 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio / video content, data collection services such as retrieving andcompiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

[0097] As a whole, the communication system 500 of Figure 5 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system 500 may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and / or other suitable Second, Third, Fourth, or Fifth Generation (2G, 3G, 4G, or 5G) standards, or any applicable future generation standard (e.g., Sixth Generation (6G)); Wireless Local Area Network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any Low Power Wide Area Network (LPWAN) standards such as LoRa and Sigfox.

[0098] In some examples, the telecommunication network 502 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunication network 502 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 502. For example, the telecommunication network 502 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing enhanced Mobile Broadband (eMBB) services to other UEs, and / or massive Machine Type Communication (mMTC) / massive Internet of Things (IoT) services to yet further UEs.

[0099] In some examples, the UEs 512 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 504 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 504. Additionally, a UE may be configured for operating in single- or multi-Radio Access Technology (RAT) or multi-standard mode. For example, a UE may operate with any one or combination of WiFi, New Radio (NR), and LTE, i.e. being configured for Multi-Radio Dual Connectivity (MR-DC), such as Evolved UMTS Terrestrial RAN (E-UTRAN) NR - Dual Connectivity (EN-DC).

[0100] In the example, a hub 514 communicates with the access network 504 to facilitate indirect communication between one or more UEs (e.g., UE 512C and / or 512D) and networknodes (e.g., network node 510B). In some examples, the hub 514 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub 514 may be a broadband router enabling access to the core network 506 for the UEs. As another example, the hub 514 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 510, or by executable code, script, process, or other instructions in the hub 514. As another example, the hub 514 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 514 may be a content source. For example, for a UE that is a Virtual Reality (VR) headset, display, loudspeaker or other media delivery device, the hub 514 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 514 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, the hub 514 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy IoT devices.

[0101] The hub 514 may have a constant / persistent or intermittent connection to the network node 510B. The hub 514 may also allow for a different communication scheme and / or schedule between the hub 514 and UEs (e.g., UE 512C and / or 512D), and between the hub 514 and the core network 506. In other examples, the hub 514 is connected to the core network 506 and / or one or more UEs via a wired connection. Moreover, the hub 514 may be configured to connect to a Machine-to-Machine (M2M) service provider over the access network 504 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 510 while still connected via the hub 514 via a wired or wireless connection. In some embodiments, the hub 514 may be a dedicated hub – that is, a hub whose primary function is to route communications to / from the UEs from / to the network node 510B. In other embodiments, the hub 514 may be a non-dedicated hub – that is, a device which is capable of operating to route communications between the UEs and the network node 510B, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0102] Figure 6 shows a UE 600 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged, and / or operable to communicate wirelessly with network nodes and / or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, Voice over Internet Protocol (VoIP) phone, wireless local loop phone, desktop computer, Personal Digital Assistant (PDA), wireless camera, gaming console ordevice, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, Laptop Embedded Equipment (LEE), Laptop Mounted Equipment (LME), smart device, wireless Customer Premise Equipment (CPE), vehicle, vehicle-mounted or vehicle embedded / integrated wireless device, etc. Other examples include any UE identified by the 3GPP, including a Narrowband Internet of Things (NB-IoT) UE, a Machine Type Communication (MTC) UE, and / or an enhanced MTC (eMTC) UE.

[0103] A UE may support Device-to-Device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), Vehicle-to-Vehicle (V2V), Vehicle-to-Infrastructure (V2I), or Vehicle- to-Everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and / or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).

[0104] The UE 600 includes processing circuitry 602 that is operatively coupled via a bus 604 to an input / output interface 606, a power source 608, memory 610, a communication interface 612, and / or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 6. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

[0105] The processing circuitry 602 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 610. The processing circuitry 602 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, Field Programmable Gate Arrays (FPGAs), Application Specific Integrated Circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general purpose processors, such as a microprocessor or Digital Signal Processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry 602 may include multiple Central Processing Units (CPUs).

[0106] In the example, the input / output interface 606 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and / or outputdevices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE 600. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.

[0107] In some embodiments, the power source 608 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source 608 may further include power circuitry for delivering power from the power source 608 itself, and / or an external power source, to the various parts of the UE 600 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 608. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 608 to make the power suitable for the respective components of the UE 600 to which power is supplied.

[0108] The memory 610 may be or be configured to include memory such as Random Access Memory (RAM), Read Only Memory (ROM), Programmable ROM (PROM), Erasable PROM (EPROM), Electrically EPROM (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 610 includes one or more application programs 614, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 616. The memory 610 may store, for use by the UE 600, any of a variety of various operating systems or combinations of operating systems.

[0109] The memory 610 may be configured to include a number of physical drive units, such as Redundant Array of Independent Disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, High Density Digital Versatile Disc (HD- DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, Holographic Digital Data Storage (HDDS) optical disc drive, external mini Dual In-line Memory Module(DIMM), Synchronous Dynamic RAM (SDRAM), external micro-DIMM SDRAM, smartcard memory such as a tamper resistant module in the form of a Universal Integrated Circuit Card (UICC) including one or more Subscriber Identity Modules (SIMs), such as a Universal SIM (USIM) and / or Internet Protocol Multimedia Services Identity Module (ISIM), other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as a ‘SIM card.’ The memory 610 may allow the UE 600 to access instructions, application programs, and the like stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system, may be tangibly embodied as or in the memory 610, which may be or comprise a device-readable storage medium.

[0110] The processing circuitry 602 may be configured to communicate with an access network or other network using the communication interface 612. The communication interface 612 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 622. The communication interface 612 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter 618 and / or a receiver 620 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 618 and receiver 620 may be coupled to one or more antennas (e.g., the antenna 622) and may share circuit components, software, or firmware, or alternatively be implemented separately.

[0111] In the illustrated embodiment, communication functions of the communication interface 612 may include cellular communication, WiFi communication, LPWAN communication, data communication, voice communication, multimedia communication, short- range communications such as Bluetooth, NFC, location-based communication such as the use of the Global Positioning System (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented according to one or more communication protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband CDMA (WCDMA), GSM, LTE, NR, UMTS, WiMax, Ethernet, Transmission Control Protocol / Internet Protocol (TCP / IP), Synchronous Optical Networking (SONET), Asynchronous Transfer Mode (ATM), Quick User Datagram Protocol Internet Connection (QUIC), Hypertext Transfer Protocol (HTTP), and so forth.

[0112] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 612, via a wireless connection to a network node.Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[0113] As another example, a UE comprises an actuator, a motor, or a switch related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input.

[0114] A UE, when in the form of an IoT device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application, and healthcare. Non-limiting examples of such an IoT device are a device which is or which is embedded in: a connected refrigerator or freezer, a television, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door / window sensor, a flood / moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or VR, a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an IoT device comprises circuitry and / or software in dependence of the intended application of the IoT device in addition to other components as described in relation to the UE 600 shown in Figure 6.

[0115] As yet another specific example, in an IoT scenario, a UE may represent a machine or other device that performs monitoring and / or measurements and transmits the results of such monitoring and / or measurements to another UE and / or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship, an airplane, or other equipment thatis capable of monitoring and / or reporting on its operational status or other functions associated with its operation.

[0116] In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g., by controlling an actuator) to increase or decrease the drone’s speed. The first and / or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator and handle communication of data for both the speed sensor and the actuators.

[0117] Figure 7 shows a network node 700 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged, and / or operable to communicate directly or indirectly with a UE and / or with other network nodes or equipment in a telecommunication network. Examples of network nodes include, but are not limited to, APs (e.g., radio APs), Base Stations (BSs) (e.g., radio BSs, Node Bs, evolved Node Bs (eNBs), NR Node Bs (gNBs)), and O-RAN nodes or components of an O-RAN node (e.g., O-RU, O-DU, O- CU).

[0118] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node), and / or Remote Radio Units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such RRUs may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a Distributed Antenna System (DAS).

[0119] Other examples of network nodes include multiple Transmission Point (multi-TRP) 7G access nodes, Multi-Standard Radio (MSR) equipment such as MSR BSs, network controllers such as Radio Network Controllers (RNCs) or BS Controllers (BSCs), Base Transceiver Stations (BTSs), transmission points, transmission nodes, Multi-Cell / Multicast Coordination Entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and / or Minimization of Drive Tests (MDTs).

[0120] The network node 700 includes processing circuitry 702, memory 704, a communication interface 706, and a power source 708. The network node 700 may be composed of multiple physically separate components (e.g., a NodeB component and an RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node 700 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair may in some instances be considered a single separate network node. In some embodiments, the network node 700 may be configured to support multiple RATs. In such embodiments, some components may be duplicated (e.g., separate memory 704 for different RATs) and some components may be reused (e.g., a same antenna 710 may be shared by different RATs). The network node 700 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 700, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, Long Range Wide Area Network (LoRaWAN), Radio Frequency Identification (RFID), or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within the network node 700.

[0121] The processing circuitry 702 may comprise a combination of one or more of a microprocessor, controller, microcontroller, CPU, DSP, ASIC, FPGA, or any other suitable computing device, resource, or combination of hardware, software, and / or encoded logic operable to provide, either alone or in conjunction with other network node 700 components, such as the memory 704, to provide network node 700 functionality.

[0122] In some embodiments, the processing circuitry 702 includes a System on a Chip (SOC). In some embodiments, the processing circuitry 702 includes one or more of Radio Frequency (RF) transceiver circuitry 712 and baseband processing circuitry 714. In some embodiments, the RF transceiver circuitry 712 and the baseband processing circuitry 714 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of the RF transceiver circuitry 712 and the baseband processing circuitry 714 may be on the same chip or set of chips, boards, or units.

[0123] The memory 704 may comprise any form of volatile or non-volatile computer- readable memory including, without limitation, persistent storage, solid state memory, remotely mounted memory, magnetic media, optical media, RAM, ROM, mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD), or a Digital Video Disk (DVD)), and / or any other volatile or non-volatile, non-transitorydevice-readable, and / or computer-executable memory devices that store information, data, and / or instructions that may be used by the processing circuitry 702. The memory 704 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and / or other instructions capable of being executed by the processing circuitry 702 and utilized by the network node 700. The memory 704 may be used to store any calculations made by the processing circuitry 702 and / or any data received via the communication interface 706. In some embodiments, the processing circuitry 702 and the memory 704 are integrated.

[0124] The communication interface 706 is used in wired or wireless communication of signaling and / or data between a network node, access network, and / or UE. As illustrated, the communication interface 706 comprises port(s) / terminal(s) 716 to send and receive data, for example to and from a network over a wired connection. The communication interface 706 also includes radio front-end circuitry 718 that may be coupled to, or in certain embodiments a part of, the antenna 710. The radio front-end circuitry 718 comprises filters 720 and amplifiers 722. The radio front-end circuitry 718 may be connected to the antenna 710 and the processing circuitry 702. The radio front-end circuitry 718 may be configured to condition signals communicated between the antenna 710 and the processing circuitry 702. The radio front-end circuitry 718 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry 718 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of the filters 720 and / or the amplifiers 722. The radio signal may then be transmitted via the antenna 710. Similarly, when receiving data, the antenna 710 may collect radio signals which are then converted into digital data by the radio front-end circuitry 718. The digital data may be passed to the processing circuitry 702. In other embodiments, the communication interface 706 may comprise different components and / or different combinations of components.

[0125] In certain alternative embodiments, the network node 700 does not include separate radio front-end circuitry 718; instead, the processing circuitry 702 includes radio front-end circuitry and is connected to the antenna 710. Similarly, in some embodiments, all or some of the RF transceiver circuitry 712 is part of the communication interface 706. In still other embodiments, the communication interface 706 includes the one or more ports or terminals 716, the radio front-end circuitry 718, and the RF transceiver circuitry 712 as part of a radio unit (not shown), and the communication interface 706 communicates with the baseband processing circuitry 714, which is part of a digital unit (not shown).

[0126] The antenna 710 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. The antenna 710 may be coupled to the radio front-end circuitry 718 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, the antenna 710 is separate from the network node 700 and connectable to the network node 700 through an interface or port.

[0127] The antenna 710, the communication interface 706, and / or the processing circuitry 702 may be configured to perform any receiving operations and / or certain obtaining operations described herein as being performed by the network node 700. Any information, data, and / or signals may be received from a UE, another network node, and / or any other network equipment. Similarly, the antenna 710, the communication interface 706, and / or the processing circuitry 702 may be configured to perform any transmitting operations described herein as being performed by the network node 700. Any information, data, and / or signals may be transmitted to a UE, another network node, and / or any other network equipment.

[0128] The power source 708 provides power to the various components of the network node 700 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 708 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 700 with power for performing the functionality described herein. For example, the network node 700 may be connectable to an external power source (e.g., the power grid or an electricity outlet) via input circuitry or an interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 708. As a further example, the power source 708 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

[0129] Embodiments of the network node 700 may include additional components beyond those shown in Figure 7 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and / or any functionality necessary to support the subject matter described herein. For example, the network node 700 may include user interface equipment to allow input of information into the network node 700 and to allow output of information from the network node 700. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 700.

[0130] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understoodthat these computing devices may comprise any suitable combination of hardware and / or software needed to perform the tasks, features, functions, and methods disclosed herein. Determining, calculating, obtaining, or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and / or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box or nested within multiple boxes, in practice computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and / or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

[0131] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer- readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hardwired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer- readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole and / or by end users and a wireless network generally.

[0132] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

[0133] Some of the embodiments of the present disclosure include:

[0134] Embodiment 1: A method performed by a device (100) for backscattering an incident signal, the method comprising: filtering (204) intermodulation products generated by non- linearities in a rectifier (118) or an envelope detector (120) when the device (100) is subjected tothe incident signal (114); generating (206) a signal that matches a subcarrier spacing of the incident signal (114) or that matches an integer multiple of the subcarrier spacing of the incident signal (114); and switching (208) impedance states of an antenna (104) based on the generated signal to create a backscattered signal (112) that is transmitted through the antenna (104), wherein the filtered intermodulation products are combined with the incident signal (114) such that third order intermodulation products are added constructively to the incident signal (114) in the backscattered signal (112).

[0135] Embodiment 2: The method of embodiment 1, wherein the filtering comprises filtering the intermodulation products to suppress frequency components outside of a fundamental frequency band of the incident signal (114).

[0136] Embodiment 3: The method of any of embodiments 1 to 2, wherein the generated signal is a baseband signal.

[0137] Embodiment 4: The method of any of embodiments 1 to 3, wherein the incident signal (114) is received from a first node (102), wherein the backscattered signal (112) is transmitted to the first node (102) or to a second node (103).

[0138] Embodiment 5: The method of any of embodiments 1 to 4, wherein: the intermodulation products are generated by non-linearities in the rectifier (118) or the envelope detector (120) when said antenna (104) is subjected to the incident signal (114); or the device (100) comprises a second antenna (104), wherein the intermodulation products are generated by non-linearities in the rectifier (118) or the envelope detector (120) when the second antenna (104) is subjected to the incident signal (114).

[0139] Embodiment 6: The method of any of embodiments 1 to 5, further comprising: receiving (202) signaling, wherein the generated signal is generated based on said signaling.

[0140] Embodiment 7: The method of embodiment 6, wherein the received signaling indicates: the subcarrier spacing of the incident signal (114); and / or a frequency of the generated signal.

[0141] Embodiment 8: The method of any of embodiments 6 to 7, wherein said signaling is received from a node (102) from which the incident signal (114) is received; or said signaling is received from a node (103) to which the backscattered signal (112) is transmitted.

[0142] Embodiment 9: A device (100) for backscattering an incident signal, wherein the device is configured to perform the methods of embodiments 1 to 8. REFERENCES1.TR 38.848, V18.0.0, “Study on Ambient IoT (Internet of Things) in RAN (Release 18)”

Claims

CLAIMS 1. A method (200) performed by a device (100) for backscattering an incident signal, the method comprising: filtering (204) intermodulation products generated by non-linearities in a rectifier (118) or an envelope detector (120) when the device (100) is subjected to the incident signal (114); generating (206) a signal that matches a subcarrier spacing of the incident signal (114) or that matches an integer multiple of the subcarrier spacing of the incident signal (114); and switching (208) impedance states of an antenna (104) based on the generated signal to create a backscattered signal (112) that is transmitted through the antenna (104), wherein the filtered intermodulation products are combined with the incident signal (114) such that third order intermodulation products are added constructively to the incident signal (114) in the backscattered signal (112).

2. The method of claim 1, wherein the filtering comprises filtering the intermodulation products to suppress frequency components outside of a fundamental frequency band of the incident signal (114).

3. The method of any of claims 1 to 2, wherein the generated signal is a baseband signal.

4. The method of any of claims 1 to 3, wherein the incident signal (114) is received from a first node (102), wherein the backscattered signal (112) is transmitted to the first node (102) or to a second node (103).

5. The method of any of claims 1 to 4, wherein: the intermodulation products are generated by non-linearities in the rectifier (118) or the envelope detector (120) when said antenna (104) is subjected to the incident signal (114); or the device (100) comprises a second antenna (104), wherein the intermodulation products are generated by non-linearities in the rectifier (118) or the envelope detector (120) when the second antenna (104) is subjected to the incident signal (114).

6. The method of any of claims 1 to 5, further comprising: receiving (202) signaling, wherein the generated signal is generated based on said signaling.

7. The method of claim 6, wherein the received signaling indicates: the subcarrier spacing of the incident signal (114); and / or a frequency of the generated signal.

8. The method of any of claims 6 to 7, wherein: said signaling is received from a node (102) from which the incident signal (114) is received; or said signaling is received from a node (103) to which the backscattered signal (112) is transmitted.

9. The method of any of claims 1 to 8, wherein the backscattered signal (112) also comprises odd-numbered ordered intermodulation products higher than third order intermodulation products.

10. A device (100) for backscattering an incident signal, wherein the device is configured to perform the method of any of claims 1 to 9.

11. The device (100) of claim 10, further comprising a bandpass filter (116) that performs the filtering (204).

12. The device (100) of claim 10, further comprising a baseband processor (108) that performs the generating (206).

13. The device (100) of claim 10, further comprising a radio frequency, RF, switch, (106) that performs the switching (208).

14. A method (400) performed by a receiver node (102, 103) for receiving a backscattered signal (112), the method comprising: receiving (402) the backscattered signal (112) comprising intermodulation products or harmonics; filtering (404) frequency components of the backscattered signal (112) in respective bandpass filters; performing channel estimation (406) on the filtered frequency components of thebackscattered signal (112) to generate coherent intermodulation products or harmonics; and combining (408) the coherent intermodulation products or harmonics to increase a signal to noise ratio of the backscattered signal (112).

15. The method of claim 14, wherein the filtering comprises filtering the intermodulation products to suppress frequency components outside of a fundamental frequency band of the backscattered signal (118).

16. A receiver node (102, 103) for receiving a backscattered signal, wherein the receiver node is configured to perform the method of any of claims 14 to 15.

17. The receiver node (102, 103) of claim 16, further comprising: an antenna (304) that performs the receiving (402) 18. The receiver node (102, 103) of claim 16, further comprising a plurality of bandpass filters (306-1, 306-2) that perform the filtering (404).

19. The receiver node (102, 103) of claim 16, further comprising a plurality of channel estimators (308-1, 308-2) that perform the channel estimation (406).

20. The receiver node (102, 103) of claim 16, further comprising a mixer (310) that performs the combining (408).

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