Non-linear interference cancellation across aggressor transmitters and victim receivers

Systems and methods are disclosed to implement non-linear interference cancellation (NLIC) across chips or dies in communication systems to cancel or mitigate self-jamming interference. A victim transceiver may receive an analog baseband transmit (Tx) signal from an aggressor transceiver. The analog baseband Tx signal may be tapped from a digital analog converter (DAC) of the aggressor transceiver. Alternatively, the analog baseband Tx signal may be generated by the aggressor transceiver using an auxiliary down-conversion and filtering stage. The victim transceiver may receive a composite baseband Rx signal from the victim transceiver front-end. The composite baseband Rx signal includes the desired Rx signal and an interference signal. The victim transceiver may sample the analog baseband Tx signal to generate a digital signal replica of the analog baseband Tx signal for the NLIC operation to cancel or mitigate the interference signal present in the composite baseband Rx signal.

TECHNICAL FIELD

This application generally relates to communication systems. In particular, this application relates to cancelling self-jamming interference induced by a transmitter on a receiver of a communication system when the transmitter and the receiver are implemented as separate chips or dies of the communication system.

BACKGROUND

Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. It is common to integrate multiple radios into a single communication system. For example, smartphones may have radios to support cellular communication, WiFi, GPS, and Bluetooth, etc., each operating on a different frequency band. Even for systems that have just a single radio, the radio may be a frequency division duplex (FDD) system, in which the transmit (Tx) and receive (Rx) links simultaneously operate on different frequency bands. In these systems, the strongest interference on an Rx signal may be caused by self-jamming leakage from a Tx signal that is simultaneously transmitted by the systems. For example, the Tx signal may leak to the Rx path through the finite isolation between the Tx and Rx paths. Although in a different frequency band, the Tx leakage signal may cause co-channel interference on the intended Rx signal due to non-linearities in the Rx chain. For example, non-linear behavior in the radio frequency (RF) down conversion components: such as low noise amplifier (LNA), mixer, switches, filters, data converters, etc., operating on the Tx leakage signal may generate interference in the Rx frequency band. Another scenario for Tx self-jamming arises when non-linearities present in the transmitter chain generate spectral re-growth such as harmonics of the Tx frequency that fall in the Rx frequency band. The effects of the self-jamming interference due to non-linearities of the Tx or the Rx chains are degradation in the performance of the communication systems.

If the Tx and Rx chains are on the same die, the Tx waveforms that generate the interference are known. Hence, the interference component at the victim Rx chain may be constructed via an adaptive non-linear interference cancellation (NLIC) scheme. For example, the NLIC may generate, based on the known baseband Tx signal, an estimate of the interference in the baseband Rx signal due to the Tx/Rx non-linearities. The Rx chain may remove the estimated interference from the baseband Rx signal to cancel or to mitigate the interference. In this regard, if the aggressor baseband module and victim baseband module are on the same die, NLIC may be implemented by streaming the digital baseband Tx samples from the aggressor baseband module to the victim baseband module via an internal bus or a shared memory.

However, there are situations where it may not be desirable to integrate the Tx and Rx chains, such as the aggressor baseband module and the victim baseband module, on the same die or chip. For example, integration of the Tx/Rx chains from the same radio or different radios on one transceiver die carries the risk that design bugs, design enhancements, or technology upgrade in the Tx or Rx chains may require a re-spin of the entire design. In another example, the bus/memory shared by the aggressor/victim baseband modules may become a limiting factor when the Tx and Rx chains are running at maximum speed or when trying to optimize the performance of the Tx or Rx chain. Furthermore, it may be desirable to pair Tx and Rx chipsets from different vendors together for specific feature-set requirements. Frequently, the aggressor transceiver and the victim transceiver may use different clocks. In these circumstances, the NLIC architecture complexity may become prohibitive as it would require additional modules to compensate for time drift and/or frequency drift between aggressor and victim clocks, increasing the complexity of the design. As such, there is a need for a solution to more easily implement NLIC if the aggressor and victim baseband modules are not on the same chip or on the same die.

SUMMARY

Systems and methods are disclosed for implementing non-linear interference cancellation (NLIC) across chips or dies in communication systems to cancel or mitigate self-jamming interference. Self-jamming interference may arise when Tx leakage signal causes co-channel interference on the Rx signal due to non-linearities in the Tx or Rx chains of the communication systems. When the Tx and the Rx chains are implemented in separate chips or dies, cancellation or mitigation of the self-jamming interference is implemented across chips or dies. For example, a victim Rx chip implementing NLIC may be paired to an aggressor Tx chip of a FDD radio to cancel co-channel interference on the Rx signal due to Tx or Rx non-linearities. Similarly, a victim transceiver of a WiFi radio implementing NLIC may be paired to an aggressor transceiver of a 3GPP Long Term Evolution (LTE) radio to cancel co-channel interference on the Rx WiFi signal due to the harmonics on the LTE signal.

A method for NLIC by a victim receiver is disclosed. The method includes receiving an analog Tx signal from an aggressor transmitter. The method also includes receiving by a digital backend of the victim receiver a composite Rx signal from an Rx front-end of the victim receiver. The composite Rx signal includes a desired Rx signal and an interference signal, where the interference signal includes a non-linear distortion of a radio-frequency (RF) Tx signal. The method further includes generating a digital baseband Tx signal replica of the analog Tx signal, and generating a digitized composite Rx signal from the composite Rx signal. The method further includes determining an estimate of the interference signal from the digital baseband Tx signal replica. The method further includes removing the estimate of the interference signal from the digitized composite Rx signal.

A method for generating an auxiliary analog Tx signal from an aggressor transmitter for NLIC by a victim receiver is disclosed. The method includes receiving an analog Tx signal from a digital backend of the aggressor transmitter. The method also includes generating an RF Tx signal from the analog Tx signal. The method further includes generating an auxiliary analog Tx signal from the RF Tx signal. The method further includes providing the auxiliary analog Tx signal to the victim receiver for NLIC of a non-linear distortion of the RF Tx signal received by the victim receiver.

An apparatus for NLIC disclosed. The apparatus includes one or more ADCs, a memory, and one or more processors that execute instructions read from the memory. The processors execute the instructions to receive an analog Tx signal from an aggressor transmitter. The processors also execute the instructions to receive a composite Rx signal from an analog front-end of the apparatus. The composite Rx signal includes a desired Rx signal and an interference signal, where the interference signal includes a non-linear distortion of a radio-frequency (RF) Tx signal. The processors further execute the instructions to activate the ADCs to sample the analog Tx signal to generate a digital baseband Tx signal replica of the analog Tx signal, and to sample the composite Rx signal to generate a digitized composite Rx signal. The processors further execute the instructions to determine an estimate of the interference signal from the digital baseband Tx signal replica. The processors further execute the instructions to remove the estimate of the interference signal from the sampled composite Rx signal.

An apparatus to generate an analog Tx signal from the apparatus for NLIC by a victim receiver is disclosed. The apparatus includes a memory, and one or more processors that execute instructions read from the memory. The processors execute the instructions to receive an analog Tx signal from a digital backend of the apparatus. The processors also execute the instructions to generate an RF Tx signal from the analog Tx signal. The processors further execute the instructions to generate an auxiliary analog Tx signal from the RF Tx signal. The processors further execute the instructions to provide the auxiliary analog Tx signal to the victim receiver for NLIC of a non-linear distortion of the RF Tx signal received by the victim receiver.

A non-transitory machine-readable medium that stores machine-readable instructions is disclosed. One or more processors may execute the instructions to perform steps for NLIC. The instructions include receiving an analog Tx signal from an aggressor transmitter. The instructions also include receiving a composite Rx signal from an Rx analog front-end. The composite Rx signal includes a desired Rx signal and an interference signal, where the interference signal includes a non-linear distortion of a RF Tx signal. The instructions further include generating a digital baseband Tx signal replica of the analog Tx signal, and generating a digitized composite Rx signal from the composite Rx signal. The instructions further include determining an estimate of the interference signal using the digital baseband Tx signal replica. The instructions further include removing the estimate of the interference signal from the digitized composite Rx signal.

A non-transitory machine-readable medium that stores machine-readable instructions is disclosed. One or more processors may execute the instructions to perform steps for generating an auxiliary analog Tx signal for NLIC by a victim receiver. The instructions include receiving an analog Tx signal from a digital backend. The instructions also include generating an RF Tx signal from the analog Tx signal. The instructions further include generating the auxiliary analog Tx signal from the RF Tx signal. The instructions further include providing the auxiliary analog Tx signal to the victim receiver for NLIC of a non-linear distortion of the RF Tx signal received by the victim receiver.

A system for NLIC across chips or dies is disclosed. The system includes means for receiving an analog Tx signal from an aggressor transmitter. The system also includes means for receiving a composite Rx signal from an analog front-end of the system. The composite Rx signal includes a desired Rx signal and an interference signal, where the interference signal includes a non-linear distortion of a radio-frequency (RF) Tx signal. The system further includes means for generating a digital baseband Tx signal replica of the analog Tx signal, and means for generating a digitized composite Rx signal from the composite Rx signal. The system further includes means for determining an estimate of the interference signal using the digital baseband Tx signal replica. The system further includes means for removing the estimate of the interference signal from the digitized composite Rx signal.

A system to generate an analog Tx signal from the system for NLIC by a victim receiver is disclosed. The system includes means for receiving an analog Tx signal from a digital backend of the system. The system also includes mean for generating an RF Tx signal from the analog Tx signal. The system further includes means for generating an auxiliary analog Tx signal from the RF Tx signal. The system further includes means for providing the auxiliary analog Tx signal to the victim receiver for NLIC of a non-linear distortion of the RF Tx signal received by the victim receiver.

DETAILED DESCRIPTION

Systems and methods are disclosed to implement non-linear interference cancellation (NLIC) across chips or dies in communication systems to cancel or mitigate self-jamming interference. A communication system may include multiple transceivers operating in different frequency bands in which a Tx leakage signal from a first transceiver induces self-jamming interference on an Rx signal of a second transceiver. A communication system may also be an FDD transceiver in which the Tx leakage signal induces self-jamming interference on the Rx frequency band of the FDD transceiver. In these transceivers, the Tx chain generating the Tx leakage signal and the Rx chain receiving the self-jamming interference may be on different chips or dies. A die in the context of integrated circuits is a small block of semiconducting material, on which a given functional circuit is fabricated.

An aggressor transceiver of a communication system may include a digital backend that generates a Tx signal in baseband and an analog frontend that generates the Tx signal in RF from the baseband Tx signal. The RF Tx signal may leak to a victim transceiver of the communication system through finite isolation between the aggressor transceiver and the victim transceiver (e.g., duplexer, antenna coupling, circuit electromagnetic interference (EMI), ground coupling). The victim transceiver may include an analog frontend that receives a composite RF signal comprising the desired Rx signal in an Rx frequency band and the RF Tx leakage signal. Even though the RF Tx leakage signal may be in a different frequency band, non-linearities in the RF components of the analog frontend of the victim transceiver operating on the RF Tx leakage signal may generate co-channel interference in the Rx frequency band. For example, 2ndorder intermodulation (IM2) distortion of the RF Tx leakage signal in a RF down-converter of the victim transceiver may introduce interference to the desired RF signal. If there is an additional external narrowband jamming signal, cross modulation of the RF Tx leakage signal with the jamming signal in the RF down-converter may also cause interference. The interference signal may appear with the desired Rx signal in a composite baseband Rx signal from the output of the analog frontend. A digital backend of the victim transceiver may receive the composite baseband Rx signal to demodulate and decode the desired Rx signal. The interference signal reduces the signal to interference and noise ratio of the desired Rx signal, degrading performance of the victim transceiver, causing a decrease in throughput, and increasing the likelihood of dropped calls at the cell edge in cellular communication.

Self-jamming interference may also arise when non-linearities in the Tx RF components of the analog frontend of the aggressor transceiver generate spectral re-growth of the RF Tx signal that overlaps with the Rx frequency band. For example, a third harmonic distortion (H3D) of the Tx carrier signal f0from an RF up-converter of the aggressor transceiver may introduce spectral sideband at 3f0, which may fall in the Rx frequency band of the victim transceiver. The desired Rx signal and the interference signal in the Rx frequency band are down-converted by the analog frontend of the victim transceiver. The interference signal may appear with the desired Rx signal in a composite baseband signal from the output of the analog frontend. Similar to the interference from the IM2 distortion of the victim transceiver, the H3D interference may degrade the performance of the victim transceiver by causing a decrease in throughput and increasing the likelihood of dropped calls at the cell edge in cellular communication.

To cancel or mitigate the interference, the digital backend of the victim transceiver may receive the Tx signal from the aggressor transceiver as an analog baseband signal. The analog baseband Tx signal may be received from the digital backend or the analog frontend of the aggressor transceiver. In one or more embodiments, the analog baseband Tx signal may be tapped or spilled from a digital analog converter (DAC) of the digital backend of the aggressor transceiver. The same analog baseband Tx signal may go to the analog frontend of the aggressor transmitter to be up-converted to the RF Tx signal. In one or more embodiments, the analog frontend of the aggressor transceiver may down-convert the RF Tx signal to generate an auxiliary analog baseband signal using an auxiliary down-conversion and filtering stage. In this regard, the down-converted analog baseband Tx signal may include the self-jamming interference caused by the non-linearities in the Tx RF components of the analog frontend, e.g., the spectral re-growth from non-linearities in a power amplifier and/or switches of the aggressor transceiver. This spectral re-growth may include the close-in intermodulation interference at the Tx carrier frequency f0.

The digital backend of the victim transceiver may receive the analog baseband Tx signal from the aggressor transceiver as well as the composite baseband Rx signal from the analog frontend of the victim transceiver. The composite baseband Rx signal includes the desired Rx signal and the interference signal. The digital backend of the victim transceiver may remove the interference signal by adaptively estimating the non-linear interference component in a NLIC module from a digital signal replica of the analog baseband Tx signal obtained at the victim transceiver as will be further detailed. To implement the NLIC, the digital backend may sample the analog baseband Tx signal using an analog digital converter (ADC), referred to as the baseband Tx ADC, to generate the digital signal replica of the analog baseband Tx signal. The baseband Tx ADC may be separate from a baseband Rx ADC used to sample the composite baseband Rx signal from the analog frontend to generate a digitized composite baseband Rx signal. The two ADCs may run on the same sampling clock so that the digital signal replica of the analog baseband Tx signal may be used by the NLIC module to estimate the non-linear interference signal that is sample aligned with the received interference component present in the digitized composite baseband Rx signal from which the estimated non-linear interference signal is to be removed. Advantageously, the digital backend of the victim transceiver does not need to run a frequency and/or time tracking loop to compensate for the frequency/time drift between the clocks in the aggressor transceiver and the victim transceiver. In addition, because the victim transceiver does not receive a digital baseband Tx signal replica that was digitized at a different clock frequency from the sampling clock in the victim transceiver, there is no need to re-sample the digital baseband TX signal replica to align the samples with the digitized composite baseband Rx signal.

The NLIC module may process the digital signal replica of the analog baseband Tx signal to generate an estimate of the non-linear interference component present in the digitized composite baseband Rx signal. The NLIC module may be a digital adaptive filter that applies a non-linear distortion to the digital signal replica of the analog baseband Tx signal to construct an estimate of the non-linear interference component. The digital backend may remove the estimate of the non-linear interference component from the digitized composite baseband Rx signal. The removal of the estimated non-linear interference component from the digitized composite baseband Rx signal may generate a residual interference signal. The residual interference signal may be minimized using a minimum square error (MSE) algorithm to generate an estimate of the non-linear interference component that closely approximates the received non-linear interference component present in the digitized composite baseband Rx signal.

FIG. 1shows two communication systems in a communication network in which NLIC across chips or dies may be implemented in the communication systems according to one or more embodiments of the present disclosure. A user terminal102communicates with a base station104over a wireless network. User terminal102may be a smartphone, a tablet computer, a personal digital assistant (PDA), a notebook computer, a laptop, or other communication and/or computing devices. User terminal102may be stationary, portable, or mobile. User terminal102may also be referred to as a user equipment, a subscriber unit, a user node, a mobile station, or using other terminology. Base station104may be a base station in a cellular network, an access point (AP) in a WiFi network, or other stationary, portable, or mobile communication terminals. The wireless communication network over which user terminal102and base station104communicate may be a multiple access network, a point-to-point network, a mesh network, etc. Examples of multiple access networks may include Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), etc., that are found in cellular, wide-area network (WAN), local-area network (LAN), personal-area network (PAN), etc. Systems and methods for NLIC across chips or dies discussed here may also be applicable to GPS, UWB, RFID, or wired communication systems such as Ethernet, cable, fiber, power-line, etc.

User terminal102transmits data to base station104over an uplink106. Base station104transmits data to user terminal102over a downlink108. In an FDD system, uplink106and downlink108operate simultaneously over different frequency bands. Self-jamming interference in user terminal102may occur when non-linearities in the Tx path or Rx processing of user terminal102causes Tx frequency band of uplink106to interfere with the Rx frequency band of downlink108. Similarly, self-jamming interference in base station104may occur when non-linearities in the Tx or Rx processing of base station104causes Tx frequency band of downlink108to interfere with the Rx frequency band of uplink106.

FIG. 2shows a system block diagram of an aggressor transmitter and a victim receiver of a communication system in which an analog Tx signal is spilled from a digital-to-analog converter of an aggressor transmitter and is used by a victim receiver for NLIC according to one or more embodiments of the present disclosure. The communication system ofFIG. 2may be found in user terminal102or base station104ofFIG. 1.

The communication system includes an aggressor transmitter202and a victim receiver204. Aggressor transmitter202and victim receiver204may be from the same transceiver of an FDD communication system or from different transceivers of a multi-radio communication system. Aggressor transmitter202includes a digital backend206and an analog frontend214. Similarly, victim receiver204includes a digital backend240and an analog frontend234. In one or more embodiments, digital backend206and analog frontend214of aggressor transmitter202may be implemented in the same chip or die. Similarly, digital backend240and analog frontend234of victim receiver204may be implemented in the same chip or die.

Digital backend206of aggressor transmitter202generates Tx data for up-conversion by analog frontend214. Digital backend206includes a controller208, a Tx baseband (Tx-BB) modulator210, and a DAC212. Tx-BB modulator210performs coding, interleaving, and modulation, etc., of data from one or more data sources to generate digital baseband Tx data under the control of controller208. Controller208may execute instructions stored in a memory211to control the generation of the digital baseband Tx data. DAC212converts the digital baseband Tx data received from Tx-BB modulator210to an analog baseband Tx signal. In one or more embodiments, the analog signal from DAC212may be at an intermediate frequency (IF) if Tx-BB modulator210digitally up-converts the digital baseband Tx data to the IF.

The analog baseband Tx signal is routed as a signal213to digital backend240of victim receiver204for NLIC. Analog frontend214of aggressor transmitter202also receives the analog baseband Tx signal for up-conversion to an RF Tx signal. Analog frontend214includes a BB analog module216and an RF up-converter218. BB analog module216filters, amplifies, and conditions the analog baseband Tx signal to generate a signal suitable for transmission over the communication channel. In one or more embodiments, BB analog module216may further condition the Tx signal for beamforming or for transmission over a multiple-input multiple-output (MIMO) channel. RF up-converter218up-converts the Tx signal from BB analog module216to the RF frequency band of the RF Tx signal. RF up-converter218may convert the Tx signal from baseband to the RF frequency band using a single-stage mixer or use a multi-stage up-conversion process involving several mixers and one or more IFs. The RF Tx signal may occupy the full bandwidth of the Tx channel or may only occupy one or more sub-bands of the Tx channel.

A power amplifier PA220amplifies the RF Tx signal from analog frontend214to a desired power level for transmission through an antenna222. Operation of analog frontend214and PA220may also be under the control of controller208. For example, controller208may determine the RF frequency band of the Tx channel, the sub-bands within the Tx channel, and the power level of the RF Tx signal.

Non-idealities in BB analog module216, RF up-converter218, and/or PA220generate spectral re-growth of the RF Tx signal that overlaps with the Rx frequency band received by victim receiver204. For example, non-linearities in the amplifier or filter of BB analog module216, in one or more mixers of RF up-converter218, and/or in PA220may introduce spectral re-growth in the RF Tx signal. Linearities in PA220is a function of current consumption and the linear operating range of PA220may be traded off against power, area, and/or cost savings during design of aggressor transmitter202. The result of the design trade-off may be to allow for some spectral re-growth when PA220is operated over the non-linear region. In one or more embodiments, if RF Tx signal224has a RF carrier frequency of f0, the third harmonic distortion (H3D) of RF Tx signal224may introduce undesired energy at 3f0, which may fall in the Rx frequency band of RF Rx signal226received by victim receiver204. Other mthharmonic distortions of RF Tx signal224may similarly introduce undesired energy at mthmultiples of f0, the cancellation of which also falls under the scope of the present disclosure.

Victim receiver204receives RF Rx signal226that is the desired Rx signal centered at Rx carrier frequency fRxthrough antenna228. Victim receiver204may receive self-jamming interference in the Rx frequency band due to the H3D of RF Tx signal224through antenna228or through limited isolation between aggressor transmitter202and victim receiver204. Received RF Rx signal226is filtered by an external filter230(e.g., a duplexer, switch, or a surface acoustical wave (SAW) filter). The filtered Rx signal is amplified by a low noise amplifier (LNA)232.

Analog frontend234of victim receiver204receives the filtered and amplified Rx signal from LNA232. Analog frontend234includes an RF down-converter236and a BB analog module238. RF down-converter236down-converts the Rx signal from the RF frequency band (e.g., Rx carrier frequency fRxmay be close to 3f0) down to baseband. RF down-converter236may down-convert the Rx signal from RF to baseband using a single-stage mixer or through a multi-stage down-conversion process involving several mixers and one or more IFs. BB analog module238filters, amplifies, conditions the baseband signal from RF down-converter236, and outputs a composite baseband Rx signal239from analog frontend234for demodulation by digital backend240. In one or more embodiments, analog frontend234may output the Rx signal at IF.

Non-idealities in the Rx signal processing chain may generate co-channel interference even if RF Tx signal224does not have spectral re-growth that overlaps with the Rx frequency band centered at fRx. For example, IM2 distortion of one or more mixers of RF down-converter236operating on leakage of RF Tx signal224may introduce interference component to composite baseband Rx signal239. RF Tx signal224may leak to victim receiver204due to the large difference in signal power between RF Tx signal224and RF Rx signal226and due to limited isolation between aggressor transmitter202and victim receiver204. Non-linearities in external filter230, in LNA232, and/or in the amplifier or filter of BB analog module238operating on the leakage of RF Tx signal224may also cause co-channel interference.

As such, composite baseband Rx signal239generated by analog frontend234is a composite signal that contains the desired Rx signal and an interference component. Digital backend240of victim receiver204receives composite baseband Rx signal239from analog frontend234and analog baseband Tx signal213from digital backend206of aggressor transmitter202. Digital backend240samples composite baseband Rx signal239using an ADC246to generate a digitized composite baseband Rx signal252. To implement NLIC across different chips or dies, digital backend240samples analog baseband Tx signal213using a second ADC, ADC2242, to generate a digital signal replica of analog baseband Tx signal248. ADC246and ADC2242run on sampling clocks generated by a clock module244. The two ADCs may run on a common sampling clock so that digital signal replica of analog baseband Tx signal248may be used in a NLIC module to estimate the non-linear interference signal that is sample aligned with the received non-linear interference component present in digitized composite baseband Rx signal replica252.

An NLIC module250processes digital signal replica of analog baseband Tx signal248to generate an estimate of the non-linear interference component present in digitized composite baseband Rx signal252under the control of a controller262. NLIC module250may be a digital adaptive filter that applies a non-linear distortion to digital signal replica of analog baseband Tx signal248to construct an estimated interference signal254. In one or more embodiments, NLIC module250may be a non-linear filter that constructs estimated interference signal254to represent a sum of an estimate of the H3D interference from RF Tx signal224, of an estimate of the IM2 interference from the RF processing of victim receiver204, and of estimates of other distortions induced by the leakage of RF Tx signal224. A summer256subtracts estimated interference signal254from digitized composite baseband Rx signal252to cancel or mitigate the non-linear interference component present in digitized composite baseband Rx signal252. Summer256generates a post-cancellation signal258as a representation of the desired Rx signal Summer256may also generate an error signal to represent a residual of the non-linear interference component after NLIC. NLIC module250may minimize the error signal using a minimum square error (MSE) algorithm to adaptively generate estimated interference signal254that closely approximates the non-linear interference component present in digitized composite baseband Rx signal252.

A demodulator—decoder module260demodulates, de-interleaves, and decodes post-cancellation signal258to recover Tx data received in RF Rx signal226under the control of controller262. Controller262may execute instructions stored in a memory264to configure demodulator-decoder module260with Tx parameters such as the coding scheme, coding rate, modulation scheme, etc., used by Tx-BB modulator210of aggressor transmitter202to generate the Tx data. Such Tx parameters may be communicated by controller208of aggressor transmitter202to controller262of victim receiver204via a data interface.

Aggressor transmitter202may also communicate Tx information209on its Tx operation to victim receiver204to aid the NLIC. For example, controller208of aggressor transmitter202may communicate Tx information209pertaining to the Tx carrier frequency (e.g., f0), transmit power, Tx sub-bands used, configuration information of analog frontend214of aggressor transmitter202, etc., to controller262of victim receiver204via the data interface. Digital backend240of victim receiver204may use Tx information209to enable NLIC module250. For example, controller262may enable NLIC module250for cancellation of IM2 interference if it determines from the Tx sub-band information, the Tx carrier frequency, the Tx power, and knowledge of the frequency of a local oscillator (LO) of RF down-converter module236of victim receiver204that non-linearities in RF down-converter module236operating on the leakage of RF Tx signal224may cause co-channel interference on the Rx frequency band of RF Rx signal226. In one or more embodiments, controller262may enable NLIC module250for cancellation of H3D interference if it determines from the Tx sub-band information and the Tx carrier frequency that the third harmonics of RF Tx signal224may overlap with the Rx frequency band of RF Rx signal226. In one or more embodiments, controller262may fine tune the MSE algorithm of NLIC module250based on Tx information209. For example, controller262may initialize the MSE algorithm of NLIC module250for faster convergence of estimated interference signal254to the non-linear interference component present in digitized composite baseband Rx signal252using Tx information209. The data interface between aggressor transmitter202and victim receiver204may be a standardized interface such as the WCI-2 interface.

FIG. 3shows a flow chart for NLIC across an aggressor transmitter and a victim receiver of a communication system according to one or more embodiments of the present disclosure. For example, the processing steps ofFIG. 3may be practiced by digital backend240of victim receiver204ofFIG. 2for NLIC of self-jamming interference from aggressor transmitter202.

In302, the victim receiver receives an analog Tx signal from the aggressor transmitter. The analog Tx signal may be a baseband signal that will be up-converted to the RF frequency band of the Tx channel. For example, the analog Tx signal may be analog baseband Tx signal213output by DAC212as shown inFIG. 2. Digital backend240of victim receiver204may receive analog baseband Tx signal213from digital backend206of aggressor transmitter202. In one or more embodiments, the analog Tx signal may be at an IF.

In304, the victim receiver receives an analog composite Rx signal that includes the desired Rx signal and the interference signal. The interference signal may be self-jamming interference from non-linearities in the Tx RF components of the aggressor transmitter, such as H3D of the RF Tx signal that falls into the Rx frequency band. In one or more embodiments, the interference signal may be co-channel interference from non-linearities in the RF components of the victim receiver operating on leakage of the RF Tx signal from the aggressor transmitter. The analog composite Rx signal may be a baseband signal. For example, the analog composite Rx signal may be composite baseband Rx signal239from BB analog module238. Digital backend240of victim receiver204may receive composite baseband Rx signal239from analog frontend234of victim receiver204. In one or more embodiments, the analog composite Rx signal may be at the same IF as the analog Tx signal.

In306, the victim receiver generates a digital signal replica of the analog Tx signal. The victim receiver may sample the analog Tx signal at a sufficient sampling rate to replicate the digital baseband Tx signal as transmitted by the aggressor transmitter. For example, digital backend240of victim receiver204may sample analog baseband Tx signal213using ADC2242to replicate analog baseband Tx signal213in a digital form (i.e., generating digital signal replica of analog baseband Tx signal248).

In308, the victim receiver generates a digitized composite Rx signal. The victim receiver may sample the composite Rx signal at the same sampling rate as that used to sample the analog Tx signal. For example, digital backend240of victim receiver204may generate digitized composite baseband Rx signal252by using ADC246to sample composite baseband Rx signal239at the same sampling rate as that used by ADC2242in sampling analog baseband Tx signal213. By sampling composite baseband Rx signal239and analog baseband Tx signal213at the same sampling rate, digital signal replica of analog baseband Tx signal248may be processed by NLIC module250to generate an estimate of the interference signal (i.e., estimated interference signal254) that is sample-aligned with the received non-linear interference component present in digitized composite baseband Rx signal252. In one embodiment, NLIC module250may sample align estimated interference signal254and the received non-linear interference component present in digitized composite baseband Rx signal252by inserting adjustable delays in NLIC module250to compensate for the difference in path delays between analog baseband Tx signal213received from aggressor transmitter202and composite baseband Rx signal239received from analog frontend234of victim receiver204.

In310, the victim receiver determines an estimate of the interference signal from the digital signal replica of the analog Tx signal. The victim receiver may use the NLIC module to adaptively apply a non-linear distortion to the digital signal replica of the analog Tx signal to generate the estimated interference signal. For example, NLIC module250of digital backend240may process digital signal replica of analog baseband Tx signal248to generate estimated interference signal254. NLIC module250may use a MSE algorithm to adaptively generate estimated interference signal254to minimize an error signal. The error signal may represent a residual of the non-linear interference component after NLIC as determined from the difference between estimated interference signal254and the received non-linear interference component present in digitized composite baseband Rx signal252.

In312, the victim receiver removes the estimated interference signal from the digitized composite Rx signal to cancel or mitigate the interference component present in the digitized composite Rx signal. For example, summer256of digital backend240may subtract estimated interference signal254from digitized composite baseband Rx signal252to generate post-cancellation signal258to approximate the desired Rx signal. The victim receiver may demodulate the interference-mitigated digitized composite Rx signal to recover the desired Rx data. For example, demodulator decoder260may demodulate post-cancellation signal258to receive the desired Rx data.

FIG. 4shows a system block diagram of an aggressor transmitter and a victim receiver of a communication system in which an analog baseband Tx signal down-converted from the RF Tx signal of the aggressor transmitter is used by a victim receiver for NLIC according to one or more embodiments of the present disclosure.FIG. 4differs fromFIG. 2in how the analog baseband Tx signal is generated. InFIG. 2, the analog baseband Tx signal is tapped from DAC212of digital backend206. However, there may be situations when DAC212is not readily accessible, or it may be undesirable to tap DAC212because loading and/or impedance mismatch on the output of DAC212may introduce noise or otherwise degrade the signal integrity of the analog baseband Tx signal.FIG. 4shows an alternative embodiment in which analog frontend214down-converts the RF Tx signal to generate the analog baseband Tx signal. To distinguish between the analog baseband Tx signal generated by digital backend206of aggressor transmitter202from the analog baseband Tx signal generated by analog frontend214, the analog baseband Tx signal down-converted from the RF Tx signal by analog frontend214is referred to as the auxiliary analog baseband Tx signal.

Operations of digital backend206of aggressor transmitter202ofFIG. 4may be the same as that described in the discussion forFIG. 2and so is not repeated. Analog frontend214receives an analog baseband Tx signal215from digital backend206. Analog baseband Tx signal215is tapped from the same DAC (i.e., DAC212) as analog baseband Tx signal213ofFIG. 2. Analog frontend214up-converts analog baseband Tx signal215to generate RF Tx signal224as inFIG. 2. RF Tx signal224has a RF carrier frequency of f0. A coupler may sense RF Tx signal224at the output of PA220. When sensed, RF Tx signal224is routed back to analog frontend214in addition to being transmitted through antenna222. An RF auxiliary down-converter402down-converts RF Tx signal224from the RF carrier frequency (e.g., f0) down to baseband. RF auxiliary down-converter402may use a single-stage mixer or may use a multi-stage down-conversion process involving several mixers to perform the down-conversion. RF auxiliary down-converter402and RF up-converter218may share a Tx_LO module408that provides one or more LOs for the one or more mixers. A BB analog filter404filters, amplifies, and/or conditions the baseband signal from RF auxiliary down-converter402and outputs an auxiliary analog baseband Tx signal406. Digital backend240of victim receiver204receives auxiliary analog baseband Tx signal406from analog frontend214of aggressor transmitter202. In one or more embodiments, auxiliary analog baseband Tx signal406may be at an IF, such as when RF auxiliary down-converter402down-converts RF Tx signal224to IF. Operations of the RF processing of the RF Rx signal received at antenna228at victim receiver204to generate composite baseband Rx signal239may be the same as that described in the discussion forFIG. 2. Similarly, operations of processing auxiliary analog baseband Tx signal406and composite baseband Rx signal239for NLIC may be the same as that described in the discussion forFIG. 2. These discussions are not repeated for brevity.

RF auxiliary down-converter402and BB analog filter404may be existing modules used for other functionalities. Controller208may manage the time sharing of RF auxiliary down-converter402and BB analog filter404with the other functionalities. As such, analog frontend214may down-convert RF Tx signal224to generate auxiliary analog baseband Tx signal406without incurring a penalty in area or cost. Advantageously, because auxiliary analog baseband Tx signal406is down-converted from RF Tx signal224that is generated by the RF components in analog frontend214, auxiliary analog baseband Tx signal406may include the self-jamming interference caused by the non-linearities in the Tx RF components of analog frontend214. For example, auxiliary analog baseband Tx signal406may include the interference from H3D of RF Tx signal224caused by non-linearities in BB analog module216, RF up-converter218, and/or PA220of aggressor transmitter202. The presence of the H3D interference in auxiliary analog baseband Tx signal406received by digital backend240of victim receiver204may eliminate the need for NLIC module250to estimate the H3D interference. Estimated interference signal254may contain an accurate replica of the H3D interference that may be removed from digitized composite baseband Rx signal252to cancel or mitigate the H3D interference.

FIG. 5shows a flow chart for the aggressor transmitter ofFIG. 4to generate the auxiliary analog baseband Tx signal from the RF Tx signal according to one or more embodiments of the present disclosure. For example, the processing steps ofFIG. 5may be practiced by analog frontend214of aggressor transmitter202ofFIG. 4to generate auxiliary analog baseband Tx signal406.

In502, the aggressor transmitter receives an analog baseband Tx signal. The analog baseband Tx signal may be up-converted to the RF frequency of the Tx channel. For example, analog baseband Tx signal215may be received by analog frontend214from DAC212of digital backend206of aggressor transmitter202. In one or more embodiments, analog baseband Tx signal215may be at an IF.

In504, the aggressor transmitter generates the RF Tx signal from the analog baseband Tx signal. The RF Tx signal has a RF carrier frequency of the Tx channel. For example, aggressor transmitter202may process analog baseband Tx signal215through BB analog module216and RF up-converter218to generate an RF Tx signal from analog frontend214. PA220may amplify the RF Tx signal from analog frontend214to the desired transmit power level to generate RF Tx signal224. RF Tx signal224may have a carrier frequency of f0.

The aggressor transmitter may transmit the RF Tx signal through the antenna. The aggressor transmitter may sense the RF Tx signal to enable the down-conversion of the RF Tx signal. For example, aggressor transmitter202may transmit RF Tx signal224through antenna222. In addition, a coupler may sense RF Tx signal224at the output of PA220to route RF Tx signal224back to analog frontend214for down-conversion.

In508, the aggressor transmitter generates the auxiliary analog baseband Tx signal from the RF Tx signal. For example, RF auxiliary down-converter402of analog frontend214may down-convert RF Tx signal224from a carrier frequency of f0to baseband. BB analog filter404of analog frontend214may filter, amplify, and/or condition the baseband signal from RF auxiliary down-converter402to generate auxiliary analog baseband Tx signal406that may be provided to victim receiver204for NLIC operation. In one or more embodiments, the aggressor transmitter may down-convert the RF Tx signal to IF.

In510, the aggressor transmitter routes the auxiliary analog baseband Tx signal to the victim receiver for the victim receiver to implement NLIC operation to cancel or mitigate the interference on the RF Rx signal. For example, digital backend240of victim receiver204receives auxiliary analog baseband Tx signal406from analog frontend214of aggressor transmitter202for NLIC processing.

It is contemplated that the methods identified herein may be implemented using one or more general purpose or specific purpose computers and/or computer systems, networked and/or otherwise. Where applicable, the ordering of various steps described herein may be changed, combined into composite steps, and/or separated into sub-steps to provide features described herein.

It is also contemplated that various embodiments provided by the present disclosure may be implemented using hardware, firmware, software, or any combinations thereof. For example, the various modules of the analog frontends or the digital backends ofFIG. 2or4may be implemented by one or more processors, including but not limited to, controller208, controller262, and/or other processing components internal or external to the aggressor transmitter or victim receiver. The processors may include a micro-controller, digital signal processor (DSP), or other processing components. The processors may perform specific operations by executing one or more sequences of instructions contained in system memory. Logic may be encoded in a computer readable medium, which may refer to any medium that participates in providing instructions to processors for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. In one embodiment, logic is encoded in non-transitory computer readable medium. Any combination of one or more non-transitory computer readable medium(s) may be utilized. Non-transitory computer-readable media comprise all computer readable media, with the sole exception being a transitory, propagating signal.

Although embodiments of the present disclosure have been described, these embodiments illustrate but do not limit the disclosure. For example, although NLIC operation across chips or dies was discussed with respect to IM2 and H3D interference, embodiments of the present disclosure may encompass NLIC operation between an aggressor transmitter and a victim receiver that are implemented on the same chip or die. In addition, embodiments of the present disclosure may encompass other types of self-jamming interference introduced by the Tx and/or Rx chains (e.g., other harmonics of the RF Tx signal, higher orders of intermodulation interference, or cross modulation of the RF Tx with other Tx frequencies or jammers). It should also be understood that embodiments of the present disclosure should not be limited to these embodiments but that numerous modifications and variations may be made by one of ordinary skill in the art in accordance with the principles of the present disclosure and be included within the scope of the present disclosure as hereinafter claimed.