Patent Publication Number: US-2015065064-A1

Title: Active interference cancellation in analog domain

Description:
BACKGROUND 
     1. Field 
     The disclosure relates generally to the field of interference cancellation systems and methods, and, in particular, to systems and methods for cancelling interference in the analog domain produced by multiple radios operating on the same, adjacent, harmonic/sub-harmonic, or intermodulation product frequencies. 
     2. Background 
     Advanced wireless devices have multiple radios (e.g., WWAN, WLAN, WPAN, GPS/GLONASS, etc.) that operating on the same, adjacent, or harmonic/sub-harmonic frequencies. Various combinations of radios cause co-existence issues due to the relative frequencies. In particular, when one radio is actively transmitting at or close to the same frequency and at a same time that another radio is receiving, the transmitting radio can cause interference to the receiving radio. For example, same band interference may occur between Bluetooth (WPAN) and 2.4 GHz WiFi (WLAN); adjacent band interference between WLAN and LTE band 7, 40, 41; harmonic/sub-harmonic interference may occur between 5.7 GHz ISM and 1.9 GHz PCS; and an intermodulation issue may occur between 7xx MHz and a GPS receiver). 
     Active interference cancellation (AIC) cancels interference between a transmitter radio and a receiver radio by matching gain and phase of a wireless coupling path signal and in a wired AIC path, as shown in  FIG. 6 , where d t  is a transmitted signal from the transmitter (aggressor) radio, and h c  is the coupling channel (wireless coupling path signal) from the transmitter radio to the receiver (victim) radio. 
     AIC may be implemented with respect to RF (radio frequency), BB (baseband), or both RF/BB. AIC in BB only shows limited cancellation performance because the coupling path signal is much stronger than the desired signal strength, easily resulting in the saturation of an LNA (low-noise amplifier) and an ADC (analog-to-digital converter). AIC in RF provides better cancellation performance. Prior art RF AIC techniques include difference calibration methods, such as direct channel estimation and cancellation method, binary search the coupling phase, and LMS (least mean squares)-based adaptive filtering methods. The LMS-based methods can further be categorized into analog LMS and digital LMS methods, depending on where the LMS coefficient is generated. However, interference cancellation performance is limited because of delay mismatch between the wireless coupling path and the wired AIC path. In particular, the use of filters in the AIC path increases the group delay significantly relative to the coupling path. 
     Moreover, existing solutions are generally specific to one particular co-existence combination (e.g., only for the combination of Bluetooth and WLAN) requiring a different solution for each co-existence issue. 
     SUMMARY 
     A method of performing interference cancellation in a communication device having a plurality of transmitters and a plurality of receivers includes, but is not limited to any one or combination of: detecting a co-existence issue between a first transmitter of the plurality of transmitters and a first receiver of the plurality of receivers; selecting the first transmitter for providing an input signal to an interference cancellation (IC) circuit; selecting the first receiver, wherein each of the receivers has a corresponding filter, the first receiver having a filter for filtering a signal received by the first receiver to provide a first filtered signal; configuring the IC circuit based on parameters of the co-existence issue; generating, at the IC circuit, an output signal based on the input signal and the parameters of the co-existence issue; selecting a filter, based on the filter of the first receiver, configured to receive the output signal of the IC circuit, the selected filter configured to filter the output signal to provide a second filtered signal; and generating a cancellation signal based on the first filtered signal and the second filtered signal to reduce interference caused by the first transmitter on the first receiver. 
     In various embodiments, the selected filter is selected to be identical to the filter of the first receiver. 
     In various embodiments, the selected filter is selected to provide a delay on an IC path along which the IC circuit is located that is the same as a delay on a coupling path between an antenna of the first transmitter and an antenna of the first receiver. 
     In various embodiments, the filter of the first receiver may comprise at least one of a band pass filter, a duplexer, and a notch filter. 
     In various embodiments, the selected filter may comprise at least one of a band pass filter, a duplexer, and a notch filter. 
     In various embodiments, the IC circuit may comprise an adaptive filter. 
     In some embodiments, the adaptive filter may comprise a lease mean squares (LMS) adaptive filter. 
     In further embodiments, the LMS adaptive filter may comprise an analog-controlled analog LMS adaptive filter. 
     In further embodiments, the LMS adaptive filter may comprise a digitally-controlled analog LMS adaptive filter. 
     In some embodiments, the adaptive filter may comprise a single-tap filter. 
     In various embodiments, the selecting a filter comprises selecting a filter from among a plurality of filters. 
     In various embodiments, the selecting a filter comprises configuring the filter based on the filter of the first receiver. 
     In various embodiments, the first transmitter and the first receiver are selected based on the co-existence issue between the first transmitter and the first receiver. 
     In various embodiments, the method further includes: detecting a second co-existence issue between the first transmitter of the plurality of transmitters and a second receiver of the plurality of receivers; selecting the first transmitter for providing a second input signal to the IC circuit; selecting the second receiver, the second receiver having a filter for filtering a signal received by the second receiver to provide a third filtered signal; configuring the IC circuit based on the parameters of the second co-existence issue; generating, at the IC circuit, a second output signal based on the second input signal and the parameters of the second co-existence issue; selecting a filter, based on the filter of the second receiver, from among the plurality of filters configured to receive the second output signal of the IC circuit, the selected filter configured to filter the second output signal to provide a fourth filtered signal; and generating a cancellation signal based on the third filtered signal and the fourth filtered signal to reduce interference caused by the first transmitter on the second receiver. 
     In various embodiments, the method further includes: detecting a second co-existence issue between a second transmitter of the plurality of transmitters and a second receiver of the plurality of receivers; selecting the second transmitter for providing a second input signal to the IC circuit; selecting the second receiver, the second receiver having a filter for filtering a signal received by the second receiver to provide a third filtered signal; configuring the IC circuit based on the parameters of the second co-existence issue; generating, at the IC circuit, a second output signal based on the second input signal and the parameters of the second co-existence issue; selecting a filter, based on the filter of the second receiver, from among the plurality of filters configured to receive the second output signal of the IC circuit, the selected filter configured to filter the second output signal to provide a fourth filtered signal; and generating a cancellation signal based on the third filtered signal and the fourth filtered signal to reduce interference caused by the second transmitter on the second receiver. 
     In various embodiments, the first transmitter transmits signals on a frequency within a first frequency band. The first receiver receives signals at a frequency within a second frequency band. The first frequency band at least partially overlaps the second frequency band. 
     In various embodiments, the first transmitter transmits signals on a frequency within a first frequency band. The first receiver receives signals at a frequency within a second frequency band. The first frequency band is adjacent the second frequency band. 
     In various embodiments, the first transmitter transmits signals at a frequency within a first frequency band. The first receiver receives signals at a frequency within a second frequency band. The first frequency band is a non-adjacent lower frequency band. In some embodiments, the first frequency band includes a sub-harmonic frequency of the second frequency band. 
     In various embodiments, the first transmitter transmits signals at a frequency within a first frequency band. The first receiver receives signals at a frequency within a second frequency band. The first frequency band includes a non-adjacent higher frequency band. In some embodiments, the first frequency band includes a harmonic frequency of the second frequency band. 
     In various embodiments, the method further includes detecting an intensity of the interference caused by the first transmitter on the first receiver. The co-existence issue is not detected if the intensity is below a predetermined threshold. 
     In various embodiments, at least one receiver of the plurality of receivers is configured to receive navigation signals. 
     In various embodiments, the detecting a co-existence issue comprises measuring an interference level at the first receiver. 
     In some embodiments, the interference level is based on (i) a frequency separation between a transmit channel of the first transmitter and receive channel of the first receiver and (ii) transit power of the transmitter. 
     In further embodiments, the detecting a co-existence issue comprises comparing the interference level with a pre-defined table. 
     In various embodiments, the detecting a co-existence issue comprises measuring transmission information obtained at the transmitter. 
     In various embodiments, the detecting a co-existence issue comprises detecting a co-existence issue based on a pre-defined table. 
     In various embodiments, the detecting a co-existence issue comprises measuring transmission information obtained at the transmitter. 
     In various embodiments, the method is not performed if the co-existence issue is not detected. 
     An apparatus for reducing interference in a communication device having a plurality of transmitters and a plurality of receivers includes, but is not limited to, means for detecting a co-existence issue between a first transmitter of the plurality of transmitters and a first receiver of the plurality of receivers; means for selecting the first transmitter for providing an input signal to an interference cancellation (IC) circuit; means for selecting the first receiver, wherein each of the receivers has a corresponding filter, the first receiver having a filter for filtering a signal received by the first receiver to provide a first filtered signal; means for configuring the IC circuit based on parameters of the co-existence issue; means for generating, at the IC circuit, an output signal based on the input signal and the parameters of the co-existence issue; means for selecting a filter, based on the filter of the first receiver, configured to receive the output signal of the IC circuit, the selected filter configured to filter the output signal to provide a second filtered signal; and means for generating a cancellation signal based on the first filtered signal and the second filtered signal to reduce interference caused by the first transmitter on the first receiver. 
     A computer program product for reducing interference in a communication device having a plurality of transmitters and a plurality of receivers include a computer-readable storage medium comprising code for (but not limited to): detecting a co-existence issue between a first transmitter of the plurality of transmitters and a first receiver of the plurality of receivers; selecting the first transmitter for providing an input signal to an interference cancellation (IC) circuit; selecting the first receiver, wherein each of the receivers has a corresponding filter, the first receiver having a filter for filtering a signal received by the first receiver to provide a first filtered signal; configuring the IC circuit based on parameters of the co-existence issue; generating, at the IC circuit, an output signal based on the input signal and the parameters of the co-existence issue; selecting a filter, based on the filter of the first receiver, configured to receive the output signal of the IC circuit, the selected filter configured to filter the output signal to provide a second filtered signal; and generating a cancellation signal based on the first filtered signal and the second filtered signal to reduce interference caused by the first transmitter on the first receiver. 
     A system for performing interference cancellation in a communication device includes, but is not limited to, a demultiplexer, an input multiplexer, an output de multiplexer, and a summer. The input multiplexer (MUX) configured to select a transmitter from among a plurality of transmitters. The interference cancellation (IC) circuit is configured to receive an input signal from the selected transmitter of the plurality of transmitters to generate an output signal. The demultiplexer (DEMUX) is configured to select a receiver from among a plurality of receivers. Each of the receivers is associated with a corresponding filter. The filter of the selected receiver is for filtering a signal received by the selected receiver to provide a first filtered signal. The DEMUX is configured to select a filter from among a plurality of filters, based on the filter of the selected receiver. The selected filter is for filtering the output signal to provide a second filtered signal. The summer is configured to combine the first filtered signal and the second filtered signal to provide a cancellation signal to reduce interference caused by the selected transmitter on the selected receiver. 
     A system for performing interference cancellation in a communication device includes, but is not limited to, a plurality of receiver filters, an interference cancellation circuit, a plurality of transmitter filters, and a summer. Each of the receiver filters is associated with a corresponding receiver of the plurality of receivers. The filter of a selected receiver is for filtering a signal received by the selected receiver to provide a first filtered signal. The interference cancellation (IC) circuit is configured to receive an input signal from a selected transmitter of the plurality of transmitters to generate an output signal. A selected transmitter filter is for filtering the output signal to provide a second filtered signal. The selected transmitter filter is selected from among the plurality of filters based on the filter of the selected receiver. The summer is configured to combine the first filtered signal and the second filtered signal to provide a cancellation signal to reduce interference caused by the selected transmitter on the selected receiver. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an environment that includes a device according to various embodiments of the disclosure. 
         FIG. 2  is a block diagram of an illustrative hardware configuration for an apparatus employing a processing system according to various embodiments of the disclosure. 
         FIG. 3  is a portion of a communication system according to various embodiments of the disclosure. 
         FIG. 4  is a diagram of a communication system according to various embodiments of the disclosure. 
         FIGS. 5A-5B  are flow charts of a method according to various embodiments of the disclosure. 
         FIG. 6  is a block diagram of an active interference cancellation system. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments relate to methods and systems for cancelling interference produced by multiple radios (transceivers) operating on the same, adjacent, harmonic/sub-harmonic frequencies, or intermodulation product frequencies. In particular embodiments, an interference-cancellation system is adaptable for different radio combinations. For instance, for a co-existence issue caused by a first combination of radios, the transmitting radio (e.g., WiFi) may be selected for an input of an interference cancellation (IC) circuit and the receiving radio (e.g., Bluetooth) may be selected for the output of the IC circuit. For a co-existence issue caused by a second (different) combination of radios, the transmitting radio (e.g., WiFi) may be selected for the input of the IC circuit and the receiving radio (e.g., LTE band 7) may be selected for the output of the IC circuit. It should be noted that the terms cancellation (as in interference cancellation) and variants thereof may be synonymous with reduction, mitigation, and/or the like in that at least some interference is reduced. 
     In various embodiments, for a given co-existence issue, systems and methods include two identical filters (e.g., similar characteristics): a filter in a wireless coupling path (along which a signal transmitted by an aggressor radio interferes with a victim radio) and a filter in an IC path (along which the IC circuit is provided) to minimize delay (and/or gain) mismatch between the two paths. In various embodiments, the IC circuit includes a digitally-controlled analog least mean squares (LMS) adaptive filter or an analog-controlled analog LMS adaptive filter to match gain in the IC path with gain in the wireless coupling path. 
       FIG. 1  is a block diagram illustrating an environment  100  that includes a device  102 . The environment  100  may be representative of any system(s) or a portion thereof that may include at least one device  102  enabled to transmit and/or receive wireless signals to/from at least one wireless system  104 . The device  102  may, for example, include a mobile device or a device that while movable is primarily intended to remain stationary. The device  102  may also include stationary devices (e.g., desktop computer) enabled to transmit and/or receive wireless signals. Thus, as used herein, the terms “device” and “mobile device” may be used interchangeably as each term is intended to refer to any single device or any combinable group of devices that may transmit and/or receive wireless signals. 
     In various embodiments, the device  102  may include a mobile device such as a cellular phone, a smart phone, a personal digital assistant, a portable computing device, a navigation device, a tablet, and/or the like or any combination thereof. In other embodiments, the device  102  may take the form of a machine that is mobile or stationary. In yet other embodiments, the device  102  may take the form of one or more integrated circuits, circuit boards, and/or the like that may be operatively enabled for use in another device. 
     The device  102  may include at least one radio (also referred to as a transceiver). The terms “radio” or “transceiver” as used herein refers to any circuitry and/or the like that may be enabled to receive wireless signals and/or transmit wireless signals. In particular embodiments, two or more radios may be enabled to share a portion of circuitry and/or the like (e.g., a processing unit, memory, etc.). That is the terms “radio” or “transceiver” may be interpreted to include devices that have the capability to both transmit and receive signals, including devices having separate transmitters and receivers, devices having combined circuitry for transmitting and receiving signals, and/or the like. 
     In some embodiments, the device  102  may include a first radio enabled to receive and/or transmit wireless signals associated with at least a first network of a wireless system  104  and a second radio that is enabled to receive and/or transmit wireless signals associated with at least a second network of the wireless system  104  and/or at least one navigation system  106  (e.g., a satellite positioning system and/or the like). 
     The wireless system  104  may, for example, be representative of any wireless communication system or network that may be enabled to receive and/or transmit wireless signals. By way of example but not limitation, the wireless system  104  may include one or more of a wireless wide area network (WWAN), a wireless local area network (WLAN), a wireless personal area network (WPAN), a wireless metropolitan area network (WMAN), a Bluetooth communication system, WiFi communication system, Global System for Mobile communication (GSM) system, Evolution Data Only/Evolution Data Optimized (EVDO) communication system, Ultra Mobile Broadband (UMB) communication system, Long Term Evolution (LTE) communication system, Mobile Satellite Service—Ancillary Terrestrial Component (MSS-ATC) communication system, and/or the like. 
     The wireless system  104  may be enabled to communicate with and/or otherwise operatively access other devices and/or resources as represented simply by cloud  110 . For example, the cloud  110  may include one or more communication devices, systems, networks, or services, and/or one or more computing devices, systems, networks, or services, and/or the like or any combination thereof. 
     The term “network” and “system” may be used interchangeably herein. A WWAN may be a Code Division Multiple Access (CDMA) network, a Time Division Multiple Access (TDMA) network, a Frequency Division Multiple Access (FDMA) network, an Orthogonal Frequency Division Multiple Access (OFDMA) network, a Single-Carrier Frequency Division Multiple Access (SC-FDMA) network, and/or the like. A CDMA network may implement one or more radio access technologies (RATs) such as cdma2000, Wideband CDMA (W-CDMA), to name just a few radio technologies. Here, cdma2000 may include technologies implemented according to IS-95, IS-2000, and IS-S56 standards. A TDMA network may implement Global System for Mobile Communications (GSM), Digital Advanced Mobile Phone System (D-AMPS), or some other RAT. GSM and W-CDMA are described in documents from a consortium named “3rd Generation Partnership Project” (3GPP). Cdma2000 is described in documents from a consortium named “3rd Generation Partnership Project 2” (3GPP2). 3GPP and 3GPP2 documents are publicly available. A WLAN may include an IEEE 802.11x network, and a WPAN may include (but not limited to) a Bluetooth network, an IEEE 802.15x, for example. 
       FIG. 2  is a block diagram of an illustrative hardware configuration for an apparatus, such as the device  102 , employing a processing system  201  according to various embodiments of the disclosure, including (but not limited to) the embodiments of FIGS.  1  and  3 - 5 B. In this example, the processing system  201  may be implemented with a bus architecture represented generally by bus  202 . The bus  202  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  201  and the overall design constraints. The bus  202  links together various circuits including one or more processors, represented generally by the processor  204 , and computer-readable media, represented generally by the computer-readable medium  206 . The bus  202  may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. A bus interface  208  provides an interface between the bus  202  and a plurality of transceivers  210  (also referred to as radios). Each of the transceivers  210  allows for communicating with various other apparatus over a transmission medium. 
     A processor  204  is responsible for managing the bus  202  and general processing, including the execution of software stored on computer-readable storage medium  206 . The software, when executed by the processor  204 , causes the processing system  201  to perform the various functions described in the disclosure for any particular apparatus. The computer readable storage medium  206  may also be used for storing data that is manipulated by the processor  204  when executing software. 
     In various embodiments, the processing system  201  includes an interference cancellation (IC) circuit  220  and a controller  230 . The IC circuit  220  is configured to cancel interference produced by the transceivers  210  that are operating on the same, adjacent, or harmonic/sub-harmonic frequencies. The controller  230  may be as a microcontroller, a microprocessor, computer, state machine, or other programmable device. The controller  230  is coupled to the IC circuit  220 . The controller  230  executes one or more algorithms and/or include control logic (e.g., as stored on the computer-readable storage medium  206 ) for optimizing the reduction of interference by the IC circuit  220 . In particular, the controller  230  adjusts the settings of the IC circuit  220  to adjust the amplitude, phase, and/or delay of an input signal to generate an output. In some embodiments, the controller may be the processor  204 . 
       FIG. 3  illustrates a portion of an interference management system  300  that is at least a part of and/or implemented with the processing system  201  (e.g.,  FIG. 2 ). That is, the interference management system  300  may be implemented in the device  102  (e.g.,  FIGS. 1-2 ). 
     With reference to  FIGS. 1-3 , in various embodiments, the plurality of transceivers  210  may include n transceivers (e.g., two transceivers, three transceivers, etc.), such as, for example (but not limited to), a first transceiver  212 , a second transceiver  214 , a third transceiver  216 , to an n-th transceiver  218 . The first transceiver  212  may include a first transmitter  312  and a first receiver  314 . The second transceiver  214  may include a second transmitter  322  and a second receiver  324 . The third transceiver  216  may include a third transmitter  332  and a third receiver  334 . The n-th transceiver  218  may include an n-th transmitter  342  and an n-th receiver  344 . Depending on which transmitters are active (e.g., transmitting) and which receivers are active (e.g., receiving), any number of co-existence issues may occur. 
     Each of the transceivers  210  may operate according to various parameters, such as a respective frequency, radio frequency circuits with group delays, coupling channel gains to other transceivers, and/or the like. For instance, the first transceiver  212  may operate at a first frequency f1 with a first delay d1, the second transceiver  214  may operate at a second frequency f2 with a second delay d2, the third transceiver  216  may operate at a third frequency f3 with a third delay d3, and the n-th transceiver  218  may operate at an n-th frequency fn with an n-th delay d2. The first transceiver  212  may have a coupling channel gain h12 to the second transceiver  214 , a coupling channel gain h13 to the third transceiver  216 , and a coupling channel gain h1n to the n-th transceiver  218 , respectively. Other transceivers  210  may have different coupling channel gains to various transceivers  210 . 
     In various embodiments, the processing system  201  is configured to reduce interference produced among transceivers of the plurality of transceivers  210 , for example, operating on the same, adjacent, harmonic, or sub-harmonic frequencies. In particular embodiments, the processing system  201  is configured to be adaptable for different transceiver combinations. That is, the processing system  201  is configured to cancel interference based on the co-existence issue caused by the current combination of transceivers  210 . For instance, for a first co-existence issue (e.g., at time T1) caused by a first combination of transceivers  210 , such as the first transmitter  312  (e.g., WiFi transmitter) and the second receiver  324  (e.g., Bluetooth receiver), the processing system  201  (e.g., via the controller  230 ) may select from among the transmitters and the receivers, the first transmitter  312  for providing an input to the IC circuit  220  and the second receiver  324  for receiving an output of the IC circuit  220 . Accordingly, interference caused by an aggressor transceiver (e.g., the first transmitter  312 ) upon a victim transceiver (e.g., the second receiver  324 ) can be reduced. In this case, if the coupling channel gain from the aggressor transceiver to the victim transceiver is −10 dB (e.g., due to separation of two antennas), then the IC circuit  220  may need to match this gain for successful IC. For a second co-existence issue (e.g., at time T2) caused by a second (different) combination of transceivers, such as the first transmitter  312  (e.g., WiFi transmitter) and the third receiver  334  (e.g., LTE band 7), the processing system  201  (e.g., via the controller  230 ) may select from among the transmitters and the receivers, the first transmitter  312  for providing an input to the IC circuit  220  and the third receiver  334  for receiving an output of the IC circuit  220 . Accordingly, interference caused by an aggressor transceiver (e.g., the first transmitter  312 ) upon a victim transceiver (e.g., the third receiver  334 ) can be reduced. According to various embodiments, in such a case, if the coupling channel gain from the aggressor transceiver to the victim transceiver is −50 dB (e.g., due to separation two antennas and band pass filtering at the victim transceiver), then the IC circuit  220  may need to match this gain for successful IC. 
     In various embodiments, the system  300  is configured to select the transceivers (e.g., one or more transmitters and one or more receivers) associated with a co-existence issue. In particular embodiments, the controller  230  or the like selects the transceivers causing a co-existence issue for processing by the IC circuit  220 , for example, in response to detection of the co-existence issue between the at least two transceivers. For instance, in some embodiments, the transmitters  312 ,  322 ,  332 ,  342  may be coupled to an input multiplexer (MUX)  352  to receive corresponding signals  313 ,  323 ,  333 ,  343  from the transmitters  312 ,  322 ,  332 ,  342 . The input multiplexer  352  is coupled to the IC circuit  220  to allow the input multiplexer  352  to select (e.g., as controlled by the controller  230 ) one of the signals  313 ,  323 ,  333 ,  343  from one of the transmitters  312 ,  322 ,  332 ,  342  as input signal  356  to the IC circuit  220 . 
     The receivers  314 ,  324 ,  334 ,  344  may be coupled to an output multiplexer  354  to receive corresponding signals  315 ,  325 ,  335 ,  345  from the output multiplexer  354 . The output multiplexer  354  is coupled to the IC circuit  220  to allow the output multiplexer  354  to select (e.g., as controlled by the controller  230 ) one of the receivers  314 ,  324 ,  334 ,  344  to receive an output signal  358  from the IC circuit  220 . 
     For example, for a co-existence issue caused by a combination of transceivers, such as the first transmitter  312  (e.g., WiFi transmitter) and the third receiver  334  (e.g., LTE band 7), the controller  230  may select from among the transmitters, the first transmitter  312  for providing the input signal  356  to the IC circuit  220 , and the controller  230  may select from among the receivers, the third receiver  334  for receiving the output signal  358  from the IC circuit  220 . Likewise, in response to detecting a different co-existence issue caused by a different combination of the transceivers  210 , the controller  230  may select the transceivers causing the different co-existence issue. In some embodiments, the controller  230  may activate the IC circuit  220 , which may be deactivated or in a reduced power state, in response to detecting a co-existence issue. 
       FIG. 4  is a functional block diagram of a communication system  400  employed with the device  102  (e.g.,  FIGS. 1-2 ) and/or the processing system  201  and may implement the features and methods of such. For reference, the system  400  includes a coupling path  410  along which a signal transmitted by an aggressor radio interferes with a victim radio and an IC path  420  along which the IC circuit  220  is provided to generate a cancellation signal to reduce interference caused by the aggressor radio upon the victim radio. 
       FIG. 5A  illustrates a method B 500  of interference management, for example for reduction or cancellation of such interference, according to various embodiments of the disclosure. With reference to  FIGS. 1-5A , the method B 500  may be performed, for example, by the communication system  400  (e.g., the IC circuit  220 , the controller  230 , etc.). 
     In various embodiments, at block B 510 , the controller  230  is configured to detect a co-existence issue between at least two of the transceivers  210 . The controller  230 , for instance, may detect a co-existence issue when at least a transmitter (aggressor transmitter) and a receiver (victim receiver) of the at least two transceivers  210  are active (e.g., transmitting/receiving) at once. In particular embodiments, a co-existence issue may be detected when the transmitter and the receiver are candidates for co-existence issues (e.g., as provided in a pre-defined look-up table or database). For instance, a co-existence issue may be detected between a first transmitter  412  (which may correspond, for example, to one of the transmitters  312 ,  322 ,  332 ,  342 ) and a first receiver  424  (which may correspond, for example, one of the receivers  314 ,  324 ,  334 ,  344 ). 
     In some embodiments, the candidates may be provided in a look-up table or other database of known transceiver combinations that cause co-existence issues. Accordingly, when a combination of active transceivers is detected that appears in the table or database, a co-existence issue may be detected. In other embodiments, a sensor may be provided for sensing, measuring, or otherwise detecting interference, such as an intensity or magnitude (level) of the interference, on a transceiver (e.g., receiver) or a symptom of interference (e.g., de-sense level), such as a reduced receiving signal or the like (e.g., reduced receiving rate, increased noise, etc.) by the transceiver. In some embodiments, transmission information (e.g., by a transmitter) may be sensed, measured, or otherwise detected. Accordingly, when interference or other symptom of interference is detected a co-existence issue may be detected. In particular embodiments, the interference level (e.g., de-sense level) is based on (i) a frequency separation between a transmit channel of the transmitter and receive channel of the receiver and (ii) transit power of the transmitter. 
     In some embodiments, parameters of the detected co-existence issue may also be determined, for example, by the controller  230 . For instance, the controller  230  may determine the parameters, such as the coupling channel gains, the frequency (e.g., f1), delay (e.g., d1), and/or the like of the aggressor transmitter. For example, if the first transmitter  412  is a WiFi transmitter, the first frequency f1 may be about 2.4 GHz and the first delay may be (but is not limited to) about 15 ns. For example, if the second receiver  424  is a Bluetooth receiver, the first frequency f1 may be about 2.4 GHz and the second delay may be about 15 ns. If the co-existence issue is between the first transmitter and the second receiver  324 , the overall IC parameters are coupling channel gain −10 dB at 2.4 GHz and the overall delay is 30 ns. In particular embodiments, the controller  230  may correspond to a LMS coefficient controller and/or the LMS coefficient controller  460  may be provided to determine the parameters. 
     The first transmitter  412  is electrically coupled to a first antenna  401 . The first transmitter  412  transmits communication signals along a first transmit path  413  via the first antenna  401 . In some embodiments, a power amplifier (not shown) for amplifying signals transmitted by the first transmitter  412  may also be provided. 
     At block B 520 , the first transmitter  412 , which was determined to have a co-existence issue with the first receiver  424  (e.g., at block B 510 ), is coupled to the IC  220 . For instance, an input MUX  452  (which may correspond, for example, to the input MUX  352 ) may select the first transmitter  412  to provide a signal  411  transmitted by the first transmitter  412  as an input signal  456  (which may correspond, for example, to the input signal  356 ) to the IC  220 . 
     In some embodiments, the input signal  456  to the IC circuit  220  is coupled to the first transmit path  413  via a coupler  416  and the input MUX  452 . The coupler  416  obtains samples of signals (signal  411 ) transmitted by the first transmitter  412  and provides the samples to the input MUX  452 , which then provides the samples as the input signal  456  to the IC circuit  220 . Accordingly, the coupler  416  can obtain a sample or a representation of the interference of the aggressor signal transmitted by the first transmitter  412 , which produces, induces, generates, or otherwise causes the interference. In certain embodiments, the coupler  416  provides a direct connection to the first transmit path  413 . Alternatively, a capacitor, resistor, antenna, or other device could be used in place of or in addition to the coupler  416  to obtain samples of the signals transmitted by the first transmit path  413 . 
     At block B 530 , the first receiver  424 , which was determined to have a co-existence issue with the first transmitter  412  (e.g., at block B 510 ), is selected. The first receiver  424  is electronically coupled to a second antenna  403 . The first receiver  424  receives a signal d(t)+g(t)+n(t), where d(t) is the aggressor signal from the first transmitter  412 , g(t) is the signal of the wireless coupling path, and n(t) is noise, along a first receiver path  414  via the second antenna  403 . 
     Each of the plurality of receivers  314 ,  324 ,  334 ,  344  may include a corresponding filter for filtering a signal received by its respective receiver to provide a corresponding filtered signal. For instance, a MUX (not shown) may select the first receiver  424  (as determined to have a co-existence issue) to provide a signal  414  received by the first receiver  424  (e.g., via antenna  403 ) to a filter  404  corresponding to the first receiver  424 . The filter  404  may filter the signal  414  to provide a first filtered signal  417 . One or more of the filters  404  may be a band pass filter (BPF), duplexer, notch filter, and/or the like. 
     In other embodiments, the filter  404  is a tunable filter that is tuned based on the co-existence issue. For instance, for a first type of co-existence issue (e.g., WiFi transmitter with Bluetooth receiver), the filter  404  may be tuned to have a first set of characteristics (e.g., gain, delay, etc.) and a second set of characteristics for a second type of co-existence issue. 
     It should be noted that the co-existence combination between the transmitter  412  ( 312 ) and the receiver  424  ( 324 ) is merely exemplary and that the controller  230  is configured to select from among other combinations (e.g., the first transmitter  312  with the third receiver  334  and/or the n-th receiver  344 ; the second transmitter  322  and the first receiver  314 , the third receiver  334 , and/or the n-th receiver  344 ; the third transmitter  332  and the first receiver  314 , the second receiver  324 , and/or the n-th receiver  344 ; the n-th transmitter  342  and the first receiver  314 , the second receiver  324 , and/or the third receiver  334 ) based on co-existence issues between such combinations. 
     At block B 540 , in various embodiments, the IC circuit  220  is configured (e.g., by the LMS controller  460 ), for example, based on the parameters of the co-existence issue. For instance, this may be performed by measuring interference level at the receiver  424  or from pre-defined table. In some embodiments, if a significant amount of interference is detected, the controller (e.g., controller  230 ) determines the radio of interest (i.e., the radio involved with the co-existence issue) and switch the input and output MUXs to choose the signal of interest. The waveform-agnostic common IC circuit  220  is used for various set of aggressor and victim radios. Accordingly, the IC circuit  220  may begin updating LMS coefficient(s) to cancel the interference. In some embodiments, one or more pre-defined initial parameter values may also be used for the LMS coefficient(s) at the IC circuit  220  until the IC circuit  220  enters a steady state. Accordingly, at block B 550 , the IC circuit  220  may generate an output signal  458  (which may correspond, for example, to the output signal  358 ) based on the input signal  456  and the parameters of the co-existence issue. 
     The interference cancellation (IC) circuit  220  is configured to generate the output signal  458  to cancel (reduce) interference (e.g., in-band and/or nearby out-of-band interference) introduced onto the first receive path  414  by signals transmitted along the first transmit path  413  (by the first transmitter  412 ). In various embodiments, the IC circuit  220  is configured by the controller  230  based on the parameters (e.g., frequency, delay, etc.) of the detected co-existence issue. 
     The IC circuit  220  adjusts the amplitude, phase, and/or delay of the sampled signals to produce an interference compensation signal (e.g., output signal  458 ) that, when applied (e.g., via adder  426 ) to the first receive path  414  of the second receiver  424 , reduces, suppresses, or cancels the amplitude of in-band and/or nearby out-of-band interference and/or noise introduced onto the first receive path  414  by signals transmitted along the first transmit path  413 . In particular embodiments, the IC circuit  220  adjusts the amplitude, phase, and/or delay of the sampled signals based on settings received from another device, such as an LMS coefficient controller  460  (and/or the controller  230 ). 
     In some embodiments, the IC circuit  220  comprises a single-tap least-mean square (LMS) adaptive filter  450 . The LMS adaptive filter  450  may receive the input signal  456  and generate the output signal  458 . It should be noted that in other embodiments, an LMS filter having any number of taps (e.g., three taps) may be implemented. In some embodiments, the LMS adaptive filter  450  implements analog methods. Analog methods, for example, allow for wideband interference cancellation. In other embodiments, the LMS adaptive filter  450  implements digital methods. Digital methods, for example, may provide a good tradeoff between main lobe and side lobe cancellation. In some embodiments, an amplifier  451  may be provided to amplify a signal generated by the LMS adaptive filter  450  to generate the output signal  458 . 
     In some embodiments, a plurality of filters may be coupled to an output DEMUX  454  (which may correspond, for example, to the output DEMUX  354 ) to receive corresponding signals  415 ,  425 ,  435 ,  445  (which may correspond to signals  315 ,  325 ,  335 ,  345 , respectively) from the output DEMUX  454 . The output DEMUX  454  is coupled to the IC circuit  220  to allow the output DEMUX  454  to select (e.g., as controlled by the controller  230 ) a filter from among the plurality of filters, to receive the output signal  458  from the IC circuit  220 . Accordingly, at block B 560 , a filter  402  is selected based on parameters of the filter  404  associated with the first receiver  424 . The filter  402  receives the output signal  458  from the IC circuit  220  to provide a second filtered signal  418 . One or more of the filters  402  may be a band pass filter (BPF), duplexer, notch filter, and/or the like. 
     In some embodiments, the filter  402  is selected from among a plurality of filters. For instance, the plurality of filters may include a corresponding filter for each of the receiver filters. In other embodiments, a single (or more) filter  402  is configured to match characteristics of the filter  404 . For instance, the filter  402  may be a tunable filter that is tuned to match the characteristics, (e.g., gain, delay, etc.) of the filter  404 . For instance, if the filter  404  has a first characteristic (or set of characteristics), the filter  402  is tuned to have the first characteristic, and if the filter  404  has a second characteristic, the filter  402  is tuned to have the second characteristic. 
     Thus in various embodiments, for a given co-existence issue, the system  400  includes two identical filters: the filter  404  in the wireless coupling path  410  and the filter  402  in the IC path  420  to minimize delay (and/or gain) mismatch between the two paths  410 ,  420 . Because in some embodiments, the filter  402  may be the main source of the group delay in the IC path  420 , using an identical filter  404  in the coupling path  410  can minimize the delay difference between the two paths  410 ,  420 . In particular, the filter  402  in the IC path  420  can be selected or otherwise adjusted, for instance using the output DEMUX  454  to match the filter  404  associated with the receiving radio (in the wireless coupling path  410 ). For example, if the victim radio is a first victim radio associated with a first filter (e.g., BPF1), the output DEMUX  454  selects a similar filter (e.g., BPF1) in the IC path  420 , and if the victim radio is a second victim radio associated with a second filter (e.g., BPF2), the DEMUX  454  selects a similar filter (e.g., BPF2) in the IC path  420 . 
     At block B 570 , a cancellation signal  419  is generated based on the first filtered signal  417  and the second filtered signal  418  to reduce interference caused by the first transmitter  412  on the first receiver  424 . For instance, an adder  426  receives the first filtered signal  417  and the second filtered signal  418  to generate the cancellation signal  419 . 
     In some embodiments, the cancellation signal  419  may be provided to a low-noise amplifier (LNA)  427 . The LMS coefficient controller  460  receives a signal  429  from the LNA  427  to determine parameters (coefficients) for the IC circuit  220 . 
     In some embodiments, the LNA  427  may be coupled to a mixer  431 . An output of the mixer  431  may be coupled to an analog-to-digital converter (ADC)  433 . An output of the ADC  433  may be coupled to one or more digital filters  435 . An output of the digital filter  435  may be coupled to a digital signal processor (DSP)  437  that generates an output coupled to a software block (S/W)  439 . In some embodiments, the S/W  439  may include a timer to periodically switch between a first mode (a normal operation mode) and a second mode (an IC monitoring mode). An output of the S/W  439  may be coupled to digital-to-analog converter (DAC)  441 . An output of the DAC  441  may be coupled to the LMS coefficient controller  460 . Accordingly, for example, the LMS coefficient controller  460  provide configuration information to the IC circuit  220  (e.g., LMS adaptive filter  450 ), via the update path  462 , based on the signal  429  and the output of the DAC  441 . That is, the LMS coefficient controller  460  may control a signal along the update path  462  based on gain, delay, and/or frequency mismatch between the coupling path  410  and the IC path  420  to minimize error before the LNA  427 . In various embodiments, the configuration information (e.g., coefficients) from the LMS coefficient controller  460  may be used to configure the IC circuit  220  (e.g., LMS adaptive filter  450 ) to generate an updated output signal  458 , which then may be filtered by the filter  404  to provide an updated second filtered signal  418  (g(t)+n′(t), where n′(t) is noise along the IC path  420 ) to generate a new cancellation signal  419  (d(t)+n(t)−n′(t)). 
     In some embodiments, a co-existence issue may exist or be detected between more than two transceivers. Accordingly, multiple IC circuits  220  may be implemented for concurrent interference cancellation. 
     In some embodiments, the processing system  201  may selectively ignore or otherwise not manage a particular co-existence issue (e.g., via the IC circuit  220  and/or the controller  230 ) under certain circumstances. For example, the processing system  201  may selectively ignore or otherwise not manage the particular co-existence issue if the processing system  201  (e.g., the controller  230 ) determines that the particular co-existence issue is being managed by a different method and/or system. If the co-existence issue is managed by a baseband IC circuitry, the processing system  201  may not manage the issue with an analog IC circuitry. As another example, the processing system  201  may selectively ignore or otherwise not manage the particular co-existence issue if the processing system  201  (e.g., the controller  230 ) determines that the particular co-existence issue is below a specified threshold. For instance, the particular co-existence issue may be ignored if the issue causes light interference (e.g., a few decibels). That is, the co-existence issue may be ignored (or otherwise unmanaged) if an intensity of the interference is below a predetermined threshold. For example, if the interference is less than 10 dB above a sensitivity level of the receiver, the co-existence issue may be ignored. 
     The method B 500  described in  FIG. 5A  above may be performed by various hardware and/or software component(s) and/or module(s) corresponding to the means-plus-function blocks B 500 ′ illustrated in  FIG. 5B . In other words, blocks B 510  through B 570  illustrated in  FIG. 5A  correspond to means-plus-function blocks B 510 ′ through B 570 ′ illustrated in  FIG. 5B . 
     It is understood that the specific order or hierarchy of steps in the processes disclosed is an example of illustrative approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged while remaining within the scope of the present disclosure. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented. 
     Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the implementations disclosed herein may be implemented as electronic hardware, computer software embodied on a tangible medium, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software embodied on a tangible medium depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. 
     The various illustrative logical blocks, modules, and circuits described in connection with the implementations disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     The steps of a method or algorithm described in connection with the implementations disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An illustrative storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal. 
     In one or more illustrative implementations, the functions described may be implemented in hardware, software or firmware embodied on a tangible medium, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. In addition, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-Ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. 
     The previous description of the disclosed implementations is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these implementations will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the implementations shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.