# US 2013/0155913 A1 · Single channel full duplex wireless communication > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0155913 A1 - Document ID: US20130155913A1 - Status: Published application - Kind: A1 - Application number: 13/713,443 - Filed: 2012-12-13 - Published: 2013-06-20 - Earliest claimed: 2011-12-14 - Assignees: Redline Communications Inc. - Inventors: Octavian Sarca - Web page: https://patentgrep.com/patent/US20130155913A1 ## CPC - H04B 1/525: with means for reducing leakage of transmitter signal into the receiver - H04B 1/40: Circuits - H04L 5/14: Two-way operation using the same type of signal, i.e. duplex - H04L 5/1461: {Suppression of signals in the return path, i.e. bidirectional control circuits} - H04W 24/02: Arrangements for optimising operational condition - H04W 84/042: {Public Land Mobile systems, e.g. cellular systems} - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract A single channel full duplex wireless communication system includes a processor, a transmitter, a receiver, a secondary transmission path, a combining element, a primary transmission feedback path and a secondary transmission feedback path. The transmitter transmits a transmission signal via a transmission path. The receiver receives a received signal via a reception path. The transmitter and the receiver utilize one channel to transmit and receive signals. The transmission signal causes self-interference. The processor estimates a first transfer function and feeds the secondary transmission path with the transmission signal adjusted by the first transfer function to reduce the transmission signal leaked to the reception path. The combining element combines the transmission signal with the adjusted secondary transmission path signal to remove the self-interference. The primary transmission feedback path output is modified by a second transfer function. The secondary transmission feedback path output is modified by a third transfer function. ## Claims ### Claim 1 A single channel full duplex wireless communication system, comprising: a processor; a transmitter coupled to the processor, the transmitter transmitting a transmission signal via a transmission path; a receiver coupled to the processor, the receiver receiving a received signal via a reception path, wherein the transmitter and the receiver utilize one channel, at the same time, to transmit and receive said transmission and received signals, the transmission signal causing self-interference; a secondary transmission path coupled to the transmitter; and the processor estimating a first transfer function and feeding the secondary transmission path with the transmission signal adjusted by the first transfer function in such a way that the secondary transmission path signal reduces the transmission signal leaked to the reception path; a combining element coupled to the receiver, the combining element being configured to combine the transmission signal with the adjusted secondary transmission path signal, thereby removing at least a fraction of the self-interference; and a primary transmission feedback path and a secondary transmission feedback path, the primary transmission feedback path output being modified by a second transfer function and the secondary transmission feedback path output being modified by a third transfer function, such that combining of the modified primary transmission feedback path output and the modified secondary transmission feedback path output to the reception path output reduces the remaining fraction of the self-interference. ### Claim 2 (depends on 1) The system of claim 1, wherein the transmitter and the receiver utilize one antenna to transmit and receive signals, the antenna being coupled to both the transmitter and the receiver via a circulator-like device. ### Claim 3 (depends on 2) The circulator-like device of claim 2, further comprising an entrance port and a second port coupled to the antenna, the circulator-like device being configured to allow the transmission signal entering the circulator-like device through the second port to exit through the input of the receiver with minimal attenuation and with only a minor part of the signal energy exiting through the entrance port. ### Claim 4 (depends on 2) The circulator-like device of claim 2, further configured to offer isolation in the range of at least one of 20 dB through use of passive components or in the range of 50 dB through use of active noise cancellation techniques. ### Claim 5 (depends on 2) The system of claim 2, further comprising a transmission splitter coupled to both the transmission path and to a transmission feedback path, wherein the transmission splitter is configured to direct a portion of the transmission signal to the transmission feedback path and to direct the remainder of the transmission signal to an entrance port of the circulator-like device. ### Claim 6 (depends on 1) The system of claim 1, further comprising a first antenna and a second antenna, wherein the first antenna is a transmission antenna and the second antenna is a receiver antenna, the antennas being coupled to the processor. ### Claim 7 (depends on 1) The system of claim 1, wherein the combining element is a combiner. ### Claim 8 (depends on 1) The system of claim 1, comprising multiple transmission paths and multiple reception paths. ### Claim 9 A method of improving signal-to-interference ratio in a single channel full duplex wireless communication system, comprising: transmitting a transmission signal via a transmission path; receiving a received signal via a reception path, the transmission path and the reception path utilizing one channel, at the same time, to transmit and receive transmission and received signals, the transmission signal causing self-interference; estimating, by a processor, a first transfer function; feeding, by the processor, a secondary transmission path with the transmission signal adjusted by the first transfer function in such a way that the secondary transmission path signal reduces the transmission signal leaked to the reception path, thereby removing at least a fraction of the self-interference, the secondary transmission path being coupled to the transmitter; combining, by a combining element coupled to the receiver, the transmission signal with the adjusted secondary transmission path signal; estimating, by the processor, a second transfer function and a third transfer function; modifying, by the processor, a primary transmission feedback path output signal with the second transfer function and a secondary transmission feedback path output signal with the third transfer function; and adding, by the processor, of the modified primary transmission feedback path output and the modified secondary transmission feedback path output to the reception path output, thereby canceling the remaining fraction of the self-interference. ### Claim 10 (depends on 9) The method of claim 9, wherein the third signal is further configured to cancel an amount of self-interference in the range of 60 dB. ### Claim 11 (depends on 9) The method of claim 9, wherein the transmitter and the receiver utilize one antenna to transmit and receive signals, the antenna being coupled to both the transmitter and the receiver via a circulator-like device. ### Claim 12 (depends on 9) The method of claim 9, further comprising an entrance port and a second port coupled to the antenna, the circulator-like device being configured to allow the transmission signal entering the circulator-like device through the second port to exit through the input of the receiver with minimal attenuation and with only a minor part of the signal energy exiting through the entrance port. ### Claim 13 A single channel full duplex wireless communication system, comprising: a processor; a transmitter coupled to the processor, the transmitter transmitting a transmission signal via a transmission path; wherein a portion of the transmission signal is leaked; a receiver coupled to the processor, the receiver receiving a received signal, the received signal comprising leakage from the transmission signal, the receiver including at least one combining element and at least one reception path, wherein the at least one combining element is coupled to an input of the receiver and wherein the at least one reception path is coupled to an output of the receiver, wherein the receiver produces an output signal, the output signal including self-interference caused by the leakage from the transmission signal; a secondary transmission path coupled to the transmitter and to the combining element; and the processor estimating a first transfer function and feeding the secondary transmission path with at least a portion of the transmission signal adjusted by the first transfer function to produce a first intermediate signal at an output of the secondary transmission path, wherein a first cancellation signal is obtained based upon the first intermediate signal, the first cancellation signal being subsequently combined with the received signal in the at least one combining element so as to reduce the self-interference in the output signal from the receiver; a second cancellation signal being generated by modifying a second intermediate signal using a second transfer function, the second transfer function being estimated by the processor, the second intermediate signal being obtained based on at least one of the transmission signal and the first intermediate signal, the second cancellation signal being subsequently combined with the output signal from the receiver within the processor, thereby further reducing the self-interference in the output signal from the receiver. ### Claim 14 (depends on 13) The system of claim 13, further comprising: a transmission feedback path coupled to the transmission path; a third cancellation signal, the third cancellation signal being generated from the transmission signal by directing a portion of the transmission signal through the transmission feedback path and subsequently modifying the output of the transmission feedback path using a third transfer function, the processor estimating the third transfer function; the third cancellation signal subsequently combined with the output signal from the receiver within the processor, thereby further reducing the self-interference in the receiver output signal. ### Claim 15 (depends on 13) The system of claim 13, wherein the first cancellation signal is obtained by splitting the first intermediate signal into a first and a second portion; and wherein the first portion becomes the first cancellation signal; or the first cancellation signal is obtained directly from the first intermediate signal. ### Claim 16 (depends on 15) The system of claim 15, wherein the second intermediate signal is generated by passing the second portion through a secondary transmission feedback path, the secondary transmission feedback path being coupled to the secondary transmission path, or is generated by splitting off a portion of the transmission signal. ### Claim 17 (depends on 13) The system of claim 13, wherein the transmitter and the receiver are coupled to one antenna to transmit and receive signals, the antenna being coupled to both the transmitter and the receiver via a circulator-like device. ### Claim 18 (depends on 17) The system of claim 17, being further configured to offer isolation through use of one of passive components and active noise cancellation techniques. ### Claim 19 (depends on 13) The system of claim 13, further comprising a first antenna and a second antenna, wherein the first antenna is a transmission antenna, the transmission antenna being coupled to the transmission path and wherein the second antenna is a receiver antenna, the receiver antenna being coupled to the receiver. ### Claim 20 (depends on 14) The system of claim 14, wherein the transmission path is coupled to the transmission feedback path using a splitter or wherein the second and third cancellation signals are combined with the receiver output signal within the processor by adding the second and third cancellation signals to the receiver output signal. ### Claim 21 (depends on 13) The system of claim 13, wherein the receiver comprises a plurality of stages, each stage including a reception path, wherein the output of the reception path is connected to a stage output of that stage, and wherein at least some of the stages include a combining element coupled to a stage input, an output of the combining element being coupled to the input of the reception path, and wherein the first cancellation signal is generated by: splitting the first intermediate signal into a plurality of portions; directing at least some of the plurality of the portions to the at least some of the stages including the combining element; and combining at least some of the plurality of the portions with the input signal to the stage within the combining element. ### Claim 22 A method of reducing self-interference caused by one or more transmission signals in a single channel full duplex wireless communication apparatus, comprising the steps of: transmitting one or more transmission signals using a transmitter, the transmitting occurring via one or more transmission paths coupled to the transmitter, wherein one or more portions of the one or more transmission signals are leaked; receiving one or more received signals using a receiver, the one or more received signals including leakage from the one or more transmission signals, the receiver comprising one or more combining elements and one or more reception paths, wherein at least one combining element is coupled to an input of the receiver, wherein the receiver produces one or more output signals, the one or more output signals including self-interference, the self-interference being caused by the leakage from the one or more transmission signals; generating one or more first cancellation signals; the generating of one or more first cancellation signals further including: estimating, by a processor, a first transfer function; feeding, by the processor, one or more secondary transmission paths with one or more portions of the one or more transmission signals adjusted by the first transfer function to produce one or more first intermediate signals at output(s) of the one or more secondary transmission paths, each one of the one or more secondary transmission paths being coupled to the transmitter and to the one or more combining elements of the receiver; obtaining the one or more first cancellation signals from the one or more first intermediate signals; combining, using the one or more combining elements within the receiver, the one or more received signals with the one or more first cancellation signals in the one or more combining elements of the receiver, thereby reducing the self-interference in the one or more output signals; generating one or more second cancellation signals; the generating of one or more second cancellation signals further including: estimating a second transfer function, the second transfer function being estimated by a processor; generating one or more second intermediate signals, the second intermediate signals being generated by obtaining portions of the one or more transmission signals; using one or more secondary transmission feedback path output signals, wherein inputs to the one or more secondary transmission feedback paths are coupled to the outputs of the one or more secondary transmission paths; and modifying the one or more second intermediate signals with the second transfer function to obtain the one or more second cancellation signals; and combining, in the processor, the one or more second cancellation signals with the one or more output signals from the receiver, thereby further reducing the self-interference in the one or more output signals. ### Claim 23 (depends on 22) The method of claim 22, further comprising generating one or more third cancellation signals, the generating of the one or more third cancellation signals further comprising: estimating a third transfer function; the third transfer function being estimated by the processor; modifying the one or more transmission feedback path output signals with the third transfer function; wherein inputs to the one or more transmission feedback paths are coupled to the outputs of the one or more transmission paths; and adding the one or more third cancellation signals to the one or more second cancellations signals and the one or more output signals from the receiver, thereby further reducing the self-interference caused by the leakage from the one or more transmission signals. ### Claim 24 (depends on 22) The apparatus of claim 22, including only one transmission path and only one reception path, the transmitter and the receiver utilizing only one antenna to transmit and receive signals, the antenna being coupled to both the transmitter and the receiver via a circulator-like device. ### Claim 25 (depends on 23) The method of claim 23, wherein the inputs to the one or more transmission feedback paths are coupled to the outputs of the one or more transmission paths by one or more transmission splitters, and the one or more transmission splitters receive the one or more transmission signals from the one or more transmission paths as inputs, and direct portions of the one or more transmission signals to the inputs of one or more transmission feedback paths. ### Claim 26 (depends on 22) The method of claim 22, wherein the transmitter is coupled to one or more transmit antennas and the receiver is coupled to one or more receive antennas, and the first and second transfer functions are matrices of transfer functions. ### Claim 27 (depends on 23) The method of claim 23, wherein the transmitter is coupled to one or more transmit antennas, and wherein the receiver is coupled to one or more receive antennas, and the first, second and third transfer functions are matrices of transfer functions. ### Claim 28 (depends on 24) The circulator-like device of claim 24, further configured to offer isolation through use of at least one of passive components and active noise cancellation techniques. ### Claim 29 (depends on 22) The method of claim 22, wherein the second intermediate signals are generated by obtaining one or more secondary transmission feedback path output signals, wherein the outputs of the one or more secondary transmission paths are coupled to by one or more secondary transmission splitters the inputs of the one or more secondary transmission feedback paths and at least some of the one or more combining elements of the receiver, wherein the one or more first cancellation signals are obtained from the one or more first intermediate signals by splitting the output signals from the one or more secondary transmission paths into a first set of one or more portions and a second set of one or more portions, the splitting being performed by the secondary transmission splitters, the first set of one or more portions becoming the first cancellation signals; directing the second set of one or more portions to the inputs of the one or more secondary transmission feedback paths. ### Claim 30 (depends on 22) The method of claim 22, wherein at least one of the one or more reception paths includes a plurality of stages, wherein the inputs to at least some of the stages are coupled to combining elements, and for each stage input coupled to a combining element, combining the input signal to the stage with a corresponding first cancellation signal in the combining element, thereby reducing the self-interference in the receiver output signal caused by the leakage from the one or more transmission signals.