664 results about "Self interference" patented technology

Two-way (full-duplex) wireless communications. Various embodiments measure interference channels and provide for interference cancellation in both analog and digital domains to mitigate self-interference. The system supports multiple clients wherein new clients can join the network asynchronously, and also supports Multiple-Input Multiple-Output (MIMO) antennas.

A receiver circuit suppresses effects of “benign” impairment from the calculation of received signal quality estimates, such that the estimate depends primarily on the effects of non-benign impairment. For example, a received signal may be subject to same-cell and other-cell interference plus noise, which is generally modeled using a Gaussian distribution, and also may be due to certain forms of self-interference, such as quadrature phase interference arising from imperfect derotation of the pilot samples used to generate channel estimates for the received signal. Such interference generally takes on a distribution defined by the pilot signal modulation, e.g., a binomial distribution for binary phase shift keying modulation. Interference arising from such sources is relatively “benign” as compared to Gaussian interference and thus should be suppressed or otherwise discounted in signal quality calculations. Suppression may be based on subtracting benign impairment correlation estimates from total impairment correlation estimates, or on filtering the benign impairment in channel estimation.

A wireless communication device includes, in part, an analog interference cancellation circuit and a controller. The analog cancellation circuit includes a multitude of delay paths each including a delay element and a variable attenuator. The controller dynamically varies the attenuation level of each of the variable attenuators in accordance with the frequency response characteristic of that attenuator to remove a portion of a self-interference signal present in a signal received by the device. The device measures the frequency response characteristic of the communication channel, used in determining the attenuation levels, via one or more preamble symbols. A second portion of the self-interference signal is removed by the device using a multitude of samples of a transmitted signal and a multitude of samples of a signal to be transmitted.

The present invention relates to confocal self-interference microscopy. The confocal self-interference microscopy further includes a first polarizer for polarizing reflected or fluorescent light from a specimen, a first birefringence wave plate for separating the light from the first polarizer into two beams along a polarizing direction, a second polarizer for polarizing the two beams from the first birefringence wave plate, a second birefringence wave plate for separating the two beams from the second polarizer into four beams along the polarizing direction, and a third polarizer for polarizing the four beams from the second birefringence wave plate, in the existing confocal microscopy. Optic-axes of the first and second birefringence wave plates exist on the same plane, optic-axes of the first and second birefringence wave plates are inclined from an optical axis of the entire optical system at a predetermined angle, and self-interference spatial periods of the first and second birefringence wave plates are different from each other.

A circuit that cancels a self-interference signal includes, in part, a pair of signal paths that are substantially in phase, each of which paths includes a passive coupler, a delay element and a variable attenuator. The circuit further includes, in part, a first group of P signal paths each of which is substantially in phase with the pair of paths, and a second group of M signal paths each of which is substantially out-of-phase relative to the pair of signal paths. Each of the P and M signal paths includes a delay element and a variable attenuator. Furthermore, (P−1) signal paths of the first group of P signal paths, and (M−1) signal paths of the second group of M signal paths include a passive coupler. Optionally, each of the M signal paths is optionally 180° out-of-phase relative to the pair of signal paths.

A method for full duplex communication includes creating a canceling self interference signal using active noise cancelation in RF circuits and transmission lines with a plurality of receive antennas being used and a signal received by the antennas are destructively combined in the transmission lines and passive RF components, and attaining full-duplex simultaneous in time and overlapping in space wireless transmission and reception on same frequency band responsive to the step of creating a canceling self interference signal.

A method for reducing self-interference between at least four data symbols that are modulated via a non-orthogonal matrix modulation and transmitted from at least four transmit antennas to at least one receive antenna comprises mapping the at least four data symbols onto the at least four transmit antennas and two orthogonal transmission resources via the non-orthogonal matrix modulation, multiplying data symbols mapped to one of the at least four transmit antennas with a factor γ, wherein γ is determined at least in dependence on the transmission channel characteristics from the at least four transmit antennas to the at least one receive antenna to reduce a self-interference between the at least four data symbols, and transmitting the mapped data symbols and the mapped and multiplied data symbols from the at least four transmit antennas to at least one receive antenna in the two orthogonal transmission resources.

In order to satisfy the conflicting requirements for spectrum sensing and QoS of data transmission, it is highly desirable for a cognitive radio system, e.g. IEEE 802.22 WRAN, to perform spectrum sensing and data transmission simultaneously. Embodiments of the invention address critical issues of self-interference generated from a transmission unit to the co-located sensing unit when the simultaneous sensing and data transmission technique is applied. A number of interference mitigation techniques are described and analyses are given.

A circuit that cancels a self-interference signal includes, in part, a pair of signal paths that are substantially in phase, each of which paths includes a passive coupler, a delay element and a variable attenuator. The circuit further includes, in part, a first group of P signal paths each of which is substantially in phase with the pair of paths, a second group of M signal paths each of which is substantially out-of-phase relative to the pair of signal paths, and at least a pair of feedback paths. Each of the P and M signal paths, as well as the feedback paths includes a delay element and a variable attenuator. Optionally, each of the M signal paths is optionally 180° out-of-phase relative to the pair of signal paths.

A MIMO wireless communication device includes, in part, a first transmit path adapted to transmit a first transmit signal from a first antenna, a second transmit path adapted to transmit a second transmit signal from a second antenna, a first receive path adapted to receive a first receive signal, an interference cancellation circuit and a controller. The cancellation circuit includes a cascaded filter structure each filter including a multitude of filter taps each including a variable element. The controller dynamically varies a value applied to each of the plurality of variable elements in accordance with frequency response characteristics of the variable element to remove a portion of a self-interference and / or cross-talk interference signal present in a signal received by the device. The device measures the frequency response characteristic of a multitude of communication channels, used in determining the values, via one or more preanible symbols that are jointly transmitted from the first transmit antenna and the second transmit antenna. A second portion of the interference signal is removed by a digital cancellation circuit using a multitude of samples of a transmitted signal.

A wireless communication device includes, in part, at least one antenna for receiving or transmitting a signal, and a cancelation circuit adapted to cancel or reduce the self-interference signal. The cancelation circuit includes, in part, a control block, N delay and attenuation paths, a combiner, and a subtractor. Each path includes a delay element and a variable attenuator whose attenuation level varies in response to a control signal generated by the control block. Each path receives a sample of the transmit signal and generates a delayed and attenuated (weighted) version of the sample signal. The combiner combines the N delayed and weighted versions of the sample signal to construct a signal representative of the self-interference signal. The subtractor subtracts the constructed signal from the received signal thereby the cancel or reduce the self-interference signal therefrom.

Full duplex radio wireless systems and methods and especially transceivers for full duplex radio wireless systems with reduction of self-interference are described. MIMO (=multiple input multiple output several antennas for output and input) is used within one device with multiple antennas to remove self-interference in a proactive way. For example, a transceiver is described having self-interference suppression, comprising, within one transceiver device: two or more transmitters comprising one or more signal generators for transmitting transmit signals having transmit center frequencies in a selected first subchannel; and one or more receivers having receiver inputs for simultaneously receiving a desired receive signal in a second subchannel and an undesired accumulated interference signal due to said transmitted signals; and at least one of said transmitters also comprising a precompensation circuit that modifies the transmit signals such that said accumulated interference signal at the receiver(s) inputs is reduced.

Provided is a self-interference cancellation method and apparatus that may remove self-interference occurring when a transmission signal of a transmit antenna is received, directly or via a reflector, by a receive antenna in a relay using the same frequency band in an orthogonal frequency division multiplexing (OFDM)-based radio communication system.

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.

A linear turbo-equalizer for use in a CDMA receiver equalizes a despread received signal (rather than the spread received signal) to suppress self-interference resulting from coupling between transmitted symbols. In an example implementation, a linear equalizer based on a generalized-Rake (G-Rake) receiver design uses decoder feedback in forming Rake combining weights as well as in forming a self-interference estimate removed from the equalizer signal provided to the decoder. Preferably, turbo de-coding is also performed. In that case, each turbo-decoder component preferably executes one pass before feeding back information to the equalizer. This ensures that the turbo-decoder does not prematurely lock onto an incorrect code word before feeding back extrinsic information to the equalizer.

A method for full duplex communication that includes creating a canceling self interference signal using a passive noise cancellation, and attaining full-duplex simultaneous in time and overlapping in space wireless transmission and reception on same frequency band responsive to the step of creating a canceling self interference signal.

Methods, apparatuses, and systems are presented for providing self-interference cancellation in two-way relayed electromagnetic communication between a first and a second device through a relay station, involving retrofitting existing equipment comprising a transmitter system and a receiver system at the first device by adding a canceler module, providing a version of a modulated near signal as a first non-baseband interface signal from the transmitter system to the canceler module, providing a version of a composite signal as a second non-baseband interface signal from the receiver system to the canceler module, generating a cancellation signal at the canceler module corresponding to a relayed version of the modulated near signal, using the first and the second non-baseband interface signals, applying the cancellation signal at the canceler module to a version of the second non-baseband interface signal, to produce a cancellation-processed signal as a third non-baseband interface signal provided to the receiver system.

The invention discloses a simultaneous common-frequency full duplex self-interference offset method in a multi-path environment. The method comprises the steps that in the transmission end, a digital signal to be transmitted is sent to a signal pre-correction module and a digital interference offset module, and a radio frequency signal to be transmitted is sent to a radio frequency interference reconstruction unit. The signal outputted by the signal pre-correction module passes through a DAC (digital-to-analog converter) and a transmission radio frequency channel to form a pre-corrected radio frequency signal. In the receiving end, the outputted self-interference signal subtracts the pre-corrected radio frequency signal and the radio frequency signal processed by the radio frequency interference reconstruction unit, the radio frequency self-interference offset is finished, and the offset signal, the pre-corrected radio frequency signal and the converted digital signal are sent to the digital interference offset module to finish the digital interference offset, together with the digital signal to be transmitted and the pre-corrected digital signal. The simultaneous common-frequency full duplex self-interference offset method under the multi-path environment is applicable to a simultaneous common-frequency system, the utilization rate of spectrum is doubled, the radio frequency self-interference offset performance is improved, the communication quality of the system is improved, and the working stability of communication equipment in a simultaneous common-frequency multi-path environment is improved.

A full-duplex transceiver is provided with componentry and methods for cancellation of nonlinear self-interference signals. The transceiver is capable of receiving an incoming radio-frequency signal that includes both a desired radio-frequency signal component and a self-interference component caused by the transceiver's own radio-frequency transmission. The transceiver demodulates the incoming radio-frequency signal to generate a first demodulated signal. The transceiver combines an analog corrective signal with the first demodulated signal to generate a second demodulated signal with reduced self-interference. The transceiver processes the first and second demodulated signals to determine a desired incoming baseband signal and to determine nonlinear components of the self-interference signal, such as nonlinearities introduced by the transceiver's power amplifier.

A self-interference signal cancellation circuit includes a transmitter for transmitting a transmit signal, a plurality of signal paths, a controller, and a receiver for receiving a signal. Each signal path includes a delay element and a variable attenuator having attenuation levels set by the controller. A combiner generates an output signal by combining outputs of the signal paths. The circuit computes a matrix based on first and second output signals associated with first and second attenuation levels. The controller concurrently varies the attenuation level of each signal path so that a product of the matrix and the attenuation levels of the signal paths is substantially equal to the received signal. The circuit may iteratively compute the matrix using different transmit signal frequencies or with an FFT. The controller iteratively varies the attenuation level of the attenuators until a sum of the product and the received signal satisfies a predefined condition.

A method for full duplex communication includes creating a canceling self interference signal using active noise cancelation in the air by using a plurality of transmit antennas and feeding the plurality of antennas with an RF signal in so that part of said RF signal is destructively combined at a receive antenna, and attaining full-duplex simultaneous in time and overlapping in space wireless transmission and reception on same frequency band responsive to the step of creating a canceling self interference signal.

The embodiment of the invention provides a method, device and system for processing interference signals for eliminating the interference signals in a full-duplex multi-antenna system. The method comprises the following steps: receiving wireless signals, wherein the wireless signals comprise self-interference signals of a sending antenna, and the self-interference signals comprise a first self-interference signal and a second self-interference signal; conducting primary interference offset processing on the received wireless signals by using a first reference signal to eliminate the first self-interference signal; conducting secondary interference offset processing on signals subjected to the primary interference offset processing by using a second reference signal to eliminate the second self-interference signal.

Methods, apparatuses, and systems are presented for providing self-interference cancellation in two-way relayed electromagnetic communication between a first and a second device through a relay station, involving retrofitting existing equipment comprising a transmitter system and a receiver system at the first device by adding a canceler module, providing a version of a modulated near signal as a first non-baseband interface signal from the transmitter system to the canceler module, providing a version of a composite signal as a second non-baseband interface signal from the receiver system to the canceler module, generating a cancellation signal at the canceler module corresponding to a relayed version of the modulated near signal, using the first and the second non-baseband interface signals, applying the cancellation signal at the canceler module to a version of the second non-baseband interface signal, to produce a cancellation-processed signal as a third non-baseband interface signal provided to the receiver system.

The invention discloses a same-time same-frequency full duplex multi-tap radio frequency self-interference offset system and method. A wireless unit receiving end outputs self-interference signals, self-interference offset is not conducted at first, after being processed by a radio frequency receiving channel and an analog-digital converter, the self-interference signals are sent to a pattern recognition module to generate an adjustment value, multiple taps are controlled to interfere in a reconstruction filter to reconstruct sending end radio frequency signals in a radio frequency mode, radio frequency self-interference offset is conducted on output reconstruction signals through a summator, signals after the radio frequency self-interference offset are sent to an adjustment algorithm module again through the radio frequency receiving channel and the analog-digital converter to obtain digital signals which are sent to the adjustment algorithm module, an adjusting value needed for adjusting the time delay zero is obtained, radio frequency interference reconstruction is further controlled, controlling over the radio frequency interference reconstruction is carried out repeatedly according to the method, and self-interference offset is achieved. According to the same-time same-frequency full duplex multi-tap radio frequency self-interference offset system and method, joint control of the pattern recognition module and the adjustment algorithm module is used, same-time same-frequency-radio self-interference can be removed effectively, the frequency spectrum utilization rate is improved, the radio frequency self-interference offset performance is improved, and the working stability of communication equipment is guaranteed.

Disclosed herein are an analog compensation circuit and a method for tuning an analog compensator in full-duplex transmission systems. An embodiment analog compensation circuit includes a secondary receiver configured to receive and convert a sampled self-interference signal to a baseband self-interference signal. A tuner is coupled to the secondary receiver and configured to receive a baseband transmit signal and the baseband self-interference signal, and to compute complex gains according to the baseband transmit signal and the baseband self-interference signal. An analog compensator is coupled to the tuner and has multiple branches. The analog compensator is configured to receive the complex gains and use them to adjust respective attenuators and phase shifters of the branches. The analog compensator is further configured to process a sample of a transmit signal using the branches, the transmit signal being up-converted from a new baseband transmit signal.

Full duplex radio wireless systems and methods and especially transceivers for full duplex radio wireless systems with reduction of self-interference are described. MIMO (=multiple input multiple output several antennas for output and input) is used within one device with multiple antennas to remove self-interference in a proactive way. For example, a transceiver is described having self-interference suppression, comprising, within one transceiver device: two or more transmitters comprising one or more signal generators for transmitting transmit signals having transmit center frequencies in a selected first subchannel; and one or more receivers having receiver inputs for simultaneously receiving a desired receive signal in a second subchannel and an undesired accumulated interference signal due to said transmitted signals; and at least one of said transmitters also comprising a precompensation circuit that modifies the transmit signals such that said accumulated interference signal at the receiver(s) inputs is reduced.

Self-interference cancellation is provided in two-way relayed electromagnetic communication between a first device and a second device through a relay station wherein a representation of a relayed composite signal above baseband and a representation of a locally modulated interface signal above baseband interact to effect the self-interference cancellation. Specifically, the composite signal, which contains a relayed version of the locally modulated (near) signal from the first device and a relayed version of a modulated far signal from the second device, is received at the first device from the relay station. The composite signal is then provided in a representation as a first interface signal at a first frequency at or above baseband to a canceler module of the first device and a representation of the modulated near signal at a second frequency above baseband is provided as a second interface signal to the canceler module. Part of the relayed version of the modulated near signal is canceled from the representation of the composite signal using the representation of the modulated near signal as provided to the canceler module to produce a third interface signal as output at a third frequency at or above baseband. The first and second frequencies may or may not be the same.

The invention discloses a full-duplex transceiver in a flat fading environment and a method for canceling self-interference. The method includes dividing received signals by a coupler to obtain a channel I of signals and a channel Q of signals at a receiving end; respectively transmitting the channel I of signals and the channel Q of signals into a channel I receiving channel and a channel Q receiving channels which are structurally symmetrical with each other; canceling the self-interference in a simulated manner in the receiving channels by the aid of multipliers, adders and a radiofrequency interference reconstruction module; digitally canceling the self-interference at the rear end via a digital cancellation unit; transmitting delay estimation parameters and channel estimation parameters to a delay module, the radiofrequency interference reconstruction module and the digital cancellation unit; circularly canceling the self-interference until the optimal cancellation effect is realized. Phase difference between the channel I of signals and the channel Q of signals is 90 degrees. The delay estimation parameters and the channel estimation parameters are generated by a channel / delay estimation unit. The full-duplex transceiver and the method have the advantages that the complexity of the structure of the transceiver can be effectively decreased by the aid of self-mixing and zero-intermediate-frequency technologies, the cost can be saved, and the size of the full-duplex transceiver can be reduced; requirements of self-interference signals on the precision of delay devices can be greatly reduced, and the devices can be selected conveniently and can be implemented easily; the receiving channels are independent from each other, are structurally symmetrical with each other and can be integrated easily.

Embodiments are provided for cancelling self-interference in a full-duplex communications system. The cancellation includes using a digital cancellation stage in additional to analog cancellation. In an embodiment, a method by a full-duplex communications device includes sampling a received signal, wherein the sampling provides a received digital signal corresponding to the received signal. The method further includes sampling a transmitted signal, wherein the sampling provides a transmitted digital signal corresponding to the transmitted signal. A channel distortion introducing self-interference in the received signal is then estimated according to the transmitted digital signal and the received digital signal. The method further includes estimating the self-interference in the received digital signal according to the estimated channel distortion.

A method for increasing cellular system capacity includes receiving a signal in a time slot and a frequency band and transmitting a signal in the same time slot and the same frequency band. An adaptive self-interference canceller is used to reduce the radio frequency self-interference created by receiving and transmitting signals in the same time slot and the same frequency band. The self-interference can be further reduced by using: (1) a circulator connected between an antenna, a receiver, and a transmitter; (2) separate antennas for receiving and transmitting signals can be used; and / or (3) an adaptive antenna.