Wireless communication receivers are often subject to interference that degrades reception performance. Various techniques for interference cancellation are known in the art.
For example, U.S. Pat. Nos. 5,596,439 and 6,011,952, whose disclosures are incorporated herein by reference, describe techniques in which a source transmitted signal is cancelled at a receiver associated with the transmitter, so that the desired received signal can be extracted from a composite received signal, the composite received signal consisting of the source signal relayed from the relay station along with the desired received signal from the other user in the pair, plus additive noise.
U.S. Pat. No. 6,725,017, whose disclosure is incorporated herein by reference, describes multi-channel self-interference cancellation in relayed electromagnetic communication between a first device and one or more other devices on one or more shared frequency channels. Specifically, near signals are generated at the first device and transmitted to a relay station. A composite signal is received at the first device from the relay station containing relayed versions of the near signals and relayed versions of remote signals transmitted from the one or more other devices, the composite signal having frequency channels including the one or more shared frequency channels, each shared frequency channel occupied by at least one of the relayed near signals and one of the relayed remote signals. One or more cancellation signals are selectively generated, each having a frequency band corresponding to one of the shared frequency channels. The cancellation signals are combined with the composite signal to produce a desired signal representing the relayed remote signals.
U.S. Pat. No. 6,859,641, whose disclosure is incorporated herein by reference, describes an adaptive interference canceller for canceling an interfering signal corresponding to a delayed, frequency translated, amplitude and phase offset version of a transmitted signal contained in a composite received signal relayed through a relay system such as a satellite transponder. The canceller digitally down-converts the received signal and a local replica of the transmitted signal from IF to baseband, applies a variable delay and frequency compensation to the replica as a coarse delay and frequency correction, and tracks fine delay, amplitude and phase differences using an adaptive finite impulse response filter to generate a cancellation signal corresponding to the delayed and frequency shifted version. A minimum output power process produces an error signal that drives the variable delay and adaptive filter to minimize the power in the signal of interest to maximize cancellation of the interfering signal.
U.S. Pat. No. 6,907,093, whose disclosure is incorporated herein by reference, describes self-interference cancellation 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 canceller 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 canceller 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 canceller module to produce a third interface signal as output at a third frequency at or above baseband.
U.S. Pat. No. 6,996,164, whose disclosure is incorporated herein by reference, describes self-interference cancellation in two-way relayed communications, by creating models of up-converter and down-converter imperfections and then compensating for those imperfections before self interference cancellation processing. The model includes compensation for phase offset, for amplitude imbalance and for leakage in the mixers.
U.S. Pat. No. 7,228,104, whose disclosure is incorporated herein by reference, describes an adaptive interference canceller for canceling an interfering signal corresponding to a delayed, frequency translated, amplitude and phase offset version of a transmitted signal contained in a composite received signal relayed through a relay system such as a satellite transponder. The canceller digitally down-converts the received signal and a local replica of the transmitted signal from IF to baseband, applies a variable delay and frequency compensation to the replica as a coarse delay and frequency correction, and tracks fine delay, amplitude and phase differences using an adaptive finite impulse response filter to generate a cancellation signal corresponding to the delayed and frequency shifted version. A minimum output power process produces an error signal that drives the variable delay and adaptive filter to minimize the power in the signal of interest to maximize cancellation of the interfering signal.
U.S. Pat. No. 7,349,505, whose disclosure is incorporated herein by reference, describes techniques 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 canceller module, providing a version of a modulated near signal as a first non-baseband interface signal from the transmitter system to the canceller module, providing a version of a composite signal as a second non-baseband interface signal from the receiver system to the canceller module, generating a cancellation signal at the canceller 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 canceller 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.
U.S. Pat. No. 7,522,877, whose disclosure is incorporated herein by reference, describes a method for reduction of echo noise in satellite communications, including receiving an aggregate signal from multiple remote stations, where the aggregate signal includes a transmit signal, whose bandwidth is in the range of 0.1 MHz to 66 MHz, is previously sent from a hub to the multiple receiving stations, computing a scaled, delayed and distorted replica of the transmit signal and using the replica to compensate for satellite transponder nonlinearities and reduce echo noise interference from a received aggregate signal received by the hub from the multiple remote stations.
U.S. Pat. No. 7,991,373, whose disclosure is incorporated herein by reference, describes a signal filtering system for a frequency reuse system. A first implementation includes a downlink baseband signal, coupled to a downlink bandwidth filter, including a composite received signal including at least an interfering signal and a signal of interest, each having a composite bandwidth, a first bandwidth, and a second bandwidth, respectively. An uplink baseband signal may be included, coupled to an uplink bandwidth filter, having a replica of the interfering signal corresponding with the interfering signal and having an interference bandwidth. A baseband processing module may be coupled with the downlink bandwidth filter and the uplink bandwidth filter and may be configured to cancel the interfering signal from the composite received signal using the replica of the interfering signal. The downlink bandwidth filter may be configured to reduce the composite bandwidth and the uplink bandwidth filter may be configured to reduce the interference bandwidth.
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