Abstract: The present invention pertains to a transmitter that can exploit feedback to help it organize information which is subsequently sent to a receiver. More specifically, the transmitter receives a feedback signal from the receiver and then uses data about a channel in the feedback signal to adapt at least one of a coding, interleaving and modulating scheme to organize information which is subsequently transmitted to the receiver. In this way, the transmitter can obtain the best match of a channel and a given information payload.

Abstract: A Direct-Sequence Code Division Multiple Access (DS-CDMA) receiver and method of allocating probing correlators and combining correlators (fingers). A front-end processor converts received radio signals to baseband samples. Based on average path strengths, a controller adaptively allocates probing correlators to signal paths to de-spread certain received signals. Based on path power estimates, the controller adaptively allocates combining correlators to signal paths. The allocations may be made to minimize the total received power at the receiver, or to achieve acceptable performance for all users.

Abstract: A method of generating a control signal to enable or inhibit a wide variety of applications is provided. The method generally includes the steps of determining the location of a first mobile radio terminal, determining the location of a second mobile radio terminal, comparing the locations of the terminals, and generating a control signal based upon the comparison. The control signal may be generated if the first and second mobile radio terminals are within a specified distance of one another. Alternatively, the control signal may be generated if the first and second mobile radio terminals are separated by at least a specified distance from one another. Additionally, the control signal may be generated if it is determined that the first mobile radio terminal is at a first specified location and the second mobile radio terminal is at a second specified location spacially separated from the first specified location.

Abstract: Methods and apparatus for canceling co-channel interference in a receiving system using spatio-temporal whitening. In some embodiments, a spatio-temporal interference canceling method, and apparatus for carrying out the method are provided which effectively cancel co-channel interference despite frequency offset between the desired signal and the interferer in a TDMA type system. Real and imaginary component values of the total received signal are used for virtual diversity branches, and a vector-valued auto regressive model is used to characterize the interference. In other embodiments, spatio-temporal interference whitening is used to improve timing estimates used for synchronization. The two uses of spatio-temporal whitening can be combined in one receiver. The invention is typically implemented in one or more programmed digital signal processors or application specific integrated circuits (ASICS), embodied in a receiving system.

Abstract: A wireless communication receiver, such as the receiver included in a wireless communication transceiver implemented in a base station or in a mobile station of a wireless communication network, includes a parametric G-RAKE receiver circuit and a method that compute parametric scaling parameters on a per transmission interval basis. In one embodiment, measured impairment correlations are obtained for an individual transmission slot and used to estimate instantaneous values of the scaling parameters. One or both of those instantaneous values are then constrained according to one or more defined limits. In other embodiments, multiple transmission slots are used to increase the number of measurements available to estimate the scaling parameters, with parameter constraining optionally applied. Further embodiments use iterative methods and/or solve for one parameter, and use the results to obtain the other parameter(s).

Abstract: A gain processor circuit calculates a first AGC signal for a first one of a number of receive chains, each including a gain-controlled front-end circuit, and derives one or more additional AGC signals from the calculation of that first AGC signal for any remaining chains. The first AGC signal may be calculated by tracking received power for one or more of the receive chains. An AGC signal may be derived for each additional receive chain by assuming that its received power is the same, i.e., the same AGC command is used. Alternatively, an additional AGC command is derived based on a scaling value determined from a ratio of received powers for the first and additional receive chains. Such powers may be expressed as channel tap powers, which may be available from other circuit elements associated with signal demodulation. Alternatively, the scaling value further incorporates received interference and/or noise powers.

Abstract: A method and apparatus carry out received signal processing for received communication signals based on least squares processing to estimate the contribution of one or more interferer signals. The exemplary receiver uses interferer signal channel estimates to obtain least squares estimates for the interference contributions of one or more interferer signals, and then uses those estimates to suppress interference during demodulation processing. Further, the least-squares estimates may be used to obtain a reduced search space wherein the candidate set of signals searched during demodulation processing is reduced.

Abstract: A method and apparatus derives an impairment correlation matrix to process signals received at a wireless receiver over multiple paths of a multi-path channel. The receiver includes first and second impairment correlation estimators for estimating first and second impairment correlation matrices based on despread symbols received over multiple paths of a multi-path channel. The receiver then derives the impairment correlation matrix based on the estimated first and second impairment correlation matrices. The receiver may combine traffic despread values to suppress interference using weighting factors calculated based on the derived impairment correlation matrix. Further, the receiver may estimate a signal-to-interference ratio based on the derived impairment correlation matrix.

Abstract: A system and method of audio processing provides enhanced speech recognition. Audio input is received at a plurality of microphones. The multi-channel audio signal from the microphones may be processed by a beamforming network to generate a single-channel enhanced audio signal, on which voice activity is detected. Audio signals from the microphones are additionally processed by an adaptable noise cancellation filter having variable filter coefficients to generate a noise-suppressed audio signal. The variable filter coefficients are updated during periods of voice inactivity. A speech recognition engine may apply a speech recognition algorithm to the noise-suppressed audio signal and generate an appropriate output. The operation of the speech recognition engine and the adaptable noise cancellation filter may advantageously be controlled based on voice activity detected in the single-channel enhanced audio signal from the beamforming network.

Abstract: The present application describes a new path search and verification method and apparatus for identifying and selecting one or more delays for a receiver. A front-end receiver receives a signal having one or more signal images, where each signal image has a corresponding signal delay. A tree generator builds a hierarchical delay tree from a plurality of delay nodes, each corresponding to one of the signal delays. A tree searcher searches through the delay tree to identify one or more surviving delay nodes, where each surviving delay node corresponds to a candidate delay for the receiver. The receiver may also include a state machine comprising a plurality of ordered states for providing candidate delays for the receiver. The state machine stores the candidate delays and shifts the candidate delays between states within the state machine based on the latest results from the tree searcher.

Abstract: Interference, such as inter-symbol interference, from a symbol of interest in a RAKE receiver is reduced. The RAKE receiver comprises a plurality of RAKE fingers, a processor, and a combiner. The plurality of RAKE fingers despread symbols received over multiple paths of a multi-path channel. The processor determines cross-correlations between symbol waveforms from different symbols and multiple paths. The combiner combines the despread symbols using the cross-correlations to reduce interference from the symbol of interest.

Abstract: Channel and correlation characteristics are determined for a composite signal. Respective combining weights for information from the composite signal are determined for respective ones of a plurality of candidate delays based on the determined channel and correlation characteristics. A group of delays, e.g., RAKE correlator delays or chip equalizer filter taps, is selected from the plurality of candidate delays based on the determined weights. Information from the composite signal for the selected delays is processed according to a spreading code to generate a symbol estimate. The invention may be embodied as methods, apparatus and computer program products.

Abstract: A RAKE receiver circuit generates combining weights based on channel estimates and combining statistics that comprise channel coefficient statistics, noise statistics, and channel estimation error statistics. Together, these statistics incorporate the relationships in noise and channel estimation across two or more RAKE fingers, and thus improve combining weight generation. Exemplary determination of statistics comprises channel coefficient cross-correlations, noise cross-correlations, and channel estimation error cross-correlations. Determination of the statistics can be varied based on, for example, the assumption of default or nominal signal models.

Abstract: A receiver based on a RAKE receiver architecture includes a logic circuit configured to assign one or more RAKE fingers to a finger placement grid that is independent from a searcher delay grid used by the receiver's searcher in generating multipath delay profiles for received signals. The logic circuit may use the multipath delay profile to “tune” the finger placement grid relative to the searcher delay grid but the delay resolution of the finger placement grid is independent of the searcher delay grid. This independence permits, for example, setting the finger placement grid to a delay resolution based on a Nyquist criterion independently from the delay resolution used by the searcher. The receiver may use two or more finger placement grids, may operate in a mixed mode where fingers are assigned on- and off-grid, and may operate selectively in grid or non-grid modes.

Abstract: A wireless communication device includes at least two antennas with at least two corresponding receive chains. Selectively activating and deactivating the receivers as needed for a desired quality of reception controls the performance and power consumption of the wireless communication device. The wireless communication device may operate in a single receiver mode or a dual receiver diversity mode. In the dual receiver diversity mode, the wireless communication device may selectively control the gain of one or more antennas and/or reconfigure one or more receive chains to minimize power consumption while maintaining a desired performance.

Abstract: A method of forward link power control in a CDMA mobile communication system is adapted for diversity transmission. First and second diversity signals are transmitted from a base station to a mobile terminal. The mobile terminal derives first and second channel quality estimates associated with the first and second diversity signals respectively. The mobile terminal uses the channel quality estimates to derive first and second power control codes which it transmits to said base station. The base station adjusts the transmit power of first and second antennas associated with the base station based on the first and second power control codes, respectively.

Abstract: A system and method of audio processing provides enhanced speech recognition. Audio input is received at a plurality of microphones. The multi-channel audio signal from the microphones may be processed by a beamforming network to generate a single-channel enhanced audio signal, on which voice activity is detected. Audio signals from the microphones are additionally processed by an adaptable noise cancellation filter having variable filter coefficients to generate a noise-suppressed audio signal. The variable filter coefficients are updated during periods of voice inactivity. A speech recognition engine may apply a speech recognition algorithm to the noise-suppressed audio signal and generate an appropriate output. The operation of the speech recognition engine and the adaptable noise cancellation filter may advantageously be controlled based on voice activity detected in the single-channel enhanced audio signal from the beamforming network.

Abstract: A spread spectrum signal is processed by correlating the spread spectrum signal with a spreading sequence at a first plurality of correlation times to produce a first plurality of time-offset correlations. The first plurality of time-offset correlations is processed to produce a first symbol representation for a symbol. A first quality is determined for the first symbol representation. Responsive to the determined first quality, it is determined whether to further process the first symbol representation or to process a second symbol representation for the symbol generated from the spread spectrum signal. The first quality may be determined, for example, by decoding the first symbol representations to generate a decoding metric or error check indicator, such as a CRC result. The symbol representations may be generated and/or evaluated for quality in a serial fashion or a parallel fashion.

Abstract: A symbol is transmitted in a communications medium according to a first spreading sequence of a set of spreading sequences, for example, CDMA channelization codes, which may be used to transmit symbols in the system. A communications signal is received from the communications medium, for example, at a mobile terminal. The received communications signal is resolved into a plurality of multipath signal components by, for example, descrambling the received signal according to a cell-specific scrambling code. The resolved plurality of signal components is correlated with the set of spreading sequences to generate a respective set of correlations for a respective one of the resolved signal components, a respective one of the sets of correlations including a respective correlation of a resolved signal component with the first spreading sequence.

Abstract: A CDMA communication system uses a set of quasi-orthogonal codes to supplement the standard set of Walsh codes used in conventional systems. Users are assigned a code selected from the set of Walsh codes, if available. If the number of users exceeds the number of available Walsh codes, selected users are assigned to quasi-orthogonal codes. The users assigned quasi-orthogonal codes are chosen based on user mobility.