Abstract: A weighted mean arrival time determines a delay offset of a fractionally spaced equalizer. The weighted mean arrival time is determined using path arrival times and energies from a Rake receiver. The difference between a weighted mean arrival time and a current delay offset is set to a difference X, in units of the equalizer tap spacing. If the difference X is greater than or equal to 1 or less than or equal to −1, then the current delay offset is updated by an incremental delay offset and the equalizer filter coefficients are shifted by a number of tap spacings. Otherwise, the current delay offset is not updated and the filter coefficients of the fractionally spaced equalizer are not shifted. Adaptation of the filter coefficients and updates of the delay offset of the equalizer occur only during pilot bursts so as to minimize adaptation transients.

Abstract: A communication receiver (400) minimizes a combined local and global mean square error for signal equalization. A base station (101) or a mobile station (102-104) may include a plurality of antennas (292) for receiving a plurality of signals transmitted from a common source. The plurality of signals carry a common stream of data symbols. A pre-processing block (299) processes the received signals to produce a plurality of processed received signals (298). A signal equalizer (401) minimizes a combined local and global MSE over the processed received signals (298) to produce a combined signal (499). A decoder decodes the combined signal (499) to retrieve the stream of data symbols. A processor is configured for combining a local MSE and a global MSE in accordance with an adjustable weighting factor a to produce the combined local and global MSE.

Abstract: Techniques to process data for transmission in a time division duplexed (TDD) communication system. In one aspect, the frequency response of a forward link is estimated at a base station based on reverse link transmissions (e.g., pilots) from a terminal. Prior to a data transmission on the forward link, the base station determines a reverse transfer function based on the pilots transmitted by the terminal, “calibrates” the reverse transfer function with a calibration function to derive an estimate of a forward transfer function, and preconditions modulation symbols based on weights derived from the forward transfer function. In another aspect, the terminal estimates the “quality” of the forward link and provides this information to the base station. The base station then uses the information to properly code and modulate data prior to transmission such that the transmitted data can be received by the terminal at the desired level of performance.

Abstract: Method and apparatus that compensates for overestimation of channel SINR due to overfitting of an adaptive equalizer to the pilot portion of a received frame. The SINR of a wireless channel is estimated by adapting an adaptive equalizer using the pilot portion of the frame, applying the adaptive equalizer to a non-pilot portion of the frame, determining a parameter using the adaptive equalizer output, and estimating the SINR of the wireless channel using the parameter. The parameter can include, for example, the mean square error (MSE) or the bias of the equalizer output. The accuracy of the SINR estimate according to this aspect of the present invention is thereby improved (as compared to a SINR estimate based on parameters calculated during the pilot interval) because the adaptive equalizer is not overfit to the control or data portions of the frame.

Abstract: The present invention relates to a method and apparatus for adaptively compensating for channel or system variations in which adaptive compensation is used in the receiver of a digital communication system. The transmitter of the digital communication system includes precoding. The adaptive receiver compensation mitigates the interferences not removed by the transmitter precoder. In an embodiment of the invention, the adaptive compensation can be performed using an adaptive feedforward filter (FFF) and a feedback filter (FBF) in the receiver. The FBF output is generated based on previous values of estimates of the transmitted precoded sequence. The determined value of the FBF coefficients can be periodically relayed to the transmitter to update the precoder coefficients of the transmitter. Alternatively, the value of the FBF coefficients can be relayed to the transmitter after the value of the coefficients exceeds a predetermined threshold.