Abstract: A multi-stage receiver including, in one embodiment, a sequence of processing stages. At least one of the processing stages includes a first processing block, a delay block, and a second processing block. The first processing block is adapted to receive an input signal and generate from the input signal one or more processing parameters. The delay block is adapted to generate a delayed signal. The second processing block is adapted to apply the one or more processing parameters to the delayed signal to generate an output signal. The delay block compensates for one or more processing delays associated with the generation of the one or more processing parameters by the first processing block.

Abstract: A technique for estimating the Doppler frequency of an input signal comprising a pilot signal. In one embodiment, the technique comprises: (a) accumulating a plurality of samples from the input signal over a specified time duration to derive a channel tap estimate; (b) obtaining a sequence of channel tap estimates by repeating step (a) until a specified number of channel tap estimates have been accumulated; (c) performing a Fourier transform of the sequence of channel tap estimates to obtain a complex sequence of values; (d) finding the smallest index value for which a power spectral distribution function of the complex sequence of values exceeds a specified threshold; and (e) obtaining an estimate of the Doppler frequency by dividing the smallest index value found in step (d) by the product of the specified number of channel tap estimates and the specified time duration.

Abstract: In one embodiment, the present invention is a method for reducing the peak-to-average power ratio (PAPR) of a multi-carrier modulated symbol, such as an orthogonal frequency division multiplexed (OFDM) symbol. The method first transforms a set of data symbols into a multi-carrier modulated symbol. The method then uses the multi-carrier modulated symbol and a gradient-descent algorithm to generate a set of symbols for PAPR-reduction tones. The data symbols and the PAPR-reduction symbols are then transformed to generate an updated multi-carrier modulated symbol. The PAPR-reduction symbols are iteratively updated until a terminating condition occurs (e.g., an acceptable PAPR is achieved for the multi-carrier modulated symbol).

Abstract: In one embodiment, a receiver has an equalizer, a tap-averaging block, a delay buffer, and a filter. The equalizer receives an input signal from upstream processing and generates sets of filter coefficients. Each set of filter coefficients is adaptively generated by 1) filtering the received signal to generate an equalized signal, 2) calculating an error of the equalized signal, and 3) generating a new set of coefficients based on the error of the equalized signal. The sets of filter coefficients are output to the tap-averaging block, which averages groups of the sets of filter coefficients to generate sets of averaged filter coefficients, where each averaged set is output to the filter. The filter receives a time-delayed version of the input signal from the delay buffer and applies the current set of averaged filter coefficients to the time-delayed signal. The filtered signal is then output to downstream processing.

Abstract: In one embodiment, the present invention is a method for reducing the peak-to-average power ratio (PAPR) of a multi-carrier modulated symbol, such as an orthogonal frequency division multiplexed (OFDM) symbol. The method first transforms a set of data symbols into a multi-carrier modulated symbol. The method then uses the multi-carrier modulated symbol and a gradient-descent algorithm to generate a set of symbols for PAPR-reduction tones. The data symbols and the PAPR-reduction symbols are then transformed to generate an updated multi-carrier modulated symbol. The PAPR-reduction symbols are iteratively updated until a terminating condition occurs (e.g., an acceptable PAPR is achieved for the multi-carrier modulated symbol).

Abstract: In one embodiment, an HSDPA co-processor for 3GPP Release 6 Category 8 (7.2 Mb/s) HSDPA that provides all chip-rate, symbol-rate, physical-channel, and transport-channel processing for HSDPA in 90 nm CMOS. The co-processor design is scalable to all HSDPA data rates up to 14 Mb/s. The coprocessor implements an Advanced Receiver based on an NLMS equalizer, supports RX diversity and TX diversity, and provides up to 6.4 dB better performance than a typical single-antenna rake receiver. Thus, 3GPP R6 HSDPA functionality can be added to a legacy R99 modem using an HSDPA co-processor consistent with embodiments of the present invention, at a reasonable incremental cost and power.

Abstract: In one embodiment, a receiver has an equalizer, a tap-averaging block, a delay buffer, and a filter. The equalizer receives an input signal from upstream processing and generates sets of filter coefficients. Each set of filter coefficients is adaptively generated by 1) filtering the received signal to generate an equalized signal, 2) calculating an error of the equalized signal, and 3) generating a new set of coefficients based on the error of the equalized signal. The sets of filter coefficients are output to the tap-averaging block, which averages groups of the sets of filter coefficients to generate sets of averaged filter coefficients, where each averaged set is output to the filter. The filter receives a time-delayed version of the input signal from the delay buffer and applies the current set of averaged filter coefficients to the time-delayed signal. The filtered signal is then output to downstream processing.

Abstract: In one embodiment, an equalizer equalizes two versions of a signal that are received through separate propagation paths, to generate one equalized signal. The equalizer comprises a single FIR filter and an NLMS updater. During each iteration, the NLMS updater supplies a set of coefficients to the FIR filter. The FIR filter processes samples of both the first and second versions by multiplying each sample by one coefficient in the set of coefficients to generate a number of products. The products are combined by a summation block to generate an equalized sample. The equalized sample is compared to a reference signal to generate an error measure used to update the set of coefficients. The samples of the received versions are then advanced and this process is repeated to generate further equalized samples. In further embodiments, the equalizer may process more than two versions of a signal.