Abstract: A MAP decoding system in which one or more backward engines operate to calculate backward state probabilities for sub-blocks within a sliding window stored in a memory. One or more forward engines calculate forward state probabilities for a sub-block in the same order as the encoded symbols for the sub-block are stored. Calculation of the forward state probabilities for a sub-block are deferred until the backward state probabilities for the sub-block have been calculated. Responsive to the calculation of the forward and backward state probabilities, the one or more forward engines calculate and release soft outputs for a sub-block in synchronization with the calculation of the forward state probabilities. The sliding window may be moved throughout the block, and the foregoing process repeated until soft outputs for the entire block have been released.

Abstract: Iterative decoder employing multiple external code error checks to lower the error floor and/or improve decoding performance. Data block redundancy, sometimes via a cyclic redundancy check (CRC) or Reed Solomon (RS) code, enables enhanced iterative decoding performance. Improved decoding performance is achieved during interim iterations before the final iteration. A correctly decoded CRC block, indicating a decoded segment is correct with a high degree of certainty, assigns a very high confidence level to the bits in this segment and is fed back to inner and/or outer decoders (with interleaving, when appropriate) for improved iterative decoding. High confidence bits may be scattered throughout inner decoded frames to influence other bit decisions in subsequent iterations.

Abstract: A system for carrier phase tracking of symbols. In an embodiment employing a feedback structure, a symbol derotator pre-rotates a symbol by a derotation phase. A symbol and reliability estimation engine provides, responsive to the pre-rotated symbol, an estimate of the symbol and a reliability metric for the estimate. A tracking loop module determines a residual between the pre-rotated symbol and the symbol estimate, weights the residual by the reliability metric for the estimate, and determines a phase offset estimate responsive to the weighted residual. An accumulator then determines a next derotation phase responsive to the phase offset estimate. In an embodiment employing a feedforward structure, a symbol and reliability estimation engine provides an estimate of a symbol and a reliability metric for the estimate.

Abstract: Systems and techniques are disclosed for framing and processing single-carrier and/or OFDM transmit-diversity transmissions through delay-spread channels, as well as for deframing and processing the corresponding merged signals, received from a plurality of antennas, to estimate the transmitted information. Time-domain processing techniques may be used for both types of transmissions to create multiplexed dual signal-unit pairs, particularly when cyclic prefixes are needed to reduce delay-spreading effects. Repetitive pilot words may be employed in burst preambles and/or in payloads of transmission bursts to minimize or provide flexibility in the amount of bandwidth that is consumed to generate good channel response estimates under changing channel conditions.

Abstract: A method and apparatus for processing demodulated data comprising received symbol data is disclosed. A decoder is used to compute estimated symbols and corresponding reliability metrics. The reliability metrics are transformed into reliability weights. Optionally, residuals relating to the difference between the received symbol data and the estimated symbols are computed. Output data are generated comprising any combination of the following: estimated symbols, reliability weights, residuals, and received symbol data. The residuals may be weighted by the reliability metrics and used by demodulation or error compensation loops to instantaneously reduce or increase the bandwidth of these loops.

Abstract: A decoder having a first decoder providing first decoded data. A deinterleaver is included for deinterleaving the first decoded data. A second decoder provides second decoded data based on the deinterleaved first decoded data. The second decoder provides at least one decode status signal indicative of second decoder operations. A pipeline decoder unit is included that is coupled to the second decoder. The pipeline decoder unit includes an encoder that receives the second decoded data and provides forced decision data, a multiplexer, and a third decoder that provides pipelined decoded data. The multiplexer is responsive to the at least one decode status signal to selectively constrain the pipelined decoded data to be at least partially dependent on the forced decision data.

Abstract: A mobile wireless transceiver selects one of multiple nearby base stations to facilitate communication over a wireless network. Each base station transmits a pilot signal that includes a spreading signal transmitted at one of many possible phase offsets. The wireless transceiver selects an initial one of the possible phase offsets of the spreading signal and then correlates a received signal against the spreading signal at consecutive ones of the possible phase offsets. Correlation begins at the selected initial phase offset and continues until a component of the received signal and the spreading signal are aligned, indicating the detection of the pilot signal from one of the base stations.

Abstract: A system for determining an estimate of a multi-dimensional symbol, and one or more residuals between the symbol and the estimate. The one or more of the residuals may be weighted by the reliability metric for the multi-dimensional symbol. The residuals, weighted or unweighted, may then be used to update a derotation phase or phase offset estimate. The individual symbols in the multi-dimensional symbol may then be derotated responsive to the derotation phase or phase offset estimate.

Abstract: An iterative system for performing carrier phase tracking of symbols using a serial turbo decoder. Estimates of a buffered block of symbols are provided by a serial turbo decoder. Optionally, reliability metrics for the estimates are provided as well. Responsive to this information, a tracking loop module determines derotation phases for each of the symbols in the buffer. A symbol derotator derotates each of the buffered symbols in the block by its corresponding derotation phase. The derotated symbols are stored back in the buffer. The process may repeat itself for a prescribed number of iterations, after which the serial turbo decoder provides estimates of the underlying source bits.

Abstract: A duplex polarization adaptive system is described. The system provides polarization diversity for base station antennas under both receive and transmitting conditions. Since the base station provides polarization diversity in both transmit and receive modes, no polarization diversity is needed in the handheld unit. Even though the handheld unit does not provide polarization diversity, a duplex communication system, that uses polarization diversity for both the uplink and the downlink is provided, because the base station provides polarization diversity for the uplink and the downlink paths. By installing the two-way diversity at the base station, the overall cost of implementing diversity is reduced because one base station can typically serve many handsets. The base station antenna determines the polarization state of signals received from a remote unit, such as a handheld unit, using a polarization diverse antenna system. The base station then transmits using the same polarization state.

Abstract: An envelope feedforward technique is described that provides efficient, variable-power, linear amplification of an input signal. An input signal having phase and amplitude components is separated (decomposed) into an FM portion and an envelope portion. The FM portion contains the high frequency phase and frequency information from the input signal. The envelope portion contains the low frequency amplitude information from the input signal. An envelope combiner uses the envelope signal to amplitude-modulate the FM signal to produce an output signal. Spectral regrowth of the output signal is reduced by adjusting the relative time delays in the signal path of the envelope signal and the FM signal such that the FM signal and the envelope signal arrive at the envelope combiner at the same time. The envelope feedforward technique may be used to increase battery life in a handheld mobile RF unit such as a cellular telephone.

Abstract: A rate n/n recursive, systematic encoder. In combination with a bit to symbol mapper, the encoder advantageously forms an inner encoder of a serial concatenated trellis coded modulation encoder. The encoder may also form the inner encoder of a serial concatenated convolutional encoder. A related decoder is also described.

Abstract: A mobile wireless transceiver selects one of multiple nearby base stations to facilitate communication over a wireless network. Each base station transmits a pilot signal that includes a spreading signal transmitted at one of many possible phase offsets. The wireless transceiver selects an initial one of the possible phase offsets of the spreading signal and then correlates a received signal against the spreading signal at consecutive ones of the possible phase offsets. Correlation begins at the selected initial phase offset and continues until a component of the received signal and the spreading signal are aligned, indicating the detection of the pilot signal from one of the base stations.

Abstract: A mobile wireless transceiver selects one of multiple nearby base stations to facilitate communication over a wireless network. Each base station transmits a pilot signal that includes a spreading signal transmitted at one of many possible phase offsets. The wireless transceiver selects an initial one of the possible phase offsets of the spreading signal and then correlates a received signal against the spreading signal at consecutive ones of the possible phase offsets. Correlation begins at the selected initial phase offset and continues until a component of the received signal and the spreading signal are aligned, indicating the detection of the pilot signal from one of the base stations.

Abstract: A power amplifier for use in a wireless communication system operates like a quadrature mixer with conversion gain. The amplifier includes a local oscillator that generates two reference signals 90° out of phase with respect to each other. Four quadrature mixer elements receive signals representing the in-phase and quadrature components of a baseband signal. Each quadrature mixer amplifies the in-phase or the quadrature component of the baseband signal while upconverting with the corresponding reference signal.

Abstract: Iterative decoder employing multiple external code error checks to lower the error floor and/or improve decoding performance. Data block redundancy, sometimes via a cyclic redundancy check (CRC) or Reed Solomon (RS) code, enables enhanced iterative decoding performance. Improved decoding performance is achieved during interim iterations before the final iteration. A correctly decoded CRC block, indicating a decoded segment is correct with a high degree of certainty, assigns a very high confidence level to the bits in this segment and is fed back to inner and/or outer decoders (with interleaving, when appropriate) for improved iterative decoding. High confidence bits may be scattered throughout inner decoded frames to influence other bit decisions in subsequent iterations.

Abstract: A power amplifier for use in a wireless communication system operates like a quadrature mixer with conversion gain. The amplifier includes a local oscillator that generates two reference signals 90° out of phase with respect to each other. Four quadrature mixer elements receive signals representing the in-phase and quadrature components of a baseband signal. Each quadrature mixer amplifies the in-phase or the quadrature component of the baseband signal while upconverting with the corresponding reference signal.

Abstract: A power amplifier that amplifies an electrical signal that is passed through a power amplification array. The power amplifier is employed in various applications including cellular telephones, radio frequency signal transmission, and other electrical signal applications requiring power amplification. The power amplifier contains a number of power amplifiers arranged in a power amplifier array. To reproduce a particular envelope profile, a selected number of the power amplifiers of the power amplifier array is switched ON, whereas another selected number of the power amplifiers of the power amplifier array are switched OFF. All elements are fed with an RF signal containing phase information as well. The amplified, output signal provided after the power amplifier array is fed to an antenna for signal transmission.

Abstract: The envelope of a non-constant envelope signal is limited to certain maximum and minimum values. An envelope value is calculated for each pair of I-Q samples of the non-constant envelope signal and then is compared to the maximum and minimum values. If the envelope value lies above or below the maximum and minimum values, the I and Q signals are scaled so that the envelope value lies between these values. In some embodiments, the threshold values are selected to ensure that the probability that the envelope value will exceed these values is less than a predetermined amount (e.g., between 0.01 and 0.001).