Abstract: An embodiment includes a method for generating a set of synchronization/pilot sequences (SPS) by generating a plurality of candidate SPS using different initial conditions. Correlations are performed among the candidate SPS to generate a plurality of correlation values, and a plurality of permutations of the candidate SPS are determined, where each permutation includes a different set of candidate SPS, and wherein each permutation includes a number, D, of candidate SPS. In addition a selected permutation is identified from the plurality of permutations, where the selected permutation corresponds to the set of SPS being generated. A system includes a transmitter adapted to generate a wireless signal in which an SPS is embedded by combining each SPS of the set with phase shifted input data, determining peak-to-average power ratios (PARs) for at least some of the combined signals, and identifying a selected combined signal based on the PARs.

Abstract: An embodiment for wirelessly communicating a signal includes a transmitter combining a plurality of phase shifted input data signals with a plurality of synchronization/pilot sequences to produce a plurality of combined signals, performing frequency domain-to-time domain transformations of the combined signals to produce a plurality of candidate signals, determining peak-to-average ratios for at least some of the plurality of candidate signals, identifying a selected signal from the plurality of candidate signals based on the peak-to-average ratios, and transmitting the selected signal over a wireless communication channel.

Abstract: An embodiment for wirelessly communicating a signal includes a transmitter combining a plurality of phase shifted input data signals with a plurality of synchronization/pilot sequences to produce a plurality of combined signals, performing frequency domain-to-time domain transformations of the combined signals to produce a plurality of candidate signals, determining peak-to-average ratios for at least some of the plurality of candidate signals, identifying a selected signal from the plurality of candidate signals based on the peak-to-average ratios, and transmitting the selected signal over a wireless communication channel.

Abstract: In an embodiment, a receiver includes an antenna configured to receive a communication frame. The communication frame may include an acquisition code symbol sequence, which in turn may include a plurality of acquisition code symbols. In an embodiment, an acquisition code symbol includes a subcode sequence having a plurality of subcodes. A receiver also may include a correlation calculator coupled to the antenna. The correlation calculator may be configured to determine a correlation between the subcodes of the received communication frame and a stored version of the subcodes. The correlation may be used in determining a timing offset for further processing of the communication frame.

Abstract: An embodiment for wirelessly communicating a signal includes a transmitter combining a plurality of phase shifted input data signals with a plurality of synchronization/pilot sequences to produce a plurality of combined signals, performing frequency domain-to-time domain transformations of the combined signals to produce a plurality of candidate signals, determining peak-to-average ratios for at least some of the plurality of candidate signals, identifying a selected signal from the plurality of candidate signals based on the peak-to-average ratios, and transmitting the selected signal over a wireless communication channel.

Abstract: An embodiment for wirelessly communicating a signal includes a transmitter generating and transmitting a wireless signal over a wireless communication channel. The wireless signal includes a guard band, data represented within a plurality of data-bearing subcarriers, and a plurality of pilot signals represented within a plurality of pilot subcarriers. In an embodiment, the plurality of pilot signals have variable pilot signal parameters selected from a group of parameters that includes pilot power and pilot spacing with respect to adjacent pilots. An embodiment further includes a receiver receiving a channel-affected version of the wireless signal, and producing a corrected signal by applying corrections to the received signal based on estimated channel perturbations within the received signal, where the estimated channel perturbations are determined based on the plurality of pilot signals. The receiver also produces an output data symbol from the corrected signal.

Abstract: Embodiments include methods and apparatus for verifying the detection of a correlation peak, which may represent an acquisition of a received acquisition code symbol sequence. The method includes determining a series of coherently-aligned peaks from a series of correlation peaks. Determining the plurality of coherently-aligned peaks includes correcting a frequency offset and a phase offset for each of the plurality of correlation peaks. A coherent match filter process is performed on the plurality of coherently-aligned peaks. A detection of the correlation peak may be verified when the match filter result exceeds a threshold.

Abstract: A method (20) of orthogonal frequency-division multiplex (OFDM) communication via a plurality of subchannels (30) within a noncontiguous wideband channel (24) is provided. The method (20) determines an SNR for each of the subchannels (30). The method (20) then designates a subchannel (30) as clear (93) when its SNR is greater than a least-SNR threshold (70), as impeded (95) when its SNR is less than the least-SNR threshold and greater than an SNR-evaluation threshold, and as obstructed (111) when its SNR is less than both the least-SNR and the SNR-evaluation thresholds. The method (20) then transmits OFDM data (34) so that each of the clear subchannels receives the OFDM data (34) at a maximum subchannel signal level (40), each of the impeded subchannels receives the OFDM data (34) at an intermediate subchannel signal level (42), and each of the obstructed subchannels receives the OFDM data (34) at zero subchannel signal level (44).

Abstract: An embodiment for wirelessly communicating a signal includes a transmitter generating and transmitting a wireless signal over a wireless communication channel. The wireless signal includes a guard band, data represented within a plurality of data-bearing subcarriers, and a plurality of pilot signals represented within a plurality of pilot subcarriers. In an embodiment, the plurality of pilot signals have variable pilot signal parameters selected from a group of parameters that includes pilot power and pilot spacing with respect to adjacent pilots. An embodiment further includes a receiver receiving a channel-affected version of the wireless signal, and producing a corrected signal by applying corrections to the received signal based on estimated channel perturbations within the received signal, where the estimated channel perturbations are determined based on the plurality of pilot signals. The receiver also produces an output data symbol from the corrected signal.

Abstract: An embodiment for wirelessly communicating a signal includes a transmitter combining a plurality of phase shifted input data signals with a plurality of synchronization/pilot sequences to produce a plurality of combined signals, performing frequency domain-to-time domain transformations of the combined signals to produce a plurality of candidate signals, determining peak-to-average ratios for at least some of the plurality of candidate signals, identifying a selected signal from the plurality of candidate signals based on the peak-to-average ratios, and transmitting the selected signal over a wireless communication channel.

Abstract: An embodiment includes a method for generating a set of synchronization/pilot sequences (SPS) by generating a plurality of candidate SPS using different initial conditions. Correlations are performed among the candidate SPS to generate a plurality of correlation values, and a plurality of permutations of the candidate SPS are determined, where each permutation includes a different set of candidate SPS, and wherein each permutation includes a number, D, of candidate SPS. In addition a selected permutation is identified from the plurality of permutations, where the selected permutation corresponds to the set of SPS being generated. A system includes a transmitter adapted to generate a wireless signal in which an SPS is embedded by combining each SPS of the set with phase shifted input data, determining peak-to-average power ratios (PARs) for at least some of the combined signals, and identifying a selected combined signal based on the PARs.

Abstract: Apparatus are provided for a communication signal processing apparatus having a channel estimator configured to generate a first channel estimation at a first time point, a linear predictor coupled to the channel estimator, and an adaptive filter coupled with the linear predictor. The linear predictor is configured to predict a second channel estimation based on a second time point and a channel frequency. The second time point is concurrent or subsequent to the first time point. The second channel estimation includes a first coefficient. The linear predictor includes a first predictor having a sample time point. The first predictor is configured to generate the first coefficient of the second channel estimation based on the sample time point and the second time point. The sample time point is prior to the second time point. The adaptive filter is configured to recursively determine the second channel estimation.

Abstract: In an embodiment, a receiver includes an antenna configured to receive a communication frame. The communication frame may include an acquisition code symbol sequence, which in turn may include a plurality of acquisition code symbols. In an embodiment, an acquisition code symbol includes a subcode sequence having a plurality of subcodes. A receiver also may include a correlation calculator coupled to the antenna. The correlation calculator may be configured to determine a correlation between the subcodes of the received communication frame and a stored version of the subcodes. The correlation may be used in determining a timing offset for further processing of the communication frame.

Abstract: Embodiments include methods and apparatus for verifying the detection of a correlation peak, which may represent an acquisition of a received acquisition code symbol sequence. The method includes determining a series of coherently-aligned peaks from a series of correlation peaks. Determining the plurality of coherently-aligned peaks includes correcting a frequency offset and a phase offset for each of the plurality of correlation peaks. A coherent match filter process is performed on the plurality of coherently-aligned peaks. A detection of the correlation peak may be verified when the match filter result exceeds a threshold.

Abstract: A symbol synchronizer (100) is provided for a software-defined communications system (10). The symbol synchronizer (100), when integrated into either a pre- or post-detection diversity signal combiner (108, 208), enables highly accurate signal synchronization with minimal added system complexity. The symbol synchronizer (100) includes a single complex sliding window-matched filter (102) for filtering an input digital signal with a match filtering function based on predetermined signal transfer function characteristics to average out receiver noise from the signal. A signal delay bank (84) includes a plurality of delay blocks each for delaying the digital signal filtered by the single matched filter for a predetermined number of samples. A complex correlator (88) correlates the digital signal filtered by the single complex sliding window matched filter (102) and delayed by the complex correlator (88) with a correlator reference signal, and selects an index of a path having a peak correlator value.

Abstract: A multi-carrier communication system (400) groups subchannels (802) into different quality-of-signal (QoS) regions (804). An unconstrained optimization process (1200) is performed independently for the subchannels (802) of the different QoS regions (804) to allocate bit rates and power to the individual subchannels (802) so that the indicated QoS will result. Coders (504, 508, 512, 516, 1700) partition and error-correction encode source information using encoding schemes matched to the different QoS regions (804). A set (1100) of only a few directed QoS partition vectors (1102) direct the unconstrained optimization process (1200) to attempt bit-rate and power allocations on only a few promising groupings of subchannels (802) and QoS regions (804). An iterative process may take place between bit-rate and power allocation on one side and source information coding on the other for different directed QoS partition vectors (1102) to identify the best solution.

Abstract: A multi-carrier communication system (400) groups subchannels (802) into different quality-of-signal (QoS) regions (804). An unconstrained optimization process (1200) is performed independently for the subchannels (802) of the different QoS regions (804) to allocate bit rates and power to the individual subchannels (802) so that the indicated QoS will result. Coders (504, 508, 512, 516) partition and error-correction encode source information using encoding schemes matched to the different QoS regions (804). A set (1100) of only a few directed QoS partition vectors (1102) direct the unconstrained optimization process (1200) to attempt bit-rate and power allocations on only a few promising groupings of subchannels (802) and QoS regions (804). An iterative process may take place between bit-rate and power allocation on one side and source information coding on the other for different directed QoS partition vectors (1102) to identify the best solution.

Abstract: A symbol synchronizer (100) is provided for a software-defined communications system (10). The symbol synchronizer (100), when integrated into either a pre- or post-detection diversity signal combiner (108, 208), enables highly accurate signal synchronization with minimal added system complexity. The symbol synchronizer (100) includes a single complex sliding window matched filter (102) for filtering an input digital signal with a match filtering function based on predetermined signal transfer function characteristics to average out receiver noise from the signal. A signal delay bank (84) includes a plurality of delay blocks each for delaying the digital signal filtered by the single matched filter for a predetermined number of samples. A complex correlator (88) correlates the digital signal filtered by the single complex sliding window matched filter (102) and delayed by the complex correlator (88) with a correlator reference signal, and selects an index of a path having a peak correlator value.

Abstract: A communications system (100) includes a multi-rate source coder (MRSC) (102), a variable size/rate buffer (VSRB) (112), a speech buffer (104), and a buffer control block (106). The variable size/rate buffer (112) includes a source coder bit buffer (SCBB) (114) and an adaptive transmit frame buffer (116). The source coder bit buffer (114) receives speech frames coded at different rates from the multi-rate source coder (102), and deposits an integer or non-integer number of frames in the adaptive transmit frame buffer (ATFB) (116). A receiver includes a seamless rate transition module (SRTM) (308) and an variable buffer (310). The seamless rate transition module (308) correlates speech data previously coded at different rates, and it then truncates or alternatively appends, concatenates, and warps the speech data to remove any annoying artifacts at the rate change boundary.

Abstract: An orthogonal frequency division multiplexed wideband communication system provides improved time and frequency synchronization by inserting an unevenly spaced pilot sequence within the constellation data. A receive correlates the received data using the unevenly spaced pilot sequence. The pilot sequence is generated with a maximum length pseudo random noise code and inserted into frequency bins having prime numbers.