Abstract: A detector and an interference cancellation method for a spatial multiplexing filter bank multicarrier with offset quadrature amplitude modulation (SM-FBMC/OQAM) system are provided. The detector includes a decision unit, an inter-symbol feedback filtering unit and an inter-antenna feedback filtering unit. The decision unit is configured to receive a plurality of reception signals corresponding to a subchannel and a plurality of reception antennas to output a decision signal corresponding to the subchannel and a transmission antenna. The inter-symbol feedback filtering unit is configured to feed back the decision signal corresponding to the subchannel and the transmission antenna to eliminate an inter-symbol interference (ISI). The inter-antenna feedback filtering unit is configured to feed back a decision signal corresponding to the subchannel and another transmission antenna to eliminate an inter-antenna interference (IAI).

Abstract: For frequency bin error estimation, multiple hypotheses are formed for different frequency bin errors, pilot offsets, or combinations of frequency bin error and pilot offset. For each hypothesis, received symbols are extracted from the proper subbands determined by the hypothesis. In one scheme, the extracted received symbols for each hypothesis are despread with a scrambling sequence to obtain despread symbols for that hypothesis. A metric is derived for each hypothesis based on the despread symbols, e.g., by deriving a channel impulse response estimate based on the despread symbols and then deriving the metric based on the channel impulse response estimate. In another scheme, the extracted received symbols for each hypothesis are correlated, and a metric is derived based on the correlation results. For both schemes, the frequency bin error and/or the pilot offset are determined based on the metrics for all hypotheses evaluated.

Abstract: For frequency bin error estimation, multiple hypotheses are formed for different frequency bin errors, pilot offsets, or combinations of frequency bin error and pilot offset. For each hypothesis, received symbols are extracted from the proper subbands determined by the hypothesis. In one scheme, the extracted received symbols for each hypothesis are despread with a scrambling sequence to obtain despread symbols for that hypothesis. A metric is derived for each hypothesis based on the despread symbols, e.g., by deriving a channel impulse response estimate based on the despread symbols and then deriving the metric based on the channel impulse response estimate. In another scheme, the extracted received symbols for each hypothesis are correlated, and a metric is derived based on the correlation results. For both schemes, the frequency bin error and/or the pilot offset are determined based on the metrics for all hypotheses evaluated.

Abstract: Techniques for performing time tracking at a receiver are described. A first arriving path (FAP) and a last arriving path (LAP) are detected based on a channel impulse response estimate for a communication channel. The detected FAP and LAP may be correct or swapped. To resolve ambiguity in the detected FAP and LAP, a first hypothesis corresponding to the FAP and LAP being correctly detected and a second hypothesis corresponding to the FAP and LAP being incorrectly detected are evaluated. For each hypothesis, hypothesized FAP and LAP are determined based on the detected FAP and LAP, a correlation window is determined based on the hypothesized FAP and LAP, and correlation is performed using the correlation window. The correct hypothesis is determined based on correlation results for the two hypotheses. The receiver timing is updated based on the hypothesized FAP and LAP for the correct hypothesis and used for demodulation.

Abstract: A “unified” modulator for multiple modulation schemes (e.g., GMSK and 8PSK) is described. The waveform for each modulation scheme is generated based on a set of one or more pulse shaping functions. The waveforms for all supported modulation schemes may be generated based on a composite set of all the different pulse shaping functions. The unified modulator includes a filter for each pulse shaping function in the composite set. To generate the waveform for a selected modulation scheme, the set of one or more filters for this modulation scheme is enabled and all other filters are disabled. The outputs from all enabled filters are summed to generate a modulator output. When switching between modulation schemes, a smooth transition may be obtained by (1) providing a suitable data pattern for each filter to be enabled or disabled and (2) generating symbols for the new modulation scheme with an appropriate initial phase.

Abstract: An efficient method and apparatus for implementing a back-end channel matched filter in a receiver is disclosed. A typical channel matched filter embodiment includes a peak detector for establishing processing synchronization from a despread signal, a channel estimator producing a channel impulse response (CIR) estimate from the despread signal based on the synchronization by the peak detector and a back-end symbol combiner coherently combining dominant multipath components of the despread signal by weights based on the CIR estimate based on the synchronization by the peak detector to generate a decision variable. In a digital spread spectrum implementation, the despread signal operated on by the channel matched filter has been previously been correlated with a spreading sequence replica.

Abstract: For frequency bin error estimation, multiple hypotheses are formed for different frequency bin errors, pilot offsets, or combinations of frequency bin error and pilot offset. For each hypothesis, received symbols are extracted from the proper subbands determined by the hypothesis. In one scheme, the extracted received symbols for each hypothesis are despread with a scrambling sequence to obtain despread symbols for that hypothesis. A metric is derived for each hypothesis based on the despread symbols, e.g., by deriving a channel impulse response estimate based on the despread symbols and then deriving the metric based on the channel impulse response estimate. In another scheme, the extracted received symbols for each hypothesis are correlated, and a metric is derived based on the correlation results. For both schemes, the frequency bin error and/or the pilot offset are determined based on the metrics for all hypotheses evaluated.

Abstract: Techniques for performing time tracking at a receiver are described. A first arriving path (FAP) and a last arriving path (LAP) are detected based on a channel impulse response estimate for a communication channel. The detected FAP and LAP may be correct or swapped. To resolve ambiguity in the detected FAP and LAP, a first hypothesis corresponding to the FAP and LAP being correctly detected and a second hypothesis corresponding to the FAP and LAP being incorrectly detected are evaluated. For each hypothesis, hypothesized FAP and LAP are determined based on the detected FAP and LAP, a correlation window is determined based on the hypothesized FAP and LAP, and correlation is performed using the correlation window. The correct hypothesis is determined based on correlation results for the two hypotheses. The receiver timing is updated based on the hypothesized FAP and LAP for the correct hypothesis and used for demodulation.

Abstract: A received continuous phase modulation (CPM) signal (which is formed with a set of pulse shaping functions) is approximated as a phase shift keying (PSK) modulated signal (which is formed with just the dominant pulse shaping function having the largest energy). Channel estimation and data detection are performed in accordance with the CPM-to-PSK approximation. A signal power estimate and a noise power estimate are obtained for the received CPM signal and have errors due to the CPM-to-PSK approximation. The difference ? between the energy of the dominant pulse shaping function and the energy of the remaining pulse shaping functions is determined. An approximation error is estimated based on the signal power estimate and the difference ?. A C/I estimate for the received CPM signal is computed based on the signal power estimate, the noise power estimate, and the approximation error estimate.

Abstract: A received continuous phase modulation (CPM) signal (which is formed with a set of pulse shaping functions) is approximated as a phase shift keying (PSK) modulated signal (which is formed with just the dominant pulse shaping function having the largest energy). Channel estimation and data detection are performed in accordance with the CPM-to-PSK approximation. A signal power estimate and a noise power estimate are obtained for the received CPM signal and have errors due to the CPM-to-PSK approximation. The difference ? between the energy of the dominant pulse shaping function and the energy of the remaining pulse shaping functions is determined. An approximation error is estimated based on the signal power estimate and the difference ?. A C/I estimate for the received CPM signal is computed based on the signal power estimate, the noise power estimate, and the approximation error estimate.

Abstract: A “unified” modulator for multiple modulation schemes (e.g., GMSK and 8PSK) is described. The waveform for each modulation scheme is generated based on a set of one or more pulse shaping functions. The waveforms for all supported modulation schemes may be generated based on a composite set of all the different pulse shaping functions. The unified modulator includes a filter for each pulse shaping function in the composite set. To generate the waveform for a selected modulation scheme, the set of one or more filters for this modulation scheme is enabled and all other filters are disabled. The outputs from all enabled filters are summed to generate a modulator output. When switching between modulation schemes, a smooth transition may be obtained by (1) providing a suitable data pattern for each filter to be enabled or disabled and (2) generating symbols for the new modulation scheme with an appropriate initial phase.

Abstract: An efficient method and apparatus for implementing a back-end channel matched filter in a receiver is disclosed. A typical channel matched filter embodiment includes a peak detector for establishing processing synchronization from a despread signal, a channel estimator producing a channel impulse response (CIR) estimate from the despread signal based on the synchronization by the peak detector and a back-end symbol combiner coherently combining dominant multipath components of the despread signal by weights based on the CIR estimate based on the synchronization by the peak detector to generate a decision variable. In a digital spread spectrum implementation, the despread signal operated on by the channel matched filter has been previously been correlated with a spreading sequence replica.