A receiver includes a reception antenna, a reception unit, and a demodulation unit. The reception unit sequentially receives modulated signals resulting from spread spectrum via the reception antenna. The demodulation unit demodulate a first signal received by the reception unit by performing despreading using a short-period spreading code, the first signal including information for identifying a long-period spreading code. The demodulation unit identifies the long-period spreading code on the basis of the information obtained from the first signal. The demodulation unit then demodulates a second signal received by the reception unit after the first signal by performing despreading using the long-period spreading code.

An apparatus and method for use with a shared access communication channel is disclosed. A wireless network device receives signals and recovers data from a first plurality of subscriber units and a second plurality of subscriber units in a time interval. Received signals from the first plurality of subscriber units are distinguishable by having unique pseudo noise (PN) sequence with respect to others of the first plurality of subscriber units. Received signals the second plurality of subscriber units are distinguishable by a unique orthogonal sequence with respect to others of the second plurality of subscriber units. Received signals are distinguished between the first and second plurality of subscriber units based on detection of an orthogonal sequence present only in the received signals from the second plurality of subscriber units.

During optical performance monitoring in low SNR conditions, the detection of pilot data may be more difficult because the detector may mistake noise for the pilot data signal. Systems and methods are disclosed herein that try to address this problem. In one embodiment, a pilot tone detector processes the received signal to determine a maximum correlation peak, and then performs tracking of the correlation peak over time. Unlike the pilot data signal, noise is typically more transient in nature. Therefore, if a correlation peak does not actually correspond to the pilot data signal, but instead corresponds to noise, then the correlation peak typically disappears over time when tracked. A search for a new correlation peak may then be performed. When a correlation peak is determined that actually corresponds to the pilot data signal, then the correlation peak typically remains when tracked.

During optical performance monitoring in low SNR conditions, the detection of pilot data may be more difficult because the detector may mistake noise for the pilot data signal. Systems and methods are disclosed herein that try to address this problem. In one embodiment, a pilot tone detector processes the received signal to determine a maximum correlation peak, and then performs tracking of the correlation peak over time. Unlike the pilot data signal, noise is typically more transient in nature. Therefore, if a correlation peak does not actually correspond to the pilot data signal, but instead corresponds to noise, then the correlation peak typically disappears over time when tracked. A search for a new correlation peak may then be performed. When a correlation peak is determined that actually corresponds to the pilot data signal, then the correlation peak typically remains when tracked.

An apparatus and method for detecting a burst signal. The apparatus includes circuitry that concatenates a predetermined number of samples and transmits the samples to a first programmable memory tap of a predetermined number of programmable memory taps. For each memory tap, a corresponding partial correlation is computed. A normalized sum of all the partial correlations is multiplexed and transmitted to a predetermined number of multipliers. A peak of the burst signal is determined by computing a summation of the complex multiplications of each multiplier, wherein the determined peak corresponds to a start of the burst signal.

An apparatus and method for detecting a burst signal. The apparatus includes circuitry that concatenates a predetermined number of samples and transmits the samples to a first programmable memory tap of a predetermined number of programmable memory taps. For each memory tap, a corresponding partial correlation is computed. A normalized sum of all the partial correlations is multiplexed and transmitted to a predetermined number of multipliers. A peak of the burst signal is determined by computing a summation of the complex multiplications of each multiplier, wherein the determined peak corresponds to a start of the burst signal.

A device and method for estimating a bias in a frequency estimate of a received signal. Circuitry generates a first signal including a number of sample-blocks, wherein the first signal is shifted in frequency from the received signal by a first frequency shift. Based on the first signal, a second signal and a third signal are generated, by shifting a frequency of each of the samples of the first generated signal by a second frequency shift and a third frequency shift, respectively. For each generated signal, a variance for each sample-block is computed. An average variance of the computed sample-block variances is further calculated and a bias of the received signal is determined as one of the first frequency shift, the second frequency shift, and the third frequency shift, corresponding to the generated signal having the smallest calculated average variance.

A device and method for unwrapping phase samples of a burst signal. The device generates a set of vectors including phase samples. A first mean and a first variance of the vectors is computed, and a set of unwrapped phase samples of the burst signal are computed by rotating phase samples of the vector having a smallest first variance by a first rotation amount. The set of vectors is updated based on a new phase sample and a second mean and a second variance of the updated set of vectors is computed. Differences between unwrapped phase samples and a number of phase samples included in the vector having the smallest computed second variance are computed. A next unwrapped phase sample is generated by rotating the new phase sample by a second rotation amount corresponding to a median value of the computed differences.

An apparatus and method for use with a shared access communication channel is disclosed. A wireless network device receives signals and recovers data from a first plurality of subscriber units and a second plurality of subscriber units in a time interval. Received signals from the first plurality of subscriber units are distinguishable by having unique pseudo noise (PN) sequence with respect to others of the first plurality of subscriber units. Received signals the second plurality of subscriber units are distinguishable by a unique orthogonal sequence with respect to others of the second plurality of subscriber units. Received signals are distinguished between the first and second plurality of subscriber units based on detection of an orthogonal sequence present only in the received signals from the second plurality of subscriber units.

A receiver receives signals and noise over a frequency spectrum of a desired received signal. The desired received signal is spread using code division multiple access. The received signals and noise are demodulated to produce a demodulated signal. The demodulated signal is despread using a code uncorrelated with a code associated with the desired received signal. A power level of the despread demodulated signal is measured as an estimate of the noise level of the frequency spectrum.