Patent ID: 7555090

Claim:
A communications channel detector for determining the availability of a desired type of communications channel in a communication system having at least one communications channel, the communications channels including data streams comprising a plurality of data symbols, the channel detector comprising: a phase identifier configured to provide a plurality “n” of phase measurements for each of a plurality of consecutive ones of the data symbols comprising one of the communications channels, the n phase measurements for any one of the data symbols respectively corresponding to n timing offsets from a center of the data symbol; a phase comparator coupled to the phase identifier and configured to determine the differences between the phase measurements for consecutive data symbols, each of the differences corresponding to one of the n timing offsets and determined between phase measurements corresponding to the one of the n timing offsets, to provide a plurality of phase differences for each timing offset; and a phase correlator coupled to the phase comparator and configured to determine whether or not the plurality of phase differences for at least one of the timing offsets exhibit a predetermined phase difference profile, wherein the predetermined phase difference profile comprises a predetermined histogram of expected phase differences for the desired type of communications channel; wherein the phase identifier is configured to measure the phase of each data symbol at a number “m” of the n timing offsets, and to estimate the phase of each data symbol at n-m of the n timing offsets, to thereby provide m measured phase measurements and n-m estimated phase measurements as the n phase measurements; wherein the phase comparator is configured to form a histogram of the plurality of phase differences for each timing offset, to provide n histograms; and the phase correlator is configured to correlate each of the n histograms with the predetermined histogram; and further wherein the metric for each of the n histograms is calculated by computing the inner product of the predetermined phase difference profile and the histogram for each of a plurality of relative positions of the predetermined phase difference profile and the histogram, dividing each inner product by the number of phase differences used to form the histogram, and selecting the maximum of the resultant divided inner products as the metric for the histogram.