Patent ID: 6993101

Claim:
A method of determining a start of a transmitted frame at a receiver on a frame-based communications network, the method comprising: providing a preamble format for the transmitted frame wherein a plurality of identical copies of a preamble symbol sequence are transmitted sequentially; filtering a received transmitted frame using filter coefficients matched to the preamble symbol sequence to provide a correlation sequence; computing a squared-magnitude of the correlation sequence; low-pass filtering the squared-magnitude of the correlation sequence to provide a low-pass filtered correlation signal; delaying the low-pass filtered correlation signal to provide a delayed low-pass filtered correlation signal; comparing the delayed low-pass filtered correlation signal with the low-pass filtered correlation signal to provide a correlation difference indicator; comparing the correlation difference indicator with a first fixed predetermined threshold to provide a threshold compared correlation difference indicator; detecting energy of the received transmitted frame and low-pass filtering the energy to provide a low-pass filtered energy signal; comparing the low-pass filtered correlation signal with the low-pass filtered energy signal to provide a correlation peak indicator; comparing the correlation peak indicator with a second fixed predetermined threshold to provide a threshold compared correlation peak indicator; and forming a logical-AND of the threshold compared correlation difference indicator and the threshold compared correlation peak indicator to determine a match/no match comparison indicative of the start of a transmitted frame.