A method of determining a collision between two or more transmitting stations
at
one of the transmitting stations on a frame-based communications network. A transmitted
frame header includes a cyclic preamble wherein identical copies of a preamble
symbol sequence are transmitted sequentially. A collision is declared if an estimate
of error power in second and third copies of the preamble minus an estimate of
error power in third and fourth copies of the preamble exceeds a first threshold,
or a maximum value of the norm of each term of a source field error vector minus
a greater of the estimate of the error power in the second and third copies of
the cyclic preamble and the estimate of the error power in the third and fourth
copies of the preamble exceeds a second threshold.
