Methods and apparatus for signal processing is disclosed. The methods and apparatus include a first autocorrelator configured to autocorrelate a received signal using a first time delay to produce a first correlation magnitude, a second autocorrelator configured to autocorrelate the received signal using a second time delay different from the first time delay to produce a second correlation magnitude, and a detector configured to determine whether the received signal comprises a packet preamble based on the first and second correlation magnitudes.