A system includes a differential demodulation module that differentially demodulates modulated signals. A cross-correlation module generates cross-correlation values by cross-correlating states of X symbols in the differentially demodulated signals with corresponding states of X predetermined symbols in each of Y preamble sequences, and determines whether one of the Y preamble sequences is present in the modulated signals, where X and Y are integers greater than 1. The cross-correlation module includes a state detection module that detects the states of the X symbols in the differentially demodulated signals, where each of the X symbols has one of a first state and a second state, and a summing module that generates the cross-correlation values by generating X sums for each of the Y preamble sequences by adding each of the states of the X symbols with the corresponding states of the X predetermined symbols in each of the Y preamble sequences.