| In this paper, we introduce a simple method to improve the performance of threshold-based serial, matched-filter acquisition in packet radio communications. Each packet transmission includes a fixed-length acquisition preamble, and the preamble sequence used in packet transmissions is changed at predetermined times based on a sequence-generation algorithm. Two classes of sequence-generation algorithms are considered: random sequence generation, and preamble sequence generation based on m-sequences. Both are used in conjunction with a sequence-acceptance criterion based on the sidelobe energy of the preamble sequence.
The tradeoff between the acquisition performance and the stringency of the acceptance criterion is examined for each sequence-generation algorithm. The computational burden of the search for an acceptable preamble sequence is also considered. It is shown that the use of the m-sequence generation algorithm results in much poorer acquisition performance for a given percentage of accepted candidate preamble sequences than is predicted using the model of a random sequence generator. Moreover, it is shown that that the tradeoff between acquisition performance and the computation required to find an acceptable preamble sequence is comparable for all of the m-sequence generators considered. Thus within the class of m-sequence generation algorithms, the use of a longer-period m-sequence generator results in a larger number of acceptable preamble sequences for a given level of acquisition performance and sequence-search computation. |