Improved frame synchronization for spontaneous packet transmission over frequency-selective radio channels

In digital TDMA-based packet radio channel access schemes operating over slowly time-variant frequency-selective multipath radio channels, it is necessary to achieve fast initial acquisition of receiver synchronization. The authors are concerned with improving the frame sync performance of the ML-algorithm [Fechtel and Meyr, 1993] for feedforward joint frame sync and frequency offset estimation. Emphasis is placed upon improved “non-data-dependent” (NDD) reduced-complexity variants of the ML-estimator. This is achieved by abandoning the test for signal periodicity in favor of a different preamble structure that yields a more pronounced peak of the autocorrelation at the expense of a larger preamble length. The average frame error rate and frequency estimation performance of the new frame/frequency synchronizers is assessed via simulation. For typical examples, the new algorithms are shown to yield frame sync performance gains of several decibels so that asynchronous packet transmission in the lower SNR regions becomes feasible