Design of Distributed Unique Words for Enhanced Frame Synchronization.

A novel approach is introduced for the design of a unique word (UW) for frame synchronization in time division multiplexing/time division multiple access (TDM/TDMA) systems. In particular, the UW symbols are distributed in each frame in a specific pattern in order to optimize the UW autocorrelation properties. The distribution patterns are scalable, since they preserve their autocorrelation properties under truncation. The resulting frame structure enables the use of several types of UWs, including the silent-UW (SUW) and the unit-UW (UUW), that are novel approaches for which the optimal Bayes detector is derived. An analytical performance characterization is presented along with comparisons with state-of-the-art alternatives. We show that SUW can significantly outperform the classic UW in the presence of frequency offsets or whenever data interference is the main impairment to cope with, i.e. at moderate to high signal to noise ratios. Interestingly, this performance improvement comes with the further advantage of a considerable complexity reduction. Hence UUW is shown to provide both performance improvement and complexity reduction.