Training Symbol Based Coarse Timing Synchronization in OFDM Systems

In orthogonal frequency division multiplexing (OFDM) systems, coarse frame timing can be acquired from one or more training symbols preceding every OFDM burst. The existing literature studied the case where there was only one training symbol consisting of identical segments. We generalize the timing synchronization methods to take advantage of multiple training symbols and only require the segments to be highly correlated but not necessarily identical. We construct a series of component timing metrics, one for each pair of the highly correlated segments, and combine them linearly to minimize the false alarm probability while keeping the asymptotic missed detection probability to the same level as other techniques. The OFDM data symbols in a downlink burst can have different power levels to reach the users at different distances. We take that into account and yield more realistic results than those in existing literature which only considered the equal power case. The performance of the proposed method is analyzed in three scenarios generalized from the IEEE 802.11 and IEEE 802.16 standards. Numerical results are presented to confirm the robustness of the proposed method in various channel conditions.