Novel Preamble for Accurate Synchronization of Frequency Hopped OFDM Links

Frequency Hopping(FH) is an effective way to ensure resilience to jamming and eavesdropping. We consider an ultra-fast FH system where a contiguous set of subcarriers of an OFDM block which hold data are altered periodically based on a random code pattern. Since only a small set of subcarriers of the OFDM symbol are used in any one hop, receiver synchronization for timing and frequency is difficult since the time-domain auto-correlation properties degrade. In this paper, we compare existing preamble and processing methods using auto-correlation for synchronization. We then propose a new preamble with a two-step improved timing estimate. Simulation and results are presented which show the effectiveness of the proposed preamble and processing scheme, especially at low Signal-to-Noise Ratios as evident from the plots where a 3-dB improvement in the probability of detection at -6 dB SNR is seen.