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Preamble design and acquisition for CPM

Packet-based communication systems, such as Time Division Multiple Access (TDMA) systems, often employ a preamble sequence to allow coarse estimation of carrier frequency offset, phase offset, and signal delay at the receiver. Successful acquisition of these parameters is of critical importance in synchronization and data demodulation. In this work, a simple preamble structure consisting of a continuous wave (CW) signal followed by a unique, continuous phase modulated (CPM) start-of-message (SOM) sequence is analyzed. Simulation results for frequency, phase and timing error are shown to compare favourably with their respective lower bounds. The required CW and SOM sequence lengths are established by statistical analysis of the effect of residual frequency error on symbol timing performance. In particular, it is shown that an iterative peak search of the SOM crosscorrelation nearly achieves the modified Cramer-Rao bound (MCRB) on symbol timing, making it an attractive option for timing acquisition with minimal overhead. In addition, the proposed preamble format and processing approach are compared to that of the MIL-188-181B standard.