A joint pilot and demodulation soft information carrier synchronization for SOQPSK signals

To solve the carrier recovery problem with large frequency offset in short burst communication systems using shaped-offset quadrature phase shift keying(SOQPSK), a joint pilot and demodulation soft information carrier synchronization algorithm is proposed. First, a coarse estimation based on a few short pilot sequence is carried out. Then, further fine search is done around the coarse estimation region. The precise carrier synchronization parameters are obtained based on the maximum-mean-square soft output of SOQPSK. Simulation results show that at E_b/N₀ ≥ 0dB the proposed algorithm can eliminate large carrier offsets as much as half the data rate, resist phase confusion and achieve effective carrier synchronization with only 30 pilot bits and low computation complexity, achieving a BER performance which is very near that of the optimal coherent demodulation. When BER is in the region of 10^-2~10^-5, SNR degradation is within 0.3dB.