Joint Carrier Recovery and Turbo Decoding Method for TDMA Burst MODEM Under Very Low SNRs

In this paper, we propose the enhanced carrier recovery algorithm for very low SNR environment. Especially, in order to increase an accuracy of residual frequency and phase offset estimation under very low SNR with constraints of power-limited communication system, it is achieved by comparing the phases between soft decision outputs of code symbols and the channel symbols at the each turbo decoding iteration. As the number of iteration increases, residual freq. and phase offset are compensated and thus the reliability of the soft decision output at next iteration is increased. In consequence, the complementary cooperation between iteration decoding and carrier recovery improves the final coded BER performance. The proposed techniques can fulfil the stringent up-link link budgets at Ka band by operating at very low SNR