A Joint Algorithm for Carrier Phase and Timing Synchronization in Non-binary LDPC Coded CPM Systems

Abstract

Traditional convolutional coded minimum shift keying (CC-MSK) scheme has the problems of poor reliability and low communication rate under the narrow band and low signal noise ratio (SNR) conditions, a novel scheme of non-binary low density parity check coded continuous phase modulation (LDPC-CPM) is introduced in order to increase reliability and effectiveness. At the same time, the receiver introduces iterative detection mechanism to achieve the compromise between reliability and complexity, and as a key module of the receiver, how to complete synchronization for the signals is a problem worthy of study. This paper proposes a maximum-mean likelihood ratio (MMLR) joint algorithm based on the logarithmic domain, which uses the soft information output by LDPC decoder to complete carrier phase synchronization and timing synchronization simultaneously during a synchronization process. Theoretical research and simulation results show that the proposed algorithm has high effectiveness in large synchronization range and high reliability under low SNR conditions. Compared with serial synchronization, the proposed algorithm can also effectively shorten the synchronization time.