Synchronization Algorithms For Continuous Phase Modulation

As the deep space communication, Monitoring and control communication systems require higher bandwidth efficiency and code rate, continuous phase modulation system has been widespread concerned in the field of satellite communication and mobile communication because of its characteristics of constant envelope and high bandwidth efficiency. Nevertheless, because of its high complexity receiver and synchronization problems, the CPM system cannot get more extensive application. The recovery of frequency, phase and timing has been studied and improved in this paper. The main contents of this paper are as follows.1. Three carrier synchronization algorithms are discussed in this paper. The multiplying delay estimation algorithm has a low computational complexity, a wide range of frequency offset estimation and a low estimation accuracy. This algorithm is suitable for a coarse estimation for frequency. The maximum square soft output algorithm can accurately estimate the frequency offset, which is close to the performance limits of synchronization, and that the algorithm can achieve ideal error performance. The frequency estimation algorithm that is based on FFT is a data aided algorithm which needs pilot training sequence. Its estimation accuracy increases with the length of the pilot. On the basis of these algorithms, a joint pilot and demodulation soft output assisted carrier synchronization algorithm is proposed in this paper. It combines the frequency estimation algorithm based on FFT and the maximum square soft output algorithm, in which way it reduces the length of pilot and the search range of frequency. The algorithm firstly estimate the frequency offset coarsely, then it fine searches around the value to achieve a fine frequency offset estimation value. In this way, it realizes the fine estimation of large frequency offset.2. A joint timing and phase estimation algorithm is studied in this paper. It can track the time delay and phase offset at the same time. Improving the filters with Laurent decomposition can reduce the complexity of the filter as well as obtain accurate timing and phase estimation value. On the basis of this algorithm, a joint frequency offset, timing and phase estimation solution is present in this paper. It combines the algorithm based on FFT and joint timing and phase estimation algorithm. It takes the advantage of the joint timing and phase estimation algorithm’s property that it can estimate timing and phase information within small frequency offset.Based on the study of several frequency offset, timing and phase estimation algorithms, we analyze the scope and application of these algorithms. This paper provides a fine estimation solution for large frequency offset. Simulation results show that this method reduces the pilot length and the search range. It can obtain accurate estimation value with low complexity. It also proposes a joint frequency offset, timing and phase estimation algorithm. The simulation results show that this method has a good BER performance and high estimation accuracy.