Parameter Estimation Of Higher Order Modulated PCMA Signals

Satellite communications, developed in the 1940s, has become one of the modern communication systems, due to a lot of advantages and excellent properties. PCMA (Paired Carrier Multiple Access) is a multiple access technique used widely in satellite communications. PCMA is able to effectively reduce the transmission bandwidth, and to improve the anti-interception performance. Therefore, PCMA has been paid a close attention in recent years.With the scenario of cooperative receiving PCMA signals, receivers should usually know some information about the interference signal to make interference cancellation and get estimation of the interested signal. However, for non-cooperative reception scenarios, receiver knows little priori information of the received signal. On the other hand, two digital communication signals included in the PCMA signal are almost completely overlapped in time-frequency domain, which brings new challenges to separation or demodulation of PCMA signal.The parameter estimation of PCMA signal is a fundamental basis for separation or demodulation of PCMA signal. Currently in the non-cooperative scenario, some parameter estimation methods have been proposed for low-order modulated PCMA signal, such as BPSK, QPSK modulation, but the existing algorithms have some disadvantages, for example, only one or a small quantity of parameters can be estimated with some prior information of other parameters. With the increasing use of higher order modulation in PCMA satellite communications, the parameter estimation of higher order modulated PCMA signal is significant.This thesis focuses on the parameter estimation algorithm for high-order modulated PCMA signal, under non-cooperative reception scenarios and by utilizing the cyclic statistics. The main work of this thesis is as follows.1. Introduce the cyclostationary of communication signals, and analyze the quantitative relationship between the cyclic statistics of high order modulation PCMA signal and parameters.2. For the PCMA signal with identical baud rate, design the parameter estimation algorithm by using cyclic-spectrum. The estimated parameters include symbol rate, SNR, frequency offset, channel gain, timing error, and phase. Some discussions are made about the relationship between the parameter estimation performance and sample length, signal to noise ratio, signal power ratio, and a low complexity scheme for parameter estimation is also presented.3. For the PCMA signal with different baud rate, the estimation algorithm for symbol rate, channel gain and timing error is given by using second order cyclic-spectrum, and the performance of the proposed algorithm is evaluated by simulations.