Research On The Parameters Estimation Of Non-cooperated Multicarrier Reception

Multi-carrier modulation has been widely used in civil high-speed broadband communications and military tactical communications with its efficient bandwidth utilization, ambition performance of transmittability under multipath channel and simple system implementation. It has an important theoretical significance as well as greatest need to analysis this kind of signals in both civil and military communications as well as extracts the modulation parameters. Based on the characteristics of the non-cooperative reception, this thesis deal with the blind parameters estimation of multicarrier modulation signals, the main work and contributions could be listed as follows:1. Based on the analysis of implementation method and modulation principle of Orthogonal Frequency Division Multiplexing(OFDM) and Offset Quadrature Amplitude Modulation(OQAM), this thesis establishes the blind analysis mathematical model which combining with the characteristics of the signal analysis in the non-cooperative receiving. Then points out the particularity of its analysis.2. Analyzes the spectrum line feature of cyclostationary of OFDM signals, deduces the relationship between oversampling ratio and the square spectrum line. An algorithm was put forward for the problem of poor performance of traditional oversampling ratio estimators; then analysis the cyclic cumulants of OFDM signals, combining with the oversampling ratio, an algorithm of joint blind parameters estimation of OFDM signals was put forward which could estimate the symbol period, sequence period, subcarrier numbers and cyclic-prefix length. The algorithm can achieves a good accuracy and needs low priori information, which is more suitable for non-cooperative reception.3. For the problem of high complexity and poor adaptability of traditional blind signal to noise ratio(SNR) estimators for OFDM signals, firstly analyzes the characteristics of symbol of OFDM signals, expands the testing region of correlation of cycle padding correlation and get a signature sequence, introduce the wavelet noise reduction to improve the robustness under multipath channel. Deduces the relationship between SNR and the extreme value of the sequence and apply it to estimate SNR. Simulation results show that the algorithm can estimate the SNR of ZP-OFDM signals accurately as well as CP-OFDM signals, and gain better adaptability and lower complexity in the estimation of CP-OFDM signals.4. Analyzes and deduces the second-order cyclic cumulants and spectral correlation function of the OQAM signals, analysis these characteristics of modulation parameters. Aiming at the problem of large computational complexity of the traditional parameter estimators, an algorithm based on cyclic cumulants and oversampling rate is put forward. Experiment results shown that the algorithm can reduce the complexity without significant performance loss of the blind demodulation and data recovery of the back-end.5. The system structure and function module of a comprehensive MCM signal analysis system has been preliminary implemented, then test the performance. Experimental testing results validate that the relevant algorithms lead to an efficient performance in the parameters estimation of OFDM and OQAM signals. The overall performance of the system could achieved the desired effect.