Blind Estimation Of Time-parameters And SNR For OFDM Signal

For the rapid development and widely applications in the civil and military of OFDM(Orthogonal Frequency Division Multiplexing) technology, OFDM signal’s non-cooperativereception study is of great significance. Based on the non-cooperative communication system as thebackground, this paper carries out research on blind estimation methods of time-parameters and SNR(Signal to Noise Ratio) for OFDM signal. The main contents are as follows:Blind estimations of the time-parameters for OFDM signal are firstly studied in this paper,which include the over-sampling ratio and system parameters of OFDM. Firstly, through the analysisof OFDM signal’ spectrum characteristics in the condition of over-sampled, this chapter proposed amodified blind estimation method of over-sampling factor; and then through the analysis of OFDMsignal’s cyclostationarity characteristics, combined the time-domain correlation algorithm with thecyclic autocorrelation algorithm, this chapter proposed a novel method to estimate the symbol periodbased on cyclic autocorrelation with the time-domain average; finally, according to the characteristicof the useful data length equal to the IFFT transform points, the over-sampling ratio is correctedbased on the estimated over-sampling rate and the system parameters of OFDM signal.In addition, this paper also makes some research on SNR blind estimation for OFDM signal,and proposes two modified SNR blind estimation method. Firstly, the paper analyzes the derivationof autocorrelation function expression for OFDM signal under the condition of multi-path channel;and then according the characteristic of autocorrelation function, the chapter proposes a novel blindcoarse estimation method for multi-path channel order, and use the autocorrelation values withoutinter symbol interference to estimate signal power; finally, through the analysis of Gausscharacteristics of OFDM signal, the paper proposes a novel SNR blind estimation method based onthe cyclic prefix propertied, which does not need the accurate timing synchronization and solve theproblem that the existing estimation methods all need precise timing and frequency synchronization.Some simulations are implemented to verify the effectiveness of the proposed methods in thispaper. The simulation results show that all of the proposed methods can obtain good performance inthe conditions of low SNR and multi-path, and that compared with the existing methods, theproposed methods achieve certain promotions in the same simulation conditions.