The Key Technology For The Wireless Mobile Communication System With OFDM

Facing the object of the next generation mobile communication system, Orthogonal Frequency Division Multiple (OFDM) against Code Division Multiplex Access (CDMA) has its distinct superiority. However, OFDM is sensitive to synchronization error and channel estimation error and it has the weakness of the high Peak-to-Average Power Ratio (PAPR) of the transmitted signal. To these weaknesses, scholars have done numerous researches and gained great achievements. But as far as the new object about the next generation mobile communication system is concerned, the question about how to realize the synchronization and channel estimation and to reduce PAPR in the transmitter is under the way. Against these problems, the thesis has mainly discussed the three key technologies about synchronization and channel estimation and reducing PAPR for the OFDM systems in the receiver.Firstly, the thesis has proposed four kinds of timing synchronization and frequency synchronization algorithms using series-wound Pseudo Noise (PN) sequence. The first two synchronization algorithms employing Barker code and PN sequence. The rest two algorithms employing PN sequence devised by the different design methods in the frequency domain of the receiver. Then, the algorithms against the conventional algorithms gained further advantage relations in the time domain of transmitter to achieve the synchronization signal and to deduce the synchronization algorithms by theories. It's proved by simulation that the synchronization performances of the four algorithms are superior to those of the conventional ones for AWGN channel and multi-path fading channel under the high speed mobile environment.Secondly, the thesis has proposed the three frame synchronization algorithms employing the superimposing PN sequence. The main difference of three algorithms against the conventional algorithms is that the proposed superimposing PN sequence is distributed far weaker power than it does in the convention, which the influence over the signal and the system performance can be ignored. The first kind of the frame synchronization algorithm employs the correlation of the long PN sequence and the redundancy of the guard interval to produce the synchronization signal. The second kind of the frame synchronization algorithm employs the re-correlation of the long PN sequence and the redundancy of the guard interval to produce the synchronization signal under the multi-path fading channel. The three kinds of the frame synchronization algorithm show that their synchronization performances are superior. Especially the computation complexity of the third is not only the lowest, but its performance is the best.Thirdly, the thesis has proposed the Linear Minimum Mean Square Error (LMMSE) channel estimation algorithm using the superimposing PN sequence with less computation complexity. It's proved that this algorithm doesn't need the apriori information and doesn't occupy the precious band-wideth. Furthermore, its computation complexity is lower than that of Least Square (LS) and the performance of the proposed algorithm is better than that of LS in the lower Signal-to-Noise Ratio (SNR). Furthermore,the thesis has proposed the power distribution rule of the superimposing PN sequence that will play an important role in the synchronization and channel estimation techniques employing the superimposing PN sequence.Lastly, the thesis has proposed the compandor algorithm to reduce PAPR. This algorithm is a pre-distortion method of numerical value transfer and is deduced by the theories. It's proved that the computation complexity of the algorithm to reduce PAPR...