Performance Evaluation Of Spread Spectrum System Based On Polyphase Orthogonal Sequence

Mobile communication is in a key period of development. New operation and technology are coming forth. At the same time, Internet is being a true information high way and the wireless operation is increasing. Communication of data and multimedia is developing rapidly. Therefore, the target for third generation mobile communication is spread spectrum communicatin.In the spread spectrum communication system, the spreading sequence is very vital, its capability can impact the whole system's performance. At present the main spreading sequence are duality sequences, it includes m sequence, Gold sequence and M sequence. The research for duality sequences have been abroad and thoroughly. But the duality sequences have some disadvantages that there are few address-codes and the correlation properties can not be improved further. Therefore, the increase of mobile users and higher communication quality can not be satisfied. To change the actuality, a lot of scholars begin to study polyphase sequences. The polyphase sequences construction method of Naoki Suehiro from Japan is typical. According this method, polyphase sequences with more excellent correlation properties can be gotten and more address-code can also be gotten.In this paper, the correlation properties of polyphase sequences are studied thoughtly and a new definition of converting the polyphase orthogonal sequences into a polyphase Spread spectrum signal used in communication system directly is introduced. A modle of communication system using the signal is given, and the simulation of the system is performed. The result shows that the data of receiver remains the character of the transmitter's.Finally, the performance of Spread spectrum communication system in Rayleigh Fading Channel with polyphase orthogal spreading sequences is evaluated: the BER of spread spectrum communication system in Rayleigh Fading Channel is correlative to spread codes by mathematic analysis;the result of simulation shows that the performance of polyphase spreading sequences is better than that of WALSH codes in some ways. It also proves that the feasibility of spectrum communication system with polyphase spreading sequence.