The Research Of Modulation And Demodulation Method And Communication Mode 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 communication.In spread spectrum communication, the main address codes are duality sequences. 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 require for 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 got and more address-codes can also be got.In this paper, the correlation properties of polyphase sequences are studied thoroughly and an new method of modulation and demodulation is given. The capacity of auto-correlation and anti-MAI for this method is analysed. Two communication modes for CDMA based on polyphase complete complementary sequences are given. The conclusion that this system can overcome the MAI and multipath impact in mobile communication is given.The properties of auto-correlation for polyphase orthogonal sequences are very ideal, but its cross-correlation properties are not good when the phase number is low. Although the number of independent address can satisfy the request with the increase of phase, the searching time is too long. In this paper, the shift sequences of polyphase orthogonal sequences are distributed to different user and the ideal auto-correlation properties are utilized for CDMA communication.Finally, in this paper some problems for theory and application of polyphase orthogonal sequences are pointed out. The main direction of research for polyphase orthogonal sequences is given.