Research On Application Of Sequence Pairs In DS-CDMA Communication System

Spread spectrum communication modulate the information data by spreading sequence, and then transform the modulated signal by a much more wider bandwidth. At the receiver, after demodulation and correlation processing using the spreading sequence, the transmitted information data can be get back exactly. On the basis of this, CDMA communication system takes advantage of orthogonal spreading sequences to differentiate users. But the orthogonality of spreading sequences is not good enough, which leads to MAI, and multiuser detection can weaken or eliminate MAI effectively. At present the widely-used spreading sequence include m sequence, Gold sequence, etc. But these spreading sequence exist some given length, so we have to cut short these spreading sequences. While sequence pairs exist at much more length, it can make up the shortage of the spreading sequences at present. In addition, the number of existing sequence is limited, so sequence pairs can be used as an effective supplement.Sequence pairs, as a couple of different sequences satisfying certain given conditions, rank in a new perfect signal. If sequence pairs can be applied to the existing communication system, which is not only overcome the shortcomings of existing sequence, but establish a new concept and idea in signal processing. So analysis the performance of the system is very important to the actual application of sequence pairs.In this paper, the sequence pairs satisfying the certain given conditions is applied to spread spectrum communication system, through theoretical analysis and experimental simulation, the feasibility of sequence pairs being applied to spread spectrum system is proved. Accordingly, sequence pairs is first introduced in CDMA communication system, the BER performance of which isstudied by experimental simulation and afterwards is compared with that of CDMA system with Gold sequence. The result shows that BER performance of the two systems is close to each other. Finally, sequence pairs are applied to CDMA system which uses MOE and LS-CMA blind multiuser detection algorithms, simulation results show that both SINR and BER of the system can be improved obviously.