Analysis of Multiple Access Interference in Asynchronous Direct Sequence Spread Spectrum Communication System Using Gold Sequence
|School||Harbin Institute of Technology|
|Course||Information and Communication Engineering|
|Keywords||DS-CDMA Gold sequence correlation characteristic multiple access interference|
Direct Sequence CDMA system is the widest application in spread spectrum communication system at present. It is a self-interference system because each user is interference to other users, and multiple access interference (MAI) is the main interference factor in the system. So the characteristic and quantity of spread spectrum address code has great influence and restriction to the system performance and capability improvement. Most of the researches are under the condition that all the code rates are the same. However, the rates between users are not quite the same practically. At this time, the correlation characteristic is different, so is MAI. The analysis of MAI in asynchronous direct sequence spread spectrum system using Gold sequence is studied in this paper.Firstly, the spread spectrum system and direct sequence CDMA system are briefly introduced. The definition and characteristic of m sequence are discussed, besides, the generation method and correlation characteristic of Gold sequence are analyzed detailedly from theoretical and practical aspect.Based on the above work, the analysis of MAI in synchronous Direct Sequence CDMA system using Gold sequence is studied, and method of estimating asynchronous system interference is given according to it. Then the basic blue print of system simulation is brought out. On the basis of analyzing generating ways and correlation performance of optimum m sequence pairs and Gold sequence, the computer realization of how to get them with Matlab is presented, and the program flow chart are provided. A mass of data and figures are got by Matlab programs. After making use of them to analyse the correlation characteristic of Gold sequence and MAI in the system, some pertinent useful conclusions are brought forward.Overall, after a lot of study on spread spectrum communication system theory and sufficient understanding, this project focuses on application research and simulation, and gets several achievements. The conclusion can be used for reference when project is involved in the field for the future.