Research On The Performance Of Communication System Based On Multi-code CDMA

Wireless communication technology and wireless access technology play a very important role in modern communications, with the development of wireless technology, the type of wireless communication services has become even more, greater communication capabilities and more flexible rate adaptive approaches are needed. Multi-code CDMA (Mc-CDMA) technology, is widely used as a multi-rate transmission technology today, with its advantage of multiple access capability and signal hidden ability.This paper summarizes the classification and developments of wireless communication technologies, introduces DS-SS technologies which play an important role in Multi-code CDMA System, and then discusses the principles of spreading spectrum and the characteristics of the spreading code. On this basis, the paper focuses on the research of Mc-CDMA system, especially the performance of spreading spectrum in Mc-CDMA system in detail. The paper describes the Mc-CDMA system in detail, and introduces the transmission model, the channel model, and the receiver model. Data transmission, error performance and main factors affecting the performance of spreading spectrum in Mc-CDMA are also analyzed and discussed. Meanwhile, with MATLAB software, this paper builds a DS-SS Multi-code System using the m sequence and the OVSF sequence. By changing parameters such as spreading code types, spreading factor, the number of active users and the number of code channels assigned to each user, the software simulates the system performance under Gaussian noise and multipath conditions and gets the bit error rate. Thus we get corresponding conclusions.In the end, the paper proposed the concept of tolerance code channel and the adaptive scheme of Mc-CDMA system. The scheme was validated in MATLAB.