Adaptive Multicode Transmission Technique in 2.4GHz-band DS-SS Wireless LAN System

摘要

2.4GHz-band wireless communications systems has taking a great attention as they provide a attractive features such as low cost, unlicensed spectral use. However, 2.4GHz-band wireless communications systems are operated in a radio frequency band prepared for Industrial, Scientific and Medical (ISM) apparatus, and then the man-made noise emitted from ISM apparatus is known to be one of the major causes of performance degradation in 2.4GHz-band wireless communications systems. In addition, as same in other wireless communications systems, the performance of 2.4GHz-band wireless communications systems also affected by multipath fading caused by multipath propagation of the transmitted signal, and then throughput performances will be degraded. In order to realize high-speed transmission and high immunity against multipath fading and man-made noise emitted from ISM apparatus, this paper proposes an adaptive multicode transmission technique for a 2.4GHz-band DS-SS Wireless LAN (WLAN) system. In the proposed technique, CDM (Code Division Multiplexing) scheme is employed and the number of simultaneous transmitted symbols (that is, the number of simultaneous employed spectrum-spreading codes) is adap-tively changed according to the propagation condition. Numerical results show that the throughput performance of 2.4GHz-band DS-SS WLAN system is much improved by using proposed adaptive multicode transmission technique.