Study on the Diversity Method to Improve the Performance of the CDMA System in the Mobile Wireless Channel

This study proposes a new diversity algorithm to improve the signal-to-noise ratio. In the wireless channel, if fading occurs due to the multipaths, the performance of the system is apparently reduced. One of the methods to reduce fadings like this is the diversity method, and this study aims to improve the performance of the system by proposing a new diversity algorithm. This study applied rake receiver, and normalized the wireless channel from the Nakagami fading channel to the Rayleigh fading channel, which set the fading index as 1, because of the multipaths. It applied QPSK and OQPSK modulation methods and applied the convolutional codes, where the code rate is 1/2 and 1/3 and the constraint length is 9, and the turbo code where the constraint length is 4. Under these conditions, this study compared and analyzed the average error probability of direct spread multiple access system. The diversity algorithm proposed in this paper could be applied to the mobile communication and other wireless multimedia communications that require high quality and high reliability.