Performance of DS-CDMA System using Low-Rate Turbo-Hadamard Codes

The aim of this paper is to analyze the performance of low-rate codes in direct sequence code division multiple access (DS-CDMA) systems. While the DS-CDMA systems have been observed to afford capacity gains as compared to TDMA systems, additional benefits in capacity can be obtained through the use of advanced coding techniques before the information data is spread employing the pseudo-noise (PN) sequences. An important approach is to use low- rate codes that can provide both the effective channel coding and spectrum spreading. Low-rate codes could be employed in DS-CDMA networks to accomplish data spreading and provide coding gain as well. One class of such low-rate codes is the Turbo-Hadamard codes which are formed from Hadamard code arrays. In conventional DS-CDMA system, channel coding and spreading is performed separately but in modified system, it is performed simultaneously using low-rate codes. We have used Turbo-Hadamard code as a low-rate code in this system. The performance of the two systems has been evaluated on the basis of SNR VS BER. The simulation result show that modified system performs approximately 0.7dB better than the conventional system