Performance Improvement of CDMA Wireless Sensor Networks in Low SNR Channels Based on Raptor Codes

Abstract

Some kinds of communication systems work in very low signal to noise power ratio (SNR) environments. For these systems to function reliably, certain techniques and methodologies have to be used to mitigate the degrading effects of the channel.The channel coding method is the key element in most low SNR communication systems with emphasis on the Code Division Multiple Access (CDMA) as a recommended transmission technique in these channels. To enhance the system capacity of the CDMA scheme and reach to unprecedented ranges of low SNR values in systems like the Wireless Sensor Network (WSN), this paper suggests a technique for combining CDMA with certain types of channel coding algorithms such as the Raptor codes. The Raptor channel encoding technique has shown an improved performance for the CDMA system when using BPSK digital modulation in AWGNchannels. It has achieved a low bit error rate in the range of 10-6 at Eb/No value of -2 dB and 10-7 at Eb/No value of -3 dB for code rates 1/2 and 1/3 resprctively. The Raptor-coded CDMA scheme showing an improvement of about 6 dB when compared with some other channel coding methods used with the CDMA system for the same BER.