Analysis of convolutional coded direct sequence spread spectrum CDMA system with a BPSK jamming signal

The number of users in a limited-bandwidth channel can be increased if code division multiple access (CDMA) technique is adopted. This technique has been widely used for wireless communication systems. As the number of users in the system increases, the achieved performance in terms of bit-error-rate (BER) does not increase significantly and is in the acceptable range. Nevertheless, this superior performance of CDMA system is obtained by exploiting much larger bandwidth depending on the chip rate used in the system. This requirement of CDMA system makes it more vulnerable for being interfered by other signals in the same frequency band. Certainly, the performance of the CDMA system is degraded if such situation happened. In this paper, the convolutional code is applied to the CDMA system in order to improve the received signal jammed by a binary phase shift keying (BPSK) signal. The simulation and analysis of such system are given. Convolutional code helps improve the BER of the received CDMA signal in the jamming environment. Up to 4 dB improvement at the BER of 10^-6 can be achieved if the convolutional code is used with the CDMA signal depending on the decoding schemes.