Effectiveness of selection and maximal ratio combining diversity techniques on a DS-CDMA wireless communication system impaired by fading

The effectiveness of different diversity combining techniques in improving the bit error rate (BER) performance of a direct-sequence code-division multiple-access (DS-CDMA) system is presented in this paper. The overall performance of a DS-CDMA system is degraded by multipath fading and additive white Gaussian noise (AWGN). To evaluate the degradation, the expression for the conditional BER, conditioned on a given level of fading is derived and then the unconditional BER is evaluated. This approach is also extended to estimate the BER performance of the system having multiple receiving antennas. The selection method and maximal ratio combining (MRC) method are employed as diversity combining schemes and it is found that both the schemes offer almost the same BER improvement. Moreover, convolutional channel coding is applied in the DS-CDMA system and it is noted to provide more enhancements in the system performance.