New results on the application of antenna diversity and turbo-codes in a JD-CDMA mobile radio system

The use of coherent receiver antenna diversity (CRAD) in combination with powerful channel coding is advisable in order to obtain sufficient quality in digital mobile radio systems. The application of both CRAD and a novel convolutional code termed the turbo-code to the uplink of a joint detection (JD) code division multiple access (CDMA) mobile radio system is considered. New results on the coded error performance obtained by using the well-known powerful JD techniques zero forcing block decision feedback equalization, minimum mean square error block linear equalization, and minimum mean square error block decision feedback equalization, which were extended to CRAD with maximal-ratio combining, are presented when either one or two receiver antennas are applied. Both bit and frame error rates, respectively, are introduced and compared with formerly published results. The performance enhancement is demonstrated. Furthermore, it is shown that there is a linear dependence between the bit as well as frame error rate and the variance of the log-likelihood ratios generated by the turbo-code decoder. Therefore, the turbo-code decoder can provide information about the current system performance by estimating the variance of the log-likelihood ratios