Group-wise successive interference cancellation receiver with adaptive MMSE detection for dual-rate DS-CDMA system

In this paper, group-wise successive interference cancellation (GSIC) receiver with adaptive minimum mean squared error (MMSE) detection and extended GSIC (EGSIC) receiver with adaptive MMSE detection are proposed for dualrate DS-CDMA system. Users are divided into 2 groups for their data rates: high-rate (HR) users and low-rate (LR) users. Initial bit estimates for the HR users are obtained by adaptive MMSE detection. Multiple access interference (MAI) between the HR users is cancelled by parallel interference cancellation (PIC) and updated bit estimates for the HR users are obtained. Then, the estimates for the received signals of the HR users are regenerated using the updated bit estimates and summed up to be subtracted from the received signal. The initial bit estimates for the LR users are obtained by adaptive MMSE detection using the received signal with MAI from the HR users being subtracted. MAI between the LR users is cancelled by PIC and updated bit estimates for the LR users are obtained. It is possible to extend the proposed receiver. In the extended GSIC (EGSIC) receiver with adaptive MMSE detection, an extra stage is added which takes the interference from the LR users to the HR users into account. It is shown that the EGSIC receiver with adaptive MMSE detection achieves significant performance improvement over the MF receiver, EGSIC receiver for dualrate DS-CDMA system in a Rayleigh fading channel.