A consideration on adaptive RAKE receivers for single-user MMSE detection

The constrained MMSE (CMMSE) receiver, which has been developed for flat fading channels (Kim et al., 2000), is applied to each finger of a RAKE receiver in a multipath fading environment. The optimal filter coefficients of the CMMSE receiver in the steady state are derived. The results indicate that the performance of CMMSE receivers can be degraded by interpath interference (IPI) when the channel fade rate is slow. It is shown that the channel estimator employed by the CMMSE receiver can suffer by bias which is caused by IPI. Nevertheless, simulation results demonstrate that the proposed CMMSE RAKE receiver can perform well in multipath fading channels, and outperforms conventional MMSE RAKE receivers