Chip rate and symbol rate MMSE functionalities for CDMA receivers

An LMMSE-variant chip equalizer and an MMSE symbol estimator are discussed for the UMTS FDD mode. Since the scrambler is aperiodic in the downlink, the LMMSE (linear MMSE) receiver has to be adapted at the chip rate. By modeling the scrambler as a stationary random sequence, however, a max-SINR equalizer-correlator structure, which may be adapted at the symbol rate, is obtained from the LMMSE receiver formulation. Linear symbol estimates at the correlator outputs can be refined by MMSE functionalities. A composite performance analysis of the discussed (L)MMSE structures is done and its applicability on estimating the interfering user symbols is discussed.