Performance of MIMO Rake receivers in WCDMA systems

The rake receiver is investigated for spatial multiplexing (SM) in wide-band code-division multiple access systems. In general, the SM increases the data rate and the diversity order as well. The appropriate maximum likelihood detector is derived in this paper and it is shown that the diversity order is related to the product of the numbers of receive antennas and taps. With realistic numbers similar diversity orders may be achieved also with reduced complexity detection schemes. Finally, a standard-conformal scrambling technique is proposed to enhance the performance and to equalize it among the full set of orthogonal variable spreading factor (OVSF) sequences used in the third generation cellular system.