A composite cyclodespreader and semiblind beamformer for WCDMA

In cellular wideband code-division multiple-access (WCDMA) systems, several transmitted data sequences can be separated because of the unique spreading codes which are designed to be orthogonal. However, cochannel interference and multipath propagation usually destroy this orthogonality at the receiver. We present a composite cyclodespreader that compensates for this distortion by exploiting the cyclostationary property of WCDMA signals, and uses a minimum mean-squareerror criterion to compute a composite despreading code. A semiblind beamformer that utilizes estimated physical channels as an extended training sequence is also employed in the receiver to improve the interference rejection capability in a high interference environment.