A novel blind adaptive algorithm for channel equalization in WCDMA downlink

In the downlink of the wideband code division multiple-access (WCDMA) system users are separated by the means of orthogonal variable spreading factor (OVSF) codes. The orthogonality of the users is lost in multipath channels causing multiple access interference in the system. To suppress the interference in the downlink, it has been proposed to utilize linear channel equalization to partially restore the orthogonality of the users' spreading codes. The well-known LMMSE equalizer, however, may be computationally too involved for practical applications. This is why adaptive solutions am preferred. In this paper, a novel adaptive approach for linear estimation and equalization is presented. Contrary to many other techniques, the applied blind adaptive algorithm can be used without changes also in multi antenna transmission systems, such as space-time coded transmission, and with long scrambling codes. The performance of the new adaptive LMMSE receiver is evaluated in a complete UTRA FDD downlink simulator and is compared to conventional RAKE receiver.