Bit error probability analysis for FRAMES WCDMA downlink receivers

The wide-band code-division multiple-access (WCDMA) concept FMA2 developed in the European Future Radio Wide-Band Multiple-Access Systems (FRAMES) project supports variable-data-rate transmission. The data rate can be altered by changing either the spreading factor or by using multiple spreading codes in parallel. In order to facilitate flexible changing of the data rate, variable-length orthogonal Walsh codes are used for channel separation, followed by the scrambling code. Optional short scrambling codes can be used if interference suppression is used. The downlink performance of the FMA2 system using both the conventional RAKE and LMMSE-RAKE receivers is studied. According to the numerical results, the performance of the conventional RAKE receivers is significantly degraded at the highest data rates, whereas the LMMSE-RAKE performs well in those cases also.