Bit Error Probability Analysis for Fma2 Downlink

| The wideband code-division multiple access (CDMA) concept (FMA2) developed in the European FRAMES AC090 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 exible changing of data rate, orthogonal Walsh codes are used for channel separation, followed by scrambling code. Optional short scrambling codes can be used if interference suppression is used. In this paper the downlink performance of the FMA2 system using both conventional RAKE and LMMSE-RAKE receivers is studied. According to the numerical results, the performance of the conventional RAKE receivers is insuucient at lowest spreading factors, whereas the the LMMSE-RAKE performs well regardless of the spreading factor. Hence, the nal speciication for ETSI-group proposal should facilitate interference suppression also in the downlink, and not only for the up-link due to relatively bad performance of the conventional RAKE receiver at high data rates.