Performance of high bit rates with WCDMA over multipath channels

IMT-2000 systems are required to provide bit rates up to 2 Mbps with high spectrum efficiency. In this paper the performance of 512 kbps-2 Mbps with UTRA wideband CDMA in multipath channels is evaluated. The evaluation is based on the link level simulations with a RAKE receiver in different multipath profiles. The performance of high bit rates in the air interface is affected by the multipath propagation. The multipath propagation gives a diversity gain but also causes inter-path interference. The effect of inter-path interference is analyzed and the possible gains from advanced receiver structures in cancelling inter-path interference are evaluated. Also, the multipath diversity gain is studied for high bit rates. The results of this paper show that inter-path interference can cause a degradation of about 2 dB for 2 Mbps transmission in 2-path Rayleigh fading channel if an ordinary RAKE receiver is used. The more multipath components are present, the higher the degradation. It is also shown that the required transmission power is lower in multipath channels than in a 1-path channel because the multipath diversity gain is typically larger than the loss due to the inter-path interference.