WCDMA HSDPA Network Performance with Receive Diversity and LMMSE Chip Equalization
Timo Nihtilä, Janne Kurjenniemi, Marko Lampinen, Tapani Ristaniemi · 2006
More advanced receiver structures than the conventional single antenna Rake can be used to improve the signal-to-noise (SNR) ratios, which is especially beneficial in order to utilize the high bit rates provided by the HSDPA concept in WCDMA network. In WCDMA system, orthogonal Walsh-Hadamard sequences are used as channelization codes. In frequency-selective fading channels the orthogonality of channelization codes disappears and intra-cell multiple access interference (MAI) arises. In order to mitigate the effect of MAI, a chip-level equalization has shown to be a simple and effective solution. The effectiveness of chip equalization, however, degrades at the cell borders where the inter-cell interference dominates rather than MAI. Dual antenna is a straight-forward solution to mitigate that performance drop. In this paper we consider receivers equipped with dual antenna and linear minimum mean squared error (LMMSE) chip-level equalizers and present an analysts of the expected gains over conventional single and dual antenna rake receivers in realistic situations by using a dynamic WCDMA system-level tool