WCDMA multi-cell link-level performance

This paper presents a multi-cell simulation approach with which the impact of selected link-level aspects on cellular system performance can be investigated. The investigations are carried out for downlink dedicated physical channels (DL-DPCH) of third-generation wideband CDMA (3G WCDMA), specified by the 3GPP standardization body. The simulator incorporates user equipment (UE) that suffers from intra-cell interference of the connected base station (BS) as well as inter-cell interference originating from explicitly, i.e. chip-exact, modeled surrounding BSs. The employed multi-cell environment, based on a radio geometry concept; is described. Coded error performance is shown for various mobile radio channel scenarios, radio geometries and different models for the interference. The question whether inter-cell interference of surrounding BSs can be modeled alternatively by additive white Gaussian noise (AWGN) is addressed. It turns out that in all cases the chip-exact modelling of adjacent BSs is necessary in order to obtain realistic performance results. This holds especially the more the UE moves towards the cell border and beyond. Comparisons with simulations employing the AWGN model for inter-cell interference show that those results are too optimistic at low speeds. Moreover, it is shown that a performance analysis based solely on uncoded (raw) bit error rate is not sufficient, but must be complemented by decoded bit and block error rate figures.