Precise Estimation of WCDMA Downlink Pole Capacity in Multipath Propagation Channel by Monte Carlo Method

There are two parameters ought to be evaluated in estimating downlink pole capacity of the WCDMA radio network. One is the downlink interference ratio, which can be precisely calculated with the link quality equation for all covered cells. Another is the downlink orthogonality factor, which is usually unknown for different multipath propagation channels in various clutter environments. When radio signal propagates in multipath channel, the orthogonality is destroyed and varies within 0.2 ~ 0.9. This gives a quite large range in estimating the cell capacity. Once the RMS delay spread of the multipath propagation channel has been measured, we can simulate the local multipath propagation channel by Monte-Carlo method for radio signals concatenating short orthogonal spreading code and long scrambling PN code to propagate. Then, in this paper, we propose a new algorithm to calculate the orthogonality factor for different spreading codes and derive a linear equation for the orthogonality factor with respect to the log-rate of data bit. With that equation, an exact solution of the downlink pole capacity for an isolated cell or a cluster of cells can be estimated when loading distribution for all services are assigned and the downlink interference ratio is calculated as well.