Performance of shared and dedicated resources in WCDMA

For data transmission WCDMA offers dedicated transport channels (DCH) and common transport channels, i.e. random access channels (RACH) and forward access channels (FACH). Both types of transport channels have different characteristics in terms of transmission performance and radio resource usage. In this paper these characteristics are described and a simulation model for the performance evaluation is presented. The effect of some parameters influencing the performance and efficiency of the different transport channel types is discussed, e.g. channel configuration, traffic load and traffic characteristics. It is demonstrated that common transport channels provide better performance than dedicated channels for a low traffic load of bursty traffic. For low data volumes they are also more resource efficient. However for an increasing traffic load dedicated channels provide a better service quality and radio resource utilisation.