Uplink and Downlink Traffic Capacity Performance in WCDMA Systems

The relationship between coverage and capacity in cellular CDMA systems complicates the tasks of capacity estimation and network planning, and requires the use of simulation. The process is usually split into link-level and network-level simulations. The former analyses the aspects related to transmission of the signal between a mobile and a base station. In the latter, user spatial distribution and traffic generation are modelled, each link being characterised by a reduced set of parameters obtained from the previous stage. In WCDMA systems, due to the effects of closed-loop power control, SIR alone does not adequately characterise the radio link from a system point of view (Holma and Toskala, 1), meaning that additional parameters are required to get a complete description, namely average transmit power rise, power headroom, and soft hand-off gains (Sipilä et al., 2, 3). Network-level simulations can be classified into dynamic or static, depending on whether user mobility is explicitly modelled or not, respectively. Static simulations are widely used. In this kind of approach, independent "snapshots'' of the network are generated. Eliminating time-dependence considerably reduces simulation time, while key performance parameters can still be obtained.