Abstract: "UMTS capacity simulation study"

The purpose of this report is to investigate the performance, measured in terms of Key Performance Indicators (KPIs) of a UMTS radio network (UTRAN) under different traffic and mobility scenarios (i.e. homogeneously/ non homogeneously distributed traffic, mobile/non-mobile traffic) and develop some general guidelines for dimensioning the UMTS network optimally.

In this work, simulations are performed using the Wines simulator, which is a dynamic simulator that models all the radio-resource management functionality of the UTRAN. Two main series of experiments have been performed. In the first series simulations have been performed on an analysis area defined in common agreement with international colleagues at Vodafone. The distribution of the traffic in this simulation scenario is homogeneous and the main purpose is to find capacity figures when increasing the traffic density of one of the four possible defined services (WWW, FTP, voice and video-call) and also with a given traffic mix involving all services together. Two mobility profiles are used (pedestrian and vehicular).

In the second series of experiments, a more realistic scenario, based on detailed geographical characteristics relevant for signal propagation, and traffic densities based on traffic maps, has been simulated. The purpose was to analyze the possible differences in capacity between the “ideal” model and the more “realistic” model.

For the single-service scenario analysis, circuit-switched services (speech and video-call), it can be observed that the capacity is mainly uplink-limited. The corresponding results for the packet-switched services (FTP, WEB) have shown that capacity is mostly downlink-limited, as it was expected due to the more asymmetrical data rates in the downlink compared to the uplink for both services.

For the service mix analysis in both scenarios (homogeneous and non homogeneous) it was found that the capacity is mostly downlink-limited (i.e. the downlink power target level is exceeded before the uplink load target level).

In terms of the power-rule usage, no significant differences between the two analyzed rules were found, provided that the downlink path loss between the Node B connector and the antenna is below 4 dB in all the sites.

Finally, for the mobility study in both scenarios (homogeneous, non homogeneous) the theoretically expected behavior was confirmed.