On system level modelling of UMTS downlink shared channel scheduling

In this paper we discuss the problem of system level modelling of UMTS downlink shared channel (DSCH). We present a novel approach for system level modelling of the shared chan-nel scheduling, which is based on the load control framework as presented in [2]. The new model uses the ranking criterion of the scheduler to model its long-term behaviour, which is provided as the distribution of the mean data rates the scheduler offers. Two major classes of schedulers are investigated, throughput fair, which tries to equalise the data rates between each user, and proportional fair, which assigns an equal amount of resources to each subscriber. The statistical models are verified by means of system level simulations, which are performed with a time-granularity of 667 µs. We show that the presented models fit very well to the simulation results for a regular scenario with 36 cells and 504 users.