On Stability and Radio Capacity in UMTS System

In this paper, we present new results regarding stability and radio capacity in UMTS system. We examine both uplink and downlink cases. We particularly give an upper bound of system stability in the uplink according to activity and inter-to-intracellular interference factors. We show that if the entire system is not very loaded and the activity is low, and if the SINR target is high, the probability that the uplink transmit power exceeds the maximum allowed value is around 5%. As for the downlink, we examine the impact of the users´ distribution in the radio capacity as well as the system stability. Simulation results proved that the downlink radio capacity can be lessened by almost the third according to the users´ distribution in the cell. More importantly, the system can reach the asymptotic capacity in 20% of the cases because of users´ location in the cell.