Cross-Layer Modeling of Capacity of UMTS/HSDPA Networks Under Dynamic User Setting

We focus in this paper on the cross-layer modeling of the integration of streaming and elastic flows in the downlink of UMTS/HSDPA systems. Streaming flows are transported over dedicated channels whereas elastic ones shall share the left over capacity according to opportunistic scheduling implemented at the MAC layer. We first study the system at the MAC layer and then make use of these results at the flow level where the system is studied in a dynamic setting. The quasi-stationary assumption makes it possible to obtain a product form expression for the steady-state probabilities of the system. Flow level dynamics are then used at the packet level to investigate TCP performance and quantify the probability of a spurious event, namely timeout. Several performance metrics are then derived and give hints into dimensioning issues of such a system.