An accurate heuristic approach for UMTS RLC delay statistics evaluation

This work is a preliminary investigation on the effect of a controlled amount of retransmission on the residual higher layer packet error probability in a UMTS system. In this paper, we first characterize the delivery delay statistics regarding link layer service data units (SDUs) considering in order delivery. After this we propose a very simple heuristic able to approximate such statistics with great accuracy. This heuristic is well suited to being used in energy limited mobile terminals. In the final part of the paper, we investigate how this heuristic can be effectively used at the mobile terminal to dynamically choose the right amount of link layer retransmissions while respecting the delay constraints imposed on the higher layer flows. We quantitatively evaluate the maximum achievable gain when the optimum number of retransmissions is selected.