Influence of discontinuous transmission and power control on the average SIR and the outage probability of the uplink of CDMA systems

In this paper the impact of the voice activity detection process and the power control system on the average signal-to-interference ratio (SIR) is investigated concerning the uplink of a single cell code division multiple access (CDMA) based mobile communication system. In the literature lower bounds on the average SIR are often employed. Here we show the applicability of such bounds. For this purpose the results obtained from these bounds are compared with results obtained from simulations. Especially, for a few number of subscribers the differences between the lower bound and the exact values are significant. Furthermore, the variance of the SIR is investigated for different parameters. We found out that significant variations occur which affect the outage probability. But, many authors often employ only the average SIR, e.g. for their capacity estimations. However, the variance of the SIR has to be taken into consideration too.