Effects of simultaneous circuit and packet switched voice traffic on total capacity.

Introducing packet switched (PS) voice in cellular systems is often discussed in terms of circuit switched (CS) voice replacement. In this study, we investigate the differences in downlink resource consumption or capacity in a WCDMA system with both CS and PS voice traffic on the same 5 MHz carrier. The PS traffic is gradually increased, representing a migration from CS to a PS only scenario. The study comprises both theoretical calculations and system simulations of downlink voice traffic. The results show that gradually introducing PS voice traffic on the same carrier as CS speech gives equally good or better voice capacity without compromising the QoS requirements. Further on, introducing PS voice on the same carrier can be done in a very flexible way. The CS admission control thresholds can control the power usage for CS, and PS voice can thereafter use the remaining base station power. This means that the CS admission control can decide the ratio of CS and PS voice users, and increase the PS ratio gradually as the PS voice traffic becomes more common