Low rate voice bearers in the GSM/EDGE radio access network

With the use of the 8PSK modulation available in the GSM/EDGE radio access network (GERAN), adaptive multirate (AMR) voice can be supported with good speech quality using half-rate (HR) or even quarter-rate (QR) bearers. In this paper channel coding schemes for 8PSK HR are evaluated in terms of quality and capacity. System level simulations show that a capacity gain of 20% can be obtained with HR bearers as compared to the default full-rate bearers in a 1/3 reuse deployment. It is also shown that the introduction of QR bearers, together with an ideal adaptation mechanism, could lead to a capacity gain of up to about 90% in a 4/12 reuse pattern. However, dynamic system level simulations indicate that both measurement periods and intra-cell handover will limit the capacity gains estimated from the static system level simulations. The simulations also indicate that the maximum system capacity can not be increased by HR/QR adaptation