Provision of Conversational Services over the GERAN: Technical Solution and Performance

A number of "GERAN Evolution" features have been standardized for Rel-7 by 3GPP TSG GERAN. One of the goals was to provide full support, in the Packet Switch (PS) domain, for Real Time services characterised by a low end to end delay (e.g. VoIP). This paper describes the technical solutions aiming at the optimization of the transmission of radio blocks over the radio interface, whose limitations are currently preventing the deployment of delay-sensitive data applications in the GERAN (GSM/EDGE Radio Access Network). In particular, the paper provides a description of the features which have been introduced to reduce the Round Trip Time (RTT) of the RLC protocol, namely: Reduced Transmission Time Interval (RTTI) radio blocks, a Fast Ack/Nack Reporting strategy and the RLC Non-Persistent mode operation. Simulation results are then provided, showing the performance of a VoIP service realized over a GERAN network implementing the above features.