Performance evaluation of the AAL2 protocol within the UTRAN

The AAL2 protocol was chosen as a transport protocol within the UMTS Terrestrial Radio Access Network (UTRAN). This protocol handles the radio channels between the mobile terminal and the Radio Network Controller (RNC). On radio channels, the time constraints are stringent because of the synchronisation mechanisms at the MAC layer. The AAL2 protocol should guarantee a certain Quality of Service (QoS) for the traffic handled on the AAL2 connections.In this paper, we introduce a general description of the AAL2 protocol and its position in the UTRAN and we study some performance issues of this protocol. We propose two schemes to transport the AAL2 traffic on the Iub and Iur interfaces and we study different scheduling algorithms (FCFS, RR, WRR, EDF, Priority) at AAL2 level in order to evaluate the performance of each algorithm. The optimal Timer-CU value is studied in this paper in order to choose a trade-off between time constraints and bandwidth efficiency. The equivalent bandwidth is calculated in order to evaluate the capacity of a VC supporting AAL2 connections. Finally, the AAL2 switching technology is compared with the ATM switching technology in the case of a traffic concentrator in order to evaluate the advantages of the AAL2 switching.