Low-bit-rate voice and telephony over ATM in cellular/mobile networks

A new ATM AAL2 to support low-bit-rate and delay-sensitive applications in an ATM environment has been approved by the ITU-T and ATM Forum. AAL2 allows multiplexing of voice/data packets (minicells) from different users in a single ATM connection, thus improving the utilization of the network resources. This article identifies issues related to AAL2 such as the application environment, the gain obtained by multiplexing voice packets from different users on a single ATM connection, buffer requirements, and cell assembly delay. To analyze these issues, we modeled and simulated ATM trunking between a base transceiver station and the mobile switching center. The performance simulations show that the multiplexing gain obtained by AAL2 is significant, and the output buffer requirement at the ATM node is small. In addition, the results show that a timeout mechanism is needed to limit the ATM cell assembly delay in order to meet the delay requirements of real-time traffic such as voice.