Voice Over ATM Using AAL2 and Bit Dropping: Performance and Call Admission Control

ATM Adaptation Layer 2 (AAL2) has been designed for efficient transport of voice, facsimile (FAX), and voiceband data (VBD) traffic over ATM land-line and wireless networks. The protocol helps achieve low latency and high bandwidth efficiency while applying suitable compression methods on voice/VBD/FAX calls and digital speech interpolation (DSI) on voice calls. We analyze the performance and capacity of an ATM multiplexer based on AAL2 adaptation. We assume that embedded ADPCM is used to compress voice, and DSI is used to achieve statistical multiplexing gain. The embedded ADPCM coding scheme allows selective dropping of less significant bits of voice during congestion in the ATM multiplexer. We compare the call capacities of voice multiplexers with and without bit dropping. The performance models and results are general, and can be used for traffic engineering and call admission control in land-line or wireless ATM systems for a variety of voice/voiceband compression algorithms.