Performance evaluation and dimensioning for AAL2 CLAD

The traffic performance of ATM Adaptation Layer 2 (AAL2) cell assembly and disassembly (CLAD) is evaluated by an analytical method where AAL2 is standardized to convey low-bit-rate traffic such as mobile traffic including IMT-2000. The analytical formulas are applicable to dimensioning of the bandwidth of the output link of the CLAD. In particular, this paper evaluates the number of channels that can be multiplexed in the fixed capacity output link of AAL2 CLAD for various timeouts and buffer sizes. The arrival process is modeled as a discrete Markovian arrival process considering the talkspurt and silence period of a voice source, and discrete-time tandem queues modeling a cell assembly queue and a transmission queue are analyzed. An approximation model and its accuracy are also investigated and shown to be good for accuracy and computation time. The short packet loss ratio, which is lower than the cell loss ratio, is derived. Through numerical examples, this paper shows the statistical multiplexing gain of AAL2 and the various parameter ranges that yield higher efficiency than STM. It also shows that timeout has a complicated impact on the performance of AAL2, as a result of changes in the characteristics of cell arrival at the transmission queue