Traffic smoothing effects of bit dropping in a packet voice multiplexer

Recent studies have shown that the superposition of packet sequences generated by packetized voice sources with speech detection exhibit high burstiness due to inherent correlations between successive interarrival times in the superposition stream. In a packet voice multiplexer without bit dropping, these correlations tend to cause significantly larger queueing delays and packet losses than would be predicted for a Poisson input stream. In this paper, we examine the performance of a packet voice multiplexer queue in which the less significant bits on voice packets are dropped during states of congestion in the multiplexer. Using the results of simulation and analytical modeling, it is illustrated that bit dropping on voice packets significantly smooths the superposition packet voice traffic by speeding up the packet service rate during critical periods of congestion in the queue. This phenomenon renders it possible to approximate the superposition process by a Poisson process for analyzing a packet voice multiplexer with,.. bit dropping. The ulUltiplexer is modeled using an M/D /l/K model in which D denotes the deterministic but state dependent nature of service. By comparison with a simulation, this model is shown to produce quite accurate performance predictions.