Prioritized statistical multiplexing of PCM sources

Using simple multiplexer models, the performances of two prioritization mechanisms for the transmission of PCM coded signals modeled as exponential on/off sources are investigated and compared with nonprioritized transmission using statistical multiplexing and peak allocation. In both mechanisms the source traffic is partitioned into a low-priority stream and a high-priority stream. In the first approach independent channels of different quality of service are used to transport the two-priority streams. In the second approach a single channel is used in conjunction with a selective packet discarding procedure which attempts to restrict loss to the low-priority traffic. For a given source partitioning, new formulae are given to describe the average loss ratio for the low- and high-priority traffic. The effect of loss on quality for PCM coded signal is quantified by a new formula which relates signal-to-reconstruction-noise ratio to low- and high-priority-loss. The results of the investigation show that both methods of prioritized transmission can provide significant improvements in overall service quality when the channel utilization is high