Performance analysis of a packet voice messaging system

摘要

A preliminary generic architecture is proposed for a packet voice messaging system (PVMS) which provides 'answering machine' service in a packet-switched environment. Its performance is considered in light of constraints imposed by the required quality of stored speech. A critical element in determining this quality is overflow in the PVMS packet buffer, which buffers packets of voice samples delivered to the PVMS for storage. A two-dimensional Markov chain analysis of the buffer occupancy of the PVMS is developed. Mean values and distributions of buffer occupancy are derived and validated against simulation. From these distributions, the probability of packet loss due to buffer overflow can be estimated, and the buffer can be sized to restrict overflow to an acceptably low level. In addition, the disk block size can be chosen to balance the tradeoff between the packet buffer size and wasted disk space.