Use of the burst voice arrival lag (BVAL) as a measure of performance that detects packet burst errors (PBER) for voice over IP systems

摘要

A new measure of performance for voice over IP systems, the burst voice arrival lag (BVAL), strongly discriminates the occurrence of packet burst loss, as opposed to an equal number of packets lost randomly. Traditional measures of performance for voice over IP systems are based on long term statistics such as packet error rate, which does not capture the distinction of burstiness properties of a given system. This distinction is important because perceptible noise clicks are experienced in systems that exhibit burst packet losses. BVAL is a measure of performance that depends on the starvation of the playback buffer implemented in real time systems such as the real time protocol (RTP). The BVAL parameter can be used for improved path selection in a routing algorithm or feedback in a RTP session over the real time control protocol (RTCP) when used over an IP system. It can also be used to compare the quality of service provided by different systems. This paper derives a mathematical expression for BVAL. It proceeds by calculating its value, first, for a system that experiences random losses, and then for a system that experiences burst packet losses of a fixed size number of packets, N. The BVAL for these systems is compared and is shown that the greater N becomes, the larger BVAL becomes (even though the long-term packet error rate remains constant). Then, a relationship is derived and graphed to show the sensitivity of BVAL as a function of N and the packet completion rate. Then, the comparison is generalized to a system that experiences burst packet losses of different sizes.