The Effect of Packet Delay on Voip Speech Quality: Failure of Hurst Method

Voice over Internet protocol (VoIP) is a technology that transports voice data packets across packet switched networks using the Internet protocol (IP). However, the current Internet, which was originally designed for data communications, provides best-effort service only, and does not guarantee to transmission quality. As known, packet delay dramatically degrades the quality of VoIP calls. It is widely accepted the network was self-similar. The degree of self-similarity can be expressed by the Hurst parameter H (0.5<H<1), so the effect of packet delay often modeled as a function of Hurst. However Hurst coefficient is long time statics character, in quality prediction model, the perceptual value will vary widely for a single H value while time change. In this paper, we carefully set up a testing environment to measure the impairment of packet delay. From the experiment result , it is clear that the Hurst function mentioned in previously work can not determine the delay effect suitably. In fact, we found it is accurate by using some function of the standard deviation of the packet delay.