Empirical Modeling and Estimation of End-to-End VoIP Delay over Mobile Multi-hop Wireless Networks

We present an empirical model of the upstream end-to-end Voice-over-IP (VoIP) delay over a mobile, multi-hop wireless network towards a single gateway. First, we define the "VoIP regime" as the regime of network operation in which a fraction 1 - epsilon of the packets are received by the gateway within the maximum tolerable VoIP networking delay y(voip), and such that epsilon is less than a maximum tolerable outage probability. We show that within the VoIP regime, the upstream VoIP delay is well-modeled by an exponential distribution whose parameter lambda(i) depends on the number of hops i to the gateway. Second, we show that the coherence time of the VoIP regime is large enough such that the estimation of the {lambda(i)} can be performed by the gateway, and distributed to the nodes such that each node can utilize the {lambda(i)} in estimating the end-to-end delay from its current location for autonomous call admission decisions. Third, we validate the empirical model across scenarios that range from a flat deployment region, to a deployment region with holes, and to the case where there is background User Datagram Protocol (UDP) data traffic. The results are significant for enabling VoIP over high-mobility, multi-hop wireless networks, and in aiding node-based call admission decisions.