| Performance evaluation of ad-hoc network protocols depends heavily on mobility models used to describe the movement of network nodes. The performance of a mobile ad-hoc network may change dramatically from one mobility model to another, hence we need to measure the degree of mobility independent of the mobility models themselves. Most of the mobility metrics proposed so far do not accurately capture the network dynamics, and are dependent on the mobility models and network size.
In the paper, we first propose a generalized mobility metric that can characterize network dynamics independent of the mobility model and the network size. It is built upon the probability of link change (creation and breakage) using entropy functions. We show that it satisfies the requirements for a generalized metric of network dynamics, and that it is independent of mobility models and network size.
Next, to illustrate practical relevance of the proposed metric, we derive analytical expressions for probabilities of link breakage and creation for an example of mobility model, i.e. random walk. The analytical results are then compared with simulation results for the same scenarios, thus verifying the derivation of link change probabilities and illustrating the utility of the proposed metric.
The proposed metric is built upon the probability of link change. Unlike the commonly used network-wide measures of link change rate or link duration, the probability of link change defined here is a link property that reflects network dynamics as a function of both time and position in the network. It captures changes in topology (connectivity) at a given time and for a given area of the network, independent of the mobility model and the network size.
The entropy of link change, i.e. our proposed metric of network dynamics, represents the amount of information required to describe changes in network topology. As such, it is a useful tool in investigations of the cost of routing and the limits on routing performance as functions of network dynamics and network resources (bandwidth). This, as well as other applications of the proposed metric, will be briefly discussed in the paper. |
| Quang-My Tran received the Diploma in Telecommunications from Saint-Petersburg State University of Telecommunications in 1994, and the Master of Engineering in Information Technology & Telecommunications from the University of South Australia in 2001. Apart from study, Mike has worked in various positions at Ho Chi Minh City Post and Telecommunications, and he also spent 5 months working experience under masters program with Motorola in Adelaide, Australia. Mike commenced his PhD with the Institute for Telecommunications Research, University of South Australia in 2004. His areas of research include wireless and mobile communications, especially mobility and routing in mobile ad hoc networks. |