Rate adaptation schemes in networks with mobile hosts

This paper considers the problem of handofF management in an Integrated Services Packet Network supporting mobile hosts. In such a network, links may become overloaded due to a high concentration of mobile hosts within a given cell. As a result, the required Quality of Service guarantees cannot be provided to all flows in that cell. However, there exists adaptive applications which can operate over a wide range of available bandwidth. Thus, it may be possible to overcome the link overload condition by reducing the bandwidth of individual flows, which we call rate adaptation. The two most important properties of a rate adaptation scheme are its network overhead and its fairness property. Rate adaptation schemes which ensure certain fairness properties, such as maxmin optimality criteria, have very high network overhead. Therefore, these schemes are not suitable for a highly mobile environment where rate adaptation may have to be invoked frequently. In this paper, we investigate the tradeoff between the network overhead and the fairness property of rate adaptation in a mobile environment. We first characterize the fairness property of rate adaptation by several measurable parameters. We then describe two rate adaptation schemes, one of which has very low network overhead but is 'unfair', while the other scheme is 'fair' but has very high network overhead. Finally we propose a new rate adaptation scheme which reconciles the two conflicting properties. Results of simulation experiments comparing the performances of the three rate adaptation schemes are presented.