Wireless Quality-of-Service support

Guest Editorial

Wireless Quality-of-Service support     

A mobility-transparent deterministic broadcast mechanism for ad hocnetworks

Broadcast (distributing a message from a source node to all other nodes) is a fundamental problem in distributed computing. Several solutions for solving this problem in mobile wireless networks are available, in which mobility is dealt with either by the use of randomized retransmissions or, in the case of deterministic delivery protocols, by using conflict-free transmission schedules. Randomized solutions can be used only when unbounded delays can be tolerated. Deterministic conflict-free solutions require schedule recomputation when topology changes, thus becoming unstable when the topology rate of change exceeds the schedule recomputation rate. The deterministic broadcast protocols we introduce in this paper overcome the above limitations by using a novel mobility-transparent schedule, thus providing a delivery (time) guarantee without the need to recompute the schedules when topology changes. We show that the proposed protocol is simple and easy to implement, and that it is optimal in networks in which assumptions on the maximum number of the neighbors of a node can be made     

Resource assignment for integrated services in wireless ATM networks

The task of supporting integrated multirate multimedia traffic in a bandwidth-poor wireless environment poses a significant challenge for network designers. In this paper we propose a novel bandwidth allocation strategy which partitions the available bandwidth amongst the different traffic classes in a manner that ensures quality-of-service guarantees for digital video while minimizing the maximum blocking probability for voice and data connections. At the connection level, near-optimum utilization of the reserved bandwidth for video traffic is achieved through an intra-frame statistical multiplexing algorithm, while at the system level the delicate task of partitioning the bandwidth between voice, video and data is accomplished by developing an efficient algorithm which uses traffic parameters consisting only of the aggregate traffic load and the total available bandwidth. The algorithm, built on non-trivial mathematical results is robust, easy to implement and has a geometric rate of convergence which ensures that the partitioning points are found quickly. These properties make it well suited for practical implementations, even for cases where changes in the aggregate traffic loads cause bandwidth allocations to be recomputed frequently. © 1998 John Wiley & Sons, Ltd.     

Cancellation properties of products of graphs

This note extends results of Fernández, Leighton, and López-Presa on the uniqueness of rth roots for disconnected graphs with respect to the Cartesian product to other products and shows that their methods also imply new cancelation laws.     

On k-planar crossing numbers

The k-planar crossing number of a graph is the minimum number of crossings of its edges over all possible drawings of the graph in k planes. We propose algorithms and methods for k-planar drawings of general graphs together with lower bound techniques. We give exact results for the k-planar crossing number of K_2k+1,q, for k?2. We prove tight bounds for complete graphs. We also study the rectilinear k-planar crossing number.     

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