Abstract: In this paper we present a new approximation algorithm for
the Minimum Energy Broadcast Routing (MEBR) problem in ad hoc
wireless networks that has exponentially better approximation factor
than the well-known Minimum Spanning Tree (MST) heuristic. Namely,
for any instance where a minimum spanning tree of the set of stations
is guaranteed to cost at most ½ times the cost of an optimal solution
for MEBR, we prove that our algorithm achieves an approximation ra-
tio bounded by 2 ln ½ ¡ 2 ln 2 + 2. This result is particularly relevant for
its consequences on Euclidean instances where we signi¯cantly improve
Abstract: An ad-hoc mobile network is a collection of mobile hosts, with wireless communication capability, forming a temporary network without the aid of any established fixed infrastructure. In such a (dynamically changing) network it is not at all easy to avoid broadcasting (and flooding).
In this paper we propose, theoretically analyse and experimentally validate a new and efficient protocol for pairwise communication. The protocol exploits the co-ordinated motion of a small part of the network (i.e. it is a semi-compulsory protocol) in order to provide to various senders and receivers an efficient support for message passing. Our implementation platform is the LEDA system and we have tested the protocol for three classes of graphs (grids, random graphs and bipartite multi-stage graphs) each ing a different ?motion topology?.
Our theoretical analysis (based on properties of random walks) and our experimental measurements indicate that only a small fraction of the mobile stations are enough to be exploited by the support in order to achieve very fast communication between any pair of mobile stations.
Abstract: In wireless communication, the signal of a typical broadcaststation is transmittes from a broadvast center p and reaches objects at a distance,say , r from it. In addition there is a radius ro, ro < r, such that the signal originating from the center p should be avoided. In other words, points within distance ro from the station compise a hazardous zone. We consider the following station layout problem: Cover a given planar region that includes a collection of buildings with a minimum number of astations so that every point in the region is within the reach of a station, while at the same time no interior point of any building is within the hazardous zone of a station. We give algorithms for computing such station layouts in both the one- and two - dimensional cases