Abstract
This paper considers the problem of finding minimum-energy cooperative routes in a wireless
network with variable wireless channels. We assume that each node in the network is equipped with a
single omnidirectional antenna and, motivated by the large body of physical layer research indicating
its potential utility, that multiple nodes are able to coordinate their transmissions at the physical layer
in order to take advantage of spatial diversity. Such coordination, however, is intrinsically intertwined
with routing decisions, thus motivating the work. We first formulate the energy cost of forming a
cooperative link between two nodes based on a two-stage transmission strategy assuming that only
statistical knowledge about channels is available. Utilizing the link cost formulation, we show that
optimal static routes in a network can be computed by running Dijkstra’s algorithm over an extended
network graph created by cooperative links. However, due to the variability of wireless channels,
we argue that many-to-one cooperation model in static routing is suboptimal. Hence, we develop an
opportunistic routing algorithm based on many-to-many cooperation, and show that optimal routes in
a network can be computed by a stochastic version of the Bellman-Ford algorithm. We use static and
opportunistic optimal algorithms as baselines to develop heuristic link selection algorithms that are
energy efficient while being computationally simpler than the optimal algorithms. We simulate our
algorithms and show that while optimal cooperation and link selection can reduce energy consumption
by almost an order of magnitude compared to non-cooperative approaches, our simple heuristics perform
reasonably well achieving similar energy savings while being computationally efficient as well.
Refereed
No
