Techreport,
Wireless Backhaul Networks: Minimizing Energy Consumption by Power Efficient Radio Links Configuration
RR-6752. INRIA, (December 2008)
Abstract
In this work, we investigate on minimizing the energy
consumption of a wireless backhaul communication network through a
joint optimization problem of data routing and radio configuration.
The backhaul network is modeled by a digraph in which the nodes
represent radio base stations and the arcs denote radio links.
According to the scenario under consideration, a power efficient
configuration can be characterized by a modulation constellation size
and a transmission power level. Every link holds a set of power
efficient configurations, each of them associating a capacity with
its energy cost. The optimization problem involves deciding the
network's configuration and flows which minimize the total energy
expenditure, while handling all the traffic requirements
simultaneously. An exact mathematical formulation of the problem is
presented. It relies on a minimum cost multicommodity flow with
stepwise cost functions which is very hard to optimize. We then
introduce a linear relaxation of the problem, which exploits the
convexity of the energy cost as a function of the throughput on a
radio link. This yields lower bounds on the energy consumption, and
eventually a heuristic algorithm based on the fractional optimum is
presented. Our models are validated through extensive experiments
which are reported and discussed. The results of the simulations
testify the potentialities behind this novel approach. In particular,
our algorithm takes a good advantage of the convexity of the cost
function, inducing a quite small integrity gap in practice.
