Hence it is important to choose routing paths in such a way that
the lifetime of the network is maximized. This problem was first studied in
16
[7]. The authors study the problem of determining the optimal routing strategy
in a multi-hop sensor network where the objective is to maximize the
time until the first battery expires. The authors associate a fixed amount of
energy expenditure for each packet reception as well as transmission. They
then note that choosing a route with minimum total energy expenditure as
in [3, 12, 15, 17, 39, 40, 43, 45] does not necessarily maximize the network
lifetime. This is because such a strategy repeatedly uses routing paths with
low total energy expenditure, and consequently the nodes along those paths
run out of battery. Hence in [7], the authors propose using a routing scheme
that performs some form of load balancing. In other words, the originating
data from the source node is spread over several di?®erent routing paths so that
no single path is over-burdened. The authors also propose a distributed algorithm
that each sensor node must execute to determine the exact fraction of
incoming data that it must forward over all its links. They use tools from network
flow analysis [1] to solve this problem. The above work mainly focuses on
energy-e?±ciency in routing without taking into account any bandwidth constraints.
In [59], the authors study the lifetime-maximization problem under
an additional constraint of limited bandwidth over each link.
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