
Selfishness-Aware Energy-Efficient Cooperative Networks 149
sion, that is, U
i
(t) < 0, would be removed from relay selection. Moreover,
since most terminals are battery-powered, it should balance the energy con-
sumption of each node as much as possible to maximize the network lifetime,
which, in this chapter, is defined as when the first node runs out of energy.
In the following discussions, we illustrate how power efficiency, cumulative
benefits, energy consumption fairness, and network lifetime are considered
in relay selection.
At time
t, we denote the nodes with nonnegative utility as a set M
{m =1, 2,...,M},whereU
m
(t) ∈ R
+
, ∀m ∈M. Then, the activ