  A cooperative medium access control (CoopMAC) network with randomly
distributed helpers is considered. We introduce a new helper selection scheme
which maximizes the average throughput while maintaining a low power
consumption profile in the network. To this end, all transmissions are assumed
to be performed using power control. We assume that each node can estimate the
channel between itself and a receiving node. Then, it evaluates the minimum
transmission power needed to achieve the desired signal to noise ratio (SNR).
If the required transmission power is less than the maximum transmission power
of the node, the communication is regarded as successful. Otherwise, the
transmission is canceled. %Also, we classify the helpers into six groups
according to their transmission rates IEEE 802.11b Standard. In order to
increase the average throughput, we assume that the cooperative link with the
highest transmission rate is chosen from those that can successfully forward
the source signal to destination. Also, when there are several links with the
same rates, the one with minimum required power is given the highest priority.
Assuming that the helpers are distributed as a Poisson point process with fixed
intensity, we derive exact expressions for the average throughput and the power
consumption of the network. Simulation results show that our scheme is able to
significantly increase the throughput in comparison to the conventional CoopMAC
network. It is also able to reduce the power consumption compared to a network
with no power control approach.
