  Energy efficiency is essential for Wireless Body Area Network (WBAN)
applications because of the battery-operated nodes. Other requirements such as
throughput, delay, quality of service, and security levels also need to be
considered in optimizing the network design. In this paper, we study the case
in which the nodes access the medium probabilistically and we formulate an
energy efficiency optimization problem under the rate and access probability
constraints for IEEE 802.15.6 Impulse Radio Ultra-wideband (IR-UWB) WBANs. The
proposed algorithm, dubbed Energy Efficiency Optimization of Channel Access
Probabilities (EECAP), determines the optimal access probability and payload
frame size for each node. The simulation results show that our algorithm
rapidly converges to the optimal solution. We also provide detailed insights on
the relationship between the optimal access probabilities and other network
parameters such as the link distance, the number of nodes, and the minimum rate
constraints.
