  In order to meet the growing mobile data demand, future wireless networks
will be equipped with a multitude of access points (APs). Besides the important
implications for the energy consumption, the trend towards densification
requires the development of decentralized and sustainable radio resource
management techniques. It is critically important to understand how the
distribution of signal processing operations affects the energy efficiency of
wireless networks. In this paper, we provide a cross-layer framework to
evaluate and compare the energy efficiency of wireless networks under different
levels of distribution of the signal processing load: (i) hybrid, where the
signal processing operations are shared between nodes and APs, (ii)
centralized, where signal processing is entirely implemented at the APs, and
(iii) fully distributed, where all operations are performed by the nodes. We
find that in practical wireless networks, hybrid signal processing exhibits a
significant energy efficiency gain over both centralized and fully distributed
approaches.
