  The widespread application of wireless services and dense devices access have
triggered huge energy consumption. Because of the environmental and financial
considerations, energy-efficient design in wireless networks becomes an
inevitable trend. To the best of the authors' knowledge, energy-efficient
orthogonal frequency division multiple access heterogeneous small cell
optimization comprehensively considering energy efficiency maximization, power
allocation, wireless backhaul bandwidth allocation, and user Quality of Service
is a novel approach and research direction, and it has not been investigated.
In this paper, we study the energy-efficient power allocation and wireless
backhaul bandwidth allocation in orthogonal frequency division multiple access
heterogeneous small cell networks. Different from the existing resource
allocation schemes that maximize the throughput, the studied scheme maximizes
energy efficiency by allocating both transmit power of each small cell base
station to users and bandwidth for backhauling, according to the channel state
information and the circuit power consumption. The problem is first formulated
as a non-convex nonlinear programming problem and then it is decomposed into
two convex subproblems. A near optimal iterative resource allocation algorithm
is designed to solve the resource allocation problem. A suboptimal
low-complexity approach is also developed by exploring the inherent structure
and property of the energy-efficient design. Simulation results demonstrate the
effectiveness of the proposed algorithms by comparing with the existing
schemes.
