Energy efficiency (EE) of cellular networks has received considerable attention recently. However, EE of relay-assisted cellular networks has not been thoroughly addressed, especially the tradeoff between EE and spectral efficiency (SE). In this paper, considering downlink transmission in a single cell of a relay-assisted cellular network with symmetric relay deployment, and modeling the locations of mobile users as a spatial Poisson point process, a simple geometric model is built to analyze the EE. A metric defined as the ratio of average area throughput to average area power consumption is used to measure the average EE and its analytical expression is derived. The tradeoff between the average EE and the average SE is formulated as an optimization problem to which the closed-form solution is difficult to obtain. Through numerical simulations, the impact of the number of relay stations (RSs) and the location parameter of RSs on the average EE are evaluated. The results show that in some cases the average EE is a quasi-concave function of the number of RSs or the location parameter of RSs.
['Hongbin Chen', 'W. B. Chen', 'Feng Zhao', 'Lisheng Fan', 'Han Zhang']
Stochastic geometry analysis of downlink energy efficiency for a relay deployment scheme in relay-assisted cellular networks