Energy Efficiency with Proportional Rate Fairness in Multi-Relay OFDM Networks

摘要

This paper investigates the energy efficiency (EE) in multiple relay aidedOFDM system, where decode-and-forward (DF) relay beamforming is employed tohelp the information transmission. In order to explore the EE performance withuser fairness for such a system, we formulate an optimization problem tomaximize the EE by jointly considering several factors, the transmission modeselection (DF relay beamforming or direct-link transmission), the helping relayset selection, the subcarrier assignment and the power allocation at the sourceand relays on subcarriers, under nonlinear proportional rate fairnessconstraints, where both transmit power consumption and linearly rate-dependentcircuit power consumption are taken into account. To solve the non-convexoptimization problem, we propose a low-complexity scheme to approximate it.Simulation results demonstrate its effectiveness. We also investigate theeffects of the circuit power consumption on system performances and observethat with both the constant and the linearly rate-dependent circuit powerconsumption, system EE grows with the increment of system average channel-tonoise ratio (CNR), but the growth rates show different behaviors. For theconstant circuit power consumption, system EE increasing rate is an increasingfunction of the system average CNR, while for the linearly rate-dependent one,system EE increasing rate is a decreasing function of the system average CNR.This observation is very important which indicates that by deducing the circuitdynamic power consumption per unit data rate, system EE can be greatlyenhanced. Besides, we also discuss the effects of the number of users andsubcarriers on the system EE performance.