Energy-efficient Power Optimization Research Articles

Energy-Efficient Power Optimization with Spectrum Sensing Errors in OFDMA Cognitive Opportunistic Relay Links

We propose a novel algorithm to optimize the energy efficiency (EE) of OFDM-based cognitive opportunistic relaying links (CORL) under secondary users (SUs) incorrectly sensing the unlicensed spectrum. We formulate an optimization problem with imperfect sensing that satisfies a specified power budget for the secondary users (SUs), while restricting the interference to primary user (PU) in a statistical manner. Unlike all related works in the literature, we consider the effect of subcarrier transmission mode on the relaying links and we additionally consider the effect of limited sensing capabilities of the SUs. The optimization problem is nonconvex and it is transformed to an equivalent problem using the concept of fractional programming. With the aid of the fractional programming method, an EE-oriented power allocation policy with low complexity is proposed which adopts the bisection method to speed up the search of the optimum. Simulation results show that the EE deteriorates as the channel sensing error increases. Comparisons with relevant works from the literature show that the EE is slightly deteriorated if the SU does not account for spectrum sensing errors.

Distributed Energy-Efficient Power Optimization for CoMP Systems With Max-Min Fairness

This letter considers the power optimization problem for downlink transmission in coordinated multi-point (CoMP) systems. We aim to maximize the minimum weighted energy efficiency (EE) with QoS constraint and limited intercell coordination. The established optimization problem is converted to the standard form of max-min fractional programming problem first. Then we discuss feasibility of the Dual Dinkelbach-type Algorithm (DDA). A distributed algorithm is proposed to solve the subproblem in DDA with limited intercell coordination, where only a small number of positive scalars are shared between base stations. Simulation results show that the proposed algorithm outperforms previous schemes in terms of both the minimum EE of all the BSs' EE and fairness.

Low Complex Energy-Efficient Resource Allocation in Femtocell Networks

Femtocells have attracted growing attention in academia, industry, and standardization forums in recent years. However, most of existing works on femtocell networks are focused on spectrum efficiency and interference mitigation, energy efficiency aspect is neglected. In this paper, we investigate the energy efficient resource allocation of downlink femtocell networks in sparsely and densely deployed scenario respectively. To decrease the complexity, joint subchannel allocation and power control are decomposed into two steps. Firstly, given subchannel allocation, a closed-form best response of transmit power is obtained. Secondly, a fair energy efficient subchannel allocation metric has been derived out. At last, we propose a distributed suboptimal subchannel allocation and low-complex power control algorithm. Simulation results show that the proposed algorithm has a low complexity with slight loss of energy efficiency compared with Round-Robin Scheduling and a non-cooperative energy-efficient power optimization algorithm. 

Distributed Interference-Aware Energy-Efficient Power Optimization

Power optimization techniques are becoming increasingly important in wireless system design since battery technology has not kept up with the demand of mobile devices. They are also critical to interference management in wireless systems because interference usually results from both aggressive spectral reuse and high power transmission and severely limits system performance. In this paper, we develop an energy-efficient power optimization scheme for interference-limited wireless communications. We consider both circuit and transmission powers and focus on energy efficiency over throughput. We first investigate a non-cooperative game for energy-efficient power optimization in frequency-selective channels and reveal the conditions of the existence and uniqueness of the equilibrium for this game. Most importantly, we discover a sufficient condition for generic multi-channel power control to have a unique equilibrium in frequency-selective channels. Then we study the tradeoff between energy efficiency and spectral efficiency and show by simulation results that the proposed scheme improves both energy efficiency and spectral efficiency in an interference-limited multi-cell cellular network.