Energy Efficiency for MISO-OFDMA-Based User-Relay Assisted Cellular Networks

The concept of improving energy efficiency (EE) without sacrificing the service quality has become important nowadays. The combination of orthogonal frequency-division multiple-access (OFDMA) multiantenna transmission technology and relaying is one of the key technologies to deliver the promise of reliable and high data rate coverage in the most cost-effective manner. In this article, EE is studied for the downlink multiple-input single-output OFDMA-based user-relay assisted cellular networks. EE maximization is formulated for the decode and forward relaying scheme with the consideration of both transmit and circuit power consumption as well as the data rate requirements for the mobile users. The quality of service constrained EE maximization, which is defined for multicarrier, multiuser, multirelay, and multiantenna networks, is a nonconvex and combinatorial problem so it is hard to tackle. To solve this difficult problem, a radio resource management algorithm that solves the subcarrier allocation, mode selection, and power allocation separately is proposed. The efficiency of the proposed algorithm is demonstrated by numerical results for different system parameters.