Energy efficiency under mobility control for device-to-divice in downlink multi-cell OFDMA systems with fractional frequency reuse and cooperative relaying

Device-to-Device (D2D) communication is proposed in cellular network as a vital technology to enhance spectral efficiency and system capacity, while reducing the energy consumption and the latency. Enabling D2D communications in multi-cell OFDMA systems poses two majors challenges: First, D2D equipements are characterizd by limited capacity of battery. Second, D2D devices inevitably suffer from co-channel interference (CCI) at cell edge. This paper addresses the mobility control (MC) for D2D in downlink multi-cell OFDMA system with cooperative relaying and Fractional Frequency Reuse (FFR) scheme. FFR and cooperative relaying schemes are proposed to improve energy efficiency (EE) and avoid CCI. In the edge region, according to a difference set and using the sectorization technique, the Frequency Reuse Factor (FRF) of 7/3 and 7/4 have been applied. The deployment of FFR with Amplify and Forward fixed relays improve significantly the system performance of FRF of 1 and 3. As shown in simulations results, the proposed cooperative MC scheme with FRF of 7/3 and 7/4 provides an improvement in term of EE nears \( 1,2.10^{6}\) bits/s/J and \(1,3.10^{6}\) bits/s/J respectively in comparison with non-cooperative scheme with FRF=3.