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In future mobile communication systems, the cell-size will be very small. Many wireless backhaul solutions will be used for the scalability from the small scale to the large-scale networks. It may be admitted that, highly directional antennas will be used by the transmitting node, but these networks will be case sensitive to the cluttered environment. The mobile device-to-device communication may be used as relays, and further be equipped with the beam selectivity capability. However, their energy efficiency may greatly depend on the Medium Access Control (MAC) protocols (Zhuang & Zhou, 2013) despite the modulation schemes effect on the power amplifiers’ efficiency (Luis et al., 2010).
For instance, Long Term Evolution (LTE) system uses a hybrid of three modulation schemes (The IET, 2013) such as 64 Quadrature Amplitude Modulation (QAM), 16QAM and Quadrature Phase Shift Keying (QPSK) modulation. QPSK is used for users farther away from the Base Station; this is very robust to interference. The 64 QAM is used for users close to the Base Station, to provide very fast data speeds and very high capacity. In (Jain et al., 2011), a perspective layered network has been discussed in which the hierarchical layouts comprise the macro, micro, pico, and femto-cell with the aim of offering a diversity of services to meet high capacity demand whereby the macro-cell and the microcell overlaid each other. The enhanced layered layout in (Yang et al., 2012), is proposed with Orthogonal Frequency Division Multiplexing (OFDM) with multi-cell combination. Therefore, a dynamic multiplexing with the base station’s coordination capability has been evaluated to enhance the network load capacity. In (Ziaul et al., 2013), the emphasis was on the heterogeneous architecture of multi-cells in which macro-, micro-, pico- and femto-cell could overlap one another. This method has been proven efficient for energy savings. In (Guowang et al., 2013), the cross-layers’ optimization has been recommended. Similar approach has been shown to have efficient energy for the LTE power management system (Oliver, Dietrich, & Ulrich). The power efficient protocol relies on discontinuous reception (DRx) and discontinuous transmission (DTx) mode for the mobile handset. This has also been proved effective in minimization of the handset battery. In contrast, the study in (Andrews, 2005) has underestimated such techniques for improving energy efficiency. This was argued that the method would not necessarily be vital for one end to the other (transmitter to the receiver) since energy efficient requirement in both uplink and downlink is interference limited. Coverage ratio to the Base transceiver station’s optimal transmission has been investigated in (Zhou et al., 2013). In (Holtkamp et al., 2013), a radio resource management’s algorithm has been proposed that aimed at minimizing the base station supply power consumption for multi-user MIMO OFDM. Meanwhile, (Lopez-Perez et al., 2013), has introduced a self-organization rule, based on minimizing cell transmit power, in which a distributed cellular network could converge into an efficient resource reuse pattern. Two resource allocation algorithms, being autonomous and coordinated have been proposed.