| Cooperative communication is an active research area in the field of wireless communications in recent years. As an efficient way of mitigating wireless channel fading, enhancing communication reliability, improving network capacity and saving energy, cooperative communication is widely used in wireless sensor networks.The cooperative MAC protocol and power allocation solution are the research objectives in this study, and NS2and MATLAB are the simulation tools.In the course of studying cooperative MAC protocol, the state-of-the-art cooperative MAC protocols are analyzed and an improved cooperative MAC protocol (IC-MAC) based on the C-MAC protocol is proposed. IC-MAC redefines the selection standard of relay channel based on the packet error rate, and the simulation results present that IC-MAC outperforms C-MAC and legacy802.11b MAC.Due to the additional power consumption of relay node, the trade-off relations of cooperative gain and additional power consumption should be considered. By taking into account the power consumption of RF circuitry, the total power loss formulas of Selective Decode-and-Forward cooperative transmission, direct transmission and multi-hop transmission are derived in terms of outage probability under Nakagami-m fading channel. The simulation results present that the cooperative transmission outperforms direct transmission and multi-hop transmission in terms of energy saving after a certain transmission range. Based on the above research, this study proposes an optimization solution of transmission power allocation, named Half Transmission Power Allocation Solution, abbreviated as HTPAS. HTPAS can save more energy than the Equal Transmission Power Allocation Solution (ETPAS). The simulation results prove HTPAS is more energy efficient and has higher cooperative gain than ETPAS. Furthermore, HTPAS algorithm is simple and easy to be implemented. |
