Design Of Cooperative Communication Schemes Towards The Problem Of Energy Consumption In Wireless Networks

As the evolution of network architecture, more and more attention has been drawn to energyconsumption in wireless network. And "Green" has become an important development direction ofwireless communication. In the development of green communication, cooperative communicationis an active research area.This thesis studies green communication based on the cooperation among nodes. Two parts ofwork is included in this thesis. One is the research on joint optimization of transmit power of sourcenodes and cooperation nodes. And the other is the research on compensative cooperative spectrumsharing scheme.This thesis begins with an overall introduction of cooperative communication and itsapplication in OFDM, physical layer network coding and distributed space-time coding. Energyefficiency and time efficiency act as new evaluation criteria is proposed for green communication.And then a jointly optimization scheme of transmit power of source nodes and cooperationnodes is proposed, which takes the joint function of energy efficiency and time efficiency as theoptimization target. The closed expression of the transmit power of source nodes and cooperationnodes is given by using the classical KKT (Karush-Kuhn-Tucker) conditions though Lagrangemethod. This scheme can reduce the energy consumption and the computational complexity ofcooperative communication system.Finally, this thesis studies compensation cooperative spectrum sharing technology. Anoptimization scheme based on time division is proposed, which improves energy-efficiency of thesystem by flexibly distributing time proportion and cooperation transmission power. For theprimary user, the time saved in cooperative spectrum sharing is just the time rewarded to the seconduser, which needs no additional signaling overhead and computation. For the second user, it getsmore transmission opportunities. So, the energy efficiency of the system has been improved greatly.