| As the evolution of network architecture, more and more attention has been drawn to energy consumption in wireless network. And "Green" has become an important development direction of wireless communication. In the development of green communication, cooperative communication is an active research area.This dissertation studies green communication based on the cooperation among nodes. Two parts of work is included in this dissertation. One is the research on joint optimization of transmit power of source nodes and cooperation nodes. And the other is the research on compensative cooperative spectrum sharing scheme.This dissertation begins with an overall introduction of cooperative communication and its application in OFDM, physical layer network coding and distributed space-time coding. Energy efficiency 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 cooperation nodes is proposed, which takes the joint function of energy efficiency and time efficiency as the optimization target. The closed expression of the transmit power of source nodes and cooperation nodes is given by using the classical KKT (Karush-Kuhn-Tucker) conditions though Lagrange algorithm. This scheme can reduce the energy consumption and the computational complexity of cooperative communication system.Finally, this dissertation studies compensation cooperative spectrum sharing technology. An optimization algorithm based on time division is proposed, which improves energy-efficiency of the system by flexibly distributing time proportion and cooperation transmission power. For the primary user, the time saved in cooperative spectrum sharing is just the time rewarded to the second user, which needs no additional signaling overhead and computation. For the second user, it gets more transmission opportunities. So, the energy efficiency of the system has been improved greatly. |
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