The Research Of Radio Frequency Energy Harvesting In Cooperative Communications

Cooperative communication is one of the important technologies of the next generation wireless network. Relay can help transfer information during its spare time, which can improve the performance of the communication. But the relaying process will cause the loss of the energy of relays, which will reduce the lifetime of the network. Radio frequency energy harvesting allows relays collecting energy from radio frequency signals, thus radio frequency energy harvesting can solve the problem of energy assumption of relays in cooperative communication. This thesis deal with the cooperative protocols in cooperative communication systems.This thesis firstly introduces the cooperative protocol in cooperative communication networks with radio frequency energy harvesting, namely, the time-switching protocol and the power-splitting protocol. The time-switching protocol contains two types of protocol as continuous time energy harvesting protocol and discrete time energy harvesting protocol. Then the thesis gets the range of energy harvesting time to obtain the minimum outage probability through simulation based on the traditional three-node cooperative network model.This thesis secondly deals with the typical three-node cooperative network, and a new cooperative method based on time-switching cooperative protocol with radio frequency energy harvesting is proposed. Relays firstly collect radio frequency energy from the ambient environment, then use the collected energy to perform decode-and-forward cooperative method, and the duration of each phase can be assigned due to the network coeffients. Simulation results show that the new cooperative method can achieve full diversity gain in the two-hop cooperative network, and the network lifetime can also be prolonged due to the radio frequency energy harvesting technology.At last the thesis introduces the cooperative protocols in cooperative communication systems with energy-constrained source nodes which also need to perform energy harvesting before sending its message. This theis also compares the outage performance of the protocol through simulation. Finally, the energy cooperation protocol and energy-information cooperation protocol are compared.