Research On Cooperative Communication Technology Of Wireless Networks Based On Energy Efficiency

Since the wireless communication can transmit information using electromagnetic technology through open unlimited space, so compared to wired communications, it gets more attention by people, in recent years, it is one of the fastest development speed of communication subject. In the wireless transmission, because of the restriction caused by multipath fading channels, people use MIMO technology to increase the diversity gain, anti multipath fading. But in the wireless network (such as wireless sensor networks), due to the limitation of volume and hardware of relay node, traditional MIMO transmission is difficult to achieve, so the cooperative communication or virtual MIMO technology have emerged as the times require. For energy constrained wireless networks, it is often difficult to supplement the energy of the node, so how to increase the energy efficiency in the given cooperative wireless networks has become a major challenge. This thesis studis the related cooperative communication technology of wireless networks, specific works are as follows:Firstly, this paper studies the improved adaptive relaying protocol based on opportunistic relaying. In view of the current fixed relaying protocol and adaptive relaying protocol, simulation results show that the incremental relaying protocol performances best in system outage probability. Because of the deficiency that incremental relaying only consider the channel gain of the source node to the destination node, this paper presents an improved adaptive relaying protocol, making the relay node can adaptively choose either amplify and forward or decode and forward mode according to the channel state, and gives the outage probability expression of the protocal applied to multi-relay scene at high SNR. The simulation results show that, compared with the original protocol, the adaptive relaying protocol which is given in this paper can reduce the system outage probability effectively.Secondly, aiming at the DF multi relay cooperative networks, this paper studies the multi relay selection scheme to increase system throughput and network lifetime. Unlike traditional virtual MIMO scheme, the multiple relay selection scheme which is given in this paper, selects the appropriate subset of potential relays to complete information transmission, considering the residual energy information and the current channel state information of the relay nodes, to avoid excessive specific relay node energy consumption. The simulation results show that compared with the traditional virtual MIMO scheme, multiple relay selection scheme which is given in this paper, can not only prolong the network lifetime effectively, while increasing the network throughput under it’s lifetime.Finally, aiming at the DF multi relay cooperative networks, this paper studies the optimal relay selection scheme to increase the network lifetime. Through the establishment of the system model, whether the system outage probability is lower than a certain threshold is to determine the network alive. After establishing the set of potential relay, selecting the optimal relay node according to the residual energy, the minimum transmission power, the desired transmit power of the relay node and system outage probability. The simulation results show that, compared with the existing relay selection schemes, the optimal relay selection scheme which is proposed in this paper, can effectively improve the network lifetime, and has a higher energe efficiency.