Research On Relay Selection For IEEE 802.11ad WLAN

Millimeter wave communication is the key to the implementation of the high-definition video and other large capacity wireless transmissions because of its rich resources of bandwidth, high transmission rate, strong anti-interference ability and good privacy performance. Millimeter wave communication technology is becoming more and more attractive. However, with short wavelength and poor diffraction ability, millimeter wave signal is very sensitive to the obstacle of barriers, making the communication link be interrupted easily. In order to solve the problem, the technology of relay coordination communication has been introduced. However, directional antenna has been used for communications between nodes in the millimeter wave network, which has also brought the problem of hidden nodes. In addition, communication delay will be severely affected by relay cooperative communication.In order to solve the two problems above, directional relay selection algorithm under the hidden nodes and the minimum communication delay relay selection algorithm have been proposed. The influence of the hidden nodes has been considered and the relay node selection criteria have been introduced in the relay selection algorithm. The collaborative MAC layer protocol is designed and three dimensional Markova chain model has been established to analyze the communication performance of the relay cooperative MAC protocol. The influence of the communication delay between relay nodes can be reduced by the minimum relay delay selection algorithm. The delay analysis model has been established with the analysis of the communication delay of different communication link. Particle swarm optimization algorithm has been used to optimize the model. Finally, several spare nodes have been selected as a relay to assist communication.The simulation results prove that communication performance increase after joining directional relay selection algorithm under the hidden nodes. With the variable link congestion probability and user number, the saturation throughput has also been improved in the millimeter wave network. Moreover, the minimum delay relay selection algorithm has been added to collaboration, which can further improve the saturation throughput of millimeter wave network and reduce the communication delay of relay link. MAC protocol communication delay model is optimized by particle swarm optimization algorithm, which can ensure minimum delay of relay nodes and make the entire network delay minimum.With the proposed algorithms, relay communication delay is minimized in millimeter wave network under the influence of directional hidden nodes. Saturation throughput of the system has also been improved. Therefore, relay coordination communication can solve the problem of millimeter wave signal being interrupted easily and guarantee the communication link under the shortest relay delay without interruption.