The Research And Implementation Of WLAN Technology In Large-scale Networks

At present, the Internet of things industry develops rapidly, the IEEE sets up a specialized working group of 11 ah to formulate the corresponding standard wireless network. The draft version has been released. In our country, China Academy of Telecommunication Research is also drafting corresponding domestic standards with several schools and companies. Wireless sensor is playing an irreplaceable big role. The IOT is playing an irreplaceable role. The problem of the capacity of wireless network has been paid more and more attention of the researchers. Also, energy saving in wireless network is a hot issue in the research of wireless networks because of the size of the node and battery technology. The current WLAN technology can’t apply to the IOT directly for the reason that the data rate is low and the number of the network is very big. So we need to study the WLAN technology for the IOT.The smart nodes of the IOT need not working all the time, so they can go to sleep to save the energy without communication. This thesis simulated the S-MAC protocol which made the nodes listening and sleeping periodically on the base of analysis and study of the S-MAC protocol.The number of the IOT usually is more than 6000, but the effectiveness of traditional CSMA protocol will decrease significantly with the number of users increase. In theory, the throughput of the node tends to be 0 when the number of users exceeds 200. To support large-scale nodes access, this thesis put forward the Interval Transmission Mechanism of the SYNC frame(ITMS). The main idea of the mechanism is the control of the transmissions mechanism of the SYNC frame. Using the method of time division multiplexing, ITMS makes nodes obtain channel access in different time to avoid conflict of the data packet and improve the success rate of transmission. Under the premise of ensuring the throughput and packet loss rate, ITMS makes the number of the network can be more than 6000. Meanwhile, this thesis made a comparison of the simulation between the improved and the original 802.11 MAC and verified that the ITMS is a very effective method in enhancing the capacity of wireless networks.At last, on the bases of the theory of load balancing, this thesis put forward the selection method of relay in the scene of 802.11 ah.The procedure is finding out the nodes which can connect to only one relay firstly. Then find out the intersection of relays which can satisfy all the other nodes that have more than one relay can connect to and distribute nodes to relay in ascending order by the number of relay optional. This method can be used as much as possible to reduce the number of the relay in the wireless network to save the power of the relay and avoid the collisions, improve the bandwidth utilization. At last, the thesis made a simulation and verified the feasibility of the method.The thesis presented the simulation of the proposed methods and verified the feasibility. The methods enhanced the performance of the wireless network.