Research On Real Time Industrial Wireless Local Area Network Media Access Control Protocol

In the communication networks of the real time system such as industrial control, with the increase of the traffic intensity and differentiated service classes, the traditional field bus techniques are gradually found to be incapable to cope with these needs. The LAN techniques such as Ethernet or Wireless LAN (WLAN) are adopted in the industry communications. Especially because the deployment of WLAN does not demand additional cable layout, and the movement of the node is supported, so the WLAN is favored. But these LANs have the inherent disadvantage that cause the indeterminable waiting time for the data frames, so they can not be directly applied to communication networks with high timing requirement. Therefore the design of real time wireless LAN media access protocol, which can ensure the waiting time upper bound for the real time frames being of high value to the system security, and can dispose the communication of multiple classes of frames with different timing requirements become a valuable research project.The mean and second moment of frame's waiting time are important performance parameter for real time communication network. It is a difficult task to find the exact analytical solution for these measures. Thus the existing researches focus only in the cases where each station only has one frame class and the adopted service disciplines are exhaustive or gated. In the traditional designs of real time MAC protocols, the study of the arriving characteristic of sporadic real time frame is often neglected. If the arriving of real time class conforms a Poisson distribution, there will be no protocol which can ensure that all the consecutive two frames can be transmitted successfully in the upper bounded times. In fact for these urgent frames, a minimum distance between consecutive arriving instants exist, so according to this characteristic, a new distribution based on Poisson distribution is proposed. Therefore both the polling-based and the contention-based protocol of this thesis can ensure the waiting times of frame class with the highest priority are upper bounded.The major contributions of this thesis are summarized as follows.A real time wireless local area network media access protocol is proposed, in which each...