Reliable Multipath Packet Transmission Scheme For Wireless Mesh Network

Wireless Mesh Network (WMN) is a kind of distributed, self-organizing, multi-hop wireless network which is made up of radio nodes organized in a mesh topology. As a kind of new network access technology, wireless mesh network combines the advantages of Wireless LAN and Ad hoc and has the following excellent features, such as easy deployment, higher reliability, self-healing, high data rate which attracts great attentions on it. Nowadays more and more wireless network standard try to support wireless mesh network like IEEE802.11s which is used in Wi-Fi technique, IEEE802.16which is used for Wireless Metropolitan Area Network and people call it WiMax. IEEE802.15is supposed to be widely used in the field of Internet of things which is also called ZigBee. Despite so many merits, wireless mesh network cannot get rid of the nature weakness of wireless links, high noise, easy to suffer interference and fading. Therefore how to increase packet transmission reliability in wireless mesh network becomes a research hotspot recent years.In this thesis we did some researches on wireless network standard and the characteristics of wireless links by simulation, classification, analysis and contradistinction. We especially paid our attentions to the mechanism of Media Access Control layer and Physic layer of wireless standard. On this foundation we designed and improved our wireless mesh network packet transmission scheme for "Quality of Service (QoS)" and "reliability". They are as follows:(1) The reliable packet transmission over wireless mesh network is a guarantee for network quality of service. In order to avoid more overhead caused by loss of data packets and the decrease of network quality, this paper proposed a new packet transmission scheme which located between network layer and data link layer by adding redundant packets and using multipath routing. It is called "RTRM". Our scheme will not only increase the reliability but also to preserve the original transmission data rate. This scheme is both suitable for TCP protocol and UDP protocol. Meanwhile we proposed some different redundant packet transmission strategies. By analysis and comparison with simulation we pick the one which has the best performance and add it into RTRM.(2) By using RTRM we found that wireless mesh network is a data rate sensitive network. That means our scheme will improve the reliability only in the case of low data rate. In the high data rate scenario RTRM has worse performance than usual, especially when we use heavy redundancy strategy. From this feature of wireless channels we did a lot of simulations and analyses, and found out the basic reason of packet loss during transmission and proposed a formula for counting packet loss rate. Based on that formula we proposed a self-adapting packet transmission scheme which is called S-RTRM. This new scheme has improved in redundant scheme selection and network traffic distribution.It can automatically change its redundancy strategy and packets distribution strategy by supervising the performance of wireless links. By doing this it can be best adaptive to an individual path. What’s more, it has much better performance in high data rate scenario, so it is suitable in a larger range of data rate.