Research Of Wireless Ad Hoc Networks Based On Multi-Rate

A Wireless Ad Hoc Networks is a set of nodes that can communicate with others in a multi-hop fashion without any assistance of fixed infrastructures and every node can move freely and relay data for others. Its main advantage is that it can be rapidly deployed without base station. The Wireless Ad Hoc Networks can be applied where pre-deployment of network infrastructure is difficult or impossible, for example, mobile meeting, disaster areas, and armies on the march.The IEEE 802.11 wireless media access standard in Wireless Ad Hoc Networks supports multiple data rates at the physical layer by employing different modulation and channel coding schemes. Nodes can utilize auto rate adaptation algorithm by automatically adapting the transmission rate to best match the channel conditions, and achieves better network performance. Research on multiple transmission rates is very important for the advancement of Wireless Ad Hoc Networks. This thesis studies four multi-rate issues for Wireless Ad Hoc Networks, including minimizing delay multicast routing in multi-rate Wireless Ad Hoc Networks, scheduling based on multi-rate transmission in Wireless Ad Hoc Networks,multi-rate routing in Wireless Ad Hoc Networks based on fuzzy petri net,relay algorithm based on network coding in wireless local network.The main results of the thesis are as follows:(1) Minimizing Delay Multicast Routing in Multi-rate Wireless Ad Hoc Networks: According to the multi-rate capacity at PHY layer, the optimal multicast delay in Wireless Ad Hoc Networks is studied. The main idea is replacing a lower rate transmission of upstream node with some transmissions from high to low to minimizing the multicast delay according to critical path based on the priority principle of high rate. Firstly, this problem is formulated as an optimization problem. Moreover, a Distributed Minimizing Delay Multicast Routing (DMDMR) algorithm is present and proved to be an optimal algorithm. The simulation results show that DMDMR algorithm can decrease of up to 21% over the multicast delay than the classic technique that the upstream node broadcast a packet only once.(2) Scheduling Based on Multi-rate Transmission in Wireless Ad Hoc Networks: This paper studies the multi-rate scheduling in Wireless Ad Hoc Networks. Firstly, we formulate it as an optimization problem. Moreover, the Highest Rate First without Considering Buffer (HRFWICB) algorithm and the Highest Rate First with Considering Buffer (HRFWCB) algorithm are present. Their main idea is scheduling prior the flow with higher transmission rate to decrease the transmission time and delay subject to that the minimum channel allocation for each flow is guaranteed. Finally the simulations are performed to compare our algorithms with Luo algorithm and Greatest Potential Packet First (GPPF) algorithm. The results show the algorithms can greatly decrease the transmission time and delay.(3) Multi-rate Routing in Wireless Ad Hoc Networks Based on Fuzzy Petri Net: This paper studies the expect media visiting time routing to improve throughput in multi-rate Wireless Ad Hoc Networks. The main idea is to select a path with the minimum except media visiting time based on the packet loss rate and the transmission rate of a link. Firstly, the problem is formulated as an optimization problem. Moreover, the Expect Media Visiting Time (EMVT) routing algorithm is present. As a consequence, the candidate route may contain a lot of high transmission rate and low packet loss ratio links. Simulation results show that EMVT algorithm can increase throughput and decrease delay over the Minimum Hop Amount routing algorithm and the routing algorithm which only considered the transmission rate.(4)Relay algorithm Based on Network Coding in wireless local network: The network coding is a new technology in the field of information in 21st century. It could enhance the network throughput and save the energy consumption. The present achievement is mainly based on the single rate. However, with the development of wireless network and equipment, wireless local network MAC protocols have already supported the multi-rate transmission. This paper proposes a Relay Algorithm Based on Network Coding (RABNC) and analyzes the transmission time gain of the algorithm over the traditional relay algorithm. The simulation results show that our algorithm could achieve the transmission time decrease of up to 17% over the traditional relay algorithm.