| Summary: | 碩士 === 國立高雄應用科技大學 === 電機工程系 === 100 === Cooperation technology [11] takes use of the spatial diversity characteristic to improve network performance while the directional antenna [13] technology takes use of the spatial reuse. [9-10]It is questionable to combine the two to get a better throughput. In this thesis, we are motivated by this to explore how and what to combine these two technologies. The thesis also proposed an active helper searching scheme which is used for D-CoopTable [9] in cooperative networks. With the help of this scheme, the sender can find a proper helper in time for its data transmission.
In the active helper searching scheme, we take use of a timer which is responsible for periodical refreshing the D-CoopTable entry to enhance the network traffic performance.The default interval we use is 5 seconds.We fill the entries of the table both from the active searching and passive overhearing.After the active searching process, the routine overhearing process can enrich the entries of the CoopTable.The active searching process may be re-activated if the timer is up.
Simulation of performance evaluation is done with NS2. We developed a directional antenna module which takes use of the TwoRayGround formula to determine the Tx/Rx power at nodes. Simulation setup is described as following: {the packet type is UDP and packet size is 128Bytes}. We can show that for the proposed active help searching scheme, the throughput can be improved by 9%. We can also show that in terms of fairness and throughput, the network with sparse node distribution is more suitable for the combination of the two technologies.
The contributions of this these include proposing an active helper searching scheme for D-CoopTable, the analysis of throughput for different kinds of directional nodes position layout in heterogeneous networks and the related simulation module development. In the future, we can be considered to develop directional MAC, cooperative MAC and directional routing mechanism of the module.
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