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Research and Application on the Handoff Scheme in Subway Mobile Wireless Network

Author: ZhaoLiFang
Tutor: ChenBing
School: Nanjing University of Aeronautics and Astronautics
Course: Applied Computer Technology
Keywords: A wireless communication network To switch Delay Packet loss rate Link layer buffer Channel quality indication
CLC: TN929.5
Type: Master's thesis
Year: 2009
Downloads: 90
Quote: 0
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Abstract

With the wireless communication technology and the development of urban rail transit, wireless local area network has been more and more applications to the subway environment. In a slow moving environment, wireless local area network to meet the requirements of network access; wireless LAN support for mobility in a fast-moving environment lacking. How to improve the quality of service in a fast-moving environment, especially a reduction in the high-speed mobile handover latency and packet loss, and problems to be solved. The subject from the Jiangsu Province, significant achievements into special \How to ensure that the wireless switch in the car - to communicate is the most important issue of the entire communication system, switching performance directly affects the quality of service to the wireless network. This paper first introduces the wireless network in the subway communication environment, analyzes the existing problems in the current mobile wireless communications environment; then a comparative study on the current wireless switching scheme for the the subway mobile wireless communication environment, in respect of vehicle wireless station (STA ) using a single, double Wireless LAN switch environment; Finally, the system implementation and testing of two switching scheme. The STA wireless card environment, delay and packet loss in the handover process improvement methods. Switching delay, combined with the subway application environment, with a reduction in the number of scanning channels, effectively reducing the scan delay; packet loss, a data link layer buffer algorithm - Layer2-Buff algorithm. The algorithm in the the guidance network data link layer data transmission through a dedicated buffer store-and-forward switching process to reduce packet loss rate, to improve the quality of network services. Finally to adopt Ixchariot smokeping test software from the handover latency, network throughput and packet loss rate three single wireless card switch program test analysis, and the results show that the programs greatly reduce the network delay, and also with the number of packet loss in the handover process reduce effectively improve network throughput in the switching process. In the the STA the double wireless card environment, we control the STA's two wireless cards to work together to achieve soft switching. First, the channel quality indication is introduced into the wireless switch obtained according to the historical data train traveling of the handover process the channel quality indication of the change, and thereby determine the timing of replacement of the work NIC; then the data transmission process performed monitoring to a certain threshold i.e. replacement work card, coordinating two wireless card to achieve soft switching function. Under normal circumstances, a wireless card for data transmission, another piece of card to complete the switch to do auxiliary functions; switching abnormal or abnormal NIC switching mechanism using a single wireless card. The experimental results show that the program on the basis of the single wireless card switch mechanism to further solve the problem of network latency, to the maximum extent possible to ensure the reliability of data transmission in subway mobile communication network environment.

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