Study On Mine Wlan Terminal Design And Roaming Switch Technology

With the continuous development of information and intelligence in coal mine, wireless communication is gradually deepened as a complement of mine wired communication network. The traditional wired video surveillance system can not meet the inconvenience or inability to use, such as mobile wired video surveillance monitoring and inspection and other occasions goals due to a lot of wiring in the construction and the lack of mobility. Combining cable and wireless networks to achieve the seamless coverage of network signal is the development trend of communication systems in coal mine. However, due to the covering capacity of the Wi Fi network access point is limited, leading to the support for user mobility is very limited. The mobile subscriber roaming between different AP cells, will cause handoff frequently. If the delay of handoff is too long, it will affect the quality of the real-time services significantly, such as video surveillance. Therefore, handoff had always been a critical and challenging issue in related areas. This thesis has mainly researched the following aspects of the design of mobile video surveillance terminal in coal mines.(1) This paper firstly studied the key technologies of the realization of mine mobile video surveillance terminal. Then, it systematically analyzed the reason and process of handoff, parsed the impact on the overall performance of the key steps in the process of handoff in detail from the perspective of time delay. By summarizing the present situations and results of handoff, analyzing the advantages and disadvantages of different handoff schemes, combining with the research background of this paper, explored feasible improvement directions.(2) This paper designed hardware circuits of mobile video surveillance terminal in mines, including the selection of processor, Wi Fi module and video acquisition module, providing excogitations of peripheral interface circuits, such as FLASH interface circuit, SDRAM interface circuit, DM9000 Ethernet card interface circuit.(3) This paper constructed the software development platform of mobile video surveillance terminal, including the porting of U-Boot, the cutting of Linux kernel, and the manufacturing of root file system.(4) In accordance with the shortcomings of the traditional thought of handoff, and the scanning process taking too long, the scheme was improved based on the background scanning scheme, designed handoff algorithm with handoff threshold and scanning threshold to guarantee the reliability of the handoff decision and the effectiveness of the handoff process. In order to verify the theoretical analysis, we had built the actual experiment platform.