The Study For Access Nets' Topological Structures And Their Appraise Based On Cities' Structure

Along with the development of our society, users put forward more and more demands for telecommunication , and telecommunication operation are turning from the traditional phoning and telegraphing to operations such as video frequency , data , picture, language and multimedia , As a result , the former lines are not capable now . So ITU-T put forward a concept as "Access Net"and regulate its frame, function, type and management .Access Nets are the systems between exchangers and users'devices ,They can substitute the traditional lines . The whole telecommunication net is made up of 3 parts transport net , exchange net and access net. Our country is just starting up to build access nets, The task is arduous and strenuous. Since the invest would be vast and cycle long . Therefore users are cost-sensitive. The technique and topological structure are important to the country's information basic building and modernization of telecommunication . Consequently we must work out appropriate topological structure and Development tactics. Choices of transmitting medium and topological structure of the network are very important. They are the most important technological factors that can influence the communication and economical results .When planning and design network , It can help us to economize the cost and raise the efficiency to choose the suitable topological structure according to the need. After the LAN is built up the topological structure can help us for regular maintenance and trouble judging etc. So, It's necessary to study the infection that Access Nets'topological structure act to the whole telecommunication net. In the planning or before the built, if the topological structure is selected correctly. The telecommunication quality would be good. There are a lot of domestic and international achievements about research to the access net. but most of them are research about access net technology , even development trend of access net technology. Few are studied about communication characteristic to the topological structure of the access network. Quantitative appraisal researches haven't been worked till now. And nobody has studied how to apply different topological access nets according to urban structure . So, how to plan and build Access Nets correctly ? How to select the best ? And how is its financial status? These questions are ready to be solved. To these questions , This thesis summarized Access Nets'topological structures . So far Access Nets own some structures such as star, bus, circle, tree, But the Access Nets usually are combined by some of them. At that time , I consulted a lot of stuffs such as stuffs about computer nets or topological structures. And then I summarized different urban structure and their each requisition for communication. And summarized the application for the topological structure of access net. The structures type and characteristics of the city are geometry abstract to the cities, such concrete characteristics as geography ,physics , climate , and humanity etc of cities are abandoned. The only factor that is considered is the overall arrangement position of the space. And the requisition for communication is summarized on the basis of the analysis according to the urban structure characteristic and the information flows .The requisition for communication includes the different kinds of user's requisitions for communication of communication distributed in the city. Communication user are mainly...