| Future mobile communications will develop towards higher spectrum efficiency, higher frequency operation, more flexible network construction and more flattened network structure. Its purpose is to adapt the network to high-transmission-rate broadband wireless mobile communications system. Distributed antenna system is a novel network structure to improve the capacity of wireless network, extend the signal coverage and increase varies of wireless service.In China, with the support of national 863 Hi-Tech Program, FuTURE framework, the key project for future mobile communication system, did the successful field trial and realized 100Mbps data rate for wireless transmission in Shanghai at the end of 2006. This paper focuses on the main characteristics of B3G mobile communications experimental network and the challenges of the network construction techniques. It highlights the realization of the scheme for building B3G mobile communications experimental network in engineering level.First, the author briefly introduces the concept and characteristics of distributed wireless system, analyses the advantages, disadvantages and feasibility of the wireless network construction scheme. According to the parameters of B3G experimental system, 3GPP model and COST 231-Hata model were selected for wireless link budget. Then the design value of the distance between the transmitter and the receiver was obtained. It provides reference for determining the cell radius.Furthermore, in the implementation of network construction engineering, with respect to the mounting multiple antennas scheme, designing the cells and building network based on RoF transmission, the technical difficulties of building B3G mobile communications experimental network are described. In terms of the scheme of mounting multiple antennas, on the basis of the full research of the effects on system performance imposed by multiple antenna configurations and some configuration examples, the author presents a novel structure of multiple antennas, which makes the antenna configuration scheme flexible. The layout of buildings and environmental features are taken into account for cell design. The paper presents more than two schemes for building cell and analyzes the advantages and disadvantages of the schemes. Further selection is based on the measurement and analysis afterwards. RoF network construction properly utilizes the fiber resources, addresses the difficulties of re-blanketing fiber in urban area and satisfies the needs of transmitting signals in B3G mobile communications experimental network.Finally the thesis, through field trial, with respect to the performance of both signal coverage and RoF transmission, validates the network construction scheme. Since no commercial measurement system is operating at the trial frequency band l, the coverage testing is a difficult topic. The author, with other staff of the team, developed a measurement system based on general testing devices. It exploits the method of testing CW to realizes the automatic measurement and improve the testing efficiency. For RoF transmission performance measurement, the optical power meter and OTDR were used to ensure the reliability of the testing results. The results shows that the coverage and the performance of fiber link are able to meet the needs of the field trial; good foundation is made for further B3G system field trial…... |
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