Outdoor radiolinks for 2.4 GHz-frequencies: measurement results and experiences within the radio communication network “Intermobil Region Dresden"

Abstract. The radio communication network “Intermobil Region Dresden" was developed and built up for data transmission of traffic videos and other traffic data. It uses Pointto- Point (PtP) and Point-to-Multipoint (PtM) bridges, forming the backbone structure. The traffic camera radio clients link up with Accesspoints, installed at the nodal points of the backbone. This paper analyses the physical and technical conditions, building up such radio communication networks. The radio channel properties (e.g. total path loss, multipath propagation) and the technical parameters (e.g. transmission power, sensitivity, antenna gain) belong to this conditions. Based on calculation and spreading measurements it is shown, that reserves have to be considered during the planning already. As well special problems, like Fresnel-zone clearance and shadowing are discussed. The choice of the antenna plays a key role for planning and building of wireless networks. It determines decisively the range and gives an important contribution to elimination of wireless disturbances (interferences). Dependent on topological facts, installation environment and wireless distance omnidirectional-, yagi-, patch- and parabol-antennas are used. Based on antenna measurements the paper discusses the use and property of decoupling. WLANs are working in the license free 2.4 GHz-band. The number of radio systems in this band increases permanently, which leads to a lot of interferences among each other. The paper makes a classification of possible interference sources and discusses their influence on transmission quality. Technical solutions are shown for increase interference robustness.