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

摘要

The radio communication network “IntermobilRegion Dresden" was developed and built up for data transmissionof traffic videos and other traffic data. It uses Pointto-Point (PtP) and Point-to-Multipoint (PtM) bridges, formingthe backbone structure. The traffic camera radio clientslink up with Accesspoints, installed at the nodal points ofthe backbone. This paper analyses the physical and technicalconditions, building up such radio communication networks.The radio channel properties (e.g. total path loss, multipathpropagation) and the technical parameters (e.g. transmissionpower, sensitivity, antenna gain) belong to this conditions.Based on calculation and spreading measurements it isshown, that reserves have to be considered during the planningalready. As well special problems, like Fresnel-zoneclearance and shadowing are discussed. The choice of theantenna plays a key role for planning and building of wirelessnetworks. It determines decisively the range and gives an importantcontribution to elimination of wireless disturbances(interferences). Dependent on topological facts, installationenvironment and wireless distance omnidirectional-,yagi-, patch- and parabol-antennas are used. Based on antennameasurements the paper discusses the use and propertyof decoupling. WLANs are working in the license free2.4 GHz-band. The number of radio systems in this bandincreases permanently, which leads to a lot of interferencesamong each other. The paper makes a classification of possibleinterference sources and discusses their influence ontransmission quality. Technical solutions are shown for increaseinterference robustness.