Radio Coverage Calculations of Terrestrial Wireless Networks using an Open-Source GRASS System ANDREJ HROVAT * , IGOR OZIMEK * , ANDREJ VILHAR * , TINE CELCER * , IZTOK SAJE + and TOMAŽ JAVORNIK * * Department of Communication Systems, * Jozef Stefan Institute, + Mobitel, d.d. * Jamova cesta 39, SI-1000 Ljubljana, + Vilharjeva 23, SI-1000 Ljubljana *+ SLOVENIA andrej.hrovat@ijs.si http://www-e6.ijs.si Abstract: - Radio network planning and dimensioning have significant impact on the overall system capacity of the cellular communication systems. Various commercial network planning and dimensioning tools with different radio signal propagation models implemented are available on the market. Their price and especially inflexibility led us to look for an open-source solution. The present paper describes usage of the open-source Geographical Resources Analysis Support System (GRASS) for the radio signal coverage calculation. GRASS modules calculating radio coverage prediction for a number of different radio channel models were developed which, together with module considering antenna radiation pattern influence, compute radio signal coverage for a defined cell. The complete network coverage is computed with modules for generating a data base table (e.g. MySQL, PostgreSQL), arranging the values in increasing order and determining maximal received power at each receive location. Additional modules for adapting input data and analyzing simulation results were also developed. The radio coverage tool accuracy was evaluated by comparing with results obtained from a dedicated professional prediction tool as well as with measurement results. Key-Words: network planning tool, open-source, GRASS GIS, path loss, raster, clutter, radio signal coverage 1 Introduction Emerging user applications call for increased bandwidth of communication systems. Consequently, higher frequencies are used in wireless systems while the size of radio cells is becoming smaller. The cellular concept enables lower transmission power and frequency reuse in cells that are far enough from each other. However, due to the increased complexity, a wireless system has to be planned carefully. Cellular system planning involves determining the number and the locations of base stations, their hardware and software, frequency and code planning. One of the aims is to efficiently use the allocated frequency band and to assure high radio coverage. For the calculation of radio coverage, various mathematical radio propagation models are being used [1, 2, 3, 4]. They can be divided into three groups: (i) statistical models, (ii) deterministic (or theoretical) models and (iii) combinatorial models. Statistical models are described by a mathematical expression depending on the distance between a transmitter and a receiver and numerous parameters. The expression and parameters are obtained by measurements of radio signal in a specific geographical environment. The reliability of the model depends on the accuracy of the measurements and on the resemblance of the environment in which the model is used to the environment in which the measurements were carried out. Due to the simplicity of their mathematical expressions, statistical models enable fast calculation of radio coverage. Typically, they are used to calculate radio coverage of macro-cells. Deterministic models are based on the physical laws that drive the propagation of radio waves. Examples of considered propagation mechanisms are: free space radio wave propagation, diffraction, scattering, reflection, absorption, and refraction. These models may be used in different environments but require extensive databases of geometrical and electromagnetic environment properties. Deterministic models are complex and computationally demanding. Thus, they are useful only for calculating radio coverage of smaller areas, e.g. micro-cells or inside buildings. Combinatorial models combine the advantages of statistical and deterministic models, i.e. fast calculation and partial consideration of terrain characteristics. For example, in many commercial tools, statistical models are used as a base and then improved by consideration of shading, diffraction and scattering. Various commercial programming tools are available for radio coverage calculation. The first representative tools were designed for mobile WSEAS TRANSACTIONS on COMMUNICATIONS Andrej Hrovat, Igor Ozimek, Andrej Vilhar, Tine Celcer, Iztok Saje, Tomaz Javornik ISSN: 1109-2742 646 Issue 10, Volume 9, October 2010