Improved coverage and interference predictions using line-of-sight detection and correction

During Autumn 1995 a set of field measurements were performed in the outskirts of Oslo to check the validity of the Okumura-Hata prediction model. Test results indicated a prediction error of 10-20 dB in areas which had a line-of-sight (LOS) path between base station and the measurement vehicle. Using a computer program to identify the LOS sections, four alternative solutions has been considered. Replacing the morpho correction with an "open terrain" correction factor of 18 dB to the existing model resulted in an average prediction error of 2.3-3.3 dB. However, the error seemed to have a distance dependency, indicating that a separate LOS model replacing the fixed correction factor with a modified attenuation gradient will be the best solution to the LOS prediction problem in urban areas.