Dinesh Sharma & Purnima K Sharma 
Development of Field Propagation Model for Urban Area 

Wireless communication is one of the most dynamic and vibrant areas of technology development in the communication field today. It has been found that severe climatic conditions disturb the propagation of electromagnetic signals at higher frequencies (greater than 30 MHz). The disturbance is mainly due to molecular absorption by oxygen for frequencies ranging between 60 and 118 GHz and due to water vapour in 22, 183 and 325 GHz bands. Rain and fog has the most significant impact, since the size of the rain drops is of the order of the wavelength of the transmitted signal. This results in energy absorption by the rain drops themselves, and as a secondary effect energy is scattered by the drops. The frequency selective absorption characteristics of the atmosphere can be approximated by a transfer function. In most of the practical channels when the signal propagates through the atmosphere the effect of many factors on the signal has to be considered along with the free space propagation channel assumption. The main objective of this study is, therefore, to find out whether, and how, the different climatic conditions are influencing radio wave propagation in GSM frequency bands in general and in Narnaul, Haryana (India) in particular. To carry out this investigation, the records of radio wave propagation along with path loss during different climatic conditions have been analyzed. On the strength of these analyses, a propagation path loss model has been developed by proposing suitable correction factors due to different climatic conditions. The validation of this developed path loss model has been verified by taking reference models and by applying practically in different urban areas. The effect of these climatic conditions on the link budget has also been analyzed.