Abstract: Mobile system engineering encompasses the art and science of defining the best placement of transmitters to provide acceptable signal quality over a wide coverage area, (since mobile operators often cannot erect their antennas at precisely the optimum site), indicating that there is potential for further research. Mobile radio communications environment is rather a hostile environment which is subjected to continuous changes in its parameters that affect the signaling path. Hence multipath fading and its effect is noticed in the form of delay spread. Delay spread is a commonly used practical measure of the extent of time dispersion introduced by multipath channels. Delay spread measurements provide a quantitative evaluation of multipath fading. A novel technique for the estimation of delay spread has been designed and implemented. The analytical study clearly shows how delay spread fluctuations affect the mobile radio coverage area; however they are not directly proportional. It is found that delay spread is directly proportional to the minimum symbol length that can be used to avoid excessive intersymbol interference (ISI). The new GSM band 1800-1900 MHZ is considered in the measurements phase. And it is noticed that for an open area of microcell size (150x150 m) the upper delay spread limit is 180 nsec for the GSM band. Also, it is found out that in open areas where the normalised delay spread exceeds 10%, the average BER obtained is worse than 10-3. This gives rise to problems such as ISI and consequently degrades the signal quality below the required C/I of 9 dB, hence transmission problems that eventually limits the mobile radio coverage. Therefore, the existing cellular network is not fit for the emerging mobile technologies (UMTS) due to the deployment of high transmission rates.