Growth in mobile telecommunications was met with great enthusiasm in Nigeria at its early stages but later resulted in frustration due to diminished quality of service (QoS)(1). In Nigeria and many other countries, mobile communication has been troubled with complications spanning across human and technical issues. However, because good quality of service must have been enjoyed before the time of bad receptions, it becomes important to study the underlying reasons for such drop in signal quality delivered(2). Obstacles and surfaces within the vicinity of the device have an effect on the path characteristics (3). Signal propagation models then, are used largely in network planning, most especially for conducting feasibility studies and during initial deployment of mobile communications systems. They are also very useful for performing analyses on interference as the deployment of these networks proceed.
These models may be broadly categorized into three kinds namely; empirical, deterministic and stochastic. Empirical models are those based on observations and measurements alone. These models are mainly used to predict the path loss, but models that predict rain-fade and multipath have also been proposed. The deterministic models make use of the laws governing electromagnetic wave propagation to determine the received signal power at a particular location. Deterministic models often require a complete 3-D map of the propagation environment (e.g. ray-tracing model). Stochastic models, however, see the environment as a collection of random variables making them the least accurate but requiring very minimal information about the environment and make use much less processing power to generate their predictions (4).
The Walfisch-Ikegami model is an empirical model from J. Walfisch and F. Ikegami and was further developed by the COST 231 project. This is now called the COST- Walfisch-Ikegami Model. The accuracy of this model is limited to its consideration of buildings only in the vertical plane and quite high because in urban environments, multiple diffractions over rooftops are predominant. Wave guiding effects due to several reflections are not considered however, in the model(5).
The study is borne out of the need to understand why hitherto good quality of service enjoyed by end users of GSM telecommunications suddenly deteriorates and in a way as to understand how physical and environmental factors play a part in this phenomenon.
1.3 Problem Statement
The problem addressed here is to compare the results of Walfisch-Ikegami model for pathloss with observed path loss by determiningthe strength of GSM signals at different locations of varied site parameters with respect to base stations’ within the University of Ilorin Campus.
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