Effect of path loss model on received signal: Using Greater Accra, Ghana as case study

Globalization has been greatly supported by wireless applications and as a result, African countries have connectivity to other parts of the world through satellite for instance. On a national level, wireless applications have proved to be invaluable where mobile services can be the means by which lives can be saved. In a developing country such as Ghana, mobile services are used not only in entrepreneurial activities, but are a means for enhancing the quality of life. Whereas wireless transmitters and receivers can be designed based on specifications, the structures of buildings considering parameters such as height and slopes of roofs vary considerably from place to place. It therefore becomes imperative to evaluate the propagation through the radio space particularly in places where such differences are observed in close proximity. This paper presents a study of propagation in the Greater Accra region of Ghana where some sections have structures of relatively similar heights close to areas where building heights greatly vary. The study is done employing the Hata-Okumura model which is widely used in telecommunications industry, particularly in West Africa. A comparative study on path loss between Hata-Okumura model, and measurement data using the received power obtained from Base station in a Code Division Multiple Access-2000 (CDMA2000^®) cellular network in Ghana has been carried out. The analysis shows that Hata-Okumura prediction for suburban area (University of Ghana) response achieved is close to the measurement plot. Hata-Okumura prediction models applied in urban (medium city) and rural (open) areas for the selected areas such as Osu and Tema respectively in Greater Accra (GA) region show a little agreement. Osu and Tema are each more densely populated and have buildings that have more variation in height than the suburban area of University of Ghana.

I. Introduction

A path loss model basically predicts the behaviour of a transmitted signal while in transit along the physical layer of a wireless network to the receiver [1], [2] and it is important in mobile cellular system design stage. It is used to evaluate the link budget, determine the cell size, estimate the fade margin and for frequency reuse planning in Global System for Mobile communication (GS:rvI) cellular networks [2]. There are deterministic and stochastic propagation models used in design, optimization,. and performance evaluation of cellular mobile radio systems [2]. Deterministic models are based on electromagnetic simulations (utilizing ray tracing together with geometrical optics and uniform theory of diffraction, finite difference time domain method, etc.) making use of information of the specific physical environment or on measurements. Stochastic models also called local mean propagation models describe the propagation phenomena on average terrain of the fading distributions (log-normal, Rayleigh, Rician distributions [3]). The modified Okumura model [4] by Hata [5] is mostly used in telecommunications industry. It takes into account the graphical information of the Okumura model and incorporates the effects of diffraction, reflection and scattering as a result of structures along the path.