Sensitivity degradation and antenna isolation analyses for a multi-operator global systems for mobile communication base transceiver stations

In other to mitigate challenges associated with the expansion of Global System for Mobile Communication (GSM) systems, infrastructure sharing have been proposed and adopted by some GSM operators. When infrastructure sharing is done, there is the possibility of degradation of quality of service due to Electromagnetic Compatibility issues, interference between operators, sensitivity degradation, increasing noise floor, antenna isolation requirement issue. This paper analyses the sensitivity degradation and the effects of spatial separation on antenna isolation requirement of Base Transceiver Station (BTS) receiver for a multi-operator mobile cellular systems. The data used were extracted from standards of organisation like European Telecommunications Standards Institute (ETSI) standards and others. Antenna dimension were obtained from physical observations of BTS site. By comparison with identified metrics in the standards, we verified that the number of operators that can share infrastructure is limited by the allowable sensitivity degradation. It was noted that an antenna isolation of 70dB can be achieved for GSM 900 band antennas and when GSM 1800 band antennas are used, 90dB antenna isolation is achievable greater than the minimum recommendation of 30dB.Keywords: Antenna isolation, base station, BTS, GSM, infrastructure sharing, receiver sensitivity, sensitivity degradatio

Assessment of multipath and shadowing effects on UHF band in built-up environments

Ultra-high frequency (UHF) bands are radio frequencies in the range of 300 MHz and 3 GHz. These bands are used for television broadcasting, mobile cellular systems, Wi-Fi, satellite communications and many others. Effective communication link in the UHF band requires direct line of sight between the transmitters and receivers. However, this is not always the case in built-up areas where diverse obstacles such as large buildings, trees, moving objects and hills are present along the communication path. These obstacles result in signal degradation as a result of shadowing (blockages) and multi-path, which are two major causes of signal losses. Path loss models are used in predicting signal losses but, the accuracy of these models depend on the fitness between the model's predictions and measured loses. In this work, the multi-path and shadowing effects on signal impairment were investigated through the use of empirical and semi-empirical path loss models analysis in built-up environments. Electromagnetic field strength measurements were conducted using four television transmitters at UHF bands along four major routes of Osun State, Nigeria. Experimental and simulation results indicated that the empirical models provide a better fit than the semi-empirical models. It was also found that the poor performance of the Knife Edge Model which is a semi-empirical model was traced to the bases of its formulation, which assumed point like knife edge for all obstacles on the path of radio propagation. The work therefore recommends that network planners employ empirical models found suitable for their kind of terrain when faced with coverage planning and optimization.Keywords: Path loss models, Radio propagation,  Terrain feature

Large-scale radio propagation path loss measurements and predictions in the VHF and UHF bands

For decades now, a lot of radio wave path loss propagation models have been developed for predictions across different environmental terrains. Amongst these models, empirical models are practically the most popular due to their ease of application. However, their prediction accuracies are not as high as required. Therefore, extensive path loss measurement data are needed to develop novel measurement-oriented path loss models with suitable correction factors for varied frequency, capturing both local terrain and clutter information, this have been found to be relatively expensive. In this paper, a large-scale radio propagation path loss measurement campaign was conducted across the VHF and UHF frequencies. A multi-transmitter propagation set-up was employed to measure the strengths of radio signals from seven broadcasting transmitters (operating at 89.30, 103.5, 203.25, 479.25, 615.25, 559.25 and 695.25 MHz respectively) at various locations covering a distance of 145.5 km within Nigerian urban environments. The measurement procedure deployed ensured that the data obtained strictly reflect the shadowing effects on radio signal propagation by filtering out the small-scale fading components. The paper also, examines the feasibilities of applying Kriging method to predict distanced-based path losses in the VHF and UHF bands. This method was introduced to minimize the cost of measurements, analysis and predictions of path losses in built-up propagation environment

Clutter Height Variation Effects on Frequency Dependen Path Loss Models at UHF Bands in Build-Up Areas

In this work, the performance of eight prominent empirical path loss models and a localized model, in predicting path losses in build up areas is investigated. Multi-transmitter electromagnetic field strength measurements were conducted, using a dedicated Agilent spectrum analyzer, along five predefined routes in Osun State, Nigeria. The measured data were compared with the model predictions. Path profile and terrain undulations effects have been observed on the received signal. For all the routes and transmitters, Okumura, SUI models over predicted the path losses, while Ericsson model under predicted the losses. However, Hata, Davidson, Cost 231 and ILORIN models generally show promising results with varying performance. The average mean error values of 55.11 dB, -8.53 dB, 46.72 dB, -9.81 dB, -28.16 dB, -8.93 dB, -30.59 dB, -22.95 dB and -12.57 dB are respectively obtained for NTAOSOGBO transmitter for Okumra, Hata, SUI, Cost 231, CCIR, Davidson, Ericsson, EEC-33 and ILORIN models. In terms of RMSE, the  average RMSE values of 9.24 dB, 9.08 dB and 9.18 dB were obtained for ILORIN, Hata and Davidson models respectively. This trend was found to be similar for other transmitters i.e. OSBC, NDTV and NTA Ile Ife with varying performances among the four contending models. We, further, examined the route performance for the two main contending models i.e. ILORIN and Hata models. Inconsistency in terms of the performance for each model were observed, however the localized model i.e. ILORIN was found to provide optimum path loss prediction with considerable accuracy, over the other models. With the aforementioned, we believe the results and observations presented would provide guide to radio system engineers in making informed choices on the applicability and predictability of such models in the terrain of Osun State and other similar build-up areas in Nigeria