Please cite this article in press as: Fernandes LC, Soares AJM. Path loss prediction in microcellular environments at 900 MHz. Int J Electron Commun (AEÜ) (2014), http://dx.doi.org/10.1016/j.aeue.2014.04.020 ARTICLE IN PRESS G Model AEUE-51206; No. of Pages 7 Int. J. Electron. Commun. (AEÜ) xxx (2014) xxx–xxx Contents lists available at ScienceDirect International Journal of Electronics and Communications (AEÜ) j ourna l h om epage: www.elsevier.com/locate/aeue Path loss prediction in microcellular environments at 900 MHz Leandro Carísio Fernandes ∗ , Antonio José Martins Soares Departamento de Engenharia Elétrica, Universidade de Brasília, Brasília 70910, Brazil a r t i c l e i n f o Article history: Received 10 March 2014 Accepted 23 April 2014 Keywords: Electromagnetic wave propagation Radiowave propagation Genetic algorithms a b s t r a c t A model is proposed to estimate path loss in urban environments at 900 MHz when the base station antenna is below the average height of the buildings. It shows that the percentage of area occupied by buildings explains more than 20 dB of variation of the mean path loss. © 2014 Elsevier GmbH. All rights reserved. 1. Introduction In a microcell the base station antenna is usually below the aver- age height of the buildings. In this case the propagation depends less on the vertical plane (rooftop propagation) and more on the horizontal plane (propagation among the buildings). To predict the path loss in such areas it is necessary to use a model that considers some characteristics of the environment. This can be accomplished with numerical methods or with analytical equations. Usually, a detailed description of the environment and a database with the vector data describing the buildings are necessary. Two well-known models used to predict the path loss are the Hata and COST-WI models. Unfortunately, both cannot be used in this case. In microcellular environments, the base station antenna height (h bs ) is usually lower than 30 m. Therefore the Hata model cannot be used to predict the path loss, because it requires that 30 m < h bs < 200 m [1]. Although the COST-WI model is suitable for microcells and small macrocells [2], it fails when h bs < h roof (average height of the buildings) [2,3]. There are some specific models to estimate the path loss in microcellular environments when h bs < h roof . They normally use some characteristics of the environments as inputs. The Berg’s model, for example, assumes that the signal reaching the receiver will cross street canyons in the horizontal plane and will not diffract on rooftops [3]. It replaces the physical distance between transmit- ter and receiver with a virtual one that depends on the align angle among the streets. ∗ Corresponding author. Tel.: +55 6182205200. E-mail addresses: carisio@gmail.com (L.C. Fernandes), martins@ene.unb.br (A.J.M. Soares). Numerical methods such as ray-tracing can also be used to calculate the path loss in microcellular systems. It is necessary to provide a set of polygons representing the buildings to run a two-dimensional simulation (or solids, for a three-dimensional simulation). Unfortunately it is not even possible to get such data. Sometimes a satellite image of a city is all the information avail- able. In this case, it is necessary to extract the buildings description using image segmentation/classification algorithms and then using the result image to get the external buildings walls. To overcome this issue, we propose a new model to estimate the path loss at 900 MHz frequency band in microcellular systems. It was developed using a genetic algorithm and needs only two input variables, the distance (d) and the information about the buildings between transmitter and receiver (). If the vector data describing the buildings is not available, this variable can be estimated through segmentation of satellite images. The pixels of the image are cate- gorized and  can be calculated counting them. It is not necessary to extract the information about the external walls of all buildings (this last step would be necessary to use the ray-tracing algorithm). 2. Proposed model At ultra high frequencies (UHF), when both transmitter and receiver are below the average buildings height, the rooftop prop- agation can be neglected. The propagation occurs mainly along the streets, reflecting and diffracting at walls and corners of the con- structions. For this configuration and d < 500 m, up to 97% of the received power at 2145 MHz is due to a street guided propagation [4]. In fact, this also happens at other frequencies, therefore the buildings can be represented as infinity tall and the rooftop propa- gation can be neglected [5]. As a result, our model does not take into account the effect of the vertical plane on the propagation of the signal. The influence of the horizontal plane is modeled through the http://dx.doi.org/10.1016/j.aeue.2014.04.020 1434-8411/© 2014 Elsevier GmbH. All rights reserved.