International Conference on Computer and Communication Engineering (ICCCE 2012), 3-5 July 2012, Kuala Lumpur, Malaysia 978-1-4673-0479-5/12/$31.00 ©2012 IEEE A Modified Multi-wall Wave Propagation Model for Concrete Based Building Structure Aween I. Sulaiman, Mohammed A. Hussein Electrical Engineering Department Faculty of engineering, University of Sulaimani Sulaimani, Iraq {aween.sulaiman, mohammed. hussein}@univsul.net Abstract—In this work several empirical propagation models have been studied based on many signal strength measurements in an indoor environment (Ophthalmology Specialized Hospital) using log-distance model for LOS (Line of Sight) area and MWM (Multi-Wall Model) for NLOS (Non Line of Sight) areas. The building is typical in Iraq (more than 85% of the buildings have this structure). It has two types of walls, 10cm and 20cm cement block walls. In this work five Multi-Wall Models have been studied and a modified one has been generated based on modifying one of them. Comparison between on site measured signal strength data and software based reading shows the applicability of the model to this building structure. In the study the measured signal strength was for a wireless access point which was working as a transmitter (Tx) and a Laptop WLAN card was working as a receiver (Rx). The Netstumbler software was used to detect the access point signal and measuring the signal strength. The used devices and software are very cost-effective and there was no need for expensive equipment for conducting the whole study which is a positive side for this study Indoor Wave Propagation Models; Path Loss and Linear Attenuation Models; Wireless Propagation Models I. INTRODUCTION Indoor propagation loss depends mainly on the geometry and materials of the buildings walls. The structural features and interior contents determine the propagation characteristics of indoor environments. The prediction models can be either empirical (also called statistical) or theoretical (deterministic), or a combination of these two. While the empirical models are based on measurements, the theoretical models deal with the fundamental principles of radio wave propagation phenomena [1] [2] [3]. In the empirical models, all environmental influences are implicitly taken into account regardless of whether they can be separately recognized [4] and based on statistics seems to be the most efficient approach, since there is no need of precise definition of the building interiors [5][6]. This is the main advantage of these models. Usually the software tools used to design WLAN system is difficult to use because, it needs a huge amount of input data and some of them depend on parameters that are computed for environments that differ from our environment. The deterministic models have several disadvantages. First, the topographical and building data is always tied to a particular site thus a huge amount of data is required in order to obtain a comprehensive set of propagation environments' model. Also, some materials are a mixture of unknown components, for which no electromagnetic measurement values are available. The amount of pre- processing required makes it slow [1][3]. Second, they are usually computationally intensive, especially when the environment is complex. Thus, detailed physical characteristics of the simulated environment must be known beforehand which is often time-consuming and impractical [1]. In the other hand empirical models can fail in irregular indoor situations where more precise site-specific model should be used, e.g. ray tracing. Example of irregular indoor environment is the small shielded chamber inside a room [6]. The advantages of the empirical approach (which this work is based on) are its very fast processing, simple input is needed, and the formulas are very easy to apply [3] [7]. In Iraq most of the buildings are concrete based. Walls are mostly constructed from cement blocks. In this work a several ways for Multi Walls Propagation Model are tested in concrete building and then we modify the Multi-walls model to be closer to the results obtained from the previous section. This type of building differ the other building which the previous work made. II. EMPIRICAL PATH LOSS MODELS The empirical model expressed in a form of simple mathematical equations which give the path loss as the output. The equations are obtained by fitting the model to measurement results. Empirical models help in reducing computational complexity as well as increasing the accuracy of the predictions [2]. The propagation loss between any point and the transmitter can be expressed with a simple distance dependent equation [3]. 325