Abstract-Quantitative models are presented that predict the effects of walls, office partitions, floors, and building layout on path loss at 914 MHz. The site-specific models have been developed based on the number of floors, partitions and concrete walls between the transmitter and receiver, and provide simple prediction rules which relate signal strength to the log of distance. The standard deviation between measured and predicted path loss is 5.8 dB for the entire data set, and can be as small as 4 dB for specific areas within a building. Average floor attenuation factors (FAF), which describe the additional path loss (in decibels) caused by floors between transmitter and receiver are found for as many as four floors in a typical office building. Average floor attenuation factors are found to be 12.9 and 16.2 dB for one floor between the transmitter and receiver in two different office buildings. For same-floor measurements, attenuation factors (AF) are found to be 1.4 dB for each cloth-covered office partition and 2.4 dB for each concrete wall between transmitter and receiver. Path loss contour plots for measured data are presented. In addition, contour plots for the path loss prediction error indicate that the prediction models presented in this paper are accurate to within 6 dB for a majority of locations in a building. I. INTRODUCTlON BJECTS that surround transmitters and receivers 0 severely affect the propagation characteristics of any radio channel. The performance of in-building high capacity wireless communications is limited by the propagation characteristics. Thus, it is important to understand how the physical surroundings impact the propagation environment. Several researchers have measured radio waves in buildings and statistically modeled their results [1]- [9]. A summary of path loss, narrow-band fading statistics, and root mean square (rms) delay spread in many different building types is given in [lo]. In this paper, we first present statistical analyses of 914 MHz narrow-band path loss measurements inside four buildings, and then classify the measurements based on the physical surroundings. The measured buildings include a grocery store, a retail department store, and two multistory office buildings. A statistical model of the simple form d" (see (2)) is used to relate average path loss to the log of distance where Values of the mean path loss exponent n are found for each building and all four buildings combined. In multifloored buildings, we find that more accurate prediction is possible when the parameter n is viewed as a function of the number of floors between transmitter and receiver. We also develop an alternative path loss model ( (5)) for multifloor buildings to quantify the additional path loss caused by multiple floors between transmitter and receiver. For measurements in the office buildings when the transmitter and receiver are located on the same floor, we quantify average path loss caused by cloth-covered plastic office partitions and concrete walls between the transmitter and receiver. We assume free space propagation with distance and consider additional path loss to be caused by the physical obstructions that lie directly between the transmitter and receiver ( (8)). This provides a tractable physical propagation model that is shown to be more accurate than a generic statistical model ((2)) that considers only the distance between the transmitter and receiver terminals, and not site-specific information. Contour plots of locations of equal path loss for a fixed base transmitter are presented for the two office buildings. The models in this paper are used to predict the path loss at the measurement locations. The differences between the measured and predicted path loss are used to develop path loss prediction error contour regions for the office buildings. Section I1 describes the measurement procedure and the four measured buildings used to produce the models in this paper. Section I11 describes the important site-specific building parameters used to develop the models. Section IV presents the measured data and shows the best fit for three different in-building path loss models. Section V shows path loss contour for measured data and error contour regions for the difference between the measured path loss and the path loss predicted from site-specific models given in Section IV. Sections VI and VI1 conclude with a summary of results and future work. MEASUREMENT PROCEDURE AND LOCATIONS Narrow-band (CW) signal strength measurements were made at 914 MHz with a system nearly identical to the one 0018-926X/92$03.00 0 1992 IEEE
Propagation Model Based REF : RSSI is related to the distance between transmitter and receiver.
914 MHz path loss prediction models for indoor wireless communications in multifloored buildings
IEEE Transactions on Antennas and Propagation
Physics