Indoor radio propagation channel

In this tutorial survey the principles of radio propagation in indoor environments are reviewed. The channel is modeled as a linear time-varying filter at each location in the three-dimensional space, and the properties of the filter's impulse response are described. Theoretical distributions of the sequences of arrival times, amplitudes and phases are presented. Other relevant concepts such as spatial and temporal variations of the channel, large-scale path losses, mean excess delay and RMS delay spread are explored. Propagation characteristics of the indoor and outdoor channels are compared and their major differences are outlined. Previous measurement and modeling efforts are surveyed, and areas for future research are suggested. >

The indoor radio propagation channel

Qualitative models are presented that predict the effects of walls, office partitions, floors, and building layout on the 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, 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. 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 are accurate to within 6 dB for a majority of locations in a building. >

914 MHz path loss prediction models for indoor wireless communications in multifloored buildings

This article's goal is to provide an in-depth understanding of the principles of FSMC modeling of fading channels with its applications in wireless communication systems. While the emphasis is on frequency nonselective or flat-fading channels, this understanding will be useful for future generalizations of FSMC models for frequency-selective fading channels. The target audience of this article include both theory- and practice-oriented researchers who would like to design accurate channel models for evaluating the performance of wireless communication systems in the physical or media access control layers, or those who would like to develop more efficient and reliable transceivers that take advantage of the inherent memory in fading channels. Both FSMC models and flat-fading channels will be formally introduced. FSMC models are particulary suitable to represent and estimate the relatively fast flat-fading channel gain in each subcarrier.

Finite-state Markov modeling of fading channels - a survey of principles and applications

The most recent FCC ruling proposes relying on a database of incumbents as the primary means of determining white space availability at any white spaces device (WSD). While the ruling provides broad guidelines for the database, the specifics of its design, features, implementation, and use are yet to be determined. Furthermore, architecting a network where all WSDs rely on the database raises several systems and networking challenges that have remained unexplored. Also, the ruling treats the database only as a storehouse for incumbents. We believe that the mandated use of the database has an additional opportunity: a means to dynamically manage the RF spectrum. Motivated by this opportunity, in this paper we present SenseLess, a database driven white spaces network. As suggested by its very name, in SenseLess, WSDs obviate the need to sense the spectrum by relying entirely on a database service to determine white spaces availability. The service, using a combination of an up-to-date database of incumbents, sophisticated signal propagation modeling, and an efficient content dissemination mechanism ensures efficient, scalable, and safe white space network operation. We build, deploy, and evaluate SenseLess and compare our results to ground truth spectrum measurements. We present the unique system design considerations that arise due to operating over the white spaces. We also evaluate its efficiency and scalability. To the best of our knowledge, this is the first paper that identifies and examines the systems and networking challenges that arise from operating a white space network, which is solely dependent on a channel occupancy database.

/pdf/senseless-a-database-driven-white-spaces-network-1uzvffk0c4.pdf

SenseLess: A database-driven white spaces network

Results of measurements at 917 MHz, performed mainly in two large buildings of similar design, are presented, and by an empirical attenuation model based on estimates of transmission, refraction, and diffraction phenomena occurring in the transmission path is elaborated. The modeling fits the data with +or-2 dB for 68% of the 729 measurements, the standard deviation between measurements and prediction being slightly less than 3 dB. >

Measurement and modeling of propagation losses in a building at 900 MHz

A series of error sequence measurements in a typical mobile radio channel has been conducted to study the time distribution of transmission errors. E.N. Gilbert's (1960) and B.D. Fritchman's (1967) digital communication channel models are shown to describe adequately the observed error bursts occurring in the mobile radio channel. An estimation method based on the gradient algorithm is proposed for computing the parameters values of both models from the experimentally derived error distributions. A digital mobile radio channel simulator based on Gilbert's and Fritchman's models with the parameter values as estimated using the gradient technique is presented. >

Estimation of Gilbert's and Fritchman's models parameters using the gradient method for digital mobile radio channels

A number of statistical models are available in the literature for the prediction and the calculation of transmission loss, but the main differences between them as well as their usefulness in a particular situation is not easy to assess. In this article, the experimental results of Okumura, as seen through the empirical expression derived by Hata, are compared with the models of Egli, Edwards and Durkin, Blomquist and Ladell, and Allsebrook and Parsons. Comparisons are made for the case of an open region and flat terrain, first without and then with inclusion of a statistical estimation of diffraction losses due to terrain in the models of Blomquist and Ladell, Edwards and Durkin, and Allsebrook and Parsons. The study is also extended to cover the case of irregular terrain and urban areas. The method proposed by Hata, based on Okumura's results, and Allsebrook and Parsons' model, which provides an easy way to take into account the influence of buildings are the most complete and it is suggested to use them with the inclusion, as required, of an estimation of diffraction losses due to terrain. As a conclusion, experimental propagation loss measurements taken in the Ottawa region at 910 MHz are presented and are found to fall very nicely in the range predicted by the above-mentioned methods.

Propagation loss prediction: A comparative study with application to the mobile radio channel

Propagation loss measurements taken in the Ottawa region in the 900-MHz frequency band are reported and discussed. Significant statistical parameters for a mobile radio channel, such as the mean, the standard deviation of the signals, the level crossing rates and the fading distance, are presented. The signal is first transformed from a time scale to a distance scale; it is then separated into slow and rapid variation components, a low-pass filter with a cutoff point corresponding to 0.125 cycle per wavelength being used to estimate the slow variation component. The statistical analysis of the rapid variation is related to the Rice probability law and to a direct-component-to-multipath-component ratio. For the medium-density urban area under consideration, this ratio is shown to change from around 5 dB to around 9 dB as one moves from medium-density urban to the surrounding open areas. >

https://ieeexplore.ieee.org/iel1/25/1340/00031125.pdf

Statistical modeling of the received signal envelope in a mobile radio channel

A statistical characterization of transmission errors for digital mobile radio links at 910 MHz in different types of urban areas is presented. Error sequences for messages of 2-s duration at a nominal rate of 20-kb/s for binary-phase-shift-keying (BPSK) demodulated transmissions have been obtained and characterized by Fritchman's channel model, including one error state and two to four error-free states. In the data analyzed, no trend has been observed in the Fritchman parameter as a function of the type of area or of vehicle speed. Typical Fritchman's parameters are established for low and intermediate error rate channels (on the order of 10/sup -3/ and 10/sup -2/ error rates) and for higher error rate channels. Results are also presented for a limited sample of quadrature-phase-shift-keying (QPSK) demodulated 40-kb/s transmissions. >

/pdf/characterization-of-error-sequences-in-uhf-digital-mobile-41sn5rl7r9.pdf

M. Lecours

Papers

Measurement and modeling of propagation losses in a building at 900 MHz

Estimation of Gilbert's and Fritchman's models parameters using the gradient method for digital mobile radio channels

Propagation loss prediction: A comparative study with application to the mobile radio channel

Statistical modeling of the received signal envelope in a mobile radio channel

Characterization of error sequences in UHF digital mobile radio channels