RF Propagation Research Articles

RF Propagation in Indoor Environment at WiMAX Band of 3.5 GHz

The purpose of this study is to characterize the indoor channel for IEEE 802.16 (WiMAX) at 3.5 GHz frequency band. This paper presents a channel model based on measurements conducted in commonly found scenarios in buildings. These scenarios include narrow corridor, wide corridor (a passage) and semi open corridor. Path loss equations are determined using log-distance path loss model and a Gaussian (Normal) or Rayleigh fading. Sometimes a combination of both fadings takes place. A numerical analysis of the measurements in each scenario was conducted, and the study determined equations that described path loss for each scenario. Propagation loss for a 20 MHz bandwidth is given. Our contribution is to show for the first time that indoor fading can be represented by Normal, Rayleigh or a combination of both.

IEEE 802.11s Wireless Mesh Networks for Last-Mile Internet Access: An Open-Source Real-World Indoor Testbed Implementation

Due to their easy-to-deploy and self-healing features, WMNs (Wireless Mesh Networks) are emerging as a new promising technology with a rich set of applications. While the IEEE standardization of this new technology is still in progress, its main traits are already set, e.g., architecture and MAC routing. WMNs are attracting considerable research in academia and industry as well, but the lack of open-source testbeds is restricting such a research to simulation tools. The main problem with simulation tools is that they do not reflect the complexity of RF propagation, especially in indoor environments, of which IEEE 802.11s WMNs are an example. This paper presents an open-source implementation of an indoor IEEE 802.11s WMN testbed. The implementation is transparent, easy-to-deploy, and both the source code and deployment instructions are available online. The implementation can serve as a blueprint for the WMN research community to deploy their own testbeds, negating the shortcomings of using simulation tools. By delving into the testbed implementation subtleties, this paper is shedding further light on the details of the ongoing IEEE 802.11s standard. Major encountered implementation problems (e.g., clients association, Internetworking, and supporting multiple gateways) are identified and addressed. To ascertain the functionality of the testbed, both UDP and TCP traffic are supported and operational. The testbed uses the default IEEE 802.11s HWMP (Hybrid Wireless Mesh Protocol) routing protocol along with the default IEEE 802.11s Airtime routing metric.

Measurements in harsh RF propagation environments to support performance evaluation of wireless sensor networks

PurposeThe purpose of this paper is to describe common methods for evaluating the performance of wireless devices such as wireless sensors in harsh radio environments.Design/methodology/approachThe paper describes how measurements of real‐world propagation environments can be used to support the evaluation process, then presents representative measurement data from multipath environments where sensor networks are likely to be deployed: a fixed‐infrastructure, process‐control environment (here an oil refinery), and a heavy industrial environment (here an automotive assembly plant).FindingsResults on the characterization of multipath in the propagation channel are summarized and how these results may be used in the performance evaluation of sensor networks is discussed.Originality/valueThe paper describes measurement results from environments where little open‐literature data exists on point‐to‐point propagation, specifically high‐multipath environments. These highly reflective scenarios can present difficulties for deployment of sensor networks.

Hybrid Distributed Instrumentation Network for Integrating Meteorological Sensors Applied to Modeling RF Propagation Impairments

Rainfall rate is the main cause of fades in the frequency bands above 10 GHz. To optimize the planning of satellite and terrestrial radio communication systems operating on these frequency bands, it is essential to have a detailed knowledge of the temporal and spatial distributions of the rainfall rate. For this reason, it is necessary to develop experimental networks, which provide adequate data to study, prevent, and compensate the rain fade. In this paper, an experimental instrumentation network is presented. This network comprises weather stations that are capable of measuring rainfall rate, temperature, and humidity; a weather radar; and three radio links. This paper first introduces the rationale and the state of the art in meteorological sensors and describes the experimental network for automatic data acquisition as a distributed process system. The design of the experimental network is explained in detail. Finally, the interest in millimeter wavelength for broadband applications is outlined, and some research lines from the collected data are presented.

Upper tail of distribution of power received from many sources

Consider the total power received from many identical, randomly scattered RF sources in a plane (that is, in Poisson fashion). If RF propagation follows a power law model with exponent α>2, the right tail of the probability distribution approximately follows a Pareto distribution with exponent 2/α.

A Mode Based Model for Radio Wave Propagation in Storm Drain Pipes

In this paper, we analyze the behavior of Storm Drain Pipes (SDPs) as multi- mode leaky waveguides for radio wave transmissions between 2.4{2.5GHz within the Industrial, Scientiflc and Medical (ISM) band. The previous research on analyzing RF propagation inside underground structures focused on auto, railroad, subway, mine and sewer tunnels of diameters greater than 1.05m. Our research provides a novel contribution by characterizing RF propaga- tion inside narrow SDPs of diameter as low as 0.30m. Understanding the behavior of SDPs as communication channels is not only important for designing portable military communication equipment, but also for other civil applications. We study the modal content of propagating waves and derive a mode based model (MBM) for predicting the received power. Empirical data gathered at selected sites in Charlotte, North Carolina is used to validate the MBM. Based on analysis of nonlinear curve fltting through the measured data, close agreement is found between the predicted and measured power. We also highlight the requirement of further work to improve the fltting of measured data with the predicted results.

Interference and Regulatory Aspects of GNSS Pseudolites

Galileo, the European Satellite Navigation System, is currently under development. Even before first satellites of the constellation are launched, Galileo signals will be provided through ground based Navigation Signal Generators for the investigation of signal performance and characteristics. These low power devices, called Pseudolites (Pseudo-Satellites), will transmit signals equivalent to those which are transmitted by the in-orbit satellites. However, from the regulatory point of view they are not providing Radionavigation Satellite Service (RNSS) as defined in International Tele communication Union (ITU) Radio Regulations but "something else". This has to be investigated, because it is expected that Pseudolites (PLs) will, beyond their roles to evaluate signal performances in the early phase of the program, significantly extend the navigation service availability into areas where the critical RF propagation of direct line of sight to satellites is blocked. Sound experience over many years has already been gained worldwide through the research with GPS Pseudolites. Galileo will introduce sophisticated and ambitious new signal schemes initiating new designs for innovative Pseudolite solutions. Old and new signals will coexist for many years to come. Currently there are various projects ongoing to develop Pseudolites for Galileo. A practicable regulatory framework, taking specific operational conditions of Pseudolites into account, has to be developed by the regulatory authorities to encourage the implementation of Pseudolite-networks on one side. But, at the same time, it is important to set strict rules for the implementation to avoid harmful interferences created by Pseudolites to RNSS and other radio receivers operated in the vicinity of a Pseudolite-network. The creation of a clear regulatory framework has eventually to provide the planning security for Pseudolite-network operators and RNSS- provider considering service guarantees. Pseudolites, as well as other means to achieve a nearly seamless service availability have been an essential element of the Galileo system architecture from its early system studies. In the Galileo architecture, PLs are defined as a sub-group of the so-called Local Elements. Technically speaking, Pseudolites are low power transmitters that either transmit or repeat (Synchrolites) RNSS-equivalent signals on the same frequency bands allocated to RNSS as defined in the ITU-R Radio Regulations. The creation of a regulatory framework for the operation of Pseudolites, which is yet undefined, has recently received a growing attention in the spectrum engineering working groups and frequency management groups of the European Conference of Postal and Telecommunications Administrations (CEPT). So far, PLs are operated under experimental license only. In order to prepare inputs to this process, the performance requirements in typical application scenarios have been investigated. This paper presents initial considerations and preliminary results of investigations performed on the interference properties of general GNSS Pseudolites. It proposes a concept for typical scenarios that can serve as generic Pseudolite network architectures to be considered in the on-going process to determine a regulatory framework for future operational networks.

Method to estimate infrared and radio-frequency synergy

A method is developed to study the synergism that can exist between horizon search radar and IR search and track (IRST) systems onboard ship under various meteorological conditions within the marine surface layer (<50 m). The method shows that four operational regions can be defined through the effect of the air-sea temperature difference and the air-sea water vapor pressure difference to produce sub- or superrefractive IR and rf propagation. It is also shown that no conditions can exist such that both IR and rf have subrefractive propagation. Applying the method to many meteorological observations shows that the method works quite well; however, it also indicates that there is not necessarily a detection range advantage to having both an optical and a radar system. However, the advantages to having an optical system are not solely dependent on its range performance. The precision with which an optical system can provide target track parameters, its ability to maintain track when radar systems cannot, and its ability to identify targets are synergisms that are quite significant.

Global Modeling of Magnetized Capacitive Discharges

Capacitive reactors for semiconductor processing must simultaneously balance many physical phenomena with engineering constraints to achieve the desired processing properties. Important phenomena include electromagnetic RF propagation, gas ionization, plasma heating, plasma transport, and nonlinear sheath effects. Constraints are driven by process uniformity, radical production, thermal control, and reactor-component lifetime. These phenomena and constraints are often modeled in isolation; however, in a real system, they can interact in ways that are not easily foreseen. It is highly desirable to have global models that can provide relatively quick feedback for the proposed modifications to these systems. While an approach based on fundamental physics models is highly desirable whenever possible, the system can quickly become too complicated for quick design evaluations. In this paper, we explore the interaction between several processes by combining fundamental physics models when reasonable, with simplified, heuristic, or even empirical models for processes that are difficult to model from first principles. The goal is to understand the interaction between these processes in a global system without becoming overly encumbered by details in the individual components of the model. We study the effects of static magnetic field on plasma transport and electromagnetic effects arising at high RF frequency. We also change the RF-coupled power and ionization efficiency in a simplified 2-D model geometry to contrast the various effects. We find that discharges with very high frequency and high plasma density can exhibit localized nulls in the RF fields caused by electromagnetic-propagation effects in the sheath region. We find that relatively low static magnetic fields can modify the radial-plasma density profiles. Good agreement is found between the radial-plasma profiles given by the model and those measured in an experiment where the currents in two concentric coils near the plasma are the only variables.

Reviews and Abstracts

This book is written as a textbook for both classroom use and as a reference by researchers and professionals. It provides a rare view of wireless communications that is very well grounded in electromagnetics. There is also a companion Web site, http://www.wiley.com/go/molisch, that contains lecture slides, additional exercises, a solution manual, and appendices containing additional technical material and mathematical derivations of selected theorems. The book is broken into five parts. Part 1 provides a broad survey and introduction to wireless communications systems. Part 2, entitled "Wireless Propagation Channels," contains chapters on RF propagation fundamentals, statistical channel modeling, wideband and directional channel characterization, a survey of channel-modeling techniques, channel sounding, and antennas. Part 3, "Transceivers and Signal Processing," contains chapters on practical wireless transceivers, pulse and digital modulation, demodulation and bit-error-rate analysis, diversity, channel coding, speech coding, and equalization. Part 4, entitled "Multiple Access and Advanced Transceiver Schemes," contains chapters on the principles of cellular networks, spread-spectrum systems, orthogonal frequency-division multiplexing (OFDM), and multi-antenna systems. Part 5, "Standardized Wireless Systems," concludes the book with chapters surveying GSM, IS-95, CDMA 2000, WCDMA, and standards for wireless local-area networks. The book is an extremely comprehensive textbook that will appeal to students and researchers in both the communications and electromagnetics disciplines.

Measurement-based models of delivery and interference in static wireless networks

We present practical models for the physical layer behaviors of packet reception and carrier sense with interference in static wireless networks. These models use measurements of a real network rather than abstract RF propagation models as the basis for accuracy in complex environments. Seeding our models requires N trials in an N node network, in which each sender transmits in turn and receivers measure RSSI values and packet counts, both of which are easily obtainable. The models then predict packet delivery and throughput in the same network for different sets of transmitters with the same node placements. We evaluate our models for the base case of two senders that broadcast packets simultaneously. We find that they are effective at predicting when there will be significant interference effects. Across many predictions, we obtain an RMS error for 802.11a and 802.11b of a half and a third, respectively, of a measurement-based model that ignores interference.

Digital Signal Processing in a Real-Time Propagation Simulator

The hardware and software interface to a programmable real-time RF propagation simulator is described. First, fading models are reviewed; and next, the digital filter design of the fade spectra filtering is detailed along with the implementation on a floating point digital signal processor (DSP). The hardware system design is given, followed by the application of this system to radio link propagation.

An empirical model for propagation‐loss prediction in indoor mobile communications using the Padé approximant

AbstractThis paper presents a new model for propagation‐loss prediction in indoor mobile communications. It uses the free‐space loss model added to an empiric function (based on the Padé approximant), and a term that describes the signal randomness (typical of the RF propagation). In order to validate this model, a measurement verification was accomplished for a typical five‐floor building of a university. The loss predicted by this model had a mean error of 4.78 dB and a standard deviation of 6.05 dB in relation to the measured data. The formulation of the model does not require accurate information about the environment used in the study, such as the permittivity of the construction materials, layout of the furniture, and so forth, but only needs to be adaptable to any indoor environment. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48:255–261, 2006; Published Online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.21321

RF propagation in finite thickness unidirectional magnetic photonic crystals

This paper presents an analysis of a new class of magnetic photonic crystals (MPCs) constructed from periodic arrangements of available (possibly anisotropic) homogeneous material layers. Earlier, analytical studies of semi-infinite versions of these crystals demonstrated that they exhibit the phenomena of minimal reflection at their interface, large amplitude growth of the harmonic wave within the crystal, and concurrent group velocity slow-down. These characteristics are associated with the so called frozen mode and occur at a specific frequency associated with a stationary inflection point within the Bloch diagram. In this paper, we present a characterization of these phenomena for a practical, finite thickness crystal slab and propose a realizable combination of materials consisting of available ferrite and dielectric media. The existence of significant wave amplitude growth and slow down are verified for materials with realistic losses. In addition, we identify and characterize the bandwidth of the magnetic photonic crystals and examine its relationship to the amplitude growth.

Dependence of the equatorial anomaly and of equatorial spread F on the maximum prereversal E × B drift velocity measured at solar maximum

The relation of equatorial bubbles to the equatorial anomaly is important because scintillation that is most disruptive to transionospheric RF propagation occurs when it passes through the intersection of the two. However, measurement of the relation between the two and of the electric field from which both arise is difficult because of large separations in space and time. This first attempt to perform these measurements employs a latitudinal array of ionospheric sounders spanning 0° to 40° dip latitude (DLAT) in the Western American sector. Measured on each day of a solar maximum year are the following: (1) the maximum electron density of the postsunset equatorial anomaly, Ne, at 16° and at 20.3° DLAT at 2100 LT, the time when the anomaly crest is at its maximum latitude; (2) equatorial spread F (ESF), detected by the occurrence of macroscopic bubbles and of bottomside spread F (BSSF), the latter recorded at levels of none, weak and strong; (3) Kp averaged over the 6 hours before sunset. Ne and ESF are considered functions of the maximum prereversal F layer drift E × B drift velocity measured by the Jicamarca incoherent scatter radar also during solar maximum and at the same longitude. Parameters are averaged over two levels of Kp for the three seasons, the E months (March, April, September, and October), D months (November–February), and J months (May–August) to yield the following results: (1) Ne measured at 16°, at 20.3° DLAT or at the anomaly crest are linearly dependent on maximum E × B drift velocity. (2) Occurrence of each level of ESF increases with Ne approximately linearly during the E and J months but not during the D months. (3) ESF occurrence is dependent on and increases approximately linearly with maximum E × B drift velocity during the E and J months. During the D months this dependence is absent. Except for the D months, these results indicate that scintillation increases with maximum prereversal E × B drift velocity: at L‐band at the bubble‐anomaly intersection because bubble occurrence increases, Ne increases, and the latitudinal extent of the anomaly increases; and at VHF/UHF near the equator because the occurrence of strong BSSF increases.

Glow discharge processing in the liquid crystal display industry

The active matrix display industry is rapidly presented. The most challenging aspect for plasma source design lies in the substrate size which is now entering the 1–2 m range. This paper focuses on the conventional planar RF capacitor at 13.56 MHz. A detailed analysis of the local perturbation due to a hole in the metal susceptor illustrates the process effects of various plasma microscopic parameters. It appears that not only the process rate must be kept uniform, but also the ion bombardment. It is also shown that very wide capacitive reactors no longer follow some classical rules: (1) plasma RF conductivity is limited, its propagation is shown to be described by a telegraph equation, in agreement with numerical modelling and electrostatic measurements, (2) the RF wavelength is no longer infinite compared to the dimensions, this leads to standing waves. The presence of the plasma is shown to worsen the effect by shortening the RF propagation wavelength.

Dependence of equatorial bubbles and bottomside spread F on season, magnetic activity, and E × B drift velocity during solar maximum

Equatorial bubbles occur sporadically, so that the resulting scintillation that disrupts transionospheric RF propagation is unpredictable. Furthermore, this randomness prevents the systematic observation of the formation of bubbles necessary for making progress in their prediction. However, recent results indicate that a necessary condition for bubble formation is bottomside spread F (BSSF); that BSSF is a function of the F region dynamo electric field; and that this field is dependent on magnetic activity and on season. This work measures these conditions using an array of ionospheric sounders in conjunction with other spread F observations, all of which are ground‐based, in the western American sector, during solar maximum. Three spread F levels are observed: total BSSF and strong BSSF, both measured near the dip equator, and macroscopic bubbles measured at the equatorial anomaly. The three independently measured thresholds form a hierarchy in which macroscopic bubbles are a subset of strong BSSF, which is a subset of total BSSF. Each level decreases as a linear function of Kp averaged in the 6 hours preceding observation during March, April, September, and October, and during November–February; however, during May–August the levels are small and are independent of Kp. As a result, the probability of occurrence of each level, most importantly of macroscopic bubbles, is a quantitative function of Kp and season. The seasonal variation of Kp dependence indicates that the suppression of irregularities results from the decrease in the maximum prereversal vertical drift velocity of the equatorial F layer and therefore from the decrease in the eastward electric field.

The equatorial anomaly: Its quantitative relation to equatorial bubbles, bottomside spread F, and E×B drift velocity during a month at solar maximum

The scintillation that is most disruptive to trans‐ionospheric RF propagation occurs when an equatorial bubble intersects the maximum electron density of the equatorial anomaly. This paper reports the first systematic observational study of the important interrelation between bubble and the anomaly together with the maximum pre‐reversal E × B drift velocity, and strong bottomside spread F (BSSF), which is a necessary condition for bubbles. An array of ionospheric sounders located near 75° W longitude measures latitudinal profiles of NmF2 at hourly intervals through 0°–40° dip latitude (DLAT) and 1800–0300 LT during a continuous period of 30 days at equinox and solar maximum. The anomaly is highly variable from day to day, but at 2100 LT, the time of its highest latitude, crest latitude and magnitude increase and decrease together, a relation that is linear above a threshold with coordinates of 38 × 105 el/cm3 and 15.4° DLAT. This threshold is important also because it corresponds to the maximum drift velocity of 50 m/s, and because above it nearly all bubbles are observed, directly as macroscopic bubbles and indirectly as strong BSSF. The importance to C/NOFS and other satellites is that maximum E × B drift, crest NmF2 and crest DLAT are in apparent one‐to‐one correspondence above this threshold, so that measurement of any one of the three implies measurement of the other two. Furthermore, any such measurement that exceeds the threshold indicates that bubbles can occur, whereas one that falls below the threshold indicates that they cannot.

On optimal cell planning: Case study for a DCS 1800 system

AbstractMicro and pico cell planning strategies are adopted in personal communication systems (PCS) in order to increase their capacity. The usage of the upper UHF band in combination with greater bandwidth is already proposed by telecom engineers in order to achieve the promised service quality and data rates. These strategies are characterized by an increased number of cells in specific geographical areas with the corresponding operating base transceiving stations (BTS) located at relatively low heights above the street level. In this case, the cell planning procedure in linear streets under line‐of‐sight (LOS) conditions needs further study concerning the technical characteristics of the PCS.In this paper, the propagation characteristics of a DCS 1800 system are investigated on a theoretical and experimental basis in a specific geographical area (center of Patras City in Northern Pelloponesse). An improved RF propagation model is proposed in order to determine the propagation path losses occurring under certain multipath fading conditions. Hence an optimum determination of a system's cellular area can be achieved. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Wireless Andrew: building a high speed, campus-wide wireless data network

Carnegie Mellon University (CMU) has a major program to create a high speed wireless network, known as Wireless Andrew. The first Phase of this network has been operational for over a year and the second Phase, to upgrade this to IEEE 802.11 standard technology, has begun. The Wireless Andrew network uses wireless local area network technology, utilizing spread spectrum in the ISM band. The purpose is not only to support wireless research but also to create a campus-wide mobile computing laboratory. The paper shows the challenge of designing and managing large scale wireless networks. The examples show the differences experienced in wireless versus wireline networks due to the nature of mobility versus static components, the nature of RF propagation versus wireline connection, and the difference in sophistication of tools because of the different place in the product development cycle. The paper describes the lessons learned at completion of the first phase including: installation design issues, issues of RF interference and data throughput, the unique problems of wireless network management, and the release of the system. The paper goes on to describe lessons learned during the first year of operation of the research network. It then discusses experience so far in Phase Two, to create an operational utility for use of all students, faculty, and staff for educational, research, and administrative applications.