Radio Propagation Characteristics Research Articles

무선 AP 위치 예측을 위한 전파특성 분석

본 논문에서는 GPS 수신기가 제공되지 않는 환경에서 무선 AP 위치 추적을 위한 방안을 마련하기 위해 AP 장비로부터 방사되는 무방향성 전파의 특성을 분석하였다. 무선 단말로부터 추적되는 AP장비나 고정된 AP 장비로 추적 가능한 무선 단말의 위치를 추적하기 위해서는 거리에 따른 수신 전력의 분포 환경을 분석하는 것이 무엇보다 중요하다. 따라서 본 논문에서는 2.4GHz 대역의 무선 전파 특성을 실내 및 실외 환경에서 거리에 따라 영향정도 및 특성을 분석하고 이를 위치 예측에 활용하였다. In this paper, it is analyzed propagation distribution characteristics of radio wave, which is radiated on all sides from Access Point device for estimating scheme of wireless AP without GPS receiver environment. To tracking AP device is traced from wireless terminals and wireless terminal is traced from fixed AP devices, above all it is important to analysis the characteristics of receiving power in according to distance. Therefore in this paper, radio propagation characteristics of 2.4GHz wave is analyzed effect extent and quality in according to distance in doors and out doors, and utilized to location estimation.

Environment-Aware Location Estimation in Cellular Networks

We propose a novel mobile positioning algorithm for cellular networks based on the estimation of the radio propagation environment. Since radio propagation characteristics vary in different environments, knowing the environment of the mobile user is essential for accurate Received Signal Strength-(RSS-) based location estimation. The key feature of our method is its capability to estimate the environment of the mobile user using machine learning techniques and to utilize this information for enhancing RSS-based distance calculations. The proposed algorithm, namely, EARBALE, has been evaluated using field measurements collected from a GSM network in diverse geographic locations. Our approach turns out to be significantly beneficial, enhancing estimation accuracy, and thereby enabling high-performance mobile positioning in a practical and cost-effective manner. Additionally, it is computationally light-weight and can be integrated onto any RSS-based algorithm as an enhancement add-on.

Path-Loss Prediction Models for Intervehicle Communication at 60 GHz

Propagation path losses affecting intervehicle communication (IVC) at 60 GHz are presented. In order to examine the radio-propagation characteristics in the IVC system, in the first stage of our investigation, we have carried out propagation tests between two vehicles communicating in a line-of-sight (LOS) situation at fixed positions on a smooth surface paved with asphalt, which is the normal communication condition. Furthermore, the non-LOS (NLOS) situation with up to three intermediate vehicles, which can cause an obstruction, has been conducted. To construct path-loss models in NLOS cases, the uniform theory of diffraction technique was applied to the calculation of waves propagating through the intermediate vehicles. The propagation path models were derived from the measured results. In the second stage, a path-loss prediction formula was derived by statistically processing the data that had been calculated using the propagation path model. The propagation tests between the vehicles in motion confirm that the path-loss prediction formula is very useful when the communicating vehicles are moving, and it is therefore suitable for designing the cells that form the IVC.

도심 환경을 고려한 마이크로파 대역 MIMO 전파 채널 측정 시스템에 관한 연구

본 논문은 국내 도심 환경을 고려한 마이크로파 대역 다중 안테나 전파 채널 특성을 연구하기 위한 광대역 MIMO 채널 측정 시스템 구축과 성능 확인을 위한 시험 측정을 기술하였다. 차세대 이동 통신을 고려하여 채널 측정 시스템은 고속의 스위칭 방식과 100 MHz의 광대역 채널 대역폭을 지원하도록 설계되었으며, <TEX>$4{\times}4$</TEX> MIMO 채널 측정을 지원한다. 시스템 성능 확인 및 교정을 위한 시험 측정을 분당 빌딩 밀집 지역에서 실시하였다. 3.7 GHz와 8 GHz의 도심 LOS 구간의 시험 측정 데이터를 분석한 결과, 3.7 GHz 및 8 GHz 대역에서의 광대역경로 손실 지수는 각각 1.79와 1.76으로 측정되었으며, 평균 RMS 지연 확산은 각각 200 ns과 42 ns로 측정되었다. 시험 측정 결과, 본 MIMO 채널 측정 시스템은 실외 도심 환경에서 커버리지와 신호대 잡음비 및 채널 용량 등의 마이크로파 대역 전파 특성 연구에 적합함을 확인하였다. In this paper, the development of wideband MIMO channel sounder and a pilot measurement result is described for research on the multi antenna radio propagation characteristics considering urban environment at microwave frequencies. We developed <TEX>$4{\times}4$</TEX> MIMO(BW:100 MHz) channel sounder using the high speed switching mechanism and periodic pseudo random binary signals method considering next generation mobile communication system. A pilot measurement campaign at the urban area of Bundang is presented for confirmation of system performance. From the analysis of measurement data, wideband path loss exponent of 3.7 and 8 GHz band is 1.79 and 1.76. Average RMS delay spread is 200 ns and 42 ns respectively. From the experiment results, operation of this measurement system is confirmed considering research for a coverage, SNR and channel capacity in urban environment at microwave frequencies.

Empirical Investigation of the LOS Propagation Characteristics on an Undulating Road for Millimeter Wave Inter-Vehicle Communication

We investigated the radio propagation characteristics for line-of-sight (LOS) inter-vehicle communication (IVC) at 60GHz on an actual road with an undulating surface. Radio propagation tests between two moving vehicles were carried out on a test course. From this, it was found that the measured received power on the actual road and the results calculated for a flat road approximately follow logarithmic normal distributions. To investigate this phenomenon in detail, a propagation test between two stationary vehicles on a road was performed. Furthermore, calculations using geometrical optics taking road undulation into consideration demonstrated that undulation in the road can cause variations in the received power that follow a logarithmic normal distribution. Finally, the received power for moving vehicles on an undulating road was calculated using the model.

Location estimation using received signal power and maximum likelihood estimation in wireless sensor networks

AbstractThis paper considers the sensor network based on IEEE 802.15.4, and proposes a method in which a probabilistic model of wireless propagation characteristics in a real environment is constructed, and the node position is estimated by maximum‐likelihood estimation using the model. The performance of the proposed method is evaluated by simulation and position estimation experiments based on the probabilistic model obtained from the actual indoor measurement. It is shown that the proposed method is useful for indoor personnel location management. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(12): 62–72, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20359

Energy-Efficient Localized Topology Control Algorithms in IEEE 802.15.4-Based Sensor Networks

Sensor networks have emerged as a promising technology with various applications, where power efficiency is one of the critical requirements. The recent IEEE 802.15.4 standard offers a promising platform for wireless sensor networks. Since each node can act as a coordinator or a device in the IEEE 802.15.4 standard, 802.15.4-based sensor networks have various possible network topologies. To reduce power consumption, in this paper, we try to construct network topologies with a small number of coordinators while still maintaining network connectivity. By reducing the number of coordinators, the average duty cycle is reduced and the battery life is prolonged. Three topology control algorithms are proposed in this paper. Self-pruning (SP) is the simplest one with O(1) running time and provides the shortest path to the sink node. Ordinal pruning (OP) can significantly improve SP in terms of power saving with O(n) running time. Layered pruning (LP) is a trade off between the first two pruning algorithms with O(radicn) running time and has a slightly higher power consumption than OP. Furthermore, all three algorithms are independent of the physical radio propagation characteristics. Extensive simulations have been performed to verify the effectiveness of the proposed topology control schemes

Geographic Channel Assignment Framework for Broadband Wireless Access Networks

This letter proposes a novel geographic channel assignment (GCA) framework for dynamic channel allocation (DCA) in broadband wireless access networks (BWANs). The proposed GCA scheme is based on the characteristics of radio propagation, which focuses on the relationship between transmission distances and communication parameters, e.g., signal-to-noise ratio (SNR) etc., and uses a signal-aware distance estimation scheme to determinate an appropriate channel for communication. This method significantly increases the capacity of the BWA system. Simulation results show that the GCA framework can yield approximate two times throughput of the IEEE 802.16 standard specifications as well as obtain significantly lower call blocking probability compared with classical channel assignment methods.

14-6 800MHz帯の大空間屋内伝搬特性(第14部門 無線・光伝送1(光・伝送・伝搬))

14-6 800MHz帯の大空間屋内伝搬特性(第14部門 無線・光伝送1(光・伝送・伝搬))

Some experimental and modeling results of widely varying urban environments on train mobile radio communication

AbstractA comparative study of urban mobile radio wave propagation characteristics in the UHF band has been carried out based on the field strength measurements conducted inside a moving train in two widely varying urban environments. Various prediction techniques are employed to compare the observed path losses with those of predicted ones in both the environments. The major fall out of the present study is the modification of Xia's model, which gave better agreement with the observed results. The deviations of the prediction techniques and their suitability have been discussed. Copyright © 2006 John Wiley &amp; Sons, Ltd.

IEEE802.15.4 ESPARSKey (Encryption Scheme Parasite Array Radiator Secret Key)

When the transmission and reception locations of radio waves are different, the correlation of the radio wave propagation characteristics decays quickly. On the other hand, reciprocity of the radio wave propagation holds between two stations that can communicate with each other. Therefore, by making use of the information on the variation of the propagation path, it is possible to generate and share a secret key that cannot be eavesdropped by a third party at a different receiving location. Hence, a secret key generation and agreement system that does not require key management and key distribution can be realized. Also, the ESPAR (Electronically Steerable Parasitic Array Radiator) antenna, under development as a commercial antenna with a variable radiation pattern, can control its directive characteristics by the use of varactor diodes to change the capacitance. Therefore, it is possible to intentionally change the radio propagation characteristics significantly. This paper reports successful test development of a wireless secret key agreement system making use of the fluctuation of the radio propagation characteristics by means of an ESPAR antenna. Further, in a verification experiment using the test system, the key generation success probability was more than 99.998% when a 128-bit secret key was modified every 3 seconds. It is also confirmed by the correlation characteristics with an eavesdropping station that more than 7.19×104 years would be required for the eavesdropping station to decipher the secret key. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(12): 31–44, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20305

Application of Ad-hoc Network Technology to Railway Systems

As tentative mobile networks can be easily constructed using ad-hoc network technology, hopes are high for its application across a range of fields. In this paper, we show the results of basic studies for its application in railway operational systems. First, we propose two application systems that can be constructed using ad-hoc network technology and clarify their transmission characteristics through simulation. We then report the measured values of radio propagation characteristics at varying frequencies suitable for use in ad-hoc networks constructed at stations and waysides. Finally, we introduce a radio propagation characteristics estimation program extended to include calculation of the propagation characteristics between two mobile nodes.

A Random Graph Model of Mobile Wireless Networks

Abstract We propose a time-invariable, integrated model of wireless networks working in hostile environment with obstructions and other factors causing interference. We present a new probabilistic model well suit for analysis of distributed algorithms requiring synchronous communication. The model is based on a random graph with a specific edge probability distribution, which is related to the radio wave propagation characteristics.

Radio link enhancement using an open flexible protocol stack framework

AbstractThis paper explores radio link enhancement utilising dynamic run‐time software download and configuration. In particular, the insertion of virtual medium access control (MAC), hybrid automatic repeat request (ARQ) and compression enhancement layers are considered in this paper. This is made possible with a flexible protocol stack framework, which permits the insertion of protocol layers and configuring them in a platform‐independent manner. A general purpose central processing unit (CPU) environment is used in order to assess performance and power consumption of this proposed approach. The results presented indicate that there are scenarios in which this approach is attractive and that execution environment optimisations for performing generic protocol functions can increase the applicability to more scenarios.Currently protocols, and in particular link layer protocols, are designed to support specific traffic and underlying radio propagation characteristics and network topologies that are expected to be observed in a range of deployment scenarios in a manner that is determined at a system design time. As a result, this leads to many different solutions that are tailored to the particular and quite specific requirements such as short range personal area networks (PAN) based on bluetooth or ultra wide band (UWB), local area networks (LAN) based on 802.11 and of course many wide area cellular networks. These solutions cannot be changed to support traffic characteristics and radio performance observed in scenarios that were not envisaged at the time of standardisation. Hence, many new releases of standards are generated to incorporate these new and often optional features that often cannot be used because not all devices support these features. A flexible protocol stack framework has been proposed to provide the ability to insert and configure new software protocol implementations at run time. The overall benefit of this is that new optional features can be exploited before or without standardisation. In addition, dynamic optimisation can be performed to tailor the protocol configuration to specific scenarios and adapt to the changing radio environment. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Experimental Characterization of Radio Wave Propagation in Hospitals

This paper reports the characterization of radio wave propagation in hospitals. In contrast to other buildings with usual walls, some rooms within hospitals are constructed with special walls that include metallic layers. The structure of the walls depends on the purpose of each hospital room. To consider all the different wall types, measurements were performed in all relevant areas of four hospitals. Rooms, such as operating rooms, X-ray and magnetic resonance tomography (MRT) rooms were taken into account. The measurements were performed at eight discrete frequencies ranging from 42.6 MHz up to 5.2 GHz. In order to investigate accurately the wave propagation properties, several antennas and measurement systems were used. Results show that radio wave propagation characteristics vary from room-to-room. It turned out that it is important to consider the room as a whole when determining the attenuation between adjacent rooms, because a small part of the wall is not enough. In addition to usual wave propagation phenomena such as reflection and transmission, slots and openings give rise to coupling effects through walls containing metallic layers in their structure. The measurement data is useful for hospital designers and hospital engineers.

Measurements and channel characterization at 1.89 GHz in modern office buildings

Indoor radio communication systems have challenged scientist's to understand the propagation of radio signals within buildings. A prerequisite to the design of these systems is knowledge of indoor radio propagation characteristics, and the information concerning the building's interior structure that strongly affects the signal propagation. This paper contributes to the modeling of propagation losses, and measurement techniques and methods in modern office buildings, by presenting measurement results at 1.89 GHz (DECT European Frequency). Narrowband propagation measurements were conducted within the Hellenic Telecommunication Organization premises (OTE building) in Athens, Greece. We examine the indoor signal behavior, considering site-specific information for both single-floor (including LOS and NLOS scenarios) and multi-floor cases, extracting the indoor radio channel characteristics. Path-loss factors ranged from 1.6 to 2.0 for LOS cases and 2.1 to 3.0 for NLOS cases, both for single-floor topographies. In multi-floor conditions the decay factor is up to 6.7. The composed prediction for the entire data set gives a mean error and standard deviation of 4.5 and 3.0 dB respectively. Copyright © 2003 AEI.

Development of Methods for the Calculation of Radio Propagation Characteristics in the Railway Environment

In recent years, radio telecommunications have become increasingly important for railway systems. We have studied methods for the calculation of radio propagation characteristics along railway lines, and proposed a new calculation method based on that of ORE A 133. We have also confirmed that the proposed method can calculate the radio signal strength along railway lines at sufficiently high precision in comparison with the conventional method. Furthermore, we have developed a radio propagation characteristics calculation program for easy application of the new method.

A new statistical model for site-specific indoor radio propagation prediction based on geometric optics and geometric probability

The ray-tracing (RT) algorithm has been used for accurately predicting the site-specific radio propagation characteristics, in spite of its computational intensity. Statistical models, on the other hand, offers computational simplicity but low accuracy. In this paper, a new model is proposed for predicting the indoor radio propagation to achieve computational simplicity over the RT method and better accuracy than the statistical models. The new model is based on the statistical derivation of the ray-tracing operation, whose results are a number of paths between the transmitter and receiver, each path comprises a number of rays. The pattern and length of the rays in these paths are related to statistical parameters of the site-specific features of indoor environment, such as the floor plan geometry. A key equation is derived to relate the average path power to the site-specific parameters, which are: 1) mean free distance; 2) transmission coefficient; and 3) reflection coefficient. The equation of the average path power is then used to predict the received power in a typical indoor environment. To evaluate the accuracy of the new model in predicting the received power in a typical indoor environment, a comparison with RT results and with measurement data shows an error bound of less than 5 dB.

Characteristics of radio frequency wave propagation in bounded plasma under the various magnetic field configurations

Detailed characteristics of radio frequency (rf) waves with pulsed modes in the whistler wave range were studied in a cylindrical rf-produced plasma, where the plasma boundary lay in the intermediate regime between infinite whistler wave propagation and bounded geometry helicon wave propagation. Excited magnetic field amplitudes and phases with three components in two-dimensional space were measured for different experimental conditions. Three magnetic field configurations were used and the diameter of the excitation loop antenna was also varied. Numerical calculation by the finite element method, which has been demonstrated to be a powerful means for this analysis, showed good agreement with the observed results, satisfying the dispersion relation and wave structures of helicons in the semisteady state and also satisfying the dispersion of whistlers with a short pulsed mode. The excited waves propagated nearly along the magnetic field lines within a small angle of less than 10°. Furthermore, in the low (high) collisionality regime, domination of standing (propagating) waves was found from the wave analysis.

1.9‐Ghz‐band radio propagation characteristics in an open urban environment and tree loss prediction using a loss layer model

AbstractFor design of optimum microcells on a university campus, it is necessary to determine the propagation characteristics within a propagation environment represented by a relatively large open space scattered with large buildings and many trees. In this paper, for the radiated waves from seven PHS base sites at 1.9 GHz experimentally installed on the campus of Hokkaido University from 1993 to 1994, a median received signal level measurement method is proposed that can be applied in unpaved garden areas (with glass and pebbles) as well as in areas with woods, vegetation, and hilly terrain, and its effectiveness is discussed. Next, for quantitative evaluations of the increase of the propagation loss due to trees in the propagation paths on the campus, a propagation model is proposed that consists of the loss layer model and the geometrical optics two‐ray model. In the loss layer model, the loss due to trees is replaced with a loss per unit length of the propagation path. The estimated median received signal level and the measured value are compared to determine the effectiveness of the model. The increase of the propagation loss on the campus due to trees can be estimated if the loss per unit length of the tree layer by the present loss layer model is chosen to be about 0.1 dB/m for the base site antenna installed on the rooftop of the building and 0.07 to 0.09 dB/m for the antenna installed on the roof of the public phone box. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 84(8): 49–61, 2001