Macrocell electric field strength prediction model based upon artificial neural networks

A new macrocell prediction model for mobile radio environment is presented. The use of feedforward artificial neural networks makes it possible to overcome some important disadvantages of previous prediction models, including both deterministic and statistical types. Our sample implementation is based upon extensive electric field strength measurements (in the 900-MHz frequency band) that were carried out in the city of Belgrade using six different test transmitter locations. Comparison between the data obtained by the proposed electric field strength prediction model and independent measurement sets show that the proposed model is sufficiently accurate for use in planning mobile radio systems.     

A comparison of prediction methods for 800 MHz mobile radio propagation

The design and installation of a mobile radio system involves the evaluation or prediction of the propagation characteristics associated with the geographical area of interest. A wide variety of prediction techniques has been developed for different mobile environments, so that the task of selecting an appropriate propagation prediction method can be difficult and complex. This is especially true for systems operating in the upper-UHF band of 800-950 MHz, where mobile radio services are rapidly growing. A practical comparison is given of current prediction techniques available in the literature (for slow lognormal fading rather than multipath Rayleigh fading), with an emphasis on three essential criteria to consider in the selection process: the type of terrain or geography covered by each method, the form of prediction provided (e.g., transmission loss estimates, field strength contour maps, etc.), and the implementation difficulty and degree of sophistication.     

Choice of a suitable method for the prediction of the field strength in planning land mobile radio systems

Aiming at the choice of a method for the field strength prediction over irregular terrain in land mobile radio service which could be adopted as the most suitable for engineering purposes, six out of the known methods have been analyzed. To verify their prediction accuracy, complex field tests have been carried out. With the moving vehicle, the field strength has been measured along well defined path profiles. Statistical processing of the recorded data has yielded the median field strength levels in a number of points of the path serving as reference for the accuracy assessment. Other features of the compared methods, such as their operativeness, complexity, suitability for the computer application, influence of subjective factors, and tolerances in determining the initial data, have been discussed. The "clearance angle" method, recently proposed and experimentally verified in detail during the field test described in this paper, has been chosen, after an argued analysis, as the most suitable field strength prediction method for engineering purposes.     

Feasibility of neural networks in modelling radio propagation for field strength prediction

A typical back-propagation neural network (BPN) model is developed for modelling radio propagation for field strength prediction based on data measurements of propagation loss (in decibels) with terrain information taken in an urban area (Athens region) in the 900 MHz band. The feasibility of the BPN model is checked against the performance of a conventional semiempirical reference model. The performance of both models is quantified by statistical methods. The evaluation is done by comparing their prediction error statistics of average absolute, standard deviation and root mean square and by comparing their percentage accuracy and correlation of predicted values relative to true data measurements. © 1998 John Wiley & Sons, Ltd.     

Comparisons of a computer-based propagation prediction tool withexperimental data collected in urban microcellular environments

Engineers designing and installing outdoor and indoor wireless communications systems need effective and practical tools to help them determine base station antenna locations for adequate signal coverage. Computer-based radio propagation prediction tools are now often used in designing these systems. We assess the performance of such a propagation tool based on ray-tracing and advanced computational methods. We have compared its predictions with outdoor experimental data collected in Manhattan and Boston (at 900 MHz and 2 GHz). The comparisons show that the computer-based propagation tool can predict signal strengths in these environments with very good accuracy. The prediction errors are within 6 dB in both mean and standard deviation. This shows that simulations, rather than costly field measurements, can lead to accurate determination of the coverage area for a given system design     

Comparison of different methods for the prediction of the field strength in the VHF range

A number of prediction methods have been proposed in the literature in recent years. By using topographical data from a terrain data bank, these methods should lead to a more accurate prediction of the field strength in irregular terrain. The prediction accuracy of these methods has been examined by comparing the field strengths they yield to those experimentally determined at VHF in the coverage area of the transmitter Feldberg/Schwarzwald. Also, the prediction according to CCIR Rec. 370-4, [1], which takes topography into account only by statistical parameters, was included in the comparison. The substantial elements of the methods will be summarized and the results of the comparison will be discussed.     

Cell radius inaccuracy: a new measure of coverage reliability

A robust method for determining the boundaries of cells and the associated reliability of the radio frequency (RF) coverage within these boundaries is presented. The procedure accurately determines the effective cell radius using a linear regression of the RF signal strength samples. The accuracy of this estimate is quantified both as a radius uncertainty (e.g., ±100 m) and as a coverage (i.e., area/edge) reliability error through: (1) simulation; (2) analysis of real data; and (3) theoretical analysis. It is shown that if the estimate of the cell radius meets the desired accuracy, then the corresponding estimates of coverage reliability (both area and edge) are more than sufficiently accurate. Through a sensitivity analysis, it is discovered that estimating the cell radius is a much more critical step in determining the quality of RF coverage than the more common practice of simply estimating the area reliability. In addition, a formula for estimating area reliability is given and shown to be more accurate than can be obtained by current approaches. The verification method presented is particularly useful in wireless planning since it effectively determines the geographic extent of reliable RF coverage. It is recommended that radio survey analyses select cell radius estimation as the preferred method of coverage verification     

Neural network-based path loss model for cellular mobile networks at 800 and 1800 MHz bands

Cellular radio communication systems have become essential for data/voice/video/multimedia applications. The performance of cellular communication radio systems is assessed by considering the design specifications of frequency planning, channel assignment and interference mitigation strategies among others. Frequency planning is the most important component to improve capacity or quality of cellular radio systems. Large-scale path loss values between the base station and mobile stations are the key regulating factors that limit the performance of cellular systems, especially in urban/vegetation region. There is a necessity to develop a suitable path loss prediction model for predicting path loss values based on received signal strength measurements. In this paper, an ANN-based path loss model was used for macro cell measurement data obtained in the Vijayawada urban region, India. The Multi-Layer Perceptron (MLP) neural network model was considered. The prediction results indicate that the ANN model outperformed the Auto Regressive Moving Average (ARMA) and COST-231-WImodels. The outcome of this research work will be immensely useful for improving coverage and ensuring better frequency planning of cellular radio systems.     

Fading Channel Prediction for Mobile Radio Adaptive Transmission Systems

Adaptive transmission methods can potentially aid the achievement of high data rates required for mobile radio multimedia services. To realize this potential, the transmitter needs accurate channel state information (CSI) for the upcoming transmission frame. In most mobile radio systems, the CSI is estimated at the receiver and fed back to the transmitter. However, unless the mobile speed is very low, the estimated CSI cannot be used directly to select the parameters of adaptive transmission systems, since it quickly becomes outdated due to the rapid channel variation caused by multipath fading. To enable adaptive transmission for mobile radio systems, prediction of future fading channel samples is required. Several fundamental issues arise in the design and testing of fading prediction algorithms for adaptive transmission systems. These include complexity, robustness, choice of an appropriate channel model for algorithm validation, channel estimation and noise reduction required for reliable prediction, and design and analysis of adaptive transmission methods aided by fading prediction algorithms. We use these criteria in the review of recent advances in the area of fading channel prediction. We also demonstrate that reliable fading prediction makes adaptive transmission feasible in diverse wireless communication systems.     

Doppler-rate estimation for burst digital transmission

We propose a new algorithm for Doppler rate estimation in burst-mode phase shift keying (PSK) transmissions. This issue may arise in mobile radio links when the received signal experiences significant time-varying Doppler distortion, as in low-earth-orbit satellite systems. The algorithm is based on the transmission of a training sequence and has a feedforward structure that is easy to implement in digital form. Its estimation accuracy is close to the Cramer-Rao bound even at SNR values as low as 0 dB. Comparisons with earlier methods are discussed     

A channel model for multipath interference on terrestrialline-of-sight digital radio

A comprehensive system model for characterizing the effects of multipath propagation on digital radio systems in the 4-6-GHz band is shown in this paper. The effects of terrain-induced multipath propagation in the presence of atmospheric anomalies are studied using data from experimental microwave links in the field and in the laboratory. This technique, which treats multipath propagation as digital signal distortions caused by interference from ground reflections, has not been shown previously. A forward multipath propagation model is used to identify the critical propagation parameters for a quadrature amplitude modulated (QAM) signal. A normalized two-ray channel model is developed to approximate the frequency response produced by interference from a ground reflection in a narrow band. The effectiveness of this channel model is evaluated using measured data from the test radio link in the laboratory and in the field     

基于GIS的青海广电资源管理系统的设计及优化

目前青海的广电资源管理系统存在多系统并存,数据、接口不统一等问题,系统中的信号覆盖监测模块还是基于传统的场强模型实现的,不能反映广播电视信号的真实地理分布。针对上述问题,提出了利用GIS管理广播电视资源的完整解决方案,并利用DEM和实测信号获取覆盖区域的改正参数曲面,对传统基于GIS方案的信号覆盖模型进行改进,结果表明新模型的监测精度提高了12%。该研究将为青海省广播电视资源的高效管理和规划提供重要的技术支持。     

全极化昆虫雷达生物参数反演方法与外场定量试验验证

全极化雷达是新一代昆虫雷达的发展方向.本文介绍了全极化雷达的昆虫体轴朝向、 体重和体长等生物参数反演方法.相对传统方法,这些方法精度更高,然而,这些方法仅经过微波暗室测量昆虫数据验证了可行性,还未经过实际全极化雷达外场测量验证.本文利用Ku波段全极化昆虫雷达,设计并开展了基于双无人机协同飞行悬吊昆虫的外场定量试验,测量...     

Adaptive Multiplication-Free Transversal Equalizers with Application to Digital Radio Systems

Recently, multiplication-free digital filters have been proposed for different applications to digital radio systems and signal processing. The absence of multiplication is obtained by constraining each coefficient to be sum of powers of two. In this way, multipliers are substituted by shift registers and, if appropriate, some adders. The optimal power-of-two coefficients must be computed through a nonlinear optimization procedure. Until now the problem of adapting the power-of-two coefficients of base band transversal equalizers in the case of time-varying channels had not been considered. In this paper two algorithms are proposed to cope with this problem and are compared from the viewpoint of complexity, accuracy, and convergence speed. As an application example, transmission of a biphase PSK digital radio system over a multipath fading channel is considered.     

Observations and Conclusions from a Three Year Digital Radio Field Experiment in Australia

For the purpose of investigating the performance of digital radio systems, Telecom Australia established and conducted over a three year period (1982-1984), a 140 Mbit/s 16 QAM digital radio field experiment. In parallel with this experiment, analytical work was undertaken to develop an "outage prediction method" to assist with route design. This paper presents the observations and conclusions drawn from this work. Emphasis is placed on the aspects which relate to system design. We show that for digital radio outage prediction, a radio path can be characterized for multipath fading by the probability of occurrence of multipath fading and the mean echo delay, while the radio equipment can be characterized by a set of normalized parameters. The performance improvements achieved through the use of adaptive equalization and space-diversity are highlighted. Finally, we present a methodology for considering the performance of digital radio systems in the presence of interference and thermal noise, and present results for system performance with adjacent channel interference.     

室内场强预测理论研究及工程应用

在数字移动通信网络工程建设中,希望对网络覆盖区域的接收信号场强进行预测,尽可能减少大量的实测工作。首先介绍场强预测理论,然后根据工程实际应用,介绍了目前常用的几种室内传播模型;最后在实际环境下,利用TEMS模拟测试对Chan传播模型和衰减因子传播模型进行比较,提出了较为实用的衰减因子模型,以利于工程实践中对室内场强传播的预测。     

Performance Analysis of UWB Channels for Wireless Personal Area Networks

Ultra-wide band (UWB) communication is one of the most promising technology for high data rate networks over short-range communication. The ultra-wide bandwidth offers pulses with very short duration that provides frequency diversity and multipath resolution. Ultra-wide band (UWB) channels raise new effects in the receiver, the amplitude fading statistics being different compared to the conventional narrow band wireless channels. This review paper focuses on modeling of ultra-wide band channels, especially for simulation of personal area networks and also discusses the benefits, application potential and technical challenges in wideband communication. The concept of Orthogonal Frequency Division Multiplexing (OFDM) has recently been applied in wireless communication systems due to its high data rate transmission capability with high bandwidth efficiency and its robustness to multi-path delay. UWB OFDM communication was proposed for physical layer in the IEEE 802.15.3a standard which covers wideband communication in wireless personal area networks. Since the channel model for multicarrier UWB communication is different from that of plain ultra-wide band channel, a novel modification method in UWB channel model is proposed with specific center frequency and multipath resolution. Moreover, dynamic channel estimation is necessary before demodulation of UWB OFDM signals since the radio channel is time varying and frequency selective for wideband systems. The performance of the proposed method is statistically analyzed using LS and MMSE based channel estimation methods.     

A versatile wave propagation model for the VHF/UHF rangeconsidering three-dimensional terrain

A polarimetric wave propagation model for field strength forecasting and coverage prediction in the VHF/UHF frequency range is presented. The model uses a digital terrain data bank and considers multipath propagation. Based on the uniform geometrical theory of diffraction (UTD) and physical optics an approach is described for calculating the propagation effects in natural 3-D terrain, given by topological and morphographical data. The method for field strength forecasting is described and methods for the analysis of the predicted multipath signal are discussed. It is shown how the complex probability density function (PDF) for the receiver field strength and the field strength delay spectrum can be derived. Methods for further evaluation of the transmitting channel characteristics are discussed     

Mobile anchor-assisted localization over android

While localization is essential to many applications, there are quantities of wireless nodes whose accurate locations remain unknown or hard to tell. As a remedy, this paper is leveraging a GPS-capable Android handset that features portability and sufficient computing capability to collect data and display localization results thereof. Our objective is to locate the unknown nodes under irregular radio coverage. To this end, we first devise a range-free approach that computes the most likely circumcenter from a convex polygon representative of radio coverage. Preliminary simulations corroborate the effectiveness of our development. Then the first approach is simplified by allowing for received signal strengths with the notion of estimative regions, namely rectangular areas enclosing an unknown node, to refine the area of interest for localization. Free from involved computations, our treatment mitigates the errors of estimation resulting from different radio signal propagation scenarios, by taking an additional parameter for ameliorating localization accuracy. Field experiments were conducted to demonstrate performance results overlying Google Maps on the handset and through quantitative comparisons in different settings. Performance results show that our development can get fielded in practice.     

Method for Enhancing the Accuracy of Frequency Offset Estimation in OFDM Modulation Based Communication Systems

The paper proposes a method for enhancing the accuracy of estimation of frequency offset for OFDM modulation based communication systems. An increase accuracy of the proposed method is achieved at the expense of combined use of pilot and information symbols of OFDM signal. The main factors determining the accuracy of proposed method were identified. Mathematical simulation of the proposed method was performed for a multipath radio wave propagation channel. The proposed method efficiency was shown in comparison with existing methods for the estimation of frequency offset. Advantages and disadvantages of existing and proposed methods were described. The relationships of the root-mean-square error of frequency offset estimation as a function of the signal-to-noise ratio were built for the proposed and existing methods. The attainable high accuracy of frequency offset estimation by employing the proposed method makes its use expedient in control and measuring equipment. Conclusions have been made regarding the simulation results obtained and the expediency of proposed method applications.