Level Crossing Rate Research Articles

Simulative Investigation of Flat Fading Wireless Channels in terms of First Order and Second Order Statistics

Second order statistics provides an efficient representation of a fading channel and plays a major role in the designing and evaluation of the wireless communication systems. This paper presents a channel model framework for the implementation of important second order statistical parameters, in particular the Level Crossing Rate (LCR) and the Average Fade Duration (AFD). In addition to this, other key first order statistics including Doppler Shift, CDF PDF, BER are also analysed. It also analyses the variations of LCR and AFD in multiple scattering environment .The analysis references to the well known Clarkes Model which has been utilised to plot the variations in key parameters.

Mobile-to-Mobile Channel Measurements at 1.85 GHz in Suburban Environments

This paper presents mobile-to-mobile (M-to-M) channel measurements and models at 1.85 GHz in dense-scattering suburban areas. Three test scenarios were considered for different transmitter (Tx) and receiver (Rx) antenna placements. Scenario 1: inside-vehicle-to-inside-vehicle (IV2IV), where both Tx and Rx antennas were placed inside the test vehicles; Scenario 2: inside-vehicle-to-walk (IV2W), where the Tx antenna was placed inside the vehicle and the Rx antenna was inside the pocket or next to the face of the tester; and Scenario 3: walk-to-walk (W2W), where the Tx and Rx were moving at walking speeds, the Tx antenna was placed on a test cart, and the Rx was inside the pocket or next to the face of the tester. To mimic more typical M-to-M channels in practice, eight sub-scenarios were configured under the availability of the line-of-sight (LoS) between the Tx and Rx. Detailed channel models are proposed for path loss, shadowing, small scale, and multi-scale fading based on the collected measurements. The level crossing rate (LCR) and average fading duration (AFD) are studied from the measurements and compared with the theoretical expressions.

Development of a MATLAB Toolbox for Mobile Radio Channel Simulators

A profound knowledge of mobile radio channels is required for the development, evaluation, and also assessment at practical conditions of present and future mobile radio communication systems. The modelling, analysis, and simulation of mobile radio channels are important key area in current context. In addition to that, knowledge of channel behaviour in mobile radio communication is extensively recommended for the study of transmitter/receiver performances under different propagation scenarios. Our intention in this research work was to develop various kinds of mobile fading channel simulators using MATLAB and embed them into MATLAB software as a toolbox. Implemented channel simulators were combined MATLAB as a toolbox which users can easily select well-known channel models to test and to study the performance of mobile communication systems. It gives better support for the new users to work on the developed channel simulators, run the test procedures as well as parameter computation. The toolbox contains channel simulators for simulating non-stationary land mobile satellite channel, spatial shadowing processes, MIMO channels, multiple uncorrelated Rayleigh fading channels, mobile to mobile channel, frequency hopping channels etc. Set of test procedures were developed such as the autocorrelation function ACF, average duration of fades ADF, the probability density function PDF, and the level-crossing rate LCR etc., in order to test and to confirm the correctness of the implemented channel simulators. Proposed new algorithms to compute the model parameters of the channel simulators were also implemented in the toolbox to enable the parameterization of the channel simulators under specific propagation conditions. Some of the simulation models were implemented based on specification of GSM system by CEPT-COST 207. DOI: http://dx.doi.org/10.4038/jur.v2i1-2.7853 J. Univ. Ruhuna 2014 2:40-45

대전 도심지의 K 대역 위성통신 채널특성 분석

This paper describes the analysis results of channel characteristics in the operating area of satellite OTM (On-The-Move) terminal. The communication channel between the Koreasat-5 and OTM terminal on a test car was measured and recorded in downtown of Daejeon, using the received beacon signal of around 20 GHz. And the measurement data were statistically analyzed and then compared with highway and national road environments. The statistical evaluation of satellite channel was conducted by using probability density function and Markov model and then presented average connection duration(ACD), average fade duration(AFD), and level crossing rate(LCR) of downtown environment.

Propagation Measurements and Analysis for Train Stations of High-Speed Railway at 930 MHz

Train stations are one of the most common structures along a high-speed railway. They can block the line of sight (LOS), generate multiple reflected and scattered waves, and aggravate the fading behavior; however, these effects have been rarely investigated. This paper presents a group of 930-MHz measurements conducted on train stations of high-speed railways in China. The whole process of a train passing stations has been measured with two typical types of stations. The results indicate that, when the station is far from the transmitter (Tx), the semi-closed station (in which the awnings cover both the platforms and the rails) influences the propagation much more seriously than the open station (in which the awnings only cover the platforms supporting a clear free space over the tracks). When the station is near the Tx, the fact of whether the train keeps the LOS and stays inside the station determines the propagation for both types of stations. All the propagation characteristics, including extra propagation loss, shadow fading, small-scale fading, level crossing rate (LCR), average fade duration (AFD), and fading depth (FD), have been measured and computed for the first time. Specific findings of propagation characteristics in the train station scenario are provided. Afterward, by filling the gap of the train station scenario, a table is made to establish the comprehensive understanding of main scenarios in the high-speed railway. Furthermore, comparisons of the propagation characteristics between the train station scenario and ten standard scenarios are made to emphasize the significance of the modeling exclusively for the train station scenario. Finally, rules of the influence of four conditions are quantitatively revealed. The measured results and quantitative analysis are significant for leading the simulation and design of signaling and train control communications systems toward the reality.

Generic stochastic modeling of vehicle-to-vehicle wireless channels

We present a generic statistical characterization of the vehicle-to-vehicle (V–V) wireless channel by adopting a stochastic modeling approach. Our approach is based on the doubly underspread (DU) property of non-wide sense stationary uncorrelated scattering (non-WSSUS) wireless channels, with V–V channels pertaining to this category. DU channels exhibit explicit frequency and time intervals over which they are approximated as WSSUS. We call these intervals restricted time interval (RTI) and restricted bandwidth (RBW), and variations taking place inside them are characterized as small scale variations. Large scale variations take place outside RTI and RBW. In this paper, we focus on small scale variations, thus, our modeling finds its applicability within RTI and RBW. As practical V–V channels exhibit rapid temporal fluctuations due to the inherent mobility of transmitter (Tx), receiver (Rx) and surrounding scatterers (e.g., other vehicles), we analyze the relevant second order statistics characterizing temporal variability, namely, the a) temporal correlation function (CF) (or autocorrelation function (ACF)), b) power spectral density (PSD) (or Doppler spectrum), c) level crossing rate (LCR) and d) average fade duration (AFD). Our analysis considers three-dimensional (3-D) scattering at the Tx and Rx together with random scatterers' mobility. Illustrative examples demonstrate the usefulness and flexibility of our analysis, which is further validated by fitting the theoretical LCR to an empirical, obtained at a US interstate highway. We show that significant Doppler frequencies can arise due to scatterers' mobility exceeding the respective maximum and minimum values when considering only Tx and Rx mobility. Also scatterers' mobility causes more rapid temporal variations when it becomes more intense. The latter is also true when 3-D scattering at the Tx and/or Rx spreads over a greater range of angular sectors and becomes less directional.

A New Analytical Approach to Estimate Fading in Mobile Communication System Design

This paperprovides a novel analytical platform for evaluating theessential second order statistical boundaries for fading in mobile communication for average fade duration (AFD) and levelcrossing rate (LCR) of Rayleigh, Rician and Nakagami fading channels. We derive new expressions for average LCR and AFD. We then model and computationally simulate the proposed method for Rayleigh, Rician and Nakagami channels and separately calculate the LCR and AFD for each channel by this approach. Simulated results obtained for all three channels show that the values of LCR and AFD calculated by using the proposed approach are much closer to actual simulated values than what conventional theoretical formulas deliver.

Statistical Properties Analysis of Relay Channel

The statistical properties of relay channel are quite different from the direct transmission channel for including two phases channel of source to relay and relay to destination. In this paper, we study the relay channel from three viewpoints of probability density function (PDF), level crossing rate (LCR) and Doppler spectrum for Rayleigh, Rice and Nakagami fading models. The closed form expressions are deduced, and simulation evaluation is done to verify the results.

English

Radio-wave propagation through wireless channel is a complicated phenomenon characterized by fading which is the result of multipath propagation. In wireless communication system, random process associated with fading channels can usually characterized by their PDF (Probability Density Function) and CDF (Cumulative Distribution Function). Signal fading can drastically affect the performance of terrestrial communication systems. Several statistical models are available for describing the fading envelope of the received signal in which Rayleigh, Rician and Nakagami are the most frequently applied models. Higher-order statistics such as Level Crossing Rate (LCR) & Average Fade Duration render (AFD) insight into signals which is not always available at lower orders.

Hidden Markov Modeling for Nakagami Fading Channel

In this paper, we proposed a novel hidden Markov model (HMM) to approximate the characteristic of the Nakagami Fading channel. Our study is based on a Hidden Markov Model (HMM). The channel switches between ‘good’ and ‘bad’ channel situation. The transition between the sub-states of the channel is governed by a Markov Chain, which some self-return state is hidden. The performance of the model is studied by simulating probability density functions (PDF), cumulative distribution functions (CDF), level cross rate (LCR) and average fade duration (AFD).

예방진단기술을 이용한 지능형 GIS 감시시스템에 관한 연구

본 논문에서, 가스절연개폐장치(GIS)의 정상상태와 비정상상태에 대해 예방진단기술을 이용하여 자세하게 서술하였다. 이 기술은 지능형 GIS 감시시스템에 의해 저장된 GIS의 데이터의 분석과 진단에 근거한다.<BR> GIS음의 파형은 방전과 자체내의 코로나 방전음에 의해 발생되는 것으로 잡음과 비슷하다. 그러므로, 본 논문에서, GIS음의 정상 상태와 비정상 상태로 분류하는데, 정상과 비정상 상태를 레벨교차율(LCR)과 스펙트로그램 에너지비율로 이용하여 구분하였다.

Finite‐state Markov modelling for wireless cooperative networks

Finite-state Markov chain (FSMC) models can capture the essence of time-varying fading channels and they are important tools for wireless network protocol design and performance study. How to build FSMC models for multi-hop and multi-path wireless systems remains an open issue. In this study, the FSMC models are developed for amplify-and-forward (AF) cooperative systems with selection combining (SC) and maximum ratio combining (MRC) techniques, respectively. First, the second-order statistics, the level-crossing rate and the average fade duration, are derived based on the statistical properties of each individual path, for the AF cooperative systems with SC and MRC, respectively. The results reveal that, in addition to improving the average received signal-to-noise ratio, the diversity combining schemes also improve its second-order statistical properties. Simulation results are given to verify the accuracy of the developed FSMC models. Finally, the models are used to optimise the configuration for scalable video streaming in an AF cooperative network. Experimental results show the feasibility and advantage of applying the proposed FSMC models for assisting protocol design and optimisation in wireless cooperative networks.

이동형 위성단말을 위한 20 GHz 대역 채널 특성 분석

Abstract This paper describes the analysis results of channel characteristics in the operating area of satellite OTM(On-The-Move) terminal. The communication channel between the Koreasat-5 and OTM terminal on a test car is measured and recorded from Daejeon to Daecheon, using the downlink frequency of around 20 GHz. And the measurement data are divided into two classes ; highway environment and national road environment, and then are statistically analyzed. The statistical evaluation of satellite channel is conducted by using probability density function and Markov model and then presents average connection duration(ACD), average fade dura-tion(AFD), and level crossing rate(LCR) of highway environment and national road environment. Finally the statistics data of the two environments are compared with each other.Key words: Satellite Communication Channel, On-The-Move, Average Connection Duration, Average Fade Duration, Level Cross- ing Rate @[#\]D^(Agency for Defense Development)*_`+\Z/ab\#(Department of Electronic Engineering, Chungbuk National University)Manuscript received October 8, 2013 ; Revised November 25, 2013 ; Accepted December 1, 2013. (ID No. 20131008-090)Corresponding Author: Kun-Sup Kwon (e-mail: kevin.kwon@add.re.kr)

Envelope Level Crossing Rate and Average Fade Duration of Nonisotropic Vehicle-to-Vehicle Ricean Fading Channels

This paper proposes a generic geometry-based stochastic model for nonisotropic scattering vehicle-to-vehicle (V2V) Ricean fading channels. With the proposed model, the level crossing rate (LCR) and average fade duration (AFD) are derived. The resultant expressions are sufficiently general and subsume many well-known existing LCRs and AFDs as special cases. The derived LCR and AFD are further investigated in terms of some important parameters, e.g., the shape of the scattering region (two-ring or ellipse), mean angle, angle spread, and directions of movement of the Tx and Rx (same or opposite direction). More importantly, in this paper, the impact of the vehicular traffic density on the LCR and AFD for nonisotropic scattering V2V Ricean fading channels is investigated for the first time. Excellent agreement is observed between the theoretical LCRs/AFDs and corresponding measured data, thus demonstrating the validity and utility of the proposed model.

On the second order statistics for GPS ionospheric scintillation modeling

AbstractEquatorial ionospheric scintillation is a phenomenon that occurs frequently, typically during nighttime, affecting radio signals that propagate through the ionosphere. Depending on the temporal and spatial distribution, ionospheric scintillation can represent a problem in the availability and precision for the Global Navigation Satellite System's users. This work is concerned with the statistical evaluation of the amplitude ionospheric scintillation fading events, namely, level crossing rate (LCR) and average fading duration (AFD). Using α‐μ model, the LCR and AFD are validated against experimental data obtained in São José dos Campos (23.1°S; 45.8°W; dip latitude 17.3°S), Brazil, a station located near the southern crest of the ionospheric equatorial ionization anomaly. The amplitude scintillation data were collected between December 2001 and January 2002, a period of high solar flux conditions. The obtained results with the proposed model fitted quite well with the experimental data and performed better when compared to the widely used Nakagami‐m model. Additionally, this work discusses the estimation of α and μ parameters, and the best fading coefficients found in this analysis are related to scintillation severity. Finally, for theoretical situations in which no set of experimental data are available, this work also presents parameterized equations to describe these fading statistics properly.

An Investigation on Dynamic Human Body Communication Channel Characteristics at 45 MHz in Different Surrounding Environments

This letter investigated characteristics of human body as a communication channel at 45 MHz, in different surrounding environments, taking into account parameter changes arising from body activities. A large amount of measurement data has been collected in five real environments for random body motions: in a conference hall, laboratory, grove, playground, and an anechoic chamber. The received power for nine human body communication (HBC) channels was acquired, with more than 2 700 000 data snapshots in total. Environmentally independent analysis of the mean and standard deviations of the received power was performed. The results of applying the Nakagami function were satisfying for the conference hall; the results of applying Lognormal function showed that it was a suitable model for the rest of the investigated environments. Lognormal and Weibull functions served well for level crossing rate (LCR) and average fade duration (AFD) in all environments. In our research, we observed lower values of LCR and AFD in HBC, compared to their usual values for ISM-band communication.

Second order statistics of SC receiver over k-μ multipath fading channel

In this paper wireless communication system with dual branch selection combining (SC) diversity receiver operating over k-? multipath fading environment is considered. Closed form expressions for average level crossing rate of SC receiver output signal envelope and average fade duration of proposed system are evaluated. Numerical results are presented graphically to show the influence of Rican factor k and fading severity ? on average level crossing rate and average fade duration.

Performance Analysis of Selecting Maximal Ratio Combining Hybrid Diversity System over Ricean Fading Channels

In this paper an approach to the performance analysis of hybrid MRCS (Selection Maximal Ratio Combining) diversity system operating over Ricean fading channels is presented. Hybrid MRCS combining method has a simple implementation, where maximal-ratio combined signals are chosen on a selection combining basis. Closed form expressions are provided for standard first and second order statistical measures for the signal at the output of the combiner, i.e. PDF (probability density function), CDF (cumulative distribution function), LCR (level crossing rate). Capitalizing on them standard performance measures like ABEP (Average Bit Error Probability) over some modulation techniques and AFD (Average Fade Duration) are efficiently evaluated and discussed in the function of various system parameters.

Estimation of level-crossing rate of signals reflected by ocean surface based on rough surface scattering theory

A method is proposed for theoretical estimation of the level-crossing rate of the underwater acoustic communication signals that are reflected from the ocean surface. The variation in the reflection coefficient of the moving ocean surface causes the intensities of the received signals to fluctuate. In this work, the reflection coefficient is obtained by modeling the time-varying characteristics of the ocean surface based on rough surface scattering theory. The surface of the ocean is modeled by Gaussian processes that are characterized by ocean spectra such as the Pierson-Moskowitz and Durden-Vesecky spectra. Furthermore, Gaussian random functions with a particular correlation time are incorporated to model the surface that continuously varies over time. Then the standard Periodogram analysis is applied to estimate the autocorrelation function. Finally, the level-crossing rate is calculated with the negative curvature of the autocorrelation function. For verification, comparison of the simulated results with the measured data is provided.

On the Connection between Gaussian Q-Functions and a Class of Hypergeometric Functions: Application to LCR of Lognormal Processes

In this letter, we derive a closed-form expression for the two-dimensional joint Gaussian Q-function in terms of a class of hypergeometric functions. Particularly, we show that the 2-D Gaussian Q-function can be expressed in terms of the bivariate confluent hypergeometric function Φ1, which is well studied in classical books of integrals, special functions and Laplace transforms. As a direct application, we derive a new closed-form expression for the level crossing rate (LCR) and the average fade duration (AFD) of sampled lognormal processes with arbitrary correlation profile.