Showing papers by "Geoffrey G. Messier published in 2014"

Joint Fading and Shadowing Model for Large Office Indoor WLAN Environments

Abstract: This paper presents measurements and a propagation model for an indoor wireless LAN (WLAN) scenario that represents an open concept office or laboratory layout with few large obstacles to reflect and refract the transmitted signal. Most mobile WLAN users generally restrict their movements to a small area due to the inability of most WLANs to accommodate hand-offs. As a result, users travel through at most one or two scattering clusters and experience only one or two discrete shadowing values. Hence, this paper will use propagation measurements collected over bandwidths of 10 MHz, to develop a statistical model for shadowing suitable for such an indoor WLAN scenario. Moreover, in indoor environments shadowing varies quickly enough to require some channel estimation algorithms to account for both small scale and large scale statistics. Therefore, this paper will present a distribution that jointly models variations due to both Rician fading and the new shadowing model. An analytical expression for the probability density function (PDF) of the joint distribution will be derived and fit to the experimental propagation data.

DSL and PLC Co-Existence: An Interference Cancellation Approach

Abstract: It is often advocated that a solution to the problem of interference to digital subscriber line networks (DSL) from a power line communications (PLC) network is to prevent the PLC networks from utilizing the DSL spectrum. However, this solution will render PLC networks inoperable with the introduction of wide-band DSL technology like G.Fast. We propose utilizing an interference cancelling scheme to ensure the co-existence of DSL and PLC networks within the home environment. A measurement campaign is conducted where a set of 480 measurements are collected within a residential house to characterize the PLC-to-DSL interference environment for two DSL modem installation scenarios. The interference cancelling scheme is based on an adaptive frequency domain interference canceller (FDIC) that utilizes the common mode (CM) PLC interference to estimate the differential mode (DM) PLC interference. The effectiveness of the FDIC, which is insensitive to the non-stationarity of the PLC channel, is demonstrated using analysis that incorporates the measured PLC-to-DSL coupling channels.

Performance of wireless/power line media diversity in the office environment

Abstract: The simultaneous use of wireless and power line communications (PLC) channels provides a convenient method for increasing the coverage and throughput of indoor networks. In this paper, we compare coding diversity and modulation diversity schemes that both utilize parallel wireless and PLC links. The signal to noise ratio (SNR) values used in this analysis are determined by conducting a series of average link gain measurements in an office environment. Measurement results show that both wireless and PLC SNRs have a wide range, but neither type of media is guaranteed to dominate performance for a given link. The empirical SNR values are used in a Monte Carlo simulation to evaluate the possible throughput advantages of coding and modulation wireless-PLC media diversity.

Fading Statistics for the Joint Fading and Two Path Shadowing Channel

Abstract: New expressions for the joint moments, mean, variance and amount of fading (AF) of the Joint Fading and Two-path Shadowing (JFTS) distribution are derived in this letter. The derived expressions for theoretical mean and variance are shown to agree with the experimental results. The AF expression is used for comparing the severity of fading imparted by the JFTS distribution to the fading severity of other common small scale fading and composite fading / shadowing distributions.

Performance Analysis of BPSK over Joint Fading and Two-Path Shadowing Channels

Abstract: The performance of Binary Phase Shift Keying (BPSK) in a Joint fading and Two-path Shadowing (JFTS)environment is analyzed. Closed form expression for the exact Average Bit Error Rate (ABER) of coherent BPSK scheme is presented using the Moment Generating Function (MGF) of the JFTS distribution. Finally the coherent BPSK ABER of a wireless communication system is simulated over JFTS fading / shadowing channels with and without non- iterative Forward Error Correction (FEC) coding and compared with the analytical ABER expression.

The Cumulative Distribution Function for the Joint Fading and Two Path Shadowing Channel: Expression and Application

Abstract: —A new expression for the Cumulative DistributionFunction (CDF) of the Joint Fading and Two-path Shadowing(JFTS) distribution is derived in this paper. The derived theo-retical CDF expression is shown to agree with the experimentalresults. The CDF expression is used to derive an outage expres-sion for non-diversity transmission which is then used to illustratethe performance of adaptive transmission over the JFTS link. I. I NTRODUCTION Attempts to model the combined effect of small scale fadingand shadowing have long been introduced in the literature [1]–[7] in order to characterize land mobile satellite (LMS) andmacro-cellular channels. In an outdoor environment, macro-cellular and LMS communication users are highly mobile andcover considerable distances which allows them to visit severalscattering clusters. As a result, a range of main waves arriveat the mobile resulting from these clusters, where the strengthof each can be drawn from the log-normal distribution.In an indoor wireless environment like an open office orlaboratory, there are not enough large obstacles to reflect orrefract the main waves contributed by the scattering clusters.Moreover, due to the inability of most WLAN standards inhandling hand-offs, mobile WLAN users have to limit theirmovements within a small area traveling at most between oneor two scattering clusters. An appropriate composite fading /shadowing channel model that characterizes the transition fromlocal small scale fading to global shadowing statistics in a largeoffice indoor wireless environment is proposed in [8] based onan indoor measurement campaign. A joint distribution calledthe Joint Fading and Two-path Shadowing (JFTS) distributioncombining Rician fading and the two wave with diffuse power(TWDP) shadowing models is shown to fit the measurementdata. However, the work in [8] is limited to the derivation ofthe expression for the probability density function (PDF) ofthe JFTS distribution.Statistical characterization of the received signal envelopein terms of its moments and cumulative distribution function(CDF) in faded and shadowed indoor wireless environments, isuseful in the design of a mobile radio communication systemand the analysis of its performance. The CDF expression isof particular interest, as it can be directly applied to analyzethe outage probability performance of communication systems.Outage probability is an appropriate performance indicator foradaptive modulation techniques, as these techniques attemptto maximize the average data rate under a bit error rate(BER) constraint or minimize outage probability under a delayconstraint. Hence, the expression for CDF can be used toanalyze the outage probability of optimal adaptive modulationtechniques like optimal rate adaptation with constant transmitpower (ORA), optimal simultaneous power and rate adaptation(OPRA), and sub-optimal policies like total channel inversionwith fixed rate (CIFR) and truncated channel inversion withfixed rate (TIFR) [9]. CDF expressions can also be usedto calculate higher order statistics like Level Crossing Rate(LCR) or Amount of Fading (AF), as is done in [10].The primary contribution of this paper is two-fold. Firstly, anew closed-form expression for the CDF of signal envelope atthe output of a JFTS channel is derived. Secondly, the derivedexpression for CDF is used to develop a new expressionfor outage probability. Finally, the analytical expressions forCDF and outage probability are used as a basis for numericalanalysis of few adaptive modulation techniques, like OPRAand TIFR. The outage probability performances are plottedas functions of the parameters of the communication channelmodel. The analytical results for both CDF and outage prob-ability are compared with the simulation results in order toverify the validity of the derived expressions.The rest of the paper is organized as below. Section IIpresents the PDF of the JFTS faded received signal envelope.The analytical derivation of the CDF of the JFTS fadedreceived signal envelope is presented in Section III. Section IVderives the expression for outage probability. Numerical resultsfor the CDF of the JFTS distribution and simulation results forthe outage probability performance of two different adaptivetransmission policies, OPRA and TIFR, are presented inSection V. Concluding remarks are provided in Section VI.