ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / RF Communication (COMMS) systems where receivers and transmitters are in motion must be proven rigorously over an array of natural RF link perturbations such as Carrier Doppler shift, Signal Doppler shift, delay, path loss and noise. These perturbations play significant roles in COMMS systems involving satellites, aircraft, UAVs, missiles, targets and ground stations. In these applications, COMMS system devices must also be tested against increasingly sophisticated intentional and unintentional interference, which must result in negligible impact on quality of service. Field testing and use of traditional test and measurement equipment will need to be substantially augmented with physics-compliant channel emulation equipment that broadens the scope, depth and coverage of such tests, while decreasing R&D and test costs and driving in quality. This paper describes dynamic link emulation driven by advanced antenna and motion modeling, detailed propagation models and link budget methods for realistic, nominal and worst-case hardware-in-the-loop test and verification.

"Real-time performance evaluation of wireless local area networks (WLANs) is an extremely challenging topic. The major drawback of real-time performance analysis in actual network installations is a lack of repeatability due to uncontrollable interference and propagation complexities. These are caused by unpredictable variations in the interference scenarios and statistical behavior of the wireless propagation channel. This underscores the need for a Radio Frequency (RF) test platform that provides isolation from interfering sources while simulating a real-time wireless channel, thereby creating a realistic and controllable radio propagation test environment. Such an RF-isolated testbed is necessary to enable an empirical yet repeatable evaluation of the effects of the wireless channel on WLAN performance. In this thesis, a testbed is developed that enables real-time laboratory performance evaluation of WLANs. This testbed utilizes an RF-isolated test system, Azimuthâ„¢ Systems 801W, for isolation from external interfering sources such as cordless phones and microwave ovens and a real-time multipath channel simulator, Elektrobit PROPSimâ„¢ C8, for wireless channel emulation. A software protocol analyzer, WildPackets Airopeek NX, is used to capture data packets in the testbed from which statistical data characterizing performance such as data rate and Received Signal Strength (RSS) are collected. The relationship between the wireless channel and WLAN performance, under controlled propagation and interference conditions, is analyzed using this RF-isolated multipath testbed. Average throughput and instantaneous throughput variation of IEEE 802.11b and 802.11g WLANs operating in four different channels - a constant channel and IEEE 802.11 Task Group n (TGn) Channel Models A, B, and C - are examined. Practical models describing the average throughput as a function of the average received power and throughput variation as a function of the average throughput under different propagation conditions are presented. Comprehensive throughput models that incorporate throughput variation are proposed for the four channels using Weibull and Gaussian probability distributions. These models provide a means for realistic simulation of throughput for a specific channel at an average received power. Also proposed is a metric to describe the normalized throughput capacity of WLANs for comparative performance evaluation."

Cette thèse s’inscrit dans le domaine de la caractérisation des systèmes de communication sans fil utilisant la diversité des antennes. En effet, ces systèmes permettent de lutter contre les évanouissements des signaux, lorsque le terminal est placé dans un environnement riche en multi-trajets. L’objectif d'une telle recherche est : d’étudier l'association de plusieurs antennes à l'émission et / ou la réception pour améliorer le bilan de liaison, et la capacité des systèmes sans fil, (diminution de BER (Bit Error Rate), augmentation de débit ...). Cette thèse s’intéresse à l'aspect électromagnétique et traitement du signal. Afin de comprendre les phénomènes mis en jeu, et de caractériser les performances du terminal, il doit être placé dans un environnement de propagation multi-trajets contrôlable dans le temps et dans l'espace.Cela nous amène à trouver des méthodes de mesures capables de reproduire des modèles de canaux de propagation réalistes. Dans le cadre de cette thèse la méthode utilisée est la chambre réverbérante. Dans cette thèse, nous nous intéressons à l'aspect temporel. La chambre réverbérante (RC) est considérée comme un outil utile pour émuler des environnements riches en multi-trajets. Dans cette contribution, ce dispositif est utilisé pour émuler des modèles canaux multi-trajets, et évaluer la performance des systèmes de communication sans fil. Cette évaluation est effectuée avec des mesures en temps réel et non temps réel. Parmi les objectifs de cette thèse est d'obtenir un modèle de simulation électromagnétique de la chambre réverbérante basé sur une approche circuit, afin de déterminer la fonction de transfert de canal en fonction des pertes. / This thesis is part of the field of the characterization of wireless communication systems using antennas diversity. Indeed, such systems allow fighting against the signals fading, when the terminal is inside a strong multipath environment. The issue of such research is: to study the association of multiple antennas at transmitting and/or receiving sides to improve the link budget, and the capacity of wireless systems, (decrease of BER (Bit Error Rate), increase of throughput …). This thesis takes an interest to the electromagnetic aspect, and signal processing. In order to understand the involved phenomena, and to characterize the terminal performance, it should be placed in a controlled multipath propagation environment in time, and in space. This brings us to find measurement methodologies able to reproduce models of realistic propagation channels. As part of this thesis the method used is the reverberation chamber. In this thesis we are interested in the time aspect. Reverberation chamber (RC) is considered as a useful tool to emulate rich multipath environments. In this contribution, this device is employed to emulate multi clusters channel models (cluster is defined as a group of multipath), and evaluate performance of wireless communication systems. This evaluation is performed with real time and not-real time measurements. It remains to note that among the objectives set out in this PhD thesis is to obtain electromagnetic simulation model of the reverberation chamber based on circuit approach, in order to determine the channel transfer function versus losses quantities.