Statistical analysis of multipath clustering in an indoor office environment

A parametric directional-based MIMO channel model is presented which takes multipath clustering into account. The directional propagation path parameters include azimuth of arrival (AoA), azimuth of departure (AoD), delay, and power. MIMO measurements are carried out in an indoor office environment using the virtual antenna array method with a vector network analyzer. Propagation paths are extracted using a joint 5D ESPRIT algorithm and are automatically clustered with the K-power-means algorithm. This work focuses on the statistical treatment of the propagation parameters within individual clusters (intracluster statistics) and the change in these parameters from one cluster to another (intercluster statistics). Motivated choices for the statistical distributions of the intracluster and intercluster parameters are made. To validate these choices, the parameters' goodness of fit to the proposed distributions is verified using a number of powerful statistical hypothesis tests. Additionally, parameter correlations are calculated and tested for their significance. Building on the concept of multipath clusters, this paper also provides a new notation of the MIMO channel matrix (named FActorization into a BLock-diagonal Expression or FABLE) which more visibly shows the clustered nature of propagation paths

Evaluation of the Military Utility of Employing an Angle of Arrival Payload Hosted on a CubeSat as an Augmentation to Existing Geolocation Systems

This research models the performance of the proposed augmentation system as well as three and four-ball TDOA satellite systems and AOA and three-ball TDOA airborne systems individually, and performs geolocation estimate fusion via a variety of techniques to determine the increase in performance due to geolocation estimate fusion in operationally representative scenarios. It also introduces a high fidelity surface of the earth constraint based upon a digital elevation model across all geolocation algorithms. The results from this research show that the proposed augmentation system does have military utility when combined with other geolocation systems of similar or worse individual performance. Additionally, it demonstrates the performance improvement due to correct application of a surface of the earth constraint, and the most appropriate estimate fusion technique

Experimental statistical channel modelling for advanced wireless communication systems in indoor environments

Draadloze communicatiesystemen voor mobiele telefonie en draadloos internet zijn onmisbaar geworden in het dagelijkse leven. De grootste troef van draadloze communicatie over bedrade communicatie is de toegenomen mobiliteit. Draadloze communicatie heeft evenwel ook één groot nadeel, namelijk de onzekerheid over de kwaliteit van de link tussen zender en ontvanger. Waar bedrade communicatie een doorgedreven ontwerp van het kanaal tussen zender en ontvanger (d.i. de kabel) toelaat, is het ontwerp van het draadloze kanaal (d.i. de omgeving) bijna onmogelijk. Desondanks kunnen wel modellen van de propagatie van draadloze signalen opgesteld worden voor verschillende types omgevingen. Deze modellen laten toe om de betrouwbaarheid en de performantie van een draadloze link in te schatten. Modellering van draadloze propagatie voor indooromgevingen is het algemeen onderwerp van dit proefschrift. De propagatiemodellering in dit proefschrift betreft drie types indooromgevingen, nl. industriële en kantooromgevingen, en de omgeving binnen in een voertuig. De modellering bestaat uit statistische modellen gebaseerd op veldmetingen in deze omgevingen. Verschillende parameters van draadloze signalen worden onderzocht, zoals de variabiliteit van het signaalvermogen met de afstand en in de tijd, het signaalbereik, de dispersie in het tijdsdomein, de dispersie in het spatiaal domein en het vermogensverlies bij propagatie van buiten naar binnen een voertuig

Broadband wireless communication systems: Channel modeling and system performance analysis

Wideband channel modeling, which can accurately describe the most important characteristics of wideband mobile fading channels, is essential for the design, evaluation, and optimization of broadband wireless communication systems. In the field of wideband channel modeling, the tradeoff between the prediction accuracy and simulation efficiency has to be taken into account. On one hand, channel models should be as accurate as possible. On the other hand, channel models are supposed to be simple and easy to put into use. There are several commonly used approaches to channel modeling, e.g., measurement-based channel modeling and deterministic channel modeling. Both methods are efficient in capturing the fading behavior of real-world wireless channels. However, the resulting channel models are only valid for the specific environments as those where the measurements were carried out or the ray-tracing scenario was considered. Moreover, these methods are quite time consuming with high computational cost. Alternatively, the geometry-based stochastic channel modeling approach can be employed to model wideband mobile fading channels. The most attractive feature of this method is that the derived channel models are able to predict fading behavior for various propagation environments, and meanwhile they can be easily implemented. Thus, the dissertation will complete the wideband channel modeling task by adopt the geometry-based stochastic approach. In the dissertation, several geometry-based channel models are proposed for both outdoor and indoor propagation scenarios. The significance of the work lies in the fact that it develops channel models under more realistic propagation conditions which have seldom been considered, such as for non-isotropic scattering environxi ments and mobile-to-mobile (M2M) fading channels. In addition, the proposed channel models remove the scarcity that proper geometry-based channel models are missing for indoor environments. The most important statistical properties of the developed channel models including their temporal autocorrelation function (ACF), the two-dimensional (2D) space cross-correlation function (CCF), and the frequency correlation function (FCF) are analyzed. Furthermore, efficient channel simulators with low realization expenditure are obtained. Finally, the validity of the proposed channel models is demonstrated by comparing their analytical channel statistics with the empirical ones measured from real world channels. Besides the work in the field of wideband channel modeling, another part of the dissertation is dedicated to investigate the performance of SISO1 orthogonal frequency division multiplexing (OFDM) broadband communication systems and space-time (ST) coded MIMO2 OFDM broadband communication systems. This work provides a deep insight into the performance of a broadband mobile radio communication system over realistic wideband fading channels. Analytical expressions are derived for bit error probability (BEP) or symbol error rate (SER) of systems. In order to confirm the correctness of the theoretical results as well as to show the usefulness of the wideband channel models in the testing and analysis of a broadband communication system, SISO OFDM systems and space-time coded MIMO OFDM systems are simulated in the dissertation. In order to improve the reliability of digital transmission over broadband wireless radio channels, a differential super-orthogonal space-time trellis code (SOSTTC) is designed for noncoherent communications, where neither the transmitter nor the receiver needs the channel state information (CSI) for decoding. In addition, a new decoding algorithm is proposed. The new algorithm has exactly the same decoding performance as the traditional one. However, it is superior from the standpoint of overall computing complexity

Real-time localization using received signal strength

Locating and tracking assets in an indoor environment is a fundamental requirement for several applications which include for instance network enabled manufacturing. However, translating time of flight-based GPS technique for indoor solutions has proven very costly and inaccurate primarily due to the need for high resolution clocks and the non-availability of reliable line of sight condition between the transmitter and receiver. In this dissertation, localization and tracking of wireless devices using radio signal strength (RSS) measurements in an indoor environment is undertaken. This dissertation is presented in the form of five papers. The first two papers deal with localization and placement of receivers using a range-based method where the Friis transmission equation is used to relate the variation of the power with radial distance separation between the transmitter and receiver. The third paper introduces the cross correlation based localization methodology. Additionally, this paper also presents localization of passive RFID tags operating at 13.56MHz frequency or less by measuring the cross-correlation in multipath noise from the backscattered signals. The fourth paper extends the cross-correlation based localization algorithm to wireless devices operating at 2.4GHz by exploiting shadow fading cross-correlation. The final paper explores the placement of receivers in the target environment to ensure certain level of localization accuracy under cross-correlation based method. The effectiveness of our localization methodology is demonstrated experimentally by using IEEE 802.15.4 radios operating in fading noise rich environment such as an indoor mall and in a laboratory facility of Missouri University of Science and Technology. Analytical performance guarantees are also included for these methods in the dissertation --Abstract, page iv

Directional Antenna System-Based DoA/RSS Estimation, Localization and Tracking in Future Wireless Networks: Algorithms and Performance Analysis

Location information plays an important role in many emerging technologies such as robotics, autonomous vehicles, and augmented reality. Already now the majority of smartphone owners use their devices' localization capabilities for a broad range of location-based services. Currently, location information in smartphones is mostly obtained in a device-centric approach, where the device to be localized, here referred to as the target node (TN), estimates its own location using, for example, the global positioning system (GPS). However, TNs with wireless communication capabilities can be localized based on their transmitted signals by a third party. In particular, localization can be implemented as a functionality of a wireless network. Depending on the application area and implementation, this network-centric approach has several advantages compared to device-centric localization, such as reducing the energy consumption within the TNs, enabling localization of non-cooperative TNs, and making location information available in the network itself. Current generation wireless networks are already capable of coarse localization. However, these existing localization capabilities do not suffice for the challenging demands of future applications. The majority of approaches moreover does not exploit the fact that an increasing number of base stations (BSs) and user devices are equipped with directional antennas. However, directional antennas enable direction of arrival (DoA) estimation that can, in turn, serve as the basis for advanced localization and location tracking. In this thesis, we thus study the application of directional antennas for localization and location tracking in future generation wireless networks. The contributions of this thesis can be grouped into two topics.First, this thesis provides a detailed study of DoA/received signal strength (RSS) estimation and localization with a group of directional antennas herein denoted as sectorized antennas. This group of antennas is of particular interest as it encompasses a broad range of directional antennas that can be implemented with a single RF front-end. Thus, the hardware complexity of sectorized antennas is low in comparison to the conventionally used antenna arrays that require multiple transceiver branches. However, at the same time this means that DoA estimation with sectorized antennas has to be implemented in a fundamentally different way. In order to address these differences, the study of sectorized antennas in this thesis includes the derivation of Cramer-Rao bounds (CRBs) for DoA/RSS estimation and localization, the proposal of three different DoA/RSS estimators, as well as numerical and analytical performance evaluations of DoA/RSS estimation and localization using sectorized antennas.Second, this thesis deals with localization based on the fusion of DoA and RSS estimates as well as DoA and time of arrival (ToA) estimates. It is shown that the combination of these estimates can result in a much increased localization performance compared to a localization based on one of these estimates alone. For the localization based on DoA/RSS estimates, a mechanism explaining this improvement is revealed by means of a CRB analysis. Thereafter, DoA/RSS-based fusion is further studied using an extended Kalman filter (EKF) as an example location tracking algorithm. Finally, an EKF is proposed that tracks the location of a TN by fusing DoA and ToA estimates. Apart from a significantly improved tracking performance, this joint DoA/ToA-EKF moreover provides estimates for the TN device clock offset and is able to localize the TN in situations where a classical DoA-only EKF fails to provide a location estimate altogether.Overall, this thesis thus provides insights into benefits of localization and location tracking using directional antennas, accompanied by specific DoA/RSS estimation, localization and location tracking solutions, as well as design guidelines for implementing localization systems in future generation wireless networks

Theory and Applications of Aperiodic (Random) Phased Arrays

A need for network centric topologies using mobile wireless communications makes it important to investigate new distributed beamforming techniques. Platforms such as micro air vehicles (MAVs), unattended ground sensors (UGSs), and unpiloted aerial vehicles (UAVs) can all benefit from advances in this area utilizing advantages in stealth, enhanced survivability and maximum maneuverability. Moreover, in this dissertation, electromagnetic radiation is investigated such that the signal power of each element is coherently added in the far-field region of a specified target direction with net destructive interference occurring in all other regions to suppress sidelobe behavior. This provides superior range and resolution characteristics for a variety of applications including; early warning radar, ballistic missile defense and search and rescue efforts. A wide variety of topologies can be used to confine geometrically these mobile random arrays for analysis. The distribution function for these topologies must be able to generalize the randomness within the geometry. By this means it is feasible to assume the random element distribution of a very large volumetric space will yield either a normal or Gaussian distribution. Therefore the underlying assumption stands that the statistically averaged beam pattern develops from an arrangement of uniformly or Gaussian distrusted elements; both confined to a variety of geometry of radius A and is further generalized using a simple theory based upon the Fourier Transform. Hence, this theory will be derived and serve as the foundation for advanced performance characteristics of these arrays such as its ability for sidelobe tapering, adaptive nulling and multi beam control. In addition it will be shown that for the most ideal of conditions a steerable beam pattern free of sidelobe behavior (better known as a Gaussian distribution) is quite possible. As well these random array structures will be shown to provide superior bandwidth capability over tradiational array structures since they are frequency independent. Last of all a summary of the random array analysis and its results concludes this dissertation

Spacelab Science Results Study

Beginning with OSTA-1 in November 1981 and ending with Neurolab in March 1998, a total of 36 Shuttle missions carried various Spacelab components such as the Spacelab module, pallet, instrument pointing system, or mission peculiar experiment support structure. The experiments carried out during these flights included astrophysics, solar physics, plasma physics, atmospheric science, Earth observations, and a wide range of microgravity experiments in life sciences, biotechnology, materials science, and fluid physics which includes combustion and critical point phenomena. In all, some 764 experiments were conducted by investigators from the U.S., Europe, and Japan. The purpose of this Spacelab Science Results Study is to document the contributions made in each of the major research areas by giving a brief synopsis of the more significant experiments and an extensive list of the publications that were produced. We have also endeavored to show how these results impacted the existing body of knowledge, where they have spawned new fields, and if appropriate, where the knowledge they produced has been applied