Reiner S. Thoma

Bio: Reiner S. Thoma is an academic researcher from Technische Universität Ilmenau. The author has contributed to research in topics: MIMO & Communication channel. The author has an hindex of 25, co-authored 85 publications receiving 2490 citations. Previous affiliations of Reiner S. Thoma include Fraunhofer Society & Japan Advanced Institute of Science and Technology.

Capacity of MIMO systems based on measured wireless channels

Abstract: We measure the capacity of multiple-input multiple-output radio systems in microcellular environments. We use a new data evaluation method that allows to evaluate the cumulative distribution function of the capacity from a single measurement. This method is based on an extraction of the parameters of the multipath components and, thereafter, a synthetic variation of their phases. In the analyzed environments, we find capacities to be about 30% smaller than would be anticipated from an idealized model. In addition, the frequency selectivity of the channel makes the CDF of the capacity steeper and, thus, increases the outage capacity, compared with the frequency-flat case, but the influence on the mean capacity is small.

Identification of time-variant directional mobile radio channels

Abstract: For the identification of the time-variant, directional structure of the mobile radio channel impulse response (CIR), a broadband vector channel sounder is described. The measurement procedure relies on periodic multifrequency excitation signals, correlation processing, and joint delay-azimuth super-resolution based on the two-dimensional (2-D) unitary ESPRIT algorithm. Problems of imperfect receiver and antenna performance as well as antenna array calibration methods are discussed. Correlation analysis of the directional impulse response records is performed in the time-frequency-spatial domain and the corresponding Doppler-delay-angular domain. Results from measurements in the 5.2 GHz frequency range in an industrial environment are presented.

Performance comparison of TOA and TDOA based location estimation algorithms in LOS environment

Abstract: In this paper, various positioning algorithms for range-based TOA and TDOA localization have been analyzed, which include the analytical method, least square method, approximate maximum likelihood method, Taylor series method, two-stage maximum likelihood method and genetic algorithm. The assumed scenario is an overdetermined system in a 3D space under line of sight (LOS) situation and a number of sensor nodes placed arbitrarily across this area. The performance of the algorithms has been compared in the assumed scenario. Both the average error and the failure rate have been investigated in terms of the number of reference nodes and the root mean squared error (RMSE) of the range estimation.

Detection and localization of persons behind obstacles using M-sequence through-the-wall radar

Abstract: We describe the architecture and design of a through-the-wall radar. The radar is applied for the detection and localization of people hidden behind obstacles. It implements a new adaptive processing technique for people detection, which is introduced in this article. This processing technique is based on exponential averaging with adopted weighting coefficients. Through-the-wall detection and localization of a moving person is demonstrated by a measurement example. The localization relies on the time-of-flight approach.

MIMO vector channel sounder measurement for smart antenna system evaluation

Abstract: For the simulation and design of smart antenna transmission principles in mobile radio, precise knowledge of the time-variant directional multipath structure in various radio environments is required. In this paper, a new real-time multiple-input-multiple-output (MIMO) vector radio channel sounder is described, which uses multiple antennas at the transmitter as well as at the receiver position. The proposed MIMO measurement principle can be effectively exploited to estimate the propagation direction at both ends of the wireless link simultaneously, and thus, dramatically enhance overall resolution of the multiple path parameters. Applying a proper antenna architecture and the multidimensional unitary ESPRIT algorithm, joint superresolution estimation of the direction of departure (DOD), time- delay of arrival (TDOA), Doppler shift, and direction of arrival (DOA) of the propagating waves becomes possible. The measured results can also be used directly for the simulation of combined transmit-receive diversity (MIMO) transmission principles and space-time (ST) adaptive receivers in a multi-user scenario. Results based on measurements in different locations are referenced, including a complicated indoor environment as is typical for industrial WLAN applications.

Millimeter Wave Mobile Communications for 5G Cellular: It Will Work!

Abstract: The global bandwidth shortage facing wireless carriers has motivated the exploration of the underutilized millimeter wave (mm-wave) frequency spectrum for future broadband cellular communication networks. There is, however, little knowledge about cellular mm-wave propagation in densely populated indoor and outdoor environments. Obtaining this information is vital for the design and operation of future fifth generation cellular networks that use the mm-wave spectrum. In this paper, we present the motivation for new mm-wave cellular systems, methodology, and hardware for measurements and offer a variety of measurement results that show 28 and 38 GHz frequencies can be used when employing steerable directional antennas at base stations and mobile devices.

Capacity limits of MIMO channels

Abstract: We provide an overview of the extensive results on the Shannon capacity of single-user and multiuser multiple-input multiple-output (MIMO) channels. Although enormous capacity gains have been predicted for such channels, these predictions are based on somewhat unrealistic assumptions about the underlying time-varying channel model and how well it can be tracked at the receiver, as well as at the transmitter. More realistic assumptions can dramatically impact the potential capacity gains of MIMO techniques. For time-varying MIMO channels there are multiple Shannon theoretic capacity definitions and, for each definition, different correlation models and channel information assumptions that we consider. We first provide a comprehensive summary of ergodic and capacity versus outage results for single-user MIMO channels. These results indicate that the capacity gain obtained from multiple antennas heavily depends on the available channel information at either the receiver or transmitter, the channel signal-to-noise ratio, and the correlation between the channel gains on each antenna element. We then focus attention on the capacity region of the multiple-access channels (MACs) and the largest known achievable rate region for the broadcast channel. In contrast to single-user MIMO channels, capacity results for these multiuser MIMO channels are quite difficult to obtain, even for constant channels. We summarize results for the MIMO broadcast and MAC for channels that are either constant or fading with perfect instantaneous knowledge of the antenna gains at both transmitter(s) and receiver(s). We show that the capacity region of the MIMO multiple access and the largest known achievable rate region (called the dirty-paper region) for the MIMO broadcast channel are intimately related via a duality transformation. This transformation facilitates finding the transmission strategies that achieve a point on the boundary of the MIMO MAC capacity region in terms of the transmission strategies of the MIMO broadcast dirty-paper region and vice-versa. Finally, we discuss capacity results for multicell MIMO channels with base station cooperation. The base stations then act as a spatially diverse antenna array and transmission strategies that exploit this structure exhibit significant capacity gains. This section also provides a brief discussion of system level issues associated with MIMO cellular. Open problems in this field abound and are discussed throughout the paper.

5G : A tutorial overview of standards, trials, challenges, deployment, and practice

Abstract: There is considerable pressure to define the key requirements of 5G, develop 5G standards, and perform technology trials as quickly as possible. Normally, these activities are best done in series but there is a desire to complete these tasks in parallel so that commercial deployments of 5G can begin by 2020. 5G will not be an incremental improvement over its predecessors; it aims to be a revolutionary leap forward in terms of data rates, latency, massive connectivity, network reliability, and energy efficiency. These capabilities are targeted at realizing high-speed connectivity, the Internet of Things, augmented virtual reality, the tactile internet, and so on. The requirements of 5G are expected to be met by new spectrum in the microwave bands (3.3-4.2 GHz), and utilizing large bandwidths available in mm-wave bands, increasing spatial degrees of freedom via large antenna arrays and 3-D MIMO, network densification, and new waveforms that provide scalability and flexibility to meet the varying demands of 5G services. Unlike the one size fits all 4G core networks, the 5G core network must be flexible and adaptable and is expected to simultaneously provide optimized support for the diverse 5G use case categories. In this paper, we provide an overview of 5G research, standardization trials, and deployment challenges. Due to the enormous scope of 5G systems, it is necessary to provide some direction in a tutorial article, and in this overview, the focus is largely user centric, rather than device centric. In addition to surveying the state of play in the area, we identify leading technologies, evaluating their strengths and weaknesses, and outline the key challenges ahead, with research test beds delivering promising performance but pre-commercial trials lagging behind the desired 5G targets.

A review of antennas and propagation for MIMO wireless communications

Abstract: Multiple-input-multiple-output (MIMO) wireless systems use multiple antenna elements at transmit and receive to offer improved capacity over single antenna topologies in multipath channels In such systems, the antenna properties as well as the multipath channel characteristics play a key role in determining communication performance This paper reviews recent research findings concerning antennas and propagation in MIMO systems Issues considered include channel capacity computation, channel measurement and modeling approaches, and the impact of antenna element properties and array configuration on system performance Throughout the discussion, outstanding research questions in these areas are highlighted

Space-Time Block Coding for Wireless Communications

Abstract: Space-time coding is a technique that promises greatly improved performance in wireless networks by using multiple antennas at the transmitter and receiver. Space-Time Block Coding for Wireless Communications is an introduction to the theory of this technology. The authors develop the topic using a unified framework and cover a variety of topics ranging from information theory to performance analysis and state-of-the-art space-time coding methods for both flat and frequency-selective fading multiple-antenna channels. The authors concentrate on key principles rather than specific practical applications, and present the material in a concise and accessible manner. Their treatment reviews the fundamental aspects of multiple-input, multiple output communication theory, and guides the reader through a number of topics at the forefront of current research and development. The book includes homework exercises and is aimed at graduate students and researchers working on wireless communications, as well as practitioners in the wireless industry.