SABA: A Testbed for a Real-Time MIMO System
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SABA: A Testbed for a Real-Time MIMO System ¨ 2 Christoph Degen,1 Wilhem Keusgen,3 Gholamreza Alirezaei,1 Daniel Borkowski,1 Lars Bruhl, 1 Frank Geschewski, Christos Oikonomopoulos,1 and Bernhard Rembold1 1 Institute
of High Frequency Technology, RWTH Aachen University, Melatener Straße 25, 52056 Aachen, Germany Radio Communication Systems GmbH & Co. KG, 89075 Ulm, Germany 3 Fraunhofer Institute for Telecommunications, Heinrich-Hertz Institute, Einsteinufer 37, 10587 Berlin, Germany 2 Telefunken
Received 6 December 2004; Revised 4 August 2005; Accepted 22 August 2005 The growing demand for high data rates for wireless communication systems leads to the development of new technologies to increase the channel capacity thus increasing the data rate. MIMO (multiple-input multiple-output) systems are best qualified for these applications. In this paper, we present a MIMO test environment for high data rate transmissions in frequency-selective environments. An overview of the testbed is given, including the analyzed algorithms, the digital signal processing with a new highly parallel processor to perform the algorithms in real time, as well as the analog front-ends. A brief overview of the influence of polarization on the channel capacity is given as well. Copyright © 2006 Hindawi Publishing Corporation. All rights reserved.
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INTRODUCTION AND MOTIVATION
The increasing demand for high data rates for wireless communication requires efficient use of the available bandwidth. Multiple-input multiple-output (MIMO) systems provide exploitation of spatial diversity and/or spatial multiplexing and enables SDMA (space division multiple access). These systems comprise on the one hand point-to-point MIMO systems where both at the transmitter and the receiver site antenna arrays are used; on the other hand, also multiuser MIMO systems with a multiantenna base station (or access point) and several users equipped with one or several antennas can be considered. However, for evaluating such systems, it is essential to also analyze their efficiency with respect to implementation issues. That is, besides spectral efficiency, one needs to consider complexity of digital signal processing as well as requirements concerning analog components. At the Institute of High Frequency Technology at RWTH Aachen University, a testbed for a real-time MIMO system with a broadband air interface has been developed. It has been designed for evaluation of concepts and for proposing new realizations. The testbed consists of one base station and several user terminals. The base station is equipped with an antenna array and the user terminals are equipped with single antennas. However, several users can be grouped together to one multiantenna user station. Our research is focused on future wideband WLAN systems. This paper is organized as follows. First, a general overview of the real-time MIMO testbed is given. Second, the in-
fluence of polarization on channel capacity is described. Third, some of the algorithms and the theoretical background for signal proces
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