Design and Implementation of a DSP-Based MIMO System Prototype for Real-Time Demonstration and Indoor Channel Measuremen
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Design and Implementation of a DSP-Based MIMO System Prototype for Real-Time Demonstration and Indoor Channel Measurements Raqibul Mostafa, Ran Gozali, Ramesh Chembil Palat, Max Robert, William G. Newhall, Brian D. Woerner, and Jeffrey H. Reed Mobile and Portable Radio Research Group, Virginia Polytechnic Institute and State University, 432 Durham Hall, Mail Stop 0350, Blacksburg, VA 24061, USA Emails: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected] Received 27 January 2004; Revised 28 February 2005 The design and implementation of the Virginia Tech Space-Time Advanced Radio (VT-STAR), a multiple antenna element spacetime (ST) processing prototype testbed, is presented. The testbed is a research tool for comparing practical and theoretical performance metrics (e.g., throughput, link reliability) in different wireless channel conditions. The prototype builds around softwaredefined radio (SDR) concepts on a DSP platform and provides the flexibility to implement various forms of ST techniques. Different components of the system are described in detail, including the software implementation, I/O schemes with custom hardware, and data transfer mechanisms between the DSP and the host PC. Two different example realizations are presented, a real-time demonstration and an offline measurement tool. Finally, some representative measurement results obtained in indoor environments are presented. These results show VT-STAR to be a promising tool for performing MIMO experiments and generating channel measurements that can complement simulation studies in this area. Keywords and phrases: space-time codes, MIMO, DSP C67, prototype, wireless communications.
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INTRODUCTION
With the integration of Internet and multimedia applications in next-generation wireless communications, the demand for reliable high-data-rate services is rapidly growing. The wireless channel introduces a variety of impairments to the transmitted signal, including large-scale and smallscale fading, channel-induced intersymbol interference (ISI), noise and multiuser interference. To mitigate these phenomena, diversity can be exploited to enhance performance over a broad range of channel realizations. Space-time coding (STC) schemes implement multiple forms of diversity by combining the channel code design and the use of multiple transmit and receive antennas, thereby creating a multipleinput multiple-output (MIMO) channel. The encoded data is split into nT streams that are simultaneously transmitted using nT transmit antennas. The received signal is a linear superposition of these simultaneous transmitted symbols corrupted by noise, interference, and channel-induced ISI. Space-time decoding algorithms using channel estimation techniques are incorporated at the receiver to achieve diversity and coding gains. Various techniques that exploit the capabilities of MIMO channels have been proposed in the literature. Among them, the main classes are
(i) BLAST—Bell Labs layered space-time architectur
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