Multiple input-multiple output (MIMO) is an attractive technology for future wireless systems. MIMO communication, enabled by the use of multiple transmit and multiple receive antennas, is known for its high spectral efficiency as well as its robustness against fading and interference. Combining MIMO with orthogonal frequency division multiplexing (OFDM), it is possible to significantly reduce receiver complexity as OFDM greatly simplifies equalization at the receiver. MIMO-OFDM is of great interest in many developing wireless standards thus the study of MIMO-OFDM in realistic environments is of great importance. This paper describes a MIMO-OFDM prototype built using a flexible, software defined radio (SDR) system architecture in conjunction with commercially available hardware. An emphasis on software permits a focus on algorithm and system design issues, rather than implementation and hardware configuration. The penalty of this flexibility, however, is that the ease of use comes at the expense of overall throughput. To illustrate the benefits of the proposed architecture, applications to MIMO-OFDM system prototyping and preliminary MIMO channel measurements are presented. A detailed description of the hardware is provided along with downloadable software to reproduce the system.
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