4x4 MIMO experimental test-bed using COTS at ISM band

This paper presents the implementation of a 4x4 multiple input multiple output (MIMO) test-bed that is employed for channel characterization using virtual MIMO indoor channel sounding technique. The 4x4 MIMO operates at ISM frequency of 2.45GHz with 5MHz of bandwidth using low cost commercially available off-the-shelf components (COTS). The system benefits from direct conversion transceiver units, reported before. Channel propagation measurements were performed in a rich multi-path environment by employing a virtual MIMO indoor wireless channel sounding as well as a direction of arrival (DOA) estimation algorithms. The channel sounding technique employs sequential switching of 1x4 Single Input Multiple Output (SIMO) channels to realize a virtual 4x4 MIMO experiments in a stationary channel environment. A hardware calibration method is also developed as a critical part of the MIMO evaluation. The DOA experiment, which employs a linear four-element patch antenna array at the receiver and a single patch antenna at the transmitter, pro-Odes a maximum of 15 degrees offset using Bartlett algorithm. The measured channel response matrix is also verified through comparison with other published results.