A MIMO hardware demonstrator: application of space-time block codes

We present a multiple antenna system for industrial, scientific, and medical (ISM)-band transmission (MASI). The hardware demonstrator was developed and realized at our institute. It enables the multiple input multiple output (MIMO)-communication applications and is capable of transmitting arbitrary signals using the 8 transmit and 8 receive antennas in parallel. It operates in the 2.4 GHz ISM-band. The hardware concept is introduced and some design specifications are discussed. As an application example, we focus on one specific class of transmit diversity schemes: orthogonal space-time block codes (OSTBC). Channel and carrier offset estimation are essential tasks in coherent receivers. However, there are also some kind of error sources due to the imperfections of the employed algorithm. We show, by simulation and measurement results, that the OSTBC based systems are more sensitive to channel estimation errors and/or carrier frequency offsets than the conventional single transmit antenna systems. The consequence is that the diversity gain decreases significantly in the case of estimation errors.