Experimental evaluation of open-loop precoding MIMO using the testbed targeted at IMT-Advanced system

This paper presents an experimental evaluation of open-loop precoding MIMO (multiple input multiple output) using a testbed targeted at IMT-Advanced systems. Open-loop MIMO is realized by applying rotational OFDM (R-OFDM), that is previously proposed by authors, to MIMO transmission. MIMO R-OFDM is more robust with respect to correlated channels than conventional open-loop MIMO-OFDM, because it optimizes the distances between the constellation points using simple phase rotation. The angle of phase rotation depends on the modulation orders and coding rate, hence the receiver does not need to feed the CSI (channel state information) back to the transmitter. In this paper, MIMO R-OFDM is implemented in a testbed targeted at IMT-Advanced systems, it is then evaluated experimentally and by computer simulations. The results of the evaluation reveal that MIMO R-OFDM is effective in correlated channels, and the gain in terms of the CIR (carrier to interference ratio) with respect to conventional MIMO OFDM to achieve PER (packet error rate) = 0.01 is about 1.5 dB when MIMO R-OFDM is used in correlated channels.