Imperfect CSI-based large MIMO systems

The authors address the problem of channel estimation and data detection in a large multiple-input multiple-output (MIMO) systems in Rayleigh fading environment. A method of channel estimation and data detection is proposed in large MIMO systems. The channel matrix is decomposed in N-d /2 x N-s/2 channel matrices; where N-d and N-s are the number of antennas at the destination and source, respectively. The pilot signals are clubbed with data symbols encoded in N-d /2 x N-s/2 orthogonal space-time block codes (OSTBC), and then by using the properties of null matrix, channel estimation is performed. A decoder of OSTBC data is derived by assuming the perfect channel state information (CSI) at the destination; then perfect CSI is replaced by estimated CSI in the decision metric. The expression for the moment generating function (MGF) of the received signal-tonoise ratio at the destination node is derived for the proposed scheme. Using the MGF expressions, they obtain the analytical symbol error rate for the proposed channel estimation-based decoders for general OSTBCs with M-ary phase-shift keying modulation symbols.