Effects of Non-Ideal Channel Feedback on Dual-Stream MIMO-OFDMA System Performance

In this paper we analyze the downlink OFDMA system-level performances of a 2times2 dual-stream MIMO multiuser transmission scheme under the assumptions of partial and noisy channel quality indicator (CQI) feedback available from the terminals. The effects on the CQI feedback of the terminal measurement and estimation errors, quantization errors, uplink reporting format and delays are included. Two reduced CQI reporting schemes are evaluated in macro and microcell scenarios when operating in combination with a MIMO outer loop link adaptation (OLLA) and a MIMO aware frequency domain packet scheduling (FDPS) algorithm. We show that, by using OLLA and with a proper choice of the CQI reporting scheme for dual-stream MIMO, the required CQI feedback overhead can be reduced by 90% while limiting the cell throughput losses to less than 10%.