An adaptive MIMO transmission technique for LDPC coded OFDM cellular systems

An adaptive MIMO transmission scheme using QAM and LDPC code is proposed for an OFDM cellular system employing FDD. By approximating the LLR distribution to a Gaussian distribution, only two parameters, the mean and the normalized standard deviation, are required to be sent to the transmitter, which requires only a few more bits than those required in currently used single carrier cellular systems, such as cdma2000-1x EV-DO. It is shown by computer simulation that the proposed adaptive transmission scheme can provide up to 2∼3 dB gain over the conventional system using the mean SNR only, at the expense of only 3 more bits in the feedback information.