Low complexity full diversity full rate code for closed loop MIMO

Full diversity full rate (FDFR) space-time coding for open loop multiple antenna systems is attractive because of high data rate and good performance, but its decoding is computationally intensive. In this paper, we propose a low complexity adaptive FDFR code for closed loop multiple input multiple output (MIMO) systems. We show that with only channel singular vector knowledge at the transmitter, the open loop FDFR code can be adapted to the channel while maintaining the special layer structure of the code at the receiver. That special layer structure enables us to decouple the joint detection into optimal, but separate, decoding of each of the different layers which reduces the complexity exponent. The proposed low complexity adaptive scheme maintains the full diversity order. To fully exploit channel knowledge and improve the performance, adaptive power loading is also incorporated with the information of the singular values of the channel. The optimal loading scheme is derived from the upper bound of the symbol vector error rate, and the loading coefficients can be seen as match filtering to the singular values of the channel. The proposed scheme can also be implemented by spatial multiplexing with adaptive linear precoding.