Adaptive Multi-Tx Multi-Rx MIMO Transmission Scheme for LTE-Advanced Downlink

Multiple-input multiple output (MIMO) spatial multiplexing has been adopted by 3GPP long term evolution (LTE) to increase the peak spectrum efficiency. However, it will lose its effectiveness for cell edge users due to the inter-cell interference (ICI). Therefore, 3GPP LTE-Advanced (LTE-A) is considering to introduce some multi-cell cooperative transmission techniques to solve this problem. In this paper, we first propose the distributed multi-Tx multi-Rx (MTMR) MIMO spatial multiplexing for LTE-A downlink, which only needs partial cooperation, so the heavy backhauling overhead and the high implementation complexity encountered in the traditional full cooperation scheme can be avoided. Meanwhile, because of the efficient utilization of multi-cell transmit power and spatial degree of freedom, a higher spectrum efficiency can be achieved by MTMR MIMO spatial multiplexing in good channel conditions compared with the other partial cooperation schemes. Then in order to ensure the highest possible cell edge spectrum efficiency to be achieved in different channel conditions, we further integrate multiple distributed cooperation modes into the same framework and introduce a mechanism of adaptive cooperation mode selection. Both qualitative analysis and quantitative simulations show the proposal's effectiveness and indicate it a promising candidate for the cooperative transmission in LTE-A downlink.