A Reduced Complexity Multi-User Massive MIMO Precoding Method

Considering the upcoming future generation of mobile communication standards, Multi-User Massive MIMO (MU-MMIMO) is a well-known method of increasing the overall cell throughput. Such a scenario suffers from a high computational complexity because of the transmit precoding that is used to eliminate the inter-user interference. The paper proposes a reduced complexity precoding method applicable at the base station (BS) side of a downlink multiuser scenario. The reduction in complexity is achieved by reducing the number of low-level operations involved in the QR decomposition without any effect on the overall system performance. The method is shown to be compatible with two of the most widespread implementations of the QR decomposition: Givens rotations and Householder reflections. The proposed algorithm is evaluated in terms of required number of multiply-and-accumulate (MAC) operations and compared with its unmodified version, showing a net decrease of computational complexity.