Coordinated multi-point (CoMP) transmission is a general method for mitigating the inter-cell interference in a cellular network through the use of multi-user precoding across neighboring basestations. In this paper, we investigate the system performance of MMSE-based multi-user precoding in a cellular network with CoMP transmission. An iterative algorithm that exploits the duality between the downlink broadcast channel and the uplink multi-access channel is used to compute the multi-user precoding matrices. The algorithm uses the knowledge of the channel error covariance during the precoder computation to alleviate the impact of channel uncertainty at the network. We simulate the system performance of various MMSE-based precoders under the CoMP setting using a realistic MIMO channel model and compare them with those of the zero-forcing precoders. We show that the error-compensated MMSE precoder is more robust towards channel uncertainty and can significantly outperform zero-forcing precoding at high loads.
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