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Dynamic-Cell-Based Macro Coordination for Massively Distributed MIMO Systems

The massive multiple input multiple output (MIMO) technique is a promising candidate to enormously increase the capacity of wireless networks. In a massive MIMO system, coordinated signal processing among different antennas is crucial to cope with the inevitable co-channel interference. However, it is normally difficult to perform perfect coordination in practical applications, due to the challenging requirement of global channel state information at the transmitter (CSIT). To solve this problem, this paper considers a massively distributed MIMO model, and presents dynamic-cell (DC)-based macro coordination, which requires only the instantaneous intra-DC CSIT and the slowly-varying large-scale inter-DC CSIT. Particularly, we first divide the system into a number of coupled user-centric DCs. Perfect coordination in the form of maximum ratio transmission (MRT) is adopted locally within each DCs based on instantaneous intra-DC CSIT. Then, we propose an inter-DC coordination approach termed as enhanced MRT to mitigate the inter-DC interference. The coordination is designed on the basis of large-scale inter-DC CSIT, which thus is referred to as macro coordination. Simulation results demonstrate that the proposed DC-based macro coordination can achieve a satisfactory performance gain in terms of system sum rate, while requiring much less CSIT than traditional schemes.