Asymptotically Achieving Centralized Rate on the Decentralized Network MISO Channel
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In this paper, we analyze the high-SNR regime of the M x K Network MISO channel in which each transmitter has access to a different channel estimation, possibly with different accuracy. It has been recently shown that, for some regimes, this setting attains the same Degrees-of-Freedom as the ideal centralized setting with perfect CSI sharing, in which all the transmitters are endowed with the best estimate available at any transmitter. This surprising result is restricted by the limitations of the Degrees-of-Freedom metric, as it only provides information about the slope of growth of the capacity as a function of the SNR, without any insight about the possible performance at a given SNR. In this work, we analyze the affine approximation of the rate on the high-SNR regime for this decentralized Network MISO setting, presenting the unexpected result that, for a regime of antenna configurations, it is possible to asymptotically attain the same achievable rate as in the ideal centralized scenario. Consequently, it is possible to achieve the beam-forming gain of the ideal perfect-CSIT-sharing setting even if only a subset of transmitters is endowed with accurate CSI. This outcome is a consequence of the synergistic compromise between CSIT accuracy at the transmitters and consistency between the locally-computed precoders. We propose a precoding scheme achieving the previous result, which is built on an uneven structure in which some transmitters reduce the accuracy of their own precoding vector for sake of using transmission parameters that can be more easily predicated by the other transmitters.
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