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Optimal DoF of the K-User Broadcast Channel With Delayed and Imperfect Current CSIT

Abstract : This work identifies the optimal Degrees-ofFreedom (DoF) of the K-User MISO Broadcast Channel (BC) with delayed Channel-State Information at the Transmitter (CSIT) and with additional current noisy CSIT where the current channel estimation error scales in P -α for α ∈ [0, 1]. These two settings had in the past been studied separately; the setting of imperfect current CSIT has attracted considerable interest over the last decade, while the setting of delayed CSIT was studied in the seminal work of Maddah-Ali and Tse in 2010 1 where an optimal DoF of K/ Σ k=1 K 1/k was established. Since k=1 then there have been several efforts to combine the two settings of delayed and imperfect-current CSIT. Our work establishes for the first time the optimal DoF in this joint setting, capitalizing on a novel transmission scheme that is presented here, which combines a structurally new approach of handling past and current interference, to achieve the optimal performance. We establish the once elusive optimal DoF to be of the form 1 αK + (1 - α)K/(K/ Σ k=1 K 1/k). This further shows that the two k=1 types of DoF gains, from current and delayed CSIT, can be combined additively.
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Submitted on : Friday, February 4, 2022 - 9:33:52 AM
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Paul de Kerret, David Gesbert, Jingjing Zhang, Petros Elia. Optimal DoF of the K-User Broadcast Channel With Delayed and Imperfect Current CSIT. IEEE Transactions on Information Theory, Institute of Electrical and Electronics Engineers, 2020, 66 (11), pp.7056-7066. ⟨10.1109/TIT.2020.3023579⟩. ⟨hal-03556490⟩



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