DoF analysis of the K-user MISO broadcast channel with hybrid CSIT

Borzoo Rassouli,Chenxi Hao,Bruno Clerckx

doi:10.1109/icc.2015.7248982

Borzoo Rassouli, Chenxi Hao + Show 1 more

Open Access

https://doi.org/10.1109/icc.2015.7248982

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Publication Date: Jun 1, 2015
Citations: 19	License type: cc0

Affiliation: Imperial College London, Korea University

Abstract

We consider a K-user multiple-input single-output (MISO) broadcast channel (BC) where the channel state information (CSI) of user i(i = 1, 2, ..., K) may be either instantaneously perfect (P), delayed (D) or not known (N) at the transmitter with probabilities λ P i , λ D i and λ N i , respectively. In this setting, according to the three possible CSIT for each user, knowledge of the joint CSIT of the K users could have at most 3 K states. Although the results by Tandon et al. show that for the symmetric two user MISO BC (i.e., λ Q i = λ Q , ∀ i ∈ {1, 2}, Q ∈ {P, D, N}), the Degrees of Freedom (DoF) region depends only on the marginal probabilities, we show that this interesting result does not hold in general when K ≥ 3. In other words, the DoF region is a function of all the joint probabilities. In this paper, given the marginal probabilities of CSIT, we derive an outer bound for the DoF region of the K-user MISO BC. Subsequently, we investigate the achievability of the outer bound in some scenarios. Finally, we show the dependence of the DoF region on the joint probabilities.

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