Optimal DoF region of the K-User MISO BC with Partial CSIT

TL;DR

This paper derives the optimal DoF region for a K-user MISO broadcast channel with partial CSIT, demonstrating that Rate-Splitting is essential for achieving this optimal performance.

Contribution

It provides the first complete characterization of the DoF region under partial CSIT and highlights the importance of Rate-Splitting in this context.

Findings

Derived the optimal DoF region for the K-user MISO BC with partial CSIT.

Showed that Rate-Splitting achieves the optimal DoF region.

Established the impact of CSIT quality on DoF performance.

Abstract

We consider the $K$-User Multiple-Input-Single-Output (MISO) Broadcast Channel (BC) where the transmitter, equipped with $M$ antennas, serves $K$ users, with $K \leq M$. The transmitter has access to a partial channel state information of the users. This is modelled by letting the variance of the Channel State Information at the Transmitter (CSIT) error of user $i$ scale as $O(P^{-\alpha_i}$) for the Signal-to-Noise Ratio (SNR) $P$ and some constant $\alpha_i \geq 0$. In this work we derive the optimal Degrees-of-Freedom (DoF) region in such setting and we show that Rate-Splitting (RS) is the key scheme to achieve such a region.