Degrees of Freedom of Time Correlated MISO Broadcast Channel with Delayed CSIT

TL;DR

This paper characterizes the optimal degrees of freedom in a two-user MISO broadcast channel with time correlation and imperfect current channel knowledge, proposing a scheme that interpolates between existing strategies.

Contribution

It introduces a new scheme that combines quantization, multicasting, and private message broadcasting to optimize degrees of freedom under correlated channel conditions.

Findings

Achieves the optimal degree of freedom region for the channel.

Bridges the gap between no current CSI and perfect CSI schemes.

Provides a unified approach for correlated MISO broadcast channels.

Abstract

We consider the time correlated multiple-input single-output (MISO) broadcast channel where the transmitter has imperfect knowledge on the current channel state, in addition to delayed channel state information. By representing the quality of the current channel state information as P^-{\alpha} for the signal-to-noise ratio P and some constant {\alpha} \geq 0, we characterize the optimal degree of freedom region for this more general two-user MISO broadcast correlated channel. The essential ingredients of the proposed scheme lie in the quantization and multicasting of the overheard interferences, while broadcasting new private messages. Our proposed scheme smoothly bridges between the scheme recently proposed by Maddah-Ali and Tse with no current state information and a simple zero-forcing beamforming with perfect current state information.