Rate Splitting for MIMO Wireless Networks: A Promising PHY-Layer Strategy for LTE Evolution

TL;DR

This paper explores rate-splitting as a promising PHY-layer strategy to improve spectral and energy efficiencies in MIMO wireless networks, especially under imperfect CSIT conditions, offering advantages over traditional methods.

Contribution

It introduces rate-splitting techniques for MIMO networks, demonstrating their potential to enhance efficiency and reliability despite CSIT inaccuracies, and discusses implications for LTE evolution.

Findings

Rate-splitting improves spectral efficiency over conventional methods.

It reduces CSI feedback overhead significantly.

Enhances reliability in multi-user MIMO scenarios.

Abstract

MIMO processing plays a central part towards the recent increase in spectral and energy efficiencies of wireless networks. MIMO has grown beyond the original point-to-point channel and nowadays refers to a diverse range of centralized and distributed deployments. The fundamental bottleneck towards enormous spectral and energy efficiency benefits in multiuser MIMO networks lies in a huge demand for accurate channel state information at the transmitter (CSIT). This has become increasingly difficult to satisfy due to the increasing number of antennas and access points in next generation wireless networks relying on dense heterogeneous networks and transmitters equipped with a large number of antennas. CSIT inaccuracy results in a multi-user interference problem that is the primary bottleneck of MIMO wireless networks. Looking backward, the problem has been to strive to apply techniques designed for perfect CSIT to scenarios with imperfect CSIT. In this paper, we depart from this conventional approach and introduce the readers to a promising strategy based on rate-splitting. Rate-splitting relies on the transmission of common and private messages and is shown to provide significant benefits in terms of spectral and energy efficiencies, reliability and CSI feedback overhead reduction over conventional strategies used in LTE-A and exclusively relying on private message transmissions. Open problems, impact on standard specifications and operational challenges are also discussed.