Hybrid Analog-Digital Precoding Revisited under Realistic RF Modeling

TL;DR

This paper critically evaluates hybrid analog-digital precoding in 5G, considering realistic RF losses and component models, revealing significant impacts on performance and energy efficiency, and comparing different RF network architectures.

Contribution

It introduces realistic RF component models into hybrid precoding analysis, highlighting the impact of practical factors on system performance and energy efficiency.

Findings

RF losses significantly reduce hybrid precoding performance

Butler networks outperform FC-ABFN in large RF chain systems

Practical RF modeling is essential for accurate hybrid precoding evaluation

Abstract

In this paper we revisit hybrid analog-digital precoding systems with emphasis on their modelling and radio-frequency (RF) losses, to realistically evaluate their benefits in 5G system implementations. For this, we decompose the analog beamforming networks (ABFN) as a bank of commonly used RF components and formulate realistic model constraints based on their S-parameters. Specifically, we concentrate on fully-connected ABFN (FC-ABFN) and Butler networks for implementing the discrete Fourier transform (DFT) in the RF domain. The results presented in this paper reveal that the performance and energy efficiency of hybrid precoding systems are severely affected, once practical factors are considered in the overall design. In this context, we also show that Butler RF networks are capable of providing better performances than FC-ABFN for systems with a large number of RF chains.