Hybrid Analog and Digital Precoding: From Practical RF System Models to Information Theoretic Bounds

TL;DR

This paper develops detailed RF system models for hybrid analog-digital precoding in millimeter wave systems, revealing significant performance degradation due to practical RF limitations and emphasizing the need for redesigned precoders.

Contribution

It introduces fundamental RF system models for hybrid precoding and quantifies their impact on achievable rates, highlighting the importance of practical considerations in precoder design.

Findings

Hybrid precoding suffers from notable performance degradation when RF limitations are considered.

The performance gap between ideal and practical hybrid precoders is quantified.

Redesigning hybrid precoders is necessary to achieve optimal rates under real-world constraints.

Abstract

Hybrid analog-digital precoding is a key millimeter wave access technology, where an antenna array with reduced number of radio frequency (RF) chains is used with an RF precoding matrix to increase antenna gain at a reasonable cost. However, digital and RF precoder algorithms must be accompa- nied by a detailed system model of the RF precoder. In this work, we provide fundamental RF system models for these precoders, and show their impact on achievable rates. We show that hybrid precoding systems suffer from significant degradation, once the limitations of RF precoding network are accounted. We subsequently quantify this performance degradation, and use it as a reference for comparing the performance of different precoding methods. These results indicate that hybrid precoders must be redesigned (and their rates recomputed) to account for practical factors.