Integrated Access and Backhaul in Millimeter-Wave Cellular: Benefits and Challenges

TL;DR

This paper reviews the benefits and challenges of integrated access and backhaul in mmWave 5G systems, focusing on multi-hop, multi-beam, and multi-connectivity functionalities and their impact on throughput and load balancing.

Contribution

It provides a system-level analysis of advanced functionalities in IAB systems, highlighting their effects on throughput and network resilience in mmWave 5G deployments.

Findings

Multi-hopping and multi-beaming significantly improve throughput.

Multi-connectivity enables load balancing in blocked mmWave links.

Advanced functionalities enhance network performance without requiring multi-connectivity.

Abstract

The recently proposed NR-ready integrated access and backhaul (IAB) architecture promises to bring a cost-efficient deployment solution for both coverage extension and capacity boosting in future 5G/5G+ systems. While its impact on the coverage extension was thoughtfully addressed in the literature, the effect of advanced functionalities such as multi-hop, multi-connectivity, and multi-beam operations on the throughput remains unclear. We review and characterize the system-level impact of these capabilities on the performance of self-backhauled IAB systems operating in half-duplex mode and utilizing millimeter-wave (mmWave) technology across both access and backhaul. Our results indicate that the throughput gain of multi-hopping and multi-beaming is significant even without multi-connectivity operation. Another important learning is that in all-mmWave systems with link blockage, multi-connectivity with link switching allows achieving self-load balancing. Finally, we outline future research directions.