[Paper Review] White Paper on Broadband Connectivity in 6G

Nandana Rajatheva, Italo Atzeni+23 more|arXiv (Cornell University)|Apr 29, 2020

Advanced Wireless Communication TechnologiesEngineering95 references291 citations

TL;DR

This white paper surveys the road to broadband 6G connectivity, detailing infrastructure, spectrum, and protocol enablers to achieve Tbps-scale peak rates and ultra-reliable low-latency communications, including integration with space networks and holographic radio concepts.

ABSTRACT

This white paper explores the road to implementing broadband connectivity in future 6G wireless systems. Different categories of use cases are considered, from extreme capacity with peak data rates up to 1 Tbps, to raising the typical data rates by orders-of-magnitude, to support broadband connectivity at railway speeds up to 1000 km/h. To achieve these goals, not only the terrestrial networks will be evolved but they will also be integrated with satellite networks, all facilitating autonomous systems and various interconnected structures. We believe that several categories of enablers at the infrastructure, spectrum, and protocol/ algorithmic levels are required to realize the intended broadband connectivity goals in 6G. At the infrastructure level, we consider ultra-massive MIMO technology (possibly implemented using holographic radio), intelligent reflecting surfaces, user-centric and scalable cell-free networking, integrated access and backhaul, and integrated space and terrestrial networks. At the spectrum level, the network must seamlessly utilize sub-6 GHz bands for coverage and spatial multiplexing of many devices, while higher bands will be used for pushing the peak rates of point-to-point links. The latter path will lead to THz communications complemented by visible light communications in specific scenarios. At the protocol/algorithmic level, the enablers include improved coding, modulation, and waveforms to achieve lower latencies, higher reliability, and reduced complexity. Different options will be needed to optimally support different use cases. The resource efficiency can be further improved by using various combinations of full-duplex radios, interference management based on rate-splitting, machine-learning-based optimization, coded caching, and broadcasting.

Motivation & Objective

• Motivate the 6G broadband connectivity use case as a core driver for next-generation wireless systems.
• Identify infrastructure, spectrum, and protocol/algorithm enablers required to achieve Tbps peak rates and global coverage.
• Propose a multi-layer approach combining ultra-massive MIMO, intelligent reflecting surfaces, integrated space-terrestrial networks, and advanced coding/waveforms.
• Highlight KPI targets and spectrum strategies across sub-6 GHz to THz and visible light bands.

Proposed method

• Survey of proposed 6G broadband enablers across three levels: infrastructure, spectrum, and protocol/algorithmic developments.
• Analysis of use cases and KPIs to motivate design choices for Tbps-scale broadband connectivity.
• Description of holographic radio as a path to continuous-aperture massive MIMO and high-dimensional spatial multiplexing.
• Evaluation of IRS and integrated networks to enhance propagation and coverage in higher frequencies.

Experimental results

Research questions

• RQ1 What are the enabling technologies at the infrastructure, spectrum, and protocol levels needed to realize 6G broadband connectivity?
• RQ2 How can 6G achieve Tbps peak rates while ensuring ultra-low latency, extremely high reliability, and wide-area coverage?
• RQ3 What roles do ultra-massive MIMO, holographic radio, and intelligent reflecting surfaces play in 6G performance gains?
• RQ4 How can space-terrestrial integration and edge computing support 6G broadband use cases across diverse environments?
• RQ5 What spectrum strategy across sub-6 GHz to THz and optical bands best supports 6G broadband goals?

Key findings

• 6G broadband aims for peak rates up to 1 Tbps with user-experienced rates around 1 Gbps and latency down to 0.1 ms in some use cases.
• A multi-layer enabler approach is required, combining infrastructure (ultra-maste MIMO, holographic radio, IRS, integrated access/backhaul, space-terrestrial networks), spectrum (sub-6 to THz and VLC), and protocol/algorithmic advances (coding, modulation, waveform, duplex, ML-based optimization).
• Ultra-dense, coordinated networks (cell-free, edge computing) and integrated space/terrestrial systems are central to achieving full coverage.
• Holographic radio and continuous-aperture active antennas enable vastly higher spatial multiplexing than beam-space approaches, especially at high frequencies.
• Intelligent reflecting surfaces offer passive beamforming gains to mitigate propagation challenges in higher bands and support network optimization.
• ML-aided optimization, coded caching, and rate-splitting are highlighted as key protocol-level tools for efficiency and adaptability.