[Paper Review] Positioning and Sensing in 6G: Gaps, Challenges, and Opportunities

Ali Behravan, Vijaya Yajnanarayana+9 more|arXiv (Cornell University)|Nov 2, 2022

Indoor and Outdoor Localization Technologies4 citations

TL;DR

This paper presents a unified vision for integrated positioning and sensing in 6G, identifying key use cases, performance requirements, and critical gaps between current 5G capabilities and future 6G demands. It proposes joint communication, sensing, localization, and computing (JRC2LS) as a core enabler, leveraging large bandwidths, massive MIMO, RIS, and advanced signal processing to achieve decimeter-level accuracy and low-latency sensing, while addressing hardware impairments and harsh propagation conditions as major challenges.

ABSTRACT

Among the key differentiators of 6G compared to 5G will be the increased emphasis on radio based positioning and sensing. These will be utilized not only for conventional location-aware services and for enhancing communication performance, but also to support new use case families with extreme performance requirements. This paper presents a unified vision from stakeholders across the value chain in terms of both opportunities and challenges for 6G positioning and sensing, as well as use cases, performance requirements, and gap analysis. Combined, this motivates the technical advances in 6G and guides system design.

Motivation & Objective

• To identify and analyze the key use cases requiring extreme positioning and sensing performance in 6G networks.
• To define the performance requirements—particularly accuracy, latency, availability, resolution, and integrity—for next-generation positioning and sensing services.
• To conduct a comprehensive gap analysis between current 5G capabilities and the envisioned 6G system requirements.
• To highlight the role of integrated radio waveforms and infrastructure (e.g., RIS, massive MIMO) in enabling joint communication, sensing, localization, and computing (JRC2LS).
• To identify and address fundamental challenges such as hardware impairments and harsh radio channel conditions in mmWave and sub-THz bands.

Proposed method

• Conducts a gap analysis comparing 5G state-of-the-art (SOTA) positioning and sensing performance against 6G use case requirements.
• Proposes joint waveforms and hardware designs for integrated communication, sensing, localization, and computing (JRC2LS) in 6G.
• Utilizes radio-based techniques such as TDoA, AoA/AoD, RTT, and OTFS/OFDM waveforms for high-accuracy positioning and sensing.
• Analyzes the impact of hardware impairments (phase noise, mutual coupling, nonlinear distortion) on positioning and sensing accuracy.
• Evaluates propagation channel characteristics across FR1, FR2, and sub-THz bands, including multipath resolvability and Doppler spread.
• Introduces the concept of infrastructure reference nodes (IRNs) and digital twins to support environment-aware radio resource management and beamforming.

Experimental results

Research questions

• RQ1 What are the key 6G use cases that demand extreme positioning and sensing performance beyond current 5G capabilities?
• RQ2 What are the specific KPIs (accuracy, latency, availability, resolution) required by 6G positioning and sensing services compared to 5G?
• RQ3 What are the fundamental technical gaps between current SOTA in positioning and sensing and the requirements of 6G use cases?
• RQ4 How do hardware impairments such as phase noise and mutual coupling degrade positioning and sensing performance in 6G systems?
• RQ5 What are the challenges posed by harsh propagation environments in mmWave and sub-THz bands for accurate sensing and localization?

Key findings

• A significant performance gap exists between 5G capabilities and 6G requirements in three key KPIs: positioning accuracy (sub-meter), latency (sub-100ms), and availability (99.999%).
• Sensing requirements exceed current SOTA in accuracy and resolution, especially for detecting small or non-radiating objects in complex environments.
• Hardware impairments such as phase noise and nonlinear distortion significantly degrade ranging and angle estimation accuracy, requiring dynamic compensation.
• At mmWave and sub-THz bands, channel conditions become more dynamic due to increased Doppler spread and rapid fading, demanding more frequent channel updates and robust models.
• Large bandwidths and massive MIMO arrays improve multipath resolvability and positioning accuracy, but require advanced signal processing and calibration to mitigate impairments.
• Reconfigurable intelligent surfaces (RIS) and joint communication-sensing waveforms (e.g., JRC2LS) are identified as key enablers for achieving low-latency, high-accuracy sensing and localization in 6G.