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Wireless Environment as a Service Enabled by Reconfigurable Intelligent Surfaces: The RISE-6G Perspective

Emilio Calvanese Strinati, George C. Alexandropoulos, Vincenzo Sciancalepore, Marco Di Renzo, Henk Wymeersch, Dinh-Thuy Phan-huy, Maurizio Crozzoli, Raffaele D'Errico, Elisabeth De Carvalho, Petar Popovski, Paolo Di Lorenzo, Luca Bastianelli, Mathieu Belouar, Julien Etienne Mascolo, Gabriele Gradoni, Sendy Phang, Geoffroy Lerosey, Benoît Denis

arXiv:2104.06265v1cs.ITmath.IT

TL;DR

RISE-6G addresses the challenge of controlling propagation to meet competing wireless service objectives. It proposes RIS-enabled environments, supported by modeling, orchestration, and research on communication and sensing, and outlines trial use cases for evaluating this vision.

Abstract

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The design of 6th Generation (6G) wireless networks points towards flexible connect-and-compute technologies capable to support innovative services and use cases. Targeting the 2030 horizon, 6G networks are poised to pave the way for sustainable human-centered smart societies and vertical industries, such that wireless networks will be transformed into a distributed smart connectivity infrastructure, where new terminal types are embedded in the daily environment. In this context, the RISE-6G project aims at investigating innovative solutions that capitalize on the latest advances in the emerging technology of Reconfigurable Intelligent Surfaces (RISs), which offers dynamic and goal-oriented radio wave propagation control, enabling the concept of the wireless environment as a service. The project will focus on: i) the realistic modeling of RIS-assisted signal propagation, ii) the investigation of the fundamental limits of RIS-empowered wireless communications and sensing, and iii) the design of efficient algorithms for orchestrating networking RISs, in order to implement intelligent, sustainable, and dynamically programmable wireless environments enabling diverse services that go well beyond the 5G capabilities. RISE-6G will offer two unprecedented proof-of-concepts for realizing controlled wireless environments in near-future use cases.

I. INTRODUCTION

RISE-6G frames RISs as a way to control propagation in future networks, addressing the difficulty of meeting competing service, exposure, and energy objectives when the environment is treated as uncontrolled. The project’s vision combines that control with realistic modeling, communication and sensing research, and programmable wireless services.

I. INTRODUCTION

  • Future 6G requirements are projected to include up to 10 Gbps/m3 capacity, 100µs latency, 1 Tb/J energy efficiency, and 1 cm 3D localization accuracy.These targets may be required individually or in combinations.Source: §I · p. 1
  • Treating propagation as an uncontrolled black box makes it harder to meet competing service, exposure, and energy targets across different users and places.Examples include hotspot data rates, factory reliability, dense-area connectivity, limiting exposure and eavesdropping, and reducing network and device energy use.Source: §I · p. 1
  • RISs use reconfigurable elements to transform propagation and support functions such as coverage extension, obstruction mitigation, localization, and exposure control.They may coat environmental surfaces and operate as reflectors or, with active radio-frequency elements, as transceivers.Source: §I · p. 1
  • Existing RIS research addresses propagation models, settings optimization, and channel estimation, while RIS use for localization has received limited treatment.Localization can exploit multipath when location-dependent radio parameters and an environmental map or suitable model are available; otherwise, SLAM can estimate the map.Source: §I · pp. 1–2
  • RISE-6G proposes RIS-enabled propagation control to concentrate service for intended users and remove energy from regions with non-intended users.The project frames this as a wireless-environment-as-a-service paradigm with trade-offs among capacity, energy efficiency, exposure, localization, sensing, and secrecy.Source: §I · p. 2

II. RIS-EMPOWERED SYSTEM ARCHITECTURE

The RISE-6G architecture treats RISs as Layer 0 elements that control the propagation environment. Its scenario analysis prioritizes connectivity, localization and sensing, and sustainability and security use cases.

II. RIS-EMPOWERED SYSTEM ARCHITECTURE

  • RISs are framed as Layer 0 elements because they control the propagation environment, unlike conventional network infrastructure operating at PHY/MAC/link layers or above.The section introduces use cases with associated KPIs, network architectures, and deployment strategies.Source: §II · p. 2

A. Scenarios and Use Cases

  • Use-case analysis considers sub-6GHz and mmWave scenarios through reference-scenario specification, technical and economic analysis, spectrum and exposure analysis, and detailed use-case specification.The section identifies connectivity and reliability, localization and sensing, and sustainability and security as prioritized scenario areas.Source: A. Scenarios and Use Cases · p. 2
  • RISs are expected to support environment mapping, motion detection, opportunistic channel sounding, and passive radar in industrial, high-user-density, and indoor environments.The project also identifies reduced signal-radiation energy, improved energy efficiency, lower exposure, and increased security as expected benefits; train stations and Industry 4.0 are example scenarios.Source: A. Scenarios and Use Cases · p. 2

B. Metrics and KPIs for RIS-Empowered Wireless Systems

RISE-6G proposes evaluating RIS-enabled systems with conventional network metrics and additional measures for localization, sensing, secrecy, and exposure. It also envisions service-specific performance zones and trade-offs when goals conflict.

B. Metrics and KPIs for RIS-Empowered Wireless Systems

  • Evaluation spans data rate and delay, localization and sensing measures, energy efficiency, Spectral Secrecy Efficiency, and EMFE Efficiency.SSE relates intended-user spectral efficiency to data rate captured by an eavesdropper; EMFEE relates intended-user data rate to exposure of intended and non-intended users.Source: B. Metrics and KPIs for RIS-Empowered… · p. 2
  • RISE-6G envisions service-specific boosted areas for QoE, localization, secrecy, exposure avoidance, and energy efficiency, with proposed trade-offs when multiple KPIs conflict.Service providers would identify areas based on marketing insights; a high-speed train station is a primary use case for the concept.Source: B. Metrics and KPIs for RIS-Empowered… · pp. 2–3

C. Network Architectures and Deployment Strategies

The project plans scenario-specific RIS architectures in which controllers dynamically reconfigure propagation settings in response to network dynamics. RIS control may use in-band or out-of-band channels, and selected architectures are intended for trials.

C. Network Architectures and Deployment Strategies

  • RIS devices may form networks of space-time reconfigurable mirrors, with controller algorithms changing their propagation settings according to real-time or predicted network dynamics.Architectures are specified for each scenario using its application needs and KPIs.Source: C. Network Architectures and… · p. 3
  • In-band RIS control uses the affected wireless signals, whereas out-of-band control uses a separate wired or wireless interface.The project will determine the appropriate control-channel type or combination for each scenario.Source: C. Network Architectures and… · p. 3
  • The project plans to select suitable RIS architectures and deployment strategies for at least partial implementation in a trial.Source: C. Network Architectures and… · p. 3

III. RESEARCH ON TECHNOLOGY COMPONENTS

RISE-6G develops RIS models and designs that account for discrete surfaces, near-field interactions, and multipath propagation. It combines impedance, statistical, and deterministic methods with electromagnetic characterization for model validation.

A. Modeling, Design, and Characterization

  • RIS modeling must capture mutual coupling between unit cells, near-field transmitter/receiver interactions, and integration with the multipath channel.The models extend continuous metasurface theory to represent tunable discrete structures.Source: A. Modeling, Design, and… · p. 3
  • Impedance models represent discrete-surface scattering and interactions among nearby RISs, while antenna arrays enable end-to-end channel models between port voltages and currents.The hybrid models combine canonical-element antenna theory with full-wave unit-cell simulation and support design and evaluation in ideal free space.Source: A. Modeling, Design, and… · p. 3
  • RISE-6G pairs statistical Random Coupling Models with deterministic RIS-aided propagation tools, extending Dynamical Energy Analysis to include RIS effects on multipath.DEA uses Wigner-function ray densities in phase space; RIS scattering is incorporated through averaging and a Green-function model, with validation through electromagnetic characterization.Source: A. Modeling, Design, and… · p. 3
  • The project will design transmittive and reflective RISs from sub-6 GHz to D-band, using PIN diodes, varactors, or MEMS and fabricating structures with more than 400 elements.Designs will consider space and polarization configurability, with full or discrete phase control depending on the frequency band.Source: A. Modeling, Design, and… · p. 3

B. RIS for Enhanced Connectivity and Reliability

RISE-6G addresses inconsistent RIS research assumptions with accurate, tractable communication models and a framework for evaluating performance. It also investigates connectivity, reliability, and RIS-assisted edge computing.

B. RIS for Enhanced Connectivity and Reliability

  • A wide range of RIS surface, channel, and communication assumptions makes performance limits and system-design conclusions difficult to compare.RISE-6G calls for accurate communication models, control-signaling accounting, and evaluation of essential system features.Source: B. RIS for Enhanced Connectivity and… · p. 3
  • Localization and communication are envisioned as mutually reinforcing in RISE-6G, rather than competing for the same resources.The project seeks deployment strategies for boosted connectivity areas based on communication metrics.Source: Figure 2 · p. 4, B. RIS for Enhanced Connectivity and… · p. 4
  • RISE-6G will develop tractable models that account for surface circuit design and electromagnetic properties, then use them to investigate connectivity, reliability, and performance limits.The project also studies control signaling, channel estimation, RIS settings, resource allocation, and scheduling for RIS support.Source: B. RIS for Enhanced Connectivity and… · p. 4
  • For mobile edge computing, RISE-6G will jointly optimize radio, computation, and RIS resources while keeping delay and accuracy within application-specific QoS limits.Machine learning will support adaptation to mobility and blocking, resource optimization over time, and operational automation and self-healing.Source: B. RIS for Enhanced Connectivity and… · p. 4

C. RIS for Enhanced Localization and Sensing

RISE-6G treats localization and sensing as both services and support for connectivity, localized service delivery, and environmental awareness. It proposes RIS-oriented architectures, control methods, and positioning algorithms to improve localization performance and flexibility.

C. RIS for Enhanced Localization and Sensing

  • Localization and sensing can support location-based services, enhanced connectivity, localized service delivery, and opportunistic environmental and context awareness.RISE-6G views localization and communication as mutually reinforcing rather than competing for resources.Source: C. RIS for Enhanced Localization and… · p. 4
  • The project asks how to place, control, and optimize RISs over time for localization accuracy and coverage, and how to estimate user locations and orientations resiliently and scalably.The desired estimation approach minimizes latency, overhead, and overall consumption while accommodating obstructions and on-demand operation.Source: C. RIS for Enhanced Localization and… · p. 4
  • RISE-6G will develop joint RIS- and system-level architectures and control methods using directional operation, multipath reconfigurability, and model-based and data-driven processing.The project also proposes positioning, tracking, and active and passive detection algorithms that relax synchronization and overhead requirements.Source: C. RIS for Enhanced Localization and… · p. 4
  • RIS-aided localization is intended to provide higher accuracy, service continuity, and flexibility than non-RIS solutions.The project envisions localization-boosted areas where high performance could be guaranteed.Source: C. RIS for Enhanced Localization and… · p. 4

D. RIS for Enhanced Sustainability and Security

RISE-6G proposes RIS-assisted sustainability and security measures that account for non-intended users. It will jointly optimize efficiency metrics and assess the resulting systems with modeling tools and field-oriented measurements.

D. RIS for Enhanced Sustainability and Security

  • Sensing and 3D electromagnetic-field maps will inform network knowledge of non-intended users, with the envisioned RIS detecting people to avoid EMF exposure or eavesdropping.The targeted users include people exposed to EM fields and eavesdroppers.Source: D. RIS for Enhanced Sustainability and… · p. 4
  • RISE-6G will jointly optimize RIS and beamforming for EMFEE and SSE alongside traditional EE, comparing different levels of knowledge about non-intended users.The project distinguishes overt EMF-exposed users, who may cooperate, from covert eavesdroppers, for whom cooperation is not expected; Fig. 3 illustrates these users and boosted areas.Source: D. RIS for Enhanced Sustainability and… · p. 4, Figure 3 · p. 5
  • Signal levels at non-intended users will constrain beamforming and RIS configurations, with centralized and distributed coordination, deep-learning methods, and efficiency trade-off schemes under study.The trade-offs include cases where improving EMFEE or SSE comes at the expense of EE.Source: D. RIS for Enhanced Sustainability and… · p. 5
  • RISE-6G will assess EE, EMFEE, and SSE using physics-based modeling and simulation, with measurements using a commercial 5G base station connected to Telecom Italia’s live network paving the way for in-situ tests.The assessments will include non-intended users across varied propagation environments.Source: D. RIS for Enhanced Sustainability and… · p. 5

IV. RIS-EMPOWERED TRIALS FOR 6G USE CASES

RISE-6G will use public and private field trials to assess RIS-empowered environments for connectivity and localization. At Rennes train station, the envisioned trial addresses coverage, high-bandwidth services, and EMF limits.

IV. RIS-EMPOWERED TRIALS FOR 6G USE CASES

  • The project plans complementary field trials in a public train station and a private smartly connected factory.The trials pursue objectives including overall performance optimization and localization accuracy maximization.Source: §IV · p. 5

A. Use Case 1: Train Station

  • At Rennes station, the envisioned RIS trial targets enhanced connectivity, with central control of RIS equipment and validation of interface density, cost, power, and complexity.The validation measures are considered in relation to desired system performance.Source: A. Use Case 1: Train Station · p. 5, Figure 4 · p. 5
  • Three station use cases are shop coverage optimization, dedicated areas for instant video downloads and cloud gaming, and EMF limits in private areas or for worker protection.Source: A. Use Case 1: Train Station · p. 5
  • The station will test 26 GHz HD video connections and 70 GHz short-range streaming, targeting at least 1.488 Gbps uncompressed 4K HD video transmission.The 70 GHz demonstration uses a compact RIS-based reflector and a 77 GHz radio module.Source: A. Use Case 1: Train Station · p. 5

B. Use Case 2: Connected Factory

The connected-factory trial focuses on kitting logistics, where uncertain component and container positions can lead to AGV mission failures. RIS-assisted communication and localization are planned to support area mapping and positioning.

B. Use Case 2: Connected Factory

  • In kitting, component and container positions may not be known when an AGV receives its mission, potentially causing mission failure and requiring an on-site operator.Kitting brings containers and components together near the assembly line to form kits.Source: B. Use Case 2: Connected Factory · p. 5
  • The envisioned Fig. 5 depicts camera-equipped AGVs, while the planned localization techniques cannot rely on cameras or distributed sensors.Source: Figure 5 · p. 6, B. Use Case 2: Connected Factory · p. 6
  • The project will deliver RIS-based signal-propagation control to complement the wireless network with continuous access-point links to containers/AGVs via sub-6 GHz and 26 GHz, plus cm-level localization demonstrations at 70 and 130 GHz.It also targets minimizing the number of installed RISs needed to cover entire working areas and identifying localization algorithms with resolution/refresh-rate trade-offs.Source: B. Use Case 2: Connected Factory · p. 6

V. CONCLUSIONS

The conclusion presents RISE-6G’s vision and identifies challenges spanning RIS network design, realistic propagation models, dynamic trade-offs, and prototype benchmarking. It proposes two complementary field trials with verticals.

V. CONCLUSIONS

  • RISE-6G identifies four technical challenges: multi-RIS architecture and operation, experimentally validated propagation models and fundamental limits, efficient trade-offs among connectivity, energy, EMFE, and localization under regulations, and benchmarking through two field trials.Source: §V · p. 6
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