Source-linked AI summary
Intelligent Reflection Enabling Technologies for Integrated and Green Internet-of-Everything Beyond 5G: Communication, Sensing, and Security
Wei Shi, Wei Xu, Xiaohu You, Chunming Zhao, Kejun Wei
TL;DR
Future IoE must meet ultra-massive communication, sensing, and security requirements with constrained devices and power budgets. This article surveys IRC technologies—RIS and AmBC—and their roles in SAGIN, green communication, sensing, and security. It identifies mutual benefits between IRC and sensing, security applications, and open challenges for deployment and channel acquisition.
Problem
Future IoE must support ultra-massive devices with demanding communication and sensing requirements under limited power and computational resources.
Method
The article provides a tutorial survey of RIS and AmBC applications in SAGIN, green communications, sensing, physical-layer security, and related open challenges.
Results
RIS can enhance links and sensing, while AmBC supports batteryless IoE devices and IRC can improve physical-layer security in unfavorable secrecy environments.
Takeaways & Limitations
RIS and AmBC can be cooperatively integrated with communication and sensing technologies to support future IoE connectivity and energy efficiency.
Abstract
from arXiv · showhide
Internet-of-Everything (IoE) has gradually been recognized as an integral part of future wireless networks. In IoE, there can be an ultra-massive number of smart devices of various types to be served, imposing multi-dimensional requirements on wireless communication, sensing, and security. In this article, we provide a tutorial overview of the promising intelligent reflection communication (IRC) technologies, including reconfigurable intelligent surface (RIS) and ambient backscatter communication (AmBC), to support the requirements of IoE applications beyond the fifth-generation (5G) wireless communication network. Specifically, we elaborate on the benefits of IRC-assisted IoE in the context of the space-air-ground integrated communications and green communications, which are regarded as key features of supporting future IoE application from society and industries. Furthermore, we envision that the IRC-assisted communication and sensing can mutually benefit each other and articulate multiple ways of enhancing the security in IoE by the IRC. Numerical results help illustrate the importance of the IRC in unfavorable secrecy environments. Finally, open research issues and challenges about the IRC-assisted IoE are presented.
I. INTRODUCTION
Future IoE must support ultra-massive connectivity alongside demanding communication and sensing requirements. The article addresses these needs through IRC technologies, especially RIS and AmBC, which reshape propagation or reuse environmental signals with low power consumption.
- Up to 125 billion intelligent devices are projected by 2030, creating stringent requirements for capacity, coverage, latency, reliability, and energy consumption.
- IRC comprises RIS and AmBC technologies that provide supplementary links or transmit information by exploiting environmental signals.
- RIS uses independently controlled passive reflecting elements to realize three-dimensional beamforming, strengthen intended signals, and extend coverage around obstacles or cell edges.
- AmBC modulates and reflects ambient RF signals, enabling batteryless devices and smart sensors with minimal intervention and maintenance costs.
- The article surveys IRC applications across IoE communication, sensing, security, and open challenges, with emphasis on SAGIN and green communications.
II. COMMUNICATION IN IRC-EMPOWERED IOE
IRC-empowered IoE communication is discussed through two complementary contexts: space-air-ground integrated networks and green communications.
- The section examines IRC-empowered IoE communication through space-air-ground integrated networks and green communications.
A. Motivation of SAGIN and Green Communications
SAGIN supports broad future-network coverage, while green IoE communication must sustainably power large numbers of devices across difficult environments. RIS and holographic RIS are presented as tools for adaptive coverage, beam control, and global connectivity.
- SAGIN combines low-, medium-, and high-frequency spectrum resources to pursue seamless global coverage for future wireless networks.
- Replacing batteries across massive IoE deployments is costly, particularly for devices in wilderness, tunnels, underwater locations, and other hard-to-reach environments.
- LEO satellites provide coverage in sparsely populated uninhabited areas but require steerable antennas because of their high velocity.
- RIS can reduce IoE hardware complexity and adapt beam tracking, beam directing, and coverage through configurable reflecting elements.
- Holographic RIS offers higher spatial resolution and compact integration, with envisioned applications in LEO satellites for global connectivity and high-rate IoE communications.
2) Deployment of RISs in Aerial Networks:
RIS deployment on buildings or UAVs can address blocked air-to-ground links in infrastructure-poor areas. Flying RISs add mobility, panoramic coverage, and greater likelihood of line-of-sight connections.
- 2) Deployment of RISs in Aerial Networks:: RISs combined with UAVs improve signal quality for IoE devices facing blocked air-to-ground channels in infrastructure-poor regions.
- 2) Deployment of RISs in Aerial Networks:: Building-mounted RISs can create virtual line-of-sight links between IoE devices and UAVs when direct links are obstructed.
- 2) Deployment of RISs in Aerial Networks:: Flying RISs permit more flexible placement, 360° panoramic coverage, and a higher probability of strong line-of-sight links with IoE devices.
3) Deployment of RISs on Ground Networks:
Ground-network RIS deployments provide supplementary links for blocked or cell-edge IoE devices, while extensions such as spherical RIS can broaden coverage across terrestrial, aerial, and satellite networks.
- 3) Deployment of RISs on Ground Networks:: RISs on outdoor buildings provide supplementary links for urban IoE devices at cell edges or behind obstacles, where signals suffer deep fading.
- 3) Deployment of RISs on Ground Networks:: Spherical RIS extends terrestrial 2D planar arrays into 3D surfaces with higher received signal strength and wider coverage than flat RIS.
- 4) AmBC for SAGIN:: RIS-assisted AmBC systems combine reconfigurable propagation with ambient backscatter communication for future IoE deployments.
- 4) AmBC for SAGIN:: AmBC harvests energy and transmits information through reflected incident RF signals, using WiFi, cellular, UAV, or satellite sources across different SAGIN areas.
1) RIS-Assisted Simultaneous Wireless Information and Power Transfer (SWIPT):
RIS-assisted SWIPT and AirComp address energy and aggregation challenges in low-power IoE systems by strengthening received signals and mitigating channel fading.
- 1) RIS-Assisted Simultaneous Wireless Information and Power Transfer (SWIPT):: SWIPT combines wireless information and power transfer, but its energy receiver requires more power than an information decoder, making receiver efficiency critical.
- 1) RIS-Assisted Simultaneous Wireless Information and Power Transfer (SWIPT):: RIS phase-shift adjustment strengthens signals at the energy receiver, improving SWIPT performance for battery-free IoE systems.
- 2) RIS-Assisted Over-the-Air Computation (AirComp):: RIS-aided AirComp reconstructs harsh channel environments and was reported to significantly reduce mean-squared error in wireless-powered data aggregation.
- 3) AmBC for Green IoE:: AmBC can reduce tiny IoE devices’ energy consumption from milli-watts to micro-watts by avoiding power-consuming active RF components.
3) AmBC for Green IoE:
AmBC supports green IoE by powering and connecting tiny devices with ambient RF signals, while cooperative RIS and AmBC can reduce transmit power and extend coverage.
- 3) AmBC for Green IoE:: RIS and AmBC can be exploited cooperatively to enhance communication in future IoE systems.
- 3) AmBC for Green IoE:: In RIS-assisted AmBC, the combination minimizes transmit-power consumption and increases IoE-device coverage compared with non-RIS-assisted systems.
- A. Enhancing Sensing by IRC for Future IoE: IRC-assisted sensing is motivated by power- and computation-constrained IoE devices that cannot consume extra resources to improve sensing quality.
- A. Enhancing Sensing by IRC for Future IoE: AmBC can power permanent smart sensors, while RIS communication links can function as large sensors for monitoring structural conditions.
- A. Enhancing Sensing by IRC for Future IoE: In smart homes, RISs extend blocked indoor links for camera-free posture recognition, while AmBC-powered devices include temperature and humidity sensors.
B. Enhancing IRC by Sensing for Future IoE
Sensing can enhance IRC-based IoE by improving environmental awareness, channel estimation, and beam alignment, with smart-farm applications linking humidity sensing to automated irrigation.
- B. Enhancing IRC by Sensing for Future IoE: Sensing helps IRC systems understand surrounding environments, improving channel estimation and beam alignment when perfect CSI is unavailable.
- B. Enhancing IRC by Sensing for Future IoE: Detecting blocked line-of-sight links lets the beam point directly toward RISs, reducing unnecessary overhead and latency for beam recovery.
- B. Enhancing IRC by Sensing for Future IoE: In a smart farm, a hygrometer uses reflected RF signals to communicate humidity information to a sprinkler, with AmBC energizing both passive devices.
- B. Enhancing IRC by Sensing for Future IoE: When humidity falls below a threshold, the sprinkler automatically discharges water, and a surveillance camera can report the discharge state.
IV. SECURITY IN IRC-EMPOWERED IOE
IRC can strengthen physical-layer security in IoE by adapting wireless propagation, with flying RISs adding mobility and cooperative jamming options for unfavorable secrecy environments.
- IRC makes physical-layer security more efficient by incorporating dynamic channel environments into the design loop.The article identifies IRC-enhanced PLS as a potential application for IoE systems.
- A. Enhancing PLS in Unfavorable Secrecy Environments: RIS phase shifts can maximize legitimate-user SNR, especially when eavesdroppers have favorable channels.
- A. Enhancing PLS in Unfavorable Secrecy Environments: An RIS-assisted case study considers sixteen elements when the BS–Eve link is shorter than the BS–Bob link.The setup uses average SNRs of −3 dB for BS–Eve and 0 dB for BS–RIS–Eve, with a target secrecy rate of 0.05.
- B. Enhancing PLS with Flying RISs: Flying RISs improve security through flexible 3D positioning, refined beam resolution, and high mobility.
- B. Enhancing PLS with Flying RISs: A flying RIS can act as a mobile cooperative jammer with the ground BS by transmitting artificial noise toward malicious nodes.
- B. Enhancing PLS with Flying RISs: Multiple collaborative flying RISs can cluster legitimate users and coordinate protection when one RIS must fly over eavesdroppers.The passage links this deployment to stronger secure communications in multi-Bob, multi-Eve scenarios.
V. OPEN ISSUES AND CHALLENGES
IRC-assisted IoE remains an active research area with open challenges in flying-RIS joint design and practical channel acquisition.
- The IRC-empowered IoE research area still has unresolved design issues despite substantial prior work.
- A. Joint Design of Flying RIS for SAGIN: Flying RIS design must jointly optimize UAV operation, RIS configuration, and transmission while satisfying endurance, controllability, placement, size, and orientation requirements.RIS orientation can significantly affect air–ground channels.
- B. Dynamic CSI Acquisition: Most IRC applications assume perfect CSI, although passive devices and low-power IoE nodes make channel estimation difficult.Estimation complexity grows with RIS elements, and pilot attacks by eavesdroppers can further degrade CSI acquisition.
C. Deployment of RISs and AmBC
RIS and AmBC deployment remains constrained by difficult RIS placement and AmBC’s limited range, low rates, and interference among many passive devices.
- C. Deployment of RISs and AmBC: RIS deployment is intractable because passive surfaces require joint decisions about physical design, location, collaboration, and association.The article identifies machine learning and stochastic geometry as possible approaches to efficient deployment.
- C. Deployment of RISs and AmBC: AmBC typically spans several to tens of meters at low data rates, creating a need for range extension and interference management.Simultaneous transmissions from many passive devices can produce uncontrollable interference.
- The survey identifies RIS and AmBC as complementary IRC forms whose cooperative use can enhance future IoE communication, sensing, and security.