https://corelab.ku.edu.tr/

Wireless Communications withReconfigurable Intelligent Surfaces

September 2020

Dr. Ertugrul BasarAssociate Professor, Department of Electrical and Electronics EngineeringKoç University, Turkey

Director, CoreLabYoung Member, Turkish Academy of SciencesSenior Member, IEEE & IEEE ComSocSenior Editor, IEEE Communications LettersEditor, IEEE Transcactions on CommunicationsEditor, Physical Communication (Elsevier)Editor, Frontiers in Communications and Networks

Outline

A Perspective on Beyond 5G and 6G

Reconfigurable Intelligent Surfaces: A New Frontier in Wireless

State-of-the-Art in Intelligent Communication Environments

Potential Applications of Intelligent Surfaces towards 6G

Future Directions & Conclusions

2

The Era of 5G

3GPP 5G Standalone Release (June 2018) Release 16: July 2020. 5G PHY Layer: Above 6 GHz, massive MIMO, multiple OFDM

numerologies.

One thing has become certain during standardization of 5G:There is no single enabling technology that can achieve all the applications being promised by 5G networking.

The necessity of more flexible, new spectrum- and energy-efficient physical layertechniques for beyond 5G wireless networks.

3First 5G NR Specs Approved. http://www.3gpp.org/news-events/3gpp-news/1929-nsa nr 5g

A Vision for 6G Wireless (2030 and Beyond)

4

W. Saad, M. Bennis, ‘’A Vision of 6G Wireless Systems: Applications, Trends, Technologies, and Open Research Problems’’, IEEE Netw., July 2019.

Requirements of 6G

5

‘’The Vision of 6G,’’ Samsung Research, 14 July 2020. https://news.samsung.com/global/samsungs-6g-white-paper-lays-out-the-companys-vision-for-the-next-generation-of-communications-technology

Main Problems in Wireless and Modern PHY Solutions

What is currently slowing down wireless network operators from building truly pervasive wireless networks that can provide uninterrupted connectivity and high quality-of-service (QoS) to multiple users and devices in harsh environments.

Main problems: Deep fading, severe attenuation, inter-symbol/user interference,

Doppler effect, evasdropping, blocked line-of-sight random channel

Existing modern physical layer solutions are not enough and the overall progress is still relatively slow! Adaptive modulation and coding, multi-carrier modulation, non-

orthogonal multiple access, relaying, dynamic spectrumallocation, beamforming, and reconfigurable antennas

New and radical solutions are required in the physical layer !

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Radical PHY Solutions for Beyond 5G

A growing interest in novel communication paradigms that exploitthe implicit randomness of the propagation environment.

Two design targets: Simplifying the transceiver architecture and/or Increasing the quality-of-service (QoS).

Two emerging PHY solutions for beyond 5G/6G Index modulation (IM) technologies Smart radio environments with reconfigurable intelligent surfaces

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What is Index Modulation?

IM is a novel transmission technique utilizes the indices of the building blocks of corresponding communication systems to convey information.

Building blocks: transmit antennas, subcarriers, antenna patterns, time slots, transmit LEDs, relays, modulation types, spreadingcodes, dispersion matrices, loads etc.

IM techniques consider innovative ways to convey information compared totraditional communication systems of the past 50 years offer attractive advantages in terms of spectrum efficiency, energy efficiency, and hardware simplicity

There has been a tremendous interest in IM schemes over the past few years.

8

E. Basar, ‘’Index modulation techniques for 5G wireless networks’’, IEEE Commun. Mag., 2016.E. Basar et al., ‘’Index modulation techniques for next-generation wireless networks", IEEE Access, 2017.

Spatial Modulation A New MIMO Mode

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R. Mesleh et al., ‘’Spatial modulation’’, IEEE Trans. Veh. Technol., 2008. ~2000 citations!Di Renzo et al., ‘’Spatial modulation for generalized MIMO: Challenges, opportunities, and implementation’’, Proc. IEEE, 2014.

Single RF chain!

OFDM with IM A New Waveform

10E. Basar et al., ‘’Orthogonal frequency division multiplexing with index modulation’’, IEEE Trans. SignalProcess., 2013. A new line of research in waveform design ~600 citations!

Divide and conquerwith subblocks!

MBM A New Virtual MIMO Solution

Media-based modulation (MBM), which can be implemented by reconfigurable antennas, offers a completely new dimension for the transmission of digital information the realizations of wireless channels themselves.

11

A. K. Khandani, ‘’Media-based modulation: A new approach to wireless transmission’’, ISIT 2013.E. Basar, ‘’Media-Based Modulation for Future Wireless Systems: A Tutorial’’, IEEE Wireless Commun., Nov. 2019.

Again single RF chain but indexing through antenna patterns!

Wireless 2.0: Intelligent Radio Environments

The propagation medium a randomly behaving entity between the Tx and the Rx degrading the quality of the received signal uncontrollable interactions of the transmitted radio waves with the surrounding objects.

Reconfigurable intelligent surfaces (RISs) man-made surfaces of electromagnetic (EM) material electronically controlled with integrated electronics have unique wireless communication capabilities.

Can the operators customize the propagation of the radio waves in the environment via software in order to increase the QoS without increasing the power consumption? smart radio environments a step beyond software networks!

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Reconfigurable Intelligent Surfaces (RISs)

RIS smart device that control the propagation environment with the aim of improving the coverage and signal quality.

The large number of small, low-cost, and passive elements on a RIS simply modify the incident signal.

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Re-engineering the electromagnetic waves…E. Basar et al., “Wireless Communications Through Reconfigurable Intelligent Surfaces’’, IEEE Access, Sep. 2019.Di Renzo et al., ‘’ Smart Radio Environments Empowered by Reconfigurable Intelligent Surfaces: How it Works, State of Research, and Road Ahead’’, arXiv:2004.09352, Apr. 2020.

PIN diodes, varactorsMEMS switches

Emerging Applications and Use-Cases

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Can we cover all walls with RISs? How feasible? How costly? How effective? An interesting optimization problem

Unique Features of RISs

The RIS concept is completely different from existing (massive) MIMO, beamforming, amplify-and-forward relaying, and backscatter communication paradigms.

The large number of small and low-cost elements on an RIS only reflect the incident signal with an adjustable phase shift or enable other unnatural EM functionalities.

Does not require a dedicated energy source for RF processing, decoding, encoding, or retransmission has a (nearly) passive nature

Not affected by receiver noise since they do not need ADCs, DACs, power amplifiers, mixers, filters no noise amplification

15E. Basar et al., ‘’Wireless Communications Through Reconfigurable Intelligent Surfaces’’, IEEE Access, Sep. 2019.

RISs vs Relaying

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Relaying Reconfigurable Intelligent Surfaces

FunctionActively processes the signal by

generating, amplifying, and retransmittingit, inherently half-duplex

No complex processing, encoding, decoding

Passively reflects the incident signal without any RF processing, full-duplex

Hardware Complexity

A dedicated power source and RF equipment are needed for operation

No dedicated power amplifiers, mixers,filters and DACs/ADCs

Cost Active RF source increases the cost considerably

Small and low-cost elements are suitable for nearly passive implementation

NoiseImpact

Noise is amplified in AF relayingNoise is mitigated but complexity and

power consumption increase in DF relaying, potential error propagation

Not affected by receiver noise since they do not need ADCs, DACs, and power

amplifiers, no error propagation

RISs vs Passive Reflectarrays

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Supports unique EM functionalities

RIS as an Active Reflectarray

Supports only normal reflection!

RISs vs Backscatter Communication

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RIS provides the control of wireless channels, the RIS itselfmight not be an information source

BackCom uses ambient RF signals to encode its information

Both are passive! Can we say they are close relatives?

S. Gong et al., ‘’Towards Smart Wireless Communications via Intelligent Reflecting Surfaces: A Contemporary Survey’’, IEEE Commun. Tuts. & Tuts., June 2020.

Ground Reflection vs Free-Space Propagation

With ground reflection:

Without ground reflection:

With intelligent reflection:

E. Basar et al., ‘’Wireless Communications Through Reconfigurable Intelligent Surfaces’’, IEEE Access, Sep. 2019.19

Controlling the Multipath Through RISs

For the case of slowly varying and flat fading channels, the received baseband signal reflected through the RIS with 𝑁𝑁 passive elements:

Our task is to maximize the received SNR by adjusting RIS phases (𝜙𝜙𝑖𝑖):

20E. Basar, “Transmission through large intelligent surfaces: A new frontier in wireless communications”, EuCNC 2019, online: Feb. 2019, published: June 2019.

Dyadic Backscatter Channel Model:

Theoretical Bit Error Probability

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Withoutpath loss!

We need channel phases knowledge at the RIS Not easy but feasible!

Increasing the Number of Reflectors

Doubling 𝑵𝑵 provides ~6 dB improvement(four-fold decrease) in the required SNR

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ThereceivedSNR is a

function of N2

Origins of Intelligent Surfaces

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L. Subrt and P. Pechac, “Controlling propagation environments using intelligent walls,” EuCAP 2012.N. Kaina et al., “Shaping complex microwave fields in reverberating media with binary tunable metasurfaces,” Sci. Rep.,2014.T. J. Cui et al., “Coding metamaterials, digital metamaterials and programmable metamaterials,” Light: Sci. & App.,2014.H. Yang et al., “A programmable metasurface with dynamic polarization, scattering and focusing control,” Sci. Rep. 2016.J. Jornet et al., “Increasing indoor spectrum sharing capacity using smart reflect-array,” ICC 2016.S. Hu et al., “The potential of using large antenna arrays on intelligent surfaces,” VTC-Spring 2017.C. Liaskos et al., “A new wireless communication paradigm through software-controlled metasurfaces”, IEEE Commun. Mag., 2018.

State-of-the Art Schemes

In the past year, several studies and innovative solutions related to RISs have been done.

Different terms to denote the RISs: reconfigurable intelligent surfaces, large intelligent surfaces, smart reflect-arrays, intelligent reflecting surfaces, passive intelligent mirrors, hypersurfaces, programmable metasurfaces, and so on.

Researchers focused on: theoretical SNR, outage, and error probability derivations channel estimation problems and effective protocols signal-to-interference-ratio (SINR) maximization joint active and passive beamforming optimization problems practical implementations (harware) and testing physical layer security solutions, cognitive radio applications the potential of intelligent surfaces for application to mmWave/THz,

free space optical, IM, OFDM, UAV, NOMA, and VLC systems artificial intelligence solutions (deep learning)

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Our Active Research on RISs @ CoreLab

Channel Modeling for Indoors and Outdoors Novel MIMO System Designs and IM-Based Systems NOMA-Based Solutions for Multi-User Systems Applications for Vehicular and UAV Networks Solutions for COVID-19 (RISs and backscatter communications)?

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E. Basar, I. Yildirim, ’’Indoor and Outdoor Physical Channel Modeling and Efficient Positioning for Reconfigurable Intelligent Surfaces in mmWave Bands’’, arXiv:2006.02240, May. 2020.E. Basar, ‘’Reconfigurable Intelligent Surface-Based Index Modulation: A New Beyond MIMO Paradigm for 6G’’, IEEE Trans. Commun., May 2020.Z. Yigit, E. Basar, I. Altunbas, ‘’Low Complexity Adaptation for Reconfigurable Intelligent Surface-Based MIMO Systems‘’, IEEE Commun. Lett. (to appear), Aug. 2020.I. Yildirim, A. Uyrus, E. Basar, ‘’Modeling and Analysis of Reconfigurable Intelligent Surfaces for Indoor and Outdoor Applications in Future Wireless Networks’’, arXiv:1912.07350, Dec. 2019.J. Zuo, Y. Liu, E. Basar, O. A. Dobre, ‘’ Intelligent Reflecting Surface Enhanced Millimeter-Wave NOMA Systems‘’, IEEE Commun. Lett., June 2020.A. Khaleel, E. Basar, ‘’Reconfigurable Intelligent Surface-Assisted MIMO Communications’’, IEEE Systems J. (toappear), July 2020.A. Canbilen, E. Basar, S. Ikki, ‘’Reconfigurable Intelligent Surface-Assisted Space Shift Keying’’, IEEE Wireless Commun. Lett. , Apr. 2020.E. Basar, ‘’Reconfigurable Intelligent Surfaces for Doppler Effect and Multipath Fading Mitigation’’, arXiv:1912.04080, Nov. 2019.

Unified narrowband channel model for RIS-assisted systems in indoor and outdoor environments for the first time

Considers the 5G mmWave (3D) channel model with randomnumber of clusters/scatterers

Includes many physical characteristics : LOS probability (modifiedwrt RIS height), shadowing effects, shared clusters, realistic gains and array responses

E. Basar, I. Yildirim, ’’Indoor and Outdoor Physical Channel Modeling and Efficient Positioning for Reconfigurable Intelligent Surfaces in mmWave Bands’’, arXiv:2006.02240, May. 2020.

Physical Channel Modeling for mmWaveCommunication Systems

Indoors

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Useful insights from the perspective of potential RIS use-cases and their efficient positioning.

Guidelines towards the effective use of RISs

Physical Channel Modeling mmWaveCommunication Systems – cont’d

Outdoors

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SimRIS Channel Simulator: An accurate, open-source, and widely applicable RIS channel model for mmWave frequencies.

Channel modeling of RIS-assisted systems with tunable operating frequency, terminal locations, number of RIS elements, and environments.

Environments: InH Indoor Office and UMi Street Canyon

Frequencies: 28 GHz and 73 GHz.Graphical user interface (GUI) of the SimRIS Channel Simulator

E. Basar, I. Yildirim, ’’SimRIS Channel Simulator for Reconfigurable Intelligent Surface-Empowered Communication Systems’’, arXiv:2006.00468, May 2020.Codes available at https://corelab.ku.edu.tr/tools/SimRIS

SimRIS Channel Simulator v1.0 (May 2020)

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The closer to the RIS the better!LOS paths are decisive!

Indoor Physical Channel Modeling: Achievable Rate Analysis

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Indoors(top view)

SimRIS v2.0 (just released – August 2020)

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MIMO extensionPlanar and linear array types

Adjustable Tx/Rx/RIS locationsAdjustable number of Tx/Rx antennas

https://corelab.ku.edu.tr/tools/SimRIS/

E. Basar, I. Yildirim, ‘’SimRIS Channel Simulator for Reconfigurable Intelligent Surfaces in Future Wireless Networks’’, arXiv:2008.01448, August. 2020

Simulations with SimRIS v2.0

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Useful guidelines for practical implementation of RISs

Practical Issues: Path Loss for RISs

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When, if ever, is it is appropriate to interpret far case RIS scattering as specular reflection? The short answer is “never”

Specular reflectionpath loss:

S.W. Ellingson, “Path Loss in Reconfigurable Intelligent Surface-Enabled Channels”, arXiv:1912.06759, Dec. 2019.

Fortunately N2 appears in path gainWe need compact RIS design

Towards Practical Channel Modeling

33E. Basar, I. Yildirim, ’’SimRIS Channel Simulator for Reconfigurable Intelligent Surface-Empowered Communication Systems’’, arXiv:2006.00468, May. 2020.

Adjustable Phase!

Careful RIS positioning is needed scattering is not merciful

Emerging Applications of RISs

Multi-User MIMO and

NOMA

Physical LayerSecurity

RIS as an Access Point

Doppler andMultipathMitigation

Deep Learning Localizationand Sensing

Vehicular/UAV Networks

OFDM, FSO, VLC, IM, CR

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App. 1: RIS-Based Multi-User Systems

35

C. Huang et al., “Reconfigurable intelligent surfaces for energy efficiency in wireless communication”, IEEE Trans. Wireless Commun., online: Oct. 2018, published: Aug. 2019.Q. Wu, R. Zhang, “Intelligent Reflecting Surface Enhanced Wireless Network via Joint Active and Passive Beamforming”, IEEE Trans. Wireless Commun., online: Sep. 2018, published: Nov. 2019.

Might be an effective solution when BS-User link is not strong enough

App. 2: RIS as a Simple Transmitter

The RIS plays the role of an access point virtual PSK

A nearby RF signal generator transmits an unmodulated carrier signal towards the RIS a very simple transmitter architecture! no power amplifiers, no mixers, no filters

36

E. Basar, “Transmission through large intelligent surfaces: A new frontier in wireless communications,” EuCNC 2019, online: Feb. 2019, published: June 2019.W. Tang et al., “Programmable metasurface-based RF chain-free 8PSK wireless transmitter“, Electron. Lett., Apr. 2019.

App. 3: Index Modulation

RIS meets spatial modulation at both Rx and Tx sides a massive MIMO alternative?

37

E. Basar, ‘’Reconfigurable Intelligent Surface-Based Index Modulation: A New Beyond MIMO Paradigm for 6G’’, IEEE Trans. Commun., online: Apr. 2019, published: May 2020.A. Canbilen, E. Basar, S. Ikki, ‘’Reconfigurable Intelligent Surface-Assisted Space Shift Keying’’, IEEE Wireless Commun. Lett., Apr. 2020.

App. 4: RIS-Based Virtual MISO/MIMO

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A. Khaleel, E. Basar, ‘’ Reconfigurable Intelligent Surface-Empowered MIMO Systems’’, IEEE Systems J. (to appear), July 2020.W. Tang et al., ‘’MIMO Transmission through Reconfigurable Intelligent Surface: System Design, Analysis, and Implementation’’, IEEE J. Sel. Areas Commun., July 2020.

MimicingMIMO

Do we needcostly RF

chains anymore?

App. 5: Physical Layer Security

39

R. Zhang et al., ‘’Secure Wireless Communication via Intelligent Reflecting Surface’’, IEEE Wireless Commun. Lett., May. 2019.R. Schober et al., ‘’Enabling Secure Wireless Communications via Intelligent Reflecting Surfaces’’, GLOBECOM 2019.

Another dimension for PHY security (an important missing feature in 5G)

App. 6: Vehicular Networks

40

R. Schober et al., ‘’Physical Layer Security in Vehicular Networks with Reconfigurable Intelligent Surfaces’’, arXiv:1912.12183, Dec. 2019.B. Massini et al., ‘’The Use of Meta-Surfaces in Vehicular Networks’’, J. Sens. Actuator Netw., Mar. 2019.

- Enhance security- Overcome LOS blockages- Sensing, pedestrian dedection

App. 7: NOMA

41

M. Fu et al., ‘’Intelligent Reflecting Surface for Downlink Non-Orthogonal Multiple Access Networks’’, GLOBECOM 2019, Dec. 2019.Z. Ding and H. V. Poor, ‘’Simple Design of IRS-NOMA Transmission’’, IEEE Commun. Lett., May 2020.J. Zuo, Y. Liu, E. Basar, O. A. Dobre, ‘’Intelligent Reflecting Surface Enhanced Millimeter-Wave NOMA Systems‘’, IEEE Commun. Lett., June 2020.

- Reduce interference- Increase capacity

Effective NOMA 2.0

App. 8: Low-Complexity MIMO

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No convexoptimization!

Z. Yigit, E. Basar, I. Altunbas, ‘’Low Complexity Adaptation for Reconfigurable Intelligent Surface-Based MIMO Systems‘’, IEEE Commun. Lett. (to appear), Aug. 2020.L. Hanzo et al., ‘’MIMO Assisted Networks Relying on Large Intelligent Surfaces: A Stochastic Geometry Model’’, arXiv:1910.00959, Oct. 2019.

App. 9: Non-Terrestrial Networks

43

M. Bennis et al., ‘’Reflections in the Sky: Millimeter Wave Communication with UAV-Carried Intelligent Reflectors’’, arXiv:1908.03271, Aug. 2019.S. Alfattani et al., ‘’ Aerial Platforms with Reconfigurable Smart Surfaces for 5G and Beyond’’, arXiv:2006.09328, June 2020.

- Overcome LOS blockages- Support terrestrial networks- Support aerial users- Backhauling support

How practical?

RIS at theground or air?

App. 10: Cognitive Radio

44E. Larsson et al., ‘’ Intelligent Reflecting Surface-Assisted Cognitive Radio System’’, arXiv:1912.10678, Dec. 2019.

Improves therate of the SU-Rx

considerably

App. 11: Doppler Mitigation

45

E. Basar, ‘’Reconfigurable Intelligent Surfaces for Doppler Effect and Multipath Fading Mitigation’’, arXiv:1912.04080, Nov. 2019.

with an RIS

time-invariantchannel

App. 11: Doppler Mitigation – cont’d

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N = 0 and M = 10 (10 plain IOs without any RISs)

N = 10 and M = 0 (10 RISs without any plain IOs)

How practical?

We are workingon it!

App. 12: Coverage Extension towards 6G

47

I. Yildirim, A. Uyrus, E. Basar, ‘’ Modeling and Analysis of Reconfigurable Intelligent Surfaces for Indoor and Outdoor Applications in Future Wireless Networks’’, arXiv:1912.07350, Dec. 2019.

- Extend the coverage with multiple RISs- Optimum RIS selection and positioning

App. 13: OFDM Systems

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R. Zhang et al., ‘’ Intelligent Reflecting Surface Meets OFDM: Protocol Design and Rate Maximization’’, arXiv:1906.09956, June 2019.

Can I use RISswith Wi-Fi?

App. 14: Posture Recognition

49

H. V. Poor et al., ‘’ Reconfigurable Intelligent Surfaces based RF Sensing: Design, Optimization, and Implementation’’, arXiv:1912.09198, Dec. 2019.

App. 15: Radio Localization

50

H. Wymeersch et al., ‘’Radio Localization and Mapping with Reconfigurable Intelligent Surfaces’’, arXiv:1912.09401, Dec. 2019.

A very interestingapplication beyond

communications

Wrapping Up the Applications – Sep. 2020

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RIS

Q. Wu et al., ‘’Intelligent Reflecting Surface Aided Wireless Communications: A Tutorial’’, arXiv:2007.02759, July 2020.E. Basar, I. Yildirim, ‘’SimRIS Channel Simulator for Reconfigurable Intelligent Surfaces in Future Wireless Networks’’, arXiv:2008.01448, Aug. 2020

Recent Interesting Studies

Near-field issues & Correlation matrices

52

E. Björnson, L. Sanguinetti, ‘’Power Scaling Laws and Near-Field Behaviors of Massive MIMO and Intelligent Reflecting Surfaces’’, IEEE Open J. Commun. Society, Aug. 2020.E. Björnson, L. Sanguinetti, ‘’Rayleigh Fading Modeling and Channel Hardening for Reconfigurable Intelligent Surfaces’’, arXiv:2009.04723, Sep. 2020.

Recent Interesting Studies – cont’d

RIS with active elements/relays

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G. C. Alexandropoulos and E. Vlachos, ‘’ A Hardware Architecture for Reconfigurable Intelligent Surfaces with Minimal Active Elements for Explicit Channel Estimation’’, arXiv:2002.10371, Feb. 2020.Z. Wan et al., ‘’Terahertz Massive MIMO with Holographic Reconfigurable Intelligent Surfaces’’, arXiv:2009.10963, Sep. 2020.A. Alkhateeb et al., ‘’ Relay Aided Intelligent Reconfigurable Surfaces: Achieving the Potential Without So Many Antennas’’, arXiv:2006.06644, June 2020.

Intelligent Metasurface: How it Works?

54

Tretyakov et al., “Intelligent Metasurfaces with Continuously Tunable Local Surface Impedance for Multiple Reconfigurable Functions”, Phys. Rev. Applied, Apr. 2019

HyperSurface @ VisorSurf

55

C. Liaskos et al., ‘’A new wireless communication paradigm through software-controlled metasurfaces’’, IEEE Commun. Mag., Sep. 2018.

Their prototype is ready after 3 years of R&D

Recent Practical Campaign

56

W. Tang et al., “Wireless Communications with Reconfigurable Intelligent Surface: Path Loss Modeling andExperimental Measurement”, arXiv:1911.05326, Nov. 2019.

One of themost

sophisticatedRIS designs

so far!

Recent Practical Campaign – cont’d

57

L. Dai et al., “Reconfigurable Intelligent Surface-Based Wireless Communication: Antenna Design, Prototyping andExperimental Results”, arXiv:1912.03620, Dec. 2019.

21.7 dBi antenna gain@ 2.3 GHz

Recent Practical Campaign – cont’d

58

M. Dunna et al., “ScatterMIMO: Enabling Virtual MIMO with Smart Surfaces”, MobiCom’20, Sep. 2020. https://wcsng.ucsd.edu/scattermimo/

ScatterMIMO creating virtual AP forMIMO streams

IEEE 802.11ac (100 MHz @5 GHz)

48 patch antenna elementsat 3 tiles

Less than 14 mW powerconsumption

Indoor coverage: 30m 45m

Our Intelligent Reflectarray Prototype - 2020

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Better than nothing!First tests are ongoing @ CoreLab using Adalm-Pluto SDRs

Recent Interest from Industry

NTT DOCOMO Pivotal Commware Metawave Greenerwave

A working group on RIS @ IMT-203060

Open Research Issues towards 6G

Determination of convincing use-cases in which the RISs might have a huge potential to boost the communication QoS.

Assessment of practical protocols for reconfigurability of RISs Practical path-loss/channel modeling and real-time testing of

large-scale RISs in different propagating environments

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Bridging the gap betweentheoretical analysis and real-world deployments

Open Research Issues towards 6G – cont’d

Determination of fundamental performance limits of RIS-assisted networks

Robust optimization & resource allocation issues (space/time/freq.) Optimal placement of RISs and optimization of the overall network Development of EM-based RIS models and hardware effects Exploration of effective mmWave and THz communication systems

with RISs Exploration of the potential of RISs for beyond communication

(sensing, radar, localization etc.)

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Open Research Issues towards 6G – cont’d

AI-driven tools for designing/optimizing/reconfiguring surfaces Deployment of multiple RISs and their coordination/optimization Exploration of futuristic scenarios (very high number of devices,

eMBB + URRLC, very high mobility)

Standardization and integration into existing wireless commu-nication networks (5G, 6G, IoT, IEEE 802.11x) joint effort of academia and industry is required

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Conclusions

Perfect time to do research on 6G. We need out-of-the-box PHY solutions!

Two possible uses to exploit RISs in the first place:i) shaping the radio waves in order to control, in a deterministic fashion, the multipath propagationii) realizing low-complexity and energy efficient transmitters that require only one RF chain.

Interesting potential use-cases & open research problems for RISs Is it the secret remedy we are looking for 6G?

Effective collaboration of academia and industry: Potential new scientific proposals/studies Potential new patents towards 6G Potential standardization activities

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Our New ETI on RISs @ IEEE ComSoc

Up and running

Please follow the website of this ETI for its future activities: https://www.comsoc.org/about/committees/emerging-technologies-initiatives/reconfigurable-intelligent-surfacesMailing-list: etiris@comsoc.orgSubscription: Please send an email to LISTSERV@comsoc-listserv.ieee.org with the following command in the BODY of the message: JOIN ETIRIS

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Our New Special Issue @ IEEE OJ-COMS

https://www.comsoc.org/publications/journals/ieee-ojcoms/cfp/reconfigurable-intelligent-surface-based-communications-6g

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Our Feature Topic at IEEE COMMAG

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https://www.comsoc.org/publications/magazines/ieee-communications-magazine/cfp/reconfigurable-intelligent-surfaces-design

Our Feature Topic at Frontiers

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https://www.frontiersin.org/research-topics/16017/wireless-communications-with-reconfigurable-intelligent-surfaces-fundamentals-experimentation-and-ap

StrongEDITORIAL BOARD

2020LAUNCH

Best Readings on RIS

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https://www.comsoc.org/publications/best-readings/reconfigurable-intelligent-surfaces

Our New Book @ IET

Beyond 5G and 6G Waveform design and OFDM,

alternative and hybrid waveforms

Index modulation Massive MIMO,

beamforming, spatial modulation

Reconfigurable intelligent surfaces

Channel modeling, mmWaveand THz communications, visible light communications

Coordinated networks Non-orthogonal radio access

and NOMA Cognitive radio, deep

learning towards 6G, and physical layer security

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https://shop.theiet.org/flexible-and-cognitive-radio-access-technologies-for-5g-and-beyond

THANK YOU!

for further questions: ebasar@ku.edu.tr

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