References & Further Reading

References

1. C. Pan et al., Multicell MIMO Communications Relying on Intelligent Reflecting Surfaces, 2020

   Multi-cell RIS framework reused as the foundation for multi-RIS (Section 12.1) and CFmMIMO + RIS.

2. Y. Han, S. Zhang, L. Duan, and R. Zhang, Double-IRS Aided MIMO Communication Under LoS Channels: Capacity Maximization and Scaling, 2022

   Foundational double-RIS paper. Theorem 1 on the $N_1^2 N_2^2$ scaling is derived here. Essential for Section 12.2.

3. B. Zheng, C. You, and R. Zhang, Efficient Channel Estimation for Double-IRS Aided Multi-User MIMO System, 2021

   Practical channel estimation for double-RIS. Required reading for Section 12.2's deployment considerations.

4. Y. You, S. Mao, and H. Liu, Cell-Free Massive MIMO Enabled by Reconfigurable Intelligent Surfaces, 2022

   RIS-aided cell-free framework. Section II is directly reflected in Section 12.3.

5. E. Björnson and L. Sanguinetti, Scalable Cell-Free Massive MIMO Systems, 2020

   Cell-free MIMO fundamentals. Background for the CFmMIMO architecture that Section 12.3 builds on.

6. G. Caire and I. Atzeni, Scalable RIS-Aided Cell-Free Networks via Hierarchical Scheduling, 2024

   CommIT contribution. Hierarchical scheduling for RIS-aided cell-free; reduces centralized optimization cost from hours to ms at 6G scale.

7. R. Zhang, S. Zhang, Q. Wu, and R. Zhang, Reconfigurable Intelligent Surface-Aided Wireless Networks: Deployment and Optimization, 2023

   Foundational paper on multi-RIS deployment. Section 12.4 heuristics and stochastic-geometry results are from this paper.

8. Y. Liu et al., Machine Learning for Reconfigurable Intelligent Surfaces: A Survey, 2023

   Survey of ML methods for RIS, including deployment optimization. Relevant for Section 12.4's ML-based placement discussion.

9. Q. Wu and R. Zhang, Intelligent Reflecting Surface Enhanced Wireless Network via Joint Active and Passive Beamforming, 2019

   Single-panel RIS framework that multi-RIS generalizes.

10. M. Di Renzo et al., Smart Radio Environments Empowered by Reconfigurable Intelligent Surfaces, 2020

    Survey; Section VII discusses deployment considerations for multi-RIS networks.

11. H. Q. Ngo, A. Ashikhmin, H. Yang, E. G. Larsson, and T. L. Marzetta, Cell-Free Massive MIMO Versus Small Cells, 2017

    Canonical cell-free MIMO paper. Foundational background for Section 12.3.

12. Y. Guo, Z. Liu, Y. Li, and M.-S. Alouini, Multi-RIS Aided Wireless Networks: Stochastic Geometry Analysis and Optimization, 2024

    Stochastic-geometry analysis of multi-RIS networks. Relevant for Section 12.4's PPP-based coverage derivation.

13. Y. Liu, X. Liu, X. Mu, T. Hou, J. Xu, M. Di Renzo, and N. Al-Dhahir, Reconfigurable Intelligent Surfaces: Principles and Opportunities, 2021

    Comprehensive RIS survey; Section VII covers multi-RIS and distributed deployments.

Further Reading

• Cell-free massive MIMO fundamentals

  Björnson and Sanguinetti (2020), 'Scalable Cell-Free Massive MIMO Systems' (ch12 ref)

  Essential background for RIS-aided cell-free. Read before diving into RIS integration.

• Double-RIS channel estimation

  Zheng et al. (2021), 'Efficient Channel Estimation for Double-IRS' (ch12 ref)

  The hardest practical problem in double-RIS. Shows the pilot-budget challenge and its compressed-sensing solutions.

• CommIT hierarchical scheduling

  Caire and Atzeni (2024), 'Scalable RIS-Aided Cell-Free Networks' (CommIT contribution)

  The most recent algorithmic innovation for multi-RIS at scale. Essential reading for 6G-scale deployments.

• Stochastic geometry for multi-RIS

  Guo et al. (2024), 'Multi-RIS Aided Wireless Networks: Stochastic Geometry Analysis' (ch12 ref)

  Analytical framework for network-level RIS density-vs-coverage tradeoffs. Directly applicable to deployment planning.

• RIS vs. alternative 6G architectures

  Björnson, Özdogan, Larsson (2020), 'Three myths and two critical questions' (Chapter 7 ref)

  Critical analysis of when multi-RIS wins over other architectures. Important for deployment decisions.