References & Further Reading

References

C. A. Balanis, Antenna Theory: Analysis and Design, Wiley, 4th ed., 2016
The standard graduate-level antenna textbook. Chapters 2 and 12 contain the canonical treatment of the reactive near field, radiating near field (Fresnel region), and far field (Fraunhofer region), including the $d_F = 2 D^2/\lambda$ definition used throughout this chapter.
K. T. Selvan, R. Janaswamy, Fraunhofer and Fresnel Distances: Unified Derivation for Aperture Antennas, 2017
Short pedagogical article that derives the Fraunhofer and Fresnel region boundaries from a unified quadratic-phase analysis. Recommended as the first reading on why $d_F = 2 D^2/\lambda$ and not something else.
M. Cui, L. Dai, Channel Estimation for Extremely Large-Scale MIMO: Far-Field or Near-Field?, 2022
Introduces the polar-domain codebook and develops near-field sparse channel estimation. The main reference for Section 17.3's discussion of chirp bases and polar codebook construction.
E. Björnson, Ö. T. Demir, L. Sanguinetti, A Primer on Near-Field Beamforming for Arrays and Reconfigurable Intelligent Surfaces, 2021
The clearest tutorial on near-field array response vectors and beam focusing, including the depth-of-focus formula used in Theorem <a href="#thm-depth-of-focus" class="ferkans-ref" title="Theorem: Depth of Focus Along the Broadside Ray" data-ref-type="theorem"><span class="ferkans-ref-badge">T</span>Depth of Focus Along the Broadside Ray</a>. Written for wireless engineers familiar with massive MIMO, not antenna specialists.
H. Zhang, N. Shlezinger, F. Guidi, D. Dardari, M. F. Imani, Y. C. Eldar, Beam Focusing for Near-Field Multiuser MIMO Communications, 2022
Extends near-field beam focusing to the multi-user setting with a ZF-style precoder, and analyses the multi-user spatial multiplexing gain that beam focusing enables. Contains the formal multi-user depth-of-focus analysis.
A. Pizzo, T. L. Marzetta, L. Sanguinetti, Spatially-Stationary Model for Holographic MIMO Small-Scale Fading, 2020
The foundational paper on continuous-aperture (holographic) MIMO and the $(A_t A_r)/(\ntn{wl} d)^2$ DoF formula. Establishes that near-field holographic apertures can support DoF greatly exceeding the classical $\min(\ntn{ntx}, \ntn{nrx})$ bound. Used in Section 17.5.
A. Pizzo, L. Sanguinetti, Spatial Characterisation of Electromagnetic Random Channels, 2022
Rigorous extension of the 2020 paper to non-stationary and anisotropic channels. Provides the machinery needed to turn holographic MIMO DoF analysis into a tool for realistic (non-LoS) XL-MIMO settings.
D. Dardari, Communicating with Large Intelligent Surfaces: Fundamental Limits and Models, 2020
Parallel derivation of the near-field DoF of large intelligent surfaces using a continuous-current model. A useful cross-check for the discrete-array Pizzo et al. results, and the standard reference on RIS-aided near-field links.
C. Huang, S. Hu, G. C. Alexandropoulos, A. Zappone, C. Yuen, R. Zhang, M. Di Renzo, M. Debbah, Holographic MIMO Surfaces for 6G Wireless Systems: Opportunities, Challenges, and Trends, 2020
High-level overview of holographic MIMO covering architectural options, RF hardware challenges, and 6G use cases. Useful for placing the physics of this chapter in a system-design context.
A. De Curninge, M. Guillaud, D. Slock, Structured Channel Covariance Estimation from Limited Samples for Large Antenna Arrays, 2019
One of the first formal treatments of spatial non-stationarity in very large arrays. Introduces the notion of position-dependent covariance and motivates sub-array processing. Referenced in Section 17.4.
E. G. Larsson, T. L. Marzetta, H. Q. Ngo, H. Yang, Antenna Count for Massive MIMO: 1.9 GHz versus 60 GHz, 2022
Argues that system-level antenna count scaling at sub-THz cannot be handled with conventional plane-wave + stationary-channel analysis. Provides the practical deployment-architecture context for Section 17.4's sub-array discussion.
Y. Xu, G. Caire, Visibility-Region Aware Channel Estimation for Extremely Large Aperture MIMO, 2023. [Link]
CommIT contribution. Treats visibility regions as a 2-D Markov random field and uses sparse Bayesian inference to jointly estimate visibility and channel coefficients under the spherical-wave model. Cited in Section 17.2 (commit_contribution) and Section 17.4. The algorithmic companion to the physics developed here; the full treatment is in Chapter 18.
3GPP, Study on Channel Model for Frequencies from 0.5 to 100 GHz (TR 38.901 v18.0.0), 2023
The current standard channel model for 5G and the baseline for 6G study items. Based on plane-wave propagation and spatial stationarity; Section 7.6.3 flags spatial consistency concerns that are being re-examined in Rel-19 XL-MIMO work.
M. Born, E. Wolf, Principles of Optics, Cambridge University Press, 7th ed., 1999
The classical optics reference. Chapter 8 derives Fresnel diffraction and depth of focus for lens-based imaging; the RF near-field depth-of-focus formula is the same result transported to the antenna array setting. Recommended for the historical perspective of Section 17.3.