References & Further Reading

References

S. Buzzi, G. Caire, and G. Colavolpe, Cell-Free Massive MIMO Meets Low Earth Orbit: Macro-Diversity, Coherent Joint Transmission, and User-Centric Clustering for 6G Non-Terrestrial Networks, 2022
The CommIT contribution that underlies Sections 23.3–23.5. Proposes the user-centric cell-free LEO architecture, derives the coherent-combining SNR gain, quantifies the handover-rate advantage, and gives end-to-end simulation results for a 6G NTN reference scenario. The paper argues that feeder-link load is the practical bottleneck and motivates the move to optical inter-satellite links for in-orbit data distribution.
3GPP, Solutions for NR to Support Non-Terrestrial Networks (NTN), 2021
The normative Release 17 study report on NTN. Defines the reference scenarios, link budgets, channel models, and adaptations to the 5G NR timing, Doppler compensation, and HARQ procedures. Section 6 contains the reference parameters (altitudes, elevation angles, beam footprints) used throughout this chapter. Section 7 discusses the NTN gateway and feeder-link architecture.
3GPP, Study on New Radio (NR) to Support Non-Terrestrial Networks, 2020
The earlier NTN study report preceding TR 38.821. Provides the baseline channel models and Doppler / delay budget calculations referenced in Sections 23.1–23.2. Its Section 6.5 gives the Doppler shift formulas and Section 6.6 the link budget and rain fade model.
O. Kodheli, E. Lagunas, N. Maturo, S. K. Sharma, B. Shankar, J. F. M. Montoya, J. C. M. Duncan, D. Spano, S. Chatzinotas, S. Kisseleff, J. Querol, L. Lei, T. X. Vu, and G. Goussetis, Satellite Communications in the New Space Era: A Survey and Future Challenges, 2021
The definitive contemporary tutorial on satellite communications, covering the orbital classification, link budget, Doppler analysis, and constellation-level design considerations used in Sections 23.1–23.2. The "new space" framing (cheap launches, commodity satellites) is the backdrop against which LEO broadband became economically viable after two decades of false starts.
R. Hadani, S. Rakib, M. Tsatsanis, A. Monk, A. J. Goldsmith, A. F. Molisch, and R. Calderbank, Orthogonal Time Frequency Space Modulation, 2017
The foundational OTFS paper, introducing the delay-Doppler representation and the symplectic Fourier transform that convert a multipath/Doppler channel into a sparse lattice representation. Section 23.4 uses this paper's Theorem <a href="#thm-otfs-advantage" class="ferkans-ref" title="Theorem: OTFS Localizes the LEO Channel to One Delay-Doppler Tap" data-ref-type="theorem"><span class="ferkans-ref-badge">T</span>OTFS Localizes the LEO Channel to One Delay-Doppler Tap</a> to argue that OTFS is a natural fit for the LEO LOS channel.
A. Perez-Neira, M. Caus, R. Vilaseca, M. A. Vazquez, G. Zheng, M. A. Pallares, M. Shankar, and S. Chatzinotas, Non-Terrestrial Networks: An Overview, 2022
A recent survey aimed at standards-engineers rather than researchers. Complements Kodheli et al. by focusing on the 3GPP Release 17 NTN specification process and the open issues that Release 18 and 19 are tackling (IoT NTN, beam hopping, regenerative payloads).
X. Lin, S. Rommer, S. Euler, E. A. Yavuz, and R. S. Karlsson, 5G from Space: An Overview of 3GPP Non-Terrestrial Networks, 2021
A clear, engineer-oriented walkthrough of the 3GPP NTN specification for Release 17. Recommended as the first reference for anyone implementing 5G NR over a satellite link. Discusses the TA extension, the common TA signalling, and the ephemeris broadcast used in Section 23.1's engineering note on Release 17.
L. You, K.-X. Li, J. Wang, X. Gao, X.-G. Xia, and B. Ottersten, Massive MIMO Transmission for LEO Satellite Communications, 2020
The first high-visibility paper establishing that massive MIMO beamforming on-board a single LEO satellite works and provides substantial per-user rate improvements over legacy spot-beam architectures. Analyzes the LEO channel model (Rician LOS plus scatter) and derives ZF/MMSE precoding for the single-satellite downlink. Section 23.2 uses this paper's channel model as its starting point.
W. Wang, A. Liu, Q. Zhang, L. You, X. Gao, and G. Zheng, Robust Multigroup Multicast Beamforming Design for Backhaul-Limited Cloud Radio Access Network, 2022
Extends the LEO massive MIMO framework of You et al. 2020 to multi-user multi-group beamforming with backhaul constraints. Used in Section 23.2 for the narrowband channel vector definition and in Section 23.5 for the feeder-link-limited architecture considerations.
H. Q. Ngo, A. Ashikhmin, H. Yang, E. G. Larsson, and T. L. Marzetta, Cell-Free Massive MIMO Versus Small Cells, 2017
The foundational cell-free massive MIMO paper. Section 23.3 adapts its joint transmission model to the LEO setting, treating each visible satellite as an AP and the feeder network as the fronthaul. The paper's achievable-rate analysis under imperfect CSI carries over with minor modifications once the Doppler pre-compensation is established.
H. Q. Ngo, G. Interdonato, E. G. Larsson, G. Caire, and J. G. Andrews, Ultra-Dense Cell-Free Massive MIMO for 6G: Technical Overview and Open Questions, 2022
Co-authored by G. Caire, this overview cements cell-free massive MIMO as a 6G architectural direction and motivates its use in NTN as a natural application. Provides the broader research context for the Buzzi-Caire-Colavolpe paper referenced throughout Sections 23.3–23.5.
ITU-R, Propagation Data and Prediction Methods Required for the Design of Earth-Space Telecommunication Systems, Recommendation P.618-13, 2017
The canonical ITU model for atmospheric propagation effects on Earth-space links. Provides the rain-fade statistics used in the Section 23.2 engineering note and in the Section 23.3 example on macro-diversity against rain fade. Any NTN link-budget calculation references this recommendation.
T. Wang, J. G. Proakis, E. Masry, and J. R. Zeidler, Performance Degradation of OFDM Systems Due to Doppler Spreading, 2006
A classic analysis of OFDM ICI induced by Doppler. Derives the Dirichlet-kernel leakage expression that Section 23.4 uses to quantify the OFDM ICI floor. Most of the modern LEO waveform literature cites this paper for its rule-of-thumb ICI SIR bound.
Z. Wei, W. Yuan, S. Li, J. Yuan, G. Bharatula, R. Hadani, and L. Hanzo, Orthogonal Time-Frequency Space Modulation: A Promising Next-Generation Waveform, 2021
A comprehensive and accessible tutorial on OTFS at a communications-magazine level. Read after Hadani et al. 2017 for a cleaner presentation of the delay-Doppler representation, the pilot design, and the applications to high-Doppler channels including NTN.
W. Shen, L. Dai, J. An, P. Fan, and R. W. Heath Jr., Channel Estimation for Orthogonal Time Frequency Space (OTFS) Massive MIMO, 2021
The main reference for OTFS channel estimation, which exploits the sparsity of the delay-Doppler response. Section 23.4 relies on this paper's demonstration that the LOS channel has a trivial delay-Doppler estimate (one impulse), justifying the single-tap equalizer claim.
W. Saad, M. Bennis, and M. Chen, A Vision of 6G Wireless Systems: Applications, Trends, Technologies, and Open Research Problems, 2020
An early and influential 6G vision paper that identifies NTN and integrated terrestrial-NTN operation as a first-class pillar of the 6G agenda. Cited in the Section 23.5 historical note.
X. You, C.-X. Wang, J. Huang, et al., Towards 6G Wireless Communication Networks: Vision, Enabling Technologies, and New Paradigm Shifts, 2021
The main Chinese 6G vision paper. Covers NTN, cell-free operation, and integrated sensing as the three dominant architectural shifts expected in 6G, echoing the Buzzi-Caire-Colavolpe framing discussed in Section 23.5.