Eunsun Kim's Research and the Feasibility of Spectrum Sharing Between LEO Satellite Constellations

This article delves into the landscape of research, touching upon Eunsun Kim's contributions and exploring the feasibility of spectrum sharing between large low-earth orbit (LEO) satellite constellations.

Eunsun Kim's Research Contributions

Eunsun Kim received her Ph.D. Her research spans various areas, as evidenced by her publications.

Hepatocellular Carcinoma Research

Kim's work has significantly contributed to the understanding of hepatocellular carcinoma (HCC). Her research explores the molecular mechanisms driving HCC progression.

Hepatocellular carcinoma: old friends and new tricks: This publication provides insights into the complexities of HCC, offering a comprehensive overview of the disease's characteristics and potential therapeutic targets.
Promotion of growth factor signaling as a critical function of β-catenin during HCC progression: This study highlights the role of β-catenin in promoting growth factor signaling, a crucial aspect of HCC development.
Recruitment of Pontin/Reptin by E2f1 amplifies E2f transcriptional response during cancer progression: This research investigates the recruitment of Pontin/Reptin by E2f1, which amplifies the E2f transcriptional response, contributing to cancer progression.
Rb family proteins enforce the homeostasis of quiescent hematopoietic stem cells by repressing Socs3 expression: This study shows how Rb family proteins enforce the homeostasis of quiescent hematopoietic stem cells by repressing Socs3 expression.
E2f coordinates the proliferation and transdifferentiation of a Sox9+bile duct cell to initiate hepatocellular carcinoma: This work shows how E2f coordinates the proliferation and transdifferentiation of a Sox9+bile duct cell to initiate hepatocellular carcinoma.
E2f coordinates the cell cycle and cell fate of hematopoietic progenitors to drive stress myelopoiesis: This work shows how E2f coordinates the cell cycle and cell fate of hematopoietic progenitors to drive stress myelopoiesis.

Spectrum Sharing Between LEO Satellite Constellations

The proliferation of LEO satellite constellations, such as SpaceX's Starlink and Amazon's Project Kuiper, raises important questions about spectrum sharing and potential interference. LEO satellite communication systems circumvent the time-consuming challenges associated with deploying terrestrial infrastructure, which has left many regions and communities severely under-served-or even completely unserved-by terrestrial-based modes of connectivity.

The Challenge of Coexistence

Among other concerns, there are important open questions regarding the coexistence of multiple mega-constellations. In light of active discussions in the regulatory domain and the impending launch of thousands of additional LEO satellites, characterizing downlink interference and investigating the feasibility of the secondary system to reliably protect the primary system becomes crucial.

Analyzing Downlink Interference

To conduct a thorough analysis on the feasibility of two dense LEO satellite communication systems coexisting in-band at 20 GHz, this analysis considers the two preeminent commercial systems mentioned in the introduction: Starlink by SpaceX and Project Kuiper by Amazon. The analysis involves creating a high-fidelity simulation of the two LEO satellite systems using actual orbital parameters, transmit powers, antenna gains, and other system parameters reported in public FCC filings. As such, the analysis considers the case where the two systems are transmitting downlink to nearby ground users at the same time and at the same carrier frequency of 20 GHz. The interference inflicted onto a primary ground user depends on its own receive beam and on the transmit beam of an interfering secondary satellite.

Factors Influencing Interference

Several factors influence the level of interference between LEO satellite systems:

Orbital Parameters: The relative positions of satellites in different constellations impact the potential for interference.
Transmit Powers: Higher transmit powers increase the likelihood of interference.
Antenna Gains: Antenna design and beamforming techniques affect the directionality and strength of signals, influencing interference patterns.

Strategic Satellite Selection

Strategic satellite selection may be used by Kuiper to serve its own ground users while also protecting Starlink ground users. This notion of satellite selection can be extended to the case where Kuiper has limited knowledge of Starlink’s serving satellite.

Simulation and Analysis

Simulations are conducted in multiple cities across the globe, namely Vancouver, Madrid, Seoul, Cape Town, Austin, Rio de Janeiro, and Bangalore. The ITU defines prohibitive interference as when the effective temperature of the receiver increases by more than 6666% when treating interference as noise.

Interference Thresholds and Spectral Efficiency

Interference inflicted onto a primary system by the secondary system may only be tolerated if it is below a certain threshold. The impact of 𝖨𝖭𝖱𝖨𝖭𝖱\mathsf{INR}sansserif_INR on an arbitrary communication link is illustrated.

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Empirical Cumulative Distribution Functions (CDFs)

The empirical cumulative distribution functions (CDFs) of the absolute bounds 𝖨𝖭𝖱max⁢(𝚞)subscript𝖨𝖭𝖱max𝚞\mathsf{INR}{\mathrm{max}}({\mathtt{u}})sansserifINR startPOSTSUBSCRIPT romanmax endPOSTSUBSCRIPT ( typewriteru ) and 𝖨𝖭𝖱min⁢(𝚞)subscript𝖨𝖭𝖱min𝚞\mathsf{INR}{\mathrm{min}}({\mathtt{u}})sansserifINR startPOSTSUBSCRIPT romanmin endPOSTSUBSCRIPT ( typewriteru ) and the conditional bounds 𝖨𝖭𝖱max⁢(𝚞,𝐩⋆)subscript𝖨𝖭𝖱max𝚞superscript𝐩⋆\mathsf{INR}{\mathrm{max}}({\mathtt{u}},{{\mathbf{p}}}^{\star})sansserifINR startPOSTSUBSCRIPT romanmax endPOSTSUBSCRIPT ( typewriteru , boldp startPOSTSUPERSCRIPT ⋆ endPOSTSUPERSCRIPT ) and 𝖨𝖭𝖱min⁢(𝚞,𝐩⋆)subscript𝖨𝖭𝖱min𝚞superscript𝐩⋆\mathsf{INR}{\mathrm{min}}({\mathtt{u}},{{\mathbf{p}}}^{\star})sansserifINR startPOSTSUBSCRIPT romanmin endPOSTSUBSCRIPT ( typewriteru , boldp startPOSTSUPERSCRIPT ⋆ endPOSTSUPERSCRIPT ) across the globe for primary ground users equipped with 32×\times×32 antenna arrays are plotted.

Feasible Secondary Satellites

The empirical CDF (over time) of the number of feasible secondary satellites N𝐬subscript𝑁𝐬N{{\mathbf{s}}}italicN startPOSTSUBSCRIPT bolds endPOSTSUBSCRIPT satisfying the interference protection constraint for various thresholds 𝖨𝖭𝖱thsubscript𝖨𝖭𝖱th\mathsf{INR}{\mathrm{th}}sansserifINR startPOSTSUBSCRIPT romanth endPOSTSUBSCRIPT is analyzed. The CDFs of primary SINR and secondary SINR over time under greedy max-SNR and greedy max-SINR secondary satellite selection 𝐬∞†superscriptsubscript𝐬†{{\mathbf{s}}}{\infty}^{\dagger}bolds startPOSTSUBSCRIPT ∞ endPOSTSUBSCRIPT startPOSTSUPERSCRIPT † endPOSTSUPERSCRIPT and 𝐬∞⋆superscriptsubscript𝐬⋆{{\mathbf{s}}}{\infty}^{\star}bolds startPOSTSUBSCRIPT ∞ endPOSTSUBSCRIPT startPOSTSUPERSCRIPT ⋆ endPOSTSUPERSCRIPT for various ground user antenna array sizes are shown.

SINR and Interference

The interference inflicted onto a primary user served by a satellite 𝐩⋆superscript𝐩⋆{{\mathbf{p}}}^{\star}boldp startPOSTSUPERSCRIPT ⋆ end_POSTSUPERSCRIPT by a secondary satellite which purely maximizes its own SNR or maximizes its own SINR, without protecting the primary user is examined.

Number of Feasible Satellites Under Uncertainty

The empirical CDFs of the number of feasible secondary satellites N𝐬′superscriptsubscript𝑁𝐬′N{{\mathbf{s}}}^{\prime}italicN startPOSTSUBSCRIPT bolds endPOSTSUBSCRIPT startPOSTSUPERSCRIPT ′ endPOSTSUPERSCRIPT capable of satisfying a protection constraint of 𝖨𝖭𝖱th=−12.2subscript𝖨𝖭𝖱th12.2\mathsf{INR}{\mathrm{th}}=-12.2sansserifINR startPOSTSUBSCRIPT romanth endPOSTSUBSCRIPT = - 12.2 dB for all 𝐩⋆∈𝒫′superscript𝐩⋆superscript𝒫′{{\mathbf{p}}}^{\star}\in\mathcal{P}^{\prime}boldp startPOSTSUPERSCRIPT ⋆ endPOSTSUPERSCRIPT ∈ caligraphicP startPOSTSUPERSCRIPT ′ endPOSTSUPERSCRIPT under various levels of uncertainty γ𝛾\gammaitalic_γ are analyzed.

Guaranteed SINR of the Secondary System

The empirical CDFs (over time) of the guaranteed SINR of the secondary system, normalized to its upper bound (SNR), under various levels of uncertainty γ𝛾\gammaitalicγ when 𝖨𝖭𝖱th=−12.2subscript𝖨𝖭𝖱th12.2\mathsf{INR}{\mathrm{th}}=-12.2sansserifINR startPOSTSUBSCRIPT romanth endPOSTSUBSCRIPT = - 12.2 dB are shown.

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Variability in SNR

Across all overhead satellites, there is typically 4444-5555 dB of variability in SNR delivered to a given user.

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