Efficient Spectrum Sharing in Upper Mid-Band with Interference Nulling

Core Concepts

The author explores interference dynamics in terrestrial-satellite coexistence scenarios and introduces a novel beamforming approach to mitigate interference, ensuring protection of satellite uplink communications while maintaining terrestrial downlink quality.

Abstract

The content delves into the challenges of expanding cellular services in the upper mid-band and the integration issues with incumbent satellite services. It proposes a beamforming technique leveraging ephemeris data for interference mitigation, demonstrating efficient spectrum sharing benefits.
The study analyzes the relationship between satellite elevation angles and path loss, highlighting the impact of BS antenna element gain on interference. The proposed interference nulling method aims to address these challenges by creating spatial radiation nulls towards visible satellites.
Through system-level simulations involving Starlink LEO satellites over rural Colorado, the study evaluates different beamforming approaches. It concludes that LOS interference nulling effectively prevents degradation of satellite uplink while maintaining terrestrial downlink performance.

Stats

The upper mid-band ranges from 7–24 GHz.
Starlink has deployed approximately 4700 LEO satellites.
The proposed approach maintains satellite uplink SNR degradation under 0.1 dB.
Terrestrial downlink SNR penalty is only negligible.
FCC released a proposed rulemaking notice (NPRM) for spectrum sharing of the 12 GHz band with 5G systems.

Quotes

"The upper mid-band has attracted considerable interest to expand cellular services."
"Starlink plans to expand its LEO satellites to over 25000."
"Our approach ensures protection of satellite uplink communications without compromising terrestrial downlink quality."

Key Insights Distilled From

Terrestrial-Satellite Spectrum Sharing in the Upper Mid-Band with Interference Nulling

by Seongjoon Ka... at arxiv.org 03-08-2024

https://arxiv.org/pdf/2311.12965.pdf

Deeper Inquiries

How can multi-user MIMO transmissions impact spectrum sharing in the upper mid-band

Multi-user MIMO (Multiple Input Multiple Output) transmissions can significantly impact spectrum sharing in the upper mid-band by enabling more efficient use of the available frequency resources. With multi-user MIMO, multiple users can be served simultaneously using the same time-frequency resource, thereby increasing spectral efficiency. In the context of spectrum sharing between terrestrial networks and LEO satellites, multi-user MIMO can help mitigate interference issues by spatially multiplexing different users and directing beams towards specific users or away from interfering entities.
By employing multi-user MIMO techniques in the upper mid-band, operators can enhance network capacity and improve overall system performance. The ability to serve multiple users concurrently while managing interference effectively is crucial for optimizing spectrum utilization in shared frequency bands. Additionally, advanced signal processing algorithms in multi-user MIMO systems enable better interference management and increased data rates for all users involved.

What are potential drawbacks or limitations of implementing LOS interference nulling

While LOS (Line-of-Sight) interference nulling presents a promising approach to mitigating interference between terrestrial networks and LEO satellites, there are potential drawbacks and limitations associated with its implementation:

Complexity: Implementing LOS interference nulling requires real-time tracking of satellite positions using ephemeris data. This process adds complexity to base station operations as it involves continuously updating beamforming vectors based on changing satellite locations.

Limited Coverage: LOS nulling primarily addresses direct line-of-sight paths between base stations and satellites, neglecting potential non-line-of-sight paths that may still cause interference. This limitation could result in incomplete mitigation of all sources of interference.

Dynamic Environment: In dynamic environments where satellite movements are rapid or unpredictable, maintaining accurate LOS information for effective nulling becomes challenging. Variations in channel conditions due to mobility may reduce the effectiveness of static nulls directed at specific elevation angles.

Resource Overhead: Constantly updating beamforming vectors based on real-time satellite tracking data consumes additional computational resources at base stations, potentially impacting overall network performance.

Despite these limitations, LOS interference nulling remains a valuable technique for reducing terrestrial-to-satellite interference when implemented effectively within its operational constraints.

How might advancements in non-terrestrial networks influence future spectrum sharing strategies

Advancements in non-terrestrial networks such as Low Earth Orbit (LEO) satellites have significant implications for future spectrum sharing strategies:

Increased Capacity: Non-terrestrial networks like LEO constellations offer expanded coverage capabilities compared to traditional terrestrial infrastructure alone. By integrating these networks into spectrum sharing arrangements, operators can increase network capacity and provide enhanced connectivity services across diverse geographic areas.

2Improved Resilience: Non-terrestrial networks provide redundancy options that enhance network resilience against outages or disruptions affecting ground-based infrastructure. Spectrum sharing with LEO satellites enables seamless service continuity even during terrestrial network failures or disasters.
3Global Connectivity: Leveraging advancements in non-terrestrial technologies allows operators to extend their services globally without being limited by geographical constraints typical of traditional cellular deployments.
4Efficient Spectrum Utilization: Collaborative approaches that integrate both terrestrial and non-terrestrial assets optimize spectrum utilization by dynamically allocating frequencies based on demand patterns across different regions.
5Interference Management: Advanced coordination mechanisms between terrestrial systems and non-terrestrial platforms facilitate effective coexistence strategies through intelligent resource allocation methods tailored to each environment's unique characteristics.
These advancements underscore the transformative potential of incorporating non-terrestrial networks into future spectrum-sharing frameworks aimed at maximizing spectral efficiency while ensuring robust connectivity solutions worldwide