Satellite Data Speeds Boosted by New Signal Compression Technique

Scientists are tackling the challenges of reliable, high-speed communication with low-Earth orbit (LEO) satellites using a novel approach to signal modulation and processing. Chaorong Zhang from Macao Polytechnic University, alongside Hui Xu and Benjamin K. Ng, with further collaboration from Yue Liu, Chan-Tong Lam, and Halim Yanikomeroglu, present a flexible Faster-Than-Nyquist Orthogonal Time Frequency Space (FTN-OTFS) scheme designed to minimise onboard power consumption and combat the effects of rapidly changing signal conditions. This research is significant because it offers a pathway to substantially improve data rates and robustness in LEO satellite-to-ground links, crucial for supporting the increasing demand for global connectivity and real-time applications.

Optimised LEO satellite communications via dynamic Faster-than-Nyquist OTFS modulation offer improved spectral efficiency

Scientists have developed a new lightweight communication scheme for Low Earth Orbit (LEO) satellites, addressing the challenges of limited onboard power and rapidly changing signal conditions. To overcome the effects of channel aging and minimise computational demands, researchers implemented a Signal-to-Noise Ratio (SNR)-aware flexible FTN strategy.
This innovative approach employs a low-complexity Look-Up Table (LUT) to dynamically adjust the time-domain compression factor based on instantaneous channel responses. By intelligently balancing rate acceleration and interference, the system maximises spectral efficiency while ensuring reliable communication with minimal processing requirements.

This mechanism effectively resolves the trade-off between achieving higher data rates and maintaining signal integrity. The study further provides a comprehensive theoretical analysis, deriving analytical expressions for key performance indicators including effective throughput, energy efficiency, and bit error rate.

Extensive simulations demonstrate that the proposed LEO-FFTN-OTFS scheme significantly outperforms static FTN benchmarks, offering a superior combination of high throughput and robustness for next-generation LEO communications. This breakthrough reveals a substantial improvement in performance, particularly in scenarios with extreme satellite mobility exceeding 7.6km/s, where conventional systems struggle with Doppler shifts and channel variations.

Experiments show the new system effectively converts a rapidly fading, doubly-selective channel into a quasi-static, sparse interaction, enhancing resilience against fractional Doppler shifts and eliminating the need for complex parameter tuning. The research establishes a pathway towards more efficient and reliable satellite communication, crucial for supporting delay-sensitive applications like autonomous driving, remote industrial control, and emergency disaster relief. This work opens possibilities for ubiquitous, three-dimensional global connectivity, leveraging the advantages of LEO constellations while mitigating their inherent challenges.

System modelling and SNR-dependent faster-than-Nyquist optimisation for LEO satellite communications offer significant performance gains

Scientists proposed a lightweight Low Earth Orbit (LEO)-assisted flexible faster-than-Nyquist (FTN)-orthogonal time frequency space (OTFS) scheme to mitigate power consumption and channel variability in non-terrestrial networks. The research team established a rigorous system framework incorporating 3GPP Tapped Delay Line (TDL) channel models to accurately simulate high-mobility propagation characteristics.

These models enabled precise capture of the dynamic channel conditions experienced in LEO satellite communications. To address channel aging, researchers developed a Signal-to-Noise Ratio (SNR)-aware flexible FTN strategy. This innovative approach utilises a low-complexity Look-Up Table (LUT) to adaptively optimise the time-domain compression factor based on instantaneous channel responses.

The LUT dynamically adjusts compression, effectively balancing rate acceleration against potential interference, thereby maximising spectral efficiency while maintaining reliability. The study pioneered a comprehensive theoretical analysis, deriving analytical expressions for effective throughput, energy efficiency, and bit error rate.

These expressions quantify the performance gains achieved by the proposed LEO-FFTN-OTFS scheme. Extensive simulations then demonstrated that the scheme significantly outperforms static FTN benchmarks, delivering a superior balance of high throughput and robustness. Specifically, the simulations validated the method’s ability to maintain performance under challenging high-mobility conditions.

This work harnessed the power of adaptive compression to overcome limitations of traditional FTN systems. The resulting LEO-FFTN-OTFS scheme offers a promising solution for next-generation LEO satellite communications, enabling efficient and reliable data transmission in demanding environments.

Performance gains from a flexible faster-than-Nyquist OTFS scheme for high-mobility LEO networks are significant

Scientists have developed a lightweight Low Earth Orbit (LEO)-assisted flexible faster-than-Nyquist (FTN)-orthogonal time frequency space (OTFS) scheme to address power consumption and fast time-varying channels in non-terrestrial networks. The research establishes a system framework utilising 3GPP Tapped Delay Line (TDL) channel models to accurately represent high-mobility propagation characteristics.

Experiments revealed that the proposed scheme significantly outperforms static FTN benchmarks, offering a superior balance of high throughput and robustness for next-generation LEO systems. The team measured the performance of an SNR-aware flexible FTN strategy, employing a low-complexity Look-Up Table (LUT) to adaptively optimise the time-domain compression factor based on instantaneous channel responses.

Results demonstrate that this mechanism effectively resolves the trade-off between rate acceleration and interference penalty, maximising spectral efficiency while satisfying strict reliability constraints with minimal processing overhead. The LUT enables real-time adaptability, allowing the system to exploit high-SNR windows for rate acceleration and revert to robust modes during deep fades.

Comprehensive theoretical analysis derived analytical expressions for effective throughput, energy efficiency, and bit error rate. Measurements confirm that a time-domain compression factor α, where 0 Tests prove that the adoption of α = 0.8 causes pulses to overlap at the sampling instant, intentionally introducing inter-symbol interference to boost the transmission rate.

Furthermore, the research shows that this non-orthogonal transmission results in a spectral dip, effectively acting as a frequency-selective channel. The forward link channel between the LEO satellite and the ground user equipment is characterised by large-scale path loss, calculated as L = Lb + Lg + Ls, where Lb, Lg, and Ls represent basic path loss, atmospheric gas attenuation, and scintillation loss, respectively. The basic path loss, Lb, is determined by the Free-Space Path Loss (FSPL), Shadow Fading (SF), and Clutter Loss (CL), expressed as Lb = FSPL(d, fc) + SF + CL(θE, fc).

Performance evaluation of a dynamic compression OTFS scheme for LEO networks reveals significant gains

Scientists have proposed a new lightweight Low Earth Orbit (LEO)-assisted flexible faster-than-Nyquist (FTN)-orthogonal time frequency space (OTFS) scheme to address the challenges of limited onboard power and rapidly changing channels in non-terrestrial networks. This research establishes a detailed system framework utilising realistic 3GPP Tapped Delay Line channel models, accurately simulating high-mobility propagation environments.

An SNR-aware flexible FTN strategy was developed, employing a low-complexity Look-Up Table to dynamically adjust the time-domain compression factor based on instantaneous channel conditions. The proposed scheme effectively balances rate acceleration with interference mitigation, maximising spectral efficiency while maintaining reliability with minimal processing demands.

Theoretical analysis yielded expressions for effective throughput, energy efficiency, and bit error rate, and extensive simulations demonstrated significant performance gains over static FTN benchmarks. The authors acknowledge a sensitivity to significant SNR estimation errors, particularly with larger OTFS grid dimensions, suggesting a trade-off between frame size and robustness.

Future research could focus on refining SNR estimation techniques to further enhance performance in challenging conditions. This study contributes vital insights for future green LEO satellite communications by addressing the specific constraints of Doppler shifts, limited bandwidth, and onboard energy scarcity.

The LEO-FFTN-OTFS scheme achieves an optimal trade-off between reliability, computational efficiency, and spectral efficiency, maximising throughput across a wide range of signal-to-noise ratios. By dynamically adjusting the compression factor, the adaptive strategy effectively resolves the error floor issue of fixed FTN systems and mitigates the effects of processing latency in high-mobility scenarios.