Time-Scale-Adaptable Spectrum Sharing Achieves Efficient Hybrid -Terrestrial Network Coverage

Researchers are tackling the growing challenge of delivering ubiquitous wireless coverage by investigating innovative spectrum sharing techniques for hybrid satellite-terrestrial networks. Yanmin Wang from Minzu University of China, Wei Feng and Shidong Zhou from Tsinghua University, along with Yunfei Chen et al, present a new framework that dynamically adjusts to varying network conditions, optimising how satellite and terrestrial links utilise the same radio frequencies. This work is significant because it proposes a low-complexity solution , relying only on readily available statistical channel information , to a traditionally difficult mixed integer programming problem, potentially unlocking substantial performance gains and improved quality of service for users even with interference constraints.

Hybrid Networks Share Spectrum Without Synchronisation

This breakthrough addresses the growing demand for connectivity by efficiently utilising available spectrum, a critical resource becoming increasingly scarce. The research team proposed a system where satellite links opportunistically share time-slotted subcarriers with terrestrial links, overcoming limitations imposed by differing link delays between satellite and ground-based infrastructure. Crucially, the study achieves this without requiring precise, network-wide time synchronisation, a traditionally challenging aspect of such integrated networks. Experiments show that the link feature sketching effectively utilises the diversity offered by the spatial distribution of users, leading to substantial performance gains.
The proposed scheme promises a significant performance boost, even when operating with coarse network-wide time synchronisation, a practical advantage over systems demanding millisecond-level precision. This adaptability is achieved by flexibly adjusting the time scale for satellite-terrestrial cooperation according to specific application requirements. This work builds upon previous research focusing primarily on frequency-domain spectrum sharing, extending it to incorporate time-domain coordination for a more holistic approach. Unlike earlier studies that often required instantaneous CSI, this research leverages statistical CSI, making it more robust and practical for real-world deployment. The team’s innovative use of link feature sketching not only improves efficiency but also allows the system to capitalise on the spatial diversity of users, enhancing overall network capacity. The research establishes a foundation for future 6G networks, paving the way for seamless integration of satellite and terrestrial components to deliver truly ubiquitous connectivity.

Hybrid Network Spectrum Sharing via Time Synchronisation offers

The study pioneered a method leveraging coarse network-wide time synchronization, enabling flexible adjustment of the cooperation time scale according to practical requirements. Experiments employed a successive-approximation-aided convex optimization technique to solve the power control problem, transforming it into a series of convex subproblems by approximating terms with first-order Taylor expansions. To handle the expectation operator within the optimization, the Monte Carlo method was utilized, approximating expected values with the average of Q random samples, where h represents channels for all links and g(h) encompasses relevant expressions dependent on those channels. Link scheduling for cellular users (CUs) and satellite users (SUs) was approached by considering the impact of SU power control, recognizing the inherent coupling in the system model.

Given the NP-hard nature of direct link scheduling, the research team adopted a clustering approach inspired by prior work, grouping BS-CU and SU-satellite links into K clusters, one per subcarrier, to facilitate opportunistic spectrum sharing. The technique reveals that delicately-designed feature vectors enable efficient clustering of links based on similarity in interference coordination, preserving spatial diversity and fully utilizing it for spectrum sharing. Specifically, the impact of SU power control was incorporated into the feature sketching process for the links, defining Vk and Uk as K BS-CU and SU-satellite link clusters scheduled on subcarrier k. Researchers defined ∆C(su) u and ∆C(cu) i,r,v as changes in capacity for SUs and CUs, respectively, and established Cmin sum as a fixed component representing the minimum achievable sum rate for QoS guarantees.

Furthermore, γ(k,min) i,r,v and p(k,max) u were determined to define the minimum interference and maximum transmit power, respectively, for each cluster, enabling a lower bound on the maximum achievable sum rate. This approach enables the utilization of these lower bounds in feature sketching, allowing for performance potential assessment without complex coupling between scheduling and power control. The study pioneered hierarchical link clustering, dividing BS-CU links into coarse groups based on allocated subcarriers, and matching SU-satellite link clustering to these groups.

Joint Scheduling Boosts Hybrid Network Performance significantly

The team measured performance gains even under strict inter-link interference constraints, demonstrating the robustness of the proposed scheme. Data shows that link feature sketching effectively utilises the diversity of links created by the spatial distribution of users, enhancing overall network performance. Scientists recorded significant performance improvements through the implementation of this time-scale-adaptable framework, circumventing the challenges of achieving fine-grained network-wide time synchronization. Tests prove that the proposed scheme delivers a substantial performance gain, even when faced with stringent inter-link interference limitations.

The breakthrough delivers a practical solution for 6G era communication, addressing the need for ubiquitous coverage and efficient spectrum utilisation. Furthermore, the research considered satellite selection, adapting to situations where multiple satellites are available, increasing system flexibility and resilience. Measurements confirm that the adjustable time scale for satellite-terrestrial cooperation allows for optimisation based on specific application needs and network conditions. The team’s approach to link clustering and grouped time slice allocation minimises the required synchronisation precision, making it more feasible for real-world deployment.

Hybrid Network Spectrum Sharing via Optimisation offers significant

This research proposes a time-scale-adaptable system where satellite links opportunistically share spectrum with terrestrial links, utilising coarse network-wide time synchronisation. The significance of this work resides in its ability to improve spectral efficiency in hybrid networks, potentially alleviating spectrum scarcity issues. Simulation results confirm that the proposed approach, employing link-feature sketching and hierarchical clustering, delivers substantial performance gains even with strict interference limitations. However, the authors acknowledge that the scheme’s complexity grows linearly with network size and the number of users, potentially limiting scalability in very large deployments.

Future research could focus on refining the complexity analysis and exploring methods to further reduce computational overhead. The team suggests investigating adaptive techniques for adjusting the time scale based on real-time network conditions, and extending the framework to accommodate more dynamic network topologies. These advancements could pave the way for more efficient and robust hybrid satellite-terrestrial communication systems.