[Paper Review] Spectrum Sharing for 6G Integrated Satellite-Terrestrial Communication Networks Based on NOMA and Cognitive Radio

Xin Liu, Kwok‐Yan Lam+3 more|arXiv (Cornell University)|Jan 27, 2021

Satellite Communication Systems14 references4 citations

TL;DR

This paper proposes a CR-NOMA hybrid spectrum sharing framework for 6G integrated satellite-terrestrial networks (ISTCN) to enhance spectral efficiency and support ubiquitous connectivity. By combining Non-Orthogonal Multiple Access (NOMA) for multi-user multiplexing and Cognitive Radio (CR) for dynamic spectrum access, the scheme enables simultaneous sharing of both idle and busy bands, improving system capacity while managing inter-system interference through power-domain multiplexing and Successive Interference Cancellation (SIC).

ABSTRACT

The explosive growth of bandwidth hungry Internet applications has led to the rapid development of new generation mobile network technologies that are expected to provide broadband access to the Internet in a pervasive manner. For example, 6G networks are capable of providing high-speed network access by exploiting higher frequency spectrum; high-throughout satellite communication services are also adopted to achieve pervasive coverage in remote and isolated areas. In order to enable seamless access, Integrated Satellite-Terrestrial Communication Networks (ISTCN) has emerged as an important research area. ISTCN aims to provide high speed and pervasive network services by integrating broadband terrestrial mobile networks with satellite communication networks. As terrestrial mobile networks began to use higher frequency spectrum (between 3GHz to 40GHz) which overlaps with that of satellite communication (4GHz to 8GHz for C band and 26GHz to 40GHz for Ka band), there are opportunities and challenges. On one hand, satellite terminals can potentially access terrestrial networks in an integrated manner; on the other hand, there will be more congestion and interference in this spectrum, hence more efficient spectrum management techniques are required. In this paper, we propose a new technique to improve spectrum sharing performance by introducing Non-orthogonal Frequency Division Multiplexing (NOMA) and Cognitive Radio (CR) in the spectrum sharing of ISTCN. In essence, NOMA technology improves spectrum efficiency by allowing different users to transmit on the same carrier and distinguishing users by user power levels while CR technology improves spectrum efficiency through dynamic spectrum sharing. Furthermore, some open researches and challenges in ISTCN will be discussed.

Motivation & Objective

• Address the growing demand for ubiquitous, high-capacity 6G connectivity by integrating satellite and terrestrial networks.
• Overcome spectrum scarcity and interference challenges in shared millimeter-wave bands (e.g., 26–40 GHz) between satellite and terrestrial systems.
• Improve spectral efficiency and system capacity in integrated satellite-terrestrial networks through advanced multiple access and dynamic spectrum sharing.
• Enable seamless, all-weather, and all-region coverage for smart cities, IoT, and critical applications like Industry 4.0 and V2X.
• Develop a unified spectrum sharing framework that supports both idle and busy band access with minimal interference to primary users.

Proposed method

• Integrate Non-Orthogonal Multiple Access (NOMA) to allow multiple users to share the same frequency band via power-domain multiplexing.
• Apply Cognitive Radio (CR) techniques to enable dynamic spectrum sensing and opportunistic access to licensed terrestrial bands.
• Use Successive Interference Cancellation (SIC) at the receiver to decode and cancel signals in a specific order based on power levels.
• Implement Non-Continuous OFDM (NC-OFDM) to aggregate non-contiguous idle subcarriers for broadband transmission in CR-NOMA.
• Design a joint spectrum sharing strategy that prioritizes terrestrial communication performance by decoding and canceling satellite signals first when necessary.
• Propose a fair NOMA grouping scheme for edge users to reduce inter-beam and multi-user interference in multi-beam satellite systems.

Experimental results

Research questions

• RQ1 How can NOMA and CR be jointly applied to maximize spectrum utilization in integrated satellite-terrestrial networks?
• RQ2 What is the optimal signal decoding order in CR-NOMA to balance interference management and user fairness?
• RQ3 How can accurate spectrum sensing be achieved in LEO satellite systems despite path loss, shadowing, and mobility?
• RQ4 What receiver design techniques can improve SIC performance under deep fading and noise in satellite channels?
• RQ5 How can the 6G core network functions be integrated with satellite segments to enable seamless global connectivity?

Key findings

• The proposed CR-NOMA framework enables full-spectrum access by allowing satellite and terrestrial users to share both idle and busy bands.
• NOMA improves spectral efficiency by 5–15 times compared to traditional OMA, significantly increasing system capacity.
• SIC-based signal decoding reduces inter-user interference, especially when high-power users are decoded first.
• Accurate spectrum sensing remains a challenge due to atmospheric fading and limited satellite sensing capacity, particularly in LEO systems.
• Inter-beam and multi-user interference degrade edge user performance, necessitating fair NOMA grouping strategies to prioritize low-power users.
• Robust satellite receiver design using adaptive filtering and weak signal detection is essential to mitigate error propagation in imperfect SIC.