Secrecy Sum Rate Maximization in Non-Orthogonal Multiple Access (1603.04290v1)

Abstract: Non-orthogonal multiple access (NOMA) has been recognized as a promising technique for providing high data rates in 5G systems. This letter is to study physical layer security in a single-input single-output (SISO) NOMA system consisting of a transmitter, multiple legitimate users and an eavesdropper. The aim of this letter is to maximize the secrecy sum rate (SSR) of the NOMA system subject to the users' quality of service (QoS) requirements. We firstly identify the feasible region of the transmit power for satisfying all users' QoS requirements. Then we derive the closed-form expression of an optimal power allocation policy that maximizes the SSR. Numerical results are provided to show a significant SSR improvement by NOMA compared with conventional orthogonal multiple access (OMA).

• The paper proposes a closed-form power allocation strategy to maximize the secrecy sum rate in SISO NOMA systems without requiring eavesdropper channel information.
• Numerical analysis shows the proposed method significantly enhances the secrecy sum rate compared to OMA, with gains increasing with more users and varying QoS thresholds.
• The findings suggest leveraging NOMA effectively improves data security levels in systems like 5G and can be extended to MIMO settings for further security boosts.

Secrecy Sum Rate Maximization in Non-Orthogonal Multiple Access

The paper explores an advanced topic within wireless communication systems, particularly focusing on Non-Orthogonal Multiple Access (NOMA) and its implications for physical layer security. The key objective pursued by the authors is to enhance the secrecy sum rate (SSR) in a single-input single-output (SISO) NOMA setup. The system under consideration involves a transmitter, multiple legitimate users, and an eavesdropper, emphasizing the necessity of ensuring secure communication.

Technical Contributions

The work systematically progresses through several core contributions:

1. Feasible Region Identification: One of the foundational steps involves identifying the feasible power transmission domain for satisfying the quality of service (QoS) requirements of all users. The authors derive the minimum power, $P_{\text{min}}$, necessary for these conditions.
2. Optimal Power Allocation: Theoretical derivations yield a closed-form power allocation strategy that maximizes the SSR. The solution primarily hinges on allocating available resources, particularly in such a manner that the user with the best channel conditions (i.e., the M-th user) receives increased focus to optimize security without requiring knowledge of the eavesdropper's channel state information.
3. Numerical Analysis: The results demonstrate that the proposed method significantly enhances the SSR compared to traditional orthogonal multiple access (OMA) systems. Evident from numerical simulations, the gain in SSR becomes more pronounced with an increasing number of users and under varying QoS thresholds, highlighting the efficiency of NOMA in maximizing spatial diversity and spectral efficiency.

Implications and Future Work

The theoretical and practical implications of this work hold tangible promise for contemporary and future cellular systems. The findings suggest that leveraging NOMA can effectively improve data security levels in 5G networks, where multiple users need simultaneous service in the same frequency band.

Considering the paper's framework, the authors suggest extending the paper to multiple-input multiple-output (MIMO) settings to further boost system security. This direction could also incorporate advanced channel estimation techniques to alleviate the practical challenge of needing detailed channel state information.

Conclusion

This work contributes an essential piece to the puzzle of secure wireless communication by integrating the principles of NOMA with physical layer security paradigms. The meticulous approach in deriving a closed-form power allocation policy offers a robust method applicable to real-world scenarios, reaffirming the utility of NOMA in evolving telecommunications architectures. As wireless communication moves towards more efficient, secure, and scalable systems, studies like this lay the foundation for further research and development within the domain.