OTFS Communication Link Construction and Three-Dimensional Constellation Encryption Design
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摘要: 为满足第6代移动通信(6G)在高速移动场景下高可靠、安全传输需求,针对正交时频空(OTFS)调制的通信链路,该文设计一种新的三维星座加密方案,充分发挥了OTFS与三维星座的性能优势。首先,设计了一种新型三维星座分布图,16个星座点分布在以原点为中心的球体表面,由球面与坐标轴的6个交点及两个平行于XOY平面的正五边形顶点构成,优化后星座点间最小欧氏距离提升5%,平均功率降低11%,星座图性能指数提升10%,改善了误码率性能。此外,提出了一种三维星座映射与旋转加密方案,通过16位量化混沌序列动态选择映射方式,并结合两次星座点旋转操作,实现了三维星座的高效加密。仿真结果表明,相较于现有方案,所提出的方案在确保通信性能的同时,安全性能有较好提升,误码率性能提升约0.6 dB,且密钥空间达10120,能够有效抵抗暴力破解,加密后图像直方图分布均匀,相关系数趋近于0,具有强抗统计攻击能力,且密钥敏感性和鲁棒性测试进一步验证了其安全性能。Abstract:
Objective With the advancement of Sixth-Generation (6G) communication technologies, the demand for highly reliable and secure transmission in high-speed mobile scenarios has grown significantly. Orthogonal Time Frequency Space (OTFS) modulation has emerged as a promising solution due to its superior transmission reliability in high-mobility environments. However, research on the security aspects of OTFS systems remains limited. To address this challenge, this study proposes a Three-Dimensional (3D) constellation encryption scheme for OTFS communication links. The objective is to enhance the security of OTFS systems while preserving communication performance by designing a novel 3D constellation structure and implementing physical-layer dynamic encryption based on a Coupled Map Lattice (CML) spatiotemporal chaotic system. This research provides a secure and efficient transmission strategy for future wireless communication systems. Methods The integration of 3D constellation encryption with OTFS modulation enhances the security of OTFS systems. First, a novel 3D constellation is designed, where 16 constellation points are uniformly distributed on the surface of a sphere centered at the origin. By optimizing the spatial distribution of constellation points, the minimum Euclidean Distance (MED) is increased and the average transmission power is reduced, thereby improving Bit Error Rate (BER) performance. Second, a dynamic encryption scheme for the 3D constellation over the OTFS link is proposed. In this scheme, pseudo-random sequences are generated using the CML system, quantized into 16-bit binary sequences, and employed to control both the selection of mapping rules and the rotational encryption of the 3D constellation. The encryption process operates as follows: first, the mapping rules are dynamically selected based on the quantized chaotic sequences; second, the rotation angles of the constellation points around the X, Y, and Z axes are determined by the same chaotic sequences. This dual encryption mechanism enhances the system’s security while maintaining reliable communication performance. Results and Discussions The performance of the proposed scheme is evaluated through extensive simulations. The results show that the optimized 3D constellation achieves a 22% improvement in MED compared with traditional 2D 16-quadrature amplitude modulation (16QAM). Compared with existing 3D constellations, the proposed design increases the MED by 5%, reduces average transmission power by 11%, and improves the Constellation Figure of Merit (CMF) by 10% ( Table 2 ,Table 3 ). Superior communication performance is also demonstrated, with a BER improvement of approximately 0.6 dB over existing methods (Fig. 5 ,Fig. 6 ). In terms of security, the encryption scheme provides a key space of 10120, effectively resisting brute-force attacks. Key sensitivity tests confirm that even minor changes to the initial key result in completely different decrypted images (Fig. 7 ), verifying the robustness of the encryption mechanism. The encrypted images exhibit uniform histogram distributions (Fig. 8 ) and correlation coefficients near zero (Table 6 ), indicating strong resistance to statistical attacks. Additionally, the scheme maintains reliable performance under noisy conditions, with decrypted images preserving high quality even at low Signal-to-Noise Ratios (SNR) (Fig. 9 ).Conclusions This study combines OTFS communication links with 3D constellation encryption to realize physical-layer security for OTFS systems, enhancing both communication performance and transmission security. The proposed 3D constellation improves the MED by 5%, reduces average power by 11%, and increases the CMF by 10%, thereby enhancing BER performance. The dual dynamic encryption mechanism based on a CML system offers strong security. Simulation results show that the proposed scheme achieves a favorable balance between communication performance and security. BER performance improves by approximately 0.6 dB, while the large key space, high key sensitivity, strong resistance to statistical attacks, and good robustness collectively ensure enhanced security. The combination of OTFS modulation and 3D constellation encryption not only improves spectrum resource utilization but also strengthens channel confidentiality, enhancing resilience to interference and potential attacks. This scheme improves transmission security without compromising communication performance, offering broad application prospects in fields such as the Internet of Things, unmanned aerial vehicles, satellite communication, and ocean communication. The proposed approach is expected to provide more secure and reliable transmission solutions for future wireless communication systems. -
表 1 3D 16-ary星座图坐标
X轴坐标 Y轴坐标 Z轴坐标 A1 1 0 0 A2 –1 0 0 A3 0 1 0 A4 0 –1 0 A5 0 0 1 A6 0 0 –1 A7 0.5050 0.5050 0.7000 A8 – 0.3242 0.6363 0.7000 A9 – 0.7054 – 0.1117 0.7000 A10 – 0.1117 – 0.7054 0.7000 A11 0.6363 – 0.3242 0.7000 A12 0.5050 0.5050 – 0.7000 A13 – 0.3242 0.6363 – 0.7000 A14 – 0.7054 – 0.1117 – 0.7000 A15 – 0.1117 – 0.7054 – 0.7000 A16 0.6363 – 0.3242 – 0.7000 表 3 不同星座性能对比
表 4 选择映射规则
Y1Y2Y3Y4 A1A2$ \cdots $A16 0000 9;0;15;6;3;5;10;14;1;2;11;12;13;8;7;4; 0001 2;1;4;11;8;14;7;5;0;9;6;13;12;3;10;15; 0010 7;2;13;8;1;11;4;12;3;0;5;14;15;6;9;10; 0011 0;3;10;5;6;12;9;11;2;7;8;15;141;4;13; 0100 13;4;11;2;7;1;14;10;5;6;15;8;9;12;3;0; 0101 6;5;0;15;12;10;3;1;4;13;2;9;8;7;14;11; 0110 3;6;9;12;5;15;0;8;7;4;1;10;11;2;13;14; 0111 4;7;14;1;2;8; 1315 ;6;3;12;11;10;5;0;9;1000 1;8;7;14;11;13;2;6;9;10;3;4;5;0;15;12; 1001 10;9;12;3;0;6;15;13;8;1;14;5;4;11;2;7; 1010 15;10;5;0;9;3;12;4;11;8;13;6;7;14;1;2; 1011 8;11;2;13;14;4;1;3;10;15;0;7;6;9;12;5; 1100 5;12;3;10;15;9;6;2;13;14;7;0;1;4;11;8; 1101 14;13;8;7;4;2;11;9;12;5;10;1;0;15;6;3; 1110 11;14;1;4;13;7;8;0;15;12;9;2;3;10;5;6; 1111 12;15;6;9;10;0;5;7;14;11;4;3;2;13;8;1; 表 5 三维星座旋转加密规则
Y5Y6Y7/Y8Y9Y10 旋转规则 000 不旋转 001 绕Z轴旋转 010 绕Y轴旋转 011 分别绕Y轴、Z轴旋转 100 绕X轴旋转 101 分别绕X轴、Z轴旋转 110 分别绕X轴、Y轴旋转 111 分别绕X轴、Y轴、Z轴旋转 表 6 复杂度对比
表 7 相关系数对比
图像名称/编号 水平方向 垂直方向 对角方向 Cameraman
(512×512)原始图像 0.9820 0.9882 0.9731 本文加密 – 0.0025 – 0.0009 – 0.0388 文献[16] – 0.0100 – 0.0087 0.0131 文献[17] 0.0103 – 0.0035 0.0597 7.1.09
(512×512)原始图像 0.8691 0.9276 0.8915 本文加密 0.0016 – 0.0023 0.0046 5.1.09
(256×256)原始图像 0.8501 0.8716 0.8723 本文加密 – 0.0023 – 0.0083 – 0.0097 5.1.10
(256×256)原始图像 0.8067 0.8552 0.8950 本文加密 – 0.0162 – 0.0056 0.0011 表 8 PSNR对比
图像名称/编号 SNR=10 SNR=12 SNR=14 Cameraman
(512×512)本文加密 23.2124 29.9727 39.5546 文献[16] 21.2720 27.7008 36.4857 文献[17] 19.0376 24.4215 33.0136 7.1.09
(512×512)本文加密 24.6201 30.6419 36.5844 文献[16] 22.8693 28.9984 35.5868 文献[17] 20.536 25.8338 33.5381 5.1.09
(256×256)本文加密 24.5723 30.5089 36.7201 文献[16] 23.1655 29.2437 35.8463 文献[17] 20.7219 25.8530 33.3320 5.1.10
(256×256)本文加密 24.1365 29.8549 35.8519 文献[16] 22.2935 28.3417 35.9071 文献[17] 19.9616 25.3111 32.1762 表 9 MSE对比
图像名称/编号 SNR=10 SNR=12 SNR=14 Cameraman
(512×512)本文加密 310.3394 65.4357 7.2048 文献[16] 485.1497 110.4092 14.6053 文献[17] 811.5578 234.9259 32.4877 7.1.09
(512×512)本文加密 224.4243 56.0901 14.2770 文献[16] 335.8523 81.8917 17.9639 文献[17] 574.7482 169.7079 28.7921 5.1.09
(256×256)本文加密 226.9086 57.8356 13.8380 文献[16] 313.7177 77.3940 16.9219 文献[17] 550.6714 168.9599 30.1913 5.1.10
(256×256)本文加密 250.8602 57.2348 16.9002 文献[16] 383.4729 95.2605 16.6867 文献[17] 656.0297 191.4116 39.3964 -
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