Abstract
Federated Learning (FL) enables collaborative model training across autonomous vehicles (AVs) without sharing raw driving data, but excessive uplink/downlink communication over bandwidth-constrained vehicular-to-everything links and privacy leakage through gradient inversion attacks limit its deployment. This paper proposes Janus, a unified FL framework combining adaptive Top-K gradient compression with error feedback on the uplink, genuine additive homomorphic encryption (HE, not a noise-based proxy) for secure aggregation, and compressed global-model broadcasting on the downlink. On real KITTI object-detection labels with 20 non-IID clients, Janus matches FedAvg/FedProx/QSGD accuracy (95.34% ± 0.01% vs. 95.35% ± 0.03%, 3 seeds) while cutting combined communication by 61.8%; the same saving (61.0%) is independently reproduced on CIFAR-10. A real Paillier HE implementation is verified exact (error below 10⁻⁶), and a genuine gradient-inversion attack (Deep Leakage from Gradients) shows raw gradients are reconstructed almost perfectly (relative error 0.0026) versus 0.0775 for Janus's compressed updates, with HE removing the attack surface entirely. The same communication saving is further reproduced on real KITTI camera images with a CNN roughly 24x larger than the tabular model and on a multimodal model fusing real camera and LiDAR features, alongside additional baselines (FedPAQ, DP-FedAvg), membership-inference and model-poisoning attacks, Markov-chain mobility, simulated network latency (61.9% reduction), an energy proxy (45.1% reduction), and a formal convergence analysis. To the authors' knowledge, this is the first vehicular-FL evaluation combining joint uplink-downlink compression with genuine HE-based privacy, validated through real cryptography, real privacy attacks, statistical testing, cross-dataset and cross-modality generalisation, and a convergence guarantee.References
- Alistarh, Dan, Demjan Grubic, Jerry Li, Ryota Tomioka, and Milan Vojnovic. ”QSGD: Communication-efficient SGD via Gradient Quantization and Encoding.” Advances in neural information processing systems 30 (2017).
- Amiri, Mohammad Mohammadi, and Deniz Gündüz. ”Federated Learning Over Wireless Fading Channels.” IEEE transactions on wireless communications 19, no. 5 (2020): 3546-3557.
- Bonawitz, Keith, Vladimir Ivanov, Ben Kreuter, Antonio Marcedone, H. Brendan McMahan, Sarvar Patel, Daniel Ramage, Aaron Segal, and Karn Seth. ”Practical Secure Aggregation for Privacy-Preserving Machine Learning.” In proceedings of the 2017 ACM SIGSAC Conference on Computer and Communications Security, 2017, 1175-1191.
- Chellapandi, Vishnu Pandi, Liangqi Yuan, Christopher G. Brinton, Stanislaw H. Żak, and Ziran Wang. ”Federated Learning for Connected and Automated Vehicles: A Survey of Existing Approaches and Challenges.” IEEE Transactions on Intelligent Vehicles 9, no. 1 (2023): 119-137.
- Chen, Mingzhe, Zhaohui Yang, Walid Saad, Changchuan Yin, H. Vincent Poor, and Shuguang Cui. ”A Joint Learning and Communications Framework for Federated Learning Over Wireless Networks.” IEEE transactions on wireless communications 20, no. 1 (2020): 269-283.
- Geiger, Andreas, Philip Lenz, Christoph Stiller, and Raquel Urtasun. ”Vision Meets Robotics: The Kitti Dataset.” The international journal of robotics research 32, no. 11 (2013): 1231-1237.
- He, Zixiao, Gengming Zhu, Shaobo Zhang, Entao Luo, and Yijiang Zhao. ”FedDT: A Communication-Efficient Federated Learning via Knowledge Distillation and Ternary Compression.” Electronics 14, no. 11 (2025): 2183.
- Kairouz, Peter, and H. Brendan McMahan. ”Advances and Open Problems in Federated Learning.” Foundations and trends in machine learning 14, no. 1-2 (2021): 1-210.
- Karimireddy, Sai Praneeth, Satyen Kale, Mehryar Mohri, Sashank Reddi, Sebastian Stich, and Ananda Theertha Suresh. ”Scaffold: Stochastic Controlled Averaging for Federated Learning.” In International conference on machine learning, PMLR, 2020, 5132-5143.
- Konečný, Jakub, H. Brendan McMahan, Daniel Ramage, and Peter Richtárik. ”Federated optimization: Distributed Machine Learning for On-Device Intelligence.” arXiv preprint arXiv:1610.02527 (2016).
- Li, Tian, Anit Kumar Sahu, Ameet Talwalkar, and Virginia Smith. ”Federated Learning: Challenges, Methods, and Future Directions.” IEEE signal processing magazine 37, no. 3 (2020): 50-60.
- Li, Tian, Anit Kumar Sahu, Manzil Zaheer, Maziar Sanjabi, Ameet Talwalkar, and Virginia Smith. ”Federated Optimization in Heterogeneous Networks.” Proceedings of Machine learning and systems 2 (2020): 429-450.
- Lin, Yujun, Song Han, Huizi Mao, Yu Wang, and William J. Dally. ”Deep Gradient Compression: Reducing the Communication Bandwidth for Distributed Training.” arXiv preprint arXiv:1712.01887 (2017).
- McMahan, Brendan, Eider Moore, Daniel Ramage, Seth Hampson, and Blaise Aguera y Arcas. ”Communication-efficient Learning of Deep Networks from Decentralized Data.” In Artificial intelligence and statistics, Pmlr, 2017, 1273-1282.
- Nguyen, Dinh C., Ming Ding, Pubudu N. Pathirana, Aruna Seneviratne, Jun Li, and H. Vincent Poor. ”Federated Learning for Internet of Things: A Comprehensive Survey.” IEEE communications surveys & tutorials 23, no. 3 (2021): 1622-1658.
- Qi, Pian, Diletta Chiaro, Antonella Guzzo, Michele Ianni, Giancarlo Fortino, and Francesco Piccialli. ”Model Aggregation Techniques in Federated Learning: A Comprehensive Survey.” Future Generation Computer Systems 150 (2024): 272-293.
- Reddi, Sashank, Zachary Charles, Manzil Zaheer, Zachary Garrett, Keith Rush, Jakub Konečný, Sanjiv Kumar, and H. Brendan McMahan. ”Adaptive Federated Optimization.” arXiv preprint arXiv:2003.00295 (2020).
- Reisizadeh, Amirhossein, Aryan Mokhtari, Hamed Hassani, Ali Jadbabaie, and Ramtin Pedarsani. ”Fedpaq: A Communication-Efficient Federated Learning Method with Periodic Averaging and Quantization.” In International conference on artificial intelligence and statistics, PMLR, 2020, 2021-2031.
- Tran, Nguyen H., Wei Bao, Albert Zomaya, Minh NH Nguyen, and Choong Seon Hong. ”Federated Learning Over Wireless Networks: Optimization Model Design and Analysis.” In IEEE INFOCOM 2019-IEEE conference on computer communications, IEEE, 2019, 1387-1395.
- Wang, Jianyu, Qinghua Liu, Hao Liang, Gauri Joshi, and H. Vincent Poor. ”Tackling the Objective Inconsistency Problem in Heterogeneous Federated Optimization.” Advances in neural information processing systems 33 (2020): 7611-7623.
- Yang, Qiang, Yang Liu, Tianjian Chen, and Yongxin Tong. ”Federated Machine Learning: Concept and Applications.” ACM Transactions on Intelligent Systems and Technology (TIST) 10, no. 2 (2019): 1-19.
- Zhang, Chengliang, Suyi Li, Junzhe Xia, Wei Wang, Feng Yan, and Yang Liu. ”{BatchCrypt}: Efficient Homomorphic Encryption for {Cross-Silo} Federated Learning.” In 2020 USENIX annual technical conference (USENIX ATC 20), 2020, 493-506.
- Zhang, Hengrun, Kai Zeng, and Shuai Lin. ”Federated Graph Neural Network for Fast Anomaly Detection in Controller Area Networks.” IEEE transactions on information forensics and security 18 (2023): 1566-1579.
- Zhang, Xinran, Zheng Chang, Tao Hu, Weilong Chen, Xin Zhang, and Geyong Min. ”Vehicle Selection and Resource Allocation for Federated Learning-Assisted Vehicular Network.” IEEE Transactions on Mobile Computing 23, no. 5 (2023): 3817-3829.
- Zhou, Hongliang, Yifeng Zheng, Hejiao Huang, Jiangang Shu, and Xiaohua Jia. ”Toward Robust Hierarchical Federated Learning in Internet of Vehicles.” IEEE Transactions on Intelligent Transportation Systems 24, no. 5 (2023): 5600-5614.
- Zhu, Ligeng, Zhijian Liu, and Song Han. ”Deep Leakage from Gradients.” Advances in neural information processing systems 32 (2019).
- Karimireddy, Sai Praneeth, Quentin Rebjock, Sebastian Stich, and Martin Jaggi. ”Error Feedback Fixes Signsgd and Other Gradient Compression Schemes.” In International conference on machine learning, PMLR, 2019, 3252-3261.
- Stich, Sebastian U., Jean-Baptiste Cordonnier, and Martin Jaggi. ”Sparsified SGD with Memory.” Advances in neural information processing systems 31 (2018).
- McMahan, H. Brendan, Daniel Ramage, Kunal Talwar, and Li Zhang. ”Learning Differentially Private Recurrent Language Models.” arXiv preprint arXiv:1710.06963 (2017)

Journal of Trends in Computer Science and Smart Technology