Lin Xiang

I am a research group leader in the Communications Engineering Lab, and an Atheme Young Investigator at TU Darmstadt. I obtained my Ph.D. in Electrical, Electronic, and Information Engineering from the Friedrich-Alexander-University of Erlangen-Nuremberg in Germany. Prior to that, I received my M.Eng in Communications and Information System and B.Eng in Electronics and Information Engineering, both from the Huazhong University of Science and Technology in China. I was a postdoctoral researcher at the University of Luxembourg, and a visiting researcher at the University of Bologna (supported by the Erasmus-Mundus program of the European Commission). 

I am also the program area coordinator within the area of communication (KOM) in  the LOEWE center emergenCITY.

News

• Several interesting topics for Master thesis/Project seminar are available for inquiry

• Jan. 2025: We will present one paper in SCC'25 Karlsruhe, one paper in WCNC'25 Milan (Italy), and two papers in ICC'25 Montreal (Canada)

• Jan. 2025: One journal paper accepted for publication in IEEE Trans. Commun.

• Sep. 2024: We will present two papers in PIMRC'24 Valencia (Spain) and three papers in Globecom'24 Cape Town (South Africa) 

• Jul. 2024: One journal paper accepted for publication in IEEE Trans. Wireless Commun.

• Jan. 2024: We will present one paper in WCNC'24 Dubai (UAE) , three papers in ICC'24 Denver (US), and another paper in WSA'24 Dresden

• Dec. 2023: The second phase of emergenCITY was accepted for funding 

• Sep. 2023: We will present two papers in Globecom'23 Kuala Lumpur (Malaysia) 

• Jul. 2023: Lecture "Mobile Communications" in SS 2023 received very positive evaluation

Research Interests

(1) Advanced wireless physical-layer technologies: 

• Multiple-input multiple-output (MIMO), massive MIMO, and rotatable antenna array (RAA)

• Orthogonal and non-orthogonal multiple-access (OMA / NOMA),

• Cooperative communication

• Physical layer security (PLS) 

• Finite-blocklength communications

• Joint sensing and commuication (JSAC)

• Adaptive decentralized computing and caching over wireless

(2) Optimization / game / learning theory and Exact / Approximation algorithms:

• Convex and nonconvex optimization theory/algorithms

• Exact/Approximate dynamic programming and reinforcement learning

• Cooperative and noncooperative games

• Learning-assisted optimization and games 

Research Theme 1: From Communication to Joint Sensing and Communication (JSAC) in Ground and Aerial Networks

Cyber-physical systems (CPSs) will bring great socio-techno-economic values and JSAC technologies are expected to significantly enhance the support of CPSs in 6G. In conventional wireless information systems, the relative movements between transmitters and receivers are unpredictable, rarely exploitable, and even detrimental to information sensing and comunication. However, emerging CPSs such as robots, unmanned aerial vehicles (UAVs), and ground (autonomous) vehicles are capable of controllable/programmable motion in space and over time. This feature can be leveraged to enable novel advanced JSAC paradigms for CPSs in 6G. In this context, we aim to exploit motion (including translation, rotation, transformation, swarming etc.) in space and over time to facilitate tailored design and optimization of information sensing and communication for and by movable CPSs.  We also consider how to best tradeoff between the complexity and overhead incurred in motion control and the achieved performances, particularly in complex environments. 

Selected Papers

1.1 Communications Against  Uncertainties and Imperfections

• X. Zhang, L. Xiang, J. Wang,  P. Zhu, D. W. K. Ng, and X. Gao, "Hybrid Precoding for mmWave Massive MIMO with Finite Blocklength", accepted for publication in IEEE Transactions on Communications, Jan. 2025

• X. Zhang, L. Xiang, J. Wang, and X. Gao, “Beamforming Design for Massive MIMO Multicast with Finite Transmission Blocklength”, IEEE Transactions on Wireless Communications,  vol. 23, no. 10, pp. 15018-15034, Oct. 2024.

• J. Ye, L. Xiang, and X. Ge, "Spatial-Temporal Modeling and Analysis of Reliability and Delay in Urban V2X Networks", IEEE Transactions on Network Science and Engineering, vol. 10, no. 3, pp. 1752 - 1765, May-Jun. 2023.

• Y. Wang, L. Xiang, J. Zhang, and X. Ge, “Connectivity Analysis for Large-Scale Intelligent Reflecting Surface Aided mmWave Cellular Networks”, in Proc. IEEE PIMRC (virtual), Sep. 2022.

• Z. Li, L. Xiang, and X. Ge, “Age of Information Modeling and Optimization for Fast Information Dissemination in Vehicular Social Networks,” IEEE Transactions on Vehicular Technology, vol. 71, no. 5, pp. 5445-5459, May 2022.

• Z. Li, L. Xiang, X. Ge, G. Mao, and H.-C. Chao, “Latency and Reliability of mmWave Multi-hop V2V Communications under Relay Selection”, IEEE Transactions on Vehicular Technology, vol. 69, no. 9, pp. 9807-9821, Sep. 2020.

1.2 Communications Exploiting Movements 

• B.  Yilmaz, A. Klein, and L. Xiang, "Completion Time Minimization for UAV-aided Communications with Rotatable Dipole Array", in Proc. IEEE ICC, Montreal, Canada, Jun. 2025.

• L. Xiang, X. Zhu, F. Pei, and D. W. K. Ng, "Energy-Efficient Dynamic Array-Steering and Beamforming for UAV-Aided Communications", in Proc. IEEE Globecom, Cape Town, South Africa, Dec. 2024.

• L. Xiang, F. Pei, and A. Klein, "Joint Optimization of Beamforming and 3D Array Steering for Multi-antenna UAV Communications",  in Proc. IEEE WCNC, Dubai, United Arab Emirates, Apr. 2024.

• Y. Wang, L. Xiang, and A. Klein, “Completion Time Minimization for UAV-Based Communications With A Finite Buffer”, in Proc. IEEE ICC, Rome, Italy, May 2023.

• B. Yilmaz, L. Xiang, and A. Klein, “UAV-Assisted Delay-Sensitive Communications with Uncertain User Locations: A Cost Minimization Approach”, in Proc. IEEE PIMRC (virtual), Sep. 2022.

• G. Lu, J. Zhang, L. Xiang, and X. Ge, “A Global Optimization Method for Energy-Minimal UAV-Aided Data Collection over Fixed Flight Path,” in Proc. IEEE ICC (virtual), May 2022.

• L. Xiang, L. Lei, S. Chatzinotas, B. Ottersten, and R. Schober, “Towards Powerefficient Aerial Communications via Dynamic Multi-UAV Cooperation”, in Proc. IEEE WCNC (virtual), Apr. 2020.

1.3 Sensing, Localization, and JSAC

• F. Pei, L. Xiang, and A. Klein, "Transmit Beamforming and Array Steering Optimization for UAV-Aided Bistatic ISAC", in Proc. IEEE Globecom, Cape Town, South Africa, Dec. 2024.

• B. Yilmaz, A. Klein, and L. Xiang, "Energy Minimization for UAV-Aided ISAC in A Cluttered Environment", in Proc. IEEE Globecom workshops, Cape Town, South Africa, Dec. 2024.

• B. Yilmaz, L. Xiang, and A. Klein, "Joint Beamforming and Trajectory Optimization for UAV-Enabled ISAC under a Finite Energy Budget", in Proc. IEEE ICC workshops, Denver, Colorado, Jun. 2024. 

• F. Pei, L. Xiang, and A. Klein, "Joint Optimization of Beamforming and 3D Array-Steering for UAV-Aided ISAC", in Proc. IEEE ICC, Denver, Colorado, Jun. 2024. 

• B. Yilmaz, L. Xiang, and A. Klein, "Joint Beamforming and Trajectory Optimization for UAV-Aided ISAC with Dipole Antenna Array", in Proc. IEEE WSA, Dresden, Germany, Mar. 2024.

• L. Xiang, M. Zhang, and A. Klein, “Robust Dynamic Trajectory Optimization for UAV-aided Localization of Ground Target”, in Proc. IEEE Globecom, Kuala Lumpur, Malaysia, Dec. 2023.

• Y. Wang, L. Xiang, and A. Klein, “Energy-Constrained UAV Trajectory Design for Sensing Information Maximization”, in Proc. IEEE Globecom workshops, Kuala Lumpur, Malaysia, Dec. 2023. 

Research Theme 2: Computing and Caching over Wireless

Modern wireless networks have witnessed an irreversible convergence of communication and computing/caching technologies, where a continuum of caching and computing resources are distributed between the mobile edge and cloud. Such converged wireless networks were one of the key factor for successful mobile video streaming in 4/5G wireless networks. They also provide the new information highway for enpowering artificial intelligence (AI)-enabled wireless networks in 6G. The overaching aim of this research theme is to enable advanced converged wireless networks through co-design of caching, computing, and (physical layer) communication schemes and co-optimization of their resources.  

Selected Papers

2.1 Cache-Aided Wireless: Offloading and Interference Cancellation

• L. Xiang, X. Wei, L. Cottatellucci, R. Schober, and T. Jiang, “Cache-Aided Massive MIMO with Linear Precoding in Multi-cell Systems”, arXiv:2204.04708, Apr. 2022.

• L. Xiang, D. W. K. Ng, R. Schober and V.W.S. Wong, “Physical Layer Security for Edge Caching Wireless Networks”, book chapter in Wireless Edge Caching: Modelling, Analysis, and Optimization, Eds. T. Vu, S. Chatizinotas, E. Bastug, and T. Q.S. Quek, Cambridge University Press, Oct. 2020.

• L. Xiang, D.W. K. Ng, X. Ge, Z. Ding, V.W. S.Wong, and R. Schober, “Cache-Aided Non-orthogonal Multiple Access: The Two-User Case”, IEEE Journal of Selected Topics in Signal Processing, vol. 13, no. 3, pp. 436–451, Jun. 2019.

• L. Xiang, D. W. K. Ng, R. Schober, and V. W. S. Wong, “Secure Video Streaming in Heterogeneous Small Cell Networks with Untrusted Cache Helpers”, IEEE Transactions on Wireless Communications, vol. 17, no. 4, pp. 2645–2661, Apr. 2018.

• L. Xiang, D. W. K. Ng, R. Schober, and V. W. S. Wong, “Cache-Enabled Physical Layer Security for Video Streaming in Backhaul-Limited Cellular Networks”, IEEE Transactions on Wireless Communications, vol. 17, no. 2, pp. 736–751, Feb. 2018.

• L. Xiang, D. W. K. Ng, T. Islam, R. Schober, V. W. S. Wong, and J. Wang, “Cross-Layer Optimization of Fast Video Delivery in Cache- and Buffer-Enabled Relaying Networks”, IEEE Transactions on Vehicular Technology, vol. 66, no. 12, pp. 11366–11382, Dec. 2017.

2.2 Optimization and Learning for Digital Twin

• Y. Wang, A. Klein, and L. Xiang, "Learning-Guided Matching Game for Decentralized Task Offloading to Multi-Functional UAVs", in Proc. IEEE ICC, Montreal, Canada, Jun. 2025.

• J. Liu, J. Zheng, J. Zhang, L. Xiang, D. W. K. Ng, and X. Ge, “Delay-aware Online Resource Allocation for Buffer-aided Synchronous Federated Learning over Wireless Networks”, in IEEE Access, vol. 12, pp. 164862-164877, 2024.

• S. Gan, K. Chen, J. Zhang, L. Xiang, D. W. K. Ng, and X. Ge, “Completion Time Minimization for Adaptive Semi-Asynchronous Federated Learning over Wireless Networks”, in Proc. IEEE PIMRC Workshops, Valencia, Spain, Sep. 2024.

• Y. Wang, M. Krantzik, L. Xiang, and A. Klein, "Joint Communication and Computing Optimization for Digital Twin Synchronization with Aerial Relay", in Proc. IEEE ICC, Denver, Colorado, Jun. 2024. 

Research Theme 3: Energy and Communication

Both communication and energy technologies are indispensible towarding building a sustainable and resilient world. The two fields are also interacting with each other: Communication technologies can enable mordernization of energy generation, transportation, distribution, and consumption to legacy power systems. Meanwhile, communication engineers are also looking for energy solutions that will be highly energy-efficient or battery-free.  This research theme explores these interacting topics, aiming to highlight the synergy in energy and communication researches. 

Selected Papers

3.1 Green Communications (Energy Efficiency Metric, Modeling, and Maximization)

• J. Zhang, L. Xiang, D. W. K. Ng, M. Chen, and M. Jo, “Energy Efficiency Evaluation of Multi-tier Cellular Uplink Transmission under Maximum Power Constraint”, IEEE Transactions on Wireless Communications, vol. 16, no. 11, pp. 7092–7107, Nov. 2017.

• D. W. K. Ng, L. Xiang, R. Schober, “Multi-objective Beamforming for Secure Communication in Systems with Wireless Information and Power Transfer”, in Proc. IEEE PIMRC, London, UK, pp. 7-12, Sep. 2013. 

• L. Xiang, X. Ge, C.-X. Wang, F.Y. Li, and F. Reichert, “Energy Efficiency Evaluation of Cellular Networks Based on Spatial Distributions of Traffic Load and Power Consumption”, IEEE Transactions on Wireless Communications, vol. 12, no. 3, pp. 961-973, 2013.

• L. Xiang, F. Pantisano, R. Verdone, X. Ge, and M. Chen, “Adaptive Traffic Load Balancing for Green Cellular Networks”, in Proc. IEEE PIMRC, Toronto, Canada, pp. 41-45, Sept. 2011.

• I. Humar, X. Ge, L. Xiang, M. Jo, and M. Chen, “Rethinking Energy-efficiency Models of Cellular Networks with Embodied Energy”, IEEE Network, vol. 25, no. 2, pp. 40-49, Mar.-Apr. 2011.

3.2 Smart Grid Communications (Renewable Energy Integration and Pricing)

• W. Lee, L. Xiang, R. Schober, and V. W. S. Wong, “Electric Vehicle Charging Stations With Renewable Power Generators: A Game Theoretical Analysis”, IEEE Transactions on Smart Grid, vol. 6, no. 2, pp. 608-617, Mar. 2015.

• W. Lee, L. Xiang, R. Schober, and V. W. S. Wong, “Direct Electricity Trading in Smart Grid: A Coalitional Game Analysis”, IEEE Journal on Selected Areas in Communications, vol. 32, no. 7, pp. 1398-1411, Jul. 2014.

• L. Xiang, D. W. K. Ng, W. Lee, and R. Schober, “Optimal Storage-aided Wind Generation Integration Considering Ramping Requirements”, in Proc. IEEE Smart-GridComm, Vancouver, Canada, pp. 1-6, Oct. 2013.

Lectures (Lehraufträge)

• Mobile Communications, TU Darmstadt, SS 2022, SS 2023, SS 2024, SS 2025

PhD Students

• Markus Krantzik, since Sep. 2024

• Fengcheng Pei, since Oct. 2023

• Yi Wang, since Aug. 2022

• Burak Yilmaz, Nov. 2020 - Mar. 2025

Guest PhD Students

• Xuzhong Zhang, Southeast University, since 2023

• Zipeng Li, Huazhong University of Science and Technology (HUST), graduated in 2021

• Xiao Wei, FAU and HUST, graduated in 2019

Bachelor and Master Students

• Xuhan Zhu, master's thesis on "Spectral- and Energy-Efficient Antenna Array Steering and Beamforming for UAV-Aided Communications", TU Darmstadt, Jun. 2024

• Tian Yu, bachelor's thesis on “Physics based Channel Modeling and Performance Analysis of Noisy-IRS Assisted Sensing and Communication”, TU Darmstadt, Oct. 2023

• Mengshuai Zhang, master's thesis on “Robust Dynamic Trajectory Optimization for UAV-aided Localization of Ground Target”, TU Darmstadt, Aug. 2023

• Fengcheng Pei, master's thesis on “Joint Optimization of Electrical and Mechanical Antenna Steering for UAV-assisted Sensing and Communication”, TU Darmstadt, Aug. 2023

• Raphael Drost, bachelor's thesis on “Map-assisted 3D Sensing and Communication Using UAV”, TU Darmstadt, Jul. 2023

• Yi Wang, master's thesis on “Completion Time Minimization for UAV-based Aerial Relaying with a Finite Buffer”, TU Darmstadt, Jul. 2022