Lin Xiang (向林)

I am currently a research group leader at the Communications Engineering Lab headed by Prof. Anja Klein, and an Atheme Young Investigator of TU Darmstadt. I obtained my Ph.D. in Electrical, Electronic, and Information Engineering from the Friedrich-Alexander-University of Erlangen-Nuremberg in Germany, advised by Prof. Robert Schober. 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, advised by Prof. Björn Ottersten, and a visiting researcher at the University of Bologna, advised by Prof. Roberto Verdone (and 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

• Dec. 2023, the second phase of emergenCITY was accepted for funding 

• Jul. 2023, lecture "Mobile Communications" in SS 2023 received very positive evaluation

Research Interest

My research interests lie in communication theory / wireless communications, including 

• Multiple-input multiple-output (MIMO) and massive MIMO, 

• Orthogonal and non-orthogonal multiple-access, 

• Cooperative communication, 

• Physical layer security (PLS), and 

• Large-scale wireless networks,

optimization / learning theory, including 

• Convex and nonconvex optimization, 

• Deterministic, stochastic, and robust optimization, 

• Exact and approximate dynamic programming, and 

• Machine learning and reinforcement learning,  

as well as their applications in emerging technologies, including 

• Digital twin,

• Integrated sensing and communication (ISAC),

• Unmanned aerial vehicles (UAVs),

• Vehicle-to-everything (V2X),

• Caching and mobile video streaming, and

• Smart Grid.

Research Theme 1: Motion and Sensing/Localization/Communication in 6G

Cyber-physical systems (CPSs) such as robots, UAVs, and ground vehicles are usually capable of controllable/programmable motion in space and over time. This differs significantly from conventional wireless information systems, where relative movements between transmitters and receivers are unpredictable, rarely exploitable, and even detrimental to information sensing/localization/communication/processing (SLCP). This topic aims to bridge the two worlds of CPSs and SLCP. In particular, we consider how to exploit motion (including translation, rotation, transformation, swarming etc.) in space and over time to facilitate tailored design and optimization of information SLCP for and by movable CPSs.  We also consider how to best tradeoff between the complexity and overhead incurred in motion control and the achieved SLCP performances, particularly in complex environments. 

Selected Papers

UAV-Aided Sensing / Localization / ISAC

• 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. 

Nonterresterial Wirelss Communication Networks

• 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.

Large-Scale V2X Networks

• 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.

• 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.

Research Theme 2: Computing / Caching and Communication

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-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

Optimization and Learning for Digital Twin

• 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. 

Cache-Aided Wireless (MIMO / NOMA / Relaying / PLS)

• 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.

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

Smart Grid (Renewable Energy Integration / Pricing)

• W. Lee, L. Xiang, R. Schober, and V. W. S. Wong, “Electric Vehicle Charging StationsWith 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.

Green Communications (Energy Efficiency Metric, Modeling, and Maximization / Large-Scale Wireless Networks)

• 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, Sep. 2022.

• 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.

Lectures (Lehraufträge)

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

PhD Students

• Fengcheng Pei (Co-supervised with Prof. Anja Klein), since Oct. 2023

• Yi Wang (Co-supervised with Prof. Anja Klein), since Aug. 2022

• Burak Yilmaz (Co-supervised with Prof. Anja Klein), since Nov. 2020

Former PhD Students

• Zipeng Li

• Xiao Wei

Bachelor and Master Students

• 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.