Unsourced random access
How can many wireless devices share a channel with little coordination while communicating reliably?
Personal homepage
Building better ways
to communicate.
I am Alexander Fengler, an Emmy-Noether Research Group Leader at Karlsruhe Institute of Technology. My work connects information theory, statistical signal processing and wireless communications.
Research areas
Questions that guide my work
Activity detection & sparse recovery
Recover active users and their signals from noisy, high-dimensional measurements.
Information-theoretic limits
Characterize the fundamental limits of communication and design practical methods that approach them.
Massive MIMO
Study channel estimation, pilot-based access, interference cancellation and power control for large antenna arrays.
Sparse regression codes
Use structured codes and iterative decoding for efficient unsourced multiple access.
Approximate message passing
Develop efficient inference algorithms for large-scale statistical signal processing problems.
Background
Where I have worked
2024 — nowKarlsruhe, DE
Emmy-Noether Research Group Leader
Karlsruhe Institute of Technology (KIT)
2024 — 2025Oberpfaffenhofen, DE
Postdoctoral Research Fellow
German Aerospace Center (DLR)
2022 — 2024Cambridge, MA
Postdoctoral Research Fellow · Walter Benjamin Fellow
Laboratory for Information and Decision Systems, MIT
2016 — 2021Berlin, DE
PhD, Communications Engineering
Technische Universität Berlin
Selected work
Publications
Journal articles
2022
2021
2019
Conference papers
2025
Removal of small weight stopping sets for asynchronous unsourced multiple access
2025 IEEE International Symposium on Information Theory (ISIT), 1–6
2023
2023
On the advantages of asynchrony in the unsourced MAC
2023 IEEE International Symposium on Information Theory (ISIT), 2523–2528
2022
Sparse graph codes for the 2-user unsourced MAC
2022 56th Asilomar Conference on Signals, Systems, and Computers, 682–686
2022
Finite-blocklength results for the A-channel: Applications to unsourced random access and group testing
2022 58th Annual Allerton Conference on Communication, Control, and Computing, 1–8
2021
Pilot-based unsourced random access with a massive MIMO receiver in the quasi-static fading regime
2021 IEEE 22nd International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 356–360
2020
2019
2019
Preprints
2026
An orthogonal approximate message passing framework for multiuser communications
arXiv:2606.26777
2025
2019
2019
2020
Pilot-based unsourced random access with a massive MIMO receiver, MRC and polar codes
arXiv:2012.03277
Thesis
2021
Sparse recovery based grant-free random access for massive machine-type communication
PhD thesis, Technische Universität Berlin