PhD Defence by Radoslaw Kotaba


12.05.2022 kl. 15.00 - 18.00


Radio Access for Ultra-Reliable Communication in 5G Systems and Beyond

Ultra-reliable low-latency communication (URLLC) and massive machine-type communication (mMTC) are two flagship use cases of the fifth generation (5G) cellular networks. Yet, designing efficient communication schemes that would enable those services is challenging due to their respective requirements. This is especially true in the uplink, which in normal circumstances needs to be fully coordinated by the base station and requires more auxiliary procedures than downlink. Such procedures might not always be feasible due to the latency involved (URLLC) and prohibitively high overhead (mMTC).

This thesis proposes several novel access techniques addressing the challenges of the aforementioned use cases. The primary focus is on developing new diversity schemes for URLLC, that jointly optimize the traffic of many users. Two variants are investigated -- grant-free access without feedback and scheduled access with feedback and retransmissions. To address the shortcomings of the current state-of-the-art grant-free schemes, this thesis proposes the usage of specifically designed access patterns, which allow to introduce certain amount of coordination and thus provide reliability guarantees. For the scheduled access, a novel technique is proposed that leverages non-orthogonal multiple access (NOMA), advanced receiver processing and power optimization to achieve highly reliable and efficient communication. Lastly, the problem of reliable massive access is tackled by considering an optimized feedback scheme which jointly encodes the acknowledgements of all active users. Additionally, a method to introduce identification and authentication capabilities to the existing concept of unsourced random access is proposed.

Assessment Committee
Professor Mads Græsbøll Christensen, Aalborg University, Denmark (chairman)
Professor Gustavo de Veciana, University of Texas, The USA
Principal Research Scientist Jakob Hoydis, NVIDIA, France

Professor Petar Popovski, Aalborg University, Denmark

Associate Professor Carles Navarro Manchón, Aalborg University, Denmark

Associate Professor Ming Shen, Aalborg University, Denmark

How to participate
The PhD defence will be carried out in hybrid format, meaning you can join on location or online via this link, meeting ID 129 623 374 4


Free of charge


Connectivity Section, Department of Electronic Systems


Aalborg University, Fredrik Bajers Vej 7, room A1-103 - or online via TEAMS


See the list