Ultra-Reliable Low-Latency Communications
: Fundamental Limits

  • Ioannis Papoutsidakis

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


Numerous institutions and companies have embarked on the global deployment of the 5th generation of cellular networks (5G) in recent years while simultaneously initiating discussions about the next generation (6G). During this time, telecommunication providers have primarily focused on the Enhanced Mobile Broadband (eMBB) out of the three designated service classes of 5G. As a result, only eMBB is implemented and ready to be used. This shortcoming has highlighted the need for future wireless networks that must be innovative and at the same time cover the weaknesses of previous generations.

This work specifically focuses on the Ultra-Reliable Low-Latency Communications (URLLC) service class, which could serve as a bridge between 5G and 6G research. It examines the fundamental trade-off between rate, reliability, and latency in the context of finite blocklength channel coding. The study delves into the blocklength of various coding schemes, as it plays a crucial role in communication latency. Specifically, it is the main component of transmission, queueing, and processing delays in a communication network. The analysis of these trade-offs is conducted via the derivation of novel converse and achievability bounds.

The non-asymptotic achievable rates of fixed blocklength codes are investigated, as well as the impact of variable-length coding with stop-feedback across various important channels. These coding schemes are put to test in network settings, taking into account relaying and queueing delays. Additionally, the influence of latency on the Age of Incorrect Information metric is studied for symmetric Markov sources.
Date of Award23 Jan 2024
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorAngela Doufexi (Supervisor) & Robert J Piechocki (Supervisor)

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