Chapter 32: URLLC, mMTC, and Emerging Traffic Types

Learning Objectives

• Derive the Polyanskiy-Poor-Verdu normal approximation for the maximum coding rate at finite blocklength, interpret channel dispersion as a penalty for short codes, and quantify the gap to Shannon capacity as a function of blocklength and error probability
• Analyse URLLC reliability requirements in terms of outage probability and diversity order, design mini-slot structures that meet latency constraints, and evaluate the diversity-multiplexing-latency trade-off under finite blocklength
• Formulate grant-free random access for mMTC, model device activity detection as a compressed sensing problem, and analyse the scaling laws that relate the number of active devices, pilot length, and detection probability
• Define the Age of Information metric, derive closed-form AoI expressions for M/M/1, M/D/1, and D/M/1 queues, determine the optimal update rate that minimises average AoI, and distinguish freshness from throughput
• Explain the unsourced random access paradigm, state the per-user probability of error achievability bound, and compare coded compressed sensing schemes against the random coding achievability bound
• Synthesise the interplay between latency, reliability, throughput, and freshness to reason about cross-layer design trade-offs in 5G NR and beyond-5G networks