Chapter 1: The Caching Problem

Learning Objectives

• Frame the content-delivery problem as a shared-link capacity bottleneck between a server and K users
• Define the operating parameters: K users, N files, per-user cache size M, delivery rate R
• Analyze the classical popularity-based (uncoded) caching strategy and its cache-hit ratio
• Recognize the fundamental limitation of uncoded caching: rate scales as $K(1-M/N)$ regardless of what the users request
• Appreciate why the memory ratio $M/N$ (not the absolute cache size) is the right figure of merit
• Motivate coded caching as the right object of study by identifying the gap between popularity caching and what information theory allows