Performance Limits of Coded Caching on Two Layers Networks Under Uncoded Placement
Liwen Liu, Kai Huang, Jinbei Zhang, Kechao Cai, Jiangwei Sui · 2024
Coded caching is a novel technique to reduce network traffic by exploiting multicast opportunities over users. Practical networks may have two layers of caches, where the central server is first connected to an internal node called a “mirror” (e.g., a base station or wifi router) and this internal node links to end users through a broadcast channel. Previous work [1] shows that there exists a tension between rates in these two layers, and the optimal tradeoff is obtained in a simplified model with one mirror and two users. In this paper, we further consider a more general setting with one mirror and multiple users. The performance limits of coded caching on two-layer networks are obtained under uncoded placement. For converse bounds, it is shown that a linear combination of the worst-case rates in each layer is not less than a threshold. An optimal achievable scheme is designed accordingly to match the novel converse bounds.