Fundamental Limits of Cache-Aided Private Information Retrieval With Unknown and Uncoded Prefetching

We consider the problem of private information retrieval (PIR) from N non-colluding and replicated databases when the user is equipped with a cache that holds an uncoded fraction r from each of the K stored messages in the databases. We assume that the databases are unaware of the cache content. We investigate D*(r) the optimal download cost normalized with the message size as a function of K, N, ...