Degrees of freedom of the cache-aided multi-hop line network

Abstract

In this paper, we study the degrees of freedom (DoF) characterization of cache-aided 8-user multi-hop line network. The leftmost user 1 wishes to send messages to the remaining users and the messages are relayed by user 2, 3,..., 7. Each user is equipped with a local cache and we assume that the messages received by user k can also be cached. Thus, interference signals from the messages transmitted by user k + 1, k + 2, ... and 8 can be eliminated since user k has already cached the contents of messages in previous data transmission. With this cache-aided scheme, the multi-hop topology can be transformed into a special partially connected interference channel (IC). Then we derived the DoF outer bound of the network information-theoretically. To deal with the challenge of this partial connected IC model, where the number of interferences increases with the index k , we proposed a DoF outbound achievable transmission method by assigning equidifferent signal space allocation.