Linear Network Coded Wireless Caching

This paper studies a K×M multiple-input multiple-output (MIMO) wireless caching that consists of a library, K base stations (BSs), and M users, where each BS and user are equipped with N_T and N_R antennas respectively. Consider that each BS has a local cache that can prefetch some popular data requested by users from the library. We propose a linear network coding (NC) assisted wireless caching, considering the finite cache size and the variability of the user requests. In the cache placement phase, we design a joint NC caching function at K BSs to store linear combinations of messages from the library. In the content delivery phase, each user can successfully decode its requested messages by the receiver shaping and reverse NC operation. Our analytical results verify that, without any shared caching messages at different BSs, the proposed caching scheme is compatible with distinct user requests. In particular, for a 2 × 2 MIMO wireless caching network, the proposed caching scheme can achieve a higher total degree of freedom (DoF) of min(2N_T, 2N_R) - 1 while consuming a smaller cache size, compared with the existing caching scheme.