Abstract:

An information-aware hierarchical weighted interference cancellation coded caching scheme is proposed for multiple relay systems to eliminate the interference of unrequested subfiles and improve the degrees-of-freedom of the system. The proposed scheme divides the system into subsystems  I and II  to minimize link load and improve the degrees-of-freedom according to the cache capacities of the user and relays, and the number of users and files by jointly designing weighted interference cancellation, orthogonal unicast scheme, and decentralized coded caching scheme. In subsystem I, when subfiles are more than users in the single interference-free transmission, the unicast is introduced to achieve additional degrees-of-freedom compared to the traditional interference cancellation. In subsystem II , the multi-relay cooperative coded transmission is proposed to reduce massive steps of the delivery and improve the system degrees-of-freedom. Simulation results show that when the number of subfiles is less than that of users in a single interference-free transmission, the system degrees-of-freedom obtained by the proposed scheme is better than that of the traditional orthogonal unicast scheme, and can achieve more than 1.3 times system degrees-of-freedom gains. In addition, it also achieves about 10.6% degrees-of-freedom gains compared with that of the traditional interference cancellation scheme.

Key words: coded caching, physical layer network coding, multi-relay system, interference cancellation