Fundamental limits of latency in a cache-aided 4×4 interference channel

Fundamental limits of communication is studied in a 4 × 4 interference network, in which the transmitters are equipped with cache memories. Each of the receivers requests one file from a library of N equal-size files. The caches at the transmitters are filled without the knowledge of the user demands, such that all possible demand combinations can be satisfied reliably over the interference channel. The achievable normalized delivery time (NDT) is studied under centralized cache placement. By combining the interference alignment (IA) and zero-forcing (ZF) techniques, a novel caching and transmission scheme is presented, and is shown to be optimal for all possible cache sizes; fully characterizing the NDT for the 4× 4 interference network with caches at the transmitter side.