Cache-Aided Retrospective Interference Alignment in SISO X Wireless Networks

In this paper, one class of single-input single-output (SISO) X networks with cache at both transmitters and receivers is considered. Specifically, the X networks consist of two transmitters and K receivers. Furthermore, only the delayed channel state information at transmitters (CSIT) is available. In order to improve degrees of freedoms (DoF) of the system, we propose a cache-aided retrospective interference alignment (RIA) scheme which contains the Prefetching Phase and the Delivery Phase. In the Prefetching Phase, we carefully choose the contents to be cached at both transmitters and receivers. In the Delivery Phase, we propose a cache-aided RIA transmission scheme where order-μ symbols are delivered and the cached contents are exploited to cancel interference. Moreover, when μ = K - 1, it is reduced to a blind scheme, which does not need the CSIT. Furthermore, we present one theorem to characterize the sum DoF of the proposed cache-aided RIA scheme. It is shown that the proposed cache-aided scheme outperforms the RIA scheme without cache and the cache-aided interference management scheme for the system configuration considered in this paper.