Devicetodevice content caching techniques in 5G: A taxonomy, solutions, and challenges Abstract   Over the past many years, content caching is one of the major challenges in the 5G environment. With the advent of the Internet of Things (IoT) and 5G, users want to access various services within a fraction of seconds resulting an extra burden on the underlying network infrastructure to maintain Quality of Service (QoS) and Quality of Experience (QoE) provisions of different applications for the endusers and service providers. However, caching the most popular contents followed by devicetodevice (D2D) sharing can resolve the aforementioned problems. But, access delay is still one of the challenges in front of the research community during content caching using D2D communications in a 5G environment. Motivated from these facts, this paper provides an indepth survey of various D2D based content caching techniques used for popular content sharing among different devices in the 5G environment. A detailed taxonomy is presented to give deep insights to the readers about the findings, constraints, and challenges of various existing proposals. Finally, a relative comparison of the existing D2D content caching proposals is given in the text with respect to various parameters. It gives deep insights to the readers about the applicability of different caching techniques in 5G.

TwoStage Interference Cancellation for DevicetoDevice Caching Networks Wireless devicetodevice (D2D) caching networks are studied, in which n nodes are distributed uniformly at random over the network area. Each node caches M files from the library of size     m xe2x89xa5 M     and independently requires a file from the library. Each request will be served by cooperative D2D transmission from other nodes having the requested file in their cache memories. In many practical sensor or Internet of things (IoT) networks, there may exist simple sensor or IoT devices that are not able to perform realtime rate and power control based on the reported channel quality information (CQI). Hence, it is assumed that each node transmits a file with a fixed rate and power so that an outage is inevitable. To improve the outagebased throughput, a cacheenabled interference cancellation (IC) technique is proposed for cooperative D2D file delivery which first performs IC, utilizing cached files at each node as side information, and then performs successive IC of strongly interfering files. Numerical simulations demonstrate that the proposed scheme significantly improves the overall throughput and, furthermore, such gain is universally achievable for various caching placement strategies such as random caching and probabilistic caching.