Data dissemination using instantly decodable binary codes in fog-radio access networks

This paper considers a device-to-device (D2D) fog-radio access network wherein a set of devices are required to store a set of files. The D2D devices are connected to a subset of the cloud data centers and thus possess a subset of the data. This paper is interested in reducing the total time of communication, i.e., the completion time, needed to disseminate all files among the devices using instantly decodable network coding (IDNC). Unlike previous studies that assume a fully connected communication network, this paper tackles the more realistic scenario of a partially connected network in which devices can only target devices in their transmission range. The joint optimization of selecting the transmitting device(s) and the file combination(s) is first formulated and its intractability exhibited. The completion time is approximated using the celebrated decoding delay approach by deriving the relationship between the quantities in a partially connected network. The paper introduces the cooperation graph and demonstrates that under the collision-free transmissions assumption, the problem is equivalent to a maximum weight clique problem over the newly designed graph. Extensive simulations reveal that the proposed solution provides noticeable performance enhancement and outperforms previously proposed IDNC-based schemes.