The coded caching scheme proposed by Maddah-Ali and Niesen (MAN) is designed to reduce peak hours traffic by partially prefetching the files in end users' cache memory in low traffic hours and sending the requested files through multicast messages. This scheme was proved to be optimal under the constraint of uncoded prefetching and was originally proposed for a so-called single bottleneck link network. This dissertation goes beyond the unrealistic bottleneck network and extends the MAN scheme to a class of two-hop wireless networks consisting of one server connected via fronthaul links to a layer of H helper nodes, which in turn communicate via a wireless access network to K users. The proposed schemes in this work achieve full spatial scalability with an arbitrary number of users and the multicast rate does not vanish as the number of users in the network increase. This dissertation primarily focuses on interference management techniques. This work includes several network models with the first model in Chapters 2 and 3 embracing the path loss and channel gain, while in Chapter 4 orthogonal links (topological model) and interference collision model (protocol model) were considered. In the first model, users are able to use their multiple antennas to receive their requested multicast message through a fixed number of helpers with a non vanishing rate. Furthermore, a scalable video streaming service with two different qualities was implemented using the proposed delivery scheme, allowing users with better channel quality to decode a high quality version of the requested video file, which results in lower distortion levels. The routing scheme proposed in the final chapter delivers the multicast messages through the helpers with orthogonal channels to the receivers by formalizing a Linear Program (LP) which can be solved optimally in linear time in terms of the number of users in very large networks. Furthermore, a novel scheme that serves users as they become interference-free is proposed, which has a practical appeal since it could be implemented via the CSMA protocol. These approaches simultaneously solve many of the open practical problems identified as stumbling blocks for the application of coded caching in practical scenarios, namely: asynchronous streaming sessions, finite file size, subpacktization and high complexity of the MAN scheme, scalability of the scheme to large and spatially distributed networks, user mobility, and random activity (users joining and leaving the system at arbitrary times), decentralized prefetching of the cache contents.
Coded caching over realistic and scalable wireless networks
Codiertes Caching über realistische und skalierbare drahtlose Netzwerke
2020
Sonstige
Elektronische Ressource
Englisch
DDC: | 629 |