Coded Caching Low Subpacketization Schemes and Improved Secretive Schemes

Abstract

Next generation wireless networks present the challenges of serving clients via channels which are not traditional point-to-point communication channels. The technique of utilizing local storage on the client s device, for aiding communication services on a broadcast channel was introduced formally in the landmark paper by Ali-Niesen, under the title of Coded Caching. The state of the art coded caching schemes require that the files at the server be divisible into a large number of parts (this number is called subpacketization). In fact, most schemes require the subpacketization which is exponential in the number of users K. On the other extreme, few schemes having subpacketization linear in K are known; however they require extremely large number of users to exist, or they offer only little gain in rate. Because of these reasons the state of the art coded caching schemes are impractical for applications, eventhough they are theoretically sound. The first objective of this thesis is to propose a new coded caching scheme with low subpacketization utilizing projective geometry which achieve subexponential subpacketization, with small cache requirement. A special case of our proposed scheme, gives a new linear subpacketization scheme. Extending our techniques, we also obtain low subpacketization schemes for D2D communications and distributed computing. We show numerical comparisons of our scheme with state-of-the-art schemes, and see that our schemes achieve lower and practically relevant levels of subpacketization in many situations at the cost of higher rate. In non-secretive coded caching, it was shown in the literature that commonality among the user demands help in reducing the rate of communication. The direct adaptation of this result to secretive coded caching is not possible because of the presence of an unique key in each transmission. The second objective of this thesis is to propose an improved perfect secretive coded caching scheme by exploiting commonality among the user demands. newline