Abstract
Next generation wireless networks (5G and beyond) present the challenges of serving clients via channels which are not traditional point-to-point communication channels.The study of efficient high throughput communication techniques for broadcast channels, interference channels, multiple access channels, device-to-device (D2D) communication, all obtain relevance in the present wireless communication scenario. The technique of utilizing local storage (which has become quite affordable, thanks to advances in hardware design), either on the client’s device or in a nearby location, for aiding communication services on a broadcast channel was introduced formally in the landmark paper by Ali-Niesen, under the title of Coded Caching. In this paper, it was shown that a combination of (a) carefully utilizing the local storage or cache available to individual clients, and (b)coded transmissions during the delivery phase, brings tremendous gains in the rate of delivery of information of a broadcast channel.
The first objective of this thesis is to propose a new coded caching scheme with low subpacketization and moderate rate gains utilizing projective geometries over finite fields. The proposed scheme achieve the asymptotic subpacketization, which is subexponential in K or exponential in O((log K)^2) (thus improving on the root-of-K exponent) and has a small cache requirement. As a special case of our proposed scheme, we get anew linear subpacketization scheme, which has a more flexible range of parameters than existing linear subpacketization schemes. Extending our techniques, we also obtain low subpacketization schemes for other multi-receiver settings such as D2D communications and distributed computing. We show numerical comparisons of our scheme with existing popular and 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 (or equivalently, a lesser caching gain).
In another line of work, secretive coded caching was proposed in the literature, where the cache content and the transmissions are required to be such that each user can decode only the requested file by that user, and no information about other files. 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 (reduced rate) perfect secretive coded caching scheme by exploiting commonality among the user demands.