Caching with Partial Adaptive Matching

We study the caching problem when we are allowed to match each user to one of a subset of caches after its request is revealed. We focus on non-uniformly popular content, specifically when the file popularities obey a Zipf distribution. We study two extremal schemes, one focusing on coded server transmissions while ignoring matching capabilities, and the other focusing on adaptive matching while ignoring potential coding opportunities. We derive the rates achieved by these schemes and characterize the regimes in which one outperforms the other. We also compare them to information-theoretic outer bounds, and finally propose a hybrid scheme that generalizes ideas from the two schemes and performs at least as well as either of them in most memory regimes.Comment: 35 pages, 7 figures. Shorter versions have appeared in IEEE ISIT 2017 and IEEE ITW 201

Uncoded Caching and Cross-level Coded Delivery for Non-uniform File Popularity

Proactive content caching at user devices and coded delivery is studied considering a non-uniform file popularity distribution. A novel centralized uncoded caching and coded delivery scheme, which can be applied to large file libraries, is proposed. The proposed cross-level coded delivery (CLCD) scheme is shown to achieve a lower average delivery rate than the state of art. In the proposed CLCD scheme, the same subpacketization is used for all the files in the library in order to prevent additional zero-padding in the delivery phase, and unlike the existing schemes in the literature, two users requesting files from different popularity groups can be served by the same multicast message in order to reduce the delivery rate. Simulation results indicate significant reduction in the average delivery rate for typical Zipf distribution parameter values.Comment: A shorter version of this paper has been presented at IEEE International Conference on Communications (ICC) 201

Multi-access Coded Caching with Decentralized Prefetching

An extension of coded caching referred to as multi-access coded caching where each user can access multiple caches and each cache can serve multiple users is considered in this paper. Most of the literature in multi-access coded caching focuses on cyclic wrap-around cache access where each user is allowed to access an exclusive set of consecutive caches only. In this paper, a more general framework of multi-access caching problem is considered in which each user is allowed to randomly connect to a specific number of caches and multiple users can access the same set of caches. For the proposed system model considering decentralized prefetching, a new delivery scheme is proposed and an expression for per user delivery rate is obtained. A lower bound on the delivery rate is derived using techniques from index coding. The proposed scheme is shown to be optimal among all the linear schemes under certain conditions. An improved delivery rate and a lower bound for the decentralized multi-access coded caching scheme with cyclic wrap-around cache access can be obtained as a special case. By giving specific values to certain parameters, the results of decentralized shared caching scheme and of conventional decentralized caching scheme can be recovered.Comment: 26 pages, 6 figures, 6 tables, Submitted to IEEE Transactions on Communication