Campus Units

Electrical and Computer Engineering

Document Type

Conference Proceeding


2015 IEEE International Symposium on Information Theory (ISIT)

Publication Version

Accepted Manuscript

Link to Published Version

Publication Date


Journal or Book Title

2015 IEEE International Symposium on Information Theory (ISIT)

First Page


Last Page




Conference Title

2015 IEEE International Symposium on Information Theory (ISIT)

Conference Date

June 14-19, 2015


Hong Kong, China


Content delivery networks often employ caching to reduce transmission rates from the central server to the end users. Recently, the technique of coded caching was introduced whereby coding in the caches and coded transmission signals from the central server are considered. Prior results in this area demonstrate that carefully designing the placement of content in the caches and designing appropriate coded delivery signals from the server allow for a system where the delivery rates can be significantly smaller than conventional schemes. However, matching upper and lower bounds on the transmission rate have not yet been obtained. In this work, we derive tighter lower bounds on the coded caching rate than were known previously. We demonstrate that this problem can equivalently be posed as a combinatorial problem of optimally labeling the leaves of a directed tree. Our proposed labeling algorithm allows for significantly improved lower bounds on the coded caching rate. Furthermore, we study certain structural properties of our algorithm that allow us to analytically quantify improvements on the rate lower bound for general values of the problem parameters. This allows us to obtain a multiplicative gap of at most four between the achievable rate and our lower bound.


This is a manuscript of a proceeding from the IEEE International Symposium on Information Theory (2015): 1696, doi: 10.1109/ISIT.2015.7282745. Posted with permission.


Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

Copyright Owner




File Format


Published Version


Article Location