Departmental Papers (CIS)

Date of this Version

June 2000

Document Type

Journal Article


Postprint version. Published in Journal of Computer and System Sciences, Volume 60, Issue 3, 2000, pages 575-591.
Publisher URL:

NOTE: At the time of publication, author Sanjeev Khanna was affiliated with Bell Laboratories. Currently (August 2005), he is a faculty member in the Department of Computer and Information Science at the University of Pennsylvania.


We consider the problem of efficient information retrieval in asymmetric communication environments where multiple clients with limited resources retrieve information from a powerful server who periodically broadcasts its information repository over a communication medium. The cost of a retrieving client consists of two components: (a) access time, defined as the total amount of time spent by a client in retrieving the information of interest; and (b) tuning time, defined as the time spent by the client in actively listening to the communication medium, measuring a certain efficiency in resource usage. A probability distribution is associated with the data items in the broadcast representing the likelihood of a data item's being requested at any point of time. The problem of indexed data broadcast is to schedule the data items interleaved with certain indexing information in the broadcast so as to minimize simultaneously the mean access time and the mean tuning time.

Prior work on this problem thus far has focused only on some special cases. In this paper we study the indexed data broadcast problem in its full generality and design a broadcast scheme that achieves a mean access time oef at most (1.5 + ε) times the optimal and a mean tuning time bounded by O(log n).



Date Posted: 15 August 2005

This document has been peer reviewed.