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Caching Policies under Content Freshness Constraints

August 13 @ 3:00 pm - 4:00 pm

Date: 13th August, 2018

Time:  3:00 pm

Venue:  Malaviya Hall

Speaker: Pawan Poojary (EE15S025)

Guide: Dr. Krishna Jagannathan

Abstract

Several real-time delay-sensitive applications pose varying degrees of freshness demands on the requested contents. The performance of cache replacement policies that are agnostic to these demands is likely to be sub-optimal. Motivated by this concern, in this work, we study caching policies under a request arrival process which incorporates user freshness demands. We consider the steady-state cache hit probability to be the performance metric. We first provide a universal upper bound on the performance of any caching policy to capture the effect of two factors limiting the cache performance, namely, the finiteness of the cache and the user freshness constraints. We then analytically obtain the content-wise hit-rates for the Least Popular (LP) policy and provide sufficient conditions for the asymptotic optimality of cache performance under this policy. Next, we obtain an accurate approximation for the LRU content-wise hit-rates under Zipf distributed requests in the regime of large content population. To this end, we map the characteristic time of a content in the LRU policy to the classical Coupon Collector’s Problem and show that it sharply concentrates around its mean. Further, we develop modified versions of these policies which eject cache redundancies present in the form of stale contents. Finally, we propose a new policy which outperforms the above policies by explicitly using freshness specifications of user requests to prioritize among the cached contents. We corroborate our analytical insights with extensive simulations.

All are cordially invited

Details

Date:
August 13
Time:
3:00 pm - 4:00 pm
Event Category:
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