Cache-Aided Private Information Retrieval with Partially Known Uncoded Prefetching: Fundamental Limits

12/18/2017
by   Yi-Peng Wei, et al.
0

We consider the problem of private information retrieval (PIR) from N non-colluding and replicated databases, when the user is equipped with a cache that holds an uncoded fraction r of the symbols from each of the K stored messages in the databases. This model operates in a two-phase scheme, namely, the prefetching phase where the user acquires side information and the retrieval phase where the user privately downloads the desired message. In the prefetching phase, the user receives r/N uncoded fraction of each message from the nth database. This side information is known only to the nth database and unknown to the remaining databases, i.e., the user possesses partially known side information. We investigate the optimal normalized download cost D^*(r) in the retrieval phase as a function of K, N, r. We develop lower and upper bounds for the optimal download cost. The bounds match in general for the cases of very low caching ratio (r ≤1/N^K-1) and very high caching ratio (r ≥K-2/N^2-3N+KN). We fully characterize the optimal download cost caching ratio tradeoff for K=3. For general K, N, and r, we show that the largest gap between the achievability and the converse bounds is 5/32.

READ FULL TEXT

page 1

page 2

page 3

page 4

research
06/04/2018

The Capacity of Private Information Retrieval with Private Side Information Under Storage Constraints

We consider the problem of private information retrieval (PIR) of a sing...
research
10/13/2020

On the Fundamental Limits of Cache-aided Multiuser Private Information Retrieval

We consider the problem of cache-aided Multiuser Private Information Ret...
research
08/29/2019

Improved Storage for Efficient Private Information Retrieval

We consider the problem of private information retrieval from Nstorage-c...
research
11/27/2018

The Capacity of Private Information Retrieval from Decentralized Uncoded Caching Databases

We consider the private information retrieval (PIR) problem from decentr...
research
02/25/2021

Download Cost of Private Updating

We consider the problem of privately updating a message out of K message...
research
02/02/2021

A New Design of Cache-aided Multiuser Private Information Retrieval with Uncoded Prefetching

In the problem of cache-aided multiuser private information retrieval (M...
research
01/09/2018

Asymmetry Hurts: Private Information Retrieval Under Asymmetric Traffic Constraints

We consider the classical setting of private information retrieval (PIR)...

Please sign up or login with your details

Forgot password? Click here to reset