9 research outputs found
Improved memory-rate trade-off for caching with demand privacy
We consider the demand-private coded caching problem in a noiseless broadcast network. It is known from past works that a demand-private scheme for N files and K users can be obtained from a non-private scheme for N files and NK users. We first propose a scheme that improves on this idea by removing some redundant transmissions. The memory- rate trade-off achieved using this scheme is shown to be within a multiplicative factor of 3 from the optimal for all the memory regimes when K K = 2.J. Ravi has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant No. 714161). The work of B. K. Dey was supported in part by the Bharti Centre for Communication in IIT Bombay. The work of N. Karamchandani is supported in part by a Science and Engineering Research Board (SERB) grant on "Content Caching and Delivery over Wireless Networks"
On the Rate-Memory Tradeoff of D2D Coded Caching with Three Users
The device-to-device (D2D) centralized coded caching problem is studied for
the three-user scenario, where two models are considered. One is the 3-user D2D
coded caching model proposed by Ji et al, and the other is a simpler model
named the 3-user D2D coded caching with two random requesters and one sender
(2RR1S), proposed in this paper, where in the delivery phase, any two of the
three users will make file requests, and the user that does not make any file
request is the designated sender. We allow for coded cache placement and none
one-shot delivery schemes. We first find the optimal caching and delivery
schemes for the model of the 3-user D2D coded caching with 2RR1S for any number
of files. Next, we propose a new caching and delivery scheme for the 3-user D2D
coded caching problem using the optimal scheme of the 3-user D2D coded caching
with 2RR1S as a base scheme. The new caching and delivery scheme proposed
employs coded cache placement and when the number of files is equal to 2 and
the cache size is medium, it outperforms existing schemes which focus on
uncoded cache placement. We further characterize the optimal rate-memory
tradeoff for the 3-user D2D coded caching problem when the number of files is
equal to 2. As a result, we show that the new caching and delivery scheme
proposed is in fact optimal when the cache size is in the medium range.Comment: To be submitted for possible journal publicatio
Fundamental Limits of Device-to-Device Private Caching with a Trusted Server under Uncoded Cache Placement and User Collusion
In the coded caching problem, as originally formulated by Maddah-Ali and
Niesen, a server communicates via a noiseless broadcast link to multiple users
that have local storage capability. In order for a user to decode the desired
file from the coded multicast transmission, the demands of all the users must
be globally known, which may violate the privacy of the users. To overcome this
privacy problem, Wan and Caire recently proposed several schemes that attain
coded multicasting gain while simultaneously guarantee information theoretic
privacy of the users' demands. In Device-to-Device (D2D) networks, the demand
privacy problem is further exacerbated by the fact that each user is also a
transmitter, which should know the files demanded by the remaining users in
order to form its coded multicast transmissions. This paper solves this
seemingly infeasible problem with the aid of a trusted server. Specifically,
during the delivery phase, the trusted server collects the users' demands and
sends a query to each user, who then broadcasts coded multicast packets
according to this query. The main contribution of this paper is the development
of novel achievable schemes and converse bounds for D2D private caching with a
trusted server, where users may be colluding (i.e., when some users share
cached content and demanded file indices), that are to within a constant factor
of one another.Comment: 64 pages, 6 figures, under review of TIT, parts of results were
presented in ICC 2020 and ISIT 202