50 research outputs found
Centralized Coded Caching with User Cooperation
In this paper, we consider the coded-caching broadcast network with user
cooperation, where a server connects with multiple users and the users can
cooperate with each other through a cooperation network. We propose a
centralized coded caching scheme based on a new deterministic placement
strategy and a parallel delivery strategy. It is shown that the new scheme
optimally allocate the communication loads on the server and users, obtaining
cooperation gain and parallel gain that greatly reduces the transmission delay.
Furthermore, we show that the number of users who parallelly send information
should decrease when the users' caching size increases. In other words, letting
more users parallelly send information could be harmful. Finally, we derive a
constant multiplicative gap between the lower bound and upper bound on the
transmission delay, which proves that our scheme is order optimal.Comment: 9 pages, submitted to ITW201
Demand-Private Coded Caching and the Exact Trade-off for N=K=2
The distributed coded caching problem has been studied extensively in the
recent past. While the known coded caching schemes achieve an improved
transmission rate, they violate the privacy of the users since in these schemes
the demand of one user is revealed to others in the delivery phase. In this
paper, we consider the coded caching problem under the constraint that the
demands of the other users remain information theoretically secret from each
user. We first show that the memory-rate pair is
achievable under information theoretic demand privacy, while using broadcast
transmissions. We then show that a demand-private scheme for files and
users can be obtained from a non-private scheme that satisfies only a
restricted subset of demands of users for files. We then focus on the
demand-private coded caching problem for users, files. We
characterize the exact memory-rate trade-off for this case. To show the
achievability, we use our first result to construct a demand-private scheme
from a non-private scheme satisfying a restricted demand subset that is known
from an earlier work by Tian. Further, by giving a converse based on the extra
requirement of privacy, we show that the obtained achievable region is the
exact memory-rate trade-off.Comment: 8 pages, 2 figure