4,705 research outputs found
Multi-Antenna Coded Caching for Multi-Access Networks with Cyclic Wrap-Around
This work explores a multiple transmit antenna setting in a multi-access
coded caching (MACC) network where each user accesses more than one cache. A
MACC network has users and caches, and each user has access to
consecutive caches in a cyclic wrap-around manner. There are antennas at
the server, and each cache has a normalized size of . The cyclic
wrap-around MACC network with a single antenna at the server has been a
well-investigated topic, and several coded caching schemes and improved lower
bounds on the performance are known for the same. However, this MACC network
has not yet been studied under multi-antenna settings in the coded caching
literature. We study the multi-antenna MACC problem and propose a solution for
the same by constructing a pair of arrays called caching and delivery arrays.
We present three constructions of caching and delivery arrays for different
scenarios and obtain corresponding multi-antenna MACC schemes for the same. Two
schemes resulting from the above constructions achieve optimal performance
under uncoded placement and one-shot delivery. The optimality is shown by
matching the performance of the multi-antenna MACC scheme to that of an optimal
multi-antenna scheme for a dedicated cache network having an identical number
of users, and each user has a normalized cache size of . Further, as a
special case, one of the proposed schemes subsumes an existing optimal MACC
scheme for the single-antenna setting.Comment: 11 pages (double column), 3 Figure
Combinatorial Multi-Access Coded Caching: Improved Rate-Memory Trade-off with Coded Placement
This work considers the combinatorial multi-access coded caching problem
introduced in the recent work by Muralidhar \textit{et al.} [P. N. Muralidhar,
D. Katyal, and B. S. Rajan, ``Maddah-Ali-Niesen scheme for multi-access coded
caching,'' in \textit{IEEE Inf. Theory Workshop (ITW)}, 2021] The problem
setting consists of a central server having a library of files and
caches each of capacity . Each user in the system can access a unique set of
caches, and there exist users corresponding to every distinct set of
caches. Therefore, the number of users in the system is . For the
aforementioned combinatorial multi-access setting, we propose a coded caching
scheme with an MDS code-based coded placement. This novel placement technique
helps to achieve a better rate in the delivery phase compared to the optimal
scheme under uncoded placement, when . For a lower memory regime, we
present another scheme with coded placement, which outperforms the optimal
scheme under uncoded placement if the number of files is no more than the
number of users. Further, we derive an information-theoretic lower bound on the
optimal rate-memory trade-off of the combinatorial multi-access coded caching
scheme. Finally, using the derived lower bound, we show that the first scheme
is optimal in the higher memory regime, and the second scheme is optimal if
.Comment: 15 pages and 5 figure
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