8 research outputs found
Multi-access Coded Caching with Optimal Rate and Linear Subpacketization under PDA and Consecutive Cyclic Placement
This work considers the multi-access caching system proposed by Hachem et
al., where each user has access to L neighboring caches in a cyclic wrap-around
fashion. We first propose a placement strategy called the consecutive cyclic
placement, which achieves the maximal local caching gain. Then under the
consecutive cyclic placement, we derive the optimal coded caching gain from the
perspective of Placement Delivery Array (PDA), thus obtaining a lower bound on
the rate of PDA. Finally, under the consecutive cyclic placement, we construct
a class of PDA, leading to a multi-access coded caching scheme with linear
subpacketization, which achieves our derived lower bound for some parameters;
while for other parameters, the achieved coded caching gain is only 1 less than
the optimal one. Analytical and numerical comparisons of the proposed scheme
with existing schemes are provided to validate the performance.Comment: 30 pages, 7 figure
Coded Caching Schemes for Multiaccess Topologies via Combinatorial Design
This paper studies a multiaccess coded caching (MACC) where the connectivity
topology between the users and the caches can be described by a class of
combinatorial designs. Our model includes as special cases several MACC
topologies considered in previous works. The considered MACC network includes a
server containing files, cache nodes and cacheless users,
where each user can access cache nodes. The server is connected to the
users via an error-free shared link, while the users can retrieve the cache
content of the connected cache-nodes while the users can directly access the
content in their connected cache-nodes. Our goal is to minimise the worst-case
transmission load on the shared link in the delivery phase. The main limitation
of the existing MACC works is that only some specific access topologies are
considered, and thus the number of users should be either linear or
exponential to . We overcome this limitation by formulating a new
access topology derived from two classical combinatorial structures, referred
to as the -design and the -group divisible design. In these topologies,
scales linearly, polynomially, or even exponentially with . By
leveraging the properties of the considered combinatorial structures, we
propose two classes of coded caching schemes for a flexible number of users,
where the number of users can scale linearly, polynomially or exponentially
with the number of cache nodes. In addition, our schemes can unify most schemes
for the shared link network and unify many schemes for the multi-access network
except for the cyclic wrap-around topology.Comment: 48 page
Hierarchical Cache-Aided Linear Function Retrieval with Security and Privacy Constraints
The hierarchical caching system where a server connects with multiple mirror
sites, each connecting with a distinct set of users, and both the mirror sites
and users are equipped with caching memories has been widely studied. However
all the existing works focus on single file retrieval, i.e., each user requests
one file, and ignore the security and privacy threats in communications. In
this paper we investigate the linear function retrieval problem for
hierarchical caching systems with content security and demand privacy, i.e.,
each user requests a linear combination of files, and meanwhile the files in
the library are protected against wiretappers and users' demands are kept
unknown to other users and unconnected mirror sites. First we propose a new
combination structure named hierarchical placement delivery array (HPDA), which
characterizes the data placement and delivery strategy of a coded caching
scheme. Then we construct two classes of HPDAs. Consequently two classes of
schemes with or without security and privacy are obtained respectively where
the first dedicates to minimizing the transmission load for the first hop and
can achieve the optimal transmission load for the first hop if ignoring the
security and privacy constraints; the second has more flexible parameters on
the memory sizes and a lower subpacketization compared with the first one, and
achieves a tradeoff between subpacketization and transmission loads.Comment: arXiv admin note: substantial text overlap with arXiv:2205.0023