5,612 research outputs found
Coding, Multicast and Cooperation for Cache-Enabled Heterogeneous Small Cell Networks
Caching at the wireless edge is a promising approach to dealing with massive content delivery in heterogeneous wireless networks, which have high demands on backhaul. In this paper, a typical cache-enabled small cell network under heterogeneous file and network settings is considered using maximum distance separable (MDS) codes for content restructuring. Unlike those in the literature considering online settings with the assumption of perfect user request information, we estimate the joint user requests using the file popularity information and aim to minimize the long-term average backhaul load for fetching content from external storage subject to the overall cache capacity constraint by optimizing the content placement in all the cells jointly. Both multicast-aware caching and cooperative caching schemes with optimal content placement are proposed. In order to combine the advantages of multicast content delivery and cooperative content sharing, a compound caching technique, which is referred to as multicast-aware cooperative caching, is then developed. For this technique, a greedy approach and a multicast-aware in-cluster cooperative approach are proposed for the small-scale networks and large-scale networks, respectively. Mathematical analysis and simulation results are presented to illustrate the advantages of MDS codes, multicast, and cooperation in terms of reducing the backhaul requirements for cache-enabled small cell networks
Optimizing MDS Codes for Caching at the Edge
In this paper we investigate the problem of optimal MDS-encoded cache
placement at the wireless edge to minimize the backhaul rate in heterogeneous
networks. We derive the backhaul rate performance of any caching scheme based
on file splitting and MDS encoding and we formulate the optimal caching scheme
as a convex optimization problem. We then thoroughly investigate the
performance of this optimal scheme for an important heterogeneous network
scenario. We compare it to several other caching strategies and we analyze the
influence of the system parameters, such as the popularity and size of the
library files and the capabilities of the small-cell base stations, on the
overall performance of our optimal caching strategy. Our results show that the
careful placement of MDS-encoded content in caches at the wireless edge leads
to a significant decrease of the load of the network backhaul and hence to a
considerable performance enhancement of the network.Comment: to appear in Globecom 201
Fundamental Limits on Latency in Transceiver Cache-Aided HetNets
Stringent mobile usage characteristics force wire- less networks to undergo a
paradigm shift from conventional connection-centric to content-centric
deployment. With respect to 5G, caching and heterogeneous networks (HetNet) are
key technologies that will facilitate the evolution of highly content- centric
networks by facilitating unified quality of service in terms of low-latency
communication. In this paper, we study the impact of transceiver caching on the
latency for a HetNet consisting of a single user, a receiver and one
cache-assisted transceiver. We define an information-theoretic metric, the
delivery time per bit (DTB), that captures the delivery latency. We establish
coinciding lower and upper bounds on the DTB as a function of cache size and
wireless channel parameters; thus, enabling a complete characterization of the
DTB optimality of the network under study. As a result, we identify cache
beneficial and non-beneficial channel regimes.Comment: 5 pages, ISIT 201
Cooperative Caching and Transmission Design in Cluster-Centric Small Cell Networks
Wireless content caching in small cell networks (SCNs) has recently been
considered as an efficient way to reduce the traffic and the energy consumption
of the backhaul in emerging heterogeneous cellular networks (HetNets). In this
paper, we consider a cluster-centric SCN with combined design of cooperative
caching and transmission policy. Small base stations (SBSs) are grouped into
disjoint clusters, in which in-cluster cache space is utilized as an entity. We
propose a combined caching scheme where part of the available cache space is
reserved for caching the most popular content in every SBS, while the remaining
is used for cooperatively caching different partitions of the less popular
content in different SBSs, as a means to increase local content diversity.
Depending on the availability and placement of the requested content,
coordinated multipoint (CoMP) technique with either joint transmission (JT) or
parallel transmission (PT) is used to deliver content to the served user. Using
Poisson point process (PPP) for the SBS location distribution and a hexagonal
grid model for the clusters, we provide analytical results on the successful
content delivery probability of both transmission schemes for a user located at
the cluster center. Our analysis shows an inherent tradeoff between
transmission diversity and content diversity in our combined
caching-transmission design. We also study optimal cache space assignment for
two objective functions: maximization of the cache service performance and the
energy efficiency. Simulation results show that the proposed scheme achieves
performance gain by leveraging cache-level and signal-level cooperation and
adapting to the network environment and user QoS requirements.Comment: 13 pages, 10 figures, submitted for possible journal publicatio
Caching in Heterogeneous Networks
A promising solution in order to cope with the massive request of wireless data traffic
consists of having replicas of the potential requested content memorized across the
network. In cache-enabled heterogeneous networks, content is pre-fetched close to the
users during network off-peak periods in order to directly serve the users when the
network is congested. In fact, the main idea behind caching is the replacement of
backhaul capacity with storage capabilities, for example, at the edge of the network.
Caching content at the edge of heterogeneous networks not only leads to significantly
reduce the traffic congestion in the backhaul link but also leads to achieve higher
levels of energy efficiency. However, the good performance of a system foresees a deep
analysis of the possible caching techniques. Due to the physical limitation of the cachesā
size and the excessive amount of content, the design of caching policies which define
how the content has to be cached and select the likely data to store is crucial.
Within this thesis, caching techniques for storing and delivering the content in
heterogeneous networks are investigated from two different aspects. The first part
of the thesis is focused on the reduction of the power consumption when the cached
content is delivered over an Gaussian interference channel and per-file rate constraints
are imposed. Cooperative approaches between the transmitters in order to mitigate
the interference experienced by the users are analyzed. Based on such approaches, the
caching optimization problem for obtaining the best cache allocation solution (in the
sense of minimizing the average power consumption) is proposed. The second part of
the thesis is focused on caching techniques at packet level with the aim of reducing
the transmissions from the core of an heterogeneous network. The design of caching
schemes based on rate-less codes for storing and delivering the cached content are
proposed. For each design, the placement optimization problem which minimizes the
transmission over the backhaul link is formulated
A New Look at Physical Layer Security, Caching, and Wireless Energy Harvesting for Heterogeneous Ultra-dense Networks
Heterogeneous ultra-dense networks enable ultra-high data rates and ultra-low
latency through the use of dense sub-6 GHz and millimeter wave (mmWave) small
cells with different antenna configurations. Existing work has widely studied
spectral and energy efficiency in such networks and shown that high spectral
and energy efficiency can be achieved. This article investigates the benefits
of heterogeneous ultra-dense network architecture from the perspectives of
three promising technologies, i.e., physical layer security, caching, and
wireless energy harvesting, and provides enthusiastic outlook towards
application of these technologies in heterogeneous ultra-dense networks. Based
on the rationale of each technology, opportunities and challenges are
identified to advance the research in this emerging network.Comment: Accepted to appear in IEEE Communications Magazin
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