75 research outputs found
Hypergraph-Based Analysis of Clustered Cooperative Beamforming with Application to Edge Caching
The evaluation of the performance of clustered cooperative beamforming in
cellular networks generally requires the solution of complex non-convex
optimization problems. In this letter, a framework based on a hypergraph
formalism is proposed that enables the derivation of a performance
characterization of clustered cooperative beamforming in terms of per-user
degrees of freedom (DoF) via the efficient solution of a coloring problem. An
emerging scenario in which clusters of cooperative base stations (BSs) arise is
given by cellular networks with edge caching. In fact, clusters of BSs that
share the same requested files can jointly beamform the corresponding encoded
signals. Based on this observation, the proposed framework is applied to obtain
quantitative insights into the optimal use of cache and backhaul resources in
cellular systems with edge caching. Numerical examples are provided to
illustrate the merits of the proposed framework.Comment: 10 pages, 5 figures, Submitte
Complete Interference Mitigation Through Receiver-Caching in Wyner's Networks
We present upper and lower bounds on the per-user multiplexing gain (MG) of
Wyner's circular soft-handoff model and Wyner's circular full model with
cognitive transmitters and receivers with cache memories. The bounds are tight
for cache memories with prelog in the soft-handoff model and for
in the full model, where denotes the number of possibly
demanded files. In these cases the per-user MG of the two models is ,
the same as for non-interfering point-to-point links with caches at the
receivers. Large receiver cache-memories thus allow to completely mitigate
interference in these networks.Comment: Submitted to ITW 2016 in Cambridg
On the Interplay Between Edge Caching and HARQ in Fog-RAN
In a Fog Radio Access Network (Fog-RAN), edge caching is combined with
cloud-aided transmission in order to compensate for the limited hit probability
of the caches at the base stations (BSs). Unlike the typical wired scenarios
studied in the networking literature in which entire files are typically
cached, recent research has suggested that fractional caching at the BSs of a
wireless system can be beneficial. This paper investigates the benefits of
fractional caching in a scenario with a cloud processor connected via a
wireless fronthaul link to a BS, which serves a number of mobile users on a
wireless downlink channel using orthogonal spectral resources. The fronthaul
and downlink channels occupy orthogonal frequency bands. The end-to-end
delivery latency for given requests of the users depends on the HARQ processes
run on the two links to counteract fading-induced outages. An analytical
framework based on theory of Markov chains with rewards is provided that
enables the optimization of fractional edge caching at the BSs. Numerical
results demonstrate meaningful advantages for fractional caching due to the
interplay between caching and HARQ transmission. The gains are observed in the
typical case in which the performance is limited by the wireless downlink
channel and the file popularity distribution is not too skewed
Caching at the Edge with Fountain Codes
We address the use of linear randon fountain codes caching schemes in a
heterogeneous satellite network. We consider a system composed of multiple hubs
and a geostationary Earth orbit satellite. Coded content is memorized in hubs'
caches in order to serve immediately the user requests and reduce the usage of
the satellite backhaul link. We derive the analytical expression of the average
backhaul rate, as well as a tight upper bound to it with a simple expression.
Furthermore, we derive the optimal caching strategy which minimizes the average
backhaul rate and compare the performance of the linear random fountain code
scheme to that of a scheme using maximum distance separable codes. Our
simulation results indicate that the performance obtained using fountain codes
is similar to that of maximum distance separable codes
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