1,720,975 research outputs found
Caching in Heterogeneous Networks
Full text linkA 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. 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 caches' 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 Java application to display temperature, humidity and luminosity in a Wireless Sensor Network
Full text linkThe aim of this thesis is to develop a Java application, using Android platform, to display in a mobile device the values taken by a Wireless Sensor Network (WSN). For this purpose, in this papers, firstly I give a general vision of what the Wireless Sensor Networks are. In particular, I wished to provide a comprehensive analysis of the main component of the WSN: the
sensor node. I describe its hardware and software structural. The second part of the thesis is dedicated to the implementation of the application. It is listed which software were useful to the development and it explained how the application has been built. In the last part of the thesis it is shown the graphical result of the work obtainedope
A Java application to display temperature, humidity and luminosity in a Wireless Sensor Network
Full text linkThe aim of this thesis is to develop a Java application, using Android platform, to display in a mobile device the values taken by a Wireless Sensor Network (WSN). For this purpose, in this papers, firstly I give a general vision of what the Wireless Sensor Networks are. In particular, I wished to provide a comprehensive analysis of the main component of the WSN: the
sensor node. I describe its hardware and software structural. The second part of the thesis is dedicated to the implementation of the application. It is listed which software were useful to the development and it explained how the application has been built. In the last part of the thesis it is shown the graphical result of the work obtaine
On the Error Floor Evaluation of NOMA-Irregular Repetition Slotted ALOHA
Full text linkIn this work, we provide a simple yet tight analytical approximation of the packet loss rate in the error floor region for a non-orthogonal multiple access (NOMA)-based irregular repetition slotted ALOHA (IRSA) scheme. Considering an Internet of Things (IoT) scenario, users randomly select both the number of replicas based on a designed degree distribution and the transmission power from predetermined levels, while successive interference cancellation (SIC) is performed at the receiver. Our derived packet loss rate expression in the finite length regime is promptly evaluated. Its accuracy is validated through Monte-Carlo simulations, demonstrating a strong match across channel loads, including those beyond the low load regime
Cache Placement Optimization for Layered Video Content
Full text linkIn this work, we investigate cache placement strategies for layered video content. We consider a library of video
files that can be requested in different quality levels, according
to a specific distribution. The study involves formulating and
solving two distinct optimization problems to determine the most
effective approach to cache placement. Our aim is to compare the
following strategies: placement strategy which reduces congestion
on the backhaul link by minimizing the number of transmissions
necessary to meet user requests, and placement strategy which
maximizes the probability of users being fully served from cached
content. As shown in the solutions, these two performance metrics
lead to different solutions for content that needs to be cached
Caching in Heterogeneous Networks With Per-File Rate Constraints
No full textWe study the problem of caching optimization in heterogeneous networks with mutual interference and per-file rate constraints from an energy efficiency perspective. A setup is considered in which two cache-enabled transmitter nodes and a coordinator node serve two users. We analyze and compare two approaches: 1) a cooperative approach where each of the transmitters might serve either of the users and 2) a non-cooperative approach in which each transmitter serves only the respective user. We formulate the cache allocation optimization problem so that the overall system power consumption is minimized while the use of the link from the master node to the end users is spared whenever possible. We also propose a low-complexity optimization algorithm and show that it outperforms the considered benchmark strategies. Our results indicate that significant gains both in terms of power saving and sparing of master node’s resources can be obtained when full cooperation between the transmitters is in place. Interestingly, we show that in some cases storing the most popular files is not the best solution from a power efficiency perspective.LTS
Edge Caching: On the Performance of Placement and Delivery Coding Schemes
Full text linkWe study the performance of caching schemes based
on two different coding techniques. A heterogeneous network is
assumed, in which cache-aided relays are connected through a
backhaul link to a master node while no connection exits between
users and the master node. The first caching scheme considers
to fill the cache with encoded content while the second scheme
considers to encode the content during the delivery phase. We
compare the schemes by characterizing the average transmission
load when users ask for downloading content to the network.
We provide an approximation of the expression of the average
load which allows a fast evaluation of the network behavior for
each scheme considered. We further assume a constraint on the
capacity of the backhaul link and derive the expression of the
outage probability, i.e. the probability that the system is not able
to serve the entire set of users demands. Finally, we examine and
discuss how the derived analysis of a two relays scenario can be
scaled to study the performance of a network with a generic
number of relays
Per-Replica Power Diversity in Grant-Free Multiple Access: Design and Performance Evaluation
No full textThis work presents the concept of power replica diversity applied to grant-free multiple access, where users access the channel following contention resolution diversity slotted ALOHA protocol (CRDSA). We study a system where users can transmit two replicas at two different power levels, maintaining a constant level of energy consumption. The receiver’s
performance is determined by a threshold-based capture effect. We demonstrate how varying the power levels of replicas can impact performance in terms of throughput, packet loss rate, and spectral efficiency. To evaluate the maximum system load supported by the most advantageous power levels, we analyze the asymptotic case of infinitely long frames. The results show that the proposed technique outperforms CRDSA in terms of both throughput and packet loss rate while achieving a higher spectral efficiency, considering fixed energy consumption
Caching in Heterogeneous Networks with Per-File Rate Constraints
No full textWe study the problem of caching optimization in
heterogeneous networks with mutual interference and per-file
rate constraints from an energy efficiency perspective. A setup
is considered in which two cache-enabled transmitter nodes and
a coordinator node serve two users. We analyse and compare
two approaches: (i) a cooperative approach where each of the
transmitters might serve either of the users and (ii) a noncooperative approach in which each transmitter serves only the
respective user. We formulate the cache allocation optimization
problem so that the overall system power consumption is minimized while the use of the link from the master node to the
end users is spared whenever possible. We also propose a lowcomplexity optimization algorithm and show that it outperforms
the considered benchmark strategies.
Our results indicate that significant gains both in terms of
power saving and sparing of master node’s resources can be
obtained when full cooperation between the transmitters is in
place. Interestingly, we show that in some cases storing the most
popular files is not the best solution from a power efficiency
perspective
Multi-Satellite NOMA-Irregular Repetition Slotted ALOHA for IoT Networks
Full text linkAs the transition from 5G to 6G unfolds, a substantial increase in Internet of Things (IoT) devices is expected, enabling seamless and pervasive connectivity across
various applications. Accommodating this surge and meeting the
high capacity demands will necessitate the integration of NonTerrestrial Networks (NTNs). However, the extensive coverage
area of satellites, relative to terrestrial receivers, will lead to
a high density of users attempting to access the channel at
the same time, increasing the collision probability. In turn, the
deployment of mega constellations make it possible for ground
users to be in visibility of more than one satellite at the same time,
enabling receiver diversity. Therefore, in this paper, we evaluate
the impact of multi-receivers in scenarios where IoT nodes share
the channel following a non-orthogonal multiple access (NOMA)-
irregular repetition slotted ALOHA (IRSA) protocol. Considering
the impairments of satellite channels, we derive a lower bound of
system performance, serving as a fast tool for initial evaluation
of network behavior. Additionally, we identify the trade-offs
inherent to the network design parameters, with a focus on packet
loss rate and energy efficiency. Notably, in the visibility of only
one extra satellite as receiver yields significant gains in overall
system performance
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