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Simulation of Multimodal Optical and Acoustic Communications in Underwater Networks
Get PDFIn this paper, we consider data muling over a network of fixed sensors by employing a mobile Autonomous Underwater Vehicle (AUV). We approach the problem using both acoustic and optical communications together in a multi-modal hybrid network: the most appropriate physical layer is chosen according to the quality of the transmissions that take place over time. We consider three distinct cases of water type: clear, coastal and turbid water, in order to test the system behavior under different conditions. The ambient light noise is realistically reproduced via the Hydrolight software and taken into account, due to its important contribution to the optical SNR in shallow waters. Finally, we simulate the performance of the system using the DESERT Underwater framework during missions of interest in different channel conditions and network depth. Our results show the effectiveness of a multi-modal underwater network in the cases of clear and coastal waters.TRUEpu
Dynamic Resource Provisioning for Energy Efficiency in Wireless Access Networks: a Survey and an Outlook
Get PDFTraditionally, energy efficiency aspects have been included in the wireless access network design space only in the context of power control aimed at interference mitigation, and for the increase of the terminal battery lifetime. Energy consumption of network components has also, for a long time, not been considered an issue, neither in equipment design, nor in network planning and management. However, in recent years, with the user demand increasing at nearly exponential pace, and margins rapidly shrinking, concerns about energy efficiency have been raised, with the objective to reduce network operational costs (not to mention the environmental issues). Installing more energyefficient hardware does not seem to fully solve the problem, since wireless access networks are almost invariably (over)provisioned with respect to the peak user demand. This means that efficient resource management schemes, capable of controlling how much of the network infrastructure is actually needed and which parts can be temporarily powered off to save energy, can be extremely effective and provide quite large cost reductions. Considering that most of the energy in wireless access networks is consumed in the radio part, a dynamic provisioning of wireless access network resources is crucial, to achieve energy-efficient operation. The consensus on this approach in the research community has been wide in the last few years, and a large number of solutions was proposed. In this paper, we survey the most important proposals, considering the two most common wireless access technologies, namely cellular and WLAN. Main features of the proposed solutions are analyzed and compared, with an outlook on their applicability in typical network scenarios that also include cooperation between both access technologies. Moreover, we provide an overview of the practical implementation aspects that must be addressed to achieve truly energy-efficient wireless access networks, including current standardization- work, and trends in the development of energy-efficient hardware.pu
Internet of Things for Smart Cities
Get PDFThe Internet of Things (IoT) shall be able to incorporate transparently and seamlessly a large number of different and heterogeneous end systems, while providing open access to selected subsets of data for the development of a plethora of digital services. Building a general architecture for the IoT is hence a very complex task, mainly because of the extremely large variety of devices, link layer technologies, and services that may be involved in such a system. In this paper we focus specifically to an urban IoT systems that, while still being quite a broad category, are characterized by their specific application domain. Urban IoTs, in fact, are designed to support the Smart City vision, which aims at exploiting the most advanced communication technologies to support added-value services for the administration of the city and for the citizens. This paper hence provides a comprehensive survey of the enabling technologies, protocols and architecture for an urban IoT. Furthermore, the paper will present and discuss the technical solutions and best-practice guidelines adopted in the Padova Smart City project, a proof of concept deployment of an IoT island in the city of Padova, Italy, performed in collaboration with the city municipality.pu
Modeling and Analysis of Opportunistic Routing in Multi-hop Wireless Networks
Get PDFOpportunistic Routing (OR) takes advantage of the
broadcast nature of the wireless medium to increase reliability in communications. Instead of selecting one node as the nexthop forwarder, OR selects a set of candidates to forward the packet. In this way, if one of them does not receive the packet from the source, another candidate will be able to do it; this avoids the need for a re-transmission from the source. To increase the successful delivery ratio, we can increase the size of the candidate set or the number of re-transmissions, but, we must take into account the impact on the use of the network resources.
In this paper, we propose a Markov chain as a general model
for OR that can be applied to any kind of network topology
and any candidate selection algorithm without any constraint.
The only input parameters needed are: i) the candidate list
of each node; ii) the link delivery probability between nodes; and, iii) the maximum number of re-transmissions in each node. Taking this data into account, our model allows for the evaluation of the performance of different candidate selection algorithms according to different metrics, such as the expected number of transmissions (ExNT), which is one of the most relevant metrics in OR. Our model also enables an evaluation of the influence of the number of candidates, its relation to the number of retransmissions and how these two parameters together contribute to the successful delivery of data packets.TRUEpu
The value of BS flexibility for QoS-aware sleep modes in cellular access networks
Get PDFDOI: http://dx.doi.org/10.1109/ICCW.2014.6881312Sleep modes are one of the most widely investigated techniques to decrease energy consumption in cellular access networks. However, the application of such algorithms on the base station (BS) equipment of today presents several challenges. Indeed, currently installed BSs are unfit for frequent on/off cycles. This may lead to increased failure rates and malfunctioning, ultimately resulting in significant CAPEX and OPEX increases for mobile network operators (MNOs). This situation calls for a new generation of flexible BSs endowed with a ”hot standby” mode, which guarantees quick activation times without affecting BS availability. However, when such new BS models become available, MNOs will need to determine a migration path to a new network deployment with progressive replacement of old BS equipment. In this paper, we propose an approach to quantify the benefits obtained by MNOs with the deployment of flexible BSs, in terms of maximum energy efficiency achievable with a given fraction of flexible BSs in their network. More specifically, we propose a method for estimating, for a given percentage of flexible BSs, the energy optimal density of static and flexible BSs, which is sufficient to serve a given set of active users with predefined performance guarantees. We show how to apply our method to derive bounds on the maximum energy saving achievable through sleep modes, as a function of the fraction of flexible BSs. We determine the effect of uncertainty in traffic predictions on sleep modes performance, and we derive indications for optimal network planning strategies.TRUEpu
On the MAC for Power-Line Communications: Modeling Assumptions and Performance Tradeoffs
Get PDFPower-line communications are becoming a key component in home networking. The dominant MAC protocol for high data-rate power-line communications, IEEE 1901, employs a CSMA/CA mechanism similar to the backoff process of 802.11. Existing performance evaluation studies of this protocol assume that the backoff processes of the stations are independent (the so-called decoupling assumption). However, in contrast to 802.11, 1901 stations can change their state after sensing the medium busy, which introduces strong coupling between the stations, and, as a result, makes existing analyses inaccurate. In this paper, we propose a new performance model for 1901, which does not rely on the decoupling assumption. We prove that our model admits a unique solution. We confirm the accuracy of our model using both testbed experiments and simulations, and we show that it surpasses current models based on the decoupling assumption. Furthermore, we study the tradeoff between delay and throughput existing with 1901. We show that this protocol can be configured to accommodate different throughput and jitter requirements, and give systematic guidelines for its configuration.TRUEpu
Bisection (Band)Width of Product Networks with Application to Data Centers
Get PDFThe bisection width of interconnection networks has always been important in parallel computing, since it bounds the speed at which information can be moved from one side of a network to another, i.e., the bisection bandwidth. Finding its exact value has proven to be challenging for some network families. For instance, the problem of finding the exact bisection width of the multidimensional torus was posed by Leighton [1, Problem 1.281] and has remained open for almost 20 years. We provide two general results that allow us to obtain upper and lower bounds on the bisection width of any product graph as a function of some properties of its factor graphs. The power of these results is shown by deriving the exact value of the bisection width of the torus, as well as of several d-dimensional classical parallel topologies that can be obtained by the application of the Cartesian product of graphs. We also apply these results to data centers, by obtaining bounds for the bisection bandwidth of the d-dimensional BCube network, a recently proposed topology for data centers.pu
Remote Peering: More Peering without Internet Flattening
Get PDFhttp://dx.doi.org/10.1145/2674005.2675013The trend toward more peering between networks is com-
monly conflated with the trend of Internet flattening, i.e.,
reduction in the number of intermediary organizations on
Internet paths. Indeed, direct peering interconnections by-
pass layer-3 transit providers and make the Internet flat-
ter. This paper studies an emerging phenomenon that sepa-
rates the two trends: we present the first systematic study of remote peering, an interconnection where remote networks
peer via a layer-2 provider. ur measurements reveal sig-
nificant presence of remote peering at IXPs (Internet eX-
change Points) worldwide. Based on ground truth traffic,
we also show that remote peering has a substantial potential
to offload transit traffic. Generalizing the empirical results,we analytically derive conditions for economic viability of remote peering versus transit and direct peering. Because remote-peering services are provided on layer 2, our results challenge the traditional reliance on layer-3 topologies in modeling the Internet economic structure. We also discuss broader implications of remote peering for reliability, security, accountability, and other aspects of Internet research.TRUEpu
No full textTopic classification of texts is one of the most interesting challenges in Natural Language Processing (NLP).
Topic classifiers commonly use a bag of words approach, in
which the classifier uses (and is trained with) selected terms from the in put texts. In this work we present techniques based on graph similarity to classify short texts by topic. In our classifier we build graphs from the input texts, and then use properties of these graphs to classify them. We have tested the resulting algorithm by classifying Twitter messages in Spanish among a predefined set of topics, achieving more than 70% accuracy.Electronic Technology, Signal and Communications Theory, and Telematic EngineeringUniversidad Carlos III de Madrid, Spainpu