1,721,028 research outputs found
Optimal Routing for Quantum Networks
Full text linkTo fully unleash the potentials of quantum computing, several new challenges and open problems need to be addressed. From a routing perspective, the optimal routing problem, i.e., the problem of jointly designing a routing protocol and a route metric assuring the discovery of the route providing the highest quantum communication opportunities between an arbitrary couple of quantum devices, is crucial. In this paper, the optimal routing problem is addressed for generic quantum network architectures composed by repeaters operating through single atoms in optical cavities. Specifically, we first model the entanglement generation through a stochastic framework that allows us to jointly account for the key physical-mechanisms affecting the end-to-end entanglement rate, such as decoherence time, atom-photon and photon-photon entanglement generation, entanglement swapping, and imperfect Bell-state measurement. Then, we derive the closed-form expression of the end-to-end entanglement rate for an arbitrary path and we design an efficient algorithm for entanglement rate computation. Finally, we design a routing protocol and we prove its optimality when used in conjunction with the entanglement rate as routing metric
End-to-End Entanglement Rate: Toward a Quantum Route Metric
No full textWe present an entanglement-generation rate analysis for generic quantum network architectures composed by repeaters operating through single atoms in optical cavities. Specifically, we analytically derive the end-to-end entanglement rate between a couple of nodes through an arbitrary path. To this aim, we first model the entanglement generation through a stochastic framework that allows us to jointly account for all the key physical-mechanisms affecting the end-to-end entanglement rate, such as decoherence time, atom- photon and photon-photon entanglement generation, entanglement swapping and imperfect bell-state measurement. Then, we derive the closed-form expression of the end-to-end entanglement rate. Finally, we evaluate the entanglement rate under realistic parameter setting
Medical emergency alarm dissemination in urban environments
No full textDuring medical emergencies, the ability to communicate the state and position of injured individuals is essential. In critical situations or crowd aggregations, this may result difficult or even impossible due to the inaccuracy of verbal communication, the lack of precise localization for the medical events, and/or the failure/congestion of infrastructure-based communication networks. In such a scenario, a temporary (ad hoc) wireless network for disseminating medical alarms to the closest hospital, or medical field personnel, can be usefully employed to overcome the mentioned limitations. This is particularly true if the ad hoc network relies on the mobile phones that people normally carry, since they are automatically distributed where the communication needs are. Nevertheless, the feasibility and possible implications of such a network for medical alarm dissemination need to be analysed. To this aim, this paper presents a study on the feasibility of medical alarm dissemination through mobile phones in an urban environment, based on realistic people mobility. The results showed the dependence between the medical alarm delivery rates and both people and hospitals density. With reference to the considered urban scenario, the time needed to delivery medical alarms to the neighbour hospital with high reliability is in the order of minutes, thus revealing the practicability of the reported network for medical alarm dissemination
Spectrum Sensing in small-scale networks: Dealing with multiple mobile PUs
No full textThe emerging applications of the small-scale primary-user (PU) paradigm require Cognitive Radio (CR) networks to explicitly support the mobility of a multitude of PUs, concurrently using the same spectrum band. In this paper, the effects of multiple mobile PUs on the spectrum sensing functionality are analyzed to jointly maximize the sensing efficiency and the sensing accuracy. To this aim, as first, a new mathematical model (the aggregate PU model) is proposed to effectively describe the cumulative effects of multiple mobile PUs on the spectrum sensing functionality. Then, stemming from this model, closed-form expressions for the sensing time and the transmission time that jointly maximize the sensing efficiency and the sensing accuracy are derived. Through the derived closed-form expressions, the following fundamental questions are answered: (i) How long can a CR user transmit without interfering with the multiple mobile PUs? (ii) How long must a CR user observe a targeted spectrum band to reliably detect multiple mobile PUs? All the theoretical results are derived by adopting a general mobility model for the multiple mobile PUs. The analytical results are finally validated through simulations
Receiver design for a bionic nervous system: Modeling the dendritic processing power
No full textIntrabody nanonetworks for nervous system monitoring are envisioned as a key application of the Internet of Nano-Things (IoNT) paradigm, with the aim of developing radically new medical diagnosis and treatment techniques. Indeed, very recently, bionic devices have been implanted inside a living human brain as innovative treatment for drug-resistant epilepsy. In this context, this paper proposes a systems-theoretic communication model to capture the actual behavior of biological neurons. Specifically, biological neurons exhibit physical extension due to their projections called dendrites, which propagate the electrochemical stimulation received via synapses to the soma. Experimental evidences show that the dendrites exhibit two main features: 1) the compartmentalization at the level of the dendritic branches of the neuronal processes and 2) the location-dependent preference for different frequencies. Stemming from these experimental evidences, we propose to model the dendritic tree as a spatiotemporal filter bank, where each filter models the behavior in both space and time of a dendritic branch. Each filter is fully characterized along with the overall neuronal response. Furthermore, sufficient conditions on the incoming stimulus for inducing a null-neuronal response are derived. The conducted theoretical analysis shows that: 1) the neuronal information is encoded in the stimulus temporal pattern, i.e., it is possible to select the neuron to affect by changing the stimulus frequency content; in this sense, the communication among neurons is frequency-selective and 2) the spatial distribution of the dendrites affects the neuronal response; in this sense, the communication among neurons is spatial-selective. The theoretical analysis is validated through a real neuron morphology
Optimal database access for TV white space
No full textIn TV White Space, the unlicensed users are required to periodically access a database to acquire information on the spectrum usage of the licensed users. In addition, the unlicensed users can access the database on-demand, whenever they believe convenient, to update the spectrum availability information. In this paper, we design the optimal database access strategy, i.e., the strategy allowing the unlicensed users to jointly: (1) maximize the expected overall communication opportunities through on-demand accesses; and (2) respect the regulatory specifications. To this aim, we develop a stochastic analytical framework that allows us to account for: (1) the PU activity dynamics; (2) the quality dynamics among the different channels; and (3) the overhead induced by the database access. Specifically, at first, we prove that the database access problem can be modeled as a Markov decision process, and we show that it cannot be solved through brute-force search. Then, we prove that the optimal strategy exhibits a threshold structure, and we exploit this threshold property to design an algorithm able to efficiently compute the optimal strategy. The analytical results are finally validated through simulations
Mobile Ad Hoc Networks: the DHT paradigm
Full text linkIn this thesis, the adoption of the hierarchical routing paradigm to achieve a scalable network layer for ad hoc networks has been proposed. The main concept of hierarchical routing is to keep, at any node, complete routing information about nodes which are close to it and lesser information about nodes located further away.
The Augmented Tree-based Routing protocol, a routing protocol for ad hoc networks exploiting both a location-aware addressing schema and a distribute hash table (DHT) system, has been proposed. The adopted addressing schema allows nodes to adopt hierarchical routing, limiting so the overhead introduced in the network, while the DHT system provides the mapping between transient identifiers and node identities.
Since the Augmented Tree-based Routing protocol adopts a multi-path strategy and since most studies in the area of multi-path routing focus on heuristic methods and the performances of these strategies are commonly evaluated by numerical simulations, an analytical framework to evaluate the performance gain achieved by multi-path routing has been proposed. The framework
is based on on graph theory and on terminal-pair routing reliability (TPRR) as performance measure.
Moreover, some features of the proposed protocol has been exploited design a peer-to-peer (P2P) system over a mobile ad hoc network (MANET) resorting to a cross-layer approach. It has been proved that simply deploying P2P systems over MANETs may cause poor performances. By coupling both the direct and the indirect key-based routing at the network layer and by resorting to the same hierarchical address space structure of ATR, we are able to build a P2P overlay network in which the logical proximity agrees with the physical one, limiting so the message overhead and avoiding the redundancy.
Finally, by extending the proposed location-aware addressing to match with the opportunistic forwarding protocol, a novel routing protocol for disruption tolerant network (DTN) and delay tolerant network (DTN) has been proposed. By exploiting both the temporal diversity and the broadcast nature of the wireless propagation, such a protocol can enable connectivity in ad hoc environments characterized by non stationary wireless propagation as well as sparse topologies
A Reliability-based Framework for Multi-path Routing Analysis in Mobile Ad-Hoc Networks
No full textUnlike traditional routing procedures that, at the best, single out a unique route, multi-path routing protocols discover proactively several alternative routes. It has been recognised that multi-path routing can be more efficient than traditional one mainly for mobile ad hoc networks, where route failure events are frequent. Most studies in the area of multi-path routing focus on heuristic methods, and the performances of these strategies are commonly evaluated by numerical simulations. The need of a theoretical analysis motivates such a paper, which proposes to resort to the terminal-pair routing reliability as performance metric. This metric allows one to assess the performance improvement gained by the availability of route diversity. More specifically, resorting to graph theory, we propose an analytical framework to multi-path route discovery processes against route failures for mobile ad hoc networks. Moreover, we derive a useful bound to easily estimate the performance improvements achieved by multi-path routing with respect to any traditional routing protocol. Finally, numerical simulation results show the effectiveness of this performance analysis
Quantum Internet Addressing
Full text linkThe design of the Quantum Internet protocol stack is at its infancy and
early-stage conceptualization. And different heterogeneous proposals are
currently available in the literature. The underlying assumption of the
existing proposals is that they implicitly mimic classical Internet Protocol
design principles: "A name indicates what we seek. An address indicates where
it is. A route indicates how to get there''. Hence the network nodes are
labeled with classical addresses, constituted by classical bits, and these
labels aim at reflecting the node location within the network topology. In this
paper, we argue that this twofold assumption of classical and location-aware
addressing constitutes a restricting design option, which prevents to scale the
quantumness to the network functionalities, beyond simple information
encoding/decoding. On the contrary, by embracing quantumness within the node
addresses, quantum principles and phenomena could be exploited for enabling a
quantum native functioning of the entire communication network. This will
unleash the ultimate vision and capabilities of the Quantum Internet
On the impact of primary traffic correlation in TV White Space
No full textIn TV White Space, a secondary user must access periodically to a geolocated database to acquire the spectrum availability information. Furthermore, it can access on-demand to the database to update such an information. The more frequent are the on-demand accesses, the higher are the communication opportunities available to the secondary user but the higher is the induced overhead. Hence, in this manuscript, the on-demand access is investigated to a-priori determine whenever it is advantageous to perform it by accounting for the correlation exhibited by primary traffic patterns. To this aim, first the on-demand access is modeled through the general notions of reward and cost. Then, it is proved that the on-demand access maximizing the total reward available to the secondary user is a Markov Decision Process. Stemming from these results, a computational-efficient algorithm is designed. Finally, the theoretical analysis is validated through numerical simulations
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