94 research outputs found
Database access strategy for TV White Space cognitive radio networks
No full textVery recently, city administrations launched TV White Space wireless networks to enable the smart city paradigm. These initiatives leverage the possibility allowed by regulations of unlicensed access to the TV White Space spectrum. All theses rulings rely on a periodic access to a database service as the primary mechanism for the unlicensed users to determine the White Space availability. Nevertheless, the specifics of such a mechanism are yet to be determined. In this paper, we address this issue by designing a database access strategy that allows unlicensed users to: i) respect the requirements imposed by the existing rulings; ii) maximize the expected communication opportunities provided by the TV White Space through the on-demand database accesses. To this aim, we prove the database access problem can be modeled as a Markov Decision Process and we provide the closed-form expressions of the transition probabilities. The analytical results are finally validated through simulations
On the achievable throughput over TVWS sensor networks
No full textIn this letter, we study the throughput achievable by an unlicensed sensor network operating over TV white space spectrum in presence of coexistence interference. Through the letter, we first analytically derive the achievable throughput as a function of the channel ordering. Then, we show that the problem of deriving the maximum expected throughput through exhaustive search is computationally unfeasible. Finally, we derive a computational-efficient algorithm characterized by polynomial-time complexity to compute the channel set maximizing the expected throughput and, stemming from this, we derive a closed-form expression of the maximum expected throughput. Numerical simulations validate the theoretical analysis
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
On the probabilistic deployment of smart grid networks in TV white space
No full textTo accommodate the rapidly increasing demand for wireless broadband communications in Smart Grid (SG) networks, research efforts are currently ongoing to enable the SG networks to utilize the TV spectrum according to the Cognitive Radio paradigm. To this aim, in this letter, we develop an analytical framework for the optimal deployment of multiple closely-located SG Neighborhood Area Networks (NANs) concurrently using the same TV spectrum. The objective is to derive the optimal values for both the number of NANs and their coverage. More specifically, regarding the number of NANs, we derive the optimal closed-form expression, i.e., the closed-form expression that assures the deployment of the maximum number of NANs in the considered region satisfying a given collision constraint on the transmissions of the NANs. Regarding the NAN coverage, we derive the optimal closed-form expression, i.e., the closed-form expression of the NAN transmission range that assures the maximum coverage of each NAN in the considered region satisfying the given collision constraint. All the theoretical results are derived by adopting a stochastic approach. Finally, numerical results validate the theoretical analysis
A theoretical model for opportunistic routing in ad hoc networks
No full textTraditional routing strategies for multi-hop wireless networks forward packets by selecting at the sender side the next hop for each packet. Recently, such a paradigm has been called into question by a new approach, namely the opportunistic routing. It exploits the broadcast nature of wireless transmissions to take advantage from spatial diversity by routing the packets according to the propagation conditions, i.e. by selecting the next hop at the receiver side. Although numerous opportunistic algorithms and protocols have been proposed in the last years, very few works have used an analytical approach to analyze the opportunistic routing behavior so as to provide a guideline for future protocol design. In this paper, we propose an analytical model to describe any routing procedures operating according to the opportunistic paradigm. It applies in a very general multi-hop scenario and is not restricted to any specific network topology or opportunistic protocol. The model requires the knowledge of both the delivery ratios and node priority, which is based on the adopted routing metric (expected transmission count (ETX), geographic distance, etc). In this paper we exploit such a model to derive a closed-form expression of the average number of data-link transmissions needed to successfully deliver a packet
On the coexistence of cognitive radio ad hoc networks in TV White Space
No full textVery recently, regulatory bodies worldwide have started to approve the dynamic access of unlicensed networks to the TV White Space spectrum. Hence, in the near future, multiple heterogeneous and unlicensed ad hoc networks will coexist within the same geographical area over shared TV White Space. Although heterogeneity and coexistence are not unique to TV White Space scenarios, their distinctive characteristics pose new and challenging issues. In this paper, the problem of the coexistence interference among multiple heterogeneous and secondary ad hoc networks in absence of secondary cooperation is addressed. Specifically, the optimal coexistence strategy, i.e., the coexistence strategy maximizing the expected throughput in presence of coexistence interference, is designed. More in detail, at first, an analytical framework is developed to model the channel selection process for an arbitrary SN as a decision process, where the reward models the data rate achievable on a channel and the cost models the communication overhead for assessing the coexistence interference. Then, we derive the closed-form expression of the expected throughput, which allows us to determine the optimal coexistence strategy. The theoretical analysis is finally validated through a case study
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
Reactive routing for mobile cognitive radio ad hoc networks
No full textAlthough more than a decade has passed from the proposal of the Cognitive Radio paradigm, in these years the research has mainly focused on physical and medium access issues, and few recent works focused on the problem of routing in cognitive networks. This paper addresses such a problem by evaluating the feasibility of reactive routing for mobile cognitive radio ad hoc networks. More specifically, we design a reactive routing protocol for the considered scenario able to achieve three goals: (i) to avoid interferences to primary users during both route formation and data forwarding; (ii) to perform a joint path and channel selection at each forwarder; (iii) to take advantage of the availability of multiple channels to improve the overall performance. Two different versions of the same protocol, referred to as Cognitive Ad-hoc On-demand Distance Vector (CAODV), are presented. The first version exploits inter-route spectrum diversity, while the second one exploits intra-route spectrum diversity. An exhaustive performance analysis of both the versions of the proposed protocol in different environments and network conditions has been carried out via numerical simulations. The results state the suitability of the proposed protocol for small mobile cognitive radio ad hoc networks
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