Imperial College London

ProfessorJulieMcCann

Faculty of EngineeringDepartment of Computing

Professor of Computer Systems
 
 
 
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Contact

 

+44 (0)20 7594 8375j.mccann Website

 
 
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Location

 

258ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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206 results found

Wang H, Zhou G, Bhatia L, Zhu Z, Li W, McCann Jet al., 2020, Energy-neutral and QoS-aware protocol in wireless sensor networks for health monitoring of hoisting systems, IEEE Transactions on Industrial Informatics, Vol: 16, Pages: 5543-5553, ISSN: 1551-3203

Hoisting equipment is core to many industrial systems and therefore their state of health significantly affects production lines and personnel safety; this is especially important in environments such as coal mines. The health of the hoisting system, can be estimated by deploying energy harvesting wireless sensor nodes that monitor the drum surface stress. In this network of sensor devices, it is very costly to send highly sampled data as it causes radio congestion and consumes energy. However, from our experience of sensing hoist systems, we note that the data observed at the upper surface of the hoist is significantly more indicative of the state of health of the whole system, compared with data sensed at the lower surface. Therefore, we need to take advantage of this to optimise the communications of sensor nodes. However, scarce energy can be collected for these devices from the hoist itself, along with the prioritised Quality of Service (QoS) requirements (throughput, delay) of monitoring signals, raises important challenges for energy management. In this paper, we use Lyapunov optimisation techniques and propose an Energy-neutral and QoS-aware Protocol (EQP), including duty cycling and network scheduling to solve it. Extensive simulations show that EQP helps sensor nodes realize consecutive monitoring, and achieve more than 38% utility gain compared with existing strategies.

Journal article

Wu D, Nie X, Asmare E, Arkhipov D, Qin Z, Li R, McCann J, Li Ket al., 2020, Towards distributed SDN: mobility management and flow scheduling in software defined urban IoT, IEEE Transactions on Parallel and Distributed Systems, Vol: 31, Pages: 1400-1418, ISSN: 1045-9219

IEEE The growth of Internet of Things (IoT) devices with multiple radio interfaces has resulted in a number of urban-scale deployments of IoT multinetworks, where heterogeneous wireless communication solutions coexist. Managing the multinetworks for seamless IoT access and handover, especially in mobile environments, is a key challenge. Software-defined networking (SDN) is emerging as a promising paradigm for quick and easy configuration of network devices, but its application in urban-scale multinetworks requiring heterogeneous and frequent IoT access is not well studied. We present UbiFlow that adopts multiple controllers to divide urban-scale SDN into different geographic partitions and achieve distributed control of IoT flows. A distributed hashing based overlay structure is proposed to maintain network scalability and consistency. Based on this UbiFlow overlay structure, the relevant issues pertaining to mobility management such as scalable control, fault tolerance, and load balancing have been carefully studied. The UbiFlow controller differentiates flow scheduling based on per-device requirements and whole-partition capabilities. Therefore, it can present a network status view and optimized selection of access points in multinetworks to satisfy IoT flow requests, while guaranteeing network performance for each partition. Our experiments confirm that UbiFlow can successfully achieve scalable mobility management and robust flow scheduling in IoT multinetworks; e.g. 67.21% throughput improvement, 72.99% reduced delay, and 69.59% jitter improvements, compared with alternative SDN systems.

Journal article

Chen P-Y, Bhatia L, Kolcun R, Boyle D, McCann Jet al., Contact-aware opportunistic data forwarding in disconnected LoRaWAN mobile networks, 40th IEEE International Conference on Distributed Computing Systems, Publisher: IEEE

LoRaWAN is one of the leading Low Power WideArea Network (LPWAN) architectures. It was originally designedfor systems consisting of static sensor or Internet of Things (IoT)devices and static gateways. It was recently updated to introducenew features such as nano-second timestamps which open upapplications to enable LoRaWAN to be adopted for mobile devicetracking and localisation. In such mobile scenarios, devices couldtemporarily lose communication with the gateways because ofinterference from obstacles or deep fading, causing throughputreduction and delays in data transmission. To overcome thisproblem, we propose a new data forwarding scheme. Instead ofholding the data until the next contact with gateways, devices canforward their data to nearby devices that have a higher probabil-ity of being in contact with gateways. We propose a new networkmetric called Real-Time Contact-Aware Expected TransmissionCount (RCA-ETX) to model this contact probability in real-time. Without making any assumption on mobility models, thismetric exploits data transmission delays to model complex devicemobility. We also extend RCA-ETX with a throughput-optimalstochastic backpressure routing scheme and propose Real-TimeOpportunistic Backpressure Collection (ROBC), a protocol tocounter the stochastic behaviours resulting from the dynamicsassociated with mobility. To apply our approaches seamlesslyto LoRaWAN-enabled devices, we further propose two newLaRaWAN classes, namely Modified Class-C and Queue-basedClass-A. Both of them are compatible with LoRaWAN Class-Adevices. Our data-driven experiments, based on the London busnetwork, show that our approaches can reduce data transmissiondelays up to25%and provide a53%throughput improvementin data transfer performance.

Conference paper

Benkhelifa F, ElSawy H, McCann JA, Alouini M-Set al., 2020, Recycling cellular energy for self-sustainable IoT networks: a spatiotemporal study, IEEE Transactions on Wireless Communications, Vol: 19, Pages: 2699-2712, ISSN: 1536-1276

This paper investigates the self-sustainability of an overlay Internet of Things (IoT) network that relies on harvesting energy from a downlink cellular network. Using stochastic geometry and queueing theory, we develop a spatiotemporal model to derive the steady state distribution of the number of packets in the buffers and energy levels in the batteries of IoT devices given that the IoT and cellular communications are allocated disjoint spectrum. Particularly, each IoT device is modelled via a two-dimensional discrete-time Markov Chain (DTMC) that jointly tracks the evolution of the data buffers and energy battery. In this context, stochastic geometry is used to derive the energy generation at the batteries and the packet transmission success probability from buffers taking into account the mutual interference from other active IoT devices. To this end, we show the Pareto-Frontiers of the sustainability region, which define the network parameters that ensure stable network operation and finite packet delay. Furthermore, the spatially averaged network performance, in terms of transmission success probability, average queueing delay, and average queue size are investigated. For self-sustainable networks, the results quantify the required buffer size and packet delay, which are crucial for the design of IoT devices and time critical IoT applications.

Journal article

Spina A, Breza M, Dulay N, McCann Jet al., XPC: fast and reliable synchronous transmission protocols for 2-phase commit and 3-phase commit, The 2020 International Conference on Embedded Wireless Systems and Networks, Publisher: ACM

The improvement of software abstractions and frame-works for programmers is one of the major challenges forthe engineering of reliable and efficient wireless sensing sys-tems. We address this challenge with X Process Commit(XPC), an atomic commit protocol framework, andHybrid,a Synchronous Transmission (ST) communication approach.Hybridexploits the reliability of Glossy and the speed ofChaos, two Synchronous Transmission primitives, to getlower latency and higher reliability than either on their own.Hybridis a general approach that can provide reliable com-munication for any round based protocol. We use XPC andHybridto build the classical 2-phase and 3-phase commitprotocols. Through extensive experimentation, we comparethe performance of the 2-phase and 3-phase commit proto-cols when they useHybrid, Glossy, and Chaos for commu-nication. Our results show thatHybridis more robust thanChaos to radio interference, with almost 100% reliability in anetwork of nodes suffering from moderate radio interference,13% to 50% faster than Glossy, and has comparable over-heads to other state of the art ST atomic commit approachesA2/Synchrotron.

Conference paper

Yu W, McCann J, Zhang C, 2019, Efficient pairwise penetrating-rank similarity retrieval, ACM Transactions on the Web, Vol: 13, Pages: 1-52, ISSN: 1559-1131

Many web applications demand a measure of similarity between two entities, such as collaborative filtering, web document ranking, linkage prediction, and anomaly detection. P-Rank (Penetrating-Rank) has been accepted as a promising graph-based similarity measure, as it provides a comprehensive way of encoding both incoming and outgoing links into assessment. However, the existing method to compute P-Rank is iterative in nature and rather cost-inhibitive. Moreover, the accuracy estimate and stability issues for P-Rank computation have not been addressed. In this article, we consider the optimization techniques for P-Rank search that encompasses its accuracy, stability, and computational efficiency. (1) The accuracy estimation is provided for P-Rank iterations, with the aim to find out the number of iterations, k, required to guarantee a desired accuracy. (2) A rigorous bound on the condition number of P-Rank is obtained for stability analysis. Based on this bound, it can be shown that P-Rank is stable and well-conditioned when the damping factors are chosen to be suitably small. (3) Two matrix-based algorithms, applicable to digraphs and undirected graphs, are, respectively, devised for efficient P-Rank computation, which improves the computational time from O(kn3) to O(υ n2+υ6) for digraphs, and to O(υn2) for undirected graphs, where n is the number of vertices in the graph, and υ (≪ n) is the target rank of the graph. Moreover, our proposed algorithms can significantly reduce the memory space of P-Rank computations from O(n2) to O(υn+υ4) for digraphs, and to O(υ n) for undirected graphs, respectively. Finally, extensive experiments on real-world and synthetic datasets demonstrate the usefulness and efficiency of the proposed techniques for P-Rank similarity assessment on various networks.

Journal article

Mcgrane SJ, Acuto M, Artioli F, Chen PY, Comber R, Cottee J, Farr-Wharton G, Green N, Helfgott A, Larcom S, Mccann JA, O'Reilly P, Salmoral G, Scott M, Todman LC, van Gevelt T, Yan Xet al., 2019, Scaling the nexus: Towards integrated frameworks for analysing water, energy and food, Geographical Journal, Vol: 185, Pages: 419-431, ISSN: 0016-7398

The emergence of the water-energy-food (WEF) nexus has resulted in changes to the way we perceive our natural resources. Stressors such as climate change and population growth have highlighted the fragility of our WEF systems, necessitating integrated solutions across multiple scales. While a number of frameworks and analytical tools have been developed since 2011, a comprehensive WEF nexus tool remains elusive, hindered in part by our limited data and understanding of the interdependencies and connections across the WEF systems. To achieve this, the community of academics, practitioners and policy-makers invested in WEF nexus research are addressing several critical areas that currently remain as barriers. First, the plurality of scales (e.g., spatial, temporal, institutional, jurisdictional) necessitates a more comprehensive effort to assess interdependencies between water, energy and food, from household to institutional and national levels. Second, and closely related to scale, a lack of available data often hinders our ability to quantify physical stocks and flows of resources. Overcoming these barriers necessitates engaging multiple stakeholders, and using experiences and local insights to better understand nexus dynamics in particular locations or scenarios, and we exemplify this with the inclusion of a UK-based case study on exploring the nexus in a particular geographical area. We elucidate many challenges that have arisen across nexus research, including the impact of multiple scales in operation, and concomitantly, what impact these scales have on data accessibility. We assess some of the critical frameworks and tools that are applied by nexus researchers and articulate some of the steps required to develop from nexus thinking to an operationalisable concept, with a consistent focus on scale and data availability.

Journal article

Altherwy YN, Elmallah ES, McCann JA, 2019, Two-terminal connectivity in UWSN probabilistic graphs: A polynomial time algorithm: Poster abstract, Pages: 444-445

© 2019 Authors. We investigate the likelihood that two nodes are connected in an Underwater Wireless Sensor Network (UWSN) where nodes are floating freely with the underwater currents and the location of nodes at any given time can only be determined in a probabilistic fashion. This problem is #P-hard, thus, we propose HB-Conn2, an algorithm that returns an exact solution in polynomial time when applied on a set of node-disjoint (s, t)-paths.

Conference paper

Zhao C, Yang S, McCann JA, 2019, On the data quality in privacy-preserving mobile crowdsensing systems with untruthful reporting, IEEE Transactions on Mobile Computing, Pages: 1-1, ISSN: 1536-1233

The proliferation of mobile smart devices with ever improving sensing capacities means that human-centric Mobile Crowdsensing Systems (MCSs) can economically provide a large scale and flexible sensing solution. The use of personal mobile devices is a sensitive issue, therefore it is mandatory for practical MCSs to preserve private information (the user's true identity, precise location, etc.) while collecting the required sensing data. However, well intentioned privacy protection techniques also conceal autonomous, or even malicious, behaviors of device owners (termed as self-interested), where the objectivity and accuracy of crowdsensing data can therefore be severely threatened. The issue of data quality due to untruthful reporting in privacy-preserving MCSs has been yet to produce solutions. Bringing together game theory, algorithmic mechanism design, and truth discovery, we develop a mechanism to guarantee and enhance the quality of crowdsensing data without jeopardizing the privacy of MCS participants. Together with solid theoretical justifications, we evaluate the performance of our proposal with extensive real-world MCS trace-driven simulations. Experimental results demonstrate the effectiveness of our mechanism on both enhancing the quality of the crowdsensing data and eliminating the motivation of MCS participants, even when their privacy is well protected, to report untruthfully.

Journal article

Qin Z, Liu Y, Li GY, McCann JAet al., 2019, Performance analysis of clustered LoRa networks, IEEE Transactions on Vehicular Technology, Vol: 68, Pages: 7616-7629, ISSN: 0018-9545

In this paper, we investigate the uplink transmission performance of low-power wide-area (LPWA) networks with regards to coexisting radio modules. We adopt the long-range (LoRa) radio technique as an example of the network of focus, even though our analysis can be easily extended to other situations. We exploit a new topology to model the network, where the node locations of LoRa follow a Poisson cluster process while other coexisting radio modules follow a Poisson point process. Unlike most of the performance analysis based on stochastic geometry, we take noise into consideration. More specifically, two models, with a fixed and a random number of active LoRa nodes in each cluster, respectively, are considered. To obtain insights, both the exact and simple approximated expressions for coverage probability are derived. Based on them, area spectral efficiency and energy efficiency are obtained. From our analysis, we show how the performance of LPWA networks can be enhanced by adjusting the density of LoRa nodes around each LoRa receiver. Moreover, the simulation results unveil that the optimal number of active LoRa nodes in each cluster exists to maximize the area spectral efficiency.

Journal article

Li K, Benkhelifa F, McCann J, Resource allocation for non-orthogonal multiple access (NOMA) enabled LPWA networks, IEEE GLOBECOM 2019, Publisher: IEEE

In this paper, we investigate the resource allocationfor uplink non-orthogonal multiple access (NOMA) enabledlow-power wide-area (LPWA) networks to support the massiveconnectivity of users/nodes. Here, LPWA nodes communicatewith a central gateway through resource blocks like channels,transmission times, bandwidths, etc. The nodes sharing thesame resource blocks suffer from intra-cluster interference andpossibly inter-cluster interference, which makes currentLPWAnetworks unable to support the massive connectivity. Usingtheminimum transmission rate metric to highlight the interferencereduction that results from the addition of NOMA, and whileassuring user throughput fairness, we decompose the minimumrate maximization optimization problem into three sub-problems.First, a low-complexity sub-optimal nodes clustering scheme isproposed assigning nodes to channels based on their normalizedchannel gains. Then, two types of transmission time allocationalgorithms are proposed that either assure fair or unfair trans-mission time allocation between LPWA nodes sharing the samechannel. For a given channel and transmission time allocation, wefurther propose an optimal power allocation scheme. Simulationevaluations demonstrate approximately100dBimprovement ofthe selected metric for a single network with4000active nodes.

Conference paper

Benkhelifa F, Qin Z, McCann J, 2019, Minimum throughput maximization in LoRa networks powered by ambient energy harvesting, ICC 2019 - 2019 IEEE International Conference on Communications (ICC), Publisher: Institute of Electrical and Electronics Engineers, ISSN: 1550-3607

In this paper, we investigate the uplink transmissions in low-power wide-area networks (LPWAN) where the users are self-powered by the energy harvested from the ambient environment. Demonstrating their potential in supporting diverse Internet-of-Things (IoT) applications, we focus on long range (LoRa) networks where the LoRa users are using the harvested energy to transmit data to a gateway via different spreading codes. Precisely, we study the throughput fairness optimization problem for LoRa users by jointly optimizing the spreading factor (SF) assignment, energy harvesting (EH) time duration, and the transmit power of LoRa users. First, through examination of the various permutations of collisions among users, we derive a general expression of the packet collision time between LoRa users, which depends on the SFs and EH duration requirements. Then, after reviewing prior SF allocation work, we develop two types of algorithms that either assure fair SF assignment indeed purposefully `unfair' allocation schemes for the LoRa users. Our results unearth three new findings. Firstly, we demonstrate that, to maximize the minimum rate, the unfair SF allocation algorithm outperforms the other approaches. Secondly, considering the derived expression of packet collision between simultaneous users, we are now able to improve the performance of the minimum rate of LoRa users and show that it is protected from inter-SF interference which occurs between users with different SFs. That is, imperfect SF orthogonality has no impact on minimum rate performance. Finally, we have observed that co-SF interference is the main limitation in the throughput performance, and not the energy scarcity.

Conference paper

Tomic I, Breza MJ, Jackson G, Bhatia L, McCann JAet al., 2019, Design and evaluation of jamming resilient cyber-physical systems, IEEE International Conference on Cyber, Physical and Social Computing (CPSCom 2018), Publisher: IEEE

There is a growing movement to retrofit ageing,large scale infrastructures, such as water networks, with wirelesssensors and actuators. Next generation Cyber-Physical Systems(CPSs) are a tight integration of sensing, control, communication,computation and physical processes. The failure of any one ofthese components can cause a failure of the entire CPS. Thisrepresents a system design challenge to address these interde-pendencies. Wireless communication is unreliable and prone tocyber-attacks. An attack upon the wireless communication of CPSwould prevent the communication of up-to-date information fromthe physical process to the controller. A controller without up-to-date information is unable to meet system’s stability and perfor-mance guarantees. We focus on design approach to make CPSssecure and we evaluate their resilience to jamming attacks aimedat disrupting the system’s wireless communication. We considerclassic time-triggered control scheme and various resource-aware event-triggered control schemes. We evaluate these ona water network test-bed against three jamming strategies:constant, random, and protocol aware. Our test-bed results showthat all schemes are very susceptible to constant and randomjamming. We find that time-triggered control schemes are justas susceptible to protocol aware jamming, where some event-triggered control schemes are completely resilient to protocolaware jamming. Finally, we further enhance the resilience ofan event-triggered control scheme through the addition of adynamical estimator that estimates lost or corrupted data.

Conference paper

Qin Z, Li FY, Li GY, McCann JA, Ni Qet al., 2019, Low-power wide-area networks for sustainable IoT, IEEE Wireless Communications, Vol: 26, Pages: 140-145, ISSN: 1536-1284

LPWA networks are attracting extensive attention because of their ability to offer low-cost and massive connectivity to IoT devices distributed over wide geographical areas. This article provides a brief overview of the existing LPWA technologies and useful insights to aid the large-scale deployment of LPWA networks. In particular, we first review the currently competing candidates of LPWA networks, such as NB-IoT and LoRa, in terms of technical fundamentals and large-scale deployment potential. Then we present two implementation examples of LPWA networks. By analyzing the field-test results, we identify several challenges that prevent LPWA technologies from moving from theory to wide-spread practice.

Journal article

Puliafito A, Gangopadhyay A, Ganti R, McCann JAet al., 2019, Message from the SMARTCOMP 2019 conference chairs

Conference paper

Yu W, Lin X, Zhang W, Pei J, McCann JAet al., 2019, SimRank*: effective and scalable pairwise similarity search based on graph topology, VLDB Journal, Vol: 28, Pages: 401-426, ISSN: 1066-8888

Given a graph, how can we quantify similarity between two nodes in an effective and scalable way? SimRank is an attractive measure of pairwise similarity based on graph topologies. Its underpinning philosophy that “two nodes are similar if they are pointed to (have incoming edges) from similar nodes” can be regarded as an aggregation of similarities based on incoming paths. Despite its popularity in various applications (e.g., web search and social networks), SimRank has an undesirable trait, i.e., “zero-similarity”: it accommodates only the paths of equal length from a common “center” node, whereas a large portion of other paths are fully ignored. In this paper, we propose an effective and scalable similarity model, SimRank*, to remedy this problem. (1) We first provide a sufficient and necessary condition of the “zero-similarity” problem that exists in Jeh and Widom’s SimRank model, Li et al. ’s SimRank model, Random Walk with Restart (RWR), and ASCOS++. (2) We next present our treatment, SimRank*, which can resolve this issue while inheriting the merit of the simple SimRank philosophy. (3) We reduce the series form of SimRank* to a closed form, which looks simpler than SimRank but which enriches semantics without suffering from increased computational overhead. This leads to an iterative form of SimRank*, which requires O(Knm) time and O(n2) memory for computing all (n2) pairs of similarities on a graph of n nodes and m edges for K iterations. (4) To improve the computational time of SimRank* further, we leverage a novel clustering strategy via edge concentration. Due to its NP-hardness, we devise an efficient heuristic to speed up all-pairs SimRank* computation to O(Knm~) time, where m~ is generally much smaller than m. (5) To scale SimRank* on billion-edge graphs, we propose two memory-efficient single-source algorithms, i.e., ss-gSR* for geometric SimRank*, and ss-eSR* for exp

Journal article

Liu X, Qin Z, Gao Y, McCann JAet al., 2019, Resource allocation in wireless powered IoT networks, IEEE Internet of Things Journal, Vol: 6, Pages: 4935-4945, ISSN: 2327-4662

In this paper, the efficient resource allocation for the uplink transmission of wireless powered Internet of Things (IoT) networks is investigated. We adopt LoRa technology as an example in the IoT network, but this paper is still suitable for other communication technologies. Allocating limited resources, like spectrum and energy resources, among a massive number of users faces critical challenges. We consider grouping wireless powered IoT users into available channels first and then investigate power allocation for users grouped in the same channel to improve the network throughput. Specifically, the user grouping problem is formulated as a many to one matching game. It is achieved by considering IoT users and channels as selfish players which belong to two disjoint sets. Both selfish players focus on maximizing their own utilities. Then we propose an efficient channel allocation algorithm (ECAA) with low complexity for user grouping. Additionally, a Markov decision process is used to model unpredictable energy arrival and channel conditions uncertainty at each user, and a power allocation algorithm is proposed to maximize the accumulative network throughput over a finite-horizon of time slots. By doing so, we can distribute the channel access and dynamic power allocation local to IoT users. Numerical results demonstrate that our proposed ECAA algorithm achieves near-optimal performance and is superior to random channel assignment, but has much lower computational complexity. Moreover, simulations show that the distributed power allocation policy for each user is obtained with better performance than a centralized offline scheme.

Journal article

Tomic I, Breza M, McCann J, Jamming-resilient control and communication framework for cyber physical systems, Living in the Internet of Things 2019, Publisher: IET

The control and monitoring of large infrastructure installations is becoming smarter, cheaper to run and easier to managethrough the use of wireless sensor and actuator networks (WSANs). Cyber Physical Systems (CPSs)are the combination of cyber sensing via WSANs and physical control. The problem withthe use of WSANs in CPSs is that they make the whole system being controlled exposed to the world andvulnerable to theft or cyber-attacks.In this article we examine the failure of CPS infrastructure due to intelligent radio jamming.The intelligent jammer employs a protocol-aware jamming strategy to learn the transmission period of a sensor device.It then broadcasts noise to disrupt the wireless communication and destabilise the CPS.Wepresent a CPS control and communication approachto counter thethreat of intelligentradio jamming. The approach exploitsthe properties of the event-based controlstrategy combined with a reservation-based communication protocolthat employs obfuscation. We usea physical model of a water distribution networkto demonstrate that the approachis resilient to an intelligent jamming attack, it is able to continue normaloperationof the systemand maintain the desired level of performance while achieving low overheads.

Conference paper

McCann JA, Picco GP, Gluhak A, Johansson KH, Törngren M, Gide Let al., 2019, Connected things connecting Europe, Communications of the ACM, Vol: 62, Pages: 46-51, ISSN: 0001-0782

Journal article

Benkhelifa F, ElSawy H, McCann J, Alouini M-Set al., 2019, Recycling cellular downlink energy for overlay self-sustainable IoT networks, 2018 IEEE Global Communications Conference: Wireless Communications, Publisher: IEEE

This paper investigates the self-sustainability of anoverlay Internet of Things (IoT) network that relies on harvest-ing energy from a downlink cellular network. Using stochasticgeometry and queueing theory, we develop a spatiotemporalmodel to derive the steady state distribution of the numberof packets in the buffers and energy levels in the batteries ofIoT devices given that the IoT and cellular communicationsare allocated disjoint spectrum. Particularly, each IoT deviceis modeled via a two-dimensional discrete-time Markov Chain(DTMC) that jointly tracks the evolution of data buffer andenergy battery. In this context, stochastic geometry is used toderive the energy generation at the batteries and the packettransmission probability from buffers taking into account themutual interference from other active IoT devices. To this end,we show the Pareto-Frontiers of the sustainability region, whichdefines the network parameters that ensure stable networkoperation and finite packet delay. The results provide severalinsights to design self-sustainable IoT networks.Index Terms—Spatiotemporal models, stochastic geometry,queuing theory, energy harvesting, packet transmission successprobability, two-dimensional discrete-time Markov chain, sta-bility conditions.

Conference paper

McCann J, Zheng Q, 2019, Message from the Program Chairs: ICPADS 2018, Proceedings of the International Conference on Parallel and Distributed Systems, Pages: xxii-xxiii, ISSN: 1521-9097

Conference paper

Fu A, Tomic I, McCann J, Asynchronous sampling for decentralized periodic event-triggered control, 2019 American Control Conference, Publisher: IEEE

Decentralized periodic event-triggered control(DPETC) strategies are an attractive solution for wireless cyber-physical systems where resources such as network bandwidthand sensor power are scarce. This is because these strategieshave the advantage of preventing unnecessary data transmis-sions and therefore reduce bandwidth and energy requirements,however the sensor sampling regime remains synchronous.Typically the action of sampling leads almost immediately toa transmission on an event being detected. If the sampling issynchronous, multiple transmission requests may be raised atthe same time which further leads to bursty traffic patterns.Bursty traffic patterns are critical to the DPETC systemsperformance as the probability of collisions and the amount ofrequested bandwidth resources become high ultimately causingdelays. In this paper, we propose an asynchronous samplingscheme for DPETC. The scheme ensures that at each samplingtime, no more than one transmission request can be generatedwhich prevents the occurrence of network traffic collision.At the same time, for the DPETC system with asynchronoussampling a pre-designed global exponential stability andL2-gain performance can still be guaranteed. We illustrate theeffectiveness of the approach through a numerical example.

Conference paper

Jiang S, Cao J, McCannt JA, Yang Y, Liu Y, Wang X, Deng Yet al., 2019, Privacy-preserving and Efficient Multi-keyword Search Over Encrypted Data on Blockchain, 2nd IEEE International Conference on Blockchain (Blockchain), Publisher: IEEE COMPUTER SOC, Pages: 405-410

Conference paper

Webster M, Breza M, Dixon C, Fisher M, McCann Jet al., 2019, Formal verification of synchronisation, gossip and environmental effects for wireless sensor networks, Electronic Communications of the EASST, Vol: 76, ISSN: 1863-2122

The Internet of Things (IoT) promises a revolution in the monitoring and control of a wide range of applications, from urban water supply networks and precision agriculture food production, to vehicle connectivity and healthcare monitoring. For applications in such critical areas, control software and protocols for IoT systems must be verified to be both robust and reliable. Two of the largest obstacles to robustness and reliability in IoT systems are effects on the hardware caused by environmental conditions, and the choice of parameters used by the protocol. In this paper we use probabilistic model checking to verify that a synchronisation and dissemination protocol for Wireless Sensor Networks (WSNs) is correct with respect to its requirements, and is not adversely affected by the environment. We show how the protocol can be converted into a logical model and then analysed using the probabilistic model-checker, PRISM. Using this approach we prove under which circumstances the protocol is guaranteed to synchronise all nodes and disseminate new information to all nodes. We also examine the bounds on synchronisation as the environment changes the performance of the hardware clock, and investigate the scalability constraints of this approach.

Journal article

Sevegnani M, Kabac M, Calder M, McCann JAet al., 2018, Modelling and Verification of Large-Scale Sensor Network Infrastructures, 23rd International Conference on Engineering of Complex Computer Systems (ICECCS), Publisher: IEEE, Pages: 71-81

Conference paper

Calder M, Dobson S, Fisher M, McCann Jet al., 2018, Making sense of the world: Framing models for trustworthy sensor-driven systems, Computers, Vol: 7, ISSN: 2073-431X

Sensor-driven systems provide data and information that facilitate real-time decision-making and autonomous actuation, as well as enable informed policy choices. However, can we be sure that these systems work as expected? Can we model them in a way that captures all the key issues? We define two concepts: frames of reference and frames of function that help us organise models of sensor-based systems and their purpose. Examples from a smart water distribution network illustrate how frames offer a lens through which to organise and balance multiple views of the system. Frames aid communication between modellers, analysts and stakeholders, and distinguish the purpose of each model, which contributes towards our trust that the system fulfils its purpose.

Journal article

Shi F, Qin Z, Wu D, McCann Jet al., 2018, Effective truth discovery and fair reward distribution for mobile crowdsensing, Pervasive and Mobile Computing, Vol: 51, Pages: 88-103, ISSN: 1574-1192

By leveraging the sensing capabilities of consumer mobile devices, mobile crowdsensing (MCS) systems enable a number of new applications for Internet of Things (IoT), such as traffic management, environmental monitoring, and localisation. However, the sensing data collected from the crowd workers are of various qualities, making it difficult to discover the ground truth and maintain the fairness of incentivisation schemes. In this paper, we propose a truth discovery algorithm based on a two-stage Maximum Likelihood Estimator (MLE), which explicitly characterises the heterogeneous sensing capabilities of the crowd and is able to estimate ground truth accurately using only a small amount of data from IoT infrastructures. Moreover, based on the truth discovery algorithm, two reward distribution schemes, LRDS and MRDS, are proposed to ensure fairness of rewarding the crowd according to their effort levels. We evaluate the estimation accuracy of the truth discovery algorithm and the fairness of the reward distribution schemes using both simulations and real-world MCS campaigns. The evaluation results indicate that the proposed methods achieve superior performance compared with state-of-the-art methods in terms of estimation accuracy and fairness of reward distribution.

Journal article

Bhatia L, Tomic I, McCann J, 2018, LPWA-MAC - a low power wide area network MAC protocol for cyber-physical system, The 16th ACM Conference on Embedded Networked Sensor Systems (SenSys 2018), Publisher: ACM, Pages: 361-362

Low-Power Wide-Area Networks (LPWANs) are being successfully used for the monitoring of large-scale systems that are delay-tolerant and which have low-bandwidth requirements. The next step would be instrumenting these for the control of Cyber-Physical Systems (CPSs) distributed over large areas which require more bandwidth, bounded delays and higher reliability or at least more rigorous guarantees therein. This paper presents LPWA-MAC, a novel Low Power Wide-Area network MAC protocol, that ensures bounded end-to-end delays, high channel utility and supports many of the different traffic patterns and data-rates typical of CPS.

Conference paper

Bhatia L, Boyle D, McCann J, 2018, Aerial interactions with wireless sensors, The 16th ACM Conference on Embedded Networked Sensor Systems (SenSys 2018), Pages: 373-374

Sensing systems incorporating unmanned aerial vehicles have the potential to enable a host of hitherto impractical monitoring applications using wireless sensors in remote and extreme environments. Their use as data collection and power delivery agents can overcome challenges such as poor communications reliability in difficult RF environments and maintenance in areas dangerous for human operatives. Aerial interaction with wireless sensors presents some interesting new challenges, including selecting or designing appropriate communications protocols that must account for unique practicalities like the effects of velocity and altitude. This poster presents a practical evaluation of the effects of altitude when collecting sensor data using an unmanned aerial vehicle. We show that for an otherwise disconnected link over a long distance (70m), by increasing altitude (5m) the link is created and its signal strength continues to improve over tens of metres. This has interesting implications for protocol design and optimal aerial route planning.

Conference paper

Kartakis S, Fu A, Mazo M, McCann JAet al., 2018, Communication schemes for centralized and decentralized event-triggered control systems, IEEE Transactions on Control Systems Technology, Vol: 26, Pages: 2035-2048, ISSN: 1063-6536

Energy constraint long-range wireless sensor/actuator-based solutions are theoretically the perfect choice to support the next generation of city-scale cyber-physical systems. Traditional systems adopt periodic control which increases network congestion and actuations while burdens the energy consumption. Recent control theory studies overcome these problems by introducing aperiodic strategies, such as event-triggered control (ETC). In spite of the potential savings, these strategies assume actuator continuous listening, while ignoring the sensing energy costs. In this paper, we fill this gap, by enabling sensing and actuator listening duty cycling and proposing two innovative medium access control protocols for three decentralized ETC approaches. A laboratory experimental test bed, which emulates a smart water network, was modeled and extended to evaluate the impact of system parameters and the performance of each approach. Experimental results reveal the predominance of the decentralized ETC against the classic periodic control either in terms of communication or actuation by promising significant system lifetime extension.

Journal article

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