A strategy for deploying diverse sensor-based networks as an evolution towards integrated Internet of Things and Future Internet Andrej Mihailovic, Member, IEEE, Marko Simeunović, Member, IEEE, Nedjeljko Lekić, Member, IEEE, Milica Pejanović-Djurisić, Member, IEEE
Abstract — Buying an off-the-shelf sensor or actuator device has become a common practice with individual developers or universities that are keen on exploring ways of flexibly building networks for increasing possibilities of use. Their objective might not be on a targeted single application or an integrated product, but by conducing trials, suitable development and research, they explore novel networking opportunities and fit them to suitable applications. Internet of Things is a concept that promises a world of interconnected IP entities to be facilitated by new underlying capabilities in the Internet. This new initiative meets the vast population of Wireless Sensor (and actuator) Networks that have been deployed in an ever-increasing ranges of applications. The paper shows an understanding of how topics can be coherently combined behind a target for developing a regional and multi-application system and grouping the research topics that would foster its further development. Keywords — Internet of Things, Wireless Sensor Networks, Future Internet.
I. INTRODUCTION research, development and commercialisation have stepped into an era where areas of applications, types of network components and architectures are rapidly changing from the typical models found in the traditional commercial telecommunications systems and the Internet. One of the catalysts of the change is represented in the proliferation of ranges of small hardware suited to sensing, actuating and communicating purposes coupled with the opportunities for numerous applications. Internet of Things (IoT) concept has emerged and gained momentum over the past years representing a direction for converging on these novel opportunities. Surge of IoT applications is anticipated to be facilitated by an almost arbitrary synthesis of a grand scale population of Internet-connected devices. Consequently, Future Internet (FI) as a global transformation initiative for IP-based communications is to
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Work is funded by European Union project Fore-Mont as a part of Seventh Framework Programme (Grant Agreement No. 315970 FP7REGPOT-CT-2013) http://www.foremont.ac.me. All authors are with the Research Centre for ICT, Faculty of Electrical Engineering, University of Montenegro, Bulevar Dzordza Vasingtona bb, 81000 Podgorica, Montenegro (e-mails:
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embrace the models and properties of the IoT as the novel Internet end-points and domains. Historically, pioneering visions on IoT considered how various Wireless Sensor Networks (WSNs) would evolve in terms of acquiring IP reachability [1],[2],[3]. This dimension in IoT development is a significant one as WSNs deployment has gained energy and its critical issue is focused on the implications of diverse functional constrains of devices, e.g. sensor nodes, which are often functionally limited to act as standard IP hosts. Fundamental features in transforming the WSNs as independent networks into IoT segments are centred on gateway functionalities, formation of WSNs nodes and means of representing the data as an IP-based web service. Another dimension of the IoT development conceives the “things” to function as IP capable objects from the start of the design, i.e. as IP hosts. Ideally, “things” would be assigned a unique IP(v6) address and autonomously connect to the Internet. Hence, a sensor that is an IoT/”thing” would be functionally capable of hosting sufficient IP protocol functions. There is a collection of topics that bolster integration of IoT into the today’s Internet: advances in machine-to-machine communications, magnitude of IPv6 addresses, protocols suited for PHY and MAC layers [4], IP stack/protocol convergences [5]…Many more augmenting issues could be added: Radio Frequency Identification (RFID) tags in various objects as the triggers for early IoT visions [6], automations, various applications based on sensors, FI as embracing the population of new “lightweight” IP hosts… This vastness of space in worldwide IoT development has generated a great surge in surveys, initiatives, practical solutions, visions, emerging standards [7],[8]. An important property of the expansion and deployment of all of the systems based on small constrained devices is that their creation and spreading is often driven not by the bare technological impetus, but rather, by the purpose and commercial viability of the specific applications. And the application areas are growing: transport, medical, agriculture, infrastructure-based, city-wide, energy-related, home and industrial automations, etc [8]. In other words, growth of IoT or WSNs that achieve IP reachability, might not follow the objectives that expanded the Internet, that is, interconnections of IP hosts. Nor will the components of the systems be produced or be chosen by developers solely for having IP reachability that is expected in IoT definitions, e.g. a sensor might be chosen for optimal performance factors, cost and vendor-related
Figure 1. Framework Architecture of Integrated WSNs characteristics. Hence, we speculate that the path towards IoT proliferation might be partly subject to transformations of WSNs in terms of IP reachability as mentioned above and subject to models of connecting to the Internet. At the same time, fully IP capable “things”, will assimilate in the global connectivity of IP hosts. Rendering the benefits of the new era of interconnected small constrained devices is the direction towards the FI that ought to embrace this diversity of data sources, models and IP hosts and solve it at the levels of: IP interconnections, higher layer visibility, domain representations, geographical and topological interpretations, control and management issues, data collection, security, etc. This paper presents a practically-founded strategy for expanding diverse WSNs towards a generic working environment for IoT and FI unravelling. The immediate context is local and regional development of WSNs applications under governance of our university. Motivations are in advancing the research, technological, societal and commercial capacities. We aspire to offer an insight into our practical development perspective (in Section II) and our contribution in positioning towards FI. There are already large scale implementations of systems for IoT-based FI, e.g. EU projects under FI-WARE initiative (www.fi-ware.org) or SmartSantader (www.smar-tsantander.eu) that provide guidance for our development. In Section III we give a convergence on some key research topics subject to the realm of our objective. II. INTERPRETING FUNCTIONAL COMPONENTS OF WSNS A. Fitting diverse segments together Diverse network components and applications, in our university example, are due to particular deployment plans. We have started early pilot WSN implementations for agriculture and meteorological monitoring with plans for further expansions, internal testing of components and planned progress in other areas such as smart cities and transport. The development is carried out via collaborations between the university and the private sector for enhancing productions or monitoring. Hence, acquisition of equipment, architecture of each WSN and the application characteristics reflect the needs of the particular purpose. It might not be practical to start with IP capability in devices, as the key development objective.
The objective can be summarised in the framework architecture shown in Figure 1, being an integration framework that groups various WSNs, independent sensors/”things”, connected via Internet using different wireless technologies, to a local-area network hosting a development platform. The objective is on a centrally coordinated system of heterogeneous components for advancing technologies, deploying new applications, commercialisations, expansion of components, in parallel with, conducting targeted research and evolving towards transformation into IoT as part of the FI. B. Development perspective Focusing on the practical aspects of developing the system centred on the architecture of Figure 1, we present a perspective on assessing some of its components: 1) Working Platform: this generic term groups the centralised features that would enable coordination of diverse segments. As there is an extensive state-of-the-art available and working solutions, we mark the importance of having a dedicated working platform for development and research purposes in case of random WSNs/”thing” being coordinated, different applications and various data being transferred. The service of coordination will have the properties of application-and-coordination-IP-cloud mark-ing its work-in-progress purpose. The cloud features operate between the levels bounded by forms of generic APIs: i) of data collections (i.e. devices), ii) processing middleware, and, iii) as an interface to applications [11]. The platform manages and controls aspects of independent WSNs and common resources such as communication links, processing and monitoring powers. The centralised approach is an economically optimal strategy for utilising university’s research and development resources as well as for producing commercial applications. 2) (Constrained) devices (sensors, actuators…): choosing a device or clusters can be subject to technological savviness, application requirements, cost, relationship with vendor(s), etc. An example classification of sensors’ performance factors [9] uses processing capabilities based on commercially available values for chips and design cores. Other classification approaches for IoT-enabled devices granulate application requirements [10] (e.g. mobility, reliability, security…). We see more axis of classification subject to the ease of deployment:
plug&play/manual/programmability, standalone/clustered/ gateway, extent of IP stack if any, higher layer features, multiple wireless interfaces, etc. These determine how a device integrates into a working platform. 3) Connectivity: we note the randomness of issues related to connectivity of devices and overall interconnections in a coordinated systems. As depicted in Figure 1, wireless technologies can vary subject to how much a node is stand-alone or part of a cluster. There is also a design consideration of the physical characteristics of wireless technologies, then, their implications on data delivery. Another angle is to observe the side of coordination of the overall system and how connectivity of devices is accounted for: by integrating a whole WSN segment or independent devices (e.g. via IP or MAC addresses, SIM card…). Finally, practical deployment issues such as characteristics of physical terrain might superimpose a choice on wireless technology. 4) Data acquisition: in a diverse IoT/WSN environment that is centrally coordinated, data acquisition becomes a complex issue of harnessing various sources and acquisition procedures. These can be periodical, pulling, then, sent via different wireless technologies and network segments, using different protocols, etc. It is seems almost inevitable that data filtering features are implemented for reasons of processing and scalability that would then present the data to applications (e.g. APIs/enablers) or to administrators/users. 5) Configuration: Processing capabilities in microcontrollers of constrained devices and their adaptations subject to external/centralised commands is a property that in many ways determines efficiency of integrations and operations. Many current sensors are manually configured with limited processing capabilities. Development needs can seek embedding of multiple codes and online configurations (e.g. routing instructions, periods of data reporting, stack layout, IP addresses…). 6) Other: There is a plentiful of other multidisciplinary set of challenges. We single out issues of security and functional independence of WSN segments and IoT populations (e.g. via self-organisation and autonomic behaviour) as critical development issues. III. POSITIONING OF RESEARCH A. Integration Path towards IoT as part of FI Section I extracted two dimensions of the progress towards IoT and FI: embracing evolutions of today’s WSNs towards IP connectivity, and/or, surge in IP “things”. We dwell at the IoT vision “IP address for every device” with a question: what would be the dominant level of identification of devices’/networks’ data or roles in the future? The past has shown that IP addressing used for IP hosts is often an intermediary and practical network layer locator for global identifications that are resolved at higher layers (e.g. email addresses, URLs, sessions user names). This works well in the current Internet and telecoms models that are built to facilitate “human-to-human” or “human-to-server” communication model [13]. In the proliferation of IoT, “device-to-device/human/database/au-
tomation…” communications and vice versa, characterise the new model. This data or roles are “personified” by the purpose, data representation and feeding to the various configurations and needs of applications. In the transformation towards FI that would accommodate various IoTs, a design consideration can be the ubiquitous level at which data or roles are visible [8]. In some WSNs, data delivered is presented as an application-specific web service [11]. Or, WSNs have interfacing features to the Internet via gateways using various models of transition [2]: as applications level gateways or, in some cases, as IP access routers. In the latter case, data or roles of devices are visible/advertised directly to the Internet (e.g. a web service variants mounted on devices that are identified by URL). Another extreme variant of the latter case is the RFID-tag where the tag is effectively confirming its “IP” presence by reactive uploading of data that explains it as an attachment. There are numerous questions: reachability of devices’ data and roles, manner of participation in the IP protocols (as active IP hosts, via gateways or passive IP-tagged components), extent of IP stack implementations in devices, IP routing [14], web service data flow characteristics (e.g. web feeds), application and web level protocols (e.g. HTTP, then, Constrained Application Protocol (CoAP) by IETF’s Constrained RESTful Environments (CORE) working group [7]…), geographical/location relevance of IP(v6) addresses etc. B. Some Targeted Research Challenges We organise the research challenges in conformance with our practical ambition and scope but attempt to approach it from a generic, wider and collaborative context: 1) Programmability: the concept stands for all active reprogramming of device software by remote interventions of the system or by autonomous reaction of devices. Overthe-Air (OTA) programming is already applied for remote programing of (sensor) devices and ought to embrace the awareness of many functional components in IoT networks. Progression and potentials of programmable IoTs are already assumed in novel FI visions, e.g. Tactile Internet [22]. Research can further reveal the multidisciplinary optimisations, hardware requirements and performance trade-offs of the software alteration procedures. 2) Orchestration: this generic term stands for control and management aspects and is based on the extent of programmability. Interventions in ranges of functional aspects of systems would be of paramount importance for achieving its integration. Concepts of Software Defined Networking (SDN) [12] could provide an abstraction for the tools needed, i.e. brake-up of the functional/plane separations in systems. We distinguish between the main functional aspects involving orchestrations: • Operational parameters: these include data transmission periods, data content, energy-related parameters, wireless transmissions, etc. All operational parameters should be subject to coordinated adjustments. • Infrastructure flexibility: concepts such as “virtualisation” applied in standard networks would apply to IoT, e.g. sensor/actuator microcontrollers or entire
clusters can be opened to changeable purposes, applications and users. • Expedited Transport and Networking: In an integrated system, data flows would be controlled by both PHY/MAC and TCP/IP layers solutions. Available PHY/MAC solutions such as IEEE 802.15.4 [4],[8] would achieve greater integration if operational features could be further controlled (e.g. sleep time, addressing, routing entries, controllers/distributions…) or simplified in each device by relying on dedicated control. At the IP layer, control would expedite adaptations needed in IP for IoT in terms of: formats (e.g. 6LoWPAN [14]), routing (IETF’s “Routing over power and Lossy (ROLL) networks” working group), content-awareness, stack layouts…With TCP, research can tackle the shortcomings of TCP mechanisms in sensor networks due to TCP’s fixednetwork based procedures for retransmission, confirmation, etc. Solutions to TCP shortcomings include intelligent caching [20] or using pseudo-connectionless applications delivery in IoT network segments via CoAP [7]. • Optimising deployment: this issue is related to the operational parameters but observes broader sets that specify physical properties of wireless mediums. There are many mathematical algorithms that optimise planned deployment of devices positioning subject to numerous constrains and objectives [15]. Recent progress in the PHY layer areas, such as modulation schemes, interference management, cooperative relaying are areas that could contribute to the precisions of optimisations. 3) Data processing: relevant techniques usually depend on the extent and diversity of data collections. Equally, many categories of data processing would fit as compliments to other challenges. Here we point out that as the system expands, in terms of volume of data and diversity of sources and applications, data processing becomes more applicable. Data in an integrated system undergoes various stages of interpretations, hence, data mining has already received significant attention in IoT applications [16]. These problems also contribute to the emerging question of Big Data, but include many specific requirements: data collection, distributed and centralised processing (e.g. at intermediate points such as gateways, cloud…), real-time constrained [19], representations (e.g. semantics/ontol-ogies, data graphs [20]…). Solutions can offer deductions such as: visualization of networks, operational anomalies, malfunction detections, faults, traffic estimates… Some applicable techniques include: compressive sensing, dictionary learning, fuzzy logic and machine learning [17],[18]. Finally, we add the vast area of security issues under the data processing challenge for integrity protection via cryptology and detection of malicious attacks. 4) Coherency of the technical solutions and application requirements: Impact of solutions is often subjective to the view of users and commercial success of applications. Considering needs of users (e.g. in agriculture plantations) is a tuning process for many technicalities and research. IV. CONCLUSION Global push for realisation of the IoT concepts has provided a fresh perspective on how FI needs to expand from the current form. It has also opened an integration
window for numerous WSNs that have been deployed in the recent decade. Combinations of different devices, communication standards, applications, connectivity options etc., combined with the purpose-driven deployment of networks using sensors or actuators, pose a complex integration task both globally and in scoped environments. This paper offers a contribution in strategically identifying the development areas and research topics that have been organised behind a practical goal of a regional network of various applications of WSNs and IoT. REFERENCES [1] [2] [3]
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