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Internet of Things in Industries: A Survey.pdf

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    The Internet of Things: A survey
    Introduction
    One paradigm, many visions
    Enabling technologies
    Identification, sensing and communication technologies
    Middleware
    Applications
    Service composition
    Service management
    Object abstraction
    Trust, privacy and security management
    Applications
    Transportation and logistics domain
    Logistics
    Assisted driving
    Mobile ticketing
    Monitoring environmental parameters
    Augmented maps
    Healthcare domain
    Tracking
    Identification and authentication
    Data collection
    Sensing
    Smart environments domain
    Comfortable homes and offices
    Industrial plants
    Smart museum and gym
    Personal and social domain
    Social networking
    Historical queries
    Losses
    Thefts
    Futuristic applications domain
    Robot taxi
    City information model
    Enhanced game room
    Open issues
    Standardization activity
    Addressing and networking issues
    Security and privacy
    Security
    Privacy
    Conclusions
    References
    Computer Networks 54 (2010) 2787–2805 Contents lists available at ScienceDirect Computer Networks j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c o m n e t The Internet of Things: A survey Luigi Atzori a, Antonio Iera b, Giacomo Morabito c,* a DIEE, University of Cagliari, Italy b University ‘‘Mediterranea” of Reggio Calabria, Italy c University of Catania, Italy a r t i c l e i n f o a b s t r a c t Article history: Received 10 December 2009 Received in revised form 27 April 2010 Accepted 14 May 2010 Available online 1 June 2010 Responsible Editor: E. Ekici Keywords: Internet of Things Pervasive computing RFID systems 1. Introduction This paper addresses the Internet of Things. Main enabling factor of this promising para- digm is the integration of several technologies and communications solutions. Identifica- tion and tracking technologies, wired and wireless sensor and actuator networks, enhanced communication protocols (shared with the Next Generation Internet), and dis- tributed intelligence for smart objects are just the most relevant. As one can easily imagine, any serious contribution to the advance of the Internet of Things must necessarily be the result of synergetic activities conducted in different fields of knowledge, such as telecom- munications, informatics, electronics and social science. In such a complex scenario, this survey is directed to those who want to approach this complex discipline and contribute to its development. Different visions of this Internet of Things paradigm are reported and enabling technologies reviewed. What emerges is that still major issues shall be faced by the research community. The most relevant among them are addressed in details. Ó 2010 Elsevier B.V. All rights reserved. The Internet of Things (IoT) is a novel paradigm that is rapidly gaining ground in the scenario of modern wireless telecommunications. The basic idea of this concept is the pervasive presence around us of a variety of things or objects – such as Radio-Frequency IDentification (RFID) tags, sensors, actuators, mobile phones, etc. – which, through unique addressing schemes, are able to interact with each other and cooperate with their neighbors to reach common goals [1]. Unquestionably, the main strength of the IoT idea is the high impact it will have on several aspects of everyday-life and behavior of potential users. From the point of view of a private user, the most obvious effects of the IoT introduc- tion will be visible in both working and domestic fields. In this context, domotics, assisted living, e-health, en- hanced learning are only a few examples of possible appli- * Corresponding author. Tel.: +39 095 7382355; fax: +39 095 7382397. E-mail addresses: l.atzori@diee.unica.it (L. Atzori), antonio.iera@unirc. it (A. Iera), giacomo.morabito@diit.unict.it (G. Morabito). 1389-1286/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.comnet.2010.05.010 cation scenarios in which the new paradigm will play a leading role in the near future. Similarly, from the perspec- tive of business users, the most apparent consequences will be equally visible in fields such as, automation and industrial manufacturing, logistics, business/process man- agement, intelligent transportation of people and goods. By starting from the considerations above, it should not be surprising that IoT is included by the US National Intel- ligence Council in the list of six ‘‘Disruptive Civil Technol- ogies” with potential impacts on US national power [2]. NIC foresees that ‘‘by 2025 Internet nodes may reside in everyday things – food packages, furniture, paper docu- ments, and more”. It highlights future opportunities that will arise, starting from the idea that ‘‘popular demand combined with technology advances could drive wide- spread diffusion of an Internet of Things (IoT) that could, like the present Internet, contribute invaluably to eco- nomic development”. The possible threats deriving from a widespread adoption of such a technology are also stressed. Indeed, it is emphasized that ‘‘to the extent that everyday objects become information security risks, the IoT could distribute those risks far more widely than the Internet has to date”.
    2788 L. Atzori et al. / Computer Networks 54 (2010) 2787–2805 Actually, many challenging issues still need to be ad- dressed and both technological as well as social knots have to be untied before the IoT idea being widely accepted. Central issues are making a full interoperability of inter- connected devices possible, providing them with an always higher degree of smartness by enabling their adaptation and autonomous behavior, while guaranteeing trust, privacy, and security. Also, the IoT idea poses several new problems concerning the networking aspects. In fact, the things com- posing the IoT will be characterized by low resources in terms of both computation and energy capacity. Accord- ingly, the proposed solutions need to pay special attention to resource efficiency besides the obvious scalability problems. Several industrial, standardization and research bodies are currently involved in the activity of development of solutions to fulfill the highlighted technological require- ments. This survey gives a picture of the current state of the art on the IoT. More specifically, it:  provides the readers with a description of the different visions of the Internet of Things paradigm coming from different scientific communities;  reviews the enabling technologies and illustrates which are the major benefits of spread of this paradigm in everyday-life;  offers an analysis of the major research issues the scien- tific community still has to face. The main objective is to give the reader the opportunity of understanding what has been done (protocols, algorithms, proposed solutions) and what to be addressed, as well as which are the enabling factors of this evolutionary process and what are its weaknesses and risk factors. remains still The remainder of the paper is organized as follows. In Section 2, we introduce and compare the different visions of the IoT paradigm, which are available from the litera- ture. The IoT main enabling technologies are the subject of Section 3, while the description of the principal applica- tions, which in the future will benefit from the full deploy- ment of the IoT idea, are addressed in Section 4. Section 5 gives a glance at the open issues on which research should focus more, by stressing topics such as addressing, net- working, security, privacy, and standardization efforts. Conclusions and future research hints are given in Section 6. 2. One paradigm, many visions Manifold definitions of Internet of Things traceable with- in the research community testify to the strong interest in the IoT issue and to the vivacity of the debates on it. By browsing the literature, an interested reader might experi- ence a real difficulty in understanding what IoT really means, which basic ideas stand behind this concept, and which social, economical and technical implications the full deployment of IoT will have. The reason of today apparent fuzziness around this term is a consequence of the name ‘‘Internet of Things” itself, which syntactically is composed of two terms. The first one pushes towards a network oriented vision of IoT, while the second one moves the focus on generic ‘‘objects” to be integrated into a common framework. Differences, sometimes substantial, in the IoT visions raise from the fact that stakeholders, business alliances, re- search and standardization bodies start approaching the is- sue from either an ‘‘Internet oriented” or a ‘‘Things oriented” perspective, depending on their specific inter- ests, finalities and backgrounds. It shall not be forgotten, anyway, that the words ‘‘Inter- net” and ‘‘Things”, when put together, assume a meaning which introduces a disruptive level of innovation into to- day ICT world. In fact, ‘‘Internet of Things” semantically means ‘‘a world-wide network of interconnected objects uniquely addressable, based on standard communication protocols” [3]. This implies a huge number of (heteroge- neous) objects involved in the process. The object unique addressing and the representation and storing of the exchanged information become the most challenging issues, bringing directly to a third, ‘‘Semantic oriented”, perspective of IoT. In Fig. 1, the main concepts, technologies and standards are highlighted and classified with reference to the IoT vi- sion/s they contribute to characterize best. From such an illustration, it clearly appears that the IoT paradigm shall be the result of the convergence of the three main visions addressed above. The very first definition of IoT derives from a ‘‘Things oriented” perspective; the considered things were very simple items: Radio-Frequency IDentification (RFID) tags. The terms ‘‘Internet of Things” is, in fact, attributed to The Auto-ID Labs [4], a world-wide network of academic research laboratories in the field of networked RFID and emerging sensing technologies. These institutions, since their establishment, have been targeted to architect the IoT, together with EPCglobal [5]. Their focus has primar- ily been on the development of the Electronic Product Code™ (EPC) to support the spread use of RFID in world-wide modern trading networks, and to create the industry-driven global standards for the EPCglobal Network™. These standards are mainly designed to im- prove object visibility (i.e. the traceability of an object and the awareness of its status, current location, etc.). This is undoubtedly a key component of the path to the full deployment of the IoT vision; but it is not the only one. In a broader sense, IoT cannot be just a global EPC sys- tem in which the only objects are RFIDs; they are just a part of the full story! And the same holds for the alterna- tive Unique/Universal/Ubiquitous IDentifier (uID) architec- ture [6], whose main idea is still the development of (middleware based) solutions for a global visibility of ob- jects in an IoT vision. It is the authors’ opinion that, starting from RFID centric solutions may be positive as the main as- pects stressed by RFID technology, namely item traceabil- ity and addressability, shall definitely be addressed also by the IoT. Notwithstanding, alternative, and somehow more complete, IoT visions recognize that the term IoT im- plies a much wider vision than the idea of a mere objects identification.
    L. Atzori et al. / Computer Networks 54 (2010) 2787–2805 2789 RFID UID Spimes Smart Items “Things”- oriented visions NFC Everyday objects Wireless Sensorsand Actuators WISP Connectivity for anything Communicating things IPSO (IP for Smart Objects) Internet 0 Web of Things INTERNET OF THINGS Smart Semantic Middleware Semantic Technologies Reasoning over data Semantic execution environments “Internet”-oriented visions “Semantic”-oriented visions Fig. 1. ‘‘Internet of Things” paradigm as a result of the convergence of different visions. According to the authors of [7], RFID still stands at the forefront of the technologies driving the vision. This a con- sequence of the RFID maturity, low cost, and strong sup- port from the business community. However, they state that a wide portfolio of device, network, and service tech- nologies will eventually build up the IoT. Near Field Com- munications (NFC) and Wireless Sensor and Actuator Networks (WSAN) together with RFID are recognized as ‘‘the atomic components that will link the real world with the digital world”. It is also worth recalling that major pro- jects are being carried out with the aim of developing rel- evant platforms, such as the WISP (Wireless Identification and Sensing Platforms) project. The one in [7] is not the only ‘‘Things oriented” vision clearly speaking of something going beyond RFID. Another one has been proposed by the United Nations, which, dur- ing the 2005 Tunis meeting, predicted the advent of IoT. A UN Report states that a new era of ubiquity is coming where humans may become the minority as generators and receivers of traffic and changes brought about by the Internet will be dwarfed by those prompted by the net- working of everyday objects [8]. Similarly, other relevant institutions have stressed the concept that IoT has primarily to be focused on the ‘‘Things” and that the road to its full deployment has to start from the augmentation in the Things’ intelli- gence. This is why a concept that emerged aside IoT is the spime, defined as an object that can be tracked through space and time throughout its lifetime and that will be sustainable, enhanceable, and uniquely identifi- able [9]. Although quite theoretical, the spime definition finds some real-world implementations in so called Items. These are a sort of sensors not only Smart equipped with usual wireless communication, memory, and elaboration capabilities, but also with new poten- tials. Autonomous context awareness, collaborative communications and elabora- tion are just some required capabilities. and proactive behavior, The definitions above paved the way to the ITU vision of the IoT, according to which: ‘‘from anytime, anyplace con- nectivity for anyone, we will now have connectivity for anything” [10]. A similar vision is available from docu- ments and communications of the European Commission, in which the most recurrent definition of IoT involves ‘‘Things having identities and virtual personalities operat- ing in smart spaces using intelligent interfaces to connect and communicate within social, environmental, and user contexts” [3]. An IoT vision statement, which goes well beyond a mere ‘‘RFID centric” approach, is also proposed by the consor- tium CASAGRAS [11]. Its members focus on ‘‘a world where things can automatically communicate to computers and each other providing services to the benefit of the human kind”. CASAGRAS consortium (i) proposes a vision of IoT as a global infrastructure which connects both virtual and physical generic objects and (ii) highlights the impor- tance of including existing and evolving Internet and net- work developments in this vision. IoT becomes the natural enabling architecture for the deploy- ment of independent federated services and applications, characterized by a high degree of autonomous data cap- ture, and interoperability. In this sense, transfer, network connectivity event This definition plays the role of trait d’union between what we referred to as a ‘‘Things oriented” vision and an ‘‘Internet oriented” vision.
    2790 L. Atzori et al. / Computer Networks 54 (2010) 2787–2805 Within the latter category falls the IoT vision of the IPSO (IP for Smart Objects) Alliance [11], a forum formed in Sep- tember 2008 by 25 founding companies to promote the Internet Protocol as the network technology for connecting Smart Objects around the world. According to the IPSO vi- sion, the IP stack is a light protocol that already connects a huge amount of communicating devices and runs on tiny and battery operated embedded devices. This guarantees that IP has all the qualities to make IoT a reality. By reading IPSO whitepapers, it seems that through a wise IP adapta- tion and by incorporating IEEE 802.15.4 into the IP archi- tecture, the full deployment of the IoT paradigm will be automatically enabled. in the view of 6LoWPAN [12], Internet Ø [13] follows a similar approach of reducing the complexity of the IP stack to achieve a protocol de- signed to route ‘‘IP over anything”. In some forums this is looked at as the wisest way to move from the Internet of Devices to the Internet of Things. According to both the IPSO and Internet Ø approaches, the IoT will be deployed by means of a sort of simplification of the current IP to adapt it to any object and make those objects addressable and reachable from any location. As said before, it is worth noticing that ‘‘Semantic ori- ented” IoT visions are available in the literature [14–17]. The idea behind them is that the number of items involved in the Future Internet is destined to become extremely high. Therefore, issues related to how to represent, store, interconnect, search, and organize information generated by the IoT will become very challenging. In this context, semantic technologies could play a key role. In fact, these can exploit appropriate modeling solutions for things description, reasoning over data generated by IoT, seman- tic execution environments and architectures that accom- modate IoT requirements and scalable storing and communication infrastructure [14]. A further vision correlated with the IoT is the so called ‘‘Web of Things” [18], according to which Web standards are re-used to connect and integrate into the Web every- day-life objects that contain an embedded device or computer. 3. Enabling technologies Actualization of the IoT concept into the real world is possible through the integration of several enabling tech- nologies. In this section we discuss the most relevant ones. Note that it is not our purpose to provide a comprehensive survey of each technology. Our major aim is to provide a picture of the role they will likely play in the IoT. Interested readers will find references to technical publications for each specific technology. 3.1. Identification, sensing and communication technologies ‘‘Anytime, anywhere, anymedia” has been for a long time the vision pushing forward the advances in communi- cation technologies. In this context, wireless technologies have played a key role and today the ratio between radios and humans is nearing the 1 to 1 value [19]. However, the reduction in terms of size, weight, energy consumption, and cost of the radio can take us to a new era where the above ratio increases of orders of magnitude. This will allow us to integrate radios in almost all objects and thus, to add the world ‘‘anything” to the above vision, which leads to the IoT concept. In this context, key components of the IoT will be RFID systems [20], which are composed of one or more reader(s) and several RFID tags. Tags are characterized by a unique identifier and are applied to objects (even persons or ani- mals). Readers trigger the tag transmission by generating an appropriate signal, which represents a query for the possible presence of tags in the surrounding area and for the reception of their IDs. Accordingly, RFID systems can be used to monitor objects in real-time, without the need of being in line-of-sight; this allows for mapping the real world into the virtual world. Therefore, they can be used in an incredibly wide range of application scenarios, span- ning from logistics to e-health and security. From a physical point of view a RFID tag is a small microchip1 attached to an antenna (that is used for both receiving the reader signal and transmitting the tag ID) in a package which usually is similar to an adhesive sticker [21]. Dimensions can be very low: Hitachi has developed a tag with dimensions 0.4 mm  0.4 mm  0.15 mm. Usually, RFID tags are passive, i.e., they do not have on- board power supplies and harvest the energy required for transmitting their ID from the query signal transmitted by a RFID reader in the proximity. In fact, this signal gener- ates a current into the tag antenna by induction and such a current is utilized to supply the microchip which will transmit the tag ID. Usually, the gain (power of the signal received by the reader divided by the power of the signal transmitted by the same reader) characterizing such sys- tems is very low. However, thanks to the highly directive antennas utilized by the readers, tags ID can be correctly received within a radio range that can be as long as a few meters. Transmission may occur in several frequency bands spanning from low frequencies (LF) at 124– 135 kHz up to ultra high frequencies (UHF) at 860– 960 MHz that have the longest range. Nevertheless, there are also RFID tags getting power supply by batteries. In this case we can distinguish semi- passive from active RFID tags. In semi-passive RFIDs batter- ies power the microchip while receiving the signal from the reader (the radio is powered with the energy harvested by the reader signal). Differently, in active RFIDs the bat- tery powers the transmission of the signal as well. Obvi- ously the radio coverage is the highest for active tags even if this is achieved at the expenses of higher produc- tion costs. Sensor networks will also play a crucial role in the IoT. In fact, they can cooperate with RFID systems to better track the status of things, i.e., their location, temperature, movements, etc. As such, they can augment the awareness of a certain environment and, thus, act as a further bridge between physical and digital world. Usage of sensor net- 1 New RFID tags, named chipless tags, are under study which do not use microchips so as to decrease production cost [96].
    L. Atzori et al. / Computer Networks 54 (2010) 2787–2805 2791 works has been proposed in several application scenarios, such as environmental monitoring, e-health, intelligent transportation systems, military, and industrial plant monitoring. Sensor networks consist of a certain number (which can be very high) of sensing nodes communicating in a wire- less multi-hop fashion. Usually nodes report the results of their sensing to a small number (in most cases, only one) of special nodes called sinks. A large scientific litera- ture has been produced on sensor networks in the recent past, addressing several problems at all layers of the proto- col stack [22]. Design objectives of the proposed solutions are energy efficiency (which is the scarcest resource in most of the scenarios involving sensor networks), scalabil- ity (the number of nodes can be very high), reliability (the network may be used to report urgent alarm events), and robustness (sensor nodes are likely to be subject to failures for several reasons). Today, most of commercial wireless sensor network solutions are based on the IEEE 802.15.4 standard, which defines the physical and MAC layers for low-power, low bit rate communications in wireless personal area net- works (WPAN) [23]. IEEE 802.15.4 does not include speci- fications on the higher layers of the protocol stack, which is necessary for the seamless integration of sensor nodes into the Internet. This is a difficult task for several reasons, the most important are given below:  Sensor networks may consist of a very large number of nodes. This would result in obvious problems as today there is a scarce availability of IP addresses.  The largest physical layer packet in IEEE 802.15.4 has 127 bytes; the resulting maximum frame size at the media access control layer is 102 octets, which may fur- ther decrease based on the link layer security algorithm utilized. Such sizes are too small when compared to typical IP packet sizes.  In many scenarios sensor nodes spend a large part of their time in a sleep mode to save energy and cannot communicate during these periods. This is absolutely anomalous for IP networks. Integration of sensing technologies into passive RFID tags would enable a lot of completely new applications into the IoT context, especially into the e-health area [24]. Recently, several solutions have been proposed in this direction. As an example, the WISP project is being carried out at Intel Labs to develop wireless identification and sens- ing platforms (WISP) [25]. WISPs are powered and read by standard RFID readers, harvesting the power from the reader’s querying signal. WISPs have been used to measure quantities in a certain environment, such as light, temper- ature, acceleration, strain, and liquid level. Sensing RFID systems will allow to build RFID sensor networks [26], which consist of small, RFID-based sensing and computing devices, and RFID readers, which are the sinks of the data generated by the sensing RFID tags and provide the power for the network operation. Table 1 compares the characteristics of RFID systems (RFID), wireless sensor networks (WSN), and RFID sensor networks (RSN) [26]. Observe that the major advantages of:  RFID systems are the very small size and the very low cost. Furthermore, their lifetime is not limited by the battery duration;  wireless sensor networks are the high radio coverage and the communication paradigm, which does not require the presence of a reader (communication is peer-to-peer whereas, it is asymmetric for the other types of systems);  RFID sensor network are the possibility of supporting sensing, computing, and communication capabilities in a passive system. 3.2. Middleware The middleware is a software layer or a set of sub-lay- ers interposed between the technological and the applica- tion levels. Its feature of hiding the details of different technologies is fundamental to exempt the programmer from issues that are not directly pertinent to her/his fo- cus, which is the development of the specific application enabled by the IoT infrastructures. The middleware is gaining more and more importance in the last years due to its major role in simplifying the development of new services and the integration of legacy technologies into new ones. This excepts the programmer from the exact knowledge of the variegate set of technologies adopted by the lower layers. As it is happening in other contexts, the middleware architectures proposed in the last years for the IoT often follow the Service Oriented Architecture (SOA) approach. The adoption of the SOA principles allows for decompos- ing complex and monolithic systems into applications consisting of an ecosystem of simpler and well-defined components. The use of common interfaces and standard protocols gives a horizontal view of an enterprise system. Thus, the development of business processes enabled by the SOA is the result of the process of designing work- flows of coordinated services, which eventually are asso- ciated with the interaction among the parts of an enterprise and allows for reducing the time necessary to adapt itself to the changes imposed by the market evolution [27]. A SOA ap- proach also allows for software and hardware reusing, be- facilitates This objects actions. Table 1 Comparison between RFID systems, wireless sensor networks, and RFID sensor networks. Processing Sensing Communication Range (m) Power RFID WSN RSN No Yes Yes No Yes Yes Asymmetric Peer-to-peer Asymmetric 10 100 3 Harvested Battery Harvested Lifetime Indefinite <3 years Indefinite Size Very small Small Small Standard ISO18000 IEEE 802.15.4 None
    2792 L. Atzori et al. / Computer Networks 54 (2010) 2787–2805 cause it does not impose a specific technology for the ser- vice implementation [28]. Advantages of the SOA approach are recognized in most studies on middleware solutions for IoT. While a com- monly accepted layered architecture is missing, the pro- posed solutions face essentially the same problems of abstracting the devices functionalities and communica- tions capabilities, providing a common set of services and an environment for service composition. These common objectives lead to the definition of the middleware sketch shown in Fig. 2. It tries to encompass all the functionalities addressed in past works dealing with IoT middleware is- sues. It is quite similar to the scheme proposed in [29], which addresses the middleware issues with a complete and integrated architectural approach. It relies on the layers explained in Sections 3.2.1–3.2.5. 3.2.1. Applications Applications are on the top of the architecture, export- ing all the system’s functionalities to the final user. Indeed, this layer is not considered to be part of the middleware but exploits all the functionalities of the middleware layer. Through the use of standard web service protocols and ser- vice composition technologies, applications can realize a perfect integration between distributed systems and applications. 3.2.2. Service composition This is a common layer on top of a SOA-based middle- ware architecture. It provides the functionalities for the composition of single services offered by networked ob- jects to build specific applications. On this layer there is no notion of devices and the only visible assets are ser- vices. An important insight into the service landscape is to have a repository of all currently connected service in- stances, which are executed in run-time to build composed services. The logic behind the creation and the manage- ment of complex services, can be expressed in terms of Fig. 2. SOA-based architecture for the IoT middleware. workflows of business processes, using workflow lan- guages. In this context, a frequent choice is to adopt stan- dard languages such as the Business Process Execution Language (BPEL) and Jolie [29,30]. Workflow languages de- fine business processes that interact with external entities through Web Service operations, defined by using the Web Service Definition Language (WSDL) [31]. Workflows can be nested, so it is possible to call a workflow from inside another one. The creation of complex processes can be rep- resented as a sequence of coordinated actions performed by single components. 3.2.3. Service management This layer provides the main functions that are expected to be available for each object and that allow for their man- agement in the IoT scenario. A basic set of services encom- passes: object dynamic discovery, status monitoring, and service configuration. At this layer, some middleware pro- posals include an expanded set of functionalities related to the QoS management and lock management, as well as some semantic functions (e.g., police and context manage- ment) [32]. This layer might enable the remote deploy- ment of new services during run-time, in order to satisfy application needs. A service repository is built at this layer so as to know which is the catalogue of services that are associated to each object in the network. The upper layer can then compose complex services by joining services provided at this layer. 3.2.4. Object abstraction The IoT relies on a vast and heterogeneous set of ob- jects, each one providing specific functions accessible through its own dialect. There is thus the need for an abstraction layer capable of harmonizing the access to the different devices with a common language and proce- dure. Accordingly, unless a device offers discoverable web services on an IP network, there is the need to intro- duce a wrapping layer, consisting of two main sub-layers: the interface and the communication sub-layers. The first one provides a web interface exposing the methods avail- able through a standard web service interface and is responsible for the management of all the incoming/out- coming messaging operations involved in the communica- tion with the external world. The second sub-layer implements the logic behind the web service methods and translates these methods into a set of device-specific commands to communicate with the real-world objects. Some works proposed the embedding of TCP/IP stacks in the devices, such as the TinyTCP, the mIP and the IwIP (see [33] and references herein), which provide a socket like interface for embedded applications. Embedded web servers can then be integrated in the objects, performing the function of this object abstraction layer. However, more often this wrapping function is provided through a proxy, which is then responsible to open a communication socket with the device’s console and send all the com- mands to it by using different communication languages. It is then responsible to make the conversion into a stan- dard web service language and, sometimes, elaborate the request to reduce the complexity of the operations re- quired by the end-device [30].
    L. Atzori et al. / Computer Networks 54 (2010) 2787–2805 2793 3.2.5. Trust, privacy and security management The deployment of automatic communication of objects in our lives represents a danger for our future. Indeed, un- seen by users, embedded RFID tags in our personal devices, clothes, and groceries can unknowingly be triggered to re- ply with their ID and other information. This potentially enables a surveillance mechanism that would pervade large parts of our lives. The middleware must then include functions related to the management of the trust, privacy and security of all the exchanged data. The related func- tions may be either built on one specific layer of the previ- ous ones or (it happens more often) distributed through the entire stack, from the object abstraction to the service composition, in a manner that does not affect system per- formance or introduce excessive overheads. While most of the proposed middleware solutions make use of the SOA approach, some others have followed a dif- ferent way, especially if developed for a specific scenario (target application, specific set of objects or limited geo- graphical scenario). One remarkable project is the Fosstrak one, which is specifically focused on the management of RFID related applications [34]. It is an open source RFID infrastructure that implements the interfaces defined in the EPC Network specifications. It provides the following services related to RFID management: data dissemination, data aggregation, data filtering, writing to a tag, trigger RFID reader from external sensors, fault and configuration management, data interpretation, sharing of RFID triggered business events, lookup and directory service, tag identifier management, and privacy [35]. All these functions are made available to the application layer to ease the deploy- ment of RFID-related services. In [36], the authors present another RFID-related middleware which relies on three functionalities: the tag, the place, and the scenic managers. The first allows the user to associate each tag to an object; the second supports creating and editing location informa- tion associated to RFID antennas; the third one is used to combine the events collected by the antennas and the developed related applications. Another architecture that does not follow the SOA ap- proach is proposed in the e-SENSE project, which focuses on issues related to capturing ambient intelligence through wireless sensor networks. The proposed architecture is di- vided into four logical subsystems, namely the application, management, middleware, and connectivity subsystems. Each subsystem comprises various protocol and control entities, which offer a wide range of services and functions at service access points to other subsystems [37]. This entire stack is implemented in a full function sensor node and in a gateway node; while a reduced-function sensor node has fewer functions. In the e-SENSE vision the middleware subsystem has the only purpose to develop and handle an infrastructure where information sensed by nodes is pro- cessed in a distributed fashion and, if necessary, the result is transmitted to an actuating node and/or to the fixed infra- structure by means of a gateway. The other functions that we have assigned to the middleware shown in Fig. 2 are attributed to other components and layers. The project UbiSec&Sens was also aimed at defining a comprehensive architecture for medium and large scale wireless sensor net- works, with a particular attention to the security issues so as to provide a trusted and secure environment for all applica- tions [38]. The middleware layer in this architecture mostly focuses on: (i) the secure long-term logging of the collected environmental data over time and over some regions (Tiny- PEDS), (ii) functions that provides the nodes in the network with the abstraction of shared memory (TinyDSM), (iii) the implementation of distributed information storage and col- lection (DISC) protocol for wireless sensor networks. 4. Applications Potentialities offered by the IoT make possible the development of a huge number of applications, of which only a very small part is currently available to our society. Many are the domains and the environments in which new applications would likely improve the quality of our lives: at home, while travelling, when sick, at work, when jog- ging and at the gym, just to cite a few. These environments are now equipped with objects with only primitive intelli- gence, most of times without any communication capabil- ities. Giving these objects the possibility to communicate with each other and to elaborate the information perceived from the surroundings imply having different environ- ments where a very wide range of applications can be de- ployed. These can be grouped into the following domains:  Transportation and logistics domain.  Healthcare domain.  Smart environment (home, office, plant) domain.  Personal and social domain. Among the possible applications, we may distinguish between those either directly applicable or closer to our current living habitudes and those futuristic, which we can only fancy of at the moment, since the technologies and/or our societies are not ready for their deployment (see Fig. 3). In the following subsections we provide a review of the short-medium term applications for each of these categories and a range of futuristic applications. 4.1. Transportation and logistics domain Advanced cars, trains, buses as well as bicycles along with roads and/or rails are becoming more instrumented with sensors, actuators, and processing power. Roads themselves and transported goods are also equipped with tags and sensors that send important information to traffic control sites and transportation vehicles to better route the traffic, help in the management of the depots, provide the tourist with appropriate transportation information, and monitor the status of the transported goods. Below, the main applications in the transportation and logistics do- main are described. 4.1.1. Logistics Real-time information processing technology based on RFID and NFC can realize real-time monitoring of almost every link of the supply chain, ranging from commodity de- sign, raw material purchasing, production, transportation,
    2794 L. Atzori et al. / Computer Networks 54 (2010) 2787–2805 Fig. 3. Applications domains and relevant major scenarios. storage, distribution and sale of semi-products and prod- ucts, returns’ processing and after-sales service. It is also possible to obtain products related information, promptly, timely, and accurately so that enterprises or even the whole supply chain can respond to intricate and changeable mar- kets in the shortest time. The application result is that the reaction time of traditional enterprises is 120 days from requirements of customers to the supply of commodity while advanced companies that make use of these technol- ogies (such as Wal-mart and Metro) only needs few days and can basically work with zero safety stock [39,40]. Addi- tionally, real-time access to the ERP program helps the shop assistants to better inform customers about availability of products and give them more product information in gen- eral [41]. 4.1.2. Assisted driving Cars, trains, and buses along with the roads and the rails equipped with sensors, actuators and processing power may provide important information to the driver and/or passengers of a car to allow better navigation and safety. Collision avoidance systems and monitoring of transporta- tion of hazardous materials are two typical example func- tions. Governmental authorities would also benefit from more accurate information about road traffic patterns for planning purposes. Whereas the private transportation traffic could better find the right path with appropriate information about the jam and incidents. Enterprises, such as freight companies, would be able to perform more effec- tive route optimization which allows energy savings. Infor- mation about the movement of the vehicles transporting goods together with information about the type and status of the goods can be integrated to provide important infor- mation about the delivery time, delivery delays, and faults. This information can be also combined with the status of the warehouses in order to automate the refilling of the magazines. 4.1.3. Mobile ticketing Posters or panels providing information (description, costs, schedule) about transportation services can be equipped with an NFC tag, a visual marker, and a numeric identifier. The user can then get information about several categories of options from the web by either hovering his mobile phone over the NFC tag, or pointing the mobile phone to the visual markers. The mobile phone automati- cally gets information from the associated web services (stations, numbers of passengers, costs, available seats and type of services) and allows the user to buy the related tickets [42]. 4.1.4. Monitoring environmental parameters Perishable goods such as fruits, fresh-cut produce, meat, and dairy products are vital parts of our nutrition. From the production to the consumption sites thousands of kilome- ters or even more are covered and during the transporta- tion the conservation status (temperature, humidity, shock) need to be monitored to avoid uncertainty in qual- ity levels for distribution decisions. Pervasive computing and sensor technologies offer great potential for improving the efficiency of the food supply chain [43,44].
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