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The IoT hardware require operating systems and communication protocols to interact with user and other devices. There are components that facilitate communication and exchange of information between devices. In IoT architectures, integration layers play an important role in combining and integrating information acquired from thousands of devices and presenting this information to users. In this section we review general software structure inside of an IoT system. In design of an IoT software platform, scalability, the extensibility and interoperability between heterogeneous devices and their business models should be considered. In addition, IoT enabling technologies (hardware) may move geographically hence need to communicate with others in a real-time mode. This kind of operation necessitates decentralized and event-driven software architecture. Service-oriented-architecture (SoA) ensures the scalability and interoperability of heterogeneous technologies in one platform. In a generic SoA four layers are defined:
In a SoA for an IoT middleware, the software between objects (things which are equipped with sensors) and applications should provide object abstraction, service managements and service composition through a secure network.
Each IoT software main task is device identification in network. For object identification, different addressing methods are used based on internet protocols (IPs) such as IPv4, IPv6, and 6LoWPAN. For the identification it should be notified that object’s identification and address are different. While an object can be identified locally, for example inside a 6LoWPAN network, the object within the global network uses public IPs as the address. Identification methods aim to make a clear identity for any object inside the network. Communication link technologies should provide the infrastructure for the connection of smart devices (sensor nodes). The IoT sensor nodes should work normally under severe designs specifications including low-power consumption, and operation in noisy environment. Currently, there are different communication protocols which can be used for IoT applications:
The IEEE 802.11 technology is designed to implement single‐hop ad hoc networks with extreme simplicity.
The Wi‐Fi stations must be within the same transmission radius (about 100‐200 meters) to be able to communicate. When the distance between a device and the router increases, the Wi‐Fi range limitation can be overcome by implementing multi‐hop ad hoc networking with the addition of routing mechanisms at stations.
Ultra‐Wideband (UWB) is a radio technology used in wireless networking, developed to achieve high bandwidth connections with low power utilization.
Ultra‐wideband technology differs substantially from other technologies (e.g. Bluetooth and 802.11a/b/g): it is based on short pulses using an extremely wide band of RF spectrum, on the order of several GHz, with low duty cycle and power spectral density with the main advantage of being able to transmit more data in a given period of time.
The goal of Bluetooth technology is a short‐range communication system to replace the cables in WPANs to enable users to connect, in a rapid or automatic way, a wide range of personal electronic devices (e.g. smartphones, speakers, GPS receivers, bar code scanners).
The initial idea, coming from an Ericsson project in 1994, was to replace wires. The project evolved and generated the Bluetooth Special Interest Group (SIG) and it was standardized by the IEEE as Wireless Personal Area Network (WPAN) specification IEEE 802.15.
Communication network protocols are structured as a stack of layers. Each layer provides the directly upper and lower layers with services according to well defined interfaces. The layered model of network architecture protocols has many advantages, in particular the independence of one layer from the others, a greater flexibility and compatibility between devices, systems and networks.
ZigBee is a specification for a suite of high level communication protocols; in fact ZigBee defines only the networking, application and security layers. As shown in Figure 11, the two lowest layers NWK and PHY, are defined by IEEE 802.15.4 standard. ZigBee adopts IEEE 802.15.4 physical and medium layers as part of itself.
As IEEE 802.15.4 is a standalone protocol suite, it is possible to develop a wireless network completely different from ZigBee.
WirelessHART is a wireless sensor networking technology designed to add wireless communication to the existing HART devices (Highway Addressable Remote Transducer), based on a specialized standard mostly used in factory and process control.
The WirelessHART protocol is capable of providing a wireless mesh topology where each device in the network can act as a router to forward messages from other nodes; this solution leads to an increased reliability of the wireless transmissions, thanks to the redundant communication routes and, at the same time, extends the range of the network without the need of additional infrastructure.
6LoWPAN is an acronym for IPv6 over Low power Wireless Personal Area Networks; it is an open standard developed by the Internet Engineering Task Force (IETF). The 6LoWPAN protocol is raising considerable interest, particularly in relation with smart energy and smart grid applications, as it enables all the capabilities of IPv6 (Internet Protocol version 6) to individual sensor nodes. Internet Protocols (IP) addresses are required to be global and unique for each node of the network; with the advent of IPv6 increasing the availability of IP addresses networking appliances and assets are expected to outnumber the conventional computer hosts.
RuBee is an emerging IEEE 1902.1 based standard that should overcome the limitations of the actual RFID technology and provide additional features such as an increased read range, compared to passive RFID tags, simple set up and low cost.
The main difference between RuBee and ZigBee or Bluetooth is that RuBee works using magnetic field, whereas the others work with the electric field. This is a very important characteristic because it provides RuBee networks with the ability to work in harsh environment such as near steal or water and around corners, where other technologies are not applicable.