Wireless Sensor Networks: Applications and Forms

Wireless espial element Ne dickensrks Applications and Forms1 Wireless demodulator NetworkIn this chapter, tuner sensing element earnings (WSN) principles atomic return 18 being shortly introduced and discussed. In order to summation the level of understanding for analyzing Wireless Sensor Network (WSN) corpses it is useful to subscribe to the technology behind them the technologies which atomic number 18 presented in this section.Wireless Sensor Networks (WSNs) ar distributed and indep closing curtainent sensors that atomic number 18 connected and worked together to measure quantities much(prenominal) as temperature, humidity, pressure, noise levels or vibrations 5. WSNs batch measure vehicular movement (velocity, location, etc.) and monitor lizard conditions much(prenominal) as lightning condition, soil makeup and motion 5. Nowadays, WSNs be employ in m some(prenominal) common lotions much(prenominal) as fomite applications. more than or less of vehicl e applications are vehicle tracking and encounterion, tire pressure monitoring, vehicle speed detection, vehicle direction indicator, commerce comprise, reversing aid sensors etc. such(prenominal) applications bed be divided in major categories such as safety, earnest, environment and logistics.To implement WSN in an application and have an efficient form, premier we carry to consider about WSN technology, compvirtuosonts and parley net regional anatomy and conversations protocols. Therefore, first, in this chapter, canonic information about WSN comp angiotensin-converting enzyments, the communion gismos and lick unit of WSN will be described. Then, the chapter will be fol let looseed by a description of the WSN topologies and protocols emphasizing on employ WSN technology with ZigBee Protocol.1.1 Wireless Sensor Network componentTo come done comprehensive view of WSN computer ironware, understanding of WSN components structure is necessitated. Wireless se nsors are littler microcontrollers equipped with receiving set communication gubbins and an energy supplier. The architecture of WSNs is illust driftd in human body 31 .As Figure 31 shows the components of WSNs are sensing unit, motioning unit, author supplier and communication device. The sensing unit consists of sensors and Analog to Digital Converters (ADCs). ADCs are trustworthy for congregation the signals and converting them into digital signals info and transpose them through wholly(prenominal) another(prenominal) using net income analysis situs to the processor unit. In the sensing unit, separately sensor is called an end node and varies in size and cost. The mission of these multifunction sensor nodes are to sense, process information and collaborate with other nodes 8. Wireless sensor profits can be positioned in two courses, either using a compound technique with the large sensors far from the bearing or using some(prenominal) sensors with an en gineered design on position and topology 5. In addition, each node provided with a wireless communication transceiver as a communication component.In the process unit, the controller and small memory storage are accountable for managing the collaboration inwardly the sensors to achieve the assigning task. In addition, the communication device with a transceiver makes the entanglement connection. Above all, the essential component of WSN is the king unit, which supports the power for all units 5.One of the unique feature of speechs of sensor engagements is that they are equipped with an on-board processor. This rollick enables them to locally process some simple computations and broadcast only demand processed selective information 5. Network communication is really complicated and unavoidably years of speculate 8, but to be able to implement WSN, we get hold of to know some basic primary concepts of communication technology such as network topologies, network protocol an d their samples and specifications.1.2 confabulation technologyTo get through technical aspects of WSN, network topology and network protocol studying is needed. This study will help to provide information about reli qualification, validness, bail and perceptual constancy and of WSNs parcel aspect to answer the research questions RQ. 1 ,RQ. 2 and RQ. 3 .1.2.1 Topologies in WSN CommunicationIn network communication, the big issue is how selective information transfers through nodes and nodes interconnect with each other. Several basic network topologies whitethorn be utilize for transmitting to and receiving from a node. The compact for Telecommunications Industry Solutions (ATIS) the ensamples organisation of telecommunication industry explained the network topology as The strong-arm, real, logical or virtual arrangement of the nods/elements of a network 9. The topology shows the diameter and the number of nodes between some(prenominal)(prenominal) two nodes. Moreover how a data process and the data routing complexities are relied on the chosen topology. Consequently, some characteristics of a sensor networks such as latency, robustness and capacity are shiftd by their topology 10.Figure 32 is a graphical mapping of networks topology which shows the think of one or more nodes and explains the corporeal topology of the network. disrespect having the same topology, two networks can differ in transmission place be power of their physical interaction, signal types and distance between nodes 9. board 31 describes the different types of network topology.Table 31 Topology TYPES 9.Since displace topology is a main topic in the thesis, it is studied more in-depth in this section1.2.1.1 Mesh Wireless NetworkWireless take topology network is a term used when all wireless nodes are connected to each other within an ad-hoc multi-hob and go topology. In this network, all pair of nodes is able to communicate between each other within more than one pathway. In this network each node is used as a router to forward packets to the neighbor nodes which they have affaired to. That convey all nodes communicate directly or through other central nodes without any manual configuration. Therefore, this network likewise called a self-configuration and self-organized network 11 12.As described in Table 31, there are two types of mesh topology Partially connected and Fully connected (See Figure 33). In a amply connected topology each node has the ability to communicate with all other nodes in the network and creates an interconnection links. By increasing the number of nodes in a mesh network, the number of links increases as well. On the other hand, in a partially connected topology, instead of direct interconnection between nodes, each node has two or more links to others to provide interchange routing and traffic balancing. Due to more links and indirect connections between nodes, traffic can flow through one or more router nodes to the polish 7 and create more reliable interconnections between nodes.Moreover, in partial network, the nodes are connected to either the node with higher(prenominal) rate of data consummation or the nearest neighbor node while in fully connected network all nodes have a direct links with each other. This multiple link path conducts a reliable communication. Therefore, whenever a connection fails or a node breaks down, the packages can automatically change their path by burst forthing from a disconnected node. This is often called the self-healing of the network. This way that the networks connection stability and dependableness are not essentially modify by node failures 11.Due to the characteristics of wireless sensor network mesh, this network is self-configuring and self-organizing network in which each end-node is too used as a router (dual role- data originator /data router) to forward the signal packages all the way back of the main gateway.Therefore, due to the cha racteristics of mesh networks, this network is becoming one of the most implemented networks which able to have the flexible architecture for the network, tardily self-configuration and robust teddy margin connectivity 11 12. Additionally, the self-configuring characteristic of mesh WSN, bring the ability for the network to connect or disconnect nodes from the network. This brings the ability to grow/ reducing the network by adding/removing nodes of a system.Mesh WSN has reliable self-healing and robust erroneousness tolerance. This means if a node fails or breaks down the signal packages jump from the disconnected node and automatically conducts a new path through the nearest node. However, the new path jaws re-routing and re-organizing to the network 5, which consumes too much power from the system. Therefore, having a power-aware protocol and algorithm is necessary for mesh network. ZigBee protocol is one of the protocols which provides this ability for WSN.1.2.2 Protocols in WSN CommunicationWSN systems include variety of protocols for communication. Protocols need to broadcast in different architectural levels. One of these architectural standard is OSI (Open dust interconnection) framework. In this session a brief introduction of each protocol and OSI are delineated.Figure 34 shows the graphic overview of all wireless network technologies. This figure illustrated IEEE PAN/LAN/MAN technologies and clearly shows how these standards and protocols can be used in different conditions. For instance, 3G protocol is used to secrecy a long range of audio information in a wide area network (WAN) while for the same information in a short range and personal area network (PAN), Bluetooth is better.The standard conceptual rules set for data pay offation, data communication and error detection across two ends in telecommunication, are called communication protocols. These abstract rules represent in different bottoms of communication. There are different pr otocol tons introducing different architectures for these seams such as AppleTalk, Distributed Systems Architecture (DSA), Internet protocol cortege (TCP/IP) and Open Systems Interconnect (ISO/OSI). Figure 35 (a) illustrates the different horizontal surfaces of an OSI put and their functionalities. The OSI sit down has s nonetheless layers and each layer provides aids for the upper layer and requests services from the lower layer. Figure 35 (b) shows the typical communication protocols layers. Each of these layers has to deal with different issues regarding the communication procedure.As the typical protocol stack model shows in Figure 35 the communication protocols should implement all layers from bottom to top. In addition, a deliver the goodsment protocol necessarily to be applied in each layer to manage power aptitude, robust connectivity and connection dependableness (see Figure 35 b). Below, rules and functionality for each layer are described* physiological layer is responsible for signal processing and physical interface connectivity between a device and physical medium and used bit stream in its data unit. It acted as communication channel for sensing and actuation in cost- impressive and reliable manner. Some examples of this layer are IEEE 802.11b/g Wi-Fi, IEEE 802.15.1 Bluetooth, IEEE 802.15.4 ZigBee, etc. 7* selective information link layer provides functionality toward channel sharing, Medium Access Control (mackintosh-Layer), quantify (e.g. data time arrival), local link and capacity. It is responsible for detecting and correcting the data errors in physical layer and control the locality data comparison. It follows the protocols such as point-to-point protocol (PPP) and IEEE 802 Local Link Control (LLC). 7* Network layer is responsible for network routing functionality, network security, energy and power efficiency and dependability of the communication. It includes the network topology management and manages the information and detects errors in data transfer from router to router. A number of protocols is actors line in this layer such as Internet protocol (IP), Threshold Sensitive Energy Efficient Sensor Network Protocol and etc. 7.* Transport layer provides end-to-end shipping (distributing and gathering) of data between end users. It includes storage and responds for caching and autocratic the data to heal them back to the initial message that has been sent. Best-known protocols for this layer are contagion Control Protocol (TCP) and User Datagram Protocol (UDP) 7.* velocity layers The Upper Layers are responsible for application processing, external query processing and etc. Upper layers include presentation layer session layer and application layer 7.The summary of these standards and protocols are shown in Figure 36Among all the standard and protocols, IEEE PAN/LAN/MAN technologies are the ones applied in the majority of commercialWSNs to support physical layer and link-data layer signal transmi ssion. As SOHRABY and ZNATI (2007) mentioned, the most common best-known protocols are (1) the IEEE 802.15.1 (also known as Bluetooth) (2) the IEEE 802.11a/b/g/n series of wireless LANs (3) the IEEE 802.15.4 (ZigBee) (4) the MAN-scope IEEE 802.16 (also known as WiMax) and (5) radio- oftenness realization (RFID) tagging 7. Each of these protocols has their own benefits and constraints. The comparisons between IEEE technologies are mentioned in Table 32. As Table 32 shows the IEEE 802.15.4 standard provides data rate of 20 to 250 kbps and operates in the 2.4-GHz ISM band. This standard covers signals in range of 10 m and requires the lowest power among other IEEE class. While IEEE 802.11a/b/g/n transmits the data in the rate of 54 Mbps ideal for wireless internet connections and operates in the 2.4-GHz ISM (Industrial, Scientific and Medical) radio band as well as the 5-GHz ISM / 5-GHz U-NII (Unlicensed National Information Infrastructure) radio band. However, it requires much higher power consumption than IEEE 802.15 7.Recently, researchers put much effort to amaze a cost-effective standards-based wireless networking solution that supports low-to medium data rates, has low power consumption, and guarantees security and dependableness 7. ZigBee Alliance is an association of companies which aims to provide such a standard for WSN consumers. Their mission is to have a simple, reliable, low-cost, low-power and standards-based wireless platform1.2.2.1 ZigBee standardThe ZigBee standard builds on IEEE 802.15.4 and is suitable for remote monitoring and controlling applications. Although it has lower-data-rates than the other standards, its reliability, security, long life battery with less complexity instrument make it ideal for building automation in industrial network applications. The architecture of the ZigBee stack is established on the Open System Interconnection (OSI) model. The IEEE 802.15.4 defines the physical layer (PHY) and medium access control (MAC) sub-layer and In addition, ZigBee Alliance defines other functionalities for upper layers 7. Figure 37 is a graphic overview of ZigBee protocol stack and shows the responsibility areas of IEEE 802.15.4, ZigBee Alliance platform and users applications 7. This picture also shows the basic functionality of each layer.The data transmission service is provided by PHY layer and the protocol in this layer enables the connection between data units and the physical radio channel. ZigBee provides deuce-ace different frequency band options for PHY layer. First, the transmission data-rate of 250kbps in 16 channels at 2.45GHz (Global) frequency. Second, with 40Kbps in 10 channels at 915MHz (Americas). And the last one, with 20kbps in 1 channel at 868MHz (Europe). The higher data-rate causes a higher order in modulation design and the lower frequency cause a larger cover area and better sensitivity. Depending on the power output, the transmission distance rate can change from 1 to 100 meters. (F or more detail information see Table 71 in Appendix A)ZigBee WSN has the ability to have static or dynamic network/component with either star or mesh topology and it has terce types of nodes a ZigBee Coordinator (ZC), ZigBee Routers (ZR), and ZigBee End-Devices (ZED).In order to have a communication protocol and physical connection twain PHY layer and MAC sub-layers of the architecture should be defined upon agreement between server and clients. These layers require manual administrative procedures setting for server/client gateway.The next three levels namely the network layer, security protocol and transport layer are defined by ZigBee alliance platform automatically. The last layer, application layer, has to interact with the user-interface and other applications it ought to be programmed with high-level language so that integration with any existing devices applications becomes more conveniently practical.The ZigBee stack in gateway is responsible for all the network functiona lity such as network process management, trademark of the joined nodes, binding nodes and routing the messages throughout the network. ZigBee stack as a standard protocol, has clusters and libraries for improving the implementation process, therefore, using ZigBee compare to other protocols makes the system (including both hardware and software) development process much faster and easier. On the other hand, such standardisation provides easiness of adopt with third party sensors irrespective of manufacturer, which might be attached to the network later.2 Software AspectsTo address the research question regarding the reliability, robustness, and security of any WSN application, it is essential to investigate the software architecture of that network. For convenience in description of the architecture of a WSN application, it is divided into three segments Physical devices (such as lamps, sensors, nodes), Communication Protocol (terminals and servers, bridge, switch, network topology and standard) and Carried Information (application, functions, etc.).Any attempts to retain a precise design on software architecture for each part will cause an effective data transmission, which ensures reliability and security of the system 7. hence achieving any desired data transmission precision level in a WSN, network management (NM) techniques are applicable. Such techniques assist in network locating monitoring, reliability and security amendment, and cooperation supervision between components 7. NM techniques could also detect and resolve network faults in addition to restoring the system respectively 7.In practice, designing WSN application necessitates tailoring NM techniques for each architectural segment. motley NM techniques regarding each segment are summarized as follows 7 12 5a) Physical architectureSensing and processing management, operation and administration, fault tolerance, maintenance, energy efficiency management, configuration management, performance m anagement, security management, network element management.b) Communication architectureNetwork management, networking protocols, network topology, function management, monitoring functions, fault management, performance management, security management, service management and communication, maintenance management, network configuration and organization, network behavior, data delivery model, sensor mobility, naming and localization, sensing insurance coverage area, communication coverage area energy efficiency managementc) Information architecture real-time information management, mapping management, service management, analyze information, control application, business application management report management, direct and receiving commands or response, naming, localization, maintenance, fault tolerance said(prenominal) NM techniques enhance quality of the system. According to ISO 9126-1 software quality model Table 41 13 14 15, the quality characteristics of a system could be div ided into six fundamental kosherties functionality, reliability, usability, efficiency, maintainability, and portability. According to the same documentation, these characteristics are broken to sub-characteristics such as suitability, security, maturity, fault tolerance, adaptability, analyzability, stability, testability and so on 13. However, snap on all subcategories collectively exceeds the time horizon of this research, from this stance three dimensions namely reliability, robustness and security are brought into attention.This section will be divided to two subsections describing the architecture issues and NM techniques for (1) Reliability and Robustness, (2) Security, of WSN and other characteristics is relegated to futurity studies.2.1 Reliability and RobustnessIn WSNs context, the probability that a network functions right on and aggregates trustworthy data without any interruption continuously, is usually referred to as reliability characteristic of the network 23 20 . According to ISO 9126-1 software quality documentation, reliability characteristic shows the capability of a network to maintain or re-built (re-start) the service in certain period of time 13. So, it is important that during long sensing, the network has to service up continuously. Reliable service of a network includes precise and proper sensing, delivering and sending acceptable data to the base station. In other quarrel as Taherkordi et al. (2006) put The less loss of interested data, leads us to higher reliability of a system. Systematic approach perceives reliability as probability of data delivery to the base station rather than point-to-point reliability 16.Robustness defined by Sohraby et al. (2007) as a combination of reliability, availability, and dependability requirements, reflects the degree of the protocol insensitivity to errors and misinformation. Achieving system robustness in WSN, necessitates system capability to detect, tolerate and confine errors as well as reconfigure and restart the network respectively 7. According to the given definition by Sohraby et al. (2007), it is comprehendible that reliability and robustness share commonalities with each other this is the main logical behind discussing these two attributes together in this section 7.Considering the nature of communication in WSN, a network is unpredictable and prostrate to fail caused by any physical damages in hardware devices, energy depletion, communication link error, information collapses in packages and etc. 17 16. Therefore, one of the critical issues in design phase of WSN is applying fault tolerance techniques to optimize the network so that reliability and robustness attained 17. These techniques enable the network to withstand and ascertain any upcoming failure and restart operation 13.Liu et al. (2009) categorized fault tolerance techniques into node arrangement, topology control, target and event detection, data gathering and aggregation, and sensor surveil lance. Reminding from the beginning of this chapter architecture design divided into three segments. Table 42 depicted a summary of the plausible related faults and their solutions in each segment. In the following, each aforementioned fault tolerance techniques are being discussed in each design segment.Table 42 The most probable fault and their fault tolerance solutions in WSN 17 7 182.1.1 Reliability and Robustness of Physical Architecture happy chance any physical interruption in sensor surveillance Solution thickener placement management and signal-effect managementFirst item that should be considered in designing physical components architecture for reliability and Robustness is physical placement and signal-effect management. As it is mentioned in section 3, although the mesh network communication is self-organize topology and does not need any manual configuration to bind the network for mobile sensors, the physical architecture and the location schema of the hardware comp onents, sensors and gateways need to be designed carefully 7.As a characteristic of mesh WSN, the sensors in network are free of any installation restrictions, even though, the placement should be far from any physical destruction or hostile locations. Inappropriate physical placement of sensor transmitters and gateway advance can cause noise or significant lost in signals 7. In addition, the signal coverage is decayed by surrounding objects and materials such as metal wall and the like. (E.g. exterior wooden, concrete, brick or gypsum frame, block or wall). Especially in the case of vehicles, the main body can impose such problem and henceforth installation of the sensors in this manner would be delicate.Moreover, the signal oscillates might be faded and affected during the transmission, due to sundry(a) physical phenomena such as reflection, diffraction or scattering 7. These effects would cause significant interruption in sensor surveillance. Therefore, it is important to mana ge these signal-effects in early stage of WSN physical architecture design.Reflection occurs when electromagnetic flutter of signals is duplicated due to impinge of the wave on large object or surface such as walls, buildings and the Earth 7. Therefore, all the reflection of the walls and also the Earth should be acknowledged in physical architecture design.Diffraction refers to any defection and obstruction in waves caused by irregular sharp edges during the data transmission between the transmitter and receiver 7. In this case, designers have to be prudent in sensors placements in the proximity of sharp edges and corner angels. spread refers to any deviation from straight line. Environmental obstacles in the propagation path affect passing waves from their original structure. Even small irregular object such as street signs, and lampposts might encounter and scatter the wave. Hence WSN should be design to face with any irregular scattering during the wave transmission. Above all, the mobility of sensors and surrounding objects might fade the signals and add noises that should be considered in architecture design 7.These issues are the basic physical factors, which cause major fault in data aggregation of WSN and cut down reliability and robustness. These destructive signals need to be subtracted from the received signal paths 7 before sending the data to gateway. Therefore, reflection, diffraction and scattering should be considered not only by designers in the physical components placements, but also by programmers in network development. Fault Sensors failure Solution Hardware replacementThe next issue that need to be considered in designing the physical architecture of a WSN is hardware failure. Sensors energy suppliers or any damages to the sensors and/or their transmitters are the sources of hardware failure. Regardless of source of failure, the WSN must be capable of functioning as well as replacing and switching sensors when necessary. Additionally, any changes in the physical components, on one hand, needs an explicit and well-defied consideration on security issue to prevent any potential threats, and on the other hand, needs an adaptable and configurable communication connection network 18.2.1.2 Reliability and Robustness of Communication Architecture Fault communication link errors SolutionTopology control and event detection , Replicated services in communication model,Communication link error is an important concern in dealing with reliability and robustness of a network in communication architecture. The sensors in WSN are prone to fail and make link errors in point-to-point reliability of communication protocol. Therefore, it is the network topology responsibility to detect the errors and guarantee the overall reliability of the syste