The Wireless Sensor Devices application

 2.1.     Overview

The following chapter is described by the Wireless Sensor Devices application, challenging, and related work of the research topic in this thesis. Presented here is started with a brief of Wireless Sensor Devices components, Sensor Networks Applications, Issue and Challenges for WSNs that appeared because of the limitations of power. Also, this chapter mentions the Routing Protocols Classification and Sensor Networks Communication Architecture. Finally, Related work done by previous researches to improve the secure routing protocol that we proposed.

2.2.     Wireless Sensor Devices

Making deployment of small, inexpensive and low-power, distributed devices that communicate with wireless and process their data locally, become reality due to the evolution of technology. The sensor nodes have a limitation in processing power. Unlike when sensors coordinated to produce a large number of information, they can measure with considerable details specific physical environment. Therefore, the best described for networks of a sensor are a group of sensor nodes can assortment to carry out a specific activity. The networks of sensors, different from other networks, because it relies on intensive deployment and coordination to perform the tasks. Besides, various sensor nodes in many cases are needed to defeat environmental hurdles such as a line of sight limitation, obstructions, etc. Mostly, the overseen area does not contain an existing infrastructure, either for communication nor energy. It is mandatory for sensors to carry on tiny, limited sources of communicating and power out of the channel of wireless communication [4]. A device called motes, developed by researchers at Berkeley, which ware commercially available to the public with TinyOS [5], the operating system associated with these devices to facilitates usability. Figure 2.1 shows a Berkeley mote device. The reason for ongoing wireless sensor networks revolution is the specifications of the devices such as a simply programmable, totally functional, comparatively inexpensive platform for an experiment, and real deployment.

Figure 2.1. A Berkeley mote (MICAz MPR 2400 series)

In Figure 2.2, there are a number of primary components make up a model wireless sensor network device.

Figure 2.2. Primary components schematic of a wireless sensor network device

2.2.1.      Storage and Memory

Sensors storage in the configuration of read-only in random access memory includes both data memory that is storing processed, raw sensor measurements and other local information. And program memory that stores instructions executed by the processor. The memory and storage quantities on WSN devices board are often restricted mostly by the considerations of economic.

2.2.2.      Sensors

WSN devices may have multiple sensors on board due to many application calls for multi-modal sensing. Dependent on the application, the specific sensors will be used; for instance, WSN may include humidity sensors, light sensors, temperature sensors, or other sensors. 

2.2.3.      Low-power embedded processor

WSN devises computational processing tasks in information that sensed locally also the information interacted by other sensors. There is significantly constrained regarding computational power in embedded processors, because of economic limitation. Due to this constraint of such as processors, typically sensors run operating system for embedded devices like TinyOS which is particularized component-based. However, some nodes may be heterogeneous and include significantly greater power computational. 

2.2.4.      Radio transceiver

The wireless radio in WSN devices includes a short-range and a low-rate also restricted in capability. The cost and immunity to noise in these radios will likely to improve over-time, interference and spectral efficiency. Moreover, radio communication in WSN devices often is restricted operation in power. Therefore, the radio must include effective energy-efficient wake-up and sleep modes.

2.2.5.      Geopositioning system

Geopositioning system used in various WSN applications, the measurements of location stamped is vital for all sensor. To take positioning of the sensor at the deployment stage, the best way is to configure locations. For other field operations in the deployed of a network such as the manner of ad-hoc, obtained information through satellite based on GPS is most easily. Although, also in some of the applications, not all the nodes provided with a capability of GPS, only a little of the nodes. Because of economic and environmental limitations. In this case, the nodes should acquire indirect locations through the algorithms of network localization [6].

2.2.6.      Power source

WSN sensors are battery-powered devices; this gave it flexible deployment. On the other hand, some of the nodes may be wired in some cases, such as some applications that need a continuous power source. In most applications of WSN, the precarious resource of the bottleneck is a finite-energy battery.

2.1.      Sensor Networks Applications

Wireless sensor networks can employ in several approaches like health applications, military applications, environmental monitoring, employment at home, and other prosecutions. The following section will discuss these applications briefly from different domains:

2.3.1.      Military Applications

WSNs are able to perform communications, a difficult portion of military command control, targeting system computing, and surveillance. The military applications lead the ammunition monitoring, equipment’s, monitoring and targeting of friendly and also enemy forces. The sensors can embed in equipment and personnel to can be monitored more closely by their condition. The sensor information's in military devices can be relayed and gathered back to a center of command to certify the perfect course of action. The sensor nodes can track in details movements of enemy troop and vehicle movements in critical areas. Moreover, to send notifications the sensors must be programmed at any time change through a specific region is identified.

2.3.2.      Health Applications

Interfaces can be provided by WSNs in health care applications for the integrated patient observing, human physiological data monitoring, observing the internal and movement procedure of insects, observing patients and doctors and tracking in a hospital. Imaginable that patients' vital signs and location monitoring and tracking by their doctors because of the patients equipped through a sensor of wireless nodes. Patients will be under continual supervision while they move freely. Alert will be raised in an accident situation, such as patient falls and trips, so the sensor sends the patient's location and condition to the hospital workers.

2.3.3.      Environmental Monitoring

Wireless sensor can embed in natural surroundings, to collect data of long term on a previously unattainable resolution and scale turn into possible. These applications can gain localized, complete measurements which are otherwise much problematic to manage. In result, different environmental claims have planned for the networks of the wireless sensor. Few of them consists tracking of animal, detection of forest-fire, habitat monitoring, flood detection, and disaster relief applications.

2.3.4.      Home Applications

Sensor nodes in a smart home can be buried in appliances. These sensor nodes inside the internal types of equipment can link through each other and through the external network with the help of the Internet. The final users can achieve these home appliances locally and remotely more efficiently.

2.3.5.      Other Applications

Some of the WSNs applications are observing the civil structure’s condition. This structure could be roads, buildings, and bridges. Moreover, there are applications for WSN includes inventory management, monitoring quality of product, building virtual keyboards, material fatigue, developing spaces of smart office, environmental control in office buildings, interactive museums, automation and control of factory process, machine diagnosis, transportation, factory instrumentation, robot guidance and control in environments of automatic manufacture, oversight and detecting thefts of car, detection and tracking of vehicles [7][8].

2.2.     Issue and Challenges for WSNs

Wireless sensor network has several challenges, the engineering research going on to address these issues because it not addressed by existing technologies:

2.4.1.      Scalability

In network design of a wireless sensor network, the scalability is an essential criterion because nodes number can be various volume orders higher than in a network of ad hoc.

2.4.2.      Extended lifetime

Wireless Sensor Network nodes will mostly be roughly energy reserved because of the batteries limitations. Due to replacing and monitoring of cells for large networks is difficult, much longer lifetimes batteries are desirable. Moreover, in many WSN applications, it is compulsory to offer guarantees that an unattended wireless sensors system can stay active without any alternatives for many years. For this reason, the primary goal of WSN protocols designs must be energy efficiency.

2.4.3.      Frequent topology changes

Topology in sensor networks is always changing, because of different reasons, just like a failure of hardware, factors of environmental, depleted batteries, intermittent radio interference, different radio transmission ranges, or the addition of sensors nodes. Because of this, applications need to capable of reconfiguring themselves as network topology evolves.

2.4.4.      Heterogeneity

Heterogeneity will take place in device capabilities, due to sensing, computation, and communication. This heterogeneity may have several essential design consequences.

2.4.5.      Programmability

Programmability means modifying or replacing part or the entire image of the code on one or more than one of the nodes including WSN. It is compulsory when WSNs need to upgrades the firmware, for instance, sensor drivers to entertain patches or new sensors to fix present bugs. The code download capacity at run time is generally accepted system requirement. Therefore, re-programmability of a network is desired; and doing so in communication and energy conservative form stays a challenge.

2.4.6.      Privacy and security

The sensitivity of the information on large collected, scale and prevalence by networks of the wireless sensor. Moreover, their possible deployment in locations of hostile. This gives rise to the crucial final challenge of confirming both security and privacy [5] [6] [9].

2.3.     Routing Protocols Classification in WSNs

Several types of categorization have been done on routing protocols in networks of Wireless Sensor. One of the categorizations is based on how the source discovers the direction to the target. A reactive protocol makes a path based on the demand, but a proactive protocol of routing keeps maintain a direction even in the absence of traffic. Whereas a protocol of hybrid combines both [11].

2.5.1.      Flat Routing Protocols

In flat protocols of routing, every node hold has same assignment and mutually with each other; it is not practical to specify a universal identification to each node in a network due to a huge number of such nodes, which give rises to the data-centric approach. Also, the base station in this approach sends queries to the sensor node deployed in a particular area and from the sensors nodes waits for data used in that area.

2.5.2.      Hierarchical Routing Protocols

The advantage in Hierarchical protocols of routing is efficient and scalability point to point communication through a tiny route state. The hubs are parceled into low vitality hub and higher vitality hubs. In this, the more upper energy node is used for sending and processing of the data whereas for sensing the low energy nodes are used. The nodes in this category play different roles according to the topology of the network [12].

2.5.3.      Location-based Routing Protocols

This type of protocol of routing, sensor nodes are recognized in the network with the help of address. Location of sensor node information is needed to locate the distance of node and each other due to which consumption of energy can be estimated. The separation between the two specific nodes is calculated with the help of the incoming signal strength location of the nodes in a network which can be obtained with the help of GPS.

2.5.4.      Multipath Routing Protocols

The links are highly dynamic by wireless links, and the ability of the multi-hop path is restricted. Hence, for the reliable and efficient high transmission rate of data, multidirectional protocols of routing were installed. 

2.5.5.      Network and QoS aware Routing Protocols

Few models of protocols the route solves and set up them as a problem of network flow. QoS alert protocols suppose an end to end delay while developing the path. Protocols which targets at maximum lifetime suppose the residual energy of the transmission and the nodes link’s cost earlier the route development [13].

2.4.     The Architecture of Sensor Networks Communication

Usually, sensor nodes distributed in the domain sensors as Fig 2.4 shows. Each of these separate sensor nodes can gather data back and data path to the end and the sink users. Data are retransmitted backward to the final user by a multihop infrastructure. Less architecture with the sink as Fig 2.3 shows. The communication between the sink and node task manager could be via Satellite and the Internet [8].  

2.3. Sensor nodes scattered in a sensor field

All sensor nodes and sink used the stack of the protocol in Fig 2.4 is given. This protocol stack integrates routing and power awareness, combine data with protocols of networking, communicates power efficiently out of the wireless medium, and raise sensor nodes efforts that are cooperative. The layers in the protocol stack are the data link layer, application layer, physical layer, network layer, and transport layer.

Figure 2.4. The sensor networks protocol stack

2.5.1.      Physical Layer

This layer is accountable for the generation of a carrier frequency, the selection of frequency, signal detection, modulation, and encryption of the data.

2.5.2.      Data Link Layer

This layer is in control of the data multiplexing streams, the detection of a data frame, medium access, and controlling error. It guarantees reliable point-to-point as well as point-to-multipoint communication connections in the network.

2.5.2.1.                        Medium Access Control

The Medium Access Control protocol in multihop wireless sensor network has to attain two objectives. First, the creation of network infrastructure. Since a huge amount of sensor nodes are heavily dispersed in sensors field, Media access control scheme must found links of communication for transfer of data. This forms the necessary infrastructure required for the process of communication of wireless hop by hop and allows the sensor network self-organizing capability. Second, is to impartially and efficiently portion resources of communication among node sensors.

2.5.2.2.                        Error Control

Another the error control of transmission data is a layer of an essential function of the data link layer is. Low-complexity encoding and decoding with error control codes simple may present better sensor networks solutions. In the structure of such type of scheme, it is essential to have better knowledge about the implementation and characteristics techniques of the channel.

2.5.3.      Network Layer

The protocol routing is responsible for defining the direction that will be taken by the messages, executing any in-network data aggregation to minimize the number of messages conveyed the whole of the network and supporting any imposed requirements of real-time communication.

2.5.4.      Transport Layer

This layer is mainly required when the purpose of the system to be gain access to all over the Internet or other types of networks. UDP/TCP type protocols encounter most of the requirements.

2.5.5.      Application Layer

Depending on the sensing tasks, on the application layer, several types of application software can be used and built. It's responsible for the following administrative tasks: Describing the protocols relative to aggregation of data, and clustering to the sensor nodes, data exchange associated with the algorithms of location finding, synchronization of time of the sensor nodes, Querying the sensor network configuration and the status of nodes, and sensor network reconfiguring, Authentication, distribution of the keys, and data communications security.

2.5.6.      Cross-layering

Current protocol of WSN structures is primarily established on a layered methodology. However, these protocols might obtain high performance regarding the related metrics of each layer; they are not simultaneously improved to maximize the comprehensive performance of network while reducing the energy disbursement because of low energy constraints low latency and consumption. Therefore, instead of having different layers, we can require cross-layering where layers are combined. The approach of cross-layer has used in two essential contexts in Wireless Sensor Networks. In several papers, the interaction of cross-layer is supposed, where layered the structure of tradition is preserved, whereas each layer is educated about the situations of other layers. Although, each layer mechanism still stay robust. Moreover, there is still numerous to be acquired by rethinking the network layers technique in a combined way to offer a module of single communication for effective communication in WSNs.

2.1.     Summary

This chapter presents the networks of wireless sensor and outlines the architecture of the wireless sensor node. Also, it discusses the challenges that face the designers of WSNs. A deep general idea of the several domains of WSN applications is also presented. Finally, it provides a quick view on WSN communication model and protocol stack.