**3.1 The physical layer of the IEEE 802.15.4**

Buratti et al. [4] in their study reported that "the IEEE 802.15.4" main system comprises of a "radio frequency (RF) transceiver and the procedure stack," as illustrated in **Figure 2**.

According to Buratti et al. [4], the "802.15.4 physical layer" functions basically in three diverse unrestricted/unlicensed bands (as well as with the diverse modalities) in respect to the geographical location where the system is positioned or installed. Nevertheless, spread spectrum procedures are somewhere required for the reduction of the interference extent/range in shared unrestricted/unlicensed. The "IEEE 802.15.4" requires a total of "27 half-duplex channels" transversely on the three frequency bands. The organisation is as follows:


The superlative transmission extent is calculated bearing in mind that, even though any legitimately suitable power is allowed, the "IEEE 802.15.4-compliant devices" ought to be capable of communicating and transmitting at −3 dBm. Giving, the energy efficiency challenges, short rate and short duty cycle are given. The "IEEE

**Figure 2.** *ZigBee procedure stack.*

802.15.4-compliant devices" are dynamic only during a brief period and the standard permits some devices to function with both the transmitter and the receiver inactive for about a duration of 99% [4].

#### **3.2 The IEEE 802.15.4 MAC layer**

The "IEEE 802.15.4" employs a procedure built on the CSMA/CA algorithm, which entails compensating attention to the channel before transmission for the reduction of the possibility of collisions with other continuing transmissions. The "IEEE 802.15.4" describes two diverse operational approaches, viz.; the "beaconenabled (BE) and the non-beacon-enabled (nBE)," which correspond to two diverse channel access machineries.

The nBE approach nodes use an unpetitioned CSMA/CA procedure for the assessment of the channel and transmission of their packets [36]. The algorithm is executed by employing units of time (UT) known as "back off periods (BPs)." Foremost, each node will interrupt any actions for a haphazard number of BPs. Subsequent on this interruption, channel sensing is achieved for one UT. If the channel is discovered free, the node instantly starts the transmission; but if, in its place, the channel is busy the node enters again in the back off situation. There occur an uppermost number of times the node could attempt in accessing the channel. When this uppermost is attained, the algorithm ends and the transmission could hardly occur. According to reports from the EEE 802.15.4 Standard Part 15.4, in the BE mode (instead, the access to the channel is accomplished through a super frame [SF]), beginning with a packet, known as "beacon," transmitted by wireless PAN coordinator. The SF could contain an indolent portion, permitting nodes to go in sleeping mode, while the active portion is shared into two portions; "the contention access period (CAP) and the contention free period (CFP)," composed of what is known as the "guaranteed time slots (GTSs)," that could be allocated by the sink to precise nodes. However, the use of the GTSs is discretionary.

#### **4. Applications of wireless sensor networks (WSNs)**

According to Buratti et al. [4], the various conceivable applications of WSNs to every sectors globally is essentially boundless, from environmental monitoring and management [37], medical and health care services [38], as well as other aspects such as positioning and tracking [39], localization, logistic. Strappingly, it is imperative to emphasise that the benefits and applications affects the choice of the wireless machinery to be employed.

As soon as the requirements of the application are set, the network designers need to select and choose the machinery which allows the gratification of these requirements. Hence, the knowledge of the structures, benefits and difficulties of the various machineries is fundamental. As a result of the significance of the relationship between the requirements for application and the machineries, this section will attempt to briefly give an outline of the some of the utmost applications of WSNs.

As stated earlier, WSNs have gained substantial admiration as a result of their flexibility in resolving issues in different application fields and have all it takes to change our world in several diverse ways. Reportedly, WSNs have been efficaciously employed in several application domains [1–4, 7, 13, 26–29, 40–44] such as:

**Military Applications:** Possibly, WSNs is an essential fragment of military intelligence, facility, control, communications, computing, frontline surveillance, investigation and targeting systems.

**31**

*Wireless Sensor Networks: Applications and Challenges DOI: http://dx.doi.org/10.5772/intechopen.93660*

of possible congestion and traffic difficulties.

discovery/detection.

cal site visitations.

involve in wiring.

reduction of wastes.

(energy source).

**5. Design challenges in WSNs**

**Applications in Area Monitoring:** In the aspect, the sensor nodes are positioned over an area where some display is to be observed. When the sensors notice the occurrence being observed (such as temperature, pressure etc), the occurrence is conveyed to one of the base stations (BSs), which then takes action appropriately. **Transportation Applications:** Instantaneous traffic statistics is being composed by WSNs to later forage transportation models and keep the drivers on alert

**Medical/Health Applications:** Some of the medical/health benefits of WSNs

**Structural Applications:** WSNs can be employed for monitoring the movement of diverse structural projects such as buildings and other infrastructural projects like flyovers, bridges, roads, embankments, tunnels etc., allowing manufacturing/ engineering practices to monitor possessions remotely without necessarily visiting the sites, and this would reduce expenses that would have been incurred from physi-

**Agricultural Applications:** The employment of WSNs has been reported assist

**Industrial Applications:** WSNs have been advanced for "Technological Condition-based Maintenance (TCBM)" since they could offer momentous cost reductions/investments and allow innovative functionalities. In wired classifications, the installation of adequate sensors is habitually limited by the amount

farmers in various aspects such as the maintenance of wiring in a problematic environment, irrigation mechanisation which aids more resourceful water use and

Reportedly, there are several challenges placed by the disposition of sensor networks [1, 2, 7, 46–49], which are segment of those that are initiated in WSN systems. The sensor nodes interrelate over the wireless, lossy spots without substructure. Another projecting challenge is the one that is related to the constrained, customarily non-renewable natural resource; that is the energy basis of the sensor nodes. As reported by Akyildiz et al. [1, 2], so as to enjoy the complete benefit of the generation of the WSNs, the techniques need to be premeditated from the beginning with the aim of efficient monitoring and management of the natural resources

According to Matin and Islam [7], the specific design challenges in WSNs are: **Scalability:** SNs differ in scale from some nodes to possibly several numbers. Furthermore, the deployment density is correspondingly adjustable. In the process

are in the areas of diagnostics, investigative, and drug administration as well as management, supporting interfaces for the incapacitated, integrated patient monitoring and management, tele-monitoring of human physiological information, and tracking and monitoring medical practitioners or patients inside the medical facility. According to Nwankwo et al. [45] nanoinformatics and nanomedicine are

now beginning to advance in clinical applications via the use of biosensors. **Environmental Applications:** The term "Environmental Sensor Networks (ESNs)" has developed to cover several benefits of WSNs to environmental and earth science study. This comprises of sensing oceans, seas, glaciers, atmosphere, volcanoes, forest, etc. However, there are presently some biosensors that have been developed for use in agricultural and environmental sustainability [29]. Some other key aspects are; air contamination monitoring and management, forest fires discovery/detection, greenhouse (GH) monitoring and management, and Landslide *Wireless Sensor Networks - Design, Deployment and Applications*

for about a duration of 99% [4].

channel access machineries.

**3.2 The IEEE 802.15.4 MAC layer**

802.15.4-compliant devices" are dynamic only during a brief period and the standard permits some devices to function with both the transmitter and the receiver inactive

The "IEEE 802.15.4" employs a procedure built on the CSMA/CA algorithm, which entails compensating attention to the channel before transmission for the reduction of the possibility of collisions with other continuing transmissions. The "IEEE 802.15.4" describes two diverse operational approaches, viz.; the "beaconenabled (BE) and the non-beacon-enabled (nBE)," which correspond to two diverse

The nBE approach nodes use an unpetitioned CSMA/CA procedure for the assessment of the channel and transmission of their packets [36]. The algorithm is executed by employing units of time (UT) known as "back off periods (BPs)." Foremost, each node will interrupt any actions for a haphazard number of BPs. Subsequent on this interruption, channel sensing is achieved for one UT. If the channel is discovered free, the node instantly starts the transmission; but if, in its place, the channel is busy the node enters again in the back off situation. There occur an uppermost number of times the node could attempt in accessing the channel. When this uppermost is attained, the algorithm ends and the transmission could hardly occur. According to reports from the EEE 802.15.4 Standard Part 15.4, in the BE mode (instead, the access to the channel is accomplished through a super frame [SF]), beginning with a packet, known as "beacon," transmitted by wireless PAN coordinator. The SF could contain an indolent portion, permitting nodes to go in sleeping mode, while the active portion is shared into two portions; "the contention access period (CAP) and the contention free period (CFP)," composed of what is known as the "guaranteed time slots (GTSs)," that could be allocated by the sink

According to Buratti et al. [4], the various conceivable applications of WSNs to every sectors globally is essentially boundless, from environmental monitoring and management [37], medical and health care services [38], as well as other aspects such as positioning and tracking [39], localization, logistic. Strappingly, it is imperative to emphasise that the benefits and applications affects the choice of the

As soon as the requirements of the application are set, the network designers need to select and choose the machinery which allows the gratification of these requirements. Hence, the knowledge of the structures, benefits and difficulties of the various machineries is fundamental. As a result of the significance of the relationship between the requirements for application and the machineries, this section will attempt to briefly give an outline of the some of the utmost applications

As stated earlier, WSNs have gained substantial admiration as a result of their flexibility in resolving issues in different application fields and have all it takes to change our world in several diverse ways. Reportedly, WSNs have been efficaciously

employed in several application domains [1–4, 7, 13, 26–29, 40–44] such as: **Military Applications:** Possibly, WSNs is an essential fragment of military intelligence, facility, control, communications, computing, frontline surveillance,

to precise nodes. However, the use of the GTSs is discretionary.

**4. Applications of wireless sensor networks (WSNs)**

wireless machinery to be employed.

investigation and targeting systems.

**30**

of WSNs.

**Applications in Area Monitoring:** In the aspect, the sensor nodes are positioned over an area where some display is to be observed. When the sensors notice the occurrence being observed (such as temperature, pressure etc), the occurrence is conveyed to one of the base stations (BSs), which then takes action appropriately.

**Transportation Applications:** Instantaneous traffic statistics is being composed by WSNs to later forage transportation models and keep the drivers on alert of possible congestion and traffic difficulties.

**Medical/Health Applications:** Some of the medical/health benefits of WSNs are in the areas of diagnostics, investigative, and drug administration as well as management, supporting interfaces for the incapacitated, integrated patient monitoring and management, tele-monitoring of human physiological information, and tracking and monitoring medical practitioners or patients inside the medical facility. According to Nwankwo et al. [45] nanoinformatics and nanomedicine are now beginning to advance in clinical applications via the use of biosensors.

**Environmental Applications:** The term "Environmental Sensor Networks (ESNs)" has developed to cover several benefits of WSNs to environmental and earth science study. This comprises of sensing oceans, seas, glaciers, atmosphere, volcanoes, forest, etc. However, there are presently some biosensors that have been developed for use in agricultural and environmental sustainability [29]. Some other key aspects are; air contamination monitoring and management, forest fires discovery/detection, greenhouse (GH) monitoring and management, and Landslide discovery/detection.

**Structural Applications:** WSNs can be employed for monitoring the movement of diverse structural projects such as buildings and other infrastructural projects like flyovers, bridges, roads, embankments, tunnels etc., allowing manufacturing/ engineering practices to monitor possessions remotely without necessarily visiting the sites, and this would reduce expenses that would have been incurred from physical site visitations.

**Industrial Applications:** WSNs have been advanced for "Technological Condition-based Maintenance (TCBM)" since they could offer momentous cost reductions/investments and allow innovative functionalities. In wired classifications, the installation of adequate sensors is habitually limited by the amount involve in wiring.

**Agricultural Applications:** The employment of WSNs has been reported assist farmers in various aspects such as the maintenance of wiring in a problematic environment, irrigation mechanisation which aids more resourceful water use and reduction of wastes.

## **5. Design challenges in WSNs**

Reportedly, there are several challenges placed by the disposition of sensor networks [1, 2, 7, 46–49], which are segment of those that are initiated in WSN systems. The sensor nodes interrelate over the wireless, lossy spots without substructure. Another projecting challenge is the one that is related to the constrained, customarily non-renewable natural resource; that is the energy basis of the sensor nodes. As reported by Akyildiz et al. [1, 2], so as to enjoy the complete benefit of the generation of the WSNs, the techniques need to be premeditated from the beginning with the aim of efficient monitoring and management of the natural resources (energy source).

According to Matin and Islam [7], the specific design challenges in WSNs are:

**Scalability:** SNs differ in scale from some nodes to possibly several numbers. Furthermore, the deployment density is correspondingly adjustable. In the process of gathering data with high resolution, the node density could reach the extent where a node has numerous neighbours in their range of transmission. The protocols positioned in SNs should to be scalable to these extents and should be able to maintain and preserve performance effectively.

**Culpability Tolerance:** SNs are susceptible and regularly deployed in hazardous environment. The failure in the nodes are supposedly due to hardware complications, physical impairment or through gruelling their energy source. Expectedly, the node failures are much higher than the one generally considered in strengthened or infrastructure-built WNs. The protocols positioned in a SN should be talented in detecting these failures in the nodes instantly and should be strongly robust in handling a comparatively huge quantities of the node failures while maintaining and preserving the complete functionality of the network system. This is particularly relevant to the routing protocol project, which ensure that alternative paths are accessible for redirecting of the packets. However, diverse deployment situations pose diverse culpability tolerance necessities.

**Cost of Production:** Due to several deployment models consider the SNs to be disposable devices, sensor networks could possibly contend with traditional information gathering methods only if the specific SNs could be produced economically. The target price intended for a NS should preferably be very low in price.

**Hardware Limitations:** At least, every NS needs to have a detecting component (sensing component), a processing component, a transmission component and a power source component. In some instant, the nodes could possibly have numerous built-in sensors or extra devices like a localization arrangement that assist the location-aware routing. Nevertheless, every extra functionality emanates with extra cost and amplifies the power consumption rate and physical dimensions of the node. Consequently, extra functionality needs to be continuously balanced in contrast to the cost and low-power requirements.

**Topology of the Sensor Network:** Even though WSNs have advanced in several aspects, the networks incessantly experience some constrained resources in terms of energy resources, computational power, storage (memory) and communications competences. Among all these aforementioned constrictions, energy resource is of utmost significance, and this is confirmed by the huge quantities of algorithms, procedures, and protocols that have been established for saving energy, and by this means encompass the generation of the network. Reportedly, maintenance of the topology is one of the utmost issues that could assist in the reduction of the energy consumption rates in WSNs [22].

**The Media of Transmission**: The communication and interaction among the nodes is ordinarily implemented by means of the radio communication over the prevalent ISM bands. Nevertheless, some sensor networks employ optical communication or infrared communication, with that of the infrared having the advantage of being strong and effectively free of interference.

**The Consumption of Power:** As previously stated, most of the challenges of WNSs mainly centred on the inadequate power resources. The magnitude of the nodes restricts the magnitude of the source of power (battery). Hence, in designing the both the software and hardware, there the needs to cautiously contemplate on the issues of resourceful energy use. For example, data compression could possibly reduce the quantity of energy used for radio transmission, but uses extra energy for the manipulation, computation or/and filtering. Also, the energy procedure depends on the application; where in some applications, it could be suitable to turn off a subdivision of nodes so as to preserve and conserve energy whereas other applications need all nodes to operate instantaneously.

According to Puccinelli and Haenggi [28], sensor networks offer an influential combination of disseminated sensing, computing and communication. They offer

**33**

**Notes**

*Wireless Sensor Networks: Applications and Challenges DOI: http://dx.doi.org/10.5772/intechopen.93660*

some of the challenges of WSNs.

cantly, the application necessities.

**Acknowledgements**

**Conflict of interest**

There is no conflict to declare.

public, commercial, or not-for-profit sectors.

studies and publications were used for this chapter.

**6. Conclusion**

themselves to immeasurable applications and simultaneously offer several challenges as a result of their distinctiveness, essentially the rigorous energy limitations to which sensor networks are characteristically subjected. The distinguishing traits of sensor networks have a direct influence on the hardware design (HWD) of the nodes at least four levels namely; "power source, processor, communication hardware, and sensors." There are several HWD platforms that have been established in testing the innumerable ideas and concepts produced by various researchers and in implementing the applications to effectively suit all fields of study especially the scientific and technological aspects [50]. Presently, in the design and deployment of WSNs, several programming procedures have been projected, of which prominence are habitually on issues of low-level systems. Nevertheless, as stated earlier, for the simplification of the design and deployment of WSNs and abstract from technological LLB specifics, some HLB procedures have been anticipated, developed and established for its resolutions. According to BenSaleh et al. [3], applying the model-driven engineering (MDE) technique is becoming an auspicious solution in particular and these HLB procedures would be of great assistance in easing the design and deployment as well as mitigate

This chapter discusses some of the utmost issues of WSNs, ranging from applications to challenges on the technological points of view. Essentially, in designing a WSN it is required to describe the utmost appropriate technology to be employed and the communication procedures (such as signal processing, topology, approaches, etc). These selections are subject to various factors, and most signifi-

The first section of the chapter was keen in discussing the description of some of the limitations that should be fulfilled by the WSN and the various aspects that should be considered for designing a WSN. The proceeding section, was connected to the possibly authentic selections that could be completed, in terms of machineries. The purpose is to assist designer of WSNs in selecting or choosing of the utmost appropriate technology. The consideration was primarily focused on standard of the IEEE 802.15.4, for which also several possible performance levels are make available. Conclusively, it is suggested that a vision on imminent trends of research and prospects such as MDE techniques on WSNs should be put in place.

The authors express their appreciation to authors and agencies whose research

This research has not received any specific grant from funding agencies in the

*Wireless Sensor Networks: Applications and Challenges DOI: http://dx.doi.org/10.5772/intechopen.93660*

themselves to immeasurable applications and simultaneously offer several challenges as a result of their distinctiveness, essentially the rigorous energy limitations to which sensor networks are characteristically subjected. The distinguishing traits of sensor networks have a direct influence on the hardware design (HWD) of the nodes at least four levels namely; "power source, processor, communication hardware, and sensors." There are several HWD platforms that have been established in testing the innumerable ideas and concepts produced by various researchers and in implementing the applications to effectively suit all fields of study especially the scientific and technological aspects [50].

Presently, in the design and deployment of WSNs, several programming procedures have been projected, of which prominence are habitually on issues of low-level systems. Nevertheless, as stated earlier, for the simplification of the design and deployment of WSNs and abstract from technological LLB specifics, some HLB procedures have been anticipated, developed and established for its resolutions. According to BenSaleh et al. [3], applying the model-driven engineering (MDE) technique is becoming an auspicious solution in particular and these HLB procedures would be of great assistance in easing the design and deployment as well as mitigate some of the challenges of WSNs.

#### **6. Conclusion**

*Wireless Sensor Networks - Design, Deployment and Applications*

maintain and preserve performance effectively.

pose diverse culpability tolerance necessities.

contrast to the cost and low-power requirements.

of being strong and effectively free of interference.

applications need all nodes to operate instantaneously.

consumption rates in WSNs [22].

of gathering data with high resolution, the node density could reach the extent where a node has numerous neighbours in their range of transmission. The protocols positioned in SNs should to be scalable to these extents and should be able to

**Culpability Tolerance:** SNs are susceptible and regularly deployed in hazardous environment. The failure in the nodes are supposedly due to hardware complications, physical impairment or through gruelling their energy source. Expectedly, the node failures are much higher than the one generally considered in strengthened or infrastructure-built WNs. The protocols positioned in a SN should be talented in detecting these failures in the nodes instantly and should be strongly robust in handling a comparatively huge quantities of the node failures while maintaining and preserving the complete functionality of the network system. This is particularly relevant to the routing protocol project, which ensure that alternative paths are accessible for redirecting of the packets. However, diverse deployment situations

**Cost of Production:** Due to several deployment models consider the SNs to be disposable devices, sensor networks could possibly contend with traditional information gathering methods only if the specific SNs could be produced economically.

**Hardware Limitations:** At least, every NS needs to have a detecting component (sensing component), a processing component, a transmission component and a power source component. In some instant, the nodes could possibly have numerous built-in sensors or extra devices like a localization arrangement that assist the location-aware routing. Nevertheless, every extra functionality emanates with extra cost and amplifies the power consumption rate and physical dimensions of the node. Consequently, extra functionality needs to be continuously balanced in

**Topology of the Sensor Network:** Even though WSNs have advanced in several aspects, the networks incessantly experience some constrained resources in terms of energy resources, computational power, storage (memory) and communications competences. Among all these aforementioned constrictions, energy resource is of utmost significance, and this is confirmed by the huge quantities of algorithms, procedures, and protocols that have been established for saving energy, and by this means encompass the generation of the network. Reportedly, maintenance of the topology is one of the utmost issues that could assist in the reduction of the energy

**The Media of Transmission**: The communication and interaction among the nodes is ordinarily implemented by means of the radio communication over the prevalent ISM bands. Nevertheless, some sensor networks employ optical communication or infrared communication, with that of the infrared having the advantage

**The Consumption of Power:** As previously stated, most of the challenges of WNSs mainly centred on the inadequate power resources. The magnitude of the nodes restricts the magnitude of the source of power (battery). Hence, in designing the both the software and hardware, there the needs to cautiously contemplate on the issues of resourceful energy use. For example, data compression could possibly reduce the quantity of energy used for radio transmission, but uses extra energy for the manipulation, computation or/and filtering. Also, the energy procedure depends on the application; where in some applications, it could be suitable to turn off a subdivision of nodes so as to preserve and conserve energy whereas other

According to Puccinelli and Haenggi [28], sensor networks offer an influential combination of disseminated sensing, computing and communication. They offer

The target price intended for a NS should preferably be very low in price.

**32**

This chapter discusses some of the utmost issues of WSNs, ranging from applications to challenges on the technological points of view. Essentially, in designing a WSN it is required to describe the utmost appropriate technology to be employed and the communication procedures (such as signal processing, topology, approaches, etc). These selections are subject to various factors, and most significantly, the application necessities.

The first section of the chapter was keen in discussing the description of some of the limitations that should be fulfilled by the WSN and the various aspects that should be considered for designing a WSN. The proceeding section, was connected to the possibly authentic selections that could be completed, in terms of machineries. The purpose is to assist designer of WSNs in selecting or choosing of the utmost appropriate technology. The consideration was primarily focused on standard of the IEEE 802.15.4, for which also several possible performance levels are make available. Conclusively, it is suggested that a vision on imminent trends of research and prospects such as MDE techniques on WSNs should be put in place.

#### **Acknowledgements**

The authors express their appreciation to authors and agencies whose research studies and publications were used for this chapter.

#### **Conflict of interest**

There is no conflict to declare.

#### **Notes**

This research has not received any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
