An overview of a wireless sensor network communication

An Overview of a Wireless SensorNetwork Communication Architecture& their Design ChallengesN. R. Pawar1, P. D. Bageshwar#, O. P. Chimankar* & Devraj

Singh$

1Department of Physics, Arts, Commerce & Science College,Maregaon-445 303, India#Department of Physics, M. M. College, Darwha-445 202, India*Department of Physics, RTM Nagpur university, Nagpur-440033, India$Department of Applied Physics, Amity School of Engineering &Technology, New Delhi 110 061, IndiaCorresponding Author: [email protected],

[email protected], [email protected]

• Abstract• In this paper, we investigate the importance of wireless

sensor network communication architecture andexplain the key issues that are faced in the design ofthe wireless sensor network monitoring strategy. Wereview the communication protocols and algorithms inMAC layer and network layer, and examine thestandard components in the sensor networkarchitecture. Based on the survey, we recommend themulti-hop and cluster based sensor networkcommunication architecture for the proposedapplications. We further study the MAC layer andnetwork layer communication protocols for wirelesssensor networks with the applications for wide arealarge scale soil moisture estimation, wetlandsmonitoring, etc

• Introduction:• Wireless Sensor Networks (WSNs) investigates the properties of

network sensors with wireless communication. The importance of wireless sensor networks arises from their capability for detailed monitoring in remote and inaccessible locations where it is not feasible to install conventional wired infrastructure. Wireless Sensor Networks play important role in disaster prevention and relief, environmental monitoring, navigation, logistics tracking, medical applications, military observation and intelligence gathering, etc. There are a number of research challenges associated with wireless sensor communication arising from the limited capabilities of low cost sensor node hardware and the common requirement for nodes to operate for long time periods [1&2]. The distributed nature of wireless sensor networks makes energy-efficient protocol design particularly challenging. There are unique problems in self configuration, network discovery, medium access control and multi-hop routing. Cross-layer design is required to bring about stable and energy-efficient solutions. The 915 MHz and 2.4 GHz industrial, scientific and medical (ISM) band has been widely suggested for sensor networks [3].

• Wireless Sensor Networks Communication Architecture:

• A wireless sensor network (WSN) is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations. Wireless Sensor Networks are networks that consist of sensors which are distributed in an ad hoc manner. These sensors work with each other to sense some physical phenomenon and then the information gathered is processed to get relevant results. Wireless sensor networks consist of protocols and algorithms with self-organizing capabilities.

• Wireless Sensor Networks CommunicationArchitecture:

• A wireless sensor network (WSN) is a wirelessnetwork consisting of spatially distributedautonomous devices using sensors to cooperativelymonitor physical or environmental conditions, suchas temperature, sound, vibration, pressure, motionor pollutants, at different locations. Wireless SensorNetworks are networks that consist of sensorswhich are distributed in an ad hoc manner. Thesesensors work with each other to sense somephysical phenomenon and then the informationgathered is processed to get relevant results.Wireless sensor networks consist of protocols andalgorithms with self-organizing capabilities.

• Example of WSN:

• Outdoor: WSN Nodes & fitness parameter sensor, WSN Nodes & fitness parameter sensor

• Indoor: WSN Nodes & vital parameter sensor, WSN Nodes & fitness parameter sensor

• Service Centre: Operator Network, Home Gateway, Mobile Gateway

• Operations in a Wireless Sensor Network Communication Architecture:

• A basic sensor node typically comprises of five main components and they are namely

• controller, memory, sensors and actuators, communication device and power supply ( Fig.1). A controller is to process all the relevant data, capable of executing arbitrary code. Memory is used to store programs and intermediate data. Sensors and actuators are the actual interface to the physical world. These devices observe or control physical parameters of the environment. The communication device sends and receives information over a wireless channel. And finally, the power supply is necessary to provide energy. In wireless sensor networks, power consumption efficiency is one of the most important design considerations. Therefore, these intertwined components have to operate and balance the trade-offs between as small energy consumption as possible and also the need to fulfill their tasks [4-7].

• Microcontrollers used in several wireless sensor node prototypes are Atmel processor and

• Intel Armstrong processors, etc. In this project, we have consolidated a list of sensor nodes in the literature (Table-1). It is noted that mica 2 mote and mica Z mote, and mica 2 dot motes are appropriate nodes suitable for large area wetland monitoring application because of its characteristics. These three motes operation range can out reached up to 500 feet (152 m), and has the lifetime up to 7 years.

• Communication device is used to exchange data between individual nodes. The communication medium between the two nodes is through radio frequencies (wireless medium). Radio frequency-based communication fits the requirements of most wireless sensor applications because it provides relatively long range and high data rates, acceptable error rates at reasonable energy expenditure, and does not require line of sight between sender and receiver.

•

• For actual communication, both a transmitter and a receiver are required in a sensor node.

• The essential task is to convert a bit stream coming from a microcontroller and convert them to and from radio waves. As half duplex operation is recommended in wireless sensor network a transceiver is generally used. In the transceiver, circuitry includes modulation, demodulation, amplifiers, filters, mixers. The table below summarizes the frequency bands, modulation and data parameters that could be used in the communication medium.

• The transceiver must provide an interface that allows the medium access control (MAC)

• layer to initiate frame transmissions and to hand over the packet from the main memory of the sensor node into the transceiver (or a byte or a bit stream, with additional processing required on the micro controller). In other direction, incoming packets must be streamed into buffers accessible by MAC protocol [8&9].

•

Sensor node hardware components

MEMORY

CONTROLLER SOURCE/SINKCOMMUNICATION DEVICE

POWER SUPPLY

Phy ( Mhz) Frequency band(Mhz)

Chip rate(kchi/s)

Modulation Bit rate Symbol rate(ksymbol/s)

868/915 868-868.6 300 BPSK 20 20

902-928 600 BPSK 40 40

2450 2400-2483.5 2000 O-QPSK 250 62.5

• Characteristics of Wireless Sensor Networks:

• Wireless Sensor Networks mainly consists of sensors. These sensors are low power, limited memory, energy constrained due to their small size, wireless networks can also be deployed in extreme environmental conditions and may be prone to enemy attacks and although deployed in an ad hoc manner they need to be self organized and self healing and can face constant reconfiguration.

• Precision Agriculture: Precision agriculture aims at making cultural operations more efficient, while reducing environmental impact. The information collected from sensors is used to evaluate optimum sowing density, estimate fertilizers and other inputs needs, and to more accurately predict crop yields.

• Monitoring Objects:

• (i) Structural Monitoring (ii) Eco-physiology (iii) Condition-based Maintenance (iv) Medical Diagnostics (v) Urban terrain mapping.

• Applications of Wireless Sensor networks:

• The applications can be divided in three categories:

• Monitoring of an area 2. Monitoring of an objects 3. Monitoring of both area and objects.

• Monitoring Area:

• (i) Environmental and Habitat Monitoring (ii) Precision Agriculture (ii) Indoor Climate Control (iv) Military Surveillance (v) Treaty Verification (vi) Intelligent Alarms

• Condition-based Maintenance:

• (i) Intel fabrication plants (ii) Sensors collect vibration data, monitor wear and tear; report data in real-time (iii) Reduces need for a team of engineers; cutting costs by several orders of magnitude

• Monitoring Interactions between Objects and Space:

• (i) Wildlife Habitats (ii) Disaster Management (iii) Emergency Response (iv) Ubiquitous Computing (v) Asset Tracking (vi) Health Care (vii) Manufacturing Process Flows (viii) The Zebra Net Project

• Design Challenges:

• Heterogeneity: The devices deployed maybe of various types and need to collaborate with each other.

• Distributed Processing: The algorithms need to be centralized as the processing is carried out on different nodes

• Low Bandwidth Communication: The data should be transferred efficiently between sensors

• Large Scale Coordination: The sensors need to coordinate with each other to produce required results.

• Utilization of Sensors: The sensors should be utilized in a ways that produce the maximum performance and use less energy.

• Real Time Computation: The computation should be done quickly as new data is always being generated.

• Operational Challenges of Wireless Sensor Networks:

• Energy Efficiency, Limited storage and computation, Low bandwidth and high error rates, errors in common wireless communication, noisy measurements, node failure are expected, scalability to a large number of sensor nodes and survivability in harsh environments

• Future of WSN:

• In future we can use WSN for:

• Design smart house and office by using Sensors controlling appliances and electrical devices.

• Health Monitors to detect Glucose, Heart rate, Cancer detection, Chronic Diseases like artificial retina & cochlear implants.

• Hospital Sensors to Monitor vital signs, Record anomalies, etc

• Military: Remote deployment of sensors for tactical monitoring of enemy troop movements.

• Industrial & Commercial to detect Agricultural Crop Conditions, Inventory Tracking, In-Process Parts Tracking, Automated Problem Reporting, RFID –Theft Deterrent and Customer Tracing, Plant Equipment Maintenance Monitoring, Traffic Management & Monitoring.

• Future cars could use wireless sensors to handle Accidents, handle Thefts, etc

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