Proceedings of 2014 RAECS UIET Panjab University Chandigarh, 06 – 08 March, 2014
A Review of sensor networks: Technologies and applications Hemraj Sharma
Sukesha Sharma
University Institute of Engg. and Technology Panjab University Chandigarh, India
[email protected]
University Institute of Engg. and Technology Panjab University Chandigarh, India
[email protected]
Abstract— Sensing any change in the physical environment and delivering this real time information about the system to the remote station for analysis has created versatile applications. With the research and development in the science and technology new sophisticated wired and wireless technologies for sensing have been developed with time. This paper presents an overview of these technologies used for wired and wireless sensor networks. For wireless sensor network some features of zigbee, enOcean, wavenis, Z-wave, wifi and Bluetooth are discussed in this paper. Brief discussion of different applications of the sensor networks is also presented. Keywords—applications; technologies; wired sensor network; wireless sensor network.
I.
INTRODUCTION
Sensor network is a group of nodes which gathers data according to their specialty. The node contains the power source, microprocessor, external memory, sensors, analog to digital converter and transceivers. Microprocessors in the nodes perform the necessary operation on data prior to send it to the remote station. Microprocessor has limited internal memory. So the external memory is also provided in the node to store the sensing data. Sensors are the physical devices which collects the environmental data as the analog signal. Then this data is converted into the digital with the help of analog to digital converter present in the node. Transceiver is the device in the node which receives the control signal from the sender and sends the operator data from the sensors to the remote station. Power source provide the energy (electricity) to the node for its operation. This power source as a battery for the wireless sensor nodes or through cable connection for the wired sensor or the power can be generated with the some energy harvesting modes like solar cell etc. Sensor networks further can be divided into two types: 1.
Wired sensor network In the wired sensor networks power source is wired. The power is continuously supplied to the node. Moreover the data from /to transceiver is send/received using wired
978-1-4799-2291-8/14/$31.00 ©2014 IEEE
Fig. 1 Block Diagram of wireless Sensor Node
communication channel. These sensor networks are highly reliable and their applications are limited. Moreover they have mesh network of the wires connecting to the network which makes them complex to handle and increase their cost. 2. Wireless sensor networks In wireless sensor network the nodes are not connected with any wire. Transceivers wirelessly send /receive the data and control signals to the control center or from the control center. In wireless sensor networks communication channel is the frequency spectrum. Moreover the power source in these nodes is the battery. As these nodes are implemented in very far areas, batteries are changed after a long time. Therefore energy consumption issue is the main research topic for wireless sensor networks. Now the data gathered at the field location is transferred to the remote station through the transceiver by the wireless channel. There data is processed for the analysis and required actions are being taken. As shown in Fig.1 energy can be provided by three ways (battery, wire or energy harvesting module) to the sensor node. Data gathered by the sender node is sent to the remote station
through wireless channel. After processing data at the remote station action is taken according to the requirement. In the wireless sensor networks, the parameters which evaluate the performance of the network are packet delay, reliability, fault tolerance, energy consumption etc. Preference of these parameters changes from application to application. II. TECHNOLOGIES There are other different technologies which are used in the wireless sensor networks .these are –zigbee ,z-wave ,wavenis ,wifi,EnOcean,Bluetooth,Insteon,x10 etc. A. Zigbee This technology is built on the IEEE 802.15.4 media standard and this works from layer 3 to the application layer of the ISO-OSI model [1]. Its working frequencies are 868 MHz, 915 MHz, and 2.4 GHz and low bit rate transmission 20kbps, 40kbps and 250kbps respectively. Moreover it is low cost wireless network technology. It has short delay and provides faster response. It need 15ms to wake up from sleeping mode and only 30ms to access the network. For insurance of reliable data transfer it uses dynamic routing protocol. Generally mesh network topology is used for the interconnection of the nodes, as in this there are at least two pathways to connect each node. In mesh each node is self routed and able to connect to other nodes if needed. A large number of nodes can use zigbee at the same time. 65000 nodes can be supported at most in a zigbee network. It has low power consumption. Two AA batteries can be used for 6 month to 2 years duration in low power standby mode [2]. Its low power consumption is due to the PSK modulation techniques, increased sleeping time of the node and use of EEMAC algorithm on the MAC layer [3]. Zigbee operates up to a range 10 to 100 meter. There are three ways in which security is provided by the zigbee technology. It uses AES encryption for the high- level secure transfer of the data. It also has option of no security setting and using access control list. So these features of the zigbee technology provide a great scope for its use. B. EnOcean It is a wireless network technology which has been very successful in Europe. Its main focus is on the energy efficiency .To achieve this it does not use the normal communication reliability procedures like message acknowledgement and CSMA. EnOcean resolve this issue using very short messages which reduce the message collision probability and hence save energy avoiding the repetition of message several times. It is not a feature rich, able to handle adhoc networks and not very complex as it is equipped with the energy harvesting modules .Energy can be harvested from environmental resources like solar energy, temperature difference or vibration/motion. EnOcean uses direct media access control (MAC) scheme [4].
C. Wavenis It was made for ultra low power energy consumption and long range transmission of small amount of data. It has automated 2-way communication. It supports Asynchronous or synchronous operation depending on network size and application [5]. It has feature of easy network device setup. Every device using wavenis technology support repeater function upto 4 hops. Wavenis operates in license free ISM bands .It has following regulatory standards. 1. 868 MHz (EU EN 300-220) with strict duty cycle regulation. 2. 915 MHz (US FCC 15 247, 15-249) with mandatory signal spreading. 3. 433 MHz with no duty cycle restriction. Wavenis applications communicate at 19.2 Kbps [1]. D. X10 This protocol is used in smart homes and it is used for wired sensor networks. It uses electrical power lines to transmit message signals, incurs low cost and easy to install .It also has less data transfer rate-20 bps. Moreover X10 is inclined towards noise [6]. E. Insteon It is the modification of the legacy X10 and is backward compatible to X10. Insteon uses both radio frequency signals and the home's existing electrical wiring as the communication channel. It provides error detection and automatic error correction of the data packet. In the mesh network of the Insteon every device acts as a repeater-receives and sends the every message to all other devices on the network and they do not contain any routing tables. This technology operates with frequency 131 kHz on power lines and for wireless transmission radio frequencies used in US and Europe is 915MHz and 868MHz respectively but Radiofrequency used in Australia and New Zealand is 921MHz. It can support 16,777,216 maximum devices per network. Its new feature is wireless communication [7]. F. Z-wave It is a wireless communication standard designed for remotely controlled applications in residential and light commercial environments. Its speed is 40 kbps (915MHz) and reach is up to 30 meter in air and reduced indoor. It is widely adopted and uses 128-bit AES encryption for the security purpose and avoids interference with Wifi, Bluetooth and other systems that operate on crowded 2.4 GHz. It was developed by Denis Startup called Zen-Sys that was acquired by sigma designs in 2008 [1]. G. wifi It is a popular wireless technology based on IEEE 802.11 standards and used in home networks. Speed can reach from 11Mbps-300Mbps.Its adoption rate is extremely high .Wifi can be less secure than the wired connections. For
security purpose it uses Wifi protected access 2(WPA2) 802.11i [1]. Wifi has high power consumption as the data rates and range is high. Wireless access point using 802.11g and 802.11b has a range of 35 m in doors and 100m outdoors.
H. Bluetooth It is short range, wireless technology and is basically wire substitute. This technology is based on IEEE 802.15.1. It is very efficient and processing bandwidth is 1000-3000Kbps. It operates in the range 2400-2483.5 MHz and makes network of maximum 7 nodes and network called piconet [2]. Brief comparison of typical technologies is given in table I.
wireless
network
TABLE I. COMPARISON OF TYPICAL WIRELESS NETWORK TECHNOLOGIES Technologies Zigbee
z-wave
bluetooth
wavenis
Data rate
20,40,250kbps
40kbps
19.2kbps
Range (in meter) Application Area
10-100m
30m,in open air
10003000kbps 50m
Monitoring and control
Remote control application
Wire substitute
Standard
IEEE 802.15.4
Proprietary wireless communication standard
IEEE 802.15.1
Security
128 bit AES encryption
128 bit AES encryption
SAFER+ Block cipher
III.
Significant range Remote control and data monitoring Certified ETS300220, FCC15-247, 15-249 3DES, AES 128, RSA
APPLICATIONS
According to the specification of the sensors, area of applications of sensor networks is very versatile. Most of the population, at the present time is in the developing countries and main income source in these countries is agriculture. With the development of the technology in the past decades green house management agriculture introduced to increase the farm production efficiency and profitability by reducing unintended effects on green house environment. The necessary parameters like temperature, humidity and irrigation in the green house can be known by the wireless technology zigbee at low cost. zigbee module is used to continuously monitor the parameter data of the green house and send to the remote station where it is get operated on the LabView GUI Software and control signal send back to the green house to maintain the parameter value level [8]. Similar and extended functionality of the operations has been described in [9]. In this, the data gathered is put on the web portal and along with it the user feedbacks of the products, future market trends and the knowledge seminar
from the experts, data stored in the database for the future use has been included. A wireless sensor network has been proposed with the sensor which senses the pH value of the water of the river [10]. In this monitoring areas are divided into sub areas like area near water pump house(A), near factory industry(B), near agricultural land(C) and near residential area(D). In each area with the cluster of sensor nodes a head node is located. Sensor nodes are deployed at the different depths of the river to measure the water quality at other levels also. A Head node from the respective clusters takes the data from other nodes and sends it to the remote station for the processing. The system in this uses zigbee communication to meet the low power consumption requirements of the development scenario. And in [11] the parameter under investigation include temperature, phosphate, dissolved oxygen, conductivity, pH, turbidity, and water level in the smartCoast R&D project, co-founded by the Irish Marine Institute and EDA. In an application of WSN the avalanche conditions can be identified in the respective areas before the actual loss by this natural calamity [12]. In this system the sensor is made up of the two or more elementary radiators. The radiators belonging to the sensor are immersed in the snow one after another. As the snow melts the water level in the snow increases which increase the conductivity of the medium. And after performing the required calculations the threshold value for the danger alerts can be calculated. WSN are also used to know the oilfields on the sea floor or the seismic movement monitoring [13]. Effective energy efficient node replacement and routing algorithms has been discussed. The nodes are autonomous and use wireless acoustic transmission for data transmission. A system to monitor the temperature in cold chain logistics in transportation has been made [14]. It prevents the perishing of the food. The system used integration of the wireless microcontroller JENNIC 5418 based on IEEE 802.15.4 standard with a thermocouple sensing converter MAX31855. They used the wireless access points integrated with the GPS and the 3G communication system. In the medical fields, WSN provides the diagnostic minority systems those do not involve puncturing the skin or entering a body cavity. In the current research it is desired to integrate more biosensors, electronics and wireless technologies into low power sensing devices that can be worn or directly planted into the patients. Other wireless applications in the hospitals are to localize the assets and streamlining hospital staff by integrating personal digital assistant (PDA) or smart phone of doctors to the larger hospital network. Smart surgical tools provide wireless sensing and tracking for computer assisted surgery and seamless use inter operatively [15]. IV.
CONCLUSION
There are number of technologies of wired and wireless sensor networks. These technologies are using the different
protocols and provide the different values for the performance parameters. Zigbee technology provides considerable data rate along with the low power consumption. EnOcean uses special messages instead of CSMA protocol to reduce the energy consumption. X10 and Insteon technologies can work on the electrical power lines which make them suitable for home automation. Wifi is high power consuming and high data rate delivering technology. Its high power consumption makes it inapplicable for wireless sensor node. Bluetooth is also a high power consumption technology which provides high data rate for shorter ranges. The main constraint of wireless sensor networks is to operate on the lowest possible level of the energy. This is because that the wireless nodes are deployed in the field which are rarely visited or attended and more over their battery replacement is costly. Wireless sensor networks are used in the versatile applications. These are being used in agriculture, home automations, environmental condition monitoring, defense areas, and medical field. V. [1]
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