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ISSN: 2278 – 909X International Journal of Advanced Research in Electronics and Communication Engineering (IJARECE) Volume 2, Issue 1, January 2013 45 A ll Rights Reserved © 2012 IJAREC E Current Wireless Sensor Nodes (Motes): Performance metrics and Constraints Mridula Maurya , Shri R. N. Shukla Abstract - Wireless sensor networks are a budding technology with the potential to change the way that we live. Motes form the building blocks of wireless sensor networks; in this paper we present the performance metrics of current existing wireless sensor nodes and constrain ts. We investigate several aspects concerning towards performance which includes important metrics - size and cost with others as power usages, data rate, radio outdoor range, memory management, receive sensitivity and we also focus on several supplementary hardware (Transceiver) , networking protocol and supporting OS in configuring motes. We are also highlighting the several technical challenges in terms of extremely low cost, low energy requirements and limited communication capabilities, while dealing with various workloads and diverse constraints. Result of the paper tells that the TinyNODE mote is the best option available for many applications. IRIS is too better option for some applications having limited sources. Sun SPOT is exceptionally good where me mory is the prime factor. Index Terms - Constraints, Motes, Performance metrics, TinyOS I. I NTRODUCTION Recently, wireless sensor network (WSN) has become a promising technology with a wide range of applications such as supply chain monitoring and environment surveillance. It is typically composed of multiple tiny devices equipped with limited sensing, compu ting and wireless communication capabilities. These tiny devices are called „motes” or wireless sensor nodes. Motes are the small, low power single board computer with a radio for wireless communication and form the building block of wireless sensor netwo rk .A single mote has mainly three key ingredients - a microcontroller, sensors and low power radios. There may be more than one sensor present in a mode depend on the applications, like sensors for temperature measurement, light, pressure, humidity etc. Mo tes can either run on batteries or they can tap into the power grid in certain applications. Motes collect and transfer data using four stages: collecting the data, processing the data, packaging the data and communicating the data. Each mote collects data using its various types of sensors. After collecting the data, the mote processes the data using its electronic brain. Once the data has been processed, the brain packages the data into an easily handled form. This process is known as enveloping [1] . O nce the data has been collected and processed to this point, the mote then begins to interact with other motes. In this paper we present the current wireless motes, their performance metrics and constraints. We investigate several Manuscript received Jan 01, 2013. Mridula Maurya , Electronics and Communication Deptt., M.M.M. Engg. College, Gorakhpur, Uttar Pradesh - 273010, India, +919889506130, Shri R. N. Shukla , Professor , Electronics and Communication Deptt. M.M.M. Engg. College, Gorakhpur, Uttar Pradesh - 273010, India, +919235500557, aspects concerning towards performance which includes important metrics - size and cost with othe rs as power usages, data rate, radio outdoor range, memory management, receive sensitivity and we also focus on several supplementary hardware(Transceiver), networking protocol and supporting OS in configuring motes. We are also highlighting the several te chnical challenges in terms of extremely low cost, low energy requirements and limited communication capabilities, while dealing with various workloads and diverse constraints. This paper is organised as follows: - Section II lists the current wireless sen sor nodes performance metrics comparison and also individual mote platforms and protocols used in configuring motes. Section III presents the limitation under diverse constraints of cost, energy requirement and capabilities. Finally, Section IV summarizes the findings of better mote having best specifications in the conclusion section. II. S COPE OF STUDY - PERFORMANCE METRICS We have divided the performance metrics into 5 different categories: - P hysical characteristics, CPU, Speed and Memory management , Transmit pow er level, Radio Range, S ensitivity , Po wer u sages, and Supplementary Hardware and Softwares [2]. In this paper, we will be limiting ourselves to 8 of the currently commercially available mote platforms in nearly 2012. Metrics of following motes is to be presented likewise: MicaZ : - These are the Generic Sensor Node, were developed at UC Berkeley and are the platforms that first coined the term “motes”. It comes in 2 nd and 3 rd generation family of Crossbow Technology [3 ] . TelosB/Tmote Sky: - The TelosB mote platform is an open source, low - power wireless sensor module designed to enable cutting - edge experimentation for the research community. The Telos nodes were first from the UC Berkeley and now available in same speciation from both Sentilla and Crossbow technology. IRIS : - The IRIS mote used for enabling low - power wireless sensor networks. IRIS provides users a wide variety of custom sensing applications providing up to three times improved radio range and twice the program memory over previous generations of MICA Motes. SHIMMER : - Full form is - Sensing Health with Intelligence, Modularity, Mobilit y, and Experimental Reusability (SHIMMER). Shimmer is a small wireless sensor platform that can record and transmit physiological and kinematic data in r eal - time. Designed as a wearable sensor, Shimmer incorporates wireless ECG, EMG, GSR, Accelerometer, Gyro, Mag, GPS, Tilt and Vibration sensors. TinyNode: - A comprehensive platform for wireless sensor network applications, supporting both research and industrial deployments. It comes with a rich, ISSN: 2278 – 909X International Journal of Advanced Research in Electronics and Communication Engineering (IJARECE) Volume 2, Issue 1, January 2013 46 A ll Rights Reserved © 2012 IJAREC E Table - I: Size, Weight and Cost (year 2012) practical set of hardware extensions and full TinyOS [4 ] support o ffering a wide set of connectivity , storage , energy, and interfacing options. Sun SPOT : - Full form is Sun Small Programmable Object Technology and developed by Sun Microsystems . The device is built upon the IEEE 802.15.4 [5 ] standard. Cricket: - The Cricket Mote, is a location aware version of the popular MICA2 low - power Processor/Radio module. The Cricket Mote includes all of the standard MICA2 hardware and an ultrasound transmitter and receiver. This device uses the combination of RF and ultrasound technologies to establish differential time of arrival and hence linear range estimates. LOTUS: - LOTUS is an advanced wireless node platform developed around the low power ARM7 Cortex M3 CPU and incorporates the best of IRIS, TelosB and Imote2 onto a single board. LOTUS is backward compatible with MEMSIC’s MDA and MTS range of Sensor Data Acquisition Boards and it is factory configured to run RTOS [6](Real Time Operating System). II (a) P hysical C haracteristics ( size and cost ) In this section motes performance metrics are contrasted based on specifications/characteristics and supports such as size, cost, hardware and software capabilities & outputs. Table - I provides mote selection parameter i.e. physical properties li ke size, cost & weight. It tells the comparative list of current sensor node’s size & cost as decisive factor when choosing a certain WSN in integrated applications [7]. IRIS & TinyNODE size is comparatively small & of less cost. So being cost and size fin al factor for selection these are best available options. II (b) C PU, S peed and M emory M anagement Table – II dictates the mote’s on board specifications - name of microcontroller [16] and its memory, frequency range and data rates. There is a wide variation in available Program and data memory, also have availability of external flash memory for saving more data of their different application spaces accordingly. Another exception to the data rate is TinyNODE having less data rate of 153.2 kbps. High 4MB exte rnal memory and 512kbps of Sun SPOT is exceptionally better than others in terms of memory. II (c) Transmit power level and sensitivity Table - III provides information about those performances metrics which are distinctly depends on different applications. As we can see that IRIS has higher TX power and upto 3 times improved radio range than mica node and others. If we ignore the data rate then TinyNODE can be efficiently selected against IRIS because of its higher TX power at certain applicati ons. II (d) Power Usages Out of 8 motes enlisted in Table - IV 6 mote platform boards are powered from an external battery pack containing 2 AA batteries, while rest 2, the SHIMMER and the Sun SPOT use Li - ion “ 3.7 V ” rechargeable battery pack “ 250mAh ” and “ 750mAh ” respectively. High configuration of battery of Sun SPOT mote is because of its more processor and power - intensive feature. Operating voltage range of all motes is in between “ 2.1 - 3.6 VDC ” [17]. TinyNODE is better comprehensive platform having simi lar communication abilities and consuming less amount of energy. MicaZ, TelosB and Sun SPOT are also comparatively more power efficient than others. Table - II: CPU, Memory, Operating Frequency and Data rate Sr. No . Name of Motes Microcontroller Prog ram +Data Memory External Memory Frequency Range Data R a t e (kbps) Remarks 1 2 3 4 5 6 7 8 MicaZ TelosB IRIS SHIMMER TinyNode Sun SPOT Cricket LOTUS ATMEGA128 TI MSP430 ATMEGA128 TI MSP430F1611 TI MSP430 ARM920T ATMEL128L NXPLPC1758 4K RAM 10K RAM 8K RAM 10K RAM 8K RAM 512K RAM 128K+4K+4K 64K SRAM 128K 48K 128K 48K 512K 4MB 512K 512K 2.4 GHZ 2.4 - 2.4835 GHZ 2.4 GHZ 2.4 - 2.4835 GHZ 868 - 870 MHZ 2.4 - 2.4835 GHZ 433 MHZ 2405 - 2480MHZ 250 250 250 250 152.3 250 250 250 Sun SPOT has exceptional ly higher program and external memory. Sr. No. Name of Motes Size in (mm) Weight (g) Cost per node Remarks 1 2 3 4 5 6 7 8 MicaZ [8] TelosB [9] IRIS [10] SHIMMER [11] TinyNode [12] Sun SPOT [13] Cricket [14] LOTUS [15] 58*32*7 65*31*6 24.23*24.23*7.5 44.5*20*13 30*40 41*23*70 ~58*32*7 76*34*7 18 23 3 10 -- 54 ~18 18 US$99 US$99 US$115 US$262 US$180 US$750 US$225 US$300 As we can see that size and cost of IRIS and TinyNODE is comparatively less than others. Cost of TinyNODE is higher than mote no. 1, 2 & 3, but considering size it may be better option, because size also affects the manufacturing cost. ISSN: 2278 – 909X International Journal of Advanced Research in Electronics and Communication Engineering (IJARECE) Volume 2, Issue 1, January 2013 47 A ll Rights Reserved © 2012 IJAREC E Table - III: TX power, Radio Range and Sensitivity Sr. No . Name of Motes Transmitter Power Max. Outdoor range Receive Sensitivity Remarks 1 2 3 4 5 6 7 8 MicaZ TelosB IRIS SHIMMER TinyNode Sun SPOT Cricket LOTUS - ( 24 ) dBm - 0dBm - (24) dBm - 0dBm 3 dBm (typ . 1 ) - (24) dBm - 0dBm u pto +12dBm - (24) dBm - 0dBm 3 dBm (typ . ) 3 dBm (typ .) 75 - 100 m 75 - 100 m �300 m ~100 m 200mtr@76.8 kbps ~100 m 30 m indoor 100 m - 90 dBm(min), - 94dBm - 90 dBm(min), - 94dBm - 101 dB m (typ . ) - 94 dBm ~106dBm@76.8 kbps ~90dBm - 101 dBm (typ . ) - 101 dBm (typ .) IRIS has higher TX power and upto 3 times improved radio range than mica node and others. typ. 1 = t ypical II (e) Supplementary Hardware and Softwares In the T able - V, majority of the motes use 802.15.4 compatible CC2420 [17] radio chip from Texas Instruments. IRIS mote also employ the 805.15.4 compatible chip from Atmel family. Another exception to the CC2420, the TinyNODE uses SEMTECHCHSX1211 [18]. Table - V also tells t hat most of the motes listed here are programmed via the TinyOS operating system unlike Sun SPOT which directly run on the processor without an OS using small java program. Mainly RF Transceiver configuration is CC2420 2.4 GHz IEEE 802.15.4 / ZigBee [19]. III. H URDLES IN WIRELESS M OTE’S RACE Due to advancement in MEMS technology [21], wireless communications and digital electronics we have been able to make variety of low - cost, low - power and less size sensor motes. But still we are subjected to a variety of u nique challenges and constraints. These constraints impact the design of a WSN, leading to protocols and algorithms that differ from their counterparts in other distributed systems. These are exactly similar to hurdles in race that we have to cross efficie ntly. In this section we have pointed those hindrances as follows: - Energy: - Motes, being a micro - electronics device operate with limited energy budgets because they are powered through batteries, which must be either replaced or recharged (e.g., using solar power) when depleted. For some nodes, neither option is appropriate, that is, they will simply be discarded once their energy source is depleted e.g. in forests used for habitat monitoring. Therefore Mote’s Lifetime factor is strongly depends on battery lifetime. As a consequence, the first and often most important current focus ing issue are making of power aware protocols and algorithms. [22] Communication capabilities: - This factor can be divided into four domains: self management, random deployment, networking and range. It is the nature of many sensor network applications that they must operate in remote areas and harsh environments, without infrastructure support or the possibility for maintenance and repair. Therefore, sensor nodes must be self - managing in that they configure themselves, operate and collaborate with other nodes, and adapt to failures, changes in the environ without human intervention. In most of net work applications sensor nodes are deployed in random manner, they do not require predetermined and engineered locations. Hence it is up to the nodes to identify themselves in some spatial co - ordinate system. The reliance on wireless networks and communica tions poses a number of challenges to a sensor network designer. For example, attenuation limits the range of radio signals, that is, a radio frequency (RF) signals fades (i.e., decreases in power) while it propagates through a medium and while it passes t hrough obstacles. The relationship between the received power and transmitted power of an RF signal can be expressed using the Inverse - square law : P r ∝ P t/ d 2 [22] This states that the received power Pr is proportional to the inverse of the square of the distance d from the source of the signal. That is, if P x r is the power at distance x , doubling the distance to y = 2 x decreases the power at the new distance to P y r = P x r / 4. As a consequence, an increasing distance between a sensor node and a base station rapidly increases the required transmission power. Cost: - Summarizing the section dictates that any improvement in above domains ultimately constraints the Cost. Increasing of TX power, providing more energy, Table - IV: Power consumption at different transmitting power level Sr. No Name of Motes Receive Mode - 10dBm/ - 17dBm - 5dBm/ - 3dBm 0dBm/ +3dBm Idle/Sleep mode Remarks 1 2 3 4 5 6 7 8 MicaZ TelosB IRIS SHIMMER TinyNODE Sun SPOT Cricket LOTUS 16mA 19.7mA 70mA 23mA 3mA 20mA ~16 mA 16mA -- /10mA 11mA/ -- -- -- -- -- -- -- /10mA -- /13mA 14mA / -- -- -- -- -- -- -- /13mA -- /17mA 17.4mA/ -- -- -- /62mA -- -- -- /17mA 20uA/1uA 21uA/1uA -- -- -- /5.1uA 32 uA/ -- -- -- TinyNODE is better comprehensive mote platform for WSN applications having similar communication cap abilities and consuming less amount of energy. ISSN: 2278 – 909X International Journal of Advanced Research in Electronics and Communication Engineering (IJARECE) Volume 2, Issue 1, January 2013 48 A ll Rights Reserved © 2012 IJAREC E Table - V: RF Transceiver and OS comparison Sr. No . Name of Motes Transceiver Operating System ( OS ) Remarks 1 2 3 4 5 6 7 8 MicaZ TelosB IRIS SHIMMER 2 TinyNode Sun SPOT Cricket LOTUS TI Chipcon CC2420 TI CC2420 AT86RF230 SHIMMER SR7 (TI CC2420) SEMTECHCHSX1211 TI Chipcon CC 2420 TI Chipcon 868/916 MHZ TI CC2420 TINY OS,MOTE RUNNER TINY OS,SOS,MANTISOS TINY OS,MOTE RUNNER TINY OS TINY OS SQUAWK JAVA ME TINY OS RTOS,TINY OS Majority of the motes use 802.15.4 compatible CC2420 and TinyOS 2 Note: - In addition to CC2420 the SHIMMER also contains a second radio, a class 2 Bluetooth radio compatible with the Mitsumi WML - C46 series. [20 ] improving adaptability and making sensor node to perform in autonomous fashion ultimately increases cost and size and restricts certain applications. IV. C ONCLUSION This paper has presented a comparative study of performance metrics of current popular wireless sensor nodes (motes) and also current focussing issues where we need to work hard and develop sensor nodes with more capabilities at low cost, size and power. A fter studying all factors we are now in better position to select best available nodes today for our required applications and to work in catching our targets. In terms of individual observations, we have found that the TinyNODE mote is the best option if less cost, limited processing power, optimum TX power and outdoor range are taken into consideration in the application requirements. IRIS is too better option for some applications having limited sources. Sun SPOT is exceptionally good where memory is the prime factor. To run the RTOS, LOTUS is best suited because it is already factory configured to the same. REFERENCES [1] Culler, D . E., & Mulder, H. (June, 2004), “Smart Sensors to Network the World.” Scientific American, 290, 52 - 59. [2] Holger Karl and Andreas Willig,” Protocols and Architectures for Wireless Sensor Networks” by John Wiley & Sons, Ltd 2005 pp. 15 - 109. [ 3 ] Crossbow, http://bullseye.xbow.com:81/Products/productdetails.aspx?sid=156 . [4 ] TinyOS, http://www.tinyos.net/ . [5 ] IEEE, 802.15.4: Wireless Access Control (MAC) and Physical Layer Specifications for Low - Rate Wireless Pe rsonal Area Networks (LR - WPANs) IEEE, New York, 2003. [6 ] RTOS, http://en.wikipedia.org/wiki/Real - time_operating_system [7 ] Bhaskar Krishnamachari, “ Networking Wireless Sensors” by Cambridge University Press 2005, pp. 4 - 6. [8 ] - [10], [14] , and [ 15 ] M otes datasheet, [Online] Available: http://www.memsic.com/products/wireless - sensor - networks/wireless - modules.html [11 ] SHIMMER, http://www.shimmer - research.com/tag/sensor and JeongGil KO, Chenyang Lu, Mani B. Srivastava, and John A. Stankovic, “ Wireless Sensor Networks for Healthcare” IEEE paper 2010. [12 ] Henri Dubo is, Roger Meier, Laurent Fabre and Pierre Metrailler, “ TinyNode: A Comprehensive Platform for Wireless Sensor Network Applications” IPSN’06, April 19 – 21, 2006, Nashville, Tennessee, USA . [ 13 ] “ Sun™ Small Programmable Object Technology (Sun SPOT) Theory of Operation” - by Sun Microsystems and http://www.sunspotworld.com/ [16 ] M. Healy, T. Newe, and E. Lewis, “Wireless sensor node hardware: A review,” in 7th IEEE Conference on Sensors at Lecce, Italy, 2008. [17 ] TI CC2420 datasheet, [Online], Available: http://www.ti.com/lit/ds/symlink/cc2420.pdf [18 ] SEMTECH SX1211 datasheet [Online], Available: www. semtech .com/images/mediacenter/collateral/ SX1211 - PB.pdf [19 ] ZigBee, http://en.wikipedia.org/wiki/ZigBee [20 ] http://www.mitsumi.co.jp/latest/Catalog/hifreq/bluetooth/wmlc46e.html [21 ] http://www.memx.com/technology.htm and http://en.wikipedia.org/wiki/Microelectromechanical_systems [22 ] Waltenegus Dargie and Christian Poellabauer,”Fundamentals of Wireless sensor Networks” by John Wiley & Sons Ltd 2010 , pp.9 - 13. percentile . She is pursuing M.tech. (2 nd Year) in Digital Systems from the dep artment of Electronics and Communication Eng ineering , M.M.M. Engineering College Gorakhpur (U.P.) India. Her main research includes Wireless Communication and Wireless Sensor Networks. He has 10 years of industrial experience, 25 years of consultancy experience. He works as assistant professor for 16 years, as associate professor for 10 years and then as professor for 3 years in Electronics Engineering Dep artment, M.M.M. Eng ineering College, Gorakhpur. He is member of ISTE, IE (INDIA ), IETE and CISCO. He supervised 16 M.tech . dissertations. He has 24 publications on various platforms in area of Process Communication. His research interests include Process Communication, Wireless Communication & Wireless Sensor Networks. Mridula Maurya was born in Kanpur, U.P., India. She completed B. T ech . Degree in Electronics engineering from Dr. A . I.T.H. Kanpur (U.P.), India in 2010. She qualified GATE - 2011 examination with 93.30 percentile. Shri Prof. R.N. Shukla was born in 1950. He is a gold medallist for 1st Rank in B.Tech in University. He is dual M.tech . in Circuits and Systems and also in Industrial Electronics & Process Communication.