1. PERFORMANCE MEASUREMENTS OF WIRELESS SENSOR NETWORKS Gizem ERDOĞAN

2. WIRELESS SENSOR NETWORKS Wireless Battery powered Ad-hoc Sense & monitor : temperature, humidity, light intensity, voltage, current, volume, acceleration, sound, pressure,etc. Various application fields: military, health care, traffic control, scientific monitoring Important aspects: Energy efficiency, self configuration

3. S TUDIES OF ANASTASI ET AL. Berkeley family motes (a) mica2 (b) mica2dot 4-Mhz, 8-bit Atmel microprocessor 512 KB of non-volatile flash memory 32-KHz clock RFM ChipCon Radio bit rate of 19.2 Kbps CSMA/CA TinyOS

4. E XPERIMENTAL ENVIRONMENT Different traffic conditions Outdoor environment Temperature Humidity Fog Rain 10 replicas in different times Average values as well as upper &lower bounds Virtual ground Limits reflection and bad electromagnetic wave’s perturbation

5. P ARAMETERS VALUES

6. DEFINITIONS Transmission Range ( TX_range ): the range within which a transmitted frame can be successfully received the transmission power the radio propagation properties Carrier Sensing Range ( CS_range ) :the range within which the other sensor nodes can detect a transmission sensitivity of the receiver the radio propagation properties

7. EXPERIMENTAL RESULTS AVAILABLE BANDWIDTH Maximum size message 56 bytes 18-byte preamble 2-byte synchronization + 36 bytes data Theoretical throughput

8. EXPERIMENTAL RESULTS AVAILABLE BANDWIDTH CONT. m : the amount of data to be transmitted. For maximum size frame 36 bytes Tframe : time required to transmit a MAC data frame at 19.2 Kbps. 56*8 /19.2 * 10 -3 = 23.33 ms; ( B min + IB max)/2 : the average backoff time ( 15 +68.3)/2=41.65 ms Expected throughput : 4.43 Kbps Estimated throughput: 4.4 Kbps

9. EXPERIMENTAL RESULTS POWER CONSUMPTION

10. EXPERIMENTAL RESULTS POWER CONSUMPTION CONT.

11. Real World Application Mica2 motes Sample the light in every 1 second Transmit 8 byte message to another node When no messages to be sent, the radio turns off and the motes power down. Leaked current while sampling is 20mA Leaked current while transmitting 18mA. Leaked current when powered down 10uA. Average current leaked in a cycle 0.19 mA, Average power consumption 0.19*3=0.57mW Lifetime of the network: more than a year!

12. EXPERIMENTAL RESULTS TRANSMISSION RANGE Two sensor nodes with the antennas in a back to back disposition Sequence numbers in each packet transmitted Vary the distance between the nodes, keep the track of the number of lost packets Assume threshold as the distance at which the percentage of received packets are below 85% Transmission range is approximately 55 m for mica2 and 135 m for mica2dot.

13. EXPERIMENTAL RESULTS TRANSMISSION RANGE CONT.

14. Factors that may affect the transmission range Transmission power Orientation of the antenna Data rate Sensor nodes location with respect to the ground Environmental conditions Transmission power: more than linear increase this increase for both kinds of motes. At the maximum transmission power 5dBm transmission range: 70 m for mica2 Transmission range: 230 m for mica2dot

15. EXPERIMENTAL RESULTS TRANSMISSION RANGE CONT. Influence of the antenna Change the relative antennas’ disposition to see the effect of the communication quality in terms of received packets mica2 antennas are very directional mica2dot nodes are resistant

16. EXPERIMENTAL RESULTS TRANSMISSION RANGE CONT. Influence of the data rate Inversely proportional in IEEE 802.11 wireless networks Does not have a significant influence on in mica2 and mica2dot Different scale of data rates Motes: Kbps whereas IEEE802.11 stations: Mbps.

17. EXPERIMENTAL RESULTS TRANSMISSION RANGE CONT.

18. Effect of sensor node’s height When the nodes are close to the ground under 1 meter, significant power loss. This loss is due to the interference between the ground.

19. EXPERIMENTAL RESULTS TRANSMISSION RANGE CONT. Influence of environmental conditions Slight variations of temperature or humidity do not have any significant influence In the presence of fog or rain, we saw that transmission range decreased significantly Due to signal attenuation caused by the interference of fog and rain particles with the electromagnetic waves

20. EXPERIMENTAL RESULTS CARRIER SENSING RANGE Fixed distance between the nodes in a couple Vary the distance between the two couples Until no correlation is measured between the couples Until Throughput achieved =4.4 Kbps

21. EXPERIMENTAL RESULTS CARRIER SENSING RANGE 275 m :end of the carrier sensing range Minor interference 450 m: interference becomes negligible

22. MAC PROTOCOLS S-MAC Reduce energy consumption caused by idle listening Schedule coordinated transmission and listen periods Overhead due to coordination and schedule maintenance. B-MAC Wake up for a very small time and sleep for a longer time. Poll the channel, if nothing interesting, go back to sleep Long preamble guaranteed to intersect with polling SCP-MAC Ultra-low duty cycle Synchronizing the polling times

23. DATA DISSEMINATION PUSH BASED STRATEGY Nodes detecting the interesting event broadcast the relevant information Efficient when there is constant need of information Broadcast bandwidth is wasted when the demand for the information is low PULL BASED STRATEGY Querier broadcasts a query for the information when it is needed. Nodes that have the relevant information send the information back. Communication takes place only when it is needed.

24. DATA DISSEMINATION CONT. COMB-NEEDLE STRATEGY Integrates both push and pull based techniques Each sensor node pushes its data through some number of The querier pulls the data in a certain neighborhood In most cases it is more efficient than both pure push and pure pull strategies.

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