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PERFORMANCE MEASUREMENTS OF WIRELESS SENSOR NETWORKS. Gizem ERDOĞAN. WIRELESS SENSOR NETWORKS. Wireless Battery powered Ad-hoc Sense & monitor : temperature, humidity, light intensity, voltage, current, volume, acceleration, sound, pressure ,etc. - PowerPoint PPT Presentation
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PERFORMANCE MEASUREMENTS OF WIRELESS SENSOR NETWORKS
Gizem ERDOĞAN
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
STUDIES 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
EXPERIMENTAL 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
PARAMETERS VALUES
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
EXPERIMENTAL RESULTSAVAILABLE BANDWIDTH
Maximum size message 56 bytes 18-byte preamble 2-byte synchronization + 36 bytes data
Theoretical throughput
EXPERIMENTAL RESULTSAVAILABLE 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; (Bmin + IBmax)/2 : the average backoff time
( 15 +68.3)/2=41.65 ms Expected throughput : 4.43 Kbps Estimated throughput: 4.4 Kbps
EXPERIMENTAL RESULTSPOWER CONSUMPTION
EXPERIMENTAL RESULTSPOWER CONSUMPTION CONT.
EXPERIMENTAL RESULTSPOWER CONSUMPTION CONT. 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!
EXPERIMENTAL RESULTSTRANSMISSION 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.
EXPERIMENTAL RESULTSTRANSMISSION RANGE CONT.
EXPERIMENTAL RESULTSTRANSMISSION RANGE CONT. 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
EXPERIMENTAL RESULTSTRANSMISSION 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
EXPERIMENTAL RESULTSTRANSMISSION 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.
EXPERIMENTAL RESULTSTRANSMISSION RANGE CONT.
EXPERIMENTAL RESULTSTRANSMISSION RANGE CONT. 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.
EXPERIMENTAL RESULTSTRANSMISSION 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
EXPERIMENTAL RESULTSCARRIER 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
EXPERIMENTAL RESULTSCARRIER SENSING RANGE 275 m :end of the carrier sensing range
Minor interference 450 m: interference becomes negligible
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
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.
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.
ANY QUESTIONS?
THANK YOU!