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!