Tackling)Self)Interference,)Cross 4Technology ...mobashir/Resources/Poster/2015sensysdc.pdf ·...
Transcript of Tackling)Self)Interference,)Cross 4Technology ...mobashir/Resources/Poster/2015sensysdc.pdf ·...
Tackling Self Interference, Cross-Technology Interference and Channel Fading in WSN
Mohammad MobashirSchool of Computing, National University of Singapore
Scalable Data Dissemination
Motivation
This leads to severe interference of the following two kinds
Self InterferenceSame technology devices transmitting synchronously
Cross-‐Technology InterferenceDifferent Technologies sharing the 2.4GHz ISM band
With a push towards “IoTification”, the world foresees a sharp rise in the number of devices having wireless
networking capabilities
2.4 GHz ISM Band
Synchronous TransmissionMultiple transmitters to send same data concurrently to multiple receivers.Eliminates channel contention. Allows fast data dissemination.• Glossy, LWB, Splash, Chaos, P3, etc.
Scalability ProblemReliability drops for large number of concurrent transmitters.• Difficult to maintain precise synchronization (<0.5μs)• Due to combination of software, hardware and signal propagation delays.
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Indriya Twist Indoor Outdoor
ApproachExploit Capture Effect over Multi-‐Channels• Receiver can decode a packet in the presence of interfering signals if the
signal from the sender is sufficiently stronger than that from the interferers
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6 (dBm)
IndoorOutdoor
IndriyaTwist
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-84.09
-83.02
-80.93
-70.89
-70.50
-70.04
-56.97-52.47
Requires much less stringent timing requirement (<160 μs) than that of synchronous transmission (<0.5 μs)
Design
Root
S4S1 S2 S3
R1 R2 R3 R4 R5
Nodes S1 S2 S3 S4
R1 G B W W
R2 G B W W
R3 W G B W
R4 W B B G
R5 W W W G
1
Nodes S1 S2 S3 S4
S1 0 1 0 0
S2 1 0 1 1
S3 0 1 0 1
S4 0 1 1 0
1
S2S1
S3S4
Root
S4S1 S2 S3
R1 R2 R3 R4 R5
Conflict GraphLink Classification MatrixTopology Construction Channel Assignment
Graph ColoringG: Si Good for Rj
B: Si Bad for Rj
W: Si Weak for Rj
Channel 1Channel 2Channel 3
Evaluation
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Glossy:Ch26 Glossy:Ch22 Glossy:Ch19 Glossy:Ch20 Glossy:Ch14 Glossy:Ch15 Syncast
Rel
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lity
%
Day 1 - Day 5 Variations
Day1 Day2 Day3 Day4 Day5
Robust Data Collection in Dynamic Urban EnvironmentCross-‐Technology Interference2.4GHz ISM band is shared by a number of Wireless Technologies
WiFi ZigBee Bluetooth
Availability of ZigBee Channels
Expectation
For Robust Data Collection in Urban Environment• No CTI-‐Free channel is be expected• Channel Estimation in such environment is expensive• Exploit Spatial and Channel Diversity to provide enough communication
opportunities so that channel estimation becomes redundant
Approach
The Internet Of Things
Phone Microwave
AcknowledgementThis work is supported in part by the Agency for Science, Technology andResearch (A*STAR), Singapore, under SERC Grant 1224104049.
Source: Cisco IBSG projections, UN Economic & Social Affairs
11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
1 6 112 1412 133 4 5 7 8 9 10
i
802.15.4 ith Channel 802.11 b/g ith Channel802.15.4 Channels
orthogonal to 1-6-11 802.11 b/g Channels
1 6 11
2 7 12
3 8 13
4 9 14
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2.4 GHz ISM Band
2.400 GHz 2.490 GHz
Ove
rlapp
ing
of W
iFi
and
ZigB
ee C
hann
els
Poss
ible
WiF
iCh
anne
l Ass
ignm
ents
i
Reality in Urban Environments
Presence of CTI significantly reducesthe number of “good” communicationopportunities or communication links