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Presented at ICC 2012 – Wireless Network Symposium – June 14th 2012
Motivation
Background
Experiment Setup & Methodology
Performance Evaluation
Discussion
Conclusions & Future Work
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Modern devices have
many options for
connectivity (radio
access technologies) or
RATs
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How can we seamlessly
switch between RATs or
enable multiple RATs
simultaneously?
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Interaction between
RATs is not well studied
Simulation tools often
ignore interference
between Wi-Fi and
Bluetooth for example
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Interaction between
RATs is not well studied
Certain algorithms
assume homogeneous
link capacities
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Source: Wikipedia
Source: Cisco
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Many reasons why the ability to seamless
switch RATs is important:
› More robust and reliable communications
Failover to other networks using different RATs
› Potentially increased battery life
Selecting the most energy efficient RAT when
possible
› Potentially improved performance
Enabling multiple RATs at once
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Previous studies show that partial
overlapping of Wi-Fi channels does not
significantly affect performance
[Mishal et al, 2006]
What about overlap between RATs(ex:
Wi-Fi, Bluetooth, Zigbee)?
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Will performance degrade with a small
channel interfering with a larger
channel? (Bluetooth interfering with Wi-Fi)
› If not, is there a threshold number of
Bluetooth interferers that causes
performance degradation?
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Will performance degrade with a larger
channel interfering with a smaller
channel? (Wi-Fi to Bluetooth interference)
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Shuaib et al [2005]
› Bluetooth Wi-Fi Internet
Wi-Fi performance somewhat dependent on
Bluetooth performance
Also only looks at Wi-Fi performance
We aim to send Bluetooth and Wi-Fi traffic
independent of each other simultaneously
We aim to investigate both Wi-Fi and Bluetooth
performance
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Carfang et al [2008]
› More focused on how mobility affects
communication in the face of interference
Guo et al [2010]
› Focused on error rates and signal strengths
while we are concerned with throughput
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In Bluetooth 1.2: Adaptive Frequency
Hopping
› Tries to sense what channel Wi-Fi is using and
avoid those frequency ranges
› What happens when Wi-Fi saturates the area as
is common now?
Other techniques where Wi-Fi and
Bluetooth chips communicate directly to
avoid
› What happens when using external Bluetooth
adaptors, chips that do not support etc?
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An equal number of
Bluetooth and Wi-Fi
devices
Located within a lab
at the University of
Guelph
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FTP file transfers between nodes
Input from /dev/random on Ubuntu 11.10
Wi-Fi file size was 10 megabytes
Bluetooth file size was 1 megabyte
Difference is because of the order of
magnitude difference in link capacity so
that a single transfer would finish roughly
at the same time
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Up to 6 laptops using each technology (6
Bluetooth and 6 Wi-Fi laptops)
Experiment performed late in the evening
when few students use the campus Wi-Fi to
decrease external interference
30 Repetitions for each data point
Throughput is averaged across all nodes
using particular technology
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Bluetooth performance particularly is
affected by Wi-Fi nodes in the region
› Fig 2: 2, 3, 4 devices all show decreased
performance due to interference
In some cases Wi-Fi nodes are also
affected by Bluetooth interference
› Fig 3: 3 devices
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Decreased performance due to
increased contention within the
technology more to blame than
interference between technologies, but
still some effect
In future experiments, it may be best to vary
the number of one type of node at a time to
isolate the cause of decreased performance
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Results show that Bluetooth is significantly
affected by Wi-Fi interference within the
same channel range
Result also showed limited cases of Wi-Fi
being affected by Bluetooth interference
Results make the case that simulation tools
should begin to support interference
modelling between technologies
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In future experiments, vary number of nodes
with a particular RAT while leaving other
constant
Expand to include other RATs, ex Zigbee
Vary the distance, introduce mobility
Develop heterogeneous access schemes
that avoid interference between RATs
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Questions?
Jason Ernst, University of Guelph
[email protected]
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