presented at icc 2012 – wireless network symposium – june 14 th 2012
TRANSCRIPT
Co-channel Interference Modelling Between RATs in Heterogeneous
Wireless NetworksJason B. Ernst, University of Guelph
Nidal Nasser, Alfaisal UniversityJoel Rodrigues, University of Beira
Interior
Presented at ICC 2012 – Wireless Network Symposium – June 14th 2012
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Introduction
Motivation Background Experiment Setup & Methodology Performance Evaluation Discussion Conclusions & Future Work
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Motivation
Modern devices have many options for connectivity (radio access technologies) or RATs
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Motivation
How can we seamlessly switch between RATs or enable multiple RATs simultaneously?
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Motivation: Problems?
Interaction between RATs is not well studied
Simulation tools often ignore interference between Wi-Fi and Bluetooth for example
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Motivation: Problems?
Interaction between RATs is not well studied
Certain algorithms assume homogeneous link capacities
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Motivation: Problems?
Source: Wikipedia
Source: Cisco
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Motivation: Why Bother?
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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Background
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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Background
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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Background
Will performance degrade with a larger channel interfering with a smaller channel? (Wi-Fi to Bluetooth interference)
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Background: Similar Studies
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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Background: Similar Studies
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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Background: Simulation Interference Models
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Background: Interference Avoidance Techniques
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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Experiment Setup
An equal number of Bluetooth and Wi-Fi devices
Located within a lab at the University of Guelph
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Laptop Node
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Methodology
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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Methodology
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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Performance Evaluation
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Performance Evaluation
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Discussion
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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Discussion
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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Conclusions & Future Work
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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Conclusions & Future Work
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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Thank you for Attending!
Questions?Jason Ernst, University of Guelph