Co-channel Interference Modelling Between RATs in Heterogeneous Wireless Networks

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

ICC 2012- Wireless Network Symposium - June 14th, 2012 2

Introduction Motivation Background Experiment Setup & Methodology Performance Evaluation Discussion Conclusions & Future Work


Motivation Modern devices have

many options for connectivity (radio access technologies) or RATs


Motivation How can we

seamlessly switch between RATs or enable multiple RATs simultaneously?


Motivation: Problems? Interaction between

RATs is not well studied

Simulation tools often ignore interference between Wi-Fi and Bluetooth for example


Motivation: Problems? Interaction between

RATs is not well studied

Certain algorithms assume homogeneous link capacities


Motivation: Problems?

Source: Wikipedia

Source: Cisco


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


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)?


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?


Background Will performance degrade with a larger

channel interfering with a smaller channel? (Wi-Fi to Bluetooth interference)


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


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


Background: Simulation Interference Models


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?


Experiment Setup An equal number of

Bluetooth and Wi-Fi devices

Located within a lab at the University of Guelph


Laptop Node


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


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


Performance Evaluation


Performance Evaluation


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


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


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


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


Thank you for Attending!

Questions?Jason Ernst, University of Guelph

[email protected]

mailto:[email protected]

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Co-channel Interference Modelling Between RATs in Heterogeneous Wireless Networks