http://www.emnets.org/

SoNIC:Classifying Interference in 802.15.4 Sensor NetworksIPSN’13

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Introduction• Devices access to 2.4 GHz band

• Knowing the interference source helps mitigation• e.g. BuzzBuzz protocol against Wi-Fi interference

[SenSys’10]

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Introduction• Existing approaches for interference

detection • Active sampling• Channel hopping• Additional hardware

• SoNIC:• use a supervised learning approach to create a

classifier that classifies corrupted packets

• light weight,energy efficiency

ApplicationMitigation Strategy

Incomming packet InterfernceStateSoNICClassifier

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Characterizing Interference• Experiment Setup:

• Sources of Interference• Wifi, Microwave ovens, Bluetooth,Non-interfered weak links

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Wifi(54M)

LQI threshold

2dBm

Bluetooth

Microwave Weak Link

14dBm11dBm

10dBm

LQI>90

Range(RSSI)>2B

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Error burstsWifi(54M) Bluetooth

Microwave Weak Link

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Error bursts• Definition:

• a sequence of corrupted symbols that may contain subsequences of at most four consecutive correct symbols.

• Temporal behavior of different interferers

mean number of symbols between error bursts in a packetthe number of symbols between the first

burst’s start and the last burst’s end

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RSSI-based featuresWifi(54M) Bluetooth

Microwave Weak LinkMean normalized RSSI

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Features of Corrupted Packets

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Overview of SoNIC

Radio Driver

Storage Matching

Feature calculation

Classifier Voter

Incoming packet

Application

Mitigation strategies

crc fail crc ok

On match

Interferencestate

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Overview of SoNIC

Radio Driver

Storage Matching

Feature calculation

Classifier Voter

Incoming packet

Application

Mitigation strategies

crc fail crc ok

On match

Interferencestate

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Classifying Corrupted Packets

Radio Driver

Storage Matching

Feature calculation

Classifier Voter

Incoming packet

Application

Mitigation strategies

crc fail crc ok

On match

Interferencestate

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Classifying Corrupted Packets• Decision Tree Classifier

• Low computational complexity• Accuracy of decision tree

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Votingtimewifi bluetooth mircowave weaklink

30sClassifier rx a corrupted packet

wifi 0.2bluetooth 0.1mircrowave 0.6Weaklink 0.2

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Votingtimewifi bluetooth mircowave weaklink

30srx a corrupted packet

the dominant interferer causes a significant amount of packet corruption

wifi 0.2bluetooth 0.1mircrowave 0.6Weaklink 0.2

Classifier

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Evaluation• SoNIC implementation

• Based on Contiki• Environment

• An office corridor of 32m long• With some uncontrolled interferer

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Classifying ResultsWeak Link Wifi Microwave Bluetooth

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Classifying ResultsWeak Link Wifi Microwave Bluetooth

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Classifying ResultsWeak Link Wifi Microwave Bluetooth

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Classifying ResultsWeak Link Wifi Microwave Bluetooth

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Classifying ResultsWeak Link Wifi Microwave Bluetooth

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Detection Results

We conclude that when experiencing packet error ratiosof 20% and more, SoNIC correctly detects the interferencestate 87.5% of the time on average

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Conclusion• Key Contribution

• SoNIC Attribute corrupted packets to an interference type

• SoNIC correctly detects the predominant interferer

• Future work• Deal with packets form different interferers are

transmitted simultaneously

http://www.emnets.org/

Q&AThanks!

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Using and Extending SoNIC

Radio Driver

Storage Matching

Feature calculation

Classifier Voter

Incoming packet

Application

Mitigation strategies

crc fail crc ok

On match

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AUGMENTING A MOBILE SINK WITHSONIC

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AUGMENTING A MOBILE SINK WITHSONIC

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Features of Corrupted Packets

Mean normalized RSSI

Automatic Gain Control

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Evaluationmean feature calculation time of 26.5 ms