802.11 Signal Emitter Identification

2007

Joel Kenny

A Double Edged Sword

• Security Enhancement– Transparent Identification– Difficult to Circumvent

• Implications for Privacy– Less of it

The ConstellationQuadrature

In-Phase

Phase Error

Fig. 2: Change in Magnitude

Fig. 3: Change in Phase

Magnitude Error

Signal Emitter Identification

• Define Features of Transmissions

• Measure Captured Transmissions

• Use a Database to Profile Transmitters

IQ O

ffset

Phase Error

Fig. 4: IQ Offset vs. Phase Error

GNU Radio PlatformComputer Running GNU Radio

USRP

usrp_src Blocks

USB

MoreBlocks

usrp_sink

SignalSink

SignalSource

Fig. 5: Photograph of the Universal Software Radio Peripheral

802.11 Signal CaptureComputer Running GNU Radio

USRP

usrp_src DemodulationChain

USB

802.11Packets

BasebandSignal

Timestamp

Fig. 5: Photograph of the Universal Software Radio Peripheral

Best Metrics

• Phase Error

• Magnitude Error

• IQ Offset

• Frequency Error

Results / Work In Progress

• Preliminary Success with GNU Radio

Future Research

• Development of New Metrics

• Multiple USRPs

• Research on Channel Characteristics