Evaluation of Software Defined Radio for Parasitic Tracking

Thesis by: Reissner Ulrich
Advisor: Manuel Huber
Director: Gudrun Klinker
Due date: 26.09.2007

Abstract

This Sep focus on meassuring IEEE 802.11(Wireless Lan) signal strength with the Universal Software Radio Peripheral(USRP) and GNU-Radio.
The 802.11 signal is converted from analog to digital with the USRP, an later demodulated with GNU-Radio. This demodulated signal is used to extract the needed data, like signal strength, type and MAC-Address.
On the other side, data received with an Intel Corporation PRO/Wireless 3945ABG controler integrated into a Laptop, is used for comparsion.
At the end, a visualisation of both signals is done with MagicMap.

Parasitic Tracking

• tracking infrastructure is not everywhere
• use all posibilities for tracking
• standard situation:
  • extra hardware
  • fixed application programming interface

• in our case:
  • use only one hardware for all kind of tracking
  • use detail information to get better results

Hardware - Universal Software Radio Peripheral(USRP)

• Altera FPGA
• USB 2.0
• up to 4 daughterboars with range form 1MHz to 3GHz

Software - GNU-Radio

• software defined radio
• turns radio hardware problems into software problems

Signal Measurement

• IEEE 802.11
  • Receive Signal Strength Indicator(RSSI) specified as optinal
  • value between 0 and RSSI_MAX
  • RSSI_MAX diffrent for each vendor

• USRP
  • calculated over a definable number of bits received
  • RSSI_MAX can be self defined

Evaluation

• Comparsion USRP - INTEL 3945ABG
  • empty room, only tables and chairs
  • 4 access points with fixed positions
  • 7 independent measurements, each 300 s long
  • USRP
    • 62699 values
    • standard deviation : 4,67
    • values per access point per second : 7,46
  • INTEL
    • 9905 values
    • standard deviation : 4,11
    • values per access point per second : 1,18

• Advantages of USRP and GNU-Radio
  • use all packets, not only beacons
  • focus only on needed channels
  • calculate the RSSI over the complete frame
  • higher packet rate
  • combination with rfid, dect, bluetooth

• Disadvanteges of USRP and GNU-Radio
  • need of extra hardware
  • more expensive than off the shelf hardware
  • lower range
  • higher power usage
  • high cpu workload
  • a bit higher standard deviation
  • only works with 1 Mbit/s at the moment

Further Work

• implement channel hopping for USRP
• improve RSSI calculation
  • use new gnuradio version
  • implement new functions
• use new USRP version, to work with more than 1Mbit/s
• expand for dect, rfid, bluetooth tracking
• implement positioning algorithm
• implement api for Ubitrack