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RSSI and LQI vs. Distance Measurement

RSSI and LQI vs. Distance Measurement. ReMotes. Spring 2011 José Antonio Esparza Torben Grøn Helligsø Peter Høgh Mikkelsen Michael Alrøe. RSSI Definition. Received Signal Strength Indicator (RSSI) is a measurement of the power present in a received radio signal. CC2420 Datasheet :

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RSSI and LQI vs. Distance Measurement

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  1. RSSI and LQI vs. Distance Measurement ReMotes Spring 2011José Antonio Esparza Torben Grøn Helligsø Peter Høgh Mikkelsen Michael Alrøe

  2. RSSI Definition • Received Signal Strength Indicator (RSSI) is a measurement of the power present in a received radio signal. CC2420 Datasheet: “The RSSI register value RSSI.RSSI_VAL can be referred to the power P at the RF pins by using the following equations: P = RSSI_VAL + RSSI_OFFSET [dBm] where the RSSI_OFFSET is found empirically during system development from the front end gain. RSSI_OFFSET is approximately –45.”

  3. LQI Definition • The link quality indication (LQI) measurement is a characterization of the quality of a received packet. CC2420 Datasheet: ”A correlation value of ~110 indicates a maximum quality frame while a value of ~50 is typically the lowest quality frames detectable by CC2420”

  4. RSSI and LQI from CC2420

  5. Path Loss Model:Mathematical Formula Model: PL = PTx - PRx = -10 n Log(d) + A [dBm] Where: • PL is the path loss • n is the path loss exponent, 2 = free space! • dis the distance between the transmitter and the receiver • A is a constant which accounts for system losses

  6. RSSI vs. DistanceField test: Outdoor [dBm] [m]

  7. LQI vs. DistanceField test: Outdoor [LQI] [m]

  8. RSSI vs. DistanceField test: Indoor [dBm] [m]

  9. Path Loss Model:Models Achieved Outdoor Model: PL(d) = -10 · 2.3 · Log(d) – 48 Indoor (Hall) Model: PL(d) = -10 · 2.0 · Log(d) – 45 Values determined empirically from field tests!

  10. RSSI vs. DistancePositioning

  11. Positioning: Outdoor M16 M17 M41

  12. Positioning: Results Average: • 3,4 m Min: • 0,9 m Max: • 9,9 m Error,[m] Location [#]

  13. Improvements More advanced modeling: • Wall Attenuation Factor model: nW is number of walls, C is maximum number of walls, WAF is the Wall Attenuation Factor • Fingerprinting • Correlation between RSSI and LQI!

  14. Thanks to 

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