RSS Step Size: 1 dB is not Enough!
Anh Luong1, Alemayehu Solomon Abrar1,Thomas Schmid1, Neal Patwari1,2
1University of Utah, 2Xandem Technology
HotWireless’16
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 1 / 20
Applications of RF Sensing
Q. Pu et al. “Whole-home gesturerecognition using wireless signals”,
MOBICOM 2013.
O. Kaltiokallio et al. “Non-invasiverespiration rate monitoring using a single
COTS TX-RX pair”, IPSN 2014.
W. Wang et al. “Understanding andmodeling of WiFi signal based humanactivity recognition”, MOBICOM 2015.
Future: Ubiquitous RF Sensing
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 2 / 20
Standard RF Sensors
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 3 / 20
RF Sensing Tradeoff Space
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 4 / 20
RF Sensing: sub-dB
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 5 / 20
Outline
1 sub-dB
2 Breathing Monitoring
3 Gesture Recognition
4 Conclusion
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 6 / 20
sub-dB CC1200 Prototype
Processor:
CC1200 Evaluation Board
Beaglebone Black (BBB)
Datasheet:
12 bits / 0.0625 dB
Empirical study:4 least significant bits / 1dBIQ Sample
17 bits Magnitude
Programable Real-time processingUnit (PRU)348 samples per sec
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 7 / 20
RSS Calculation and Verification
RSS =∑K
n=0 |Magnituden|2K − G
with K samples, G amp gain
Test with known generated signal
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 8 / 20
sub-dB Errors
Time (s)
0.2 0.4 0.6 0.8 1 1.2 1.4
Pow
er
(dB
)
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
Sub-dB
1 dB
sub-dB MME: 0.013 dB 1dB: 0.25dB
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 9 / 20
Outline
1 sub-dB
2 Breathing Monitoring
3 Gesture Recognition
4 Conclusion
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 10 / 20
Breathing Monitoring
0 5 10 15 20 25 302.22
2.24
2.26
2.28
2.30
2.32
2.34
2.36
RSS (dBm)
1e10
0 5 10 15 20 25 30Time (sec)
620
640
660
680
700
720
RIP belt
Experimental Setup:
CC1200 TX 434 MHz, sub-dB RX
Ground truth via respiratory inductance plethysmography (RIP) belt
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 11 / 20
Breathing Monitoring Algorithm
sn∑|sn|2 Filter FIFO DFT Peak f̂
0.1 0.2 0.3 0.4 0.5 0.6Frequency (Hz)
0
5000
10000
15000
PSD
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 12 / 20
Oversampling & Quantization for Breathing
For breathing monitoring, high accuracy requires:
0
1
2
3
4
5
6
7
8
9
34
8
17
4
11
6
87
58
43
.5
38
.67
29
21
.75
19
.33
14
.5
9.6
7
7.2
5
4.8
3
2.4
2
Err
or
(bp
m)
Hz
PSD RMSPSD MACB RMS
CB MA
0
1
2
3
4
5
6
7
8
9
10
1 1/2 1/4 1/8 1/16 1/32 1/64 1/128
Err
or
(bp
m)
Step Size (dB)
PSD RMSPSD MACB RMS
CB MA
Sampling rate≥29 Hz
Quantization step size≤1/16 dB(≥ 12 bits)
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 13 / 20
Outline
1 sub-dB
2 Breathing Monitoring
3 Gesture Recognition
4 Conclusion
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 14 / 20
Gesture Recognition
0.0 0.5 1.0 1.5 2.0Time (s)
−23.10
−23.05
−23.00
−22.95
−22.90
−22.85
−22.80
−22.75
RSS (
dB
m)
Punch
0.0 0.5 1.0 1.5 2.0Time (s)
−22.20
−22.15
−22.10
−22.05
−22.00
−21.95
−21.90
−21.85
−21.80
RSS (
dB
m)
Kick
0.0 0.5 1.0 1.5 2.0Time (s)
−23.2
−23.1
−23.0
−22.9
−22.8
−22.7
−22.6
−22.5
−22.4
RSS (
dB
m)
Zoom in & Zoom out
0.0 0.5 1.0 1.5 2.0Time (s)
−23.2−23.1−23.0−22.9−22.8−22.7−22.6−22.5−22.4−22.3
RSS (
dB
m)
Bowling
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 15 / 20
Gesture Recognition Evaluation
8 9 10 11 12 13 14 15 16Quantization bits
30
40
50
60
70
80
90
100
Accuracy (%
)
Two gesturesThree gesturesFour gestures
Features:
Variance
Skewness
8 percentiles (5th to 95th)
PSD for 3 different bands
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 16 / 20
Outline
1 sub-dB
2 Breathing Monitoring
3 Gesture Recognition
4 Conclusion
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 17 / 20
Recommendations
Chip Designer:I smaller step size
(1/16 dB or 0.0625dB)
Application Designer:I Pick IC with 12 bits RSSII IQ Sample
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 18 / 20
Conclusion
Ubiquitous RF Sensing
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 19 / 20
Thank you
This material is based upon work supported bythe U.S. National Science Foundation
under Grant Nos. #1329755 and #1407949.
Visit span.ece.utah.edu for more information
Breathing Monitoring Code is available at:https://github.com/SPAN-UofU/rub
PRU Code is available at:https://bitbucket.org/anh_luong/pru
A. Luong, A. Abrar, T. Schmid, N. Patwari RSS Step Size: 1 dB is not Enough! October 3rd, 2016 20 / 20
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