cc2420 channel and rssi evaluation nov/22/2006 dept. of eecs, uc berkeley c o nnect vitylab i
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CC2420 Channel and RSSI Evaluation
Nov/22/2006
Dept. of EECS, UC Berkeley
COnnect vity Labi
Contents
Introduction
Chipcon CC2420 Radio
CC2420 RSSI Evaluation
The Comparison of Different Methods
Introduction
0 1 2 3 4 5 6 70
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1The CDF of Different RSS Based Indoor Positiong Methods (Note: Different Experiment Environments)
Error (m)
CD
F
MP&AP Perspective + Kalman FilterHistogram Bayseian ApproachAdaptive TemporalNovel ToF(Steven Lanzisera - UC Berkeley)Hours (Cluster&Cluster Key)Ekahau SystemParticle Filter (Median error)A System for LEASE (Median error)ECOLOCATION (Max error)
RSS values measured by COTS wireless systems are sufficiently rich in information to permit a mobile device locates itself,
reliably and accurately
The most important trade off is between Offline Calibration and accuracy
Continuing The Project
Next Steps
Last Final Conclusion
Sensors Evaluation+
Fingerprinting
Distributed Estimation(Study, Modeling,
Simulation, Implementation)
Radio Map Independent Algorithm (Study, Modeling
Simulation, Implementation)
Tx1
Rx1Rx2
Rx3
The Goal of this Part of the project
Last Final Conclusion
Become familiar with our sensors and evaluate them as much as possible
Understand the behavior of RSSI in indoor environments
Measure the effect of different parameters on RSSI
Survey the existence of correlation in RSSI Samples and base band received signals
Study the theory of indoor wireless channels (as much as it was needed)
Gathering a lot of data in different situations and environment
Analysis of these data
Performed Works
Chipcon CC2420 Radio
The Chipcon CC2420 Radio Chip Characteristics
Frequency: 2.4 GHz
Communication Technology: Direct Sequence Spread Spectrum
Data Rate: 250 kbps
Total BW: 83 MHz
Output power: Programmable (Max Power = 0 dBm)
The CC2420 is an IEEE 802.15.4 compliant RF transceiver designed for low-power and low-voltage wireless applications
The CC2420
Range (Indoor) : 30 m
Chipcon CC2420 Radio
The Chipcon CC2420 Radio Chip Characteristics
The CC2420
IF: 2 MHz
2 Sym: 4 Bits 32 Chips
Tc = 0.5 us
Pulse Shaping: Half SineEach Byte
The RSSI value is always averaged over 8 symbols periods (128 us) and digitized by an 8 bit ADC
The Chipcon CC2420 Radio Chip Characteristics
Chipcon CC2420 Radio
RSSI and LQI in The CC2420
The Link Quality Indication (LQI) measurements is a characterization of the strength and/or quality of received packet
RSSI and LQI values are not necessarily linked; but Low LQI Invalid RSSI
The Chipcon CC2420 Radio Chip Characteristics The Chipcon CC2420 Radio Chip Characteristics
The values of RSSI could really affected by other people working with motes
Although there is no direct interference with the Wi-Fi channels, the channel quality can be affected by the overload and thus distort some
of the packets
Chipcon CC2420 Radio
Telos Mote Experiment, Stockholm, 2005
The Effect of Radio Interference
Measurements with the same motes at the same location, same batteries show a difference up to a few dBm (from new motes to
old motes)
The Effect of the Motes Themselves
RMS Delay Spread
CC2420 Wireless Channel Characteristics
Delay Spread
ns30
nsnsnsmm
Td 973.310010*3
1
10*3
3088
pathshortestandlongestjittT jiji
d :,,)()(max,
MHzT
Wd
C 7.52
1
MHzMHzW BWSignal 7.52 Channel is flat fading and a single channel filter tap is sufficient to model the channel
RMS Delay Spread
5.06.65
1
9.066050
1
FCFMHz
FCFKHz
WC
F=2.4 GHz
Flat Fading
Frequency Selective
Corry Hall Corridor
Chipcon CC2420 Radio
Coherence Time
smvms
smvms
vvf
C
fT
cdCohe /3.176
/36.17
104.2
103423.423.
423.9
8
1375
137
128 sRSSI
TroundNoRSSIS
MeasTime
Cohe
The maximum number of
stable RSSI samples
In our system, there is one RSSI sample per packet
In this network configuration the RSSI rate is 26.3 sample/second per device
CC2420 Wireless Channel Characteristics
25*tan
cmtyUserVelociCohTimeceDisCoherence
Chipcon CC2420 Radio
Indoor Path Loss Model
Path Loss Model
CC2420 RSSI Evaluation
One sensor put at different distances (at the ~same time/Corridor)
Test Scenario
Run: RSSI_FigAvgVarHist.m at C:\ZigBeeNodes\CollectedData\Corridor_072106\Test1_QP
TxRx
1d
2d
Indoor Path Loss Model
Path Loss Model
One sensor put at different distances (at the ~same time/Corridor)
Test Scenario
Conclusions
- Constant offset is not -45 dBm
- Path Loss almost follows the Log-Normal Model
- The effect of multipath is remarkable
- Something is wrong in these sensors (Interference/Sensors Board)
Worth Case
n
d
dPL
04
0
CC2420 RSSI Evaluation
0 2 4 6 8 10 12 14 16 18 20-100
-80
-60
-40
-20
0
Distance (ft)
Pat
h Lo
ss (
dB)
PathLoss vs Distance in Quiet Corridor
RSSI(d) = Pt(dBm) - PL(D0) - 10nlog10(d/D0) + Noise
RSSI(d) = -17.112 - 36.3236 - 1.85*10log10(d/3(ft))
RSSI(d) = -17.112 - 57.0773 - 1.69*10log10(d/3(ft))
Theoritical PLPractical PLReal
0 2 4 6 8 10 12 14 16 18 20-100
-80
-60
-40
-20
0
Distance (ft)
Pat
h Lo
ss (
dB)
PathLoss vs Distance in the Presense of People at Corridor
RSSI(d) = Pt(dBm) - PL(D0) - 10nlog10(d/D0) + Noise
RSSI(d) = -17.112 - 34.9492 - 1.78*10log10(d/3(ft))
RSSI(d) = -17.112 - 50.016 - 1.64*10log10(d/3(ft))
Theoritical PLPractical PLReal
-17 dbm
Indoor Path Loss Model
Path Loss Model
Test Scenario
0 2 4 6 8 10 12 14 16 18 20-80
-60
-40
-20
0
20
Distance (ft)
RS
SI
Mea
n
RSSI Mean vs Distance In The Corridor
Max Err = 9.6015 & Mean Err = 3.1511
Quiet EnvPeople|Mean Err|
0 2 4 6 8 10 12 14 16 18 200
1
2
3
4
5
Distance (ft)
RS
SI
Var
RSSI SD vs Distance In The Corridor
Quiet EnvPeople
One sensor put at different distances (at the ~same time/Corridor)
CC2420 RSSI Evaluation
Indoor Path Loss Model
Path Loss Model
Test ScenarioOne sensor put at different distances (at the ~same time/Corridor)
CC2420 RSSI Evaluation
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
-80
-70
-60
-50
-40
-30
-20
Box-Whisker Plot, Env: Quiet Corridor, Black Circle: Mean Value
RS
SI
(dB
m)
Distance (ft)
200 RSSI
Indoor Path Loss Model
Path Loss Model
Test ScenarioOne sensor put at different distances (at the ~same time/Corridor)
CC2420 RSSI Evaluation
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
-80
-70
-60
-50
-40
-30
-20
Box-Whisker Plot, Env: Not Quiet Corridor, Black Circle: Mean ValueR
SS
I (d
Bm
)
Distance (ft)
200 RSSI
Indoor Path Loss Model
Path Loss Model
One sensor put at different distances (at the ~same time/Corridor)
Test Scenario
Conclusions
-Something is wrong in these sensors
- The effect of interference
Worth Case
Our Sensors
(Outdoor)
0.20
0.05
1.90
9.17
0.91
1.60
Our Sensors (Indoor)
0.02
0.20
2.17
19.20
2.40
7.68
Stanford Sensors
(Indoor & 100 Sensors )
0.0 13.77 .02822
Min Var Max Var Avg Var
dBm
Variance Test
Mica Z
CC2420 RSSI Evaluation
Outdoor Path Loss Model
Path Loss Model
Two sensors put at different distances (at the ~same time/Soccer Court)
Test Scenario
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5-100
-80
-60
-40
-20
0
Distance (ft)
RS
SI
Mea
n (d
B)
RSSI Mean vs Distance In Large Outdoor Env
Device 1Dev1-LogNrmPLDevice 2Dev2-LogNrmPL
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5-80
-60
-40
-20
0
20
Distance (ft)
RS
SI
Mea
n (d
B)
RSSI Mean vs Distance In Large Outdoor Env After Offset Compensation, Avg-PrcThrDiff ~ 2.5 dB
Device 1Dev1-LogNrmPLDevice 2Dev2-LogNrmPL
Conclusions
- Constant offset is not -45 dBm
- Path Loss almost well follows the Log-Normal Model
- In the outdoor these sensors have almost same behavior
- There is some offset between sensors, so calibration is necessary
CC2420 RSSI Evaluation
Outdoor Path Loss Model
Path Loss Model
Two sensors put at different distances (at the ~same time/Soccer Court)
Test Scenario
1 2 3 4 5 6 7
-80
-60
-40
-20
Box-Whisker Plot, Dev 1, Env: OutDoor
RS
SI
(dB
m)
Distance (ft)
1 2 3 4 5 6 7
-80
-60
-40
-20
Box-Whisker Plot, Dev 2, Env: OutDoor
RS
SI
(dB
m)
Distance (ft)
CC2420 RSSI Evaluation
400 RSSI
200 RSSI
Height : 1.22 m height difference 6 dBm power difference
S1: 4.6022 S2: 1.9371 S3: 0.0090
S4: 11.2586 S5: 7.6377
S6: 2.0158
4.5767 dBm
S1: 4.1134 S2: 7.8446
S3: 12.3849 S4: 12.9487
S5: 0.4060 S6: 7.2592
The Effect of Height
The Effect of Different Parameters on RSSI
Two different sets of data at two different height with 1.22 m height difference was compared (Test1 & Test2 was done at two different time/Env-Conditions)
Test Scenario
Test 1AvgErr AbsMeanErr
7.4928 dBm
Test 2AvgErr AbsMeanErr
All in dBm
All in dBmReported Error for the Same Chip is 10
dBm for 1m height difference
CC2420 RSSI Evaluation
The Effect of Window
Test ScenarioTwo different sets of data at two different situations (at the same place, time and Env-
condition) was compared
Test
AbsMeanErr (All in dBm)
Window : Open/Closed 0.6 dBm power difference
S1: 1.9241 S2: 0.0140 S3: 0.9735 S4: 0.5581 S5: 0.0630 S6: 0.2506
Close to Window
The Effect of Different Parameters on RSSI
CC2420 RSSI Evaluation
The Effect of Door
Test ScenarioTwo different sets of data at two different situations (at the same place, time and Env-
condition) was compared
Test
AbsMeanErr (All in dBm)
Door : Open/Closed 1.5 dBm power difference
S1: 3.5996 S2: 0.0005 S3: 0.7787 S4: 1.9850 S5: 1.9377 S6: 0.0354
Close to Door
The Effect of Different Parameters on RSSI
CC2420 RSSI Evaluation
- Due to the need of calibration, error should be lower that this
The Effect of Different Parameters on RSSI
The Effect of Lights
Test ScenarioTwo different sets of data at two different situations (at the same place, time and Env-
condition) was compared
Lights : On/Off 1.7 dBm power difference
S1: 7.7846 S2: 0.0319 S3: 1.0982 S4: 0.8703 S5: 0.5434 S6: 0.0461
Test
AbsMeanErr (All in dBm)
In the order of several 0.1 dBm
CC2420 RSSI Evaluation
- Due to the need of calibration, error should be lower that this
Radiated pattern Vertical mounting Radiated pattern horizontal mounting
Se
ns
ors
(T
x)
Mo
bile
No
de
(Rx)
Lig
ht
Fra
me2
Lig
ht
Fra
me1
12
6
34
5
BrdWal
Win
Dor
The Effect of Antenna Direction
Test ScenarioTwo different sets of data at two different antenna directions (at the same place, time
and Env-condition) was compared
The Effect of Different Parameters on RSSI
Test
AbsMeanErr (All in dBm) 5.5 dBm power difference
CC2420 RSSI Evaluation
?
- Due to the need of calibration, error should be lower that this
Power Distribution
Feasibility Test
Test ScenarioData Received by coordinator located under each sensor (at the time and Env-
condition) was compared
02
4
05
100
50
100
Device 1 & Direction: Brd
-RS
SI
(dB
)
02
4
05
100
50
100
Device 2 & Direction: Brd
-RS
SI
(dB
)
02
4
05
100
50
100
Device 3 & Direction: Brd
-RS
SI
(dB
)
02
4
05
100
50
100
Device 4 & Direction: Brd
-RS
SI
(dB
)
02
4
05
100
50
100
Device 5 & Direction: Brd
-RS
SI
(dB
)
02
4
05
100
50
100
Device 6 & Direction: Brd
-RS
SI
(dB
)
Conclusions
- Due to the need of calibration, there is some uncertainty in these results.
CC2420 RSSI Evaluation
Basic Fingerprinting
)]([),,()([ VectorRSSmeanTxPwDirectionSensorIDIndexCellPosition lkji
Radio Map Elements
By the offset compensation of sensors we can improve the performance
48 runs in different situations (Quiet and Non-Quiet)
Sensors
Mobile Node
Light Frame2
Light Frame1
126
345
1.65 m2.44 m
1 2 3 4 5 6 3 1 4 2 24 4 6 6 5 1 3 3 6 3 4 5 6 4 1 3 1 6 5 2 5 5 3 4 3 6 3 4 5 6 4 3 3 1 6 5 2 5 5 4 4
Expected PositionEstimated Position (SQR)
Estimated Position (ABS)
Max Error 2.44m
Static Test
MobileTest
4 4 4 4 4 4 3 3 2 2 2 3 3 3 3 1 3 1 3 2 6 2 5 5 2 2 2 2 2 6 6 6 6 6 2 2 2 5 2 2 2 6 2 2 2 2 2 2 2 2 2 2 2 2
Estimated Position:
The Effect of Different Parameters on RSSI
CC2420 RSSI Evaluation
Expected Position: 3 4(2) 5(6) 6(5) 2 1 3 4(2) 5(6) 6(5) 2 1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-45
-40
-35
-30
-25
-20
-15
-10
-5
0
5
Distance (m)
Rec
eive
d P
ower
(dB
m)n=2.2, AvgVar= 0.05 & MaxVar= 0.25
Practical PLTheortical PL|Thr-Prc|
NI Power samples
NI RSSI Evaluation
Thank You
The End
Box Whisker Plot (N(0,sigma))