Transcript Nessun titolo diapositiva

University of Brescia
Department of Electronics for the Automation
A. Flammini, D. Marioli, G. Mazzoleni, E. Sisinni, A. Taroni
Actual wireless sensor scenario
Proposed solution
Power supply / wired link
 On-line Coordinator floor noise monitoring
(RSSI) in a 2 active channels architecture
COORDINATOR
COORDINATOR
Channel selection
 Few retries for a fast reconnect time
COORDINATOR
 STAR network topology: isochronous time
slots allocation with ACK (Si)
BPS
BPS
Tcycle
BPS
BPS
BPS
S1
BPS: battery powered sensor
 Low transfer rate (tens bps)
 Filtering of noise estimation
Send (CC)
Send (BC)
N
Send (CC)
CC
ACK ?
ACK ?
Send (CC)
ACK ?
CC
INA110
G=100
Y
N
ACK ?
N
WUSB
Sensor
Tek
RSA3408A
WUSB
Coordinator
WUSB
802.15.4
RF section power
consumption (@3.3V):
RF section power
consumption (@3.3V):
 BC is free ? CC  BC
 TX: 69mA, RX:60mA
 TX: 29mA, RX:33mA
 Sleep: µA, Idle: 2.5mA
 Sleep: µA, Idle: 1mA
 Rebinding procedure when failing condition remains
for more than 2 cycles
Simulated Traffic: channel occupation
Simulations
 Performances evaluation varying floor noise FN, burst number BN and burst
length BL
802.15.4 Coordinator RF consumption
802.15.4 Sensor RF consumption
 Comparison between the proposed solution and standard approach
 Tx power = 3 dBm, Transfer rate = 250kbps
 Index of merit based on Cost where W represents weight of retransmissions
(W =1) and rebinding procedures (W=26)
 Data payload = 100 bytes , ACK = 5 bytes
1
1
0.4
0.2
0.8
0.6
0.4
0
0
0.6
10
20
30
Burst Number (BN)
40
50
0.4
0
0
-70
30
0.2
0.2
0
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
Floor noise [a.u.]
Power spectrum and spectrogram as
measured by RSA 3408A
RSSI as evaluated by RF
transceivers
WUSB
Proposed
WUSB
Proposed
2000
4000
6000
Burst Length (BL)
8000
10000
RSSI CYWUSB6934 [a.u.]
0.6
0.8
Normalized Cost
WUSB
Proposed
0.8
Power spectrum estimation
M = Number of sensors, N = Simulation steps, W = Consumption weight
Normalized Cost
1
 Duty cycle ~ 48 %
-75
CYWUSB6934
-80
MC13192
20
-85
-90
10
-95
2475
2470
2465
2455
2450
2445
2440
2435
M=10
2430
FN = 0.2 , BN = 10, N =
2425
M=10
2420
FN = 0.2 , BL = 2000, N =
-100
2415
M=10
105,
2410
BN = 10, BL = 2000, N =
105,
2405
0
105,
RSSI MC13192 [dBm]
1 1 M N
Cost     Wi, j
M N i 1 j1
Normalized Cost
802.15.4
Coordinator
 Five retransmission in case of no ACK; 2 attempts
on CC plus 1 retransmission on BC then it waits for
a variable time before to retry again on BC and
finally on CC
2460
BC
Y
BC
N
TD
N
Send (BC)
↨
Y ↨
1.5m
“Sniffer”
Sensor
ACK ?
D
1.5m
Rshunt=1.5Ω
 No data from more than 50 % of sensors ? BC  CC
SENSOR
Sn
LeCroy
LT374
 Selection of CC (Clear Channel), BC (Backup
Channel)
Ch = BC
Y
802.15.4
Sensor
 Channels divided in 2 groups
N
Y
Test Bench:
Coordinator
Y
D
Experimental Results
Simulations
Simulations
50% Sensors
Alive ?
S1
 Coordinator dynamically sorts channels according to their
floor noise
 Several insulated star networks
Ch = CC
D
 Reserved “diagnostic” time slot (D) where coordinator
computes channels energy
 Few sensors (Point to Point, Star Topology)
COORDINATOR
Sn
 Additional transceiver to scan all available channels
 Low cycle time (tens s)
Features:
D
MHz
Email: {alessandra.flammini,giuseppe.mazzoleni,daniele.marioli,emiliano.sisinni,andrea.taroni}@ing.unibs.it
Web Site: http://www.ing.unibs.it/~wsnlab/