Transcript Slide 1

GENERIC AUTONOMOUS PLATFORM FOR SENSOR SYSTEMS:
AN ENVIROMENTAL MONITORING APPLICATION
NSF WORKSHOP ON:
“WIRELESS NETWORKED SENSOR AND ACTUATOR SYSTEMS”
SEPTEMBER 8 AND 9, 2003 - LOS ANGELES, CALIFORNIA
KEY FEATURES
DESCRIPTION
The Generic Autonomous Platform for Sensors (GAP4S)
provides
multiple
integrated
sensing
functions,
transmission range of tens of meters, remote re-charge of
the sensor micro-battery, and end-to-end reliable access.
The above objectives are obtained by combining:
 IC autonomous platform
 Franco Maloberti
PARTICIPANTS:
 low-power (<100 uW)
 plug-in sensor modules
 rechargable micro-battery
 Andrea Fumagalli
 Jin Liu
 Murat Torlak
 Stefano Gregori
 Marco Tacca
 Devrim Aksin
 long range (100 m)
 MW remote recharging
 OOK downlink acknowledgment
 MW/RF wireless link
 Balkan Kecicioglu
 Paolo Monti
 Tianhon Yang
 energy aware protocols
 reliable
 bandwidth efficient
 low latency
base station
base station
end user
A POSSIBLE APPLICATION:
CAR RENTAL PARKING LOT MONITORING
• detection of cars arrival and departure
• precise location of free parking spaces
internet
• automatic car identification
1. a single micro-board with full-custom ultra low-power
IC's (sensing devices and radio frequency transmitter),
high efficiency microwave receiver, micro-battery, and
signal processing capabilities,
2. a unique use of the microwave signal to simultaneously
re-charge the sensor micro-battery, synchronize data
slots, and provide the return link from the base station,
• automated inventory
• security monitoring
• secure car checkout
end user
• on-line access to car availability information
(e.g. car model, color, features)
uplink
3. a power-aware and reliable protocol stack spanning
across both the wireless sensor network and the
existing network infrastructure (the Internet).
downlink
sensor platform
A full-custom chip was designed and fabricated using 0.18
µm CMOS technology on the micro-board. A combined
optical sensor (a low-resolution digital camera together with
an analog motion detector and a low power data converter)
and an RF transmitter (power amplifier and voltage
controlled oscillator (VCO)) are on the chip. The data
converter, used both for recharging the pixels and for 7-bit
data conversion, has 10 µW power consumption. The LCtank VCO has 150 µW power dissipation and a 100 dBc/Hz
phase noise (at 1 MHz offset). The class E power-amplifier
has power efficiency higher than 80%.
A 433 MHz FSK modulation has been chosen in the
communication link sensor-base-station. FSK eliminates the
need for a linear power-amplifier, thus reducing power
consumption. The multiple-access of the sensors is
accomplished with a hybrid frequency and time division
scheme. An empirical path loss model for distances up to
100 meters has been developed. The smart antenna basestation has been designed.
Two tasks were addressed in the field of network
architecture and protocols. First, an original approach to
maximize the lifetime of a cluster-based system was
examined. A greedy algorithm able to determine the optimal
assignment of nodes to cluster-heads was designed.
Second, the end-to-end communication reliability between
the base-station and the end-user was investigated. A
dynamic algorithm able to reduce the overall network
blocking probability by efficiently making use of network
spare resources was presented.
SENSOR PLATFORM
WIRELESS LINK
NETWORKING
The autonomous platform is designed to integrate different types of plug-in
sensors. The most critical sensors for the application are image sensors.
An ultra-low power motion triggered imager has been designed to validate
the GAP4S concept.
UPLINK
Ad hoc Network Design Algorithm (ANDA)
SENSOR PLATFORM
The platform includes in the same
micro-board: custom chips, a microbattery and commercial parts. Since
all the devices are powered by the
micro-battery which is remotely
recharged via microwave from the
base station, power consumption is
the major design constraint.
OPTICAL SENSOR
It contains a 0.18 µm CMOS 64 × 64
photodiodes array used as digital
imager and as analog motion detector.
An ADC operating at 200 kHz is used
for both recharging the pixel and for a 7bit data conversion without requiring a
charge amplifier. The ADC power
consumption is 10 µW (figure-of-merit:
0.18 pJ/conversion).
RF TRANSMITTER
It contains a CMOS class E switched-mode PA with adjustable power
levels (-2, 0, 4 dBm) and an efficiency >80%, and a LC-tank VCO with a
phase noise of 100 dBc/Hz at 1 MHz offset frequency and 150 µW power
consumption.
RF RECEIVER
It contains a rectifier based on a GaAs Schottky diode used to recharge the
micro-battery with an average efficiency of 50%.
• Modulation
• Center Frequency
• Output Power
• BER
• Expected Communication Range
: BFSK
: 433.92 MHz
: 4 dBm
: 10-3
: 100 m (outdoor)
60 m (indoor)
• Network lifetime: time
period from when the
network starts functioning
to the instant in which
the first node runs out of
energy
Transmitted Power vs Distance BER = 10-3
• Objective: maximize the
network lifetime by
determining the optimal
assignment of nodes to
cluster-heads
Antenna Gains = 0 dBi
Transmitted
Power(dBm)
ACTIVITIES
base station
15
10
5
0
-5 0
-10
-15
-20
-25
-30
-35
20
40
60
80
100
120
Outdoor
Indoor
(a)
(b)
• Two different scenarios : a) network energy
configuration computed only once, b) network
energy configuration is periodically updated
Distance(m)
Communication distance is reduced
indoor because of high loss. This can
be compensated using beamforming
and coding in base stations
Beamforming gain is
10log10(M) dB, where M
is the number of
antennas
BFSK modulation: An appropriate solution for low power
applications
Freespace Pathloss model with pathloss exponent 3
indoor
DOWNLINK
• Modulation : OOK
• Frequency : 2.4 GHz
• Microwave signals: Energy source to recharge micro-batteries in the
sensors.
Dynamic SPP Protection scheme with Differentiated Reliability (DiR)
- DSPP-DiR
• DiR: each connection
has a maximum
conditional failure
probability (MCFP) that
must be met by the
protection scheme
• Objective: minimize
the probability that a
traffic request is blocked
while satisfying the
request reliability
degree.
(a)
(b)
• Blocking probability as a function of: a) the
network load and b) the reliability degree