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Wireless Intelligent Sensor and Actuator Network (WISAN)
is a scalable ultra-low-power platform for sensing applications.
Existing sensor networks do not completely satisfy requirements of problems
posed by structural health monitoring: the proactive, constant data rate character of the
data streams rather than reactive, event-driven data delivery; real-time requirements to
bidirectional data flow from sensors and to actuators.
WISAN is designed to address these
issues and support massive arrays of
heterogeneous sensors with constant data
streams. Development of WISAN is funded by
New York State Energy Research and
Development
Authority
(NYSERDA)
and
industry.

Current design is the second generation
of the WISAN platform, offering additional
capabilities and ready for manufacturing and
marketing in various applications.
WISAN offers the following functionality:

1. Low-cost massive data acquisition from arrays of heterogeneous sensors with
constant data streams forming a distributed data acquisition system. Providing
uninterrupted, steady streams of data is the focus of the network. Other
platforms, like Tiny OS, do not have such capabilities.

2. Ultra-low power consumption of a sensor node is achieved through efficient
optimization of wireless protocols that minimize the amount of time the
transceiver is powered during operation and virtually eliminate collisions,
retransmissions and packet loss.
3. Each node in the network keeps precise global time that is continuously
updated and kept synchronized on the order of few microseconds. This feature
enables "wired-like" behavior, where a data sample is taken at exactly the
same moment by all nodes in the network. Again, this feature is not available
in Tiny OS and other platforms.
WISAN1.1 node vs. WISAN 2 node
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4. Transparent scheduling extension on top of IEEE802.15.4 protocol enable
almost 100% efficient bandwidth utilization by eliminating network collisions
and providing 3-5 times more bandwidth compared with traditional CSMA-CA.
This feature allows either to increase the network size or to increase node
throughput by a factor of 3-5.

5. Low latency of the data transmission allows implementation of wireless control
loops. Low latency is ensured through the same scheduling protocol.

6. WISAN is fully compatible with IEEE 802.15.4 and can be utilized worldwide in
2.4Ghz ISM frequency band and coexists with WiFi and other devices. The
coordinator node self-selects the best channel based on results of energy
scans.

7. Sensor node design allows a variety of external extensions on stackable
boards. Interface pins include digital IO, analog in and analog out, SPI, I
2
C, and
serial interface.
WISAN 2 platform offers the following additional capabilities that were added over
basic WISAN1.1 design:

optional
micropower
24-bit
ADC
with
programmable gain, offset and antialiasing
circuitry, adding capability for easy interfacing
of differential sensors
micropower on-board voltage regulator allows
a wider range
of voltages, maximizing
utilization
of
battery
capacity
and
accommodating various power sources
1Mb flash memory for on-board storage
32Khz oscillator for real time clock and low-
power modes
a solderable connector for reliable sensor
board connection
additional LED, mounting holes, reset and user buttons
Hardware and software components of the WISAN 2 platform enable its utilization
in a variety of applications, including monitoring of transportation infrastructure.

06/25/2006
Rear view of WISAN 2 node