Information Technology Reference
In-Depth Information
Sensing
unit
Processing
unit
Communication
unit
Processor
Sensor
board
ADC
Transceiver
Storage
Power unit
Figure 5.1
An overview of a sensor device.
The main functionality of the sensing unit is to closely estimate parame-
ters, such as measuring the current temperature or detecting a specific gas in
the monitored area. An analog signal is generated by the sensing unit, which
is corresponding to the observed parameters. Then, the analog waveform is
digitized by an analog-to-digital converter (ADC), which then is delivered to
the processing unit for further analysis [4]. The sensing unit is considered a
bottleneck because the sensing technologies are following at a slower pace
than those of the semiconductors [14].
The processing unit plays a major role in managing the tasks within
the device and collaborating with other sensors to achieve the predefined
tasks. There are currently several families of the processing unit, includ-
ing a microcontroller, microprocessor, and field programmable gate array
(FPGA). A nonvolatile memory and interfaces, such as analog-to-digital con-
verters (ADCs), can be integrated onto a single integrated circuit [4,9]. The
processing unit needs storage for saving all its executed tasks and packag-
ing all collected data for later transmission.
The communication unit is comprised of a transceiver, which acts as the
connection between a sensor device and the rest of the network. The trans-
ceiver can be implemented in three communication schemes, including either
an optical, infrared, or radio frequency (RF). The optical communication con-
sumes less energy than RF and it provides a high security. However, the opti-
cal communication requires a line-of-sight and it is sensitive to atmospheric
conditions [12]. The infrared, like optical communication, needs no antenna,
but it is limited in its broadcasting capacity. The RF is the most easy to use,
but it requires an antenna (an extra hardware component needs to be added
into the sensor device).
The power unit is a major weakness of the sensor networks. Any energy
preservation schemes can help to extend a sensor's lifetime. Batteries
