The plethora of wireless sensor network development solutions offered
today is overwhelming. It is not possible in any way to give a
comprehensive coverage of the market.
Depending on your selection criteria this could be an easy choice or
could be a difficult process. I spent more than a month looking at
solutions from different vendors before jumping into the depths of new
hardware, APIs and mountains of documentation. Since all these
standards are evolving, the updates from the vendors are exacerbating
the already steep learning curve.
Navigating the proprietary and official standards is difficult,
depending on the marketing flavor experiences at some of the web sites.
Another difficulty is that different hardware/software solutions are
hard to compare, because there is no metric.
It is too hard to determine quantitatively how much better is
certain technology compared to another. The best alternative is to rely
on common sense and some guiding principles, such as open source versus
proprietary code, open communication standard versus one company
solution, etc. This article will present the problems a designer will
face when implementing a wireless sensor network and the factors that
are important in deciding which development platform to select.
Design Challenges for Wireless
Sensor Networks
There are some specifics as far as wireless sensor networks are
concerned. These make the deployment and maintenance of such networks
very different than other widespread network technologies. We need to
be aware of these specific characteristics in order to do a better job
when developing our engineering solutions. Here is a brief description
of the major challenging facts about wireless sensor networks.
Cost. It
is possible, depending on the application, to have hundreds or
thousands of sensor nodes deployed in a single site. That makes the
project cost sensitive. For some trivial uses like light switches and
tire pressure control the expected price is also very low to making
their use economically feasible.
Scalability.
The number of sensor in a deployment may be in the thousands of node,
even millions. With such high numbers new network management issues
arise. This will have a significant impact on maintenance and
diagnostics and will necessitate the widespread use across the
application of new network diagnostic tools.
Fault Tolerance.
Since sensors can be deployed everywhere - on bridges, industrial
sites, homes, farms, etc. - they will be subjected to harsh
environmental conditions and may vandalized, stolen or damaged. What
you want is a network configuration that continues to operate even if
one or more node in the network fails, is stolen or is damanged.
Localization.
In some applications the sensors are deployed sporadically in a
geographical location and thy have to organize them selves and find out
where they are in relation to each other.
Routing. Traditional
routing schemes are not designed to be energy and processing efficient
and are of little use in sensor networks. The approach that should be
pursued in this case is to keep the routing to a minimum, and activated
only when absolutely necessary.
Energy
Efficiency Constraints. Energy efficiency is a very serious
concern, because the sensor nodes have small and limited energy source
such as batteries. Very rarely device will be able to be plugged into
an electrical power outlet. There are software solutions that can
optimize the consumption of the device by switching to energy saving
modes. These solutions take advantage of the hardware features of the
smart sensor chips available today.
