Hardware Reference
In-Depth Information
Conclusion
Wireless communication involves some significant differences from wired communication.
Because of the complications, you can't count on the message getting through like you
can with a wired connection, so you have to decide what you want to do about it.
If you opt for the least-expensive solutions, you can just
implement a one-way wireless link with transmitter-receiver
pairs and send the message again and again, hoping that
it's eventually received. If you spend a little more money,
you can implement a duplex connection, so that each
side can query and acknowledge the other. Nowadays, a
duplex connection is the standard, as the cost difference
is minimal and the availability of transmitter-receiver pairs
is waning. Regardless of which method you choose, you
have to prepare for the inevitable noise that comes with a
wireless connection. If you're using infrared, incandescent
light and heat act as noise; if you're using radio, all kinds
of electromagnetic sources act as noise, from microwave
ovens to generators to cordless phones. You can write your
own error-checking routines but, increasingly, wireless
protocols like Bluetooth and ZigBee are making it possible
for you to forget about that, because the modules that
implement these protocols include their own error correc-
tion.
Just as you started learning about networks by working
with the simplest one-to-one network in Chapter 2, you
began with wireless connections by looking at simple pairs
in this chapter. In the next chapter, you'll look at peer-to-
peer networks, in which there is no central controller, and
each object on the network can talk to any other object.
You'll see both Ethernet and wireless examples.
X
urban Sonar by Kate Hartman, Kati London, and Sai Sriskandarajah
The jacket contains four ultrasonic sensors and two pulse sensors. A microcontroller in the jacket communicates via Bluetooth to your mobile
phone. The personal space bubble, as measured by the sensors, and your changing heart rate, as a result of your changing personal space,
paint a portrait of you that is sent over the phone to a visualizer on the Internet.
