Making Things Talk

218 MAKING THINGS TALK

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.

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, and if you’re using radio, all kinds of elec-

tromagnetic 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 correction.

Just as you started learning about networks by starting

with the simplest one-to-one network in Chapter 2, you

started 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 control-

ler, and each object on the network can talk to any other

object. You’ll see both Ethernet and wireless examples.

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Conclusion

Wireless communication involves some significant differences