For many applications, wired interfaces meet these requirements
easily and at low cost. Where cables aren??™t possible or desirable, wireless technologies
are an alternative.
This chapter presents options for selecting and implementing wireless technologies
for transferring asynchronous data.
Chapter 8
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Designing a wireless communication system requires deciding on a transmission
medium, a modulation method if needed, and a protocol for transferring
data.
Wireless data communications typically use infrared (IR) or radio-frequency
(RF) energy. Many wireless systems can transmit and receive data in the asynchronous
format supported by UARTs. Some wireless protocols use other data
formats for greater data throughput, better reliability, or other benefits. When
needed, an intelligent converter module can translate between asynchronous
data and another protocol.
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< 5
Instead of transmitting raw data pulses, many wireless systems transmit a carrier
frequency with the data encoded as variations in the carrier??™s amplitude, frequency,
phase, or a combination of these. The process of encoding information
as variations in a carrier is called modulation. Using a carrier helps the receiver
isolate transmitted data from noise and can increase the distance the data travels.
For basic data communications, two popular modulation methods are on/off
key (OOK) and frequency shift key (FSK).
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