Can you please explain the differences between coding and modulation?

I am a very interested reader of your WLAN expert tips and have already learned a lot about this hot topic from your tips.

Sometimes when reading the various articles about the WLAN standards I get a bit confused by the use of the terms 'coding' and 'modulation'.

Can you give me (us) a brief explanation and describe the differences between coding and modulation, or maybe direct me to other good information about this subject.

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These radio-engineering terms confuse me sometimes, too. The searchNetworking definition for modulation is the addition of information (or the signal) to an electronic or optical signal carrier. For example, Quadrature Amplitude Modulation (QAM). Other useful sites to learn about modulation include DXing.com and TelecomWriting.com.

Coding or encoding refers to how your recast information from one format to another. For example, the decimal number "15" can be encoded as a binary number "1111" or the hexadecimal number "F." CCK and OFDM are two coding techniques used in 802.11b and 802.11g wireless LANs.

In a wireless LAN network, digital data must be encoded and then modulated with a carrier signal for radio transmission. For example, in an 802.11a WLAN, the coding technique OFDM is used with the modulation technology 64QAM to send data at 54 Mbps. Think of coding as deciding how to represent the data and modulation as the way data is actually converted into radio waves.

This was first published in August 2003

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