The OFDM PHY specification leaves implementers a great deal of latitude in selecting techniques for noting a busy channel. Received signal strength thresholds determine whether the channel is in use, but the main guideline for 802.11a equipment is that it must meet certain performance standards. Implementations are free to use the Packet Length field from the PLCP header to augment clear channel assessment, but this is not required. 2 An Example of OFDM Encoding OFDM encoding, as you can no doubt see by now, is an intense, multistep process. One of the additions that 802.11a made to the original specification was Annex G, an encoding of Schiller's Ode to Joy for transmission over an 802.11a network.[2] Shortly after 802.11a was published, the IEEE 802.11 working group discovered several errors in the example and published a correction. If you are interested in learning about OFDM encoding in detail, you can refer to this example.
