What is the forward error correction in 802.11a?
From the official standard, IEEE Std 802.11a-1999, Part 11, section 17.3.5.5 Convolutional encoder, see the rate 1/2 code:



The resulting two streams A and B are interleaved bit-alternatingly.

The other rates (2/3 and 3/4) are achieved through puncturing (as defined on the page right after).

Since this code can't deal with anything that deserves the name "burst error", which in the context of OFDM means "wideband disturbance" (in this case, "interference spanning more than 3 subcarriers" is impossible to correct reliably), there's an interleaver following this. Don't forget that in your implementation.

By modern standards, this is not an overly impressive code, to be honest.