link budget 802.11g

Hello ,
I'm a student and I have to compute a budget link for 802.11g.
I read that OFDM is used to achieve 54Mbit/s. I know that I shoud fellow this steps :
- compute the EIRP
- compute the losses (free space loss...)
- compute the receiver antenna gain
- compute the the antenna noise tempurature (reception)

but I don't know if there's some gain to add thanks to the use of OFDM.

thanks

http://skypilot.trilliantinc.com/pdf...are/lb_4.9.pdf