The IEEE 802.16 family of standards uses OFDM or OFDMA (orthogonal frequency division multiple access) operating in TDD or FDD mode. We show that OFDM offers a number of advantages for very high data rate applications, whereas OFDMA is proposed for use by remote sites in the uplink. OFDMA recognises both the typical asymmetry in data rates relative to the downlink and is a practical way to manage the characteristic OFDM peak-to-average power problem.