Abstract: One way to improve the performance of OFDM system is to use adaptive modulation. However, accurate channel state information (CSI) is required at the transmitter to achieve the benefits. Imperfect CSI arises from noisy channel estimates, which may also be outdated duo to a delay in getting the CSI to the transmitter. Adaptive OFDM with both perfect and imperfect CSI is studied. Performance results are provided for this system with imperfect CSI.

Key words: OFDM, channel state information, adaptive modulation