7.5.2 Equalization In OFDMA
Channel equalization in OFDM is achieved by replacing data symbols with pilot symbols at known positions in the OFDM symbol as shown in Figure 7.16. Since the decoder knows the precise amplitude and phase of these pilot signals, the amount of phase and amplitude change caused by the channel can be calculated using the received version of the pilot signals. Once these channel characteristics are calculated for the pilot signals they are then estimated for the remaining data cells in the symbol and subsequently the distortion can be removed. It is much easier to remove this type of distortion for individual sub-carriers than it is to equalize a single high symbol-rate transmission.
