A transmitting device for transmitting data symbols and pilot symbols in an OFDM transmission system; the device comprising symbol generating means for generating said data symbols and said pilot symbols, means for transmitting said data symbols and pilot symbols respectively by using a plurality of subcarriers of said OFDM transmission system, wherein said symbol generating means is designed to selectively generate a first type pilot symbol and a second type pilot symbol being orthogonal to said first type pilot symbol so that a pilot symbol pattern in the frequency dimension comprises at least said first type pilot symbol to be transmitted by using a predefined subcarrier and second type pilot symbol to be transmitted by using other predefined subcarrier, and wherein said pilot symbol pattern has a different pattern from a succeeding pilot symbol pattern in time dimension.