A method of inserting pilot symbols among data symbols in Orthogonal Frequency Division Multiplexing, OFDM, frames at an OFDM transmitter having at least two transmitting antennas (37, 42, 140, 142), the OFDM frames having a time domain and a frequency domain, each OFDM frame comprising a plurality of OFDM symbols in the time domain and a plurality of sub-carriers in the frequency domain, the method comprising the steps of: for a first antenna of the OFDM transmitter: inserting scattered pilot symbols (126, 128) among a first set of data symbols in a scattered pattern in time-frequency by inserting a first set of pilot symbols in a first scattered pattern in time-frequency and inserting a second set of pilot symbols (126, 128) in a second scattered pattern in time-frequency at the same frequencies as the first pattern, offset by one OFDM symbol in the time domain compared to the first pattern; for a second antenna of the OFDM transmitter, inserting scattered pilot symbols among a second set of data symbols using the same scattered pattern in time-frequency, which is used for the first antenna, by inserting a third set of pilot symbols using the first scattered pattern in time-frequency at the same frequencies and symbol locations as the first scattered pattern and inserting a fourth set of pilot symbols using the second scattered pattern in time-frequency at the same frequencies and symbol locations as the second scattered pattern; wherein the data symbols are transmitted at a transmitting data symbol power level, and wherein the pilot symbols are transmitted with an increased power level and wherein the increase is dynamically adjusted with respect to modulation type applied to the sub-carriers carrying the data or depending on a value reflective of channel conditions. for a first antenna of the OFDM transmitter: inserting scattered pilot symbols (126, 128) among a first set of data symbols in a scattered pattern in time-frequency by inserting a first set of pilot symbols in a first scattered pattern in time-frequency and inserting a second set of pilot symbols (126, 128) in a second scattered pattern in time-frequency at the same frequencies as the first pattern, offset by one OFDM symbol in the time domain compared to the first pattern; inserting scattered pilot symbols (126, 128) among a first set of data symbols in a scattered pattern in time-frequency by inserting a first set of pilot symbols in a first scattered pattern in time-frequency and inserting a second set of pilot symbols (126, 128) in a second scattered pattern in time-frequency at the same frequencies as the first pattern, offset by one OFDM symbol in the time domain compared to the first pattern; for a second antenna of the OFDM transmitter, inserting scattered pilot symbols among a second set of data symbols using the same scattered pattern in time-frequency, which is used for the first antenna, by inserting a third set of pilot symbols using the first scattered pattern in time-frequency at the same frequencies and symbol locations as the first scattered pattern and inserting a fourth set of pilot symbols using the second scattered pattern in time-frequency at the same frequencies and symbol locations as the second scattered pattern; wherein the data symbols are transmitted at a transmitting data symbol power level, and wherein the pilot symbols are transmitted with an increased power level and wherein the increase is dynamically adjusted with respect to modulation type applied to the sub-carriers carrying the data or depending on a value reflective of channel conditions.