1. An apparatus for transmitting OFDM data, including a plurality of frequency domain data symbols, the transmitter comprising: a converter arranged in operation to convert a plurality of frequency domain data symbols and a plurality of training symbols in a corresponding plurality of substantially orthogonal frequency subchannels to a time domain burst for transmission, the training symbols having a pre-defined value; and transmitter arranged in operation to transmit the time domain burst, such that a receiver receiving the transmitted time domain burst is able to use the transmitted training symbols to estimate the channel responses for the subchannels by converting the received time domain burst into a set of values for the set of subchannels, extracting the training symbols from the results of converting the received burst, determining weights for the extracted training symbols based on measured statistics indicative of noise and/or interference, and using the determined weights to estimate the channel responses for the subchannels.