A method comprising: allocating a first number of bits per symbol to a carrier tracking subcarrier of a plurality of subcarriers of an orthogonal frequency division multiplexing, OFDM, signal, the carrier tracking subcarrier being a subcarrier of the OFDM signal that is used to communicate payload data with a reduced likelihood of errors in data recovery as compared to other subcarriers of the OFDM signal, such that the receiver generates receiver parameters based on the payload data received using said carrier tracking subcarrier, and wherein the first number of bits is based on a first target signal-to-noise ratio, SNR, margin; allocating numbers of bits per symbol to other subcarriers of the plurality of subcarriers based on a second target SNR margin, wherein the first target SNR margin is greater than the second target SNR margin, communicating data using the OFDM signal, the first number of bits per symbol modulating the carrier tracking subcarrier and the numbers of bits per symbol modulating the other subcarriers of the plurality of subcarriers, characterised by: wherein the allocating the first number of bits per symbol comprises determining a maximum number of data bits that provides the first target SNR margin with respect to a SNR estimate for the carrier tracking subcarrier, the SNR estimate being generated from known data, wherein the allocating numbers of bits per symbol to the other subcarriers comprises determining maximum numbers of data bits that provide the second target SNR margin with respect to SNR estimates, generated from the known data, for the other subcarriers, and selecting the carrier tracking subcarrier from the plurality of subcarriers of the OFDM signal based on the SNR estimates for the plurality of subcarriers. allocating a first number of bits per symbol to a carrier tracking subcarrier of a plurality of subcarriers of an orthogonal frequency division multiplexing, OFDM, signal, the carrier tracking subcarrier being a subcarrier of the OFDM signal that is used to communicate payload data with a reduced likelihood of errors in data recovery as compared to other subcarriers of the OFDM signal, such that the receiver generates receiver parameters based on the payload data received using said carrier tracking subcarrier, and wherein the first number of bits is based on a first target signal-to-noise ratio, SNR, margin; allocating numbers of bits per symbol to other subcarriers of the plurality of subcarriers based on a second target SNR margin, wherein the first target SNR margin is greater than the second target SNR margin, communicating data using the OFDM signal, the first number of bits per symbol modulating the carrier tracking subcarrier and the numbers of bits per symbol modulating the other subcarriers of the plurality of subcarriers, characterised by: wherein the allocating the first number of bits per symbol comprises determining a maximum number of data bits that provides the first target SNR margin with respect to a SNR estimate for the carrier tracking subcarrier, the SNR estimate being generated from known data, wherein the allocating numbers of bits per symbol to the other subcarriers comprises determining maximum numbers of data bits that provide the second target SNR margin with respect to SNR estimates, generated from the known data, for the other subcarriers, and selecting the carrier tracking subcarrier from the plurality of subcarriers of the OFDM signal based on the SNR estimates for the plurality of subcarriers. wherein the allocating the first number of bits per symbol comprises determining a maximum number of data bits that provides the first target SNR margin with respect to a SNR estimate for the carrier tracking subcarrier, the SNR estimate being generated from known data, wherein the allocating numbers of bits per symbol to the other subcarriers comprises determining maximum numbers of data bits that provide the second target SNR margin with respect to SNR estimates, generated from the known data, for the other subcarriers, and selecting the carrier tracking subcarrier from the plurality of subcarriers of the OFDM signal based on the SNR estimates for the plurality of subcarriers.