An apparatus comprising: a transmitter configured to: apply input data as a frequency-domain data sequence to modulate a set of subcarriers; separate the frequency-domain data sequence into a first subsequence of elements and a second subsequence of elements; form a first conjugate symmetric subsequence that is based on inserting a zero value into the first subsequence (402, 702), and form a second conjugate symmetric subsequence that is based on inserting a zero value into the second subsequence (404, 704), the zero values inserted at different positions in the first and second subsequences; and wherein the transmitter is to further: form a modified first subsequence by setting the 0th element of the modified first subsequence to a real number, and setting the [N/2-1]th element of the modified first subsequence to a real number; and inserting the zero value into the first subsequence, and form a modified second subsequence by setting the 0th element of the modified second subsequence to a real number, and setting the [N/2-1]th element of the modified second subsequence to a real number; and inserting the zero value into the second subsequence; extend the modified first subsequence to the first conjugate symmetric subsequence, and expand the modified second subsequence to the second conjugate symmetric subsequence; wherein the transmitter is configured to apply an inverse discrete Fourier transform (IDFT) on the first conjugate symmetric subsequence and on the second conjugate symmetric subsequence, the IDFT applied individually on the first conjugate symmetric subsequence and on the second conjugate symmetric subsequence, or the IDFT applied on a complex sequence formed from the first conjugate symmetric subsequence and the second conjugate symmetric subsequence; wherein the transmitter is configured to generate a time-domain sequence of complex numbers, the time-domain sequence comprising a real component that is a function of the first conjugate symmetric subsequence, and an imaginary component that is a function of the second conjugate symmetric subsequence; wherein the first component comprises an in-phase, I, component, and the second component comprises a quadrature-phase, Q, component. a transmitter configured to: apply input data as a frequency-domain data sequence to modulate a set of subcarriers; separate the frequency-domain data sequence into a first subsequence of elements and a second subsequence of elements; form a first conjugate symmetric subsequence that is based on inserting a zero value into the first subsequence (402, 702), and form a second conjugate symmetric subsequence that is based on inserting a zero value into the second subsequence (404, 704), the zero values inserted at different positions in the first and second subsequences; and apply input data as a frequency-domain data sequence to modulate a set of subcarriers; separate the frequency-domain data sequence into a first subsequence of elements and a second subsequence of elements; form a first conjugate symmetric subsequence that is based on inserting a zero value into the first subsequence (402, 702), and form a second conjugate symmetric subsequence that is based on inserting a zero value into the second subsequence (404, 704), the zero values inserted at different positions in the first and second subsequences; and wherein the transmitter is to further: form a modified first subsequence by setting the 0th element of the modified first subsequence to a real number, and setting the [N/2-1]th element of the modified first subsequence to a real number; and inserting the zero value into the first subsequence, and form a modified first subsequence by setting the 0th element of the modified first subsequence to a real number, and setting the [N/2-1]th element of the modified first subsequence to a real number; and inserting the zero value into the first subsequence, and form a modified second subsequence by setting the 0th element of the modified second subsequence to a real number, and setting the [N/2-1]th element of the modified second subsequence to a real number; and inserting the zero value into the second subsequence; extend the modified first subsequence to the first conjugate symmetric subsequence, and expand the modified second subsequence to the second conjugate symmetric subsequence; wherein the transmitter is configured to apply an inverse discrete Fourier transform (IDFT) on the first conjugate symmetric subsequence and on the second conjugate symmetric subsequence, the IDFT applied individually on the first conjugate symmetric subsequence and on the second conjugate symmetric subsequence, or the IDFT applied on a complex sequence formed from the first conjugate symmetric subsequence and the second conjugate symmetric subsequence; wherein the transmitter is configured to generate a time-domain sequence of complex numbers, the time-domain sequence comprising a real component that is a function of the first conjugate symmetric subsequence, and an imaginary component that is a function of the second conjugate symmetric subsequence; wherein the first component comprises an in-phase, I, component, and the second component comprises a quadrature-phase, Q, component.