OFDM and related methods for broadband mobile radio channels

A comparison is made of multicarrier and single carrier modulation schemes for radio communication systems. In both schemes, the fast Fourier transform (FFT) and its inverse are utilized. For OFDM (orthogonal frequency division multiplexing), the inverse FFT transforms the complex amplitudes of the individual subcarriers at the transmitter into the time domain. At the receiver, the inverse operation is carried out. For single carrier modulation, the FFT and its inverse are used at the input and output of the frequency domain equalizer in the receiver. Different single carrier and multicarrier transmission systems are simulated with time-variant transfer functions measured with a wideband channel sounder. For OFDM, the individual subcarriers are modulated with fixed and adaptive signal alphabets. In particular, the performance degradation of single carrier and multicarrier transmission due to pilot-aided channel estimation is analyzed.