| Orthogonal frequency division multiplexing (OFDM) has been widely adopted in newer communications systems due to its high spectral efficiency and resistance to multipath fading and impulse noise. However, because of its large peak-to-average power ratios (PAPRs), OFDM has two main disadvantages: sensitivity to frequency offset and nonlinear distortion. Nonlinear distortion is introduced primarily by the high power amplifier (HPA). The HPA is commonly considered to be memoryless, which means that the current output depends on the current input only. However, for applications with wider bandwidths, the memory effects of the whole system cannot be ignored.; This thesis proposes a general solution to compensate for the nonlinearity of the HPA with memory effects at the transmitter side. Mean square error (MSE) minimization is used to derive the predistorter, which is modelled as a simplified finite order Volterra system. (Abstract shortened by UMI.)... |
