An OFDM system with modified predistorter and MLS

To improve the bit error rate (BER) with a low outband emission, we propose an OFDM system with modified predistorter and maximum likelihood sequences (MLS). In the proposed system, input data are mapped to signal point series over multiple subcarriers. Then, the peak power is reduced with the partial transmit sequence (PTS) technique. After limited to the saturation amplitude of the high-power-amplifier (HPA), the signal is applied to the predistorter. Compared with the system using the conventional predistorter, the compression quantity of signal in the proposed system is small, because the peak power is reduced with the PTS technique beforehand. In addition, the minimum Euclidean distance in the proposed system is larger than that of the conventional system. Thus, the proposed system can improve the BER with the low outband emission. We show that only the proposed system can achieve the good performance in terms of both the BER and power spectrum density (PSD).