CDF estimation for pre-distortion of non-linear high power amplifiers

Efficient use of High Power Amplifiers (HP A) in communications systems, where power consumption is of primary concern, can be achieved taking maximum advantage of the whole available dynamic range. This means that it is desirable to operate the HPA as near saturation as possible most of the time. Thus, any efficiency improvement can only be obtained at the cost of high AM/AM and AM/PM distortion due to the non-linearity of the HPA. This becomes more critical when non-constant amplitude modulations, such as OFDM and MQAM, are applied. In this work we present an efficient pre-distortion scheme based on statistical properties between sets of input and output signal samples at the HPA. The estimation of the cumulative distribution functions (CDF) is obtained by means of order statistics and then applied in the pre-distortion design, providing a self-adaptive compensation of the non-linearity with a very low computational cost.