Architectures for Joint Compensation of RoF and PA with Nonideal Feedback

A high capacity wireless communication system requires careful design to minimize interference and distortion effects. This paper considers the adaptive predistortion of the nonlinear distortions induced by a Radio over Fiber (RoF) link and power amplifier (PA) connected in series. In particular, we study the architectures for the joint compensation of the nonlinearities in the presence of nonideal feedback. From the adaptive algorithm point of view, we study different combinations of algorithms for the predistortion. Our simulation results indicate that combined use of least mean squares (LMS) and recursive least squares (RLS) gives the best trade-off between complexity and performance. In addition, we show that the use of nonideal feedback causes a collapse in the performance of the predistortion. However, when using a compensated RoF link for feedback, the degradation of the adjacent channel power is very small compared to the case of the ideal feedback.