Predistortion study of Radio over Fibre link

The concept of virtual MIMO (multiple-input multiple output) has been proposed to tackle the challenges arising from high data rate wireless communications. Connecting a central unit (CU) with remote antenna units (RAUs), Radio over Fibre (RoF) links are an essential part of the virtual MIMO systems. This paper considers the adaptive compensation of the nonlinear distortions introduced by a RoF link and power amplifier (PA) connected in series. For the predistorter, we study the effects of the fixed point calculation to the performance. Our simulation results indicate that a fixed point predistorter with reasonably low word lengths gives almost the same performance as a floating point predistorter. Hence, it is possible to implement a feasible, low cost and energy consumption, fixed point predistorter into a field-programmable gate array (FPGA).