A Simple Envelope-Assisted RF/IF Digital Predistortion Model for Broadband RoF Fronthaul Transmission

For emerging 5G fronthaul, broadband radio over fiber (RoF) transmission has been found much more cost-effective than conventional digital fiber transmission. Current digital predistortion (DPD) techniques may not be effective in linearizing broadband RoF links. This work presents a simple envelope-assisted radio frequency (RF)/intermediate frequency (IF) DPD model for linearization of broadband/multiband RoF transmission. The model uses both RF/IF signals and baseband envelopes, resulting in the short-term and long-term memory effect mitigated efficiently even for high signal bandwidth. The model complexity is lower than the existing baseband DPDs and does not increase with the increase of the signal bands. The model is experimentally evaluated in three scenarios: two 20 MHz long-term evolution (LTE) signals spaced by 100 and 40 MHz, and three 20 MHz LTE signals spaced by 50 MHz. It is shown that the proposed DPD results in comparable performance as today's baseband models.