2D-DPD Research Articles

Multi-dimensional crest factor reduction and digital predistortion for multi-band radio-over-fiber links.

A multi-dimensional crest factor reduction (MD-CFR) technique is proposed to improve the performance and efficiency of multi-band radio-over-fiber (RoF) links. Cooperating with multi-dimensional digital predistortion (MD-DPD), MD-CFR increases the performance of both directly-modulated and externally-modulated RoF links, in terms of error vector magnitude (EVM) and adjacent channel power ratio (ACPR). For directly-modulated RoF link, more than 5 dB output ACPR reduction is obtained, output EVMs are reduced from 11.83% and 12.47% to 7.51% and 7.26% for two bands respectively, while only a slight improvement to 11.58% and 10.78% is obtained solely using MD-DPD. Similar results are achieved in externally-modulated RoF link. Given a threshold in EVM or ACPR, the RF power transmit efficiency is also further enhanced.

Experimental investigation on multi-dimensional digital predistortion for multi-band radio-over-fiber systems

The recently-proposed multi-dimensional digital predistortion (DPD) technique is experimentally investigated in terms of nonlinearity order, memory length, oversampling rate, digital-to-analog conversion resolution, carrier frequency dependence and RF input power tolerance, in both directly-modulated and externally-modulated multi-band radio-over-fiber (RoF) systems. Similar characteristics of the multi-dimensional digital predistorter are identified in directly-modulated and externally-modulated RoF systems. The experimental results suggest implementing a memory-free multi-dimensional digital predistorter involving nonlinearity orders up to 5 at 2 × oversampling rate for practical multi-band RoF systems. Using the suggested parameters, the multi-dimensional DPD is able to improve the RF input power tolerance by greater than 3dB for each band in a two-band RoF system, indicating an enhancement of RF power transmitting efficiency.