Digital Pre-Compensation Techniques Enabling Cost-Effective High-Order Modulation Formats Transmission

Digital pre-compensation complementary to post equalization increases the digital signal processing (DSP) compensation envelope, especially in non-linear band-limited channels. The DSP at the transmitter relies on the availability of high-speed and high-resolution digital-to-analog devices to generate complex analog waveforms. However, one major challenge in high-speed digital-to-analog converter (DACs) technology is the limited resolution, which introduces dominant quantization distortions. Here, a new dynamic quantization technique is proposed, based on the fact that the quantization is a non-linear deterministic operation. Extensive lab experiments and numerical simulations demonstrate signal to quantization noise ratio improvement of up to 8 dB. In addition, an extremely low complexity modified Volterra digital pre-distortion (DPD) is developed, using orthogonal polynomial basis functions. Efficient grading method of the most dominant orthogonal dimensions is developed. The method combines both the dimensions variances and the impact of the information projection on each of the dimensions. The newly proposed modified Volterra DPD is shown to maximize the DPD performance while minimizing the number of required series dimensions. Extensive sets of lab experiments and simulations are performed, indicating potential saving of up to 89% in the amount of useful dimensions with a negligible error vector magnitude (EVM) penalty.