title: Improving performance of mobile fronthaul architecture employing high order delta-sigma modulator with PAM-4 format.
abstract: An improved high-order delta-sigma modulator with multi-level quantizer is proposed to enable carrier aggregation of 4G-LTE signals in mobile fronthaul. Different from conventional delta-sigma modulation-based digital mobile fronthaul, a 2-bit quantizer is employed to reduce the quantization noise, which enabling the transmission via PAM-4 based IM-DD channel. Moreover, we employ the 4th-order high-pass filter (HPF) to replace the 1st-order HPF in the conventional delta-sigma modulator, resulting in a much better noise shaping performance. In the experiment, a PAM-4 based mobile fronthaul transmission of 32 aggregated 4G-LTE signals with a CPRI equivalent data rate of 39.32-Gb/s is demonstrated in a single-λ 10-Gb/s IM-DD channel. Significant improvement of 68% is achieved in the average EVM performance compared to the previous delta-sigma modulation-based digital mobile fronthaul.
authors.forename: Haibo
authors.initials: H
authors.lastname: Li
authors.forename: Rong
authors.initials: R
authors.lastname: Hu
authors.forename: Qi
authors.initials: Q
authors.lastname: Yang
authors.forename: Ming
authors.initials: M
authors.lastname: Luo
authors.forename: Zhixue
authors.initials: Z
authors.lastname: He
authors.forename: Peng
authors.initials: P
authors.lastname: Jiang
authors.forename: Yongpiao
authors.initials: Y
authors.lastname: Liu
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.forename: Shaohua
authors.initials: S
authors.lastname: Yu