Phase-Aligned Complex Linear Physical-Layer Network Coding in OFDM-VLC Two-Way Relay Network

We propose and experimentally demonstrate a phase-aligned complex linear physical-layer network coding (PA-CLPNC) scheme in orthogonal frequency division multiplexing (OFDM) visible light communication (VLC) two-way relay network (TWRN). The proposed scheme, based on the finite field of the Gaussian integer, achieves PNC of high-order QAMs and reduces the constellation size of the superposed signal at the relay before broadcasting it back to users. We further adopt a phase alignment strategy to enhance the minimum Euclidean distance between classes, into which the constellation points of the superposed signal at the relay are categorized. VLC-TWRN experiments with throughput of 600Mbit/s-1.47Gbit/s, using either uniform 8QAM/16QAM OFDM or bit-and-power loading, show that the proposed PA-CLPNC achieves one to two orders of magnitude reduction in the bit error ratio compared to the conventional amplify-and-forward PNC scheme.