W-band PAM-4 wireless delivery employing intensity modulation and coherent detection based on CMMA equalization

Abstract

We have experimentally demonstrated PAM-4 signals generation and millimeter wave wireless transmission at 90-GHz W-band, respectively, enabled by using an intensity modulator and coherent receiver. The bit-error-ratio (BER) performance can be improved significantly by the offline digital-signal processing (DSP) including cascaded multi-modulus algorithm (CMMA) equalization at the receiver side. We also investigated the DSP process difference between PAM-2 and PAM-4 signals recovery. The experimental results show that up to 10-Gb/s PAM-2 signal and 12-Gb/s PAM-4 signal over 9-m free space wireless delivery can be realized with a BER less than 7% hard-decision forward-error-correction (HD-FEC) threshold of 3.8x10-3. To the best of our knowledge, this is the first time to achieve W-band PAM signal wireless transmission based on coherent detection. Our proposed scheme has important practical application of significance for the 5G broadband network.