Cyclic prefix length optimization in OFDM-MMWOF/PAM4-FSO integrated system for future generation smart wireless communication

We have proposed and analysed a hybrid orthogonal frequency division multiplexing-milimeter wave over fiber (OFDM-MMWOF) with optimized cyclic prefix (CP) length/ four levels pulse amplitude-free space optics (PAM4-FSO) transmission system based on polarization multiplexing (POLMUX) technique for future wireless communication. Here, we generate and transmit 12 Gbps/60 GHz OFDM MMW and 10 Gbps PAM4 signal simultaneously by employing POLMUX technique. MMW is communicated over 80-km SMF and 500-m wireless link and baseband PAM4 signal is transmitted over 50-km SMF and 500-m FSO link with the help of doublet lens scheme. The performance of PAM4 as well as OFDM format both are evaluated for wireless communication. Proper length of CP (7.6 μs) helps to suppress the ISI, dispersion, and multipath fading effect in wireless communication. The measured BER curve at various CP lengths is also analysed for optimizing CP length. Good bit error rate (10 −3 for OFDM, 10 −9 for PAM4), proper error vector magnitude (< 10.2%), clear constellation and eye diagram are achieved, which reveal the successful transmission of the presented architecture.