A hybrid FSO/RF communication system with DSP for long haul communication

Abstract

Due to the exceptional growth in mobile data traffic, emerging mobile access networks need a lot of bandwidth and robust network architecture as a crucial solution in delivering a high capacity for support in the future. The proposed work presents a detailed investigation of hybrid free space optical/radio frequency (FSO/RF) communication system at 320 Gbps channel capacity. A digital signal processing (DSP) compensation mechanism is used in the receiver system along with circular polarization division multiplexed (CPDM) 256-quadrature amplitude modulation (QAM) to improve system performance. Constellation diagrams have been used to measure the effectiveness of the system. The constellation diagrams which are considered for investigating the proposal are, (a) without DSP (digital signal processing), (b) with DSP without normalization and low pass filtering, (c) with DSP without carrier phase estimation (CPE) and frequency offset estimation (FOE) and (d) with DSP using normalization, low pass filtering, CPE and FOE, in FSO/RF system under clear weather, rain and haze. Effects of presence and absence of DSP in the coherent receiver have been investigated. Results show the improvement in system performance with least error vector magnitude (EVM), when DSP incorporated FSO/RF system is implemented using normalization, low pass filtering, CPE, FOE with perfect placements of symbols.