Comparative analysis of MIMO-based FSO and MIMO-based MGDM communications

Abstract

The ever-growing need for high data rate, bandwidth efficiency, reliability, less complexity, and less power consumption in the communication systems is on the increase. Modern techniques have to be developed and put in place to meet these requirements. In the last few years, free space optical (FSO) communication systems have attracted considerable research efforts mainly due to their inherent potential transmission capacity, much higher than that offered by radio transmission technologies. However, despite of great potential of FSO communication, its performance is limited by the adverse effects (viz., absorption, scattering, and turbulence) of the atmospheric channel. Different studies on weather conditions and techniques employed to mitigate their effect are studied. On other hand, a MMF network may constitute the backbone network that feeds fixed-wired services (e.g. voice telephony) as well as wireless services (e.g. IEEE 802.x) throughout the building. The large bandwidth makes MMF a very attractive medium for low-cost broadband in building networks, in which several independent sets of services are integrated. In addition, research has shown that compared to conventional single-input single-output (SISO) systems, multiple-input multiple-output (MIMO) can actually increase the data rate of a communication system, without actually requiring more transmit power or bandwidth. In this paper, we develop a comparison between MIMO over multimode fiber (MMF) using MGDM and MIMO based FSO links. The achievable performance improvements, including received power levels, bit error rate (BER), and quality factor (Q-factor) are presented. Numerical results are obtained for single-input single-output (SISO) as well as for multiple-input multiple-output (MIMO) configurations. Simulation results show that MMF outperforms FSO links in terms of max Q-factor, minimum BER, and eye diagram. Seen that the dependence of the FSO system performance on the weather conditions is one of the most significant FSO limitations, we analyze the performance of FSO under clear, haze, and fog conditions using Q-factor, bit error rate (BER), etc., at varied distances. From the results, it can be concluded that as we move from clear weather conditions to haze and fog weather conditions, Q-factor of the received signal decreases.