Capacity evaluation of MIMO-OFDM Free Space Optical communication system

Free Space Optical (FSO) communication is an emerging technology to provide high bandwidth, secure and high quality communication. In this work we have determined the capacity of the Free Space Optical communication system with Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) technique under weak atmospheric turbulence conditions. To model the weak turbulence condition of the atmosphere lognormal channel model is used throughout the work. The capacity of MIMO-OFDM FSO is evaluated in the presence of Inter Symbol Interference (ISI) and is compared with MIMO FSO with ISI. The capacity of MIMO-OFDM FSO system increases in comparison to MIMO in the presence of ISI. It is found that the effect of ISI is mitigated by using OFDM and the capacity is enhanced. Since MIMO uses spatial divervity to mitigate the fading caused by turbulence hence the capacity of both MIMO-OFDM FSO and MIMO FSO also increases as the number of receiving antennas is increased.