Multilevel Modulation and Channel Codes for Terrestrial FSO links

The basic aim of this work is to enhance the performance of the existing terrestrial FSO links by introducing a well-suited modulation and channel coding scheme. Selecting an appropriate modulation and coding scheme for the FSO systems requires thorough knowledge of the behavior of the FSO systems under different conditions and the objectives that need to be achieved out of the modulation mechanism. Since modulation for the FSO systems are primarily targeted at achieving higher average optical power, so that the penetration of the light waves through the adverse weather conditions can be increased. Thus, the power efficiency of the scheme remains the deciding criteria in the selection of the modulation format. The choice of the modulation and coding format has to be based on measurements and simulation of the performance of FSO systems under nonfavourable atmospheric conditions. An effort is also being made to simulate the atmospheric free space optical channel to get more insight into the problem