مرکز منطقه ای اطلاع رسانی علوم و فناوری Journal of Information Systems and Telecommunication (JIST) 2322-1437 1 1 2013 3 20 A New Upper Bound for Free Space Optical Channel Capacity Using a Simple Mathematical in Equality A New Upper Bound for Free Space Optical Channel Capacity Using a Simple Mathematical in Equality 1 10 10.7508/jist.2013.01.001 en Arezu Rezazadeh Ferdowsi University of Mashhad Ghosheh Abed Hodtani Ferdowsi University of Mashhad 2014 10 20 In this paper, by using a simple mathematical inequality, we derive a $ new upper bound fkr the capacity of$ free space optical channel in coherent case. Then, by applying general fading distribution, we obtain an upper bound for mutual information in non-coherent case. Finally, we derive the corresponding optimal input distributions for both coherent and non-coherent cases, compare the results with previous works numerically and illustrate that our results subsume some of previous results in special cases. http://jist.ir/ar/Article/Download/14801