Thesis (Ph.D.) - Cairo University - Faculty of Engineering - Department of Electronics and Communications

This study focuses on some practical aspects that enable the free space optical communication system over orbital angular momentum modes, specifically the receiver structure and modes selection.Three contributions are introduced.The first one is the space filtering approach where the partial-pattern receiver for transmitted orbital angular momentum (OAM) multi-modes is explored.The modes are included in the Laguerre-Gaussian beam propagating under non-Kolmogorov weak-to-moderate turbulence.The partial pattern effect is studied on the achievable capacity and the error rates.Controlled parameters are derived as well.The second one is a simple iterative algorithm to determine the optimum (in terms of the system capacity) set of multiple orbital angular momentum (OAM) modes.The modes are propagating over Free space optical (FSO) communication beam for a given receiver radius.The algorithm is derived using generalized channel efficiency matrix. The new algorithm has complexity reduction in the order of (2^N ̆ )/N ^̆2 where N ̆is the number of available modes. Based on the above, a third contribution includes a deep learning detection mechanism for Multiple-Input-Single-Output (MISO) application is proposed and proved superior performance

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