Design and evaluation of an IDMA cooperative relay free-space optical system

Abstract

In this paper, we illustrate our attempt in an effective method of free space optical (FSO) communications. Firstly, a pulse-position modulated (PPM) optical interleave-division multiple-access (OIDMA) system is designed. Secondly, to alleviate the degrading effects of atmospheric turbulence, cooperative relay technique is adopted by OIDMA for achieving spatial diversity and robust transmission performance. Thirdly, to study the convergence behavior of the proposed relay-assisted optical PPM-OIDMA system, extrinsic information transfer (EXIT) charts are analyzed. By deriving the trajectories of the exchanged extrinsic information from EXIT charts, the time of iterations required for convergence can be easily predicted. The effects of scintillation, thermal noise, background noise and multi-user interference have been taken into consideration.