Performance Improvement of IM-DD Free Space Optical CDMA (Attenuated by Strong Atmospheric Turbulence) with Maximal Ratio Combining

In this paper a completely new analytical approach to the performance evaluation of turbulence induced fading on free space optical (FSO) CDMA communication system is presented. The current analysis develops an expression of average SINR of FSO CDMA system using switched inversed keyed(SIK) correlator transmitter in presence of turbulence induced fading and multiple access interference(MAI). Link performance is evaluated in terms of average bit error rate which is numerically computed. The performance improvement over atmospheric turbulence fading channel is proposed by means of applying diversity using rake correlation receiver and output of rake receiver is combined using maximal ratio combining (MRC) scheme. It has been shown in numerical evaluation that BER gets improved in diversity reception than only line of sight (LOS) reception. Numerical result also shows that, applying path diversity mitigates multiple access interference with less received power. Finally, the performance is evaluated using two different sequences (Gold and Kasami ) and from performance evaluation, it is shown that KASAMI sequence exhibits less bit error performance than GOLD sequence.