# BDCOA: Wavefront Aberration Compensation Using Improved Swarm Intelligence for FSO Communication
###### Abstract
The failure of concentrating over the phase compensation was subjected to signal distortion, which increased the BER. [PERSON] et al. [23] developed the Adagrad and Staged SPGD algorithm (AS-SPGD) for enhancing convergence in fiber coupling for FSO. The acceleration of SPGD was obtained by integrating the [PERSON]'s adaptive gain approach of Adagrad SPGD to obtain wavefront tip-tilt aberration compensation based on FSM. Further, the local convergence of SPGD was enhanced by using the Staged SPGD approach. An optimum control signal was required to be selected to further minimize the WA. [PERSON] et al. [24] evaluated the FSO's performance by using the M-ary Phase Shift Keying (MPSK), Binary Phase Shift Keying (BPSK), On-Off Keying (OOK), and M-ary Quadrature Amplitude Modulation (M-QAM) modulation approaches in transmitters and avalanche photodiode (APD) in receivers. The examination of FSO broadcasting was considered the normal (turbulence free) channel model, with the atmospherically turbulent gamma channel model used for the condition of weak/medium and strong air turbulence over air channels. However, the small routing error affected the performance of the FSO in atmospheric turbulence. In general, the small routing error was the misalignment of the route of transmitted optical beam corresponding to the intended receiver. [PERSON] et al. [25] presented the combination of adaptive moment estimation (Adam) from deep learning and SPGD, AdamSPGD, to ensure an effective wavefront correction. The development of AdamSPGD was used to enhance the correction speed and robustness of SLAO. In this approach, huge Zernike polynomial modes were utilized for precisely denoting the WAs. An inappropriate control signal in the DM of SLAO caused signal distortion during communication, thereby increasing the BER. [PERSON] and [PERSON] [26] developed an adaptive threshold return-to-zero on-off keying based on self-pilot tone, namely RZ-OOK decision for FSO communication. The RZ-OOK had impulse series features in the spectrum and these impulses were used as transmitted signal's pilot tones for transferring the Channel State Information (CSI). Further, an Adaptive Threshold Decision (ATD) was obtained by allocating optimum weight factors in the obtained CSI signal to enhance the CSI signal's power. The signal distortion was aroused in RZ-OOK when the WA compensation was not effectively performed in FSO. [PERSON] et al. [27] developed the hybrid algorithm for enhancing coupling efficiency and mixing efficiency by improving the performance indicators of a coherent communication system. In this hybrid approach, the combination of SA and SPGD algorithms were used for error correction. The hybrid approach employed rapid convergence speed of course correction from SA along with SPGD for modifying the residual error. This process minimized the probability of local optimization in the SPGD algorithm and ensured reliability in correction. In optical communication, the phase compensation was required to be obtained for further enhancing the performances. [PERSON] et al. [28] presented the AMFSPGD for enhancing the correction of WA. The spot array was obtained by using a multiplexed computer-generated hologram. Accordingly, the consistent Strehl Ratio (SR) was acquired to provide multi-feedback, which suggested highly extensive optimized information. The search gradients were effectively adjusted while obtaining an optimal value with effective probability based on the integration of global and local gradient in AMF-SPGD. The usage of hard max recognition was subjected to make corrections unstable in FSO. [PERSON] and [PERSON] [29] presented the OBAFS approach for correcting the WA in SLAO system. The utilization of OBAFS was used to obtain an optimum control signal for DM's actuators. Next, the discovery of control parameters was used to compensate the WA and to enhance the FSO communication. Effective exploration and exploitation were required to be obtained in order to search for appropriate control signals.