An Efficient Method for Offset Mitigation in Free-Space Optical Systems

Channel estimation is a key feature for free space optical (FSO) wireless communication systems which are required for a high QoS and high data rate system. Aiming at the problem of FSO wireless channel estimation, this paper proposes an implicit sequence channel estimation scheme to eliminate dc offset, and studies the key factors affecting the system performance. The optimal power allocation factor is derived based on the maximum SNR criterion. The system performance parameters such as the bit error rate (BER), mean square error (MSE), and computational complexity are evaluated. The results show that under the same dc bias condition, the MSE is estimated to decrease significantly after using the method of this paper. With the increase of dc offset d, the system error rate is significantly reduced and more approaching d = 0 (i.e., no dc offset). The proposed algorithm effectively mitigates the dc offset impact on the system and the BER is significantly improved while the MSE is reduced to 50% of the traditional state-of-the-art method. The proposed work can provide a technical solution to the FSO system and give support to technological development.