Abstract

In this paper, we propose an imperfect-quantized-feedback-based beamforming scheme for a generalized multiple-input single-output (MISO) free space optical (FSO) system over Gamma–Gamma fading channels with pointing error. It is well known that a feedback-based beamforming scheme aids channel adaptive signaling in wireless communication systems and provides large performance gain. If the feedback information is always decoded error free, then the beamforming technique reduces to a best transmit aperture selection scheme [termed error free optimal weighting scheme (EFOWS)]. However, due to a practically unguided environment, the feedback link is prone to error and leads to incorrect aperture selection, due to which diversity gain is lost. Therefore, a signal-to-noise ratio (SNR) adaptive error tolerant weighting (ETW) scheme is introduced and is optimized according to the SNR of the feedback link. In comparison to the considered arbitrarily fixed SNR-based ETW scheme, the proposed SNR adaptive ETW scheme provides significant performance gain (coding gain) almost equivalent to EFOWS. Closed-form expressions for the upper bound of the asymptotic average bit-error rate (BER) and the ergodic capacity of the proposed schemes are obtained with the help of order statistics. By minimizing the derived average BER, optimized transmit weights for the transmit apertures are achieved under erroneous feedback over Gamma–Gamma fading with pointing errors. Further, numerical results show that the proposed new error tolerant scheme outperforms the well-known repetition coding (referred to as the uniformly weighted scheme).

© 2017 Optical Society of America

On the capacity of MISO FSO systems over gamma-gamma and misalignment fading channels

Rubén Boluda-Ruiz, Antonio García-Zambrana, Beatriz Castillo-Vázquez, and Carmen Castillo-Vázquez
Opt. Express 23(17) 22371-22385 (2015)

1-bit feedback-based beamforming scheme for an uplink FSO-NOMA system with SIC errors

Prakriti Saxena and Manav R. Bhatnagar
Appl. Opt. 59(36) 11274-11291 (2020)

Polar-Coded MIMO FSO Communication System Over Gamma-Gamma Turbulence Channel With Spatially Correlated Fading

Jiafei Fang, Meihua Bi, Shilin Xiao, Guowei Yang, Ling Liu, Yunhao Zhang, and Weisheng Hu
J. Opt. Commun. Netw. 10(11) 915-923 (2018)

On the Performance of Multiplexing FSO MIMO Links in Log-Normal Fading With Pointing Errors

Mohammad Taghi Dabiri, Mohammad Javad Saber, and Seyed Mohammad Sajad Sadough
J. Opt. Commun. Netw. 9(11) 974-983 (2017)

Asymptotic error-rate analysis of FSO links using transmit laser selection over gamma-gamma atmospheric turbulence channels with pointing errors

Antonio García-Zambrana, Beatriz Castillo-Vázquez, and Carmen Castillo-Vázquez
Opt. Express 20(3) 2096-2109 (2012)