Channel estimation and error correction for UWOC system with vertical non-line-of-sight channel
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Channel estimation and error correction for UWOC system with vertical non-line-of-sight channel B. Priyalakshmi1 • K. Mahalakshmi2
Ó Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Recently, underwater wireless optical communication (UWOC) system has placed more attention towards increasing data rate, high accuracy, higher bandwidth and providing highly secured transmission. Generally, light propagation in underwater medium is disturbed due to some degrading effects such as turbulence, scattering and absorption which will degrade the performance. Therefore, channel estimation is essential and need to adapt suitable correction techniques that compensate the errors due to those effects. In this work, channel estimation and error correction technique are proposed for the UWOC system with vertical non-line-of-sight channel based on MIMO-OFDM approach. Initially, input sequence error is eliminated by HVD Turbo coding method and error rectified signal is modulated with M-ary OAM-PPM modulation technique. Modulated signal is transmitted through Vertical NLOS channel. During transmission, the signal undergoes scattering, absorption and channel fading. In receiver side, channel characteristics are estimated by invariant embedding method. Finally, estimated signal is demodulated and decoded by same techniques. MATLAB environment is used to implement the proposed work. Resultant performances like channel capacity, BER, SNR, data rate, receiving power and MSE for different water types like pure sea water, ocean water, costal water and turbid water are compared and results are examined. Keywords Underwater wireless optical communication (UWOC) Vertical non-line-of-sight M-ary Orbital angular momentum Invariant embedding and horizontal vertical diagonal (HVD) turbo coding
1 Introduction UWOC system is getting more interest over the previous decades due to its need of providing high speed communication [1]. UWOC refers to the transmission of data in untraced water medium over optical carriers. In traditional water communications, underwater communication is a dominant method because of the low attenuation of an acoustic wave present in water [2]. The underwater communication has the issues like lower bandwidth, Doppler
& B. Priyalakshmi [email protected] K. Mahalakshmi [email protected] 1
Anna University, Chennai, Tamil Nadu, India
2
Department of CSE, KIT-Kalaignarkarunanidhi Institute of Technology, Coimbatore, Tamil Nadu, India
spread, multipath propagation and multipath propagation. In seawater, the radio frequency is strongly attenuated by maximizing frequencies. Hence, it only helps short distance communication. The suspended particles and water absorption create scattering which affects optical wireless communication, but it has higher bandwidth efficiency [3]. The UWOC characteristics are well-suited to lower range of underwater communication system due to absorption, turbulence and scattering effects in the underwater opt
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