Abstract
Optical wireless communication is an energy-efficient and cost-effective solution for high-speed and highly-secure wireless connections. In this paper, we compare, discuss, and analyze three popular optical orthogonal frequency division multiplexing (OFDM) techniques, such as DC-biased optical OFDM (DCO-OFDM), asymmetrically-clipped optical OFDM (ACO-OFDM), and unipolar OFDM (U-OFDM), for underwater optical wireless communication systems. The peak power constraint, bandwidth limit of the light source, turbulence fading underwater channel, and the channel estimation error are taken into account. To maximize the achievable data propagation distance, we propose to optimize the modulation index that controls the signal magnitude, and a bitloading algorithm is applied. This optimization process trades off the clipping distortion caused by the peak power constraint and the signal to noise ratio (SNR). The SNR and clipping effects of the three compared OFDM techniques are modeled in this paper. From the numerical results, DCO-OFDM outperforms ACO- and U-OFDM when the transmitted bit rate is high compared to the channel bandwidth. Otherwise, U-OFDM can provide a longer propagation distance or requires less transmitted power.
Highlights
In recent years, underwater wireless communications (UWC) has attracted more and more research attention due to the increasing civilian and military demands [1,2,3]
Since light-emitting diode (LED) are used as transmitters in the underwater optical wireless communication systems, the band-limited LED dominates the overall bandwidth of the systems
The forward error control (FEC) codes need to be applied in a practical situation for a better bit error rate (BER) performance, which does not change the relative results among DCO, ACO, and U-orthogonal frequency division multiplexing (OFDM) obtained in this paper
Summary
Underwater wireless communications (UWC) has attracted more and more research attention due to the increasing civilian and military demands [1,2,3]. UOWC is an emerging technique for underwater systems with a high-speed transmission for moderate distance communication. A light-emitting diode (LED) working as a high power-efficient light source has attracted more attention recently and shows a big potential in underwater optical wireless communication systems [8,9,10,11]. Underwater optical OFDM has attracted much research attention recently since OFDM is a candidate technique to provide high-speed transmission. We compare, analyze, and discuss both the zero and peak power limit distortions for DCO-, ACO-, and U-OFDM in the applications of underwater optical wireless communication systems. A comparison of the state-of-the-art optical OFDM techniques for underwater optical wireless communication systems is discussed based on the propagation distance, BER, and data throughput.
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