Improving the Performance of Long Reach UOWC With Multiband DFT-Spread DMT

Negatively Biased Solar Cell Optical Receiver for Underwater Wireless Optical Communication System With Low Peak Average Power Ratio

“…Due to the presence of metallic impurities, lattice defects, etc. in the junction of the SC [21], a leakage current will be generated, and the resistance corresponding to the leakage current can be simulated by a resistor R SH . The R SH resistance is usually a few kΩ and is connected in parallel with a single diode D. The I-V properties of SC are stated as follows using the model in Figure 1(a):…”

“…In view of the above, underwater SLIPT for both EH and ID is a very interesting solution. However, due to the limited bandwidth of silicon SC devices [11] and the deterioration of bit-error-rate (BER) in natural waters [21], existing underwater SLIPT schemes with SC as detectors have a low communication rate and a high BER.…”

A Comprehensive Performance Comparison of DFT-S DMT and QAM-DMT in UOWC System in Different Water Environments

“…DFT-S outperforms conventional hard clipping by limiting the overshooting signal amplitude to a predefined level, which suffers from out-of-band spectral leakage and consequently distorts the received signal. Meanwhile, DFT-S could combat high frequency fading in a band-limited communication system and potentially improve the bit error rate (BER) performance of a long reach UOWC system [25]. In addition, turbidity, bubbles, and water flow may have significant impacts on the performance of UOWC systems, while little has been done for a comprehensive study on how these disturbance factors affect high-speed UOWC systems.…”

“…256 subcarriers carrying the paralleled 16-QAM symbols compose the payload, which can be expressed as [ ]T  denotes the transpose operation. Note that unlike our previous work[25], in order to avoid SNR degradation at fringe subcarriers after DFT-S, several zeros are padded at the edge of A , i.e., 0,X ,X ,...,X ,0,0] T N  A  . After applying an 2 N -point DFT 2 ( 260) N operation, the DFT-S symbols are expressed as  B = W A  , where the matrix Afterwards, five zeros are padded on the low frequency part near DC, which means the effective DFT-S symbols start from 6th to 265th subcarriers.…”

Underwater Wireless Optical Communication Based on DPSK Modulation and Silicon Photomultiplier

“…Given that UWOC systems suffer from severe signal power attenuation due to the absorption and scattering of light propagating through the water [1] [3], highly sensitive detector is required for compensating the transmission loss in the realization of the proposed DPSK UWOC system. At present, the avalanche photodiode (APD) is the most commonly used detector in IM-DD UWOC systems [1,5,6,[15][16][17][18], but the maximum useful gain of APD is inevitably limited by the excess noise generated by the multiplying process. Single-photon avalanche diode (SPAD) which is created by biasing the APD over its breakdown voltage can avoid excess noise [19].…”