Underwater collaborative work between small mobile platforms (SMP) such as divers, litter submarine or AUV, requires a high data rate communication system which is compact, reliable, affordable and eye-safe. The high bandwidth of LED-based underwater wireless optical communication (UWOC) is an advantage. Artificial, emulated as well as simulated, turbid underwater channel has been studied recently, but no practical nature water. To fully meet the requirements of challenging turbid underwater channel scenarios for SMP, we demonstrated a green LED-based UWOC system up to a bandwidth of 3.4 MHz in a highlyturbid nature lake water. Through a contrast wireless optical communication (WOC) experiment in air, turbid water channel is observed to compensates the receiving signal amplitude attenuates after propagating a longer attenuation length due to multiple-scattered light caused diffusion, and thus to be more like a singleinput multi-output (SIMO) system. From our experimental observation, the SIMO channel model could be employed not only in turbulent UWOC, but also in highly turbid UWOC. Moreover, turbid water channel is observed a ''frequency selection'' effect, thus LED with lower threshold voltage at higher frequency would optimize bandwidth and link range, and a robust pre-code for interference cancellation would be a well-direct choice to constructing different UWOC system in highly turbid water for SMP. Our finding will provide a new reference complementing the current LED-based UWOC systems in realistic water environment.INDEX TERMS Underwater wireless optical communication, channel, turbid water, LED, wireless optical communication, single-input multi-output, visible light communication, small mobile platform.
I. INTRODUCTIONUnderwater collaborative work between underwater small mobile platforms (SMP) such as divers, litter submarines or AUV, requires real-time and high data rate link for voice, data or video communication. AUV needs high-speed transmitting link to efficiently collect large amounts of data stored by underwater sensors [1]. Due to the small load capacity and limited power supply, SMP require these high data rate communication system to be compact, simple, reliable and affordable. It is often impractical to make a optical fiber connection between these underwater SMP, the high bandwidth of UWOC is an advantage.The associate editor coordinating the review of this manuscript and approving it for publication was Qunbi Zhuge .