Optical wireless communication for real time swimmers feedback: A review

Underwater optical wireless communication applications include robot communication, data monitoring and collection and control applications (SCADA). Underwater optical wireless communication using visible light is used because of the high data rate compared to acoustic technology and low path attenuation compared to radio frequency (RF) technology. The blue-green wavelength has minimum attenuation for absorption and scattering. One application for optical wireless communications is real time swimmers feedback. This system requires short range communication over 1 m between sensors mounted at the swimmer´s wrist and a receiver on his/her goggles. The link was sometimes line of sight (LOS) and sometimes non line of sight (NLOS). Air bubbles generated from a swimmer causes additional link attenuation. Pool lighting may cause interference both above and below the water. The final unit should be low cost, have low power consumption and small size to reduce drag. This paper reviews technology used to give real time feedback to a swimmer during swimming. This new technology should help swimmers improve their performance during training. Different optical wireless systems using LEDs as a light source are presented. The authors investigated in the previous work the effect of air bubbles and they designed, implemented and tested an optical wireless communication system based on light emitting diode (LED) and integrated detector preamplifier (IDP). Both the position and the orientation of the transmitter and the receiver change during the swimmer´s actions. Simulation results for the line of sight (LOS) communication link and the non line of sight (NLOS) with the effect of air bubbles were used to evaluate the effect on the underwater optical signal. Link budgets were calculated for different light sources. This paper reviews research in underwater optical wireless communication system using LEDs as a light source. The applications to swimming monitoring is presented.