Angular MIMO for Underwater Wireless Optical Communications: Link Modeling and Tracking

Angular imaging multiple-input--multiple-output (A-MIMO) is investigated for short-range, high-speed underwater wireless optical communications (UWOCs) where, unlike conventional MIMO (C-MIMO), data are transmitted in an angle rather than space. In this approach, the strict requirements of on-axis alignment and fixed channel length relaxed. This technique also allows simpler estimation relative misalignment between transmitter receiver from received image. For first time, we derive a comprehensive model A-MIMO link by taking into account misalignment, background noise, as well seawater absorption scattering. Power distributions at modeled arrival signal on lens its position focal plane detector. We further propose tracked (TA-MIMO) system that maintains two ends link, which distribution residual tracking error calculated. The UWOC capacity then estimated buoyed-to-fixed (B2F) (which has dominant angular misalignments) mobile-to-fixed (M2F) off-axis misalignment) communication scenarios. Numerical results indicate B2F scenario, sensitive to misalignments; however, TA-MIMO outperforms C-MIMO. case M2F links, greatly C-MIMO when misalignments present. work serves design guide determine selection A-MIMO, TA-MIMO, or receivers depending conditions particular application.