Schematic of the encoding scheme in the transmission station: user data equal to decimal number 200 is converted to 242 in base-9 number system. Linear combinations of two Zernike modes, say Z6 and Z11, each with multiple values of ϕRMS (say ±0.5 or 0 radian), are used to map to different digits of base-9 number using the lookup Table 1 and the information is sent to a phase modulating device. The device uses the digital data to generate corresponding wavefronts in a beam derived from an incident laser beam. Each wavefront representing a certain base-9 digit is transmitted in a sequential manner through free space in three consecutive time slots. Colorbar shows the false colormap in radian of the phase profiles.