Layered symmetric three-dimensional constellation mapping modulation method and system

The invention discloses a layered symmetric three-dimensional constellation mapping modulation method, which comprises the following steps of: dividing geometric distribution of constellation points in a three-dimensional space into different layers according to Z-axis numerical values, and under the condition of a fixed minimum Euclidean distance, designing corresponding constellation point two-dimensional distribution on each layer in sequence by taking maximization of a constellation diagram CFM index as a target; obtaining a layered symmetric three-dimensional constellation diagram; according to different transmitting powers required by constellation points, dividing imported data into four different energy levels, so that the data is converted into a distribution form after probability shaping calculation from an original binary bit stream, and finally mapping into space coordinates containing information in a three-dimensional space. According to the method, the structure of the constellation diagram is