Patent ID: 7277498

Claim:
A communication method using a multi-level modulation system comprising the steps of: on a transmission side, coding M-bit data into N-bit data (where M≦N); determining, for every N-bit data, whether or not to interleave said N-bit data, based on a transmission condition in a propagation path between said transmission side and a receiving side; and modulating said N-bit data into symbols of a plurality of bits each, and transmitting said symbols; and on said receiving side, demodulating said received symbols into said N-bit data; selectively rearranging (deinterleaving) said demodulated N-bit data; and decoding said N-bit data into said M-bit data, wherein each bit of the N-bit data has a determined level of importance at the time of decoding and each symbol has a different resistance to error, wherein when communication is made between the N-bit data and the symbols on the transmission side and the receiving side and when the quality of the propagation path between the transmission side and the receiving side is equal to or less than a certain value, a rule is applied such that large-weight bits are assigned to symbols of high resistance to error, and wherein when communication is made between the N-bit data and the symbols on the transmission side and the receiving side and when the quality of the propagation path is larger than the certain value, the respective bits of the N-bit data are equally or randomly assigned to symbols of the range from high resistance to low resistance to error.