Abstract: A transmission device includes an encoding circuit and a modulation circuit. The encoding circuit is configured to encode first and second data stream portions of a transmission data stream in accordance with first and second encoding protocols, respectively, convert each M bit of the encoded second data stream portion into a high-resolution value of N bit, and generate a baseband data stream including the encoded first data stream portion and the converted second data stream portion. The modulation circuit is configured to perform a 2N-level pulse amplitude modulation with respect to each N bit of the encoded first data stream portion in the baseband data stream and each N bit of the converted second data stream portion in the baseband data stream, to generate a transmission signal. M is an integer equal to or greater than 1 and N is an integer greater than M.