Bit-stream-arranged weighted modulation scheme for frequency selective fading channels

This paper proposes a bit-stream-arranged weighted modulation scheme to improve the voice quality in frequency selective fading channels. The proposed modulation scheme employs an input bit stream arrangement method which changes the bit stream order for important bits so that they do not adjoin each other over time and a mapping method which controls the amplitude of modulation signals according to the importance of the bits. Computer simulations clarify that the proposed bit-stream-arranged weighted modulation scheme shows a noise reduction of 7 dB in voice signal compared with the conventional π/4 shift DQPSK modulation scheme