This paper considers block-coded 8-phase-shift-keying (PSK) modulations for the unequal error protection (UEP) of information transmitted over Rayleigh-fading channels. Both conventional linear block codes and linear UEP (LUEP) codes are combined with a naturally labeled 8-PSK signal set, using the multilevel construction of Imai and Hirakawa (1977). Computer simulation results are presented showing that, over Rayleigh-fading channels, it is possible to improve the coding gain for the most significant bits with the use of binary LUEP codes as constituent codes, in comparison with using conventional binary linear codes alone.
Robert H. Morelos-Zaragoza, Tadao Kasami, Shu Lin, and Hideki Imai. "On Block-Coded Modulation Using Unequal Error Protection Codes Over Rayleigh-Fading Channels" Faculty Publications (1998): 1-4. doi:10.1109/26.655394