Rate 5/6 Trellis-Coded 8-PSK

Some new short constraint length codes are described for satellite channels which are constant-envelope and which have spectral and energy efficiencies intermediate to other recent coded techniques, namely
r = 2/3
coded 8-PSK and
r = 3/4
coded 16-PSK. We use two intervals of 8-PSK transmission to form a modulation base for
r = 5/6
trellis codes. A particularly attractive design is an eight-state code, producing 6.2 dB gain on the Gaussian channel over uncoded 8-PSK, yet sacrificing only 16 percent in spectral efficiency.