A pragmatic coding scheme for transmission of 155 Mbit/s SDH and 140 Mbit/s PDH signals over 72 MHz transponders

This paper presents a pragmatic coded 8-PSK scheme for transmission of up to 155.52 Mbit/s over existing 72 MHz satellite transponders. The target IF-loopback performance of an integrated 155 Mbit/s modem/codec in development is a BER=10^-9 at an Eb/No=8.0 dB. It is believed this outperforms other known approaches compatible with 72 MHz transponders. The inner code is a rate 8/9 six-dimensional trellis code with 64 states. The outer code is a rate 235/255 Reed-Solomon code. A novel bit error despreader and a symbol interleaver with a depth of 15 are used to match the inner and outer code. The soft-decision trellis decoder is built around a single standard CMOS Viterbi decoder chip operating at 42 Mbit/s. The codec performance has been verified using software simulation of the channel and modem in combination with a hardware decoder. The codec as implemented achieves a BER=10^-9 at an Eb/No=7.5 dB with an ideal 8-PSK modem and a linear AWGN channel