Transmission of SDH signals through future satellite channels using high-level modulation techniques

The authors discuss the possibility of transmitting synchronous digital hierarchy (SDH) signals through two-link nonlinear satellite channels. Transmitting such high bit rate signals through a standard 54 MHz or 36 MHz transponder bandwidth requires the use of high-level modulation schemes. The techniques and technologies needed to make the use of 16-ary quadrature amplitude modulation (QAM) and 64-ary QAM transmissions feasible for future satellite communication systems are examined. It is shown that it is possible to transmit a synchronous transport module-level 1 (STM-1) signal through a standard 54 or 36 MHz transponder bandwidth using 16-ary QAM or 64-ary QAM transmission, respectively, for the 6/4 GHz band. However, for higher frequency bands, due to high fade margins needed to achieve the high availability and performance for SDH systems, is not practical to transmit the STM-1 signal through such standard transponder bandwidths