Performance of trellis coded 256 QAM super-multicarrier modem using VLSI´s for SDH interface outage-free digital microwave radio

This paper describes the performance of an outage free SDH (synchronous digital hierarchy) interface 256 QAM modem. An outage free DMR (digital microwave radio) is achieved by a high coding gain trellis coded SPORT QAM and super multicarrier modem. A new frame format and its associated circuits connect the outage free modem to the SDH interface. The newly designed VLSI´s are key devices for developing the modem. As an overall modem performance, BER (bit error rate) characteristics and equipment signatures are presented. A coding gain of 4.7dB (at a BER of 10^-4) is obtained using SPORT 256 QAM and Viterbi decoding. This coding gain is realized by trellis coding as well as by increasing of transmission rate. Roll-off factor is decreased to maintain the same frequency occupation and modulation level as ordinary SDH 256 QAM modem