A comparison study of low bit rate DE-QPSK and TCM 8-PSK fullydigital demodulators over a land mobile satellite link

摘要

The synchronization and detection techniques used to overcome theRician channel impairments are described. The acquisition and bit errorrate (BER) performances of this modem have been evaluated by computersimulation over an AWGN (additive white Gaussian noise) and a Ricianfaded channel, and compared with a DE-QPSK demodulator with similararchitecture. In an AWGN channel the TCM (trellis coded modulation)8-PSK system is found superior to the DE-QPSK. In terms of the overallBER over realistic satellite channel conditions the two systems showcomparable results because of the greater susceptibility of TCM schemesto carrier synchronization errors. However, the outage of the coded8-PSK system is superior to the DE-QPSK one. The errors of the coded8-PSK are characterized by short periods of high error rates with longergaps of very low error rates. In contrast, the errors of the DP-QPSKsystem are distributed uniformly and occur more frequently