Research on simple QPSK demodulation method in hierarchically modulated T-DMB system with DQPSK-QPSK

We propose a simple QPSK demodulation method in hierarchically modulated T-DMB with DQPSK and QPSK. For the T-DMB system based on OFDM with DQPSK modulation, the data rate can be increased with hierarchical modulation by adding QPSK signal to existing DQPSK signal. The newly added QPSK can be restored with simple DQPSK signal estimation, which uses differential demodulation of DQPSK signal. We show the performance of a proposed method in mobile channel and static channels.