A Performance of Coded Modulation Based on Optimal Faster-than-Nyquist Signals

This paper proposes novel coded modulation schemes based on LDPC codes and optimal partial response (or Faster-than-Nyquist) signals. In these schemes coded bits are mapped into the points of QPSK constellation and the spectrum bandwidth (hence, the spectral efficiency) is widely handled by choosing the optimal finite impulse response (pulse) of the shaping filter. The shaping filter allows the intentional introduction of inter-symbol interference (ISI). The pulse optimization was based on the criterion of the minimal bandwidth comprising 99% of the signal power. It also included additional constraints of the ISI level and the signal peak-to average power ratio. By simulation, we have shown that for the channel with additive white Gaussian noise the transition from conventional RRC-pulses to optimal finite pulses within the proposed coded modulation provide a reduction of bandwidth and energy consumption.