Spectral precoding for constant-envelope OFDM

Optimal training symbols for channel estimation in constant-envelope OFDM

“…Besides nonpartitioned SP-CE-OFDM, partitioned SP-CE-OFDM was developed in [2] to provide small spectral sidelobes while requiring less implementation complexity than nonpartitioned SP-CE-OFDM. For partitioned SP-CE-OFDM, Q and P are restricted to be both divisible by N and is constrained by @ W j @W g @ N j @N> where N and N j are two positive integers with N j ?…”

“…J is properly chosen as in [2], the corresponding signal can offer fast sidelobe decaying. For instance, J O -coded partitioned SP-CE-OFDM signal with O @ N 4 Q N 4 P exhibits power spectral sidelobes decaying asymptotically as i 5O 5 , where the proposed e J is designed to have the +q> p,th entry e j q>p given by e j p.o>p @ …”

“…The key idea is to modulate the OFDM waveform into the phase of a constant-envelope single-carrier signal which exhibits a unity peak-to-average power ratio while providing high power and spectral efficiencies. To further increase the spectral efficiency, the techniques of phase continuity [1] and spectral precoding [2]- [3] are incorporated into CE-OFDM. By adjusting the carrier phase for each signaling interval, phase continuity is maintained over signaling interval boundaries [1] and this endows the phasecontinuous CE-OFDM (PC-CE-OFDM) signal with power spectral sidelobes decaying as i 7 with i being the frequency in Hertz [2].…”

“…To further increase the spectral efficiency, the techniques of phase continuity [1] and spectral precoding [2]- [3] are incorporated into CE-OFDM. By adjusting the carrier phase for each signaling interval, phase continuity is maintained over signaling interval boundaries [1] and this endows the phasecontinuous CE-OFDM (PC-CE-OFDM) signal with power spectral sidelobes decaying as i 7 with i being the frequency in Hertz [2]. By introducing correlation or redundancy among input symbols with a fixed symbol-independent precoding matrix, two spectrally-precoded CE-OFDM (SP-CE-OFDM) signaling formats are respectively proposed in [2] and [3] to provide extremely small power spectral sidelobes decaying as i 5O 5 , with O an integer parameter.…”

“…Particularly, nonpartitioned SP-CE-OFDM format is given in [3] for long signaling intervals and unconstrained guard ratios. Partitioned SP-CE-OFDM format is developed in [2] for constrained guard ratios to permit spectral precoding within shorter signaling subintervals. Due to fast sidelobe decaying, these PC-CE-OFDM and SP-CE-OFDM signals exhibit high spectrum compactness.…”