Abstract:Motivated by the convergence of terrestrial cellular networks and satellite communications, this article considers an adaptation of offset quadrature phase shift keying (OQPSK), traditionally used with single-carrier waveforms in satellite systems, to discrete Fourier transform spread orthogonal frequency-division multiplexed (DFT-s-OFDM), as employed in the uplink of terrestrial systems. First, analytical signal-to-interference-plus-noise (SINR) expressions are derived for DFT-s-OFDM with frequency-domain spectral shaping (FDSS) carrying independently distributed pi/2-BPSK or QAM symbols and received with single-tap equalization, as in 5G. Next, a correlation-induced spectral shaping technique, termed repeated-and-offset QPSK (RO-QPSK), is introduced, relying solely on bit-level processing prior to conventional QPSK modulation. Specifically, the input bits are Manchester encoded (repeated and flipped) with an offset between the in-phase and quadrature branches, resulting in order-one OQPSK-like modulation. The induced correlation between consecutive QPSK symbols produces a Hann-shaped transmit spectrum yielding a peak-to-average power ratio (PAPR) on the order of 2 dB without explicit FDSS. At the receiver, the repetition structure is exploited through post-DFT-despreading symbol combining, and the corresponding end-to-end SINR with this transmitter-receiver pair is derived in closed form. Theoretical analysis and simulation results show that RO-QPSK provides performance gains in narrowband and moderately frequency-selective channels, as encountered in satellite communications, while remaining on par with conventional 5G uplink schemes in other scenarios. The combination of RO-QPSK with FDSS is also investigated, enabling further PAPR reduction while maintaining comparable link-level performance.
From: Renaud-Alexandre Pitaval [view email]
[v1]
Mon, 13 Oct 2025 14:15:58 UTC (579 KB)
[v2]
Sat, 4 Jul 2026 21:28:49 UTC (1,116 KB)
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