To enable differential detection of coincident, hard-limited, and reduced sidelobe QPSK type of signals, we introduce asymmetrical pulse shapes. This asymmetry in the I and Q baseband channels leads to coincident (unstaggered) QPSK system applications. We consider the bit error probability performance of these modulation schemes on a hard-limited channel in the presence of uplink and downlink additive Gaussian noise. It is found that the unstaggered QPSK modulation with the asymmetrical pulse has better bit error probability performance than QPSK and staggered QORC.
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