A bandwidth-power efficient modulation scheme based on quaternary quasi-orthogonal sequences
Youhan Kim, Kyungwhoon Cheun, Kyeongcheol Yang · IEEE Communications Letters · 2003
A novel modulation scheme suitable for noncoherent demodulation based on quaternary quasi-orthogonal sequences is proposed. Compared to orthogonal modulation, the controlled quasi-orthogonality between the sequences allows significantly increased bandwidth efficiency with little or no degradation in power efficiency. A hardware efficient demodulator structure using fast Walsh transforms is also presented.