Principles of Digital Communication and Coding
Principles of Digital Communication and Coding
A novel approach to modeling of OQPSK-type digital transmission over nonlinear radio channels
IEEE Journal on Selected Areas in Communications
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The ENCAP- 4N (ENCoded Amplitude and Phase- 4N), related with a vast class of OQPSK (Offset Quadri-PhaseShift Keying) type signals, can be advantageous when it is important to achieve good tradeoffs between spectral efficiency and envelope fluctuations when a nonlinear amplification is employed. This paper presents a simplified representation of FQPSK (Feher-Patented Quadrature-Phase Shift Keying), showing also the potential improvement in power efficiency, without sacrifice of spectral compactness. Usually, the coding rule for ENCAP- 4N format is based on the complex envelope decomposition in pulses with bit duration T, directly related with the 4N generating functions set. In this paper, it is proposed a new interpretation based in this signal format that results in a coding rule, based on a complex envelope description as function of pulses with duration 2T. The signal, in accordance with the foregoing coding rule, can be viewed as a trellis coded modulation with 22N+2 states and pulses shapes.