A Robust Design of TC-OQAM Schemes with Nonlinear Transmitters
- P. M. Montezuma; Dinis, R.; Amaral, F.;
"A Robust Design of TC-OQAM Schemes with Nonlinear Transmitters
IEEE Military Communications Conf. - MILCOM
Nonlinear operations are usually regarded as something undesirable that should be avoided in digital communication systems since they lead to performance degradation, namely spectral widening and decrease in power efficiency, for a given modulation. This paper shows that the nonlinear amplification can be viewed as an encoder for nonlinear OQPSK-type signals (Offset Quadrature Phase Shift Keying) when the pulse modulation is designed to take advantage from the nonlinear distortion. It is also shown that, by a proper pulse design in association with a pre-distortion scheme, we can take advantage of the OQPSK-type signals nature to obtain encoded TC-OQAM (Trellis Coded- Offset Quadrature Amplitude Modulation) schemes for grossly nonlinear amplifiers such as SSPAs (Solid State Power Amplifier). It is also shown that any transmission block formed by an encoder and a OQPSK modulator followed by a pre-distorter and a nonlinear amplifier can be viewed as a serial concatenated coded scheme with the inherent coding gains. This assures improved performances relatively to the linear transmission scheme, without significant complexity increase.