Design of an Improved QPSK Modulation Technique in Wireless Communication Systems

This paper proposes an improved QPSK modulation scheme, called as pi/6-QPSK, which is an improvement of existing pi/4-QPSK modulation technique in the wireless communication system in case of phase transition. The key aspects of pi/6-QPSK are to consider three constellations apart by pi/6 degree successively as well as incorporating a new constellation selection mode depending on input dibits. In order to facilitate these two key aspects, a set of new encoding rules has been designed. Finally, our pi/6-QPSK provides the maximum and minimum phase transitions of +/- 90 degrees and +/- 30 degrees, respectively with reducing envelope variation. Simulation results of MATLAB Simulink confirm that the signal spectral performance of our proposed pi/6-QPSK is better than that of conventional pi/4-QPSK modulation scheme. On the other hand, the relative phase transition of pi/6-QPSK is reasonably reduced comparing to the other conventional QPSK modulation schemes.