Modulation Schemes for Wireless Access

Four modulation schemes, namely minimum shift keying (MSK), Gaussian minimum shift keying (GMSK), multiamplitude minimum shift keying (MAMSK) and π/4 differential quadrature phase shift keying (π/4-QPSK) are described and their applicability to wireless access is discussed in the paper. Low complexity receiver structures based on differential detection are analysed to estimate the performance of the modulation schemes in the additive Gaussian noise and the Rayleigh and Rice envelope fast fading channel. The bandwidth efficiency is calculated to evaluate the modulation schemes. The results show that the MAMSK scheme gives the greatest bandwidth efficiency, but its performance in the Rayleigh channel is rather poor. In contrast, the MSK scheme is less bandwidth efficient, but it is more resistant to Rayleigh fading. The performance of π/4-QPSK signal is considerably improved by appropriate prefiltering