Because of the fixed allocated frequency spectrum (20 MHz), different modulation scheme requirements mean different bandwidth requirements.
The calculation of exact expressions for the SEP or BEP of a modulation scheme under fading means, in many cases,that the expressions for additive white Gaussian noise are weighted by the probability density function of the signal-to-noise ratio for a given fading.
The bit error rate (BER) of a communications system can directly be calculated from the modulation scheme and the achieved mean squared error (MSE).
Furthermore, the transmitted symbols s are assumed to be zero mean, non-Gaussian, independent, and identically distributed (i.i.d)., and they belong to the same linear modulation scheme (pluggable authentication module (PAM), quadrature amplitude modulation (QAM), or phase-shift keying (PSK)).
This means that, assuming that a modulation scheme carrying bits per symbol could be used in the case when continuous direct link was available, one would need to switch towards a modulation carrying bits per symbol (if the symbol duration was kept identical), for example, going from QPSK to 16-QAM when 2 RNs are available.
This means that, assuming that a modulation scheme carrying m bits per symbol could be used in the case when the continuous direct link is available, one would need to switch toward a modulation carrying 2m bits per symbol (if the symbol duration was kept identical).
(i) With a fixed modulation scheme, that is, is constant, depends only on the ratio between channel mean power of the relay-to-destination link and that of source-to-relay link.
(iii) The statistical properties including the mean, the variance, and higher order moments (HOM) of wavelet transforms are different from modulation scheme to another.
[25] Based on the extracted CWT instantaneous features (the mean, variance and central moments values), the authors have proposed an ANN to classify the modulation scheme into k-ASK, k-PSK, k-FSK, k-QAM, OOK,i and MSK.
Pulse position modulation (PPM) is a power-efficient modulation scheme to overcome this problem.
