## 3 Overview of FB Approach for MR
### Critical Analysis of the FB Approach for MR  
Table 2 presents the review summary based on the discussions in Sections 3.1-3.4. The selected features, which are used in the literature to discriminate the modulation types, should be further sensitive in terms of discrimination and insensitive to noisy channels and SNR variations with reduced computational complexity. Spectral features have low complexity in terms of implementation. However, they are sensitive to additive noises. Higher-order statistics have high resistance to AWGN and multipath channels, and are further sensitive in discriminating between modulation schemes, such as M-PSK and M-QAM. Cyclostationary features have good resistance to noise at low SNR, but have high complexity and cannot discriminate a large set of modulation schemes. FFT features are  
robust at low SNR and further sensitive in discriminating M-FSK modulation schemes. The wavelet feature is suitable for discriminating modulation schemes at high SNR and requires many samples. The constellation feature is further sensitive to noise and requires high SNR to achieve good performance.  
\begin{table}
\begin{tabular}{|p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}|} \hline
**Reference(s)** & **KeyFeatures** & **Modulation Set** & **Advantages** & **Disadvantages** \\ \hline \multirow{4}{*}{[35]} & \multirow{4}{*}{Spectral features} & & 2 ASK, 4 ASK, & & & \\  & & 2 PSK, 4 PSK, & & & & \\  & & 2 PSK, 4 PSK, & & & & \\  & & 8 ASK, 8 PSK, & & & & \\  & & and 8 PSK & & & & \\ \hline \multirow{4}{*}{[38]} & \multirow{4}{*}{Spectral features} & & 2 ASK, 2 PSK, & & & & Small set digital modulation schemes \\  & & 2 PSK, 4 ASK, & & & & \\  & & 4 PSK, 16 QAM, & & & & \\  & & and 4 PSK & & & & \\ \hline \multirow{4}{*}{[43]} & \multirow{4}{*}{Spectral features} & & 2 ASK, 4 ASK, & & & & \\  & & 2 PSK, 2 PSK, & & & & \\  & & and QPSK & & & & \\ \hline \multirow{4}{*}{[12]} & \multirow{4}{*}{Sixth and fourth-order cumulants} & & & & & & High recognition at high SNR and increased multipath fading channel in real time & \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \hline \multirow{4}{*}{[48]} & \multirow{4}{*}{Second and fourth cumulants} & & 2 ASK, 4 ASK, & & & & Poor recognition of high-order modulation schemes (64 QAM and 256 QAM) & \\  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \hline \multirow{4}{*}{[51]} & \multirow{4}{*}{HOCs} & & BPSK, QPSK, 8-PSK, 64-QAM, and 256-QAM & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \hline \multirow{4}{*}{[54]} & \multirow{4}{*}{HOCs} & & BPSK, QPSK, 8-PSK, 16-QAM, and 256-QAM & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \hline \multirow{4}{*}{[76]} & \multirow{4}{*}{Cyclic frequency domain} & & BPSK, QPSK, 8-QAM, and 256-QAM & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \cline{2-6}  & & 4 PSK, 2 PSK, & & & & & \\ \hline \end{tabular}
\end{table}
Table 2: Summary of the advantages and disadvantages of key features used.