## 2 Literature Review Methodology
### Development of the Review Protocol
#### 2.2.3 Systematic Approach Used in Extracting and Analyzing Studies
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ref.** & **Bandwidth** & **Tx-Rx Distance** & **System** & **Subcarr.** & **Modulation** & **CP** \\ \hline
[35] & — & — & OFDM & — & FSK & — \\ \hline
[37] & 6 kHz & 5 km & OFDM & 256 & PSK, QAM & 64 \\ \hline
[38] & — & — & OFDM & — & — & — \\ \hline
[39] & 8 kHz & 5 km & OFDM & 1024 & PSK, QAM & 400 \\ \hline
[40] & 6 kHz & 0.3 km to 1.5 km & OTFS & 32 & PSK & — \\ \hline
[41] & — & 5 to 355 cm & OFDM & — & — & — \\ \hline
[42] & 5 kHz & 0.82 km & OFDM & 200 & — & — \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Characteristics of adaptive modulation techniques in MC-UWA communication. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Ref.** & **ML/DL Technique** & **Optimizer** & **Training Examples** \\ \hline
[49] & SCNet & Adam & Simulated Data \\ \hline
[50] & OAE-EEKNN & GD \& Adam & Measured Data \\ \hline
[51] & RNN \& CNN & Adam & Measured Data \\ \hline
[52] & SCL & Adam & Simulated and Measured Data \\ \hline
[53] & ResNet & Adam & Simulated and Measured Data \\ \hline
[54] & CNN with Ensemble Learning & — & Simulated Data \\ \hline
[55] & DCN & — & Simulated and Measured Data \\ \hline
[56] & SVM & — & Simulated and Measured Data \\ \hline
[46] & SqueezeNet and SENet & — & Simulated and Measured Data \\ \hline
[47] & Hybrid & Adam & Measured Data \\ \hline
[48] & TSTR & Adam & Measured Data (from [26] \\ \hline
[44] & NAS & MSGD & Simulated and Measured Data \\ \hline
[9] & 2D ResNet \& CNN & — & Measured Data \\ \hline
[45] & Hybrid & — & Simulated and Measured Data \\ \hline \hline \end{tabular}
\end{table} 
Table 16: Overview of ML/DL-based modulation recognition. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Ref.** & **Bandwidth** & **Tx-Rx Distance** & **Modulations Considered** \\ \hline
[49] & 1000 symbols/s & 1.5 km & PSK, QAM, SSB, FM, PAM, FSK \\ \hline
[50] & 10 kHz & 1 km & FSK, PSK, QAM, DSSS, OFDM \\ \hline
[51] & 4 kHz & 1 km & PSK, FSK, OFDM \\ \hline
[52] & — & 3, 6, 12, 60 m & PSK, FSK \\ \hline
[53] & 4 kHz & 1 km & PSK, FSK, OFDM \\ \hline
[54] & — & 45 m & PSK, FSK, QAM \\ \hline
[55] & — & 3 km, 5 km & PSK, QAM \\ \hline
[56] & 100 kHz & 6 m & FSK \\ \hline
[46] & — & 10, 500, 1000 m & PSK, FSK, DSSS, OFDM \\ \hline
[47] & — & 7 m, 1 km & PSK, FSK, QAM, DSSS, OFDM \\ \hline
[48] & — & — & PSK, QAM, FSK \\ \hline
[44] & 1 kHz & 100 m to 3 km & LFM, FSK, PSK, DSSS, OFDM \\ \hline
[9] & 3 kHz, 10 kHz & 1.22 km & FSK, PSK, CW, DSSS, LFM, OFDM \\ \hline
[45] & 31.25 kHz & 5 km, 1.25 km & PSK, QAM \\ \hline \hline \end{tabular}
\end{table} 
Table 17: Characteristics of ML/DL-based modulation recognition techniques. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Ref.** & **Training Loss** & **Complexity** & **Throughput or Equivalent** & **Gain in BER** \\ \hline
[35] & Not Applicable & Less & Near ideal & Near ideal \\ \hline
[37] & Actor and Critic Loss & — & 4\% higher & Better than others \\ \hline
[38] & — & — & \(>98\%\) (Accuracy) & Substantial \\ \hline
[39] & Not Given (MSE) & High & Higher than others & Better \\ \hline
[40] & CE & Higher & 4\% higher & Kept at 0.001 throughout \\ \hline
[41] & Not Applicable & — & 3.648\% (RSSI) & 32\% \\ \hline
[42] & Not Applicable & — & 14.8\% higher & Stable \\ \hline \hline \end{tabular}
\end{table} 
Table 15: Comparison of adaptive modulation techniques in MC-UWA communication.