## 4 Performance Assessment
### Experiment
#### 4.2.3 Experiment Results  
The experiment results of the proposed method are shown in Tables 2 and 3. The experiment results of the method using traditional MMSE adaptive equalization are shown in Table 4. For clear comparison, the BERs of the proposed method with 8 PSK mapping and the method using traditional adaptive equalization with BPSK mapping are listed in Table 5. Note that the symbol rate of the proposed method is the same as that of the reference method. The iteration of the turbo equalization terminates when the output MI of decoding is over 0.99. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Band (kHz)**} & \multicolumn{2}{c}{**After Equalization (Each Subband: 667 symbol/s)**} & \multicolumn{2}{c}{**After Decoding (Each Subband: 333 bit/s)**} \\ \cline{2-5}  & **SER** & **MI** & **BER** & **MI** \\ \hline
8–9 & 0/1400 & 1 & 0/700 & 1 \\ \hline
9–10 & 3/1400 & 0.997 & 0/700 & 1 \\ \hline
10–11 & 1/1400 & 0.999 & 0/700 & 1 \\ \hline
11–12 & 4/1400 & 0.989 & 0/700 & 1 \\ \hline
12–13 & 0/1400 & 0.999 & 0/700 & 1 \\ \hline
13–14 & 0/1400 & 1 & 0/700 & 1 \\ \hline
14–15 & 0/1400 & 1 & 0/700 & 1 \\ \hline
15–16 & 3/1400 & 0.998 & 0/700 & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results of the proposed method with BPSK mapping. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Band (kHz)**} & \multicolumn{2}{c}{**After Equalization (Each Subband: 667 symbol/s)**} & \multicolumn{2}{c}{**After Decoding (Each Subband: 1000 bit/s)**} \\ \cline{2-7}  & **SER** & **MI** & **BER** & **MI** \\ \hline
8–9 & 411/1400 & 39/1400 & 0.739 & 0.971 & 18/2100 & 0/2100 & 0.931 & 0.998 \\ \hline
9–10 & 144/1400 & 8/1400 & 0.90  
Through comparing the results in Tables 2-5, several observations can be obtained. Firstly, the SER of the method using traditional MMSE adaptive equalization is equal to that of the first equalization of the proposed method. Secondly, the proposed method realizes error-free transmission only through one time equalization and decoding for BPSK mapping, while two times equalization and decoding is needed to reach performance convergence for 8 PSK mapping. Thirdly, when the same mapping pattern is used, although the proposed method achieves better performance after convergence, the information bit rate has been cut down to half of that in the method using traditional MMSE equalization. Lastly, as shown in Table 5, when a different mapping pattern is used, the proposed method with 8 PSK mapping can achieve better communication performance at a higher bit rate than the method using traditional MMSE adaptive equalization with BPSK mapping. All experiment results are consistent with the simulation analysis. To reflect experiment results visually, Figures 10 and 11 show the scatterplots of the proposed method. Two types of scatterplots are shown in Figures 10 and 11. One type indicates the estimated symbols after equalization, and the other reflects the mean of symbols that is computed using the a posteriori LLR of the decoder. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Band (kHz)**} & **SER of BPSK Mapping (Each** & **SER of 8 PSK Mapping (Each** \\  & **Subband: 667 symbol/s, 667 bit/s)** & **Subband: 667 symbol/s, 2000 bit/s)** \\ \hline
8–9 & 0/1400 & 411/1400 \\ \hline
9–10 & 3/1400 & 144/1400 \\ \hline
10–11 & 1/1400 & 240/1400 \\ \hline
11–12 & 4/1400 & 496/1400 \\ \hline
12–13 & 0/1400 & 390/1400 \\ \hline
13–14 & 0/1400 & 206/1400 \\ \hline
14–15 & 0/1400 & 205/1400 \\ \hline
15–16 & 3/1400 & 338/1400 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of the method using traditional MMSE adaptive equalization.