# Low-Computational Extended Orthogonal Matched Filter Structure for Multiuser Detection
## 4 Performance Evaluation and Discussion
### Results and Discussion
#### 4.2.2 Cqet
The BER performance is worse than that in scenario 1 because the deterioration of the array antenna characteristics is significant, which is due to the close arrival angles of the desired signal and the interfering signal. The conventional EOMF has better BER performance than the other number of \begin{table}
\begin{tabular}{c c} \hline \hline
**Number of Desired Users** & **BER (10–3)** \\ \hline
1 (Conventional EOMF) & 1.16 \\
2 (Proposed structure) & 2.59 \\
4 (Proposed structure) & 3.41 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Bit error ratio (BER) result of scenario 1 when the number of total users is eight and DIR = \(-50\) dB. Figure 6: BER result of scenario 1. The number of total users is 30. The blue, red, and green plots show the results when the number of desired users among total users is one (the conventional EOMF case), two and 15 (the proposed structure case), respectively. desired user cases in the low DIR condition. The conventional EOMF has better BER performance than two and four desired users' cases in the low DIR condition. However, its BER is approximately \(10^{-1}\), which is not significantly different from that of the proposed structure when the number of desired users increases. In other words, the adaptive array antenna cannot sufficiently suppress the interference signal by null steering, and the replica generation in an OMF does not function sufficiently in all three cases. On the other hand, the BER is below \(10^{-3}\) in all three cases under the condition that the DIR is \(-10\) dB or higher. The reason is that the replica generation in an OMF works well even if the interference signal cannot be sufficiently suppressed by the adaptive array antenna since the interference signal energy is small originally. Then, Figure 8 shows the BER result for scenario 2; the number of total users is 30. The array antenna characteristics are greatly deteriorated due to the close arrival angles of the desired signal and the interference signal and the lack of antenna flexibility. Hence, both the conventional EOMF and the proposed structure cannot remove interferences that are up to \(\text{DIR}=-20\) dB for the same reason as in the case that the number of total users is eight. Under the condition of \(\text{DIR}=-10\) dB, good BER performance is shown in the order of the conventional EOMF, two desired users, and 15 desired users. However, the BER is less than \(10^{-4}\) in all three cases. Figure 7: BER result of scenario 2. The number of total users is eight. The blue, red, and green plots show the results when the number of desired users among total users is one (the conventional EOMF case), two and four (the proposed structure case), respectively. From the above, it is considered that the proposed system has interference cancellation performance that is close to that of the conventional EOMF, although the performance deteriorates compared to the conventional EOMF as the number of desired users increases. In addition, the proposed structure is considered to have sufficient BER performance, assuming a situation in which short packets are sent to each other, such as in a wireless sensor network.