## 4 System Analysis and Experiment
### System Setup and Dual-Receiving Method
After that, the 9-dimensional feature extraction was completed on Android, and then the classification was  
Figure 6: System architecture diagram and man-made routes for flexible NLOS situations. completed through PC. The results were returned to the main anchor in time, which were s processed by the NLOS acoustic signal identification part based on the CTGSA-AFSA-DT model before. Finally, the system finished the indoor localization if necessary, so it benefit the indoor sensor systems or the cognitive IoT networks for orientation issues. Before the main process, the main anchor must recognize the beginning time of the initial localization loop. During these periods, all of the necessary permissions or accesses are required by the applications in the system. As for the advanced TDOA process, its core process is to implement the generalized cross-correlation (GCC) method and NLOS identification. Cross-platform interactive processing should also be added. The data are transferred into the PC module or the local server, and then can be displayed with the data visualization services through Tableau Software 10.4, HTML, or other ways. There are also many considerable ways to build up the LAN module, which will provide a reliable Wi-Fi environment for the system. The PC needs to make sure that there is no port number conflict before it begins to work. At this time, all mobile devices in the system need to be connected. As shown in Figure 6 above, the anchor module transmits data and interacts with the background module through the LAN module, and also interacts with the classification module when necessary, referring to the framework plans designed in [11; 22]. Judging by the reference anchor, the system does not need to implement strict clock synchronization and only needs to carry out skillful mathematical operation in [11]. Once the localization loop starts, each acoustic anchor can obtain the real-time position of the main anchor in the form of a constant coordinate value in our system. For the dual-receiving process, the main anchor will be used in batches during the instruction sending phase, and the following process requires sending at a fixed interval of 0.4 s. The protection interval also avoids the potential risks caused by reverberation. Each acoustic anchor receives the instructions broadcasted from the main anchor in a counterclockwise loop according to the order arranged in Figure 6. When the previous acoustic anchor does not comply with the RSS selection mechanism, the next acoustic anchor will temporarily be in a silent state. After the break, the system is supposed to continue the next loop. The main anchor is expected to receive the returning instructions and calculate the coordinates within sufficient protection intervals in addition to completing the signal broadcasting process. In order to better adapt to the dual-receiving acoustic anchor function, it is also necessary to add the recording function to ensure that the GCC-PHAT method can be completed to obtain the necessary chirp signal transmission delay difference for the system. It can also help the system to calculate the main anchor's coordinates in time. The following step will make the indoor localization system abandon no more than one NLOS acoustic signal according to the NLOS identification results and the NLOS situations coping mechanism from [22]. On the one hand, it should be emphasized that using RSS intensity alone is not reliable enough to fully identify NLOS acoustic signals. On the other hand, it is quite convincing that the total transmission path must contain at least three LOS acoustic signals after the RSS selection mechanism is adopted. Otherwise, the main process will not be promoted. In detail, as for dual-receiving acoustic anchors, there will be the following three issues according to the RSS selection mechanism on each acoustic anchor:  
1.