## 4 Simulation and Analysis
### Real Data Tests
Figure 13: The TC-OFDM receiver. (**a**) is the internal and external structure of the TC-OFDM receiver; and (**b**) is the communication between the positioning receiver and the mobile phone. respectively. For signals with lower signal power, these two algorithms can no longer track steadily, and even lose lock, so the improvement of signal tracking sensitivity of the proposed algorithm is significant for practical applications. Furthermore, we ran an actual test on the campus suing the test environment shown in Figure 15. We set up the base station on the roof of four buildings on our campus. Then we selected the 3 th floor of another building as test building to start our real test using the TC-OFDM receiver. The two-order FLL assisted three-order PLL and EKF algorithms are implemented in the receiver to compare with the proposed algorithm. In order to verify the better performance of the proposed algorithm for weak TC-OFDM signal, we selected 30 test points on the floor of the test building for positioning accuracy test. The receiver is placed at each test point for ten minutes, then we calculated the Root-mean-square error (RMSE) of the test points. The corresponding acquisition and positioning algorithms are utilized for the horizontal positioning. Since the positioning system uses a custom coordinate system for indoor positioning, the output positioning result is compared with the distance between the selected point and the origin of the corresponding floor. The RMSE of the positioning accuracy error results of the three algorithms between the selected point and the corresponding original point are shown in Figure 16, which shows the horizontal measurement accuracy results of three algorithms. The horizontal axis in the figure represents the sequence number corresponding to the selected 30 points. The vertical axis represents the calculation error of the final positioning result corresponding to each selected point. The positioning results of the blue, red, and black lines respectively represent the three different carrier loop algorithms: FLL&PLL, EKF, and MLE&KF. The final positioning results of using MLE&KF has the smallest fluctuations and the best positioning accuracy, which shows the superior performance of our algorithm compared to other algorithms. Also, these results is verified the effectiveness of the proposed algorithm in practical applications. The horizontal positioning accuracy is better than 3 m. The TC-OFDM receiver can be used to achieve accurate positioning in many indoor LBS applications, such as indoor mall pedestrian navigation and positioning and elderly care terminal. It can be seen that the positioning accuracy obtained by the proposed algorithm has smaller positioning error and higher positioning accuracy than the others for weak TC-OFDM signals. Figure 14: Actual test diagram of the tracking sensitivity between the three algorithms. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Signal Power (dBm)** & \(\mathbf{-126}\) & \(\mathbf{-127}\) & \(\mathbf{-128}\) & \(\mathbf{-129}\) & \(\mathbf{-130}\) & \(\mathbf{-131}\) & \(\mathbf{-132}\) & \(\mathbf{-133}\) & \(\mathbf{-134}\) & \(\mathbf{-135}\) & \(\mathbf{-136}\) \\ \hline the proposed algorithm & O\({}^{1}\) & O & O & O & O & O & O & O & O &