# A Robust Timing Synchronization Algorithm Based on PSSS for LTE-V2X
## 5 Results and Discussion
### Hardware-in-the-Loop Simulation  
This paper establishes a hardware-in-the-loop simulation platform to further validate the performance of the improved algorithm, offering the following advantages:  
1. Efficient testing: The hardware-in-the-loop simulation overcomes the time-consuming nature and limited scope of field testing, allowing for a comprehensive analysis of  
Figure 11: Performance of different symbol timing synchronization algorithms in AWGN channels when \(\varepsilon\) = 1. Figure 10: Performance of different symbol timing synchronization algorithms in AWGN channels when \(\varepsilon\) = 0.5.  
communication performance in various channel conditions within a shorter timeframe. It provides valuable insights and corresponding deployment suggestions. 2. Accuracy and reliability: In comparison to software simulation, the hardware-in-the-loop simulation platform utilizes an actual signal source as the transmitter, ensuring more accurate and reliable results. 3. Versatility: The channel emulator supports the import of channel models, making use of models obtained by various research institutes. This versatility enhances the adaptability of the simulation platform. Figure 12 illustrates the hardware-in-the-loop simulation platform, comprising the SMBV100A vector signal generation source from Rhodes and Schwartz as the transmitter, the Vertex channel emulator from Spirent and the receiver consisting of the Universal Software Radio Peripheral (USRP) B210 and a Personal Computer (PC). During the hardware-in-the-loop simulation, the configured LTE-V2X signal is fed into the SMBV100A and continuously transmitted to the Vertex. Simultaneously, the USRP B210 receives the LTE-V2X signal passing through the channel emulator. The PC processes the collected LTE-V2X signal from the USRP, facilitating a performance comparison of symbol time synchronization under different channel conditions. Due to the power limitation of the signal entering the channel emulator, the transmitter configuration and the LTE-V2X signal we generated, shown in Table 2, comply with 3 GPP specifications except for transmission power. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline Carrier Frequency & 5.915 GHz \\ Transmit Power & \(-\)40 dBm \\ Sub-carrier Spacing & 15 kHz \\ Transmission Bandwidth & 20 M (100 RBs) \\ FFT Size & 2048 \\ Sample Rate & 30.72 M \\ LTE-V2X Subframe & SC-FDMA \\ Cyclic Prefix Type & Normal \\ SLID & 0 \\ Number of Subframes & 1000 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Transmitter configuration. Figure 12: Hardware-in-the-loop simulation platform diagram. (**a**) System structure diagram. (**b**) Device connection diagram. The channel models we used are shown in Table 3 below, which are defined in 3 GPP specification TR 36.885 [27]. Considering the diversity of V2X propagation channels, this paper selects high-speed line-of-sight (LOS) and urban non-line-of-sight (NLOS) models. It considers three different speeds of 0 km/h, 50 km/h and 120 km/h, as Table 3 shows below. Figure 13 illustrates the performance of the improved algorithm and the traditional algorithms under different vehicle velocities in a Highway-LOS scenario. In Figure 13a, the velocity is 0 km/h, and in Figure 13b, the velocity is 120 km/h. From these simulation results, the following conclusions can be made:  
1. The improved algorithm enhances PSSS detection performance when the velocity is 0 km/h in this scenario. The improved algorithm can maintain a CDR close to 0.9 at \(-\)14 dB, the SSA achieves a CDR of 0.9 at \(-\)12 dB, and the M = 2 BCCA and CCA reach a CDR of 0.9 at \(-\)10 dB. Therefore, the SSA is approximately 2 dB worse than the improved algorithm, and the M = 2 BCCA and CCA are about 4 dB worse than the improved algorithm. 2. The improved algorithm also enhances PSSS detection performance when the velocity is 120 km/h. The improved algorithm can maintain a CDR close to 0.9 at \(-\)10 dB.