# Study of Global Navigation Satellite System Receivers' Accuracy for Unmanned Vehicles
## 1 Introduction
The use of the frequency resource by the codes is presented in Figure 1. The PRN codes' power spectrum is shown in Figure 2 and their parameters are described in Table 1, which should be taken into account in the antenna design. Figure 1: PRN codes in GPS system. The addition of new navigation codes leads to a reduction in position errors. The application of dual-band GNSS signal reception is a significant technological step towards next-level accuracy and reliability in location tracking, as the standard point positioning service error is higher than 2.5 m and this is insufficiently accurate for intelligent transport systems [17; 18] as the standard lane width is equal to 3 m. Dual-band reception significantly increases position accuracy to the sub-meter level with the ability to correct ionospheric distortions, but even this technology cannot overcome the main disadvantage of global positioning systems, which is defined by the low update rate of up to 10 Hz. In this case, the integration of a dual-band GNSS receiver and Inertial Measurement Unit (IMU) could cover the land vehicle requirements, as the GNSS system could eliminate IMU error accumulation [19; 20] while the IMU system could increase the position update rate up to 1 kHz. GNSS system accuracy is critical for IMU/GNSS systems as most of the time the position and velocity, as measurement inputs, are used to compensate for IMU errors [21]. The covariance matrix from GNSS data processing is also passed to the fusion algorithm [22]. If it is suggested that the update rate of a GNSS system is 1 Hz and the latest generation accelerometer zero-rate offset is equal to 20 mg [23], the accumulated IMU displacement error \(\Delta\) for this period of time is equal to 10 cm according to Equation (1) [24]. \[\Delta=\int\int_{0}^{t}{\it adt^{2}} \tag{1}\] \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Frequency**} & \multirow{2}{*}{**PRN**} & **Code** & **Code** & **Modulation** & **Bandwidth** & **Data** \\  & & **Code** & **Length** & **Baud Rate** & **Scheme** & **[MHz]** & **Baud Rate** \\ \hline \multirow{6}{*}{L1} & \multirow{2}{*}{C/A} & \multirow{2}{*}{1023} & \multirow{2}{*}{1.023} & \multirow{2}{*}{BPSK [1] (1)} & \multirow{2}{*}{2.046} & \multirow{2}{*}{50/50} \\ \cline{3-4} \cline{6-6}  & & & & & & \\ \cline{2-6}  & & P & -7 days & 10.23 & BPSK [10] & 20.46 & 50/50 \\ \cline{2-6}  & & M & - & 5.115 & BOC [2] (10.5) & 30.69 & - \\ \cline{2-6}  & & L1C\({}_{\text{D}}\) [3] & 10,230 & 1.023 & BOC (1.1) & 4.092 & 100/50 \\ \cline{2-6}  & & L1C\({}_{\text{P}}\) [3] & 102,301,800 & 1.023 & BOC (1.1) & 4.092 & - \\ \hline \multirow{6}{*}{L2} & \multirow{2}{*}{L2C} & \multirow{2}{*}{P} & \multirow{2}{*}{\(\sim\)7 days} & \multirow{2}{*}{10.23} & \multirow{2}{*}{BPSK (10)} & \multirow{2}{*}{20.46} & \multirow{2}{*}{50/50} \\ \cline{3-4} \cline{6-6}  & & M & 10,230 & 1.023 & BPSK (1) & 2.046 & 50/25 \\ \cline{2-6}  & & L & 767,250 & & & & - \\ \cline{2-6}  & & M & & 5.115 & BOC (10.5) & 30.69 & - \\ \hline \multirow{6}{*}{L5} & \multirow{2}{*}{L5I [4]} & \multirow{2}{*}{10,230.10} & \multirow{2}{*}{10.23} & \multirow{2}{*}{BPSK (10)} & \multirow{2}{*}{20.46} & \multirow{2}{*}{100/50} \\ \cline{1-1} \cline{3-4} \cline{6-6}  & & L5Q [4] & 10,230.20 & 10.23 & BPSK (10) & 20.46 & - \\ \hline \hline \end{tabular}  
* BPSK (\(n\))—Binary Phased Shift Keying with chip rate equal to \(n\times\) 1.023 MHz, 2 BOC (\(n\),\(n\))—Binary Offset Carrier modulation with \(n\) being a 1.023 MHz square wave and \(m\) being a 1.023 MHz pseudo-random code [14].
* Overlay and ranging codes for GPS LIC code [15], 4 CB PRN codes [16].  
\end{table} 
Table 1: Frequency bands and GNSS signal description. Figure 2: Power spectrum of GPS codes.