## 2 Materials and Methods
### Universal GNSS Channel Validation
#### 2.2.5 GNSS Test Scenarios  
To cover all the above signal particularities and to demonstrate the proposed universal channel, the resulting test scenarios are summarized in Table 4.  
One should bear in mind that GPS L2 CM is first acquired without L2 CL. Because of their continuous time multiplexing, the L2 CM spreading code (_i.e._, transmitted at 511.5 kchip/s) correlator spacing is limited to \(\pm\)0.24 chip in order to avoid being polluted by L2 CL. Also, with GLONASS being transmitted at 511 kchip/s, the 60 Msample/s channel design does not allow for a correlator spacing greater than \(\pm\)31 samples, _i.e._, \(\pm\)0.26 chip. On the other hand, GPS L5 at 10.23 Michip/s suffers from the opposite problem: the channel sampling rate cannot achieve better than \(\pm\)1 sample, _i.e._, \(\pm\)0.17 chip. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **GNSS** & **RF (MHz)** & **Signal** & **Primary Code** & **Modulation** & \(\pm\)\(\delta\) **(Chip)** & **Particularity** \\ \hline \multirow{2}{*}{1} & GPS & 1575.42 & L1C & 10 ms; 10,230 chips & \begin{tabular}{c} 1: sBOC(1,1); Q: \\ TM-sBOC (6, 1, 4/3) \\ \end{tabular} & \begin{tabular}{c} 0.48\(\rightarrow\)0.05; \\ 0.48\(\rightarrow\)0.05 \\ \end{tabular} & L1 band; GPS; MBOC \\ \hline \multirow{2}{*}{2} & GPS & 1227.60 & L2C & \begin{tabular}{c} L2 CM: 20 ms; 10,230 chips; L2 CL: 1.5 s; \\ 76/,250 chips \\ \end{tabular} & \begin{tabular}{c} 0.24\(\rightarrow\)0.05; \\ off–same as L2 CM \\ \end{tabular} & \begin{tabular}{c} L2 band; LFSR logic; \\ TMBPSK \\ \end{tabular} \\ \hline \multirow{2}{*}{3} & GPS & 1176.45 & L5 & 1 ms; 10,230 chips & \begin{tabular}{c} QPSK (10) \\ \end{tabular} & \begin{tabular}{c} 0.50\(\rightarrow\)0.17; \\ 0.50\(\rightarrow\)0.17 \\ \end{tabular} & L5 band; QPSK; Code rate \\ \hline \multirow{2}{*}{4} & Galileo & 1575.42 & E1 B\&C & 4 ms; 4092 chips & \begin{tabular}{c} CsBOC (6, 1, 1/11, \(\pm\)) \\ \end{tabular} & \begin{tabular}{c} 0.48\(\rightarrow\)0.05; \\ 0.48\(\rightarrow\)0.05 \\ \end{tabular} & \begin{tabular}{c} Galileo; MBOC; Code \\ period \\ \end{tabular} \\ \hline \multirow{2}{*}{5} & GLONASS & 1602.00 & L1 OF & 1 ms; 511 chips & BPSK(–4) & 0.26\(\rightarrow\)0.05 & \
\begin{tabular}{c} A RF in L1; GLONASS; \\ FDMA \\ \end{tabular} \\ \hline \multirow{2}{*}{6} & BeiDou & 1561.098 & B1-I & 1 ms; 2046 chips & BPSK(2) & 0.48\(\rightarrow\)0.03 &
\begin{tabular}{c} A RF in L1; BeiDou; \\ Code length \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Proposed Universal Channel Test Scenarios. Unfortunately, cBOC modulation could not be formally tested without the publically undisclosed Galileo E1A and E6 spreading codes. The same applies to modernized signals that are not yet available in space, such as GPS L1C TMBOC. The test scenarios are further described in the following paragraphs. Galileo E1 B&C  
CBOC is an implementation of the MBOC spectrum, involving the two (6\(\times\) and 1\(\times\)) sub-carriers as in GPS L1 Cp, but with different, yet constant amplitudes. The current implementation being based on integrations over multiples of 1 ms, a total of four partial integrations are accumulated (coherently or not) to match the full 4 ms long primary spreading code before proceeding to the next cell of the acquisition span, encompassing 4092 chips and 16 Doppler 667 Hz bins. During acquisition, only the BOC(1,1) sub-carrier is used, with a \(\pm\)28 samples correlator spacing. This early simplification can be used since the second sub-carrier only bears a tenth of the signal power, which can be neglected. Once synchronized with a BOC(1,1) modulation, the full CBOC replica signal may be generated locally with a reduced correlator spacing of \(\pm\)3 samples. The 12-bit un-encoded preamble may be used to synchronize onto the message frame of the data component. On the other hand, the pilot component bears a 25-bit secondary code. GPS L1C modernized signal involves BOC on the data component and TMBOC on the pilot.