gpsL2CCodes

Generate CM and CL codes for GPS L2C

Since R2025a

Syntax

[CM,CL] = gpsL2CCodes(PRNID)

Description

[CM,CL] = gpsL2CCodes(PRNID) generates civil-moderate (CM) and civil-long (CL) codes, as specified in the modernized Global Positioning System (GPS) L2 civil (L2C) standard IS-GPS-200 sections 3.2.1.4 and 3.2.1.5 [1], for the satellite pseudo-random noise (PRN) indices specified in PRNID.

For details on how to generate a GPS L2C waveform, see Generate GPS L2C Waveform.

Examples

Generate GPS L2C Codes

Generate the CM and CL codes for a GPS L2C signal.

Specify the PRN IDs for the GPS satellites.

PRNID = [1 11 180]; 

Generate the CM and CL codes for the set PRN IDs.

[CM,CL] = gpsL2CCodes(PRNID);

Check the sizes of generated CM and CL code matrices. Note that each contains the same number of rows as the number of specified PRN IDs.

size(CM)

ans = 1×2

       10230           3

size(CL)

ans = 1×2

      767250           3

Input Arguments

PRNID — GPS satellite PRN index

integer in range [1, 63] or [159, 210] | vector of integers in range [1, 63] or [159, 210]

GPS satellite PRN index, specified as one of these options.

• Integer in the range [1, 63] or [159, 210] — Use this option to input a PRN index for a single satellite.

• Vector of integers in the range [1, 63] or [159, 210] — Use this option to input PRN indices for multiple satellites.

For details on how to generate these CM and CL codes for a specific PRNID, refer to these tables in GPS L2C standard IS-GPS-200N [1].

• PRN ID in the range [1, 63] — Table 3-IIa and Table 3-IIb for the code phase assignments of L2C CM and CL codes.

• PRN ID in the range [159, 210] — Table 6-II for additional code phase assignments of L2C CM and CL codes.

Data Types: double | uint8

Output Arguments

CM — Civil-moderate code

binary-valued vector | binary-valued matrix

Civil-moderate code, returned as a binary-valued vector or matrix. The number of rows is equal to the code period of 10230, and the number of columns is equal to the number of elements in PRNID.

CM codes are 20 milliseconds long with a chip rate of 511.5 kilochips per second (kcps). CM is a logical array with dimensions 10230-by-length(PRNID).

For details on how to generate a GPS L2C waveform, see Generate GPS L2C Waveform.

Data Types: logical

CL — Civil-long code

binary-valued vector | binary-valued matrix

Civil-long code, returned as a binary-valued vector or matrix. The number of rows is equal to the code period of 767250, and the number of columns is equal to the number of elements in PRNID.

CL codes are 1.5 seconds long with a chip rate of 511.5 kcps. CL is a logical array with dimensions 767250-by-length(PRNID).

For details on how to generate a GPS L2C waveform, see Generate GPS L2C Waveform.

Data Types: logical

More About

Generate GPS L2C Waveform

You can generate an L2C waveform by following these steps.

1. Generate an L2-CM and an L2-CL code.

2. XOR the civil navigation (CNAV) data with only the L2-CM code.

3. Multiplex the XORed CNAV and L2-CM data bit-by-bit with L2-CL code.

4. Because L2-CM and L2-CL each consists of 511.5 kilo chips per seconds, the multiplexed stream of bits consists of 1.023e6 chips per second

5. For the multiplexed stream generated in point 4, map bit 0 to +1 and bit 1 to –1. Place this waveform on the Q-branch.

6. Generate P-code using gpsPCode.

7. XOR the incoming legacy navigation (LNAV) data with the P-code. Ensure that the sample rates of LNAV data and P-code match.

8. For the XORed LNAV and P-code data, map bit 0 to +1/sqrt(2) and bit 1 to –1/sqrt(2) and then place this waveform on the I-branch.

   The resultant IQ waveform is the baseband GPS L2C waveform.

Alternatively, use gpsWaveformGenerator object to directly create a L2C waveform.

References

[1] IS-GPS-200N. "NAVSTAR GPS Space Segment/Navigation User Segment Interfaces." GPS Enterprise Space & Missile Systems Center (SMC) - LAAFB, August, 2022.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2025a