GNSS signal codes | P-code C/A-code A-code L1C L2C L5 E1 E5a E5b B1 B2 B3
This page covers GNSS signal codes and their use.It covers various GNSS signal codes viz. P-code, C/A-code, A-code, L1C, L2C, L5, E1, E5a, E5b, B1, B2, B3 etc.
Introduction: The full form of GNSS is Global Navigation Satellite System. It is network of satellites managed by ground stations. It provides information to GNSS receivers or users worldwide related to positioning, navigation and timing. The satellites use different codes to modulate RF carrier wave. These codes are received at the receivers which help receivers to determine type of satellite. These codes carry precise timing and satellite positioning information.
GNSS signal codes
Following table mentions various GNSS signal codes used for decoding useful GNSS informations from satellites.
| GNSS signal codes | Description |
|---|---|
| C/A-code (Coarse/Acquisition code) | This is primary code used by GPS satellites. It is transmitted using L1 frequency. C/A code has very low chipping rate. |
| P-code (Precision code) | This code is used by GPS satellites. It is highly precise and encrypted code. It is used by military. It is transmitted on L1 and L2 frequencies. It has higher chipping rate. Hence it is more difficult to acquire and track compare to C/A code. It is used to achieve more accurate positioning and timing informations. |
| A-code (Authorized access code) | It is encrypted version of C/A code available to be used by authorized users and military professionals. It offers higher accuracy than C/A code. |
| L1C and L2C | L1C code is transmitted on L1 frequency where as L2C code is transmitted on L2 frequency. Both of these codes offer greater interoperability between GPS system and other other GNSS systems (Galileo, BeiDou). These codes offer improved resistance to interference as well as jamming. |
| L5 code | This is new code which is used by various GNSS systems such as GPS, Galileo and QZSS. This code is transmitted on L5 frequency using BOC (Binary Offset Carrier) modulation. L5 ranges from 1176 MHz to 1188 MHz. L5 code supports high power and bandwidth. It offers improvement in accuracy and reliability for high precision positioning applications. |
| E1, E5a, E5b | These modern GNSS codes are used by European Galileo satellite system. E1 signal code is transmitted on L1 frequency. E1 structure is same as L1C code. L1 signal carries pilot, data and multiplexed pilot plus data components. Data component of L1 carries various informations such as navigation, ranging etc. E5a and E5b codes are transmitted on L5 frequency. E5a code structure is same as GPS L5 code. Both E5a and E5b signal carry pilot and data fields. E5a carries ionospheric data, ranging information etc. E5b carries search and rescue signals, ranging etc. |
| B1, B2, B3 | These codes are used by BeiDou system which are interoperable with other GNSS systems. B1 signal code uses L1 frequency, B2 uses L2 frequency and B3 uses 1268.52 MHz frequency. |
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