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`Home » Systems » GPS » Modernization » New Civil Signals
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`New Civil Signals
`
`On this page:
`L2C
`L5
`L1C
`Codeless Transition
`
`On other pages:
`CNAV Message
`
`A major focus of the GPS modernization program is the addition of new navigation signals
`to the satellite constellation.
`
`The government is in the process of fielding three new signals designed for civilian use:
`L2C, L5, and L1C. The legacy civil signal, called L1 C/A or C/A at L1, will continue
`broadcasting, for a total of four civil GPS signals. Users must upgrade their equipment to
`benefit from the new signals.
`
`The new civil signals are phasing in incrementally as the Air Force launches new GPS
`satellites to replace older ones. Most of the new signals will be of limited use until they
`are broadcast from 18 to 24 satellites.
`
`Second Civil Signal: L2C
`
`Status
`
`Pre-operational signal with message set "healthy"
`Broadcasting from 19 GPS satellites (as of October 17, 2017)
`Began launching in 2005 with GPS Block IIR-M
`Available on 24 GPS satellites ~2021 (as of May 2017)
`
`Features
`
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`1227.60 MHz
`
`Radio Navigation Satellite Services (RNSS) radio band
`Modern signal design (CNAV), including multiple message types and forward error
`correction
`Bi-Phase Shift Key (BPSK) modulation
`Includes dedicated channel for codeless tracking
`
`VIEW FULL TECHNICAL SPECIFICATIONS
`
`L2C is the second civilian GPS signal, designed specifically to meet commercial needs.
`
`Its name refers to the radio frequency used by the signal (1227 MHz, or L2) and the fact
`that it is for civilian use. There are also two military signals at the L2 frequency.
`
`When combined with L1 C/A in a dual-frequency receiver, L2C enables ionospheric
`correction, a technique that boosts accuracy. Civilians with dual-frequency GPS receivers
`enjoy the same accuracy as the military (or better).
`
`For professional users with existing dual-frequency operations, L2C
`enables faster signal acquisition, enhanced reliability, and greater
`operating range.
`
`L2C broadcasts at a higher effective power than the legacy L1 C/A
`signal, making it easier to receive under trees and even indoors.
`
`The Commerce Department estimates L2C could generate $5.8 billion
`in economic productivity benefits through 2030.
`
`The first GPS satellite featuring L2C launched in 2005. Every GPS
`satellite fielded since then has included an L2C transmitter.
`
`In April 2014, the Air Force began broadcasting civil navigation (CNAV) messages on the
`L2C signal. However, L2C remains pre-operational and should be employed at the user's
`own risk until it is declared operational.
`
`Related Links:
`
`CNAV Message
`Jul 2006: Article on Economic Benefits of L2C (commerce.gov)
`Jan 2006: Public Media Forum on L2C Availability
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`Third Civil Signal: L5
`
`Status
`
`Pre-operational signal with message set "unhealthy" until sufficient monitoring capability
`established
`Broadcasting from 12 GPS satellites (as of October 17, 2017)
`Began launching in 2010 with GPS Block IIF
`Available on 24 GPS satellites ~2024 (as of May 2017)
`
`Features
`
`1176.45 MHz
`
`
`
`Highly protected Aeronautical Radio Navigation Services (ARNS) radio band
`Higher transmitted power than L1 C/A or L2C
`Greater bandwidth for improved jam resistance
`Modern signal design (CNAV), including multiple message types and forward error
`correction
`Bi-Phase Shift Key (BPSK) modulation
`Includes dedicated channel for codeless tracking
`
`VIEW FULL TECHNICAL SPECIFICATIONS
`
`L5 is the third civilian GPS signal, designed to meet demanding requirements for safety-
`of-life transportation and other high-performance applications.
`
`Its name refers to the U.S. designation for the radio frequency used by the signal (1176
`MHz).
`
`L5 is broadcast in a radio band reserved exclusively for aviation safety services. It
`features higher power, greater bandwidth, and an advanced signal design.
`
`Future aircraft will use L5 in combination with L1 C/A to improve accuracy (via
`ionospheric correction) and robustness (via signal redundancy).
`
`In addition to enhancing safety, L5 use will increase capacity and fuel efficiency within
`U.S. airspace, railroads, waterways, and highways.
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`Beyond transportation, L5 will provide users worldwide with the
`most advanced civilian GPS signal. When used in combination
`with L1 C/A and L2C, L5 will provide a highly robust service.
`Through a technique called trilaning, the use of three GPS
`frequencies may enable sub-meter accuracy without
`augmentations, and very long range operations with
`augmentations.
`
`In 2009, the Air Force successfully broadcast an experimental L5
`signal on the GPS IIR-20(M) satellite. The first GPS IIF satellite
`with a full L5 transmitter launched in May 2010.
`
`In April 2014, the Air Force began broadcasting civil navigation (CNAV) messages on the L5
`signal. However, L5 remains pre-operational and should be employed at the user's own
`risk until it is declared operational.
`
`Related Links:
`
`CNAV Message
`Jun 2010: News Release on First L5 Transmission from GPS IIF Satellite (af.mil)
`Apr 2009: News Release on L5 Demo Signal from GPS IIR-20(M) Satellite (af.mil)
`
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`Fourth Civil Signal: L1C
`
`Status
`
`Begins launching in 2018 with GPS III (as of May 2017)
`Available on 24 GPS satellites in late 2020s
`
`Features
`
`1575.42 MHz
`
`Aeronautical Radio Navigation Services (ARNS) radio band
`Designed for international GNSS interoperability
`Modern signal design (CNAV-2), including forward error correction
`Multiplexed Binary Offset Carrier (MBOC) modulation
`
`VIEW FULL TECHNICAL SPECIFICATIONS
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`L1C is the fourth civilian GPS signal, designed to enable interoperability between GPS and
`international satellite navigation systems.
`
`Its name refers to the radio frequency used by the signal (1575 MHz, or L1) and the fact
`that it is for civilian use. There are also two military signals at L1, as well as the legacy
`C/A signal. L1C should not be confused with L1 C/A.
`
`L1C features a Multiplexed Binary Offset Carrier (MBOC)
`modulation scheme that enables international cooperation
`while protecting U.S. national security interests. The design
`will improve mobile GPS reception in cities and other
`challenging environments.
`
`The United States and Europe originally developed L1C as a
`common civil signal for GPS and Galileo. Japan's Quasi-
`Zenith Satellite System (QZSS) and China's BeiDou system
`are also adopting L1C-like signals.
`
`The United States will launch its first L1C signal with GPS III. L1C will broadcast at the
`same frequency as the original L1 C/A signal, which will be retained for backwards
`compatibility.
`
`Related Links:
`
`Jan 2013: Joint UK-U.S. Statement Regarding GPS Intellectual Property
`Jul 2010: U.S.-EU Joint Statement on Combined GPS-Galileo Performance
`Jul 2007: U.S., EU Announce Final Design for GPS-Galileo Civil Signal
`International Cooperation
`
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`Codeless/Semi-Codeless Transition Plan
`
`Once L2C and L5 are fully operational, their features will obviate the need for codeless or
`semi-codeless GPS receivers, which many GPS professionals use today to attain very high
`accuracy. Such receivers work by exploiting characteristics of the encrypted military P(Y)
`signal at the L2 frequency to achieve dual-frequency capability.
`
`The U.S. government encourages all users of codeless/semi-codeless GPS technology to
`start their planning for transition to the modernized civil signals.
`LEARN MORE
`
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