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The Galileo Commercial Service: Current Status and Prospects
According to the Galileo Mission Requirements, the Commercial Service (CS) will provide an ‘added value’ with respect to the Galileo Open Service and other GNSS signals. This paper presents some background of the Galileo CS, its current status and its prospects for the next years. |
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Introduction and context
A Brief History of the Galileo Commercial Service
In the late 1990s, while the European Union was defining what services Galileo would offer, two access-controlled services were defined: CAS1 (Control Access Service 1) and CAS2. CAS1 later became the Commercial Service (CS), and CAS2 the Public-Regulated Service (PRS). Both CS and PRS were designed to allow access control by the encryption of the signal at spreading code level, mainly for commercial reasons in case of the CS, and for security reasons in case of the PRS.
The CS was a cornerstone of the Galileo public-private partnership strategy. Back in the early 2000s, Galileo was foreseen to be developed by a public-private partnership, and its costs were going to be shared by the public and private sectors. A consortium of private companies would put their know-how and resources into the development, deployment and operation of Galileo. In exchange, they would collect revenues from the sizeable value-added services that the Galileo program was supposed to bring to society and economy.
However, the public-private partnership negotiations proved that the costs and risks of developing Galileo, even if mitigated by the public sector participation, were not compensated by the potential revenues derived from its exploitation. Finally, by 2007 the Concession approach was replaced by an approach in which Galileo deployment would be fully funded by the European Union. When the funding approach was shifted to a full public funding, the CS definition and development was postponed in favour of the other Galileo services: the Open Service (OS), the Public Regulated Service, the Search-And Rescue, and the Safety-Of-Life service, the latter currently undergoing a redefinition.
Nevertheless, the Galileo CS appeared in the EU 2008 GNSS Regulation (European Union, 2008) where it was stated that Galileo should “offer a commercial service (CS) for the development of applications for professional or commercial use due to improved performance and data with greater added value than those obtained through the open service”.
Since the reorientation of Galileo exploitation in 2007, a number of activities have been performed toward the further definition of the CS:
• Round tables in 2009 were held to define the services to be offered by the CS.
• An internal (EC/GSA/ESA) Working Group was operative in 2010-2011 to further develop the service.
• A business case for high accuracy and authentication was prepared by the European GNSS Agency GSA, showing the business viability of both services.
• End-to-end provision concepts were developed by the European Commission, by which the CS would be fully provided and exploited by the public sector (as the other services).
• A Commission Working Group was created in 2012 to involve EU Member States in CS discussions.
These activities led to the proposal of high accuracy and authentication as the services to be offered by the CS. However, several unknowns remained about the service definition, service provision architecture, public/private role in the exploitation scheme, market size and eventual profits. The 2013 CS parallel studies later described in this paper were launched to answer most of these unknowns.
EU GNSS Regulation and High Level Objectives
The current EU GNSS Regulation (European Union, 2013) and associated Galileo program documentation state the following about the CS:
• The CS shall enable “…the development of applications for professional or commercial use by means of improved performance and data with greater added value than those obtained through the open service”
• The CS is based on “commercial ranging and data, whose access shall be controllable in order to allow fees to be levied.”
• “The Commercial Service signals shall be the Open Service signals, plus two encrypted signals in the E6-band.”
• “…the CS shall offer a payable added-value service, which can be exploited through a revenue-sharing mechanism with the private sector.”
As shown in the rest of the paper, the current CS definition and demonstration work is based on the elaboration of the abovementioned items, in a way that best satisfies the high level objectives defined by the Programmes for the CS, which have been defined as follows:
• Maximize public benefits offered by satellite navigation for citizens.
• Create economic value for the EU in general.
• Provide the best navigation services possible with the current and future assets to the broadest GNSS community.
• Promote innovation by allowing Galileo to offer novel services, ideas and solutions not currently existing or being provided.
• Create a potential revenue source for the public sector to support the maintenance of EU satellite navigation services in the future.
The European Commission (EC) is currently working jointly with the European GNSS Agency (GSA) and with the European Space Agency (ESA), with the support of Member States, through the EU Member States CS Working Group, on the roadmap leading to the provision of an operational Commercial Service, and its associated exploitation model, in the following years.
This paper presents a summary of the current status of the CS and its prospects. The following sections present the Galileo CS signals, the currently foreseen services, including potential architectures and provision schemes, and some plans about its commercial exploitation.
Galileo commercial service signals
The capabilities of the Galileo Commercial Services depend directly on what capabilities the CS signals can bring. This section describes the Galileo signals foreseen to provide the CS.
The Galileo CS is mainly based on 2 signals: E6B and E6C. They are modulated on a carrier frequency of 1278.75 MHz, within the E6 band, as shown in Figure 1. In addition to E6B and E6C, the Galileo mission also allows the CS to be supported by spare bandwidth of other signals.
Although the E6 band is allocated for Radionavigation Satellite Services (RNSS) on a co-primary basis, it is currently used for other purposes, including radars and amateur radio and TV communications. The Commission’s Galileo frequency management team have therefore launched actions to implement measures that will allow the successful reception of the CS signals in all regions.
Figure 2 shows the Galileo signal modulations, including E6B and E6C.
As it can be observed in the figure, the E6B and E6C components are both modulated in the in-phase component of the E6 signal, by a Code Division Multiple Access (CDMA) Binary Phase Shift Keying BPSK(5) modulation. Unlike many of the modernised GNSS signals, which follow BOC approaches, the E6B/C follow a classic BPSK modulation and reach its maximum power spectral density at the carrier frequency. Table 1 further details the CS signal components. Spreading codes are 1ms long, and a 100-chip secondary code with a duration of 100 milliseconds is added to the pilot component.
The E6B data signal provides 1000 symbols per second. 16 symbols are used for page synchronisation, while the remaining 984 are used for convolutionally encoding 492 bits of data. Convolutional encoding follows the same Forward Error Correction algorithm as other Galileo signals. This format is described in the Galileo OS SIS ICD (European Union, 2010). This scheme is also followed by other radionavigation signals, as e.g. SBAS or GPS’s L5 or L2C (GPS Directorate, 2012).
Out of the 492 bps, 448 can be used to transmit Commercial Service data, as shown in Figure 3.
Foreseen services
Without precluding the provision of other services in the future, the main services foreseen to be part of the CS are high accuracy and authentication.
High Accuracy
High accuracy is understood as the ability of the system to provide a positioning accuracy in the order of a few centimetres. State of the art techniques for high accuracy are based on the use of carrierphase measurements and include Precise Point Positioning (PPP), through which high accuracy satellite clock and orbit data are provided to a user, and Real Time Kinematics (RTK), through which a reference station or network of stations provides precise measurement corrections to the user. The main high accuracy approach under study for provision by the CS is based on PPP.
Several internal studies have shown that a 448 bps bandwidth per satellite allows the transmission of PPP satellite and orbital data at an adequate update rate to provide accuracy in the centimetre level. The update rate is especially relevant for the satellite clock corrections, which should be corrected and transmitted to the user with a latency of few seconds.
One advantage of transmitting PPP corrections in the L band is that PPP receivers are already equipped with L-band antennas and RF front-ends, which may simplify the reception of the data. Another advantage of the use of Galileo satellites is that the coverage at high latitudes is significantly improved with respect to that of geostationary satellites, whose reception may be difficult above latitudes around 60º, as shown in figure 4 (note that best possible GEO elevation refers to the case where the satellite and receiver are at the same longitude). At high latitudes, Galileo (and other GNSS) satellites can be received in good visibility conditions.
Authentication
Authentication is understood in this context as signal authentication, i.e. the ability of the system to guarantee to the users that they are utilising signals from the Galileo satellites and not from any other source. In this context, spreading code encryption (SCE) can be included as one of the authentication options, as can navigation data-based authentication through asymmetrical or symmetrical architectures. Authentication can also be extended from the signal domain to the user position domain through the appropriate technologies, to ensure that the user position calculated with Galileo and potentially other navigation satellites and sources, is authentic.
In addition to the above mentioned features, the Galileo E6B and E6C signals have the possibility to be encrypted at spreading code level. Therefore, the Galileo CS signals offer the first-ever GNSS spreading code encryption capability for purely civil purposes, allowing to increase the civil security of professional applications.
In addition to the spreading code encryption capability, part of the 448 bps bandwidth can be used for data authentication, and the CS may be complemented with E1-B I/NAV message bits (see Galileo OS SIS ICD (European Union, 2010) for more details), either as the navigation data to be authenticated, or by the use of spare bits for a data authentication service. At the moment, both standalone and communicationassisted modes are being investigated. Communication-assisted modes can lighten the burden of the receiver hardware by allowing the remote processing of the received encrypted samples.
Authentication Service Provision Schemes
As mentioned above, the objectives of the EU GNSS Programmes with the CS should go beyond just obtaining revenues. A means to achieve this is by the provision of two levels of authentication, a data-based authentication service in the E1 I/NAV open signals for mass market users, and a data-based plus spreading-code based authentication service through the CS signals. The Programmes are studying the performance of a Navigation Message Authentication (NMA) service that could be offered by Galileo (Fernández-Hernández, I. 2014). Within this provision scheme, a lighter NMA service could be provided on the E1 signals with the following features:
• Lower receiver/key management complexity
• Adequate for lower security / mass market applications: e-commerce, road, handheld location-based services, etc.
• Potential Provision scheme: Free & based on NMA.
In addition, a professional authentication service based on E6 or E1+E6 with these features could be provided:
• Higher receiver/key management complexity and robustness
• Adequate for high security commercial applications: surveying, tracking & tracing, maritime, etc. and potentially some institutional applications
• Potential provision scheme: Controlled & Based on NMA + Spreading Code Encryption (SCE).
Both services could be operated and exploited in parallel. As a means to improve bandwidth for high accuracy services, the professional service could be totally or partially based on the E1 NMA service for data authentication purposes.
One way to optimally provide the two authentication services plus high accuracy, which seems to satisfy the end user and service provider needs, would be:
• To leave the E6B component unencrypted at spreading code level, so high accuracy providers could transmit high accuracy data but not be involved in the spreading code key management.
• To have E6C component (pilot) encrypted, so E6C ranging measurements based on encrypted spreading codes can be used for authentication.
• To transmit data authentication information in E1B (open NMA service), E6B or both.
EC/GSA, with the support from ESA, are currently studying these aspects to define the best exploitation scheme of the CS to achieve the previously mentioned objectives.
The CS parallel studies (2013)
In order to cover more exhaustively all the possible Commercial Service options, the Commission launched in December 2012 two 1-year parallel CS definition studies. The purpose of the studies was to define the technical options and exploitation model most suitable for the Commercial Service with the current and future Galileo assets.
The study CESAR (“Galileo CommErcial Service, A Reality”) was led by GNSS consultancy firm FDC (France Development Conseil), and included the participation of major GNSS high accuracy service providers and infrastructure developers as Trimble, Fugro, Thales Alenia Space France and Keynectics. The study GALCS (“Galileo Commercial Service definition”) was led by GMV, and included the participation of CGI and Helios Consulting. Both studies have successfully concluded by mid- December 2013. The developments of the studies have been actively monitored by the EC’s Joint Research Centre (G6 unit), which has also participated in the analysis of Galileo authentication, GSA, ESA and EC DG ENTR and have confirmed high accuracy and authentication as the two principal services to be pursued by the Galileo Commercial Service.
The studies analysed the needs and constraints of 50+ market segments having a potential interest in a GNSS high accuracy or authentication commercial service, with positive results. The main results are summarised in the following items:
• Galileo should provide high accuracy and authentication services on a separate basis but simultaneously through the CS signals, in a way that can be used separately or combined. This implies that access control to the two services must be managed separately.
• There is an interest from external service providers to provide high accuracy services from the Galileo constellation through the CS signal. The service provision scheme, algorithms and technology are mature enough, since they are already used through existing services based on GPS signals and through GEO satellite communication links.
• There is an interest from external service providers to provide authentication services from the Galileo constellation through the CS signal. Although the requirements for the system infrastructure are mature, the service provision scheme and exploitation technology require some further definition.
• The provision of both high accuracy and authentication will require external service providers to connect to the Galileo system. This connection is currently foreseen through the GNSS Service Centre. The high accuracy service can highly profit from a realtime connection to the system, and the authentication service requires a key management interface with an external service provider that will liaise with the end users. Security accreditation issues derived from this architecture are under study at the moment.
• Accuracy is sensitive to the bandwidth used in the CS. The use of around 75-90% of the CS data transmission bandwidth (448 bps per satellite) for the high accuracy service is likely to be required. Accuracy is also sensitive to data transmission latency, as the satellite clocks need to be estimated and transmitted frequently. A reliable low-latency data channel in the order of few seconds to broadcast data through Galileo would be required. This means that only the satellites that are connected to the ground at a certain time can transmit high accuracy data.
• High accuracy providers prefer not to be part of the key management processes for the CS spreading code encryption and therefore their interest on the CS requires the control of the user access at data level.
• The encryption capability of the CS signal spreading codes can be used to increase authentication robustness.
• There are no GNSS authentication services as such in the market yet, so it is not possible to take into account market and user experiences as much as for the high accuracy case.
• Authentication could be accommodated in the remaining CS E6B signal data transmission bandwidth (10-25%). If the authentication data is modulated on a non-encrypted spreading code signal or component (e.g. E1 I/ NAV or E6B, if the signals can be encrypted separately), this would allow the segmentation of users into two authentication levels, one based on data authentication only, and a more robust one based on data and encrypted codes. This two service level approach was not considered as a negative point towards a potential commercial exploitation of authentication.
• If a GNSS authentication service is mandated for certain specific securitycritical applications, this service should not be based on a payable authentication commercial service.
The CS demonstrator (2014-2016)
Based on the results of the CS studies, the European Commission launched the CS Demonstrator project in early 2014. The project has been named Authentic and Accurate Location Experimentation with the Commercial Service, or AALECS. The contract has been awarded to a consortium led by GMV and involving CGI, QASCOM, IFEN, Veripos and KU Leuven. The project will last around two and a half years.
The AALECS project will build a platform to connect to the Galileo system and transmit CS data through the Galileo satellites. This platform is foreseen to be operational by 2015 and will demonstrate the CS real performance.
It should be noted that, in order to guarantee equal treatment in later stages of the CS exploitation roadmap, particularly in the case of high accuracy services, the CS Demonstrator is oriented to the development of a testing platform and authentication solutions. It is not funding any activity related to the development or adaptation of high accuracy solutions for the CS, and as soon as the platform is qualified, it will be open for testing by external entities.
CS Early Proof-Of-Concept
Before that, the AALECS project will perform some early testing with the Galileo system to prove the CS concept viability during 2014. This early testing will be performed by an activity named CS ‘Early Proof-Of-Concept’, or EPOC, and its results will be officially reported at the Galileo Early Services Declaration.
The objective of the EPOC is to demonstrate the main functionalities of the Commercial Service at the Galileo Early Services milestone, which is currently foreseen for the end of 2014, or the beginning of 2015. This fact has led to a design philosophy in which simplicity has been the main driver. The main requirement for the EPOC is to be able to test the capability of the Galileo System to correctly transmit CS data in the E6 band, including the demonstration of user applications at terminal level. In this framework, the main identified abilities of the EPOC are as follows:
• Testing the capability of the satellites to transmit data in the E6-B band.
• Testing the encryption and decryption process of the CS signal in E6-B and E6-C components.
• Testing the robustness and performance of position and timing authentication with the E6 real signals
• Testing the reception conditions of E6 signals in realistic target user environments
In order to perform this demonstration the EPOC shall be able to close the loop of E6 data from its generation to its reception (the loop steps have been numbered). Figure 5 depicts the communications links established between the EPOC and third parties and keeps the EPOC system as a black box.
By late June, the transmission by the available IOV Galileo satellites of data external to the Galileo system has been successfully demonstrated. The external data, that is, data generated outside of the Galileo perimeter and later injected into the system, were broadcast through the Galileo E6B signals for a period of some hours. Current tests under execution including authenticated satellite position information show promising performances.
The CS Demonstration Platform
In parallel to the proof-of-concept phase in 2014, a CS demonstrator platform is currently being developed. It will allow the transmission of CS data in real time from the Galileo satellites. Its architecture is shown in the figure 6.
The CS Demonstrator will consist of the following components:
• The CS System Emulator (EMU): is a software platform deployed on a commercial PC that will emulate the Galileo system including its bandwidth and latency capabilities and perform service volume simulations. Its key output is a Contact Plan describing which satellites will be connected to the ground segment and therefore able to send CS data. This plan will be used by other elements as a fundamental configuration parameter for test scenarios.
• CS Receiver Platform (RXP): is a multi-GNSS multi-frequency receiver with E6 capability and an attached hardware platform able to process Galileo E6 signal and other GNSS signals to log data and to communicate in real time with the CS Provider Test Bed. The RXP will be used as a Commercial Service Provider (CSP) monitor to feed the CS data generation algorithms, and also as a user terminal to test user performances.
• CS Provider Test Bed (PTB): is a real time platform able to process recorded data files from receivers. Through an Application Programming Interface (API), the PTB will allow up to five CS data generation elements (DATAGENs) to be tested concurrently, either connected to the real Galileo system or to test equipment to allow the service to be explored thoroughly and with simulated stress scenarios. The PTB is the core of the CS Demonstrator.
• CS Signal Generator and Threat Simulator (SG): is a platform generating Galileo signals and allowing the testing of a receiver under different user conditions and threats. For example, it will simulate the representative threats at the Signal-In-Space level, such as meaconing, replay and spoofing attacks. This is a necessary function to test the performances of the authentication service.
Once the CS Demonstrator platform is built by mid-2015, and the GSC and the Galileo system are ready, the Real-time Signal-In-Space phase will start (Phase 2): in this phase, the CS Demonstrator platform will connect to the Galileo system through the GNSS Service Centre (GSC), which will enable the transmission of realtime E6 SIS data with a latency of some seconds.Once this chain is integrated and validated, the CS Demonstrator will start Phase 3. In this phase, it will support the connection of external service providers to test the transmission of their own data in the real Galileo CS signal.
The GNSS Service Centre and the CS Demonstrator
The GNSS Service Centre Nucleus (GSC-n) is the precursor of the fullyfledged GSC. Since November 2012, the GSC-n is providing basic services to the user community via a web portal (http://www.gsc-europa.eu/) and a dedicated user helpdesk. The web portal is conceived as the one-stop-shop for the Galileo users providing easy access to Helpdesk support, information on system status, user notifications and general programme information.
The fully-fledged GSC is identified as the element of the Galileo infrastructure providing a centralised ground interface between the broad Galileo Open Service (OS), Commercial Service (CS) user communities and the Galileo system infrastructure and operator for the provision of specific services beyond the Galileo Signal In Space (SIS) transmitted by the operational satellites.
This centre is conceived as a centre of expertise, knowledge sharing, custom performance assessment, information dissemination and support to the provision of value-added services enabled by the Galileo OS and CS core services. To implement these missions, the GSC has interface with the key elements of the Galileo ground segment, as well as with external entities. Figure 7 depicts the overall context of the GSC.
Phase 2 of the CS Demonstrator considers the connection of the platform to the Galileo system through the GNSS Service Centre (GSC V1) located in Torrejon de Ardoz, Madrid (Figure 5). This integration will be done on the basis of a CSPGSC interface that is under definition in parallel with the rest of the CS activities. The main flow in this interface will be the CS data that is generated by the CSP and provided to the GSC for broadcast through the Galileo SIS. Other flows are under definition in this interface:
• Broadcast status information from the GSC to the CSP
• Transfer of CS key material from the GSC to the CSPs
• Provision of Galileo system status information to the CSPs and results of specific data queries
• Provision of off-line data to the CSPs to assist with their service provision
• Provision of near real-time data to the CSPs to assist with their service provision.
The integration activities of the CS Demonstrator with the GSC consider scenarios without Galileo SIS. This will facilitate the CS Demonstrator integration with the GSC even if no access to the Galileo SIS is possible at some stages. If necessary, the CS Demonstrator platform could be moved to the GSC for on-site integration. As a result of this integration, the CS Demonstrator platform will be ready for the transmission of CS data through the Galileo signal within Phase 2 activities, and ultimately, during Phase 3 activities, it will support the connection of CSPs to test the transmission of their own data through the Galileo CS signal. This will be a valuable input for the final definition of the Galileo CS.
A key aspect of the CS provision architecture through the GSC will be security accreditation. The GSC project is regularly coordinating with the Galileo security team to develop an architectural solution that is secure while allowing the delivery of the CS.
Commercial exploitation
Potential users have indicated their willingness to pay for services offered by the Galileo CS. Market studies from the GSA Market Development Department predicted a potential 15 million worldwide user base for the CS with revenues in the order of 120 M€ per year, from both authentication and high accuracy services. These figures are sensitive on assumptions regarding the initial CS exploitation date and exploitation model that are under consolidation at the moment. The GSA has prepared in parallel a “CS Business Plan” with an analysis of the CS target markets and exploitation options.
In parallel to the market studies, GSA organises periodic industry consultations involving, among others, the main high accuracy commercial providers, to discuss technical and exploitation models proposed by the private sector and identify candidates for a potential service provision. The work by GSA confirms high accuracy and authentication as the most promising options for the CS according to the downstream market and industry.
GSA consultations and market studies have highlighted the fact that the window of opportunity for the CS may not remain open until the next generation of Galileo arrives. The services therefore should be available already for the Galileo 1st generation. Authentication is a new market whereas there is already a global high accuracy market established. Therefore, when it comes to defining a commercialisation scheme, especially for High accuracy, it is important to understand how the arrival of a public infrastructure can affect the market and its competition. Galileo is aiming at increasing the global market on high accuracy rather than disrupting it.
The commercialisation scheme will be conceived once the services are fully defined. However, there are some key principles concerning cooperation between public and private sectors that the commercialisation scheme will need to follow:
• The commercialisation will be done in collaboration with the private sector (Commercial Service providers broadcasting high accuracy data via E6)
• The procedure for implementing the commercialisation scheme will be undertaken as openly as possible for all market actors
• The future scheme will aim at not disrupting the market – industry will be fully briefed and involved during regular industry consultations.
Summary and conclusions
The Galileo Commercial Service (CS) was a cornerstone of the Galileo public-private partnership exploitation strategy. Since the reorientation of Galileo exploitation in 2007, when the Concession approach was replaced by the full funding of Galileo by the European Union, the CS strategy has broadened to pursue the maximisation of public benefits, value creation, innovation promotion and navigation performance increase, in addition to the generation of revenues.
The Galileo CS is mainly based on 2 signals: E6B and E6C, modulated on a carrier frequency of 1278.75 MHz. The CS signals permit the transmission of 448 bps per satellite, and spreading code encryption. The current services foreseen to be offered by the CS are high accuracy and authentication. High accuracy can be transmitted in the 448 bps of the E6B component. The current bandwidth and foreseen latency permit the transmission of precise point positioning (PPP) corrections from the Galileo satellites with an accuracy of a few centimetres. The final performances will depend on the Galileo downlink capabilities and system latency. One of the potential advantages of a high accuracy Galileo CS is the coverage and transmission robustness at high latitudes. Authentication data can be accommodated in the spare bandwidth of the E6B and E1B signals, and can be also based on the spreading code encryption feature. The provision of an open data-based authentication service for end users and mass market applications, and a controlled spreading code-based authentication service for professional and institutional users is currently under study.
The Commission launched in December 2012 two 1-year parallel CS definition studies. The studies have confirmed the feasibility and potential of high accuracy and authentication. The next step is to build a CS Demonstrator platform, to test services with the real Galileo signalin- space. This platform will be built as part of the AALECS (‘Authentic and Accurate Location Experimentation with the Commercial Service’) project, recently started. The first building block of this project is the Early Proof- Of-Concept, which between June and September 2014 will allow the testing of E6-based navigation authentication. In its operational setup, the CS Demonstrator will transmit data through the GNSS Service Centre, located in Torrejón, Spain. A key driver of the CS provision through the GSC will be security accreditation of an architecture allowing the transmission of CS data with an adequate latency. The commercial exploitation of the Galileo CS is currently under definition, and will be further defined once the technical feasibility and timeline of the foreseen services is confirmed. In order to promote dialogue, transparency and equal treatment, GSA has established periodical consultations with users and industrial stakeholders, that allow to commercialise Galileo services in a way that avoids value destruction while maximises public benefits and the usage of Galileo assets. In any case, the Galileo CS represents a great opportunity for the European GNSS Programmes and has the potential to significantly improve the security and accuracy of worldwide civil location services.
Acknowledgements
The authors would like to acknowledge the CESAR, GALCS and AALECS teams for their contributions to the CS definition and demonstration, and O. Chassagne and H. Tork from the European Commission for their involvement on the Galileo Commercial Service in the last years.
References
European Union (2008), Regulation (EC) No 683/2008 Of The European Parliament And Of The Council of 9 July 2008 on the further implementation of the European satellite navigation programmes (EGNOS and Galileo). Official Journal of the European Union, L 196.
European Union (2010). European GNSS (Galileo) Open Service Signal In Space Interface Control Document. OD SIS ICD, Issue 1.1, September 2010.
European Union (2013), Regulation (EU) No 1285/2013 Of The European Parliament And Of The Council of 11 December 2013 on the implementation and exploitation of European satellite navigation systems. Official Journal of the European Union, L 347.
Fernández-Hernández, I. (2014), GNSS Authentication: Design Parameters and Service Concepts, Proceedings of the European Navigation Conference 2014, Rotterdam, Netherlands, n.150.
GPS Directorate (2012). Navstar GPS Space Segment/User Segment L5 Interfaces. 2012. ISGPS- 705C. 05-SEP-12.
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