Overview of GNSS Interference in Aviation

GNSS, including GPS, Galileo, GLONASS, and BeiDou, plays a critical role in modern aviation. It provides precise position, navigation, and timing information, supporting en-route navigation, terminal procedures, and approach operations such as LPV (Localizer Performance with Vertical Guidance) and GBAS (Ground-Based Augmentation System) approaches.

The recent increase in the frequency of interference with GNSS signals is a concern for ICAO, IATA, and other regulatory bodies. During a recent workshop on the subject, these agencies committed to keeping aviation safe, secure, and navigable. With the current geopolitical tensions, a foreseeable reduction in such interferences appeared remote.

Types of GNSS Interference

GNSS interference can be categorized into intentional and unintentional sources:

• Intentional Interference (Jamming and Spoofing): Malicious attempts to disrupt or deceive GNSS signals.
• Unintentional Interference: Signal degradation caused by electromagnetic interference (EMI), solar activity, or structural reflections.

1. Intentional GNSS Interference

Jamming

• Description: Transmitters emitting signals to overpower GNSS signals, leading to loss of signal reception.
• Impact: Loss of positional accuracy, degradation of navigation performance, potential failure of GNSS-dependent approaches.
• Prevalence: Increasing reports, especially in conflict zones, densely populated urban areas, and near critical infrastructure.

Spoofing

• Description: Creating fake GNSS signals to deceive the receiver into computing incorrect positions.
• Impact: Dangerous in precision approaches, potentially causing aircraft to deviate from intended flight paths.
• Detection Challenges: Spoofing signals are increasingly sophisticated, making detection difficult.

2. Unintentional Interference

• Sources: Radio frequency interference from ground-based transmitters, electronic devices, solar flares, or structural reflections.
• Impact: Signal degradation, increased positioning error, and outages, especially in urban or mountainous environments.

3. Current Threat Landscape and Incidents

• Operational Incidents: Reports of GNSS outages affecting approach operations, particularly LPV and GBAS-based approaches.
• Military and Political Concerns: Jamming and spoofing are exploited in asymmetric warfare, posing risks to commercial and military flights.

Recent Incidents and Developments in GNSS Interference in India

Incidents of GNSS Disruption and Interference

• Urban and Strategic Areas: India has reported sporadic GNSS signal disruptions in major metropolitan regions like Delhi, Mumbai, and Bengaluru, often attributed to unintentional interference from dense electromagnetic activity.
• Border Regions: In border states such as Punjab, Jammu & Kashmir, and Arunachal Pradesh, there have been reports of GNSS jamming and spoofing, primarily linked to military exercises or deliberate interference by adversarial entities.

Specific Events:

• 2019-2020: Indian authorities detected instances of GNSS signal jamming during military exercises near the China border, which temporarily affected navigation and communication systems.
• 2022: Reports surfaced of suspected spoofing attempts targeting civil aviation navigation systems in strategic regions, prompting investigations by the Indian Space Research Organisation (ISRO) and Defense agencies.
• 2023: There have been sporadic reports of interference affecting GPS-based services in some parts of the country, especially during large public events or protests, possibly due to unintentional RF emissions.

Mitigation and Countermeasures

Receiver Design Improvements:

• Enhanced anti-jamming and anti-spoofing algorithms.
• Multi-constellation and multi-frequency receivers for increased resilience.

Augmentation Systems:

• GBAS (Ground-Based Augmentation System): Provides integrity and correction signals, reducing reliance solely on GNSS.
• SBAS (Satellite-Based Augmentation System): Offers integrity information, improving reliability.

Monitoring and Detection:

• Use of signal authentication techniques.
• Onboard interference detection systems.
• Ground-based monitoring networks for interference sources.

Operational Procedures:

• Use of alternative navigation aids (VOR, DME, inertial systems) during GNSS outages.
• Pilots are trained in recognizing and responding to GNSS anomalies.
• Government and Industry Responses

Enhanced Monitoring: The Indian government, through agencies like ISRO and the Directorate General of Civil Aviation (DGCA), has intensified efforts to detect and mitigate GNSS interference.

Regulatory Measures:

• The Department of Telecommunications (DoT) has issued guidelines for electromagnetic interference management, including restrictions on unauthorized RF transmitters.
• The DGCA has mandated the use of multi-sensor navigation systems (e.g., inertial navigation coupled with GNSS) for civil aircraft, especially in sensitive regions.

Operational Adaptations:

• Indian Air Force (IAF) and civil aviation authorities have increased reliance on traditional radio navigation aids (VOR, DME) in areas prone to GNSS disruptions.
• Deployment of ground-based monitoring stations to track interference sources and alert authorities of jamming/spoofing events.

Recent Developments and Research Initiatives

India’s Indigenous GNSS Systems: NavIC (Navigation with Indian Constellation)

Overview: NavIC is India’s indigenous regional navigation satellite system, operational since 2018, comprising 7 satellites providing accurate positioning over India and the surrounding region.

Features:

• Designed to offer higher integrity, accuracy, and availability than foreign GNSS systems.
• Has anti-jamming and anti-spoofing capabilities built into its signals.
• Used for both civilian and military applications, reducing reliance on GPS and other foreign systems vulnerable to interference.

Recent Upgrades:

• Efforts to expand NavIC’s constellation and improve signal robustness.
• Integration of NavIC into critical infrastructure, including aviation, defense, and transportation.
• Ground-Based Monitoring and Interference Detection Systems

Implementation:

• Deployment of dedicated ground stations across strategic locations to monitor GNSS signal integrity.
• Real-time detection of interference sources, enabling prompt response and mitigation.

Purpose:

• Track jamming/spoofing events.
• Provide data for investigations and policy formulation.
• Support civil and military operations with interference alerts.

Anti-Jamming and Anti-Spoofing Technologies:

India is actively investing in R&D for GNSS receivers with advanced anti-jamming and anti-spoofing capabilities, including cryptographic authentication features.

Policy and International Collaboration:

• India participates in regional forums like the South Asian Association for Regional Cooperation (SAARC) and Indo-Pacific dialogues to share intelligence on GNSS interference threats.
• Engagement with international bodies such as ICAO and the International Telecommunication Union (ITU) to develop standards for interference mitigation.

Research in Resilient Navigation and Positioning

Hybrid Navigation Systems:

• Combining GNSS with inertial navigation systems (INS), visual odometry, radar, and terrestrial aids.
• Ensures continued navigation capability during GNSS outages or interference.
• Artificial Intelligence (AI) and Machine Learning:
• Using AI to analyse interference patterns and predict threats.
• Enhancing the capability of onboard systems to distinguish between legitimate signals and interference

Regulatory and Industry Response

• Standards Development: ICAO and RTCA have issued guidelines for GNSS integrity and interference mitigation.
• Research Initiatives: Ongoing R&D into resilient navigation architectures, including hybrid systems combining GNSS with inertial navigation and vision-based systems.
• International Cooperation: Sharing intelligence information and threat assessments among countries and agencies

Indian Regulatory Frameworks& Responses

1. Electromagnetic Compatibility (EMC) Regulations

• Guidelines: The Department of Telecommunications (DoT) issues standards for electromagnetic emissions to prevent unintentional interference.
• Enforcement: Regular audits and monitoring of RF emitters in urban, industrial, and strategic zones.

2. Authorization and Licensing for RF Transmitters

• Strict Licensing: All RF transmitters, including those used in industrial, commercial, and military sectors, must obtain licenses.
• Unlicensed Transmitters: Strict penalties for unauthorized RF emissions that could cause interference.

3. National Policy on GNSS Security and Integrity

Policy Objectives:

• Protect the Indian satellite navigation infrastructure.
• Promote indigenous systems like NavIC.
• Establish protocols for interference detection, reporting, and countermeasures.

Implementation:

    Collaboration between ISRO, defense agencies, and the Ministry of Electronics and Information Technology (MeitY).

4. Legal and International Cooperation

Legal Measures: The Indian Penal Code and related laws criminalize malicious interference with satellite signals and communication infrastructure.

International Engagement:

• Active participation in regional forums like the South Asian Association for Regional Cooperation (SAARC) and ASEAN+ agreements.
• Cooperation with ITU and ICAO for setting international standards and sharing intelligence on interference threats.

5. Capacity Building and Training

• Workshops & Exercises: Regular training programs for military, civil aviation, and law enforcement agencies on interference detection, mitigation, and response.
• Public Awareness: Campaigns to educate industry stakeholders on electromagnetic compatibility and interference risks

Challenges and Future Outlook

• Growing Threats: As GNSS becomes more integral to civil and military operations, the threat of interference—both accidental and malicious—is expected to increase.
• Need for Resilience: India is prioritizing the development of resilient navigation systems that combine GNSS with inertial, visual, and terrestrial aids.
• International Cooperation: Strengthening regional cooperation to detect and respond to interference incidents, particularly along sensitive border zones.
• Enhanced Security: Incorporation of cryptographic authentication (e.g., Galileo’s OS-NMA, GPS’s future signals).
• Resilient Navigation: Development of multi-sensor fusion navigation solutions to mitigate GNSS vulnerabilities.
• Operational Flexibility: Increased use of alternative navigation aids and procedures to ensure safety during GNSS disruptions.

Summary

GNSS interference remains a significant concern for aircraft navigation and approach aids, especially with the increasing sophistication of jamming and spoofing techniques. While technological advances and system redundancies improve resilience, continued vigilance, regulatory oversight, and technological innovation are essential to safeguard aviation operations against GNSS interference threats.

India has experienced sporadic GNSS interference incidents, especially in strategic border regions and urban centers. The government, along with ISRO and the military, has been proactive in implementing mitigation measures, developing indigenous navigation systems like NavIC, and enhancing technological resilience. Ongoing research, regulatory measures, and international collaboration are crucial to counter evolving GNSS interference threats in India.

India’s approach combines cutting-edge technological development with robust regulatory measures to safeguard GNSS operations:

• Development of indigenous, resilient navigation systems like NavIC.
• Deployment of advanced anti-jamming, anti-spoofing receivers.
• Establishment of ground-based interference monitoring networks.
• Enactment of strict electromagnetic compatibility and licensing regulations.
• Active international cooperation and legal frameworks to deter malicious interference

Author: GR Mohan