Acp working group b meeting

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(Tokyo, Japan, January 28 – February 6, 2004)
Agenda Item #g: discussion of potential new WG-B agenda item on radio frequency interference


(Presented by the United States of America)

The Federal Aviation Administration (FAA) investigates and resolves Radio Frequency Interference (RFI) events affecting the United States Air Traffic Control System communications, navigation and surveillance (CNS) services. This is accomplished in coordination with the Federal Communications Commission (FCC) and other law enforcement federal agencies as well as non-federal organizations. The FAA RFI program includes a database system to record, track and archive events, equipment to detect and locate sources, and enforcement agreements to mitigate such sources to restore CNS services to the expected level of safety. This paper provides an overview of the FAA Spectrum Management RFI program.

1. Introduction

    1. The Federal Aviation Administration Spectrum Management office has implemented an RFI reporting and investigation process to resolve incidents that impact the operations of the National Airspace System (NAS) including the Global Positioning System (GPS). The RFI investigation process begins with pilot reports provided to air traffic facility personnel. The RFI reports are recorded into the Spectrum Management Database (SMDb). Spectrum management engineers work with FAA field technicians to locate sources of RFI. When the interfering source is located and identified, the FAA coordinates with other government and non-government agencies to mitigate the RFI. This paper provides further details on this process and the FAA RFI program.

2. Discussion

    1. The FAA is recording RFI events with improved automated tools that allow for greater analysis of these incidents. Figure 1 shows a subset of preliminary yearly statistics on increasing RFI events compiled by spectrum management from two sources, the Maintenance Management System (MMS) and the SMDb. The SMDb is expected to be the tool that captures all RFI events to aeronautical services in the near future.

Figure 1: Yearly RFI Events in the United States NAS
A critical element in the process of effectively resolving RFI problems disrupting aeronautical radio services is the reporting and tracking of events as they occur. The FAA Spectrum Management office established a liaison officer at the Air Traffic Control Systems Command Center and National Operations Control Center (ATCSCC/NOCC) to coordinate quick resolution of RFI and Global Positioning System (GPS) anomalies in the NAS. The spectrum liaison officer works with regional Frequency Management Office (FMO) personnel to record RFI incidents into the SMDb and track the resolution progress of such events. With the use of the SMDb as an automated reporting and tracking tool the spectrum liaison officer provides daily RFI resolution status to FAA executives. In addition, the command center spectrum liaison may provide near real-time conditions of RFI reports as received by pilots and air traffic personnel, to aid in minimizing the time for resolving these events given the collocated status with national air traffic personnel and airline organizations.
The command center spectrum liaison coordinates with the Federal Communications Commission (FCC) and law enforcement government agencies at the national level when local efforts to eliminate the positively identified RFI problem have failed. In addition, when RFI events causing severe impact to NAS services are not readily resolved the spectrum liaison coordinates the activation of a national FAA RFI Tiger Team to resolve the problem. Special RFI Tiger Team procedures are implemented to provide required resources to quickly eliminate the RFI problem.

    1. One critical element to effectively resolve RFI problems is the strategic use of direction finding and spectrum analyzer equipment. The FAA Spectrum Management office has implemented a five-platform capability to effectively locate sources of RFI to aviation radio services. These five platforms range from handheld manual direction finding devices to automated ground mobile, airborne and fixed sites. Although each platform can operate independently, it is the combined coordinated effort across all platforms and the expertise of spectrum management engineers that provides the most effective capability to resolving RFI. Each platform will be briefly described in the following sections.

    1. The Airborne Interference Monitoring Detection System (AIMDS) platform was implemented in the FAA flight inspection aircraft. Figure 3 shows the antenna array and the direction finder equipment use in this platform.

Figure 3: Airborne Direction Finding System
The airborne platform is very effective in locating the source when only pilots report RFI to Air Traffic facilities. In this situation the source of RFI affecting high altitude airspace sectors may be generated from many kilometers away from the aircraft’s location and makes it challenging and time consuming to locate with ground assets. The Airborne DF is used to reduce the area of search in the ground to approximately two (2) square kilometers. The FAA currently has eighteen (18) King Air (model BE-300) and three (3) Challengers (model 600) equipped with the AIMDS.

    1. The Transportable and Portable Interference Monitoring Detection System (TIMDS and PIMDS) platforms have also been implemented for resolving RFI events, which are suspected to be in close proximity to an aeronautical ground facility. Skilled Frequency Management Officers (FMO) who investigates RFI disrupting NAS services operates these units. The FMO performs an engineering analysis to determine the potential geographical area of search and deploys the appropriate platform for the particular RFI problem. These platforms also serve as assets to follow up in determining the precise location of a source after the airborne platform has reduced the search area to a few square kilometers. Figure 4 shows the Radio Frequency Interference Monitoring Van (i.e., TIMDS) as well as the Radio Frequency Interference Detector (i.e., PIMDS).

Figure 4: RFI Van and Portable Direction Finding Systems
The transportable and portable platforms can be operated unattended if necessary. The FMO specialist has advanced software automation tools available to setup a spectrum monitoring session to detect and record the interference for analysis at a later time. The FAA has implemented ten (10) RFI vans and twenty-nine (29) portable radio frequency interference detector units across the United States.

    1. The Fixed Interference Monitoring Detection System (FIMDS) platform is being implemented in specific critical areas of the United States. This platform is designed to cover a determined geographical area for which each of the direction finder sites have overlapping radio-line-of-sight (RLOS). This site strategic implementation is performed to achieve triangulation of a potential source of interference when detected by the direction finding equipment. The added advantage is that the system is available continuously and can be programmed to record spectral and signal of interest information at specific times and dates. The fixed DF platform also provides enterprise automated software tools to remotely control the equipment over the FAA Local and Wide Area Networks (LAN/WAN). All spectral signal information data is then stored in an open architecture secured database for later retrieval and playback. Retrieval of the signal information data includes audio, video and geographical location representation of the signal monitored which may be the cause of interference. Figure 5 shows the fixed site equipment and the software control screen for the FMO personnel to operate.

Figure 5: Fixed Direction Finding Network
With the Fixed DF platform the FAA has become capable of quickly locating interference sources with a great degree of precision, including both legal FM transmitters which have the potential of interfering with ILS receivers and illegal emitters such as Pirate FM Broadcasters. Figure 6 shows the triangulated building structure and location of an unlicensed Pirate FM Broadcast illegally transmitting and interfering with aeronautical radio services.

Figure 6: Unlicensed Pirate FM Station Located
At the present time the Fixed DF platform has been implemented in the vicinity of the Los Angeles International Airport, the Chicago O’Hare International Airport and the New York John F. Kennedy International Airport. Plans are underway to expand the Fixed DF capability to the Miami International Airport and other critical airports in the NAS.

    1. Other available direction finding assets include a handheld platform, which is very effective when determining the exact location of a source of RFI. The Handheld DF is a manual system with no automated software tools but it can be used effectively when the operator has learned the skills necessary to locate RFI. This equipment is widely used by FAA field personnel and is usually the first available resource to begin searching. Figure 7 shows the handheld DF with the accessory antennas required for RFI work.

Figure 7: Handheld DF System
Since the skills of the RFI investigator are critical in finding the source of interference when using the Handheld DF, the FAA Spectrum Management office has developed a special FAA training course with hands-on exercises so that field personnel readiness is always to date. The FAA Spectrum Management office has deployed approximately 200 handheld units to field Systems Management Offices (SMO). These units are in service at the present time.
Some ICAO Member States, for example, Canada and Taiwan, and the airline industry, for example, United Airlines, have sent representatives to participate in FAA RFI courses where the operation of the Handheld DF is provided as hands-on training. Future RFI training courses, where the operation of this platform will be included, are planned for RFI investigation techniques in the GPS band as well as radar bands.

    1. The FAA Spectrum Management office represents the FAA when coordinating with enforcement agencies for mitigation of RFI, especially when it is of an intentional nature, which disrupt aeronautical radio services. Interagency agreements have been developed with the United States Federal Communications Commission (FCC) and the Federal Bureau of Investigation (FBI) to mitigate RFI to aviation when local cooperation efforts haven’t produce resolution to the problem. Although not all circumstances require that law enforcement personnel intervene, collaborative efforts between the FAA, FCC and FBI can achieve mitigation of RFI to aeronautical radio spectrum effectively.

  1. Conclusion

    1. The FAA Spectrum Management office has been the leading organization in the United States for resolving radio frequency interference to aeronautical radio services. As the U.S. National Airspace System (NAS) modernizes to implement digital radio technologies, so will the tools, assets and trained personnel to mitigate present and future disruptions to aviation radio services. Sharing of the experiences and lessons learned in resolving aeronautical RFI among ICAO Member States and Organizations, will serve to further strengthen international civil aviation’s tools to support increasing levels of aviation safety and efficiency.

  1. Recommendation

    1. That the above information be used in WG-B’s deliberations on the development of ICAO radio frequency interference guidance material.

    1. That WG-B determine the need to update ITU-R SM.1009-1 “Compatibility Between the Sound-Broadcasting Service in the band of about 87-108 MHz and the Aeronautical Services in the band 108-137 MHz.”

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