Proposed ICAO 5B contribution on Space based ADS-B PDNR ...€¦ · Web viewRadiocommunication Study Groups. Source:Document 5B/TEMP/210. Annex 32 toDocument 5B/475-E. 23 December

[Editor's note: Interference environment, relations of this application with incumbent systems/application need to be clarified. The structure of the report needs to be reviewed to avoid having similar structure to a CPM Text. Should such a report aim to be a candidate for agenda item at future WRCs, careful consideration of the report would therefore be required]

In this contribution, changes are only proposed in Sections ?? xxx No changes are proposed in other sections.

1 IntroductionSurveillance plays an important role in air traffic management. The ability to accurately determine, track and update the position of aircraft has a direct influence on the minimum distances by which aircraft must be separated (i.e. separation standards), and therefore on how efficiently a given airspace can be utilized. In areas without electronic surveillance, air traffic management is reliant on pilots reporting their position verbally by HF or other means, aircraft have to be separated by relatively large distances to account for the uncertainty in the reported position, either due to delay of receiving the position or the low rate at which the information is updated. The large separation distances required makes for inefficient use of airspace.

Conversely, in areas where electronic surveillance systems are used and aircraft positions are updated frequently, the airspace can be used more efficiently by safely accommodating a higher density of aircraft through reduced separation minima. In this way, surveillance capability provides an indication of any unexpected aircraft deviation from track and is an important safety function in the management of airspace.

/TT/FILE_CONVERT/5F89A6027E6DFA50393F8BEB/DOCUMENT.DOCX 17/03/2014 20/12/2013

Radiocommunication Study Groups

Source: Document 5B/TEMP/210 Annex 32 toDocument 5B/475-E23 December 2013English only

ICAO

Proposed Revision to

WORKING DOCUMENT TOWARDS A PRELIMINARY DRAFT NEW REPORT ITU-R M.[ADS-OCEAN] ON EXPANDING THE OPERATIONAL BENEFITS

OFAUTOMATIC DEPENDENT SURVEILLANCE BROADCAST TO OCEANIC AND REMOTE AREAS WITHOUT GROUND INFRASTRUCTURE

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Accurate surveillance can be used as the basis for automated alerting systems. The ability to accurately track aircraft enables air traffic control (ATC) to be alerted when an aircraft is detected to deviate from its assigned altitude or route, or when the future positions of two or more aircraft are predicted to fall below minimum acceptable separation standards. Alerts may also be provided when the aircraft strays below the minimum safe altitude or enters a restricted area.


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With improved navigation performance on board aircraft, airspace users are demanding greater flexibility to determine the most efficient routes to satisfy their operating conditions. Considering the oceanic airspace environment, airspace users are moving towards the use of electronic surveillance and for restrictions associated with flying along fixed routes to be lifted.

In such an environment, accurate surveillance is necessary to assist controllers in the detection and resolution of any potential conflicts associated with the flexible use of airspace which will result in a more dynamic and efficient operating environment.

2 Types of surveillanceBeyond the traditional form of primary radar surveillance, there are the ground based interrogator and aircraft transponder systems which can provide the air traffic management system with aircraft ident, altitude, ground speed etc. These systems known as secondary surveillance radar are all internationally standardised by ICAO and transmit and receive in the 960 – 1 164 1 030-1 090 MHz band. All transponder equipped aircraft can be interrogated by terrestrial ground stations on 1 030 MHz which requests a reply from the aircraft on 1 090 MHz with standardised information that is used by air traffic management. More recently, ICAO’s vision of enhanced surveillance capabilities has resulted in development of an extended data message system in Mode S transponder, and further in Mode S Extended Squitter that provided an additional data message length capability. These systems operate in conjunction with ground based surveillance interrogators. The ground interrogators must be linked to an air traffic management facility for processing of the received aircraft data that is used to provide appropriate airspace management and separation of aircraft.

A more recent surveillance technology has also been developed and standardised by ICAO that does not require interrogations from a ground based system. The airborne system is known as Automatic Dependent Surveillance Broadcast (ADS-B)

3 Terrestrial Automatic dependent surveillance-broadcast conceptAutomatic dependent surveillance-broadcast (ADS-B) is the aircraft broadcast of its position (latitude and longitude), altitude, velocity, aircraft ID and other information obtained from on-board avionics systems. Every ADS-B position message includes an indication of the quality of the data which allows air traffic management to determine whether the data is of sufficient integrity to support the intended function.

The aircraft position, velocity and associated data quality indicators are usually obtained from an on-board GNSS. Current inertial navigation sensors can also provide a portion of the required accuracy and integrity data. ADS-B position messages from an inertial system are therefore usually transmitted with a declaration of lesser accuracy or integrity. However, more recent aircraft installations use an integrated GNSS and inertial navigation system to provide position, velocity and data quality indicators for the ADS-B transmission. These systems have better performance than a system based solely on GNSS, since inertial and GNSS sensors have complementary characteristics that when combined together can mitigate any potential dilution of position accuracy of each system. Altitude is obtained from the pressure altitude encoder (also used as the data source for Mode C replies).

Since ADS-B messages are broadcast on 1 090 MHz, they can be received and processed by a standardized aeronautical receiver. As a result, ADS-B supports both ground-based and airborne surveillance applications. For ADS-B surveillance, ground stations are deployed to receive and process the ADS-B messages. In some countries, there has been deployment of ADS-B ground stations where typical radar station installations are not feasible or possible. The area of coverage required is dependent on the number of ground stations. As an example of the coverage which can


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be achieved, a remote area not covered by radar, the installation of approximately 5 ADS-B ground stations would provide coverage for over 850,000 square kilometers of aircraft surveillance. In airborne applications, aircraft equipped with ADS-B receivers can also process the messages from other aircraft to determine the location of surrounding traffic in support of applications such as the cockpit display and traffic information (CDTI).

Some of the capabilities of ADS-B are:a) the ground station is simpler than the stations of primary radar, secondary radar and

multi-lateration. For a single ADS-B site, acquisition and installation costs are significantly lower. In many instances, the installation can be accommodated at navigation aid sites or sites with existing communications infrastructure;

b) each position report is transmitted with an indication of the integrity associated with the data, allowing users to determine which applications the data can support; and

c) ADS-B supports both ground-based and airborne surveillance applications.

A schematic diagram of ADS-B is shown in Figure below for terrestrial use:

Similar to radar, a limitation of ADS-B is that aircraft transmissions cannot be received beyond line of sight from a terrestrial station for processing and use by air traffic management. The propagation constraints with a terrestrial system prohibit coverage to much of the oceanic airspace, and makes coverage impractical for transpolar and other remote or underdeveloped regions. Therefore it can be seen that many areas of the world cannot be practically covered using terrestrial ADS-B stations to receive aircraft transmissions and provide the data to air traffic management. There are vast regions of the world that can be reached only by using satellite communications. The concept of ADS-B via satellite has been considered and is the only communications mechanism that has the capability to provide complete global coverage to support ADS-B beyond the present terrestrial limitations.


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4 Automatic dependent surveillance-broadcast concept via satelliteCurrently there is a space-based system under development which could use are satellite based ADS-B receivers capable of operating from on a low earth orbiting (LEO) polar orbiting satellites system tthato would provide the opportunity for true global coverage and overcome the aforementioned limitations of terrestrial ADS-B ground stations. The planned objective is to have ADS-B receivers installed as a hosted payload on each satellite in a LEO constellation. during constellation replenishment of the 66 HIBLEO-2 system. Such a An example LEO system with 66 satellites in 6 planes would provide full global coverage. The altitude of the satellites would be is approximately 780 Km providing making it low earth orbit with lower latency than from geo-stationary satellites.

The program is expected to begin first launch in 2015 and continue until completion of its 66 satellites launch campaign in the 2017 timeframe. The HIBLEO-2 Such a system wouldill complement the land surveillance infrastructure and provide continuous global coverage of the Earth including the Polar regions. The ADS-B data, such as position, velocity and message integrity from aircraft wouldill be received by the satellite ADS-B receivers and will be routed via secure cross-link architecture connecting the satellites then to a terrestrial gateway station, before being transferred to terrestrial data networks for availability to air traffic control for processing.

FIGURE 1

Hibleo-2 global satellite network

The above figure is deleted.

[Chairman’s note: need to remove the reference to agi from the above image]


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Upon completion of the satellite constellation deployment in the 2017 timeframe Tthe system will receive aircraft positional information embedded in the ADS-B messages for all transoceanic and transpolar regions as well as from aircraft in other remote or underdeveloped regions where terrestrial ADS-B stations do not exist. The aircraft ADS-B data is expected to be transmitted in near real time to area air traffic control facilities. The satellite ADS-B system will be able to extend and augment the air navigation service provider (ANSP) terrestrial network ADS-B systems to oceans and remote regions on a global basis and in a seamless manner.

Space-based automatic dependent surveillance-broadcast architecture

A potential implementation of The proposed implementation of the satellite-based ADS-B capability over the HIBLEO-2 system is described in Figure 12. ADS-B receivers located on each satellite would receive the signals broadcast from each aircraft within line of sight (the low-Earth orbit enables the satellites to reliably detect the ADS-B signals with no modification to the aircraft equipment). The ADS-B data from all aircraft would be routed and down-linked to a Hosted Payload Operations Centre (HPOC) and aggregated. The pre-processed data from the HPOC could be integrated into existing ADS-B ground infrastructure for further processing and analysis, and then forwarded on to the appropriate ATC/ATM centres and airlines.

The Figure 12 below provides a summary of how the satellite ADS-B system could integrate with a typical terrestrial ADS-B system.

FIGURE 12

Concept of operations

Implementation of athe polar orbiting LEO satellite-based ADS-B capability as shown in the above figure wouldill provide total global communications coverage to all points on the earth.).


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5 Automatic dependent surveillance-broadcast concept summaryThe LEO satellite-based ADS-B system described above will offer a transformational capability to air navigation service providers and airlines all over the world. By extending ADS-B coverage globally, it can complement the terrestrial ADS-B deployment and rapidly enhance air transport safety and efficiency. Most importantly, it will allow integration of received surveillance data from oceanic and remote regions with data from terrestrial ADS-B networks to provide global coverage and a worldwide surveillance picture.

6 Operational environment and mitigation techniquesThere are some operational considerations related to reception of ADS-B signal at the satellites. These are distinguishing the ADS-B signals from other aeronautical system signals operating in the band (unwanted signals), such as Secondary Surveillance Radar (SSR) interrogators, and mitigation measures that may be taken to improve signal discrimination and detection.

6.1 Operational environment

First, in the global areas where the satellite component can usefully augment the use of ADS-B signals from aircraft it is expected that there would be little unwanted signals as the satellites would only be receiving wanted signals from aircraft that transverse oceanic and remote (polar) regions of the world. However, there can be significant unwanted signals in terrestrial areas of high interrogator density.

The main source of unwanted signals comes from aircraft responding to ground based secondary surveillance radar interrogations such as Mode-S, and Air Traffic Control Radar Beacon System (ATCRBS), as well as from Traffic Collision Avoidance System (TCAS) interrogations. The high density interrogator operational environment in North America was used as a test bed to develop mitigation techniques in order to meet stringent applicable performance requirements.

6.2 Mitigation approaches

There are techniques to be used to mitigate unwanted signals in areas of high interrogator density. These include signal processing, spatial filtering, and temporal antenna beam management.

Signal Processing- an Advanced Receiver design uses a non-coherent matched filter with bit decision algorithms. The enhanced satellite receiver provides a higher performance than the terrestrial specified receiver.

Spatial filtering- through maximizing the use of overlapping beams (from the same satellite or adjacent satellites) it is possible to position the beam coverage in such a way as to reduce reception from aircraft in areas with a high density of interrogators. In addition, the beams can also be deactivated or reshaped to accomplish the same purpose.

Beam Management- All of the 32 beams/8 receivers on each satellite cannot be used at the same time. However, they can be managed in such a way as to ensure that the position message update intervals of 15 seconds can be maintained. In addition the probability of detection can be enhanced significantly.

7 Receive Status Studies to be performed[Editor's Note: This section will address the need to perform compatibility studies associated with the satellite reception of ADS-B, if any.]


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The satellite component of ADS-B would operate on a receive only basis and thus would not impact incumbent services. Considering that the frequency 1 090 MHz is used allocated exclusively for the use of aeronautical systems, the frequency band is not available for use by non-aeronautical systems. Accordingly, the aeronautical systems operating at this frequency in this portion of the band are standardised by ICAO, compatibility amongst these systems is assured. Further, sSince the aircraft ADS-B transmissions already exist, satellite reception of these signals does not is not anticipated to require any compatibility study.

8 Operational efficiencies Status from the expanded use of satellite detection of automatic dependent surveillance-broadcast in oceanic and remote regions

Using the North Atlantic as an example of the most dense oceanic airspace with an average of 1000 flights per day, procedural aircraft separation standards are used, whilst providing the necessary safety of air traffic, the structured NAT OTS (North Atlantic Tracks Organised Track Structure) is limited due to the lack of positive radar or ADS-B surveillance availability to air traffic management, the end effect of fixed aircraft altitude and mach speed, results in inefficiencies for airlines and other users.

Although a number of fixed trans-Atlantic tracks exist, the bulk of air traffic operates on tracks, which vary from day to day dependent on meteorological conditions and planning. The variability of the wind patterns renders the fixed track system unnecessarily penalising in terms of flight time and consequent fuel usage. Nevertheless, the volume of traffic along the core routes is such that a complete absence of any designated tracks (i.e. a free flow system) would currently be unworkable given the need to maintain procedural separation standards in airspace largely without radar or ADS-B surveillance coverage.

Airlines are requesting more fuel-efficient flight profiles and routes that will reduce operating costs and show a return on operator investment in aircraft and avionics. It is envisioned that applying reduced separation is expected to enhance the provision of fuel-efficient profiles, altitudes and routes with minimal change to the overall NAT operations.

Advancements in aircraft design, avionics and air traffic management flight data processing systems are currently driving analysis of whether the lateral separation standard in the current NAT airspace can be reduced to increase the number of tracks available and therefore increase capacity at optimum flight levels. Under future consideration, is the potential to reduce lateral separation for aircraft operating at the flight levels associated with the NAT airspace, which can be practically achieved by establishing tracks which are spaced by ½ degree of latitude. Satellite reception of ADS-B aircraft surveillance has the capability to fully support this initiative to achieve reduced separation minima, expand capacity, while the required levels of safety are maintained.

From the perspective of traffic management flow, aircraft surveillance coverage in the NAT airspace would also contribute to efficiencies in domestic traffic flow at major airports due to improved traffic sequencing and merging. Moreover, the efficiency benefits to air traffic management in extending ADS-B coverage on a global basis bringing forth fuel savings, better cost predictability to the airlines, reduced GHG’s, shorter flight duration and optimum routing collectively contribute to a more sustainable global aviation system. The benefits described using the NAT as an example, are also anticipated to accrue in other oceanic regions including the Polar regions.


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9 Assessment of Operational Efficiencies

Text to be developed:

The Table 1 below sets forth the spectrum structure for the provision of the ADS-B service on a fully global basis. It indicates the frequencies utilized by the HIBLEO-2 non-GSO MSS satellite system and the frequency used for the implementation of ADS-B which would have equipment on-board the satellites for its reception.

All of the frequencies in this table are supported by appropriate allocations in Article 5 of the Radio Regulations. The ADS-B transmissions are in the Aeronautical Mobile (route) Service.

The transmissions require approximately 2 MHz of bandwidth within the indicated allocation, and centred on 1 090 MHz. The feeder links and Cross links are in the fixed-satellite (FSS), and inter-satellite (ISS) services, respectively. They are presently being used to support the MSS satellite service links which have an AMS(R)S allocation status under RR No. 5.367. Consistent with that application, and FSS links used at 4/6 GHz and 11/14 GHz to support feeder-links to safety services, those ISS and FSS feeder-link frequencies do not require any special status. As such, ADS-B traffic carried in ISS, MSS or FSS bands would have the same regulatory status as those currently afforded by the MSS, FSS or ISS allocations regarding priority in transmission or protection from interference from other services. However, since satellite reception of ADS-B has not been done before, and considering that the aircraft to satellite uplink would be a safety service, the ADS-B satellite receiver requires some clarification regarding its regulatory status.

TABLE 1

Satellite system spectrum utilization

Link Purpose Frequency ADS-B Uplink Aircraft to satellite ADS-B signal 1 090 MHz +/- 1 MHz

Satellite Ka-Band Downlink Satellite to ground for downlink of ADS-B data and payload telemetry

19.4-19.6 GHz (FSS primary allocation)

Satellite Ka-Band Crosslink Satellite to satellite for relay of ADS-B data, payload telemetry, and command and control of the ADS-B payload

23.18-23.38 GHz (ISS primary allocation)

In the frequency band 960–1 164 MHz, the ADS-B application operates as a terrestrial radiocommunication service under the aeronautical mobile (R) service (AM(R)S) where both the aircraft stations, and ground station transmissions and reception are operated.

When considering the space-borne receiver onboard a satellite that is receiving transmissions from aircraft earth stations, in the true sense, the terrestrial regulatory status under AM(R)S would not apply to the satellite receiver. It would seem that the only appropriate allocation for the satellite receiver and to provide the appropriate regulatory status to the ADS-B signal being received would be under the AMS(R)S, aeronautical mobile satellite (R) service.

Considering that there is currently no AMS(R)S allocation in the 960–1 164 MHz band it would seem reasonable to propose a regulatory option in a footnote authorising AMS(R)S for the operation of ADS-B aircraft transmissions in the uplink direction to the satellite receiver at 1 090 MHz.


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Further, it would be appropriate to restrict the AMS(R)S authorisation for ADS-B to 1 090 MHz, and to also specify that it is limited to recognised international aeronautical standardized systems.

8.1 Allocation discussion

There are several regulatory possibilities to consider when clarifying the status of the received ADS-B signal at the satellites. The satellites would have receivers capable of receiving the ADS-B transmissions being sent in the existing terrestrial service. The signals are the same as those being transmitted in the terrestrial allocation. The RR Article 5 Allocation Table for the 960-1 164 MHz part of the spectrum is as indicated below in Table 2 along with its associated footnotes.

Table 2

Allocation to services

Region 1 Region 2 Region 3

960-1 164 AERONAUTICAL MOBILE (R) 5.327A

AERONAUTICAL RADIONAVIGATION 5.328


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5.327A The use of the frequency band 960-1 164 MHz by the aeronautical mobile (R) service is limited to systems that operate in accordance with recognized international aeronautical standards. Such use shall be in accordance with Resolution 417 (Rev.WRC-12). (WRC-12)

5.328 The use of the band 960-1 215 MHz by the aeronautical radionavigation service is reserved on a worldwide basis for the operation and development of airborne electronic aids to air navigation and any directly associated ground-based facilities. (WRC-2000)

Consideration A – No Change

It has been suggested that the ADS-B service could be provided without any regulatory change as the received signal is being transmitted in an already authorized service, AM(R)S which is recognized as a safety service.

Consideration B – New Footnote No. 5.328X

Another suggestion is to add a footnote No. 5.328X. Transmissions in accordance with international aeronautical standards on the frequency 1 090 MHz from aircraft stations to satellite receivers in the aeronautical mobile satellite (R) service are authorized when such transmissions are used to extend or supplement the aircraft links.

This would provide status to the ADS-B signal being received at the satellite on the frequency 1 090 MHz. It would seem to be an appropriate provision as ADS-B is considered to be an aid to navigation.

Consideration C – New service

Another suggestion has been to add the AMS(R)S allocation by a new footnote and have it indicate its use for the 1 089-1 091 MHz band. This option would be more demonstrative with respect to the use of the band by the ADS-B signal received by the satellites. Further, it would be appropriate to also specify that it is limited to recognised international aeronautical standardized systems. The following Footnote options would provide for such a new service.

Footnote Option C1

The band [1 089–1 091] MHz is allocated to the aeronautical mobile satellite (R) service on a primary basis for reception of aircraft transmissions by space stations on a worldwide basis as an aid to navigation and is limited to systems that operate in accordance with recognised international aeronautical standards.

Footnote Option C2

The use of the frequency 1 090 MHz in the aeronautical mobile satellite (R) service is authorised on a global basis for reception of aircraft transmissions by space stations as an aid to navigation. Such use shall be in accordance with recognised international aeronautical standards.

Footnote Option C3

The band [1 089–1 091] is also allocated to the aeronautical mobile satellite (R) service (Earth-to-space) on a primary basis for the space station reception of automatic dependant


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surveillance - broadcast (ADS-B) emissions from aircraft stations and is limited to systems that operate in accordance with recognised international aeronautical standards.

10 Summary and Conclusions

119 Glossary of abbreviationsTo be developed.


Documents

Proposed ICAO 5B contribution on Space based ADS-B PDNR ...€¦ · Web viewRadiocommunication Study Groups. Source:Document 5B/TEMP/210. Annex 32 toDocument 5B/475-E. 23 December