AMCP WG/WP29

AERONAUTICAL MOBILE COMMUNICATIONS PANEL

Working Group of the Whole Meeting

21-24 May 2002

Montreal, Canada
Agenda Item 4:Proposed development of SARPs for the Universal Access Transceiver (UAT)

VDL MODE 4 SUPPORTING A-SMGCS SYSTEMS

Presented by Larry Johnsson

Prepared by Larry Johnsson and Jens Nilsson

SUMMARY

Advanced Surface Movement Guidance and Control Systems (A-SMGCS) is believed to be one of the main components in the CNS/ATM concept as airport operations are one of the major bottle necks of a flight process from gate to gate, or from en-route to en-rote as it also is referred to. Runway Incursion Warning Systems is also believed to be one of the most important safety nets in future aviation.

To get an indication on how a VDL Mode 4 based A-SMGCS system might behave on a high-density airport, a simulation activity was carried out by LFV during 2001. The goal was to complete the practical information, gained by using the VDL Mode 4 like STDMA systems for several years. This paper is presenting the results of this simulation activity.

1.Introduction

Advanced Surface Movement Guidance and Control Systems (A-SMGCS) is believed to be one of the main components in the CNS/ATM concept as airport operations are one of the major bottle necks of a flight process from gate to gate, or from en-rote to en-rote as it also is referred to. Runway Incursion Warning Systems is also believed to be one of the most important safety nets in future aviation.

Trials with VDL Mode 4 prototypes (STDMA) started on an airport investigating a Runway Incursion Warning function. The VDL Mode 4 system has the capability to provide surveillance, navigation and communication functions, that all are components in an A-SMGCS system. ADS-B will provide position data to all units that are equipped. The navigation component is providing GNSS augmentation data that are essential to increase the accuracy of the navigation and positioning system. The traditional data link can be used for exchange of information and clearances.

How VDL Mode 4 behaves in an airborne scenario has been very well investigated during its standardisation process. Also the behaviour on ground has been investigated but this has been done in practical tests, in an much smaller scale than a fully equipped large airport require, mainly at Stockholm/Arlanda and Göteborg/Landvetter airports in Sweden. These experiments have shown that VDL Mode 4 is well suited for use on an airport.

To get an indication on how a VDL Mode 4 based A-SMGCS system might behave on a high-density airport, a simulation activity was carried out by LFV during 2001 [1]. The aim was to complete the practical information, gained by using the VDL Mode 4 like STDMA systems for several years. This paper is presenting the results of this simulation activity.

2.Simulations

The differences between a ground- and airborne scenario are substantial both with respect to requirements and the propagation of VHF radio waves. Other interesting factors are if the STDMA protocol behaves different in a scenario with very short ranges and high link load.

2.1Radio Model

The differences between ground propagation and free space propagation are investigated in the ICAO AMCP WG-B paper Ground-ground propagation attenuation applicability to VHF frequency planning criteria [2] and the model used in the study was based on the results presented in this paper.

2.2Simulated Scenarios

The scenario was derived from the work done in the NEAN Update Programme (NUP) and presented in the rapport; OED for NUP application: A-SMGCS Paris Charles de Gaulle [3]. Here the maximum instant number of active[1] mobiles on Charles de Gaulle (aircraft + other vehicles) is estimated to 300 consisting of aircraft (100), operational ground vehicles (100) and other vehicles (100).

The concept of sleep mode was used to reduce the link load in the simulations. If a vehicle moves very slow or not at all its VDL Mode 4 transceiver can be set to sleep mode. When in sleep mode the transceiver transmits once every minute on each channel. It also monitors speed or/and distance, both variables that can be set by the base stations. Threshold speed may be in the range of 1 – 15 kts and distance in the range of 1 – 255 meters. If the vehicle moves so that these limits are exceeded it goes back to normal mode. The slots needed when waking up can be reserved on the link safely due to the incremental broadcast procedures [4]. A vehicle can be in sleep mode for many reasons, it can be a jet fuel tanker that refuels an aircraft or a bus filling up/dropping of passengers, an aircraft waiting in a queue for take off (in the so called “congo line”) or at a stop. Simulations were carried out with 75, 50, 25 and 0 percent of the mobiles in sleep mode. The number of monitoring ground stations has been selected to be sufficient for the 50 % scenario, which is considered as the main scenario here.

In the simulations the 300 aircraft/vehicles (A/V) were considered to be spread over a circular area with a radius of 2 kilometres. Each A/V was given either an update period of 1 second divided equally over two channels (i.e. a period of 2 seconds per channel) or are in sleep mode, transmitting once a minute on each channel. Six ground stations were used for surveillance. The number of ground stations has been selected to ensure good coverage in the main scenario. Most of the ground stations can be very simple monitors that are entirely passive. This is due to the fact that a transmitting ground station doesn’t have to share slots with other ground stations or vehicles. They can transmit in the protected slots in the beginning of each second and be synchronized so they don’t garble each other.

3.Conclusions

The study indicated that VDL Mode 4 is a suitable candidate for A-SMGCS as it fulfils the requirements on an A-SMGCS surveillance system [5]. The performance in vehicle-to-vehicle surveillance in the main scenario (50 % active) gives a range of 600 metres with 98% delivery probability. With increased link load the systems performance drops but the system never fails in any of the simulations.

VDL Mode 4 also has several other benefits over other systems. The perhaps most important benefit is that VDL Mode 4 is standardised by ICAO. An ICAO standard ensures interoperability allowing aircraft to be part of the system whatever airport it arrives to. It will be seen by all other vehicles, as well as the air traffic controllers and it will see the other aircraft and ground vehicles it self. Secondly the same equipment can be used for navigation and data communication as well. Compared to ground radar based system, the system always have identification on all vehicles and a simple routing system can replace advanced trackers when more ground stations are added. VDL Mode 4 also allows vehicles to monitor other vehicles at a very low cost.

4.Recommendations

The AMCP WGW meeting is invited to

•note the information in this paperon the capability of VDL Mode 4 to support A-SMGCS systems; and

•consider the importance of ADS-B systems to support A-SMGCS systems.

Refernces

[1] VDL Mode 4 in A-SMGCS; Performance simulations, version 1.0, 24/01/2002, Luftfartsverket.

[2] Ground-ground propagation attenuation applicability to VHF frequency planning criteria. 15-23 jan 2001 Agenda item 3,AMCP WG-B.

[3] OPERATIONAL ENVIRONMENT DEFINITION (OED) for NUP application: A-SMGCS Paris Charles de Gaulle, Version 1.0, 2001-04-02, North Atlantic ADS-B Network Update Programme, Phase 1.

[4] VDL Mode 4 STANDARDS AND RECOMMENDED PRACTICES, Version 6.0.1, 21 January 2000, and Manual on Detailed Technical Specifications for the VDL Mode 4 Data Link , Version 6.0.0, 20 January 2000.

[5] European Manual on Advanced Surface Movement Guidence and Control Systems. Draft version 07, 9 Jan 2001, ICAO.

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[1] Aircraft are considered active from landing until engine stop and from departure clearance until take off. Ground vehicle are considered active from engine start until engine stop.