Airport Vehicle Position System (AVPS)

AMCP/WG-C5/IP…

AERONAUTICAL MOBILE COMMUNICATIONS PANEL (AMCP)

WORKING GROUP C5

Kobe, Japan

15-25 October 2002

Agenda Item

Airport Vehicle Positioning System

(Development of Multi-ChannelAirport Surface ADS System)

Presented by Shuuji Takahashi

Prepared by Shiro Nihei

INFORMATION PAPER

Airport Vehicle Positioning System

(Development of Multi-channelAirport Surface ADS System)

Shiro Nihei

Electronic Navigation Research Institute

Independent Administrative Institution

1. Introduction

For the future aircraftsurveillance, an introduction of Automatic DependentSurveillance (ADS) system is being proposed, and the ADS system will utilize data link and precisionpositioning system such as GNSS inplace of radar. The introduction of the ADS system is also being studied for surveillance of such mobile objects as aircraft and vehicles around an airport and on the airport surface so that the safety and efficiency of airport operations can be improved.

In Electronic Navigation ResearchInstitute (ENRI), we are developing and experimenting with an airport surface ADS system that will perform surveillance of such mobile objects as aircraft and vehicles in an airport. A prototype system so far developed is capable of processing approximately 300 mobile objects when a position update rate of the system is once per second. In fiscal year (FY) 1999, we developed using this system an “Airport vehiclepositioning system” that can control mobile objects within an airport and perform data communications with them, and installed the system in NewChitoseAirport. In FY 2000 and 2001, we did performance evaluation tests and confirmed successfulsurveillance of mobile objects moving around the airport .

Since current processing capability is insufficient to support this kind of airport surface ADS system that is also expected to be implemented in larger airports, large increase in the data link communication capacity will be an issue in the future.

In the conventional data link system, only one channel is securely accommodated within the entire bandwidth of ISM (Industrial, Scientific and Medical) radio band at 2.4 GHz. Since October 1999, the ISM radio bandwidth has expanded about three times wider than the previous bandwidth, and thus it becomes capable of accommodating three channels of the data link. With this, the communication capacity can largely be expanded.

Accordingly, we made a prototype multi-channel airport surface ADS system in which the conventional time-division cell-type data link and the frequency-division communication cell are combined, and tested its basic performance at NewChitoseAirport. The summary of the prototype is reported in the followings.

2. Summary of multi-channel airport surface ADS system

In the conventional radio communication network, interference between cells has been avoided by sequentially time-dividing one channel of ISM radio band in order to establish the cell-type data link.

In this network, the number of time division can not be increased significantly because the ratio of communication control signals to the amount of data communications will increase as the number of time division increases and this causes the deterioration of the data transfer rate. In addition, it is required to keep distance between cells long enough in order to avoidinterference among the cells when trying to set up the multiple numbers of cells in which data will be sent in the same period of time. This constraint of keeping the distance long makes it difficult to use the conventional network in such relatively small areas as airports in order to increase the communication capacity.

However if it is possible to accommodate the multiple channels in the cell-type data link then the constraint in setting up cells can be relaxed because there will be no mutual interferencebetween the cells in the different channels. The appropriate combination of channel-division and time-divisionsystems will enable the communication capacity of the cell to increase significantly.

Figure 1 shows an example of the data link with three channels, the frequency of which is different from each other. Each channel has its control station A, B and C respectively that control its own data link, and three control stations have base stations A1 through An, B1 through Bn and C1 through Cn respectively that constitute the communication cells.

Figure-1 Concept of multi-channel ADS System

Figure 2 is a timing chart showing the changes of communication cells that are switched sequentially with the time division. In this chart, the numbers of cells in each channel are three.

In this system, the control station in each channel supervisesmobile objects and controls entry and exit of mobile objects between cells in the same way as the conventional system does while the mobile objects are in the same channel. To control entry and exit of mobileobjects between cells in different channels, a master control station is introduced to supervise and control the control stations in each channel, and thus the master control station can control all the control stations and monitor all the mobile objects within the system. Thus, it becomes possible to control entry and exit of mobileobjects between cells in different channels.

Figure-2 Timing chart

Figure 3 shows an example of cell layout where the numbers of channels and of time division are three. Compared to the conventional data link that accommodates one channel, this method can provide more flexible cell layout and wider area to be covered by many cells that are mutually free from interference, and this will result in significant increase of the processing capacity.

Figure-3 Cell layout example of multi-channel ADS system

3. Configuration of prototype System

Figure 4 shows configuration of the prototype multi-channel experimental ADS system compatible with the new ISM band (2400 through 2483.5 MHz). This system has a hierarchical structure of three layers that are composed of a control station, base stations and mobile stations.

Figure-4 Configuration of prototype multi-channel ADS system

(1) Control Station

The Control Station, which is the core of the system, is composed of a File Server, a Super Organizer, Channel Organizers, a GPS Station, an Observer and LAN equipment that includes a HUB.

The Super Organizercontrols operations of each radio channel, has user interfaces to set up the Base Stations to be operational, channel operation conditions and etc., and supervises relations between all the Mobile Stations and Base Stations in real time.

The Channel Organizer is installed in each radio channel, and controls operations of Base Stations in that channel. The operation control method used in the Channel Organizer is the same sequentialswitching of the Base Station as used by the conventional data link method that accommodates one channel.

(2) Base Station

The Base Station includes radio data communication equipment that can process three channels. The frequencychannel is arbitraryselectable but is normally fixed to operate the same way as conventional Base Station operations. The number of Base Stations can be increased to a maximum of 15 stations in one channel.

(3) Mobile Station

The Mobile Station is composed of radio data communication equipment that is same as the Base Station, a GPS receiver used as position sensor of the Mobile Station and a moving map monitor to display the location of that Mobile Station. (The monitor is a 12-inch SVGA LCD panel with touch panel function.) During operation, the frequency of the channel is changed dynamically to the frequency of the connecting Base Station.

The Mobile Station, while it is in service of one Base Station, operates in the same conventional way, and also utilizes GPS position information to see if it is leaving or entering the service area of that Base Station. However when entering the area that is in another channel the Mobile Station will switch the channel.

Table-1 summarizes the major performance of radio section in the radio data communication equipment.

Figure-5 shows the location of Base Station & tracks of fire engines night test run (July 25,2002).

Table-1 Major performance of radio section in radio data communication equipment

(a) Location of Base Station (M1 through M6) & Tracks of Fire Engine Night Test Run

(b) Example Expression of Tracks

Figure-5 Tracks of Fire Engine Night Test Run (July 25,2002)