MOON Central Monitoring Server

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CMS Key Features

A systematic screening and analysis of VDL MODE 2 traffic would involve considerable human efforts if it were not automated, and it would not be error free. Consequently the CMS is provided with a set of mechanisms that allows automatic traffic supervision. Using the CMS, a MOON user can either consult all captured characteristics of the traffic, request traffic from specific date and any RMU or sets of RMUs, or focus on various situations that the CMS can automatically detect. These features are described hereafter.

CMS user interface (HMI)

All the MOON CMS functionalities described hereafter such as MOON traffic consultation are accessible using a single and intuitive WEB 2.0 interface. Practically speaking a regular web browser such as Internet Explorer 9 or Firefox 3 will be sufficient. MOON CMS is accessible using a regular Internet address beginning with HTTPS:// and no IT specific task should be required. In other words if an IT department allows standard Internet consultation within its premises, then the MOON CMS should be accessible inside these premises by default.

Traffic consultation

Outside of any data processing, the CMS also simply allows the consultation of any traffic captured on the RMUs that are within the user scope of control. The associated VDL mode 2 traffic can be exported in various data format including simple text export. A user may request the traffic using the following criteria:

  • Specific date/time
  • Specific RMUs or the traffic of ALL RMUs (or all local RMUs in the case of ANSP) merged in one export.

Tracker creation

The MOON captured traffic is automatically and exhaustively decoded by the CMS. Using specific filters, it is then possible to track a specific event. These filters are flexible enough to track almost any situation involving one or more transmissions. The filtering feature in the CMS is also called “Tracker” and is used for an automatic surveillance of the traffic involving almost none human intervention. The events collected by MOON trackers can then be either notified to users using alarms or used as an input for the statistic module.

Alarm generation

Using the CMS alarm notification, a user or a set of users can be automatically notified if an issue followed by a tracker occurs. Two notifications methods are currently supported

  • Automatic mail generation, with a link allowing to download automatically the associated traffic
  • The automatic call to a user defined internet page, allowing seamless integration between MOON and another existing bug tracking tool.

The following picture depicts this relationship between Trackers and alarms.

Relationship between tracker and alarms


Thanks to Trackers and Alarms, the implementations specific issues can be reliably monitored. But for a more general picture of the VDL mode 2 operation and in order to anticipate potential issues, the MOON CMS also incorporates a generic statistic module. This component provides both generic purpose statistics and some more specific statistics that can be generated on top of trackers. These statistics can be presented in tabular form and be exported in CSV for direct usage with MSExcel or presented in chart to be pasted in a report. Here follows a non exhaustive list of available statistics:

  • Evolution of the number of new aircraft equipped seen by week, month and year
  • Average frequency usage by RMU, seen by week, month and year.
  • Average, min and max channel load seen by week, month and year
  • Average, min and max VDL MODE 2 and CPDLC round trips
  • Per aircraft statistics, such as the average number of retransmissions
  • Per tracker alarm such as number of frame rejects per day, week, month …

Here follows an example of the AVLC average retransmission rates during 1 typical day in Brussels airport.


MOON in a multi-frequency environment

As VDL Mode 2 usage grows, several additional channels will be deployed across Europe. The VDL Mode 2 standards have been updated to reflect this necessity and MOON design is made to extend MOON to handle additional frequencies as they will be deployed. The existing RMUs can be extended to support the simultaneous monitoring over several channels and the trackers also can detect issues happening among several channels. Additionally all the statistics can be developed for a multi- or single-channel scope.