ATC System Integration & Interfaces

PAMS retrieves current operational statuses and other information through its interfaces to ground-based aerodrome equipment. SNMP IP communications are used for most modern equipment, and simple switch-to-earth (dry contacts) or volt-free contacts are available for legacy and low-level status monitoring. Time synchronisation across all systems, to track events, is achieved through Master Clock NTP communications. When required, monitoring is also available through PAMS native drivers for a wide variety of manufacturers hardware.

SNMP interfaces are available to either SNMP v2c or v3 standards, according to the capabilities of the third-party equipment. SNMP v2c is simpler to set up but v3 provides more secure communications through encryption and authentication.

Operating over the ATM LAN, managed network switches can be used to further control access and route network traffic between the PAMS Server(s) and aerodrome equipment.

In order to setup an SNMP interface, the equipment manufacturer's MIB and OIDs are required. The MIB (Management Information Base) contains the hierarchical database structure used to hold the status information. MIBs often contain references to other MIBs which means more than one can be required to understand the data structure detail. The OID (Object Identifiers) are the unique numerical addresses within the tree structure that identify each data point (expressed as .1.21.4.1…). Armed with this information, PAMS SNMP drivers can receive not only the current status but other related information from the equipment, such as the frequencies that are being used by the ground to air radios.

ATM equipment is designed to have a long operational life. Therefore, there is often a requirement for PAMS to interface through switch-to-earth (dry contact) or volt-free contacts. Many older airfields already have Krone connectors terminating old telephone-style twisted pair cabling in place, and these are often utilised to provide a reliable connection between PAMS and the ATM equipment.

PAMS can be provided with one or more I/O racks for this purpose. These are typically fitted into an equipment rack alongside the PAMS Server(s), but can also be located anywhere on the airfield (or beyond). Using LAN infrastructure with cat5e/cat6 cabling or fibre optic with fibre to LAN converters, dual redundant PAMS servers can be deployed which can both communicate with the I/O units.

Modern equipment racks also feature dual redundant power supplies that are monitored as part of PAMS self-diagnostics functionality, and are also fitted with temperature monitoring for the equipment rack it is fitted in.

Many airfield systems are now supplied with multiple servers to provide a level of redundancy. For most systems this means just two but in the case of more complex air traffic systems, there may be six or more.

These can all be monitored and rules applied to decide which server(s) to use, what constitutes a communications issue, and ultimately how to determine if an alarm condition has occurred.