AERONAUTICAL COMMUNICATIONS PANEL (ACP)
Eleventh Meeting of Working Group C
Brussels, Belgium. 20-22 September 2006
Agenda Item 3 –Update on ICAO, ITU and industry activities
Information Paper on the activities of
EUROCAE Working Group 67 VoIP for ATM
Presented by
John MacBride
SUMMARY
This information paper provides information and a status report on the work of EUROCAE Working Group 67 – VoIP for ATM.
1.Background
This information paper provides a status update on the activities undertaken by EUROCAE Working Group 67 which is examining the use of VoIP in an Air Traffic Management environment (VoIP for ATM). The final deliverable of WG67, defined within the Terms of Reference, is to develop and define a Technical Specification for an IP voice ATM System.
The Terms of Reference for WG67 were approved in July 2004 by the EUROCAE council.
At the present time the components of Ground-Ground ATM voice systems mainly use digital (TDM/PCM - Time Division Multiplexing / Pulsed Code Modulation) or analogue technology. However there is a large movement towards the convergence of voice and data into one multimedia network by the commercial network providers. It has also been noted by various groups and studies in the past that Voice over IP Technology may fulfil and improve operational and technical ATM communication requirements, and with Pan-European Network Services (PENS) foreseeing integration of ATM IP Voice communications by 2010, it was decided that WG67 would be formed to examine using VoIP in ATM.
The Working Group initially defined the IP Voice ATM Systems and identified their individual components and interfaces (Voice Communication System / VCS, Ground based Radio Station etc.) This agreement was drawn up to form the baseline of the deliverables of the group and was called ‘The Vienna Agreement’.
Currently WG67 does not address the air segment of the link. The boundary of the work is defined from the controller to the ground based radios. There is an acknowledgement in the group that a number of external studies are looking at the air segment of the link.
Members of WG67 include;
European ANSPs, European ATM Suppliers of VCS equipment and Ground Based Radio Systems, FAA, Eurocontrol, Telecom equipment suppliers and Telecom Operators.
2.Objectives
The Deliverables are defined according to the four sub groups of WG67;
- WG67-SG1 - Requirement Sub Group
“VoIP ATM System operational and technical requirements”
- WG67-SG2 - Interoperability Sub Group
“IP standards to fulfil operational and technical requirements” and
“IP interfaces between IP components as defined in the Vienna Agreement”
- WG67-SG3 - Network Sub Group
“Network requirements and performances to fulfil QoS required to interconnect IP components”
- WG67-SG4 - Validation Sub Group
“Validation requirements for VoIP ATM System and Components”
It is anticipated that once the work of the group is complete that the Published EUROCAE documents(deliverables of WG67) will be presented to the ICAO ANC panel for consideration as international recommendations, submitted for consultation by the Civil Aviation Community and available for consideration by both European and International Standardisation Bodies.
3.Status
WG67-SG1 - Requirement Sub Group
A number of requirements papers have been produced by SG1 – an initial ‘fast track’ was made of the well developed and documented ground ground telephone requirements. Separate papers have been produced on other areas including recording, system management, and voice quality.
A System Performance paper was written and includes clear definitions of the components and delay associations with the components. This includes items like voice latency and signaling delay (including cross coupling working). There is a task to produce this baseline model of the current systems in alignment with the COCR.
The final deliverables of SG1 will be complete by the end of 2006 and will include the Air Ground System functional requirements.
WG67-SG2 - Interoperability Sub Group
The work of SG2 concentrates on the technical analysis of the requirements papers produced by SG1. Check the existing specifications and protocols in use in the VoIP world.
The work of SG2 is to propose specifications based on existing IP protocols, recommendations and standards.This work takes into account interoperability with existing signalling (MFCR2ATS-QSIG), compatibility with ground telephone addressing plans and the compatibility/capacity to interface IP systems with existing voice equipment (VCS and Radios).
For the radio requirements the work will address the performances aspects, the need to provide specific functions (e.g. Cross Coupling, BSS and Climax Operation). The work of SG2 is also to look at the security aspects of using VoIP.
One notable area of examinationduring the technical analysis is to ensure the compatibility/capacity to interface IP systems with the existing voice equipment (VCS and Radios).
Currently SG2 propose to use for the Ground Ground Components;
- RTP, RTCP for audio transmission over IP
- G711, G728 and G729 CODEC
- Signalling protocol: SIP as exchange protocol through IP network
Currently SG2 propose to use for the Air Ground Components;
- Audio protocol: Based on RTP/RTCP (RFC 3550),
- Control signalling integrated in RTP signalling,
- Additional information in the RTP protocol (RTP Extender) for PTT and A/C
- Proposed CODEC G711 with or without PLC (Packet Loss Concealment)
There are some difficulties in the proposal for the radio requirements that are being worked on, as there are no fully compliant standards available, these include;
Performance when using VoIP, transmission of additional control signals as “PTT”, “A/C”, which need to be managed, sidetone control and management, Configuration of the radios on remote sites and the availability of the network.
WG67-SG3 - Network Sub Group
The work of SG3 is to develop the network design rules with two deliverables:
- IP Addressing Plan
- Network Design Guideline
Also to develop a technical specification for a VoIP ready network with two deliverables:
- Network Minimum Requirements
- Security Policy
The IP Addressing Scheme work has been totally based on the iPax TF results, which has resulted in a recommendation for the use of IPv6. The recommendation is also made for the migration to IPv6 as early as possible (The Core IP Network could be PENS).
The conclusion on the analysis of the Management Protocols is that SNMPv3 is recommended.
The items of Delay, Jitter, Packet Loss were analysed, VoIP calls must achieve 150ms (or less) to meet the requirements. Typical network delays can be guaranteed to be less than 50ms.
Delay, Jitter and Packet Loss can be controlled by using routers, firewalls, and other network elements that support QoS.
The Current status of the SG3 deliverables are;
The ‘IP Addressing Plan’ has been issued. The ‘Network Design Guideline’ is in draft, The ‘Security Policy’ is in draft, The Specification of ‘Network Minimum Requirements’ draft in progress.
WG67-SG4 - Validation Sub Group
SG4 is developing the guidelines for the validation of ATM VoIP-components and their interoperability in compliance with EUROCAE WG67 requirements and specification documents.
The guidelines will specify the validation in four phases;
Phase 1: Validation tests between IP-Interfaces and existing telephone and radio systems.
Phase 2: Adaptation of Radio & Telephone voice and signaling to existing analogue equipment through an IP network.
Phase 3: Test of a complete Telephone and Radio system through an IP network.
Phase 4: Test of a complete VoIP system using an IP WAN. (As an example using 3 VCS and 3 RCE)
Current status is that the verification guidelines document is in draft.
4.Schedule
The work is scheduled for completion including final versions of all of the deliverables in early 2007.
- Recommendation
The meeting is invited to note the information in this paper.
- 1 -