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ACP-WGW01/WP-01
/
International Civil Aviation Organization
WORKING PAPER / ACP-WGM16/WP-02
04/23/10

AERONAUTICAL COMMUNICATIONS PANEL (ACP)

SIXTEENTH MEETING OF THE WORKING GROUP M

Paris, France 17 – 19 May 2010

Agenda Item 5: / Maintenance of VDL Mode-2 Documents

Updates to Amendments to ICAO Doc 9776

(Presented by Rob Morgenstern, MITRE)

SUMMARY
This working paper proposes updates to pending Amendment proposals 303 and 304 to ICAO Doc 9776 based on recent activity within RTCA SC214/EUROCAE WG78 VDL Subgroup.
ACTION
The working group is invited to consider the changes for incorporation into Document 9776, Manual on VDL Mode 2.

1.  INTRODUCTION

1.1  The joint RTCA SC214/EUROCAE WG78 has spawned a subgroup to deal with updates to VDL Mode 2 MASPS and MOPS, primarily for the multiple frequency updates made in AEEC Specification 631-5 with errata. As part of this group’s development of MASPS updates, the relevant amendment proposals to ICAO Doc 9776 were reviewed.

2.  discussion

2.1  AP304 proposes changes to Doc 9776 to define support for AOA and FIS-B over the VDL Mode 2 service. The proposed change to AP304 adds a new state for ‘No Service’ to the AVLC-specific options parameter. This allows the ground service provider to indicate that an operating radio station is not currently connected to the network and the aircraft should not use the station. Updates to the AP are as below:

Amendment Proposal #304

Title: / Network Identifier
AP working paper number and date / M13/WPx 18 Nov 2008
Document(s) Affected: / Manual on VDL Mode 2 Technical Specifications
Document Version: / Doc 9776
Sections of Documents Affected: / 6.1
Coordinator: / Robert Morgenstern
Coordinator's Address: / 7515 Colshire Drive, M/S N660
McLean, VA 22102
USA
Coordinator's Phone: / +1 703 983 7846
Coordinator's Fax: / +1 703 983 1367
Coordinator's E-mail Address: /
Category: / BUG
Problem description: / Defines support for AOA and FIS-B over VDL2. The generic interface also readily supports the addition of IP or other networking services, if deemed appropriate.
Background: / Most aircraft using VDL2 are using AOA. This defines the method in the standard, so as to ensure interoperability.
Backwards compatibility: / Already implemented.
Amendment Proposal: / See below.
WG-M Status: / SUBMITTED 11/18/08
UPDATED 5/17/10

5.4.2.4.5 AVLC specific options parameter. This parameter defines which AVLC protocol options are supported by the transmitting station. It shall be encoded as per Tables 5-15 and 5-16. An LME shall set the reserved bits to 0 on transmission and shall ignore the value of these bits on receipt. When both this parameter and the Connection Management parameter are included in an XID, the bit values for those options which are included in both parameters shall be determined by the Connection Management parameter.

A ground station advertises the operational state of available services in it's GSIF through the use of the AVLC Specific Options parameter and the ATN Router NETs parameter. Possible states for available services are:

• VDLM2 8208 only

• non-VDLM2 8208 only

• VDLM2 8208 plus non-VDLM2 8208

• No Service

The VDLM2 8208 only state is indicated by setting bit 6 (“a” bit) of the AVLC Specific Options parameter to zero and encoding at least one non-zero parameter value in the ATN Router NETs parameter.

The non-VDLM2 8208 only state is indicated by setting bit 6 (“a” bit) of the AVLC Specific Options parameter to one and encoding one all-zeros parameter value in the ATN Router NETs parameter.

The VDLM2 8208 plus non-VDLM2 8208 state is indicated by setting Bit 6 (“a”) of the AVLC Specific Options parameter to one and encoding one non-zero parameter value in the ATN Router NETs parameter.

The No Service state is indicated by setting Bit 6 (“a”) of the AVLC Specific Options parameter to zero and encoding one all-zeros parameter value in the ATN Router NETs parameter.

If the aircraft station sets bit 6 (“a” bit) of the AVLC Specific Options parameter to zero, it is requesting VDLM2 8208 service. If the aircraft station sets bit 6 (“a” bit) of the AVLC Specific Options parameter to one, it is requesting non-VDLM2 8208 service (such as AOA).

Add New:

6.1.2 Generic Network Access

The VDL Mode 2 system is capable of supporting multiple network protocols over AVLC (link layer), enabling ATN services to coexist with other network types, such as AOA, over the VDL Mode 2 media. The data link layer frame can carry any defined packet type, with a signature component for the host to differentiate between different types of frames. This signature component identifier shall be in accordance with ISO/IEC TR 9577 and its use of the Initial Protocol Identifier (IPI) and Extended IPI (EIPI), as needed. The ISO 9577 IPI byte encoding of all-ones (0xFF) is reserved by ISO/IEC TR 9577 to allow for the specification of additional subnetwork protocols beyond those explicitly defined in the ISO document. When this form of IPI encoding is employed, a second octet (the Extended Initial Protocol Identifier (EIPI)) is used to specify the actual subnetwork protocol in use. The IPI followed by the EIPI octet shall be contained at the beginning of the User Data field as defined in Figure 5-1. If the link is configured with the “a” bit of the AVLC options parameter set to one, then the user data field of Figure 5-1 shall include the IPI/EIPI fields and non-8208 user data. If the link is configured with the “a” bit of the AVLC options parameter set to zero, then the user data field of Figure 5-1 shall include ISO 8208 user data.

6.1.2.1 ACARS Over AVLC (AOC). AOA is a service that encapsulates ACARS messages with an AVLC frame for transmission over the VDL Mode 2 system. AOA is provided as a service to the current users of the datalink services to support the increased demand and to promote a smoother transition to the full ATN service. For AOA operation, the IPI shall be encoded as 0xFF and the EIPI shall be encoded 0xFF indicating ARINC 618/620.

6.1.2.2 Flight Information Service – Broadcast (FIS-B). Flight Information Services-Broadcast (FIS-B) is an automated, media-independent digital data link system that provides non-control, advisory information needed by pilots to operate more safely and efficiently in the airspace. FIS provides to pilots the necessary weather graphics and text, Special Use Airspace (SUA) information, Notices to Airmen (NOTAMs), and other information.

This broadcast data provides connectionless unacknowledged protocol services. This broadcast data link service supports efficiency in spectrum use since there is no need to separately transmit the same information to multiple receivers.

One of the FIS-B media is the VDL Mode 2 subnetwork; consequently, there’s a need to uniquely identify this service from other services that are or might be carried by VDL Mode 2, such as ATN, AOA and future applications.

For FIS-B operation, the IPI shall be encoded as 0xFF and the EIPI shall be encoded 0xFE within a VDL Mode 2 UI frame to uniquely identify a FIS-B message in accordance with the recommendations of ISO/IEC TR 9577.

2.2  AP303 proposes changes to Doc 9776 to add multi-frequency operation. AP303 included the proposed changes from AP304 since it also modified the same section. With the modification to AP304, AP303 should be modified accordingly for section 5.4.2.4.5. There is also an editorial update to 5.4.4.6.8.2 and a change to 5.4.4.11.2.1 to replace ‘XID requesting an autotune’ with ‘XID containing an autotune parameter’. An update to the note to 5.4.4.11.4 replacing ‘hazard’ with ‘complication’ since the word ‘hazard’ has meaning in aviation that was not implied here. A similar replacement of ‘hazard’ with ‘complication’ is made in the text of 6.2.4.2. There are also 2 ‘should’s replaced with ‘shall’s, which were erroneously left from the source AEEC document which uses should exclusively.

Amendment Proposal # 303

Title: / Multi-Frequency Operation
AP working paper number and date / M13/WPx 18 Nov 2008
Document(s) Affected: / Manual on VDL Mode 2 Technical Specifications
Document Version: / Doc 9776
Sections of Documents Affected: / 5.4.2.4.5, 5.4.2.7, 5.4.4, 6.2.4, Table 5-16, Table 5-19
Coordinator: / Robert Morgenstern
Coordinator's Address: / 7515 Colshire Drive, M/S N660
McLean, VA 22102
USA
Coordinator's Phone: / +1 703 983 7846
Coordinator's Fax: / +1 703 983 1367
Coordinator's E-mail Address: /
Category: / BUG
Problem description: / The autotune specification is insufficient to guarantee interoperability, as well as does not cover some failure modes
Background: / Link 2000 projections place the need for a second frequency in Europe in the 2009-2011 timeframe. The US envisions the need for multiple frequencies shortly after Segment 1 operations begin. As such the specification needs a viable multi-frequency capability.
Backwards compatibility: / Autotune will still function, but some failure modes may not be covered.
The FSL-based frequency management scheme was devised such that older implementations would just not change to the new frequency.
Amendment Proposal: / See below.
WG-M Status: / SUBMITTED 11/18/08
UPDATED 5/17/10

See Attached M13WP14ter for proposed updates.

3.  ACTION BY THE MEETING

3.1  The ACP WGW is invited to incorporate the changes to AP303 and AP304 to ICAO Doc 9776.