Mobility Testing Environment for ATM safety communications

Objectives

Within the framework of the Iris programme, the development of end-user satellite equipment on the ground and on-board aircraft will be undertaken. This will require the development of test beds for interoperability testing including functionalities not covered by the satellite communication standard.

In this context, one identified activity is the development of the Mobility Testing Environment (MTE) for the ATM safety communications in order to test the performance of the Air-Ground Router (AGR). The AGR is being produced within a separate ESA funded task and is based on internet protocol suite version 6 (IPv6). AGR is placed at the boundary of the ground network infrastructure of the European Air Traffic Management Network (EATMN). It offers an interface with the Ground Earth Station (GES) of the new satellite communication (SATCOM) sub-network.

As such, the MTE will be realised as a set of SW and HW elements with external IP interface to the AGR (therefore, physically decoupled from the AGR). Therefore, the MTE will allow the verification of the functionality of AGRs from different vendors.

The main objective of the present project is the design and development of a Mobility Testing Environment (MTE) for validation and verification of Air-Ground Router (AGR).

The MTE shall allow the testing of any commercially available AGR along with the customized solution developed under separate ESA contract that comprises an AGR as well as functional enhancements to the AGR called Routing Enhancements for Iris Link (REIL).

It is expected that some parts of MTE may in future be upgraded and used within appropriate ANTARES verification platforms.

Challenges

One key issue in the MTE project will be testing options for extending the period of an interruption-free IP connectivity between moving aircraft and the ATC/AOC ground-based units.

Due to the assumed topology where each GES is served by its dedicated AGR, when the AES moves between GESs, this automatically means changing the L3 point of attachment for the MN(s) served by this AES. Therefore, L2 handover between GESs will trigger L3 handover between associated AGRs. After a break-before-make L2 handover has been initiated, a given MN within the concerned aircraft will be no longer reachable for the ground CNs under its old IP (CoA) address. It may take significant time until MN has configured its new CoA and performed successful registration at HA. Without specific measures taken, this may cause that existing transport sessions between CNs and this MN will break and will have to be re-established when the new CoA becomes registered. MTE shall enable investigating the efficiency of supplementary mechanisms for avoiding connectivity loss during handovers.

Similarly, MTE shall allow for validating supplementary enhancements to the GES switchover in case of primary GES failure, including these for GES status monitoring and implicitly signalling the GES failure to GGR.

Benefits

The development of the MTE enables testing of the AGR and associated REIL functionality within a realistic IPv6 environment and considers the specifics of the satellite-based communication link.

Features

In order to support safety-related ATS services the AGR must support seamless aircraft handovers between coverage areas of Ground Earth Stations (GES) and/or GESs of different service providers, also providing uninterrupted IP connectivity in case of switch-over to redundant GES upon primary GES failure.

The MTE provides a full external IPv6/MIPv6 environment for detailed functional testing of the AGR, including enhancements to the AGR for fast net entry, fast handovers, fast GES switchover and header compression that will be implemented within a separate Routing Enhancements for Iris Link (REIL) unit. Moreover, the MTE will allow for adjusting and testing parameters related to QoS provision and the DiffServ concept.

The figure below shows the MTE components and their relationships to AGR and REIL.


click for larger image

The following components will be produced within the MTE task:

  • Mobile Node (MN)
  • Home Agent (HA)
  • Correspondent Node (CN)

These components will be implemented on standard PC platforms, using standard LINUX features together with necessary supplementary software packages:

  • Ground-ground Router (GGR)

Representative GGR will be purchased as a COTS product and will be configured within the MTE task. Following components will be produced outside the MTE task, but will become “Device Under Test” within MTE:

  • Air-ground Router (AGR)
  • Routing Enhancements for Iris Link (REIL)

Some components of the SATCOM ground segment are external to the MTE task:

  • Network Control Centre (NCC)
  • Ground Earth Station (GES)
  • Aircraft Earth Station (AES)

GES and AES will be neither implemented nor emulated within the MTE task - wired connections will be used between involved MNs and AGRs. Impact of these components as well as mobile channel impact will be taken into account via configurable excess delay for both forward link and return link, configurable packet error rate, as well as by emulating packet loss/duplication/ reordering between MN and AGR.

NCC functionality during GES switchover/AES handover – e.g. detecting GES-AES connectivity changes or GES failure detection – will be emulated up to the necessary extent.

Plan

The project plan comprises 3 tasks as described below:

  • Task 1: Specification of the test framework technical requirements

    The main objective of this task is to capture the technical functional requirements necessary for the development of the MTE. The requirements will be based on ICAO Doc 9896, as well as relevant deliverables of ARTES 10(Iris) and ARTES 1.

    ICAO Document 9896 specifies the standards for the Aeronautical telecommunication network based on IPv6. IETF RFCs deliver the detailed standards for IPv6 protocol suite including mobility management. However, existing RFCs put no particular focus on satellite based communication and are even less concerned with safety-critical ATS services, therefore another objective of this task is to merge and harmonize requirements specified by ICAO and IETF.

    The outputs of task 1 are the Technical Requirements Document (TRD) and Test Plan Document (TPD) that serve as inputs to task 2.

  • Task 2: Development of the test framework

    The objective of this task is to define the SW and HW architecture of the MTE and develop the MTE framework based on the TRD along with related test/validation scenarios defined in TPD. The task comprises development, integration and configuration of all required software modules on LINUX-based PCs.

    Task 2 provides the Software/Hardware Architecture Document (SHAD) as an input to task 3.

  • Task 3: Validation of the mobility test framework

    The main objective of this task is the validation of the MTE test framework according to scenarios defined in TPD. Validation will span all components being produced or purchased under MTE task (MN, GGR, HA, CN).

    TPD and SHAD are inputs to task 3 that will actually produce the MTE and associated documentation: Validation Results Document (VRD) and User Manual (UM), including detailed configuration and installation information. This task will also provide all MTE hardware and software.

Current status

From the beginning of the MTE project onwards, a full set of deliverables has been produced, reviewed and accepted by ESA:

  • Technical Requirements Document (TRD)
  • Test Plan Document (TPD)
  • Software/Hardware Architecture Document (SHAD)

MTE hardware has been configured, required software installed, and required features implemented, followed by the validation activities. Recently, MTE validation – checking the compliance of the MTE implementation with TRD – has been successfully closed. In the course of MTE validation further two deliverables have been produced, reviewed and accepted:

  • Validation Results Document (VRD)
  • User Manual (UM)

Current MTE implementation allows for emulating the SATCOM UT with two radio units (supporting two independent channels between the UT and two different GESs).

The MTE project is completed.

The MTE hardware/software will remain available for subsequent functional enhancements and testing, e.g. for integrated end-to-end tests with real AGR(s). Such tests could significantly contribute to the optimization of various IPv6/MIPv6 adjustable parameters within the challenging SATCOM context.

Contacts

Status date

Monday, March 18, 2013 - 17:33