A Q&A About AS6003 TTP Communication Protocol

The SAE International AS-2 Embedded Computing Systems Committee is working to develop the AS6003 TTP Communication Protocol, an aerospace standard that will simplify the design of advanced integrated systems using time-triggered protocol (TTP), resulting in lifecycle cost savings. Dr. Mirko Jakovljevic, of TTTech Computertechnik AG in Vienna, Austria, is the chair of the SAE AS-2D subcommittee focusing on time-triggered system and architectures. He answered some questions about the protocol.

Q: What are some of the benefits that might come out of this protocol?

Jakovljevic:

TTP is a new generation of databuses designed for use in critical embedded systems for cross-industry applications.
TTP offers linear scalability, robust partitioning, determinism, low jitter, and higher bandwidth.
It also reduces complexity and system integration effort, which is a significant part of the system lifecycle costs.

TTP is used in railway, commercial (Boeing B787 and Airbus A380) and defense aviation programs, land systems and commercial vehicles. TTP is an open technology and SAE AS6003 will support creation of a larger ecosystem of component, tool and services providers.

Q: How does TTP compare to existing ARINC 429 and MIL 1553 standards?

From data bandwidth perspective, TTP offers 10x higher bandwidth than Mil-1553 and 100x higher bandwidth than ARINC-429. In comparison to MIL-1553, TTP does not use bus controllers, which is beneficial for fault-tolerant operation and acceptable for commercial aerospace applications.

TTP also contains higher-level services for system health monitoring, redundancy management, and system synchronization which makes TTP a hard real-time platform for distributed, fault-tolerant computing, certifiable for highest criticality applications.

Q: How does TTP support system design, system integration, teamwork and acquisition?

In terms of system design and integration, TTP helps to reduce the complexity of interactions among functions in a system. The resulting impact on the design team’s capability to understand, modify, and verify a system design can be very significant. Companies with many dislocated teams working on one complex integrated system that uses modular subcontracting strategies, like MOSA, can significantly profit from TTP-based architectures.

TTP helps to reduce the system integration effort, and advanced users who optimize their internal design process could easily see an order of magnitude improvement in integrations effort. TTP also supports upgrades, incremental modernization and obsolescence management.

A special case is the reuse—one of key TTP strengths. Reuse allows the split of initial system design costs over several platforms.

Q: Can you give an example?

Jakovljevic: If an integrators is working on a “clean sheet” architecture using TTP, let’s say for a Boeing 787 or a new type of military aircraft, they would have a system that is well designed, less complex, scalable and predictable in operation. TTP-based system architectures are parametric, so you can reuse the same system, on the new generation of aircraft or another type of aircraft, just by changing the parameters and configuration.

For example TTP is a part of Hamilton Sundstrand’s Common Electronic Architecture, to enable reuse of integrated electronic systems over several platforms. Honeywell claims in one of recent publications that with time-triggered technology, both development effort and cost for reuse of modular avionics controls (MAC) on a different platform can be reduced for 50%.

For example, if you have an unmanned air vehicle (UAV) with TTP-based architecture and you want to change some operational characteristic or add different payloads for different mission, TTP allows that and prevents unintended system behavior. This is a real advantage because you can have one electronic brain which is reused for different types of UAVs; and you can expand it or shrink it in any way you want to.

Q: Are there other ways in which TTP allows for cost savings?

Jakovljevic:
Yes, SAE AS6003 enables the same set of benefits as Integrated Modular Avionics (IMA), but in a completely distributed system. Time-triggered technologies support modular certification and reuse of certification data on different platforms.

It is possible to modify and change system functions without impact on other functions in the distributed system. We call it “true modularity” because in this case we resolve many, many issues that have been on the agenda of advanced systems integrators for a very long time.

Q: Which future standardization activities for time-triggered technologies are planned?
Jakovljevic:
We will work on TTP physical layer later in 2009. Also we plan to standardize a time-triggered service for Ethernet which is currently available as TTEthernet. It offers same benefits as TTP, but it is fully compatible with IEEE802.3 Ethernet and runs at Gigabit speeds. This technology is selected for NASA Constellation program and will be deployed for avionics integration.