By J.R. Wilson
CHINA LAKE NAVAL WEAPONS CENTER, Calif. - The venerable MIL-STD-1553 databus is about to make a quantum leap into the 21st century, having endured unchanged on an estimated one million applications during the most dramatic two decades of technological change in human history.
The proven stability and capability of the 1553 since its last Notice 2 revision in 1986 has made it a constant in everything from the B-2 bomber to handheld computers and munitions, yet rapid technology advances today demand far greater data-transfer speeds than the 1 megabit per second 1553 provides.
The existing 1553 standard is based on a trapezoidal waveform, with a recent addition for a filtered waveform, which also runs at 1 megabit per second, but is filtered to limit bandwidth to prevent electromagnetic interference.
The Boeing F-15E1 advanced-technology demonstrator aircraft, shown above, takes off from Lambert International Airport at St. Louis during a flight test last December of a high-performance 1553 data bus (called HyPer-1553) developed by Data Device Corp. (DDC). The faster speed of the new data bus helps increase bandwidth between subsystems, which is becoming increasingly necessary for network-centric operations and sensor fusion applications.
The upgraded standard also will incorporate a multicarrier waveform to provide 200-megabits-per-second data transfers.
“The multicarrier waveform uses excess capacity in the existing 1553 wiring to create a separate communications channel from the trapezoidal or filtered channel,” explains Duane Anderson, president of Edgewater Computer Systems in Ottawa. “So you have two separate network protocols, totally independent of each other, with their own bus controllers, on the same physical media.
Maximum throughput
“This is a 21st century technology, using advanced communications theory to get the maximum throughput possible,” Anderson says. “To get that high-performance throughput for the multicarrier waveform via a channel that is very distorted requires an enormous amount of signal processing and mathematical calculation.”
The U.S. Naval Air Systems Command (NAVAIR) at Patuxent River Naval Air Station, Md., and the U.S. Air Force Aeronautical Systems Division at Wright-Patterson Air Force Base, Ohio, have been working since the turn of the century on how to implement at least a hundredfold increase in the data rate, yet any such change also must meet stringent cost and time requirements.
“We need low risk, smooth insertion, and assurance that this technology is real,” says Gerard Walles, science and technology lead for NAVAIR’s F/A-18 Advanced Development Group. “We reviewed what the Air Force is doing and, to convince the program offices that this has those qualities, we undertook a demonstration on the ground at China Lake (Calif., Naval Air Warfare Weapons Center), using the F/A-18 Advanced Weapons Lab. We challenged the Edgewater company and the Air Force to prove to us that this technology has the qualities we are looking for.
“It was amazing to see this was done in such a short period of time,” Walles says. “They were successful in demonstrating all the things we asked them to do. We had senior management from Naval aviation and the program offices fly out to China Lake to witness these tests. They asked how it could be done with such ease and were, you could say, shocked that we were able to transition this technology without affecting the software or having any impact on the hardware.”
Edgewater has been under contract to the Air Force to demonstrate the Extended 1553 (E-1553) databus it began developing shortly after the Society of Automotive Engineers (SAE) and others declared it was impossible to do high-performance transfers over existing 1553 wiring.
“We developed the technology and presented it to the Air Force, which was quite surprised after having been told it was impossible,” Anderson says. “We demonstrated physically and theoretically about six years ago that it was totally possible. We’ve been building on that ever since, working to meet all the military requirements. Even in the last two or three years, when other companies became aware of what Edgewater was doing and the Air Force sought out other vendors who could meet their requirements, no other vendor was able to do it.”
Only one other vendor has tried to match Edgewater’s considerable investment-in time and money-on taking the 1553 to the next level. Data Device Corp. in Bohemia, N.Y., has been working with Boeing to demonstrate the potential for its own version of a high-performance bus, the HyPer-1553.
Flight demonstrations
In December 2005, DDC and Boeing Phantom Works in St. Louis conducted a flight demonstration of the HyPer-1553 on a Boeing F-15E-1 Strike Eagle Advanced Technology Demonstrator aircraft. Image data moved at 40 megabits per second between a rugged 6U VME chassis in the aircraft’s forward equipment bay and a modified Joint Direct Attack Munition (JDAM) mounted on a wing pylon.
Those transmissions moved over existing 1553 wiring in parallel with conventional traffic that normally utilizes the 1553. A second HyPer-1553, dedicated solely to the expanded data stream, was clocked at 80 and 120 megabits per second.
DDC pursued independent development of the HyPer-1553 while Edgewater was working with the Air Force but before what had been Edgewater proprietary intellectual property transferred to the U.S. government and was released-under ITAR restrictions-for use by other vendors.
“We met earlier this year with Boeing and DDC and have a commitment that they are not pursuing an alternate standard and are supportive of the MIL-STD and will pursue design solutions to meet that, although the HyPer-1553, as we understand it now, is not compliant and would not be accepted,” says Will Urschel, chief architected at Air Force Aeronautical Systems Division. “The United Kingdom government, U.S. Air Force, and NAVAIR have decided that, with this technology, we will not have multiple variants of the standard propagating through our fleets.
“The British MOD (Ministry of Defence) has undertaken parallel studies in terms of what next-generation network they should pursue and we’ve had a lot of discussions with them in the last year,” Urschel says. “Those studies are favorable of MIL-STD-1553B Notice 5; we will be working much more closely with them in the coming year to make sure they understand the full breadth of the technology and implementation of the standard being developed by the U.S. We also are presenting the standard to NATO through the Avionics Standardization Board and to the rest of the member nations.”
While the China Lake demonstration did not use an actual aircraft, Walles says the lab there is used to validate anything the Navy plans to put into its aircraft before moving to flight tests. For this test, high-speed data transmissions included video feeds of a Pixar animation, a traditional DVD movie, and EO/IR sensor video.
Real-world conditions
“Our engineers made sure the normal flight applications were running under normal conditions; none of the databus traffic was slowed down, none of the components were hand-picked-it was actual flight hardware,” Walles says. “We had map displays and flight controls up; we can simulate a flight mode, where navigation data, GPS data, flight control, and mission computer information are all operational. It is pretty much an airplane. We had it running in legacy computers and all the message traffic was active between all the boxes. Through a video switching mechanism, we could switch between different video sources.
“What we noticed was the low latency and real time performance of the bus,” Walles continues. “There was very little lag between the source and what was displayed. This bus is adaptable to any source, so we could stream Web information into the cockpit or three video sensors or data file exchanges. This is not a canned program with imagery. This was live feeds and very different from what was done before. It was a much more technical demonstration.”
Air Force researchers plan additional tests on the Edgewater E-1553, with an F-16 Block 30 jet fighter in an actual operating environment at Hill Air Force Base, Utah, in October, with systems integration lab and ground testing on a C-17 Globe Master III jet transport in the summer of 2007, and on a B-2 stealth bomber sometime next year, following completion of system-level investigations next Spring by prime contractor Northrop Grumman.
As this effort moves toward release of a new 1553-C, the Navy also is proceeding cautiously, noting there is more involved than just moving more data quickly over existing wiring.
“We are pushing new areas, including how to use this capability to provide information assurance in the area of multiple independent levels of security,” Walles explains. “This is a big emerging need. Most of our current architectures are built around a single-level security system. With integration being a key enabler, where we have to use computers to do multiple functions we need to do data fusion with multiple sensors, onboard and offboard, which brings up new challenges with levels of security.
“If we are going to host this on our current architecture, we have to protect that information, both on the ground and in the air,” Walles says. “We have to come up with new ways to have one processing system, which is a challenge. The current means of transmission through the wires prohibits us from doing this new functionality. The new bus architecture that Edgewater has will be an enabler to meeting that objective.”
Crucial considerations
The Air Force’s Urschel says while raw data throughput is important it actually is not the most important concern to the user community. A substantial part of the cost of weapons-system upgrades is verification, and a substantial part of verification is ensuring the information moving over aircraft networks is being received in the time frames required.
Because no existing network standard has any quality assurance of real-time operations, that assurance is gained through extensive, costly and time-consuming tests prior to deploying the upgrade. Part of the joint Navy/Air Force effort on the new E-1553 standards is incorporating the ability to substantially reduce upgrades testing
“If we had a network with an analytical basis through the design of the network itself and not just tests, we could save substantial dollars in future upgrades and capabilities on these aircraft,” Urschel explains. “That is one reason we have pursued this-not just raw data, but data received at the exact time required. In almost all other network standards, you have to derate them by at least a factor of 10 to get some assurance of real-time operations. Even then substantial system level verification has to occur to ensure we are getting information between the systems in the time frame required.
“As we got into the new network structure and signaling techniques, we saw there is a basic foundational layer to support real-time information,” Urschel continues. “We are using this for vehicle management, targeting, and target acquisitions, so we cannot afford to have information transmitted on these networks outside the required time frame; even valid information is useless if late within the context needed.”
Implementing the E-1553 to meet military requirements meant not only using the existing platform wiring, but doing so with as little change in hardware and software as possible. For the Navy and Air Force, it is not only a question of cost but also of how long an aircraft will be out of service while the change is made. The Air Force alone is looking at substantial capability upgrades it wants to make on more than 4000 existing aircraft that will still be in the fleet by 2020, about 85 percent of which have 1553-based networks.
Aircraft upgrades
“The physical transmission layer is identical to the current layer, which is very important because we already have the physical transmission line deployed and it is not affordable to replace that. Our estimates are $200,000 to $1 million per aircraft to do that. So a major issue is the ability to utilize the existing transmission lines resident in the aircraft, untouched, to carry not only existing traffic but high bandwidth as well,” Urschel explains, noting it also would take up to six months.
“The network interface device that puts a transmission signal on the bus, instead of using the previous 1553 signal, now can layer the new signal on top of it,” he says. “There is no physical change to the network at all. So only the network interface devices are changed and only those that transmit or receive the new data; those handling the existing signals were unchanged.”
As a result, upgrading an aircraft means pulling a line-replaceable unit (LRU) in the field and replacing it with another, then sending that LRU back to depot for a quick shop replaceable upgrade of the card containing the new network interface. That could be accomplished incrementally as part of each aircraft’s standard maintenance cycle in the field and could be completed across the Air Force fleet in as little as one year, says Bill Wilson, an Air Force Aeronautical Systems technical expert on buses and architectures.
The Navy says further analyses will need to be completed before they can estimate how extensive such an upgrade plan would be or how long it might take.
The importance of the 1553 to the military-and the potential of E-1553-is reflected in it being one of only seven joint Navy/USAF aviation initiatives being tracked at the three-star level.
Army buy-in
“We have included Army aviation recently and it has been endorsed at the three-star level there, as well, because of the perception of tremendous cost, schedule and performance advantages,” Urschel says.
While the 1553 is deployed on some 30,000 aircraft worldwide, it is even more widely used in non-aviation applications, including the International Space Station.
The new standard and dramatically increased speed of the E-1553 bus also make it possible to address an issue Urschel says has too long been overlooked.
“There is a tremendous push for network-enabled or -centric warfare. Almost 99 percent of that effort is being put into the offboard network, what is done off the weapons system,” he says. “But if we don’t invest in how the onboard network will handle that information within the security and time requirements, that won’t be of any use. So we are trying to ensure we have common attributes in the onboard networks.”
While the current drive is to provide a card-level upgrade for platform applications, Edgewater is looking at a much broader implementation of the new high-speed bus in the future.
“Later on we will have a chipset for embedding into products that can go into the same footprint as an existing 1553 interface,” Anderson says, “embedded deeply into multipurpose, multifunction cards. Those will be out in mid-2007; the first chips will be reserved for our own board-level products.”
