Mobile Dynamics runs 100 megabits per second on 1553
By John McHale
SANTA CLARA, Calif. — Engineers at Mobile Dynamics Inc. of Santa Clara, Calif., recently transmitted data faster than 100 megabits per second across the MIL-STD-1553 serial data bus, and say they expect to deliver 300 megabits per second over 1553 sometime in 2001.
This kind of bandwidth on 1553 — which normally moves data only as fast as 1 megabit per second — should enable robust, deterministic transmission of voice and video across 1553.
If workable, this development could compel military and aerospace systems designers to rethink their choices of other fast serial databuses such as Asynchronous Transfer Mode, Fiber Data Distributed Interface, or even Fibre Channel.
The Mobile Dynamics solution, MDI-1553+, will run the transmission over the existing MIL-STD C-17 copper cable, and supports the Manchester II bi-phase coding for 1 megabit per second transmission. It also provides interoperability with existing low-speed AS1553 terminals at a rate of 1 megabit per second using the existing AS1553 transformer assemblies.
"This is a major milestone for [Mobile Dynamics] and the U.S. military," says Jack Musetti, chief executive officer of Mobile Dynamics and vice chairman of the Society of Automotive Engineers (SAE) next-generation MIL-STD 1553 Standards Committee. "Prior to the introduction of [Mobile Dynamics`] technology, the U.S. military had no way to modernize their on-board electronic network systems without expensive unreliable fiber solutions and infrastructure retrofitting on every air, ground, and ship platform.
"With our technology, they have the speed they need to modernize their systems without re-wiring which can lead to hundreds of millions of dollars in savings," Musetti continues. "With ever tightening budgets for military applications, the technology will enable future applications at a fraction of the cost while reducing cost of ownership and increasing product life cycle."
Next-generation 1553 "will be a major logistical advantage to the military," Musetti says. "They won`t have to pull planes apart to replace all the existing cable" with Fibre Channel, he adds. "What the military wants is an extended life cycle, and to reduce the cost of ownership."
It will cost the U.S. military about $10 million per aircraft to retrofit each U.S. Air Force F-16, he claims. Putting Fibre Channel into the Apache helicopter is costing half as much as the aircraft itself, Musetti continues.
The maintenance of Fiber Channel systems is also very costly, he says. Plus Fiber Channel will not accommodate the 1-megabit-per-second 1553 that is necessary to operate landing gear, but the MDI-1553+ will, Musetti claims.
The constraints for bending Fiber channel are tight, Musetti explains. "Any way you look at it, it`s glass," he adds. Severe vibrations on a military platform will sever it, Musetti explains.
While 100 megabits per second represents a 100-fold increase over current 1553, Mobile Dynamics officials claim the final integrated circuit will operate at 300 megabits per second.
The new product will support 250 terminals as opposed to the 32 terminal addressing on current 1553. Multi-port versions will enable speeds beyond 1 gigabit per second via trunking. This will provide the use of copper over fiber optic cable plants and remove the concern of fiber on military platforms, they say.
During the last two years, officials on the SAE Avionics Systems Subcommittee (AS-1A) have been investigating the use of different technologies to increase the data transfer capacity of existing AS1553 networks.
U.S. Department of Defense officials requested the study to find ways of existing weapon system platforms with subsystems that would demand more data transfer bandwidth, says Francois Trans, chief technical officer at Mobile Dynamics.
Company engineers demonstrated their 100-megabit-per-second solution earlier this year to U.S. Air Force officials at Wright-Patterson Air Force Base in Dayton, Ohio, and at the Society of Automotive Engineers Conference in San Diego.
The Mobile Dynamics next-generation 1553 uses multi-level modulations and advanced coding schemes, Trots says. Multi-level modulation such as Quadrature Amplitude Modulation (QAM) or baseband Pulse Amplitude Modulation (PAM) will increase the bandwidth efficiency to support transmission of 100 megabits per second over a band-limited channel of as much as 30MHz, Trans adds.
Mobile Dynamics engineers have also reduced the signal level of the transmission by combining their modulation, coding, and advanced equalization for noise suppression techniques to achieve a high performance and high capacity suitable to support 300 megabits per second over the existing MIL-C-17-Cable.
Extreme precision timing throughout the solution enables MDI-1553+ to be deterministic, Musetti says. The MDI-1553+ signaling scheme for 100 megabits per second speed will not require a new coupler, Trans says. "However, MDI-1553+ signaling scheme for 300 + megabits per second will require a new coupler for higher data throughput and additional stub wiring would also need to be added to power the couplers," he explains.
The new design addresses challenges such as additional power requirements, cooling concerns, as well as system reliability, he adds.
"We are also looking to apply the technology in processor to processor applications, which lead to a virtual open architect and allow distributed processing thus increasing expansion to support additional sub-systems with minimal space impacts," Musetti says.
Mobile Dynamics engineers are also working on interfacing their product with MIL-STD 1773, a 20-megabit product from Boeing that never took off, Musetti says. It had some addressing problems they were not able to solve and they did not account for fiber optics, he explains.
Earlier in the program, Mobile Dynamics officials evaluated commercially available technologies such as xDSL for next generation 1553 application. They found the technology was not suitable for the Multi-drop Bus architecture, they say.
Stringent requirements such as a robust and reliable message deliver mechanism for mission critical applications cannot be met from the best effort xDSL signaling and delivery system, Mobile Dynamics officials claim. Guaranteed time-critical messages needed to transfer reliably and cannot be met by ATM protocol since the message can be dropped via the inherent ATM Fast Packet protocol and switch design, they say.
The main difference is that "we are multipoint while xDSL is point to point," Musetti says. The flexible bandwidth allocation and time division multiplex schemes are crucial for 1553 terminals to guarantee a robust communication method; commercial xDSL does not support it, Mobile Dynamics officials say.
Aeroflex UTMC in Colorado Springs, Colo., provided the chip work for the MDI-1553+, and engineers at Excalibur in Elmont, N.Y., provided the test equipment for the solution, Musetti says.
A new 1553 solution from Mobile Dynamics runs 100 megabits per second over existing cable.
