While faster processing, smaller packaging and software innovations have helped push the introduction of Mil-Std-1553 products with more capabilities, cost-effective methods of achieving breakthrough data rate increases while using the same data bus architecture are advancing.
The U.S. Air Force, in cooperation with Edgewater Computer Systems of Canada, is in the process of testing 1553 technology that will achieve much higher rates while using an aircraft's existing wiring and infrastructure. Bohemia, N.Y.-based Data Device Corp. (DDC), along with its industry partners, also has demonstrated high-speed 1553. The technique is viewed as one of a number of alternatives for adding extra bandwidth capacity to legacy aircraft. Not having to rewire the airframe saves cost and time out of service, compared with competing technologies, such as Ethernet and Fibre Channel.
There are three types of Mil-Std-1553 data buses. The conventional, 1-Mbit/s 1553 is currently onboard the entire U.S. Air Force, Army and Navy aircraft fleets, as well as in military aircraft worldwide. When 1553 buses were first developed in the early 1970s, 1 Mbit/s was considered state-of-the-art and adequate to meet the needs of the military into the future. But in the late 1990s, certain applications, such as radar and forward looking infrared (FLIR) sensors, data communications and certain munitions, began to require more bandwidth capacity. In response to an Air Force request, the Society of Automotive Engineers (SAE), the Mil-Std-1553 specification maintainer, developed Enhanced Bit Rate 1553, a 10-Mbit/sec version of the data bus.
But, according to Todd Decker, DDC's marketing manager for 1553, the 10-Mbit version "does not use the same wiring or infrastructure; it really just uses the protocol from Mil-Std-1553."
In the past decade, the demand for new communications and data applications in existing military aircraft has exceeded the capabilities of the legacy 1553 bus. In order to take advantage of advancements in avionics, higher-speed processors, input/output (I/O) channels and other technological developments in electronics that require higher throughput, Air Force and industry researchers in the late 1990s began working on a third variation of the 1553 bus, which involves overlaying a high-speed signal on top of the existing low-speed signal to create a new data and communications channel that can operate at much faster speeds, in parallel with the legacy 1553 bus.
Will Urschel, chief architect at the Air Force Aeronautical Systems Center (ASC), notes that with programs like the Joint Tactical Radio System (JTRS) and tactical targeting network technology (TTNT), 99 percent of the efforts have focused on developing offboard networks, while little work has been done to determine how those programs will interface with the aircraft networks. One solution, installing an Ethernet port on board the aircraft, would require costly rewiring and time out of service for most of the Air Force fleet. "If we had tens of billions of dollars and 20 years, we could do that," Urschel explains, but "the funding isn't available and the time isn't available."
Developed by Edgewater in cooperation with the Air Force, Extended 1553 (E1553) is designed to use existing 1553 infrastructure, including the bus and stub cables, couplers, and termination resistors, to provide increased throughput. E1553 coexists with legacy 1553 remote terminals and bus controllers, and can operate independently of existing software as a separate network on the same bus. This leads to substantial reductions in software verification costs, since the aircraft's existing operational flight program (OFP) does not need to be changed to support new capabilities. Duane Anderson, president of Edgewater, says that the technology is directly applicable to any platform with a 1553 bus, such as F-15 and F/A-18 fighters, B-2 and B-52 bombers, and C-5, C-17 and C-130 transports. It also could be used for helicopters, such as the AH-64 Apache. In fact, Anderson says, all legacy aircraft with 1553 buses that require additional high-speed performance could use E1553 technology.
Edgewater recently partnered with Rockwell Collins to prove the compatibility of the E1553 bus with a Collins' multifunction display, as well as a TTNT radio. The tests, in a C-130 system integration lab, specifically demonstrated high-performance communications using existing wiring and components and the E1553 bus.
The Canadian company is also under contract with the Air Force's Odgen Air Logistics Center at Hill AFB, Utah, to provide Extended 1553 network interface cards, driver software and technical support for avionics boxes that will be installed in F-16, Block 30, aircraft. Hill AFB is currently conducting flight tests of the technology, a process expected to conclude in April 2007. These flight tests are intended to prove that the data bus can transfer data between multiple E1553-enabled line replaceable units (LRUs) in a multidrop configuration. The tests will include the transmission of multiple video and data streams to the cockpit, and elsewhere on the platform, while concurrently supporting operational flight command and data traffic across the legacy 1553 over the same bus. In addition, the company has been working with the Air Force and Navy and to demonstrate its E1553 technology in system integration labs at Hill AFB, Wright-Patterson AFB, Ohio, China Lake Naval Air Station, Calif., as well as at Edgewater facilities. The company also is performing tests to confirm the validity of Mil-Std-1553B, Notice 5, an amendment issued to the 1553 standard in April 2006.
According to Bill Wilson, an avionics architecture specialist with ASC, the Air Force is testing the 1553 technology on a fighter (F-16, Block 30), a bomber (B-2) and a transport aircraft (C-17) in order to "get a wide range of experience so we can resolve any particular issues that may occur in terms of one particular application over another."
Edgewater is not the only company testing high-speed 1553 technology. Bohemia, N.Y.-based DDC has been developing its brand of high-performance data bus, known as HyPer 1553, since March 2002.
In December 2005, DDC, along with Boeing and Honeywell, demonstrated its HyPer 1553 technology on a Boeing F-15E1 advanced technology demonstrator. The companies achieved 40 Mbits/s while simultaneously operating the legacy 1-Mbit/s bus, and up to 120 Mbits/s on a second bus dedicated to high-speed transfer.
Since the F-15 demonstration, DDC has worked with the Navy in lab tests related to the F/A-18, as well as some recent trials at China Lake NAS. Decker says those tests demonstrated up to 100 Mbits/s using HyPer while simultaneously running a 1-Mbit legacy bus, without using any special filters while retaining low-latency characteristics. He adds that DDC is confident it can achieve rates of 150 and 200 Mbits/s while running a legacy 1553 bus.
The Air Force's launch application for the high-performance 1553 is the JTRS program. Anderson notes that JTRS platforms will benefit from the higher bandwidth provided by the technology. Although requiring such network interfaces on military aircraft will ultimately be decided by the U.S. Department of Defense, Edgewater thinks it would be "a logical requirement, because JTRS radios already have a 1553 data bus connector and most [military] aircraft already have 1553 data buses," Anderson says.
Besides communications applications, high-performance 1553 could be used for applications such as munitions delivery, as well as the transfer of video, radar and other imaging data. With munitions, high-speed 1553 interfaces would enable the military to perform weapons downloads much faster. Anderson notes that high-speed 1553 will have applications in network centric operations. "Current military radio data network systems are inadequate to handle the much larger data flows necessary for network centric operations and warfare," he says, adding that E1553 is "the ideal means of enabling weapons platforms for network centric operations."
One disadvantage of using the increased-performance 1553 bus is that the speed has an upper limit. For instance, operators won't be able to get the 1-, 4- or 10-Gbit/s speeds offered through modern Ethernet or Fibre Channel interfaces currently being installed on new aircraft. But the monetary savings that can be achieved vs. installing next-generation technology are significant.
According to Anderson, increasing the performance of an existing 1553 bus through Extended 1553 is a "cost-effective means of upgrading the performance and functionality of an aircraft's internal data networks ... with no change to aircraft wiring." This method avoids anywhere from $500,000 to $2 million in rewiring costs, and up to one year of down time for installation on each fighter, he adds.
"LRUs can be upgraded incrementally only if and when necessary," Anderson continues, adding that there is little to no impact to the aircraft's operational flight program, which reduces software verification costs created by changing an OFP.
"The old 1553 that's already on existing aircraft doesn't have to change," Decker says, "and that's really compelling, because you've got a lot of systems that have gone through years of integration, and testing, and certification of software, and everything else." The advantage of HyPer 1553, he continues, "is that you unplug a box that used to plug into 1553, and you plug in a new box that has both old and new 1553, and it's kind of a quick-change operation." Using high-performance 1553 enables new capabilities "without having to peel the skin off an aircraft, pull a new copper wire or new fiber optic cable, and hook these devices up," Decker adds.
Based on technologies provided by Edgewater, the Air Force issued an update to the existing standard in April 2006, covering the initial expanded 1553 requirements. Known as Mil-Std-1553B, Notice 5, the specification increases the throughput capacity of the 1553 bus to an uncompressed data rate of 200 Mbits/s over existing aircraft wiring, while maintaining a 10 -12 bit error ratio. Notice 5 is protected under ITAR rules. The Air Force plans to release a Notice 6 amendment to Mil-Std-1553B soon, incorporating comments received from the industry and other service branches, followed later by Mil-Std-1553C, a tri-service standard. Urschel explains that both documents will essentially be revised versions of Notice 5. Further updates to the standard will address future avionics capability upgrades, such as multiple independent levels of security (MILS), expanded address space, wiring diagnostics and guaranteed timeliness of real-time functions.
While DDC has not yet introduced a Notice 5-compliant product, Decker says that all the research conducted for HyPer 1553 will directly translate into Notice 5 offerings once the market matures and the standard becomes more widely accepted.
"The techniques that DDC uses and those used in Notice 5 are essentially the same thing ... we just have to fill in the details of the protocol," he says.
How Fast Can it Get?
According to Anderson, Edgewater is considering methods to approach or achieve a data rate of 500 Mbits/s with Extended 1553. But ultimately, he says, the highest achievable data rate in any networking technology "is limited by the integrity of the network and the environmental operating conditions."
Decker thinks that a data transfer rate of 1 Gbit/s "is not achievable in the signal to noise ratio environment that 1553 operates in." He says the "sweet spot" with the technology is likely in the 100 to 200 Mbits/s range, adding that 50 to 100 Mbits/s could be achieved on almost any existing 1553 bus.
New 1553 Products
Several companies have released new Mil-Std-1553 data bus products this year. In September, DDC unveiled its BU-65590F/M, a PMC card for 1553 and ARINC 429 applications, and its BU-65590U, a USB avionics device also for 1553 and 429. The multiprotocol PMC card supports many functions, including up to four dual-redundant 1553 channels, ARINC 429 receive and transmit channels, six discrete input/outputs (I/Os) and an IRIG-B time synchronization input. The portable USB device also supports multiple channels of 1553, 429, discrete I/O and IRIG-B. In July, DDC introduced its BU-65578C, a PC/104-Plus card for 1553.
GE Fanuc Embedded Systems, which acquired longtime 1553 component manufacturer Condor Engineering in April 2006, released its P-10SF in June. A single-function PMC module for 10-Mbit/s, Mil-Std-1553B performance, the P-10SF features one or two dual-redundant 10-Mbit channels using RS-485 transceivers. GE Fanuc says the module is designed for flight controls, actuators, electro-pneumatic controllers or other traditional 1553 applications requiring faster data rates.
Elmont, N.Y.-based Excalibur Systems introduced this summer its EXC-4000 PC104 and PC104-Plus cards that provide 1553, ARINC 429, serial and discrete I/O channels. The EXC-4000 is designed for Excalibur's Dragon PC104 system. The company also has recently introduced a 16-channel, conduction-cooled VME card.
This April, AIM GmbH launched MILScope, a 1553 test and analysis tool that allows users of its APX1553 interface cards to not only monitor data and detect protocol errors, but verify waveforms and detect faulty conditions without using an external oscilloscope. Mil-Std-1553 bus timings, such as rise and fall times, overshoot and undershoot, pulse width and signal amplitude, can be measured and stored using MILScope.
Ballard Technology of Everett, Wash., offers its OmniBus PMC module, which features one or two dual-redundant 1553 channels. The commercial-off-the-shelf (COTS) product is designed for rugged conditions. It has a universal PCI interface, a rear panel input/output (I/O) and an optional front panel I/O that provide access to the 1553 bus signals. The module also has RT address inputs, RS-232, 422 and 485 serial ports and an avionics discrete I/O.
In March, Holt Integrated Circuits completed remote terminal (RT) validation tests of its HI-6110 message processor. The single-chip, CMOS 3.3-volt message processor is designed to implement Mil-Std-1553 protocol between a host processor and a dual-redundant 1553 bus. The HI-6110, a commercial off-the-shelf product, can be configured as a bus controller, a remote terminal or an addressed or non-addressed monitor terminal.
Also in March, Bohemia, N.Y.-based North Atlantic Industries unveiled its 64D1 multifunction, single-slot VME communications card. The VME card accommodates three independent function modules. Each module can include two channels of dual-redundant Mil-Std-1553, eight channels of Profibus, 48 channels of discrete I/O or 48 channels of TTL I/O. The 64D1 is available in operating temperatures of -40 to 85 degrees C and 0 to 70 degrees C.
Rockwell Collins Integration Tests
On Aug. 30, 2006, Rockwell Collins and Edgewater Computer Systems announced they had demonstrated Edgewater's high-performance Extended 1553 data bus with an adapted MFD-268 multifunction display and tactical targeting network technology (TTNT) radio terminal. TTNT is an emerging airborne networking waveform. The tests were conducted aboard a C-130 system integration lab. The companies successfully ran the Extended 1553 bus at more than 50 Mbits/s (the stated throughput rate established for the trials) while concurrently operating the legacy 1553 bus at approximately 700 Kbits/s, without any signal degradation.
As part of the tests, engineers passed DVD-quality video, large data files and Link 16 situational awareness information from the TTNT radio, through the Extended 1553 bus and to the MFD. (A second TTNT radio was used as an off-platform network environment.)
"Extended 1553-equipped TTNT radios and cockpit displays will provide an end-to-end pipe capable of supporting network centric warfare operations not possible today," says John Dunn, senior director of integrated systems, advanced programs. He adds that applications include video and voice over Internet protocol, remote flight plan updates, remote weather and improved situational awareness feeds. The two companies plan to continue working together on further validation of the high-performance 1553 technology to complement the implementation of Mil-Std-1553B, Notice 5, buses in F-16, F-18 and C-17 aircraft, as well as other platforms.
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Aero Express www.aeroexpress.com
AIM GmbH and AIM-USA www.aim-online.com
Ampol Technologies www.ampol-tech.com
Ballard Technology www.ballardtech.com
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Data Device Corp. www.ddc-web.com
Demo Systems www.demosystems.com
Edgewater Computer Systems www.edgewater.ca
Excalibur Systems www.mil-1553.com
GE Fanuc Embedded Systems www.gefanuc.com/embedded
Holt Integrated Circuits www.holtic.com
MAX Technologies www.maxt.com
National Hybrid Inc. www.nationalhybrid.com
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Phoenix Logistics www.phxlogistics.com
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