The Department of Defense (DoD), in an effort to take advantage of the rapid advancement of technology, is increasingly turning to open architecture systems and software-defined radios (Figure 1-1) as an alternative to closed system designs.  The Department of Navy formed the Naval Open Architecture Enterprise Team which created an open architecture assessment tool to analyze the adaptability of design projects.  By using open architectures, component  replacement can occur more easily than in a closed system.  Through software-defined radios, new communication protocols can be utilized without the need to replace hardware.  Open architecture is one key element in achieving more affordable electronics manufacturing aboard Navy ships.

Open systems, as defined by the Department of Defense Open Systems Joint Task Force, are those which conform to consensus based standards on all key interfaces.  For example, if designing a system that requires access to a storage device, the system could be designed so that it utilizes USB (Universal Serial Bus) for said access, allowing simple upgrades or replacement in the future.  USB is one example of an open standard, but there are many others such as PCI, RS232, and IEEE1394.  Open standards are those which involve the participation of many interested industry parties that collaborate on an acceptable standard.  An open standard must be freely available to all who wish to implement a system conforming to said standard.  Use of the standard may have a nominal licensing fee, but it should not be so excessive that it is a barrier to wide-spread use.  Utilizing these standards in system design will allow the system to be modified as new technology is developed with minimal impact on the existing system. For example, the effective processing power of a microprocessor doubles every eighteen months as a result of technology advances. A new processor could be placed in a system which utilized open standards with little or no impact to the display, or input/output modules.  This allows for the military to keep pace with the changing technology without the cost of a complete redesign.

An SDR (Software Defined Radio) is a radio whose functionality and waveforms are defined in software.  The software can reside in a DSP, an FPGA (Field Programmable Gate Array), or in any other appropriate processor.  There is an analog front end, which can handle the analog to digital and digital to analog conversions for transmission and reception of the desired radio communication protocol.  After the conversion, all core functionality occurs in the software.  Likewise, construction of the transmitted signal is performed in the software.  Given the sampling rates for digital-to-analog (D/A) and analog-to-digital (A/D) converters, the signal may be mixed up or down to the desired carrier frequency depending on the application.  As the sampling rates of D/As and A/Ds increase the analog portion of the radio design decreases.  Since the radio functionality, modulation/demodulation, base band processing, and filtering are defined in software, the platform becomes very versatile.  By using such a system, the radio can be reconfigured in the field for different protocols depending on the application. 

Taking this a step further, several different communications protocols can be actively switched while in use.  The number of protocols that are supported by a device is almost limitless.   The Joint Tactical Radio System (JTRS) is a DoD initiative that uses these protocols to implement different waveforms for different applications and missons, allowing the warfighter with a single radio to communicate with the most appropriate protocol for the given situation.

Open architectures are being used in redesign to allow for modular components to be utilized for control and user input.  A compact Peripheral Components Interconnect (cPCI) backplane is used to allow for the modular implementation of the receiver and transmitter RF sections as well as MIL-STD-1553 control, control processor and SDR.  Through use of the cPCI backplane, additional bus devices can be added for increased functionality with minimal impact on the other components.  For example, if it is determined that the unit is required to generate output to a monitor, a graphics controller could be added to the bus.  The impact of this upgrade would be isolated to the controller software to generate output for this device.  Utilizing open standards such as the cPCI backplane increases the versatility and the useful lifetime of the unit.

The AN/ARS-6 redesign, currently underway at U.S. Army CECOM, leverages SDR technology for implementing the transmitted waveform, utilizing a circuit card with some analog-to-digital converters, digital-to-analog converters, an FPGA, and a PCI interface.  The FPGA is utilized for the digital signal processing.  Implemented within the FPGA are the DME waveform modulation, time dependent control signaling, and DME demodulation.  These provide the functionality for the combat search and rescue application of this unit. The unit could be expanded to communicate with other systems by implementing a different FPGA design to achieve that function.  The unit could then be switched from one functional mode to another with a simple reconfiguration of the FPGA, which can occur while the unit is operational. This versatility could potentially reduce the amount of differing communication equipment needed.

Through the use of open architectures and SDR technologies the DoD can better keep pace with changing technology.  Reconfigurable devices, such as SDRs, can help reduce the warfighter’s need to carry multiple radio systems.  The JTRS (Joint Tactical Radio System) program was set up for that purpose.  By leveraging SDR technology, the DoD hopes to enable the modern warfighter to communicate using any method or protocol available without the need for multiple radios.  The Department of Navy hopes to increase affordability  of shipboard electronics through the use of open architectures.  The Navy is accomplishing this through many projects such as the Littoral Combat Ship, on which the EMPF is collaborating.

By utilizing open architecture approaches to shipboard systems, the useful lifetime of those systems can be extended, and more importantly, can drive down the total ownership cost of electronics hardware aboard current and future ships.  New advances in the electronics industry can be leveraged by changing only the necessary component - with little impact to other system components.  Allowing for current technology to be introduced into a system will contain ever-increasing upgrade costs, which ultimately will lead to greater improvements in affordability of shipboard systems.