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Advantage... SDR
by Claus Vesterholt, Technical Program Mgr.—SATCOM, GateHouse A/S

This is an introduction to the challenges, opportunities and advantages associated with Software Defined Radio (SDR), particularly within the field of satellite communication (SATCOM), and more specifically in relation to Inmarsat’s currently most advanced IP-service, the Broadband Global Area Network (BGAN).

SDRFig1 SDR (Software Defined Radio) is no longer a vision but an opportunity readily at hand for manufacturers of military terminals and radios, software developers and satellite communication (SATCOM) service providers. The technology argues that:

• Rapid technological developments within the underlying hardware components have paved the way for SDR.

• In addition to the multiple generic advantages of SDR, SATCOM may be the only communication option available in many operational scenarios—and at present Inmarsat BGAN is an attractive option for achieving global commercial SDR-based satellite communication.

• Access to commercial SATCOM such as Inmarsat BGAN is expected to be a vital supplement to military programs also in the future, offering on-demand access and additional capacity.

• GateHouse has a long track record as a leading provider of the complete software package for Inmarsat BGAN terminals—the most recent offering is the BGAN Waveform developed for SDR and SCA-compliant military radio hardware.

An Introduction
SDR as a term has been around for a long time. The technology has been the vision of a single wireless multi-purpose device that could seamlessly integrate multiple communication channels, including SATCOM... a vision no longer.

Teledyne_ad_MSM1112 Driven mainly by the military market and DoD/MoD’s need for interoperability, flexibility in choice of communication means, reduced total cost of ownership as well as rapid functionality upgrades and repair, the SDR technology has experienced great advances and focus during the last decade.

With the increasing globalization on the military scene, (i.e., participation of various countries in international conflict resolution and peace keeping missions) the need for communication and interoperability in remote areas of the globe has significantly increased.

SATCOM is an attractive option when the communication distance increases and direct radio links become unavailable in the scene of operation. SATCOM is used heavily by military entities and governments and operational needs can no longer be fulfilled by the military SATCOM (milSATCOM) solutions only. In fact, 80 percent of all U.S. government and military traffic in 2008 was already carried via commercial satellites1—commercial SATCOM is an established supplement enabling easy, flexible and on-demand access to extra capacity.

Inmarsat BGAN is the leading global commercial broadband mobile SATCOM service available and the company is a well-established SATCOM provider. BGAN is easy to set-up and use and has already been proven in military field operations. Moreover, BGAN is currently an attractive option for achieving commercial SDR-based SATCOM. This combination of BGAN SATCOM and SDR is enabled by GateHouse and is the company’s most recent technological development.

Currently, militaries operate with dedicated hardware/software for each communication means, e.g., one radio/terminal for SATCOM and one for VHF, UHF and so on. This is space demanding and sets a limit to the number of communication means that the soldiers in the field can use.

With an SDR platform, the number of communications means is limited only by the channels available on the terminal as well as the requirements of the individual mission. This operational benefit is complemented by the cost benefits mentioned above.

SDR does provide benefits for the end-users as well as for manufacturers of military radios/terminals. SDR provides each manufacturer with the opportunity to customize their offering to satisfy changing customer demands, with limited extra costs incurred and a reduced time to market.

SDRFig2 With SDR, the manufacturers can produce the SDR terminal hardware and then wait to equip it with software waveforms when the customer requirements have been defined. This saves the manufacturer significant development and waveform porting costs. In other words, the manufacturers are enabled to deliver greater customer value at lower cost.

GateHouse acknowledges the needs for, and benefits of, SDR and is focused on initially delivering the Inmarsat BGAN SATCOM SDR waveform to the military market.

BGAN @ A Glance
Inmarsat is a recognized pioneer and market leader in the field of global Mobile Satellite Services (MSS), and the IP-based BGAN (the acronym for Broadband Global Area Network) service is the most advanced of Inmarsat’s current offerings.

The service is provided globally via three satellites placed in geostationary Earth orbit. System specifications provide for terminals operating from ground vehicles, ships and airplanes.

While the Inmarsat BGAN system is a commercial system, it has been adopted by military forces for Beyond-Line-Of-Sight (BLOS) communication, primarily because it is easy to set up and use, and provides an on-demand 492kbps data service on the surface of the Earth, with exception of the Polar Regions.

The government sector is a major revenue generator for Inmarsat. The airtime is generated from an installed terminal base provided by manufacturers of commercial equipment for government aircrafts, ground vehicles and ships. The shift to SDR based terminals is expected to enable BGAN on tactical radios, as it provides an opportunity for an instant BLOS capability, at limited extra cost.

SDRFig3 SDR Technology
Over the last 30 years, radios have changed from purely hardware-based to containing more and more software. The term Software Defined Radio is used for a radio where the essential functions are implemented in software and which, as a consequence, can be reconfigured for different communication standards.

An SDR contains generic processing elements, namely, General Purpose Processors (GPP), Digital Processing Processors (DSP) and Field Programmable Gate Arrays (FPGA). These processing elements are loaded and configured during startup of the modem to make the unit perform as required to implement a particular communication standard. The term Waveform refers to the software loaded during startup of the modem which performs the communication functions.

The development of SDR technology has been encouraged by the rapid development over recent years in integrated circuits (ICs), where size and power consumption has decreased and performance and flexibility has increased, enabling very high performance generic platforms.

The U.S. DoD has invested in SDR through the Joint Tactical Radio System (JTRS) program. The JTRS program has produced a number of SDR radios and waveforms. It has also produced the SCA standard (short for Software Communication Architecture) which specifies how radio platform and waveforms must be designed and implemented to ensure interoperability, and in particular that an SCA compliant waveform can run on different radio platforms as long as they are SCA compliant.

The GateHouse BGAN waveform contains all the common functionality required to build a BGAN terminal with on-demand, beyond-line-of-sight (BLOS) communication capability.

The BGAN Waveform is developed for Software Defined Radios (SDRs) and can be made compliant with the SCA specification version 2.2.2. This means that the waveform can run on generic SDR hardware conformant to the SCA specification (the waveform can also run on non-SCA compliant hardware).

SDRFig4 The BGAN waveform can run as the only waveform on the radio or as one of several waveforms on a multimode radio. Due to the SCA specification, the effort to port the waveform from one radio to another is considerably less than for a conventional radio design where the software typically interfaces custom designed hardware.

The traditional approach has been to develop inflexible purpose—specific hardware to implement a BGAN terminal, whereas by using the SDR approach, the complete functionality (waveform) is implemented in software, leaving the underlying hardware generic and fit for other purposes as well.

In addition to giving the advantage of reusing radio platforms and allowing for the coexistence of waveforms on a single radio, the SDR approach also allows for easy upgrades of the BGAN terminals as the BGAN standard evolves (e.g., support of higher data rates).

The GateHouse BGAN waveform is structured internally according to the Inmarsat BGAN specifications and contains multiple layers of functionality as shown in Figure 3.

In a typical customer engagement process, the customer provides an SDR platform which is either already existing or a new development. In the case of new terminal development, GateHouse is involved early in the terminal design and implementation process to define software/hardware interfaces in cooperation with the customer and to ensure that the radio platform is capable of hosting the BGAN waveform. When Gatehouse receives the radio platform, the BGAN waveform is then configured and built for the radio and loaded into the radio. A series of thorough tests is then conducted to ensure that the resulting BGAN SDR terminal is compliant with the BGAN specifications.

VesterholtHead About the author
Claus Vesterholt is the Technical Program Manager for the Satellite Communication activities in the Danish software company GateHouse A/S. He has a Master degree in Electrical Engineering from Aalborg University and has taken various positions in the wireless communication industry over the last 18 years. He has been leading a number of programs and projects on the development of communication systems, mainly GSM/GPRS terminals and Inmarsat BGAN terminals. Claus has experience in developing and testing communication software for terrestrial systems and satellite systems. Currently, Claus is responsible for all technical activities in the SATCOM area of Gatehouse and leads the engineering team.

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About GateHouse + SDR
Proven Core Technology—Single point of contact and access to a rock-solid, field-proven IPR platform based on more than 100 man-years of accumulated expertise from more than 10 completed BGAN terminal development programs across many different hardware platforms—for aeronautical, maritime and land mobile usage.

Reduced development costs and time-to-market—An attractive alternative to in-house development, which will bring BGAN terminal projects through to Inmarsat Final Type Approval faster, with considerably fewer risks and at a competitive and flexible pricing model.

Fully capable BGAN partner—GateHouse is able to take charge of the entire BGAN implementation process based on a customer supplied hardware platform up to, and including, the mandatory approval testing (Inmarsat Final Type Approval).

BGAN Software Defined Radio—the Company provides the complete embedded software package for Inmarsat BGAN terminals, a competence center for SDR, and provider of a BGAN waveform that can be made compliant to the SCA specification.

Additional information is available at the GateHouse A/S website: http://www.gatehouse.dk/

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Northrop Grumman has become the first BGAN SDR Hardware Partner

Since the contract between GateHouse and Inmarsat on development of the BGAN waveform was entered into in 2009, the commercial goal has been to identify and contract with the first hardware partner to bring BGAN SDR to the market. The development project is now nearing completion and the first hardware partner has agreed to introduce BGAN SDR.

Northrop Grumman will be the first partner to introduce BGAN SDR to the market. In 2011, Inmarsat partnered with Northrop Grumman to port the BGAN SDR waveform to their SDMD platform (Software Defined Multi-Function Device), which is a JTRS product. This project enables delivery of flexible BGAN capability to the U.S. military market. Going forward several porting projects are expected and discussions are ongoing with other U.S. defense integrators.

Following the above, the waveform will initially form a basis for a range of BGAN products in government/military/defence markets in the U.S. However, the focus is not limited to military markets or the U.S.

The BGAN SDR waveform also presents a strong value proposition to global civil markets within land, maritime and aeronautical segments by enabling a fast, and cost efficient, road to reliable BLOS (Beyond Line Of Sight) broadband on the move.

Status on technical BGAN SDR waveform development project—The waveform development is nearing completion and the waveform is running all BGAN data services as well as the circuit switched voice service, ISDN and SMS. Once the development is complete the waveform will offer the exact same capabilities as a dedicated BGAN terminal, and will support all classes of operation in compliance with Inmarsat requirements.