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Great expectations for Galileo users

Posted: 18 Jun 2008     Print Version  Bookmark and Share

Keywords:satellite navigation system  base band  radio front-end  GPS 

Much of the discussion of Europe's fledgling satellite navigation system, Galileo, has focused on the political wrangling over the funding of the ambitious project and the delays this is causing. However, there is a wealth of R&D under way to ensure there will be working terminals available when, if not before, the system is in commercial operation in 2012 or 2013.

Behind the scenes, several programmes are under way, many co-funded by the European Global Navigation Satellite System (GNSS) Supervisory Authority and through the European Commission's Framework Project that aids technology across a host of areas. One of these, dubbed the GREAT Consortium (for Galileo REceiver for the mAss markeT) has just completed its two-year project and delivered a library of demonstrable IP for future receivers as well as a combined Galileo/GPS receiver with prototype base band and a wideband dual-frequency radio front-end.

The completion of the project was timely as the mood is changing about the commercial viability of the venture as key technological milestones are reached. For instance, the planned constellation of 30-satellites to rival the American GPS system received a boost last month when Giove-B, the second demonstrator satellite, was successfully launched into orbit and immediately started transmitting and receiving signals. Giove-B, built by a consortium led by Europe's largest satellite concern, Astrium, is crucial to the success of Galileo as it will test and verify the receive and transmit capabilities of what is planned for the commercial satellites.

The first demonstrator, Giove-A, built by a consortium led by Surrey Satellite Technology Ltd., recently acquired by Astrium, has been laying the ground work and operating successfully for three years.

Within the GREAT Consortium, the RF front-end part of the project was led by Spanish design and manufacturing group Acorde that targets the satellite communications sector, while the base band prototype was done by a group led by GPS chip specialist u-blox AG.

The RF part operates in the L1-E1 and L5-E5a GNSS bands and provides immunity to wireless control systems (WCSs) interferences as well as an analogue IF signal compatible with the advanced base band processing. The base band also implements advanced multi-path algorithms developed by researchers at Tampere University, Finland.

MMIC (above) and filter board (below) developed during the GREAT Consortium project.

The consortium was led by PA Consulting (Cambridge, England), and also includes Qualcomm CDMA Technologies GmbH and the German Aerospace Center, DLR.

"Our approach has focused very much on the premise that when these terminals come into use, almost all applications will also need a cellular link and must be able to operate in low-signal environments, and thus must not show any loss of signal strength or delay as users transition from outdoors to inside buildings," project manager Graham Bell at PA Consulting told EE Times.

"We really do not expect there to be pure Galileo terminals; they will be general GPS terminals with cellular capabilities that can make use of available satellites for global positioning and location."

While the project has now been completed and, according to Bell, has created a base band and RF front-end believed to be ahead of anyone else, "We are not resting on our laurels. We have put forward follow on proposals to further exploit the technologies developed within the GREAT project, as part of the seventh Framework Program, and expect to get assistance to move to the next phase."

"The proposals represent a logical continuation of the work we have achieved, and will see the prototype developments get nearer to commercial reality." Bell noted that other advanced algorithms have been developed, notably at DLR, demonstrating the benefits of Assisted-GNSS and Hybrid Data Fusion (HDF) for the mass market, at least in simulation.

Assisted-GNSS extends sensitivity and decreases acquisition time, thus reducing the power consumption, while HDF exploits the already available capabilities of a cellular network to determine the mobile station location, extending the availability of GNSS in critical scenarios, such as urban canyons and inside buildings.

Acquisition time is reduced as the Doppler and code phase search space is much smaller, while search speed is increased, enhancing sensitivity and thus allowing the receiver to dwell longer in each code/Doppler search bin. The multi-path mitigation algorithms developed within the project will also play a role in reducing multi-path errors in complex urban scenarios, leading to more accurate and speedier positioning.

"Availability, Time To First Fix (TTFF) and power consumption are key technical challenges that must be addresses to achieve mass adoption of the technology," said Bell.

In terms of power efficiency, the prototype base band and RF front end developed within the project is "pretty near to that of today's commercial chips for GPS devices," he said.

The current prototype base band is in the form of an FPGA but "u-blox believes it can turn that into a commercial part within six months." When that happens will depend on whether the market is ready for such a device. Bell is adamant that companies working on devices and chipsets for combined Galileo/GPS terminals, such as u-blox, Texas Instruments, Qualcomm,

STMicroelectronics, CSR and NXP, "will have devices for terminal makers in place and production well before the Galileo system is fully turned on for commercial use."

- John Walko
EE Times Europe

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