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Post Info TOPIC: Four satellite navigation constellations set to be in place by 2020


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Four satellite navigation constellations set to be in place by 2020

Galileo, Europe's fledgling global navigation satellite system (GNSS), is facing another crucial and hectic year.

On the agenda are testing and monitoring the first signals transmitted from the two in-orbit validation (IOV) satellites launched late last year; readying the launch of six more satellites; and, perhaps somewhat incongruously for a huge and strategic project well into its second decade, a marketing push.

"The deployment of the constellation is important. But what is more important is creating tangible benefits for European citizens and business," said Antonio Tajani, vice president of the European Commission, which has been driving the project from its inception alongside the European Space Agency (ESA).

Speaking at a conference in London in December 2012, Tajani urged European manufacturers to incorporate Galileo capability into their products and services and said more collaboration will be needed between chip manufacturers, receiver designers and service providers to get things up and running.

The attraction to all playeres is the value of the GNSS based services sector; already exceeding 100billion a year, the market is set to double by 2025 once all systems are in play.

First proposed in the late 1990s as a rival to the US Global Positioning System (GPS) that began more than a decade earlier, the Galileo project had lofty and strategic targets. It would be technically more accurate, civilian led, commercially profitable and, by inference, not at the mercy of the Pentagon which, the argument went, could turn off GPS signals for civilian use when it suited.

The reality has been quite different, due to a mixture of political detours (the original public-private partnership model was debunked back in 2007), technical delays, and on going arguments about budget overruns and future budgets. The latter continue to blight the project.

While the project moves into the crucial deployment phase to meet the 2014 timeline for initial services, the technologists, satellite providers and receiver designers are waiting on European parliamentarians to approve the hard fought budget deal secured in January 2013. That would see 6.3bn allotted to Galileo between 2014 and 2020 for finishing the infrastructure and for operational costs only 10% less than the European Commission's previously revised proposals.

The commercial landscape has also seen significant changes and it is now clear Galileo will not as originally planned be the second GNSS. Instead, it will only be available after Russia's revitalised Glonass project and possibly only fully deployed after China's Compass/BeiDou-2 system. And the next generation GPS III technology being readied will likely steal some of the thunder from Galileo's once perceived technical advantages.

Then there are regional players, such as Japan's Quasi-Zenith Satellite System and the Indian Regional Navigation System. Both have already had their signal and constellation parameters incorporated into GNSS simulator products, so they will be ready for adoption as they mature.

All this with the ever increasing number of satellites being made available and much work into improving positioning in signal challenged environments such as urban canyons is clearly a huge opportunity for receiver designers and suppliers of devices such as chip sets, rfics, antennas and low noise amplifiers.

System integrators and receiver makers are already designing multifrequency products which exploit combinations of the four GNSS systems, with high cost, professional equipment available that relies on GPS and Glonass. A myriad of research projects is targeting the consumer opportunity, with companies such as STMicroelectronics, u-blox, CSR, Broadcom and Qualcomm waiting in the wings, eager to implement Galileo's capabilities now that test signals are being transmitted from the IOVs.

"It is very exciting right now," Dr Philip Mattos, technical director and chief engineer, GNSS, for STMicroelectronics told New Electronics. "Over the past few weeks, we have been receiving real data from the Galileo satellites and we now have the full specifications for the Chinese Compass/Bei Dou B1 capability for civilian receivers. This has given multifrequency GNSS receiver development a real boost."

But the technologists are also well aware that ensuring interoperability is and will be a huge challenge and that the great aspirations of the four operators will need to be translated into better harmonisation.

Javier Benedicto, Galileo project manager with ESA, told New Electronics the main technical target for Galileo in 2013 will be to get a reliable position fix. "This will happen soon after the second set of satellites launched in October is commissioned." Four satellites is the minimum needed to test services rigorously. Full IOV is expected to be completed by October or November. "Achieving that will be helped by the experience we have gained from the two pathfinder satellites, Giove-A and Giove-B."

Giove-A and -B were launched in 2005 and 2008 respectively, the latter built by microsatellite pioneer Surrey Satellite Technology (SSTL), now owned by EADS Astrium. They were also the test beds for receivers on the ground, as well as two control stations and 15 groundstations.

"Full validation takes time," said Benedicto. "We have to refine radiation models, check communications with numerous ground stations and ensure the working of the two atomic clocks (one rubidium, the other based on a passive hydrogen maser) that we developed specially for the project and which are the most advanced and accurate of their type to date."

ESA claims that, with the help of these clocks, Galileo satellites will be able to offer positional accuracy in the range of centimetres and timing accuracy in the order of nanoseconds.

Benedicto stresses the satellite constellations are not competitive and, from the point of view of the customer's receiver, should be seen as harmonised and complementary. The exciting aspect of all the global developments is that, through harmonisation, users will be able to access signals from multiple systems to achieve really high accuracy and a faster way to get a positional fix. "We are actively promoting applications in several sectors, but this will need a coordinated approach at the global level."

He also cautions that it is vital to ensure the numerous satellite systems do not interfere with each other. For instance, while GPS and Glonass operate in the L1, L2 and L3 bands, Galileo has been assigned frequencies in the L1, L6 and E1, E2, E5 and E6 bands, between 1.156 and 1.610GHz.

Benedicto also stresses that existing GPS receivers will not benefit from the 'reality of Galileo' because of these different frequencies, modulations and data formats. "Users will need new chip sets. The good news is that chip makers have been designing that capability into their latest multichannel designs. I believe there are already 30million Galileo capable chip sets out there."

The plans call for 18 satellites to be in orbit by mid 2014, providing an initial commercial service, as well as the free of charge Open Service and a demonstration of the secure encrypted Galileo signal for the Public Regulated Service offering. The satellites will also support the important search and rescue capability. The orders for the 14 satellites have gone to Germany's OHB-Systems for the platform, with SSTL responsible for the payload.

The next milestone is to place 24 satellites in orbit for full operational capability (FOC), followed by completing the 30 satellite constellation by 2018 at the latest a decade later than the project's original schedule.

But, as Benedicto retorts, GPS also had its own teething problems despite full backing from the US military and was used for a long time before reaching its FOC. He also notes that, at one stage, Glonass was heading into deep problems. "So I think we are doing pretty well," he concluded.

Designing the components

Much of the focus on the Galileo project has been on the design and implementation of the infrastructure. But an equally important and, for the components sector, possibly more significant activity has centred on defining the architecture of the rf front end and baseband sections for a variety of working multifrequency receivers and readying them to be implemented at minimal cost, once the network is fully functional.

There are, and have been, numerous European R&D projects targeting the opportunities provided by the diversity and redundancy of independent, compatible and hopefully interoperable GNSSs. One of the most exciting is the UK's iNsight (Innovative Navigation using new GNSS Signals with Hybridised Technologies) programme. This has a budget of 4.75million, including 2.75m from the EPSRC.

The four year project, which is nearing completion, links Imperial College, UCL and Nottingham and Westminster universities with industrial partners such as STMicroelectronics, EADS Atrium, Leica Geosystems, Nottingham Scientific, QinetiQ and Thales Research and Technology.

From the hardware point of view, The University of Westminster team looked at tracking channel structures and receiver architectures. "We have developed a discovery enabling receiver platform that will allow experimenters to investigate different approaches and to do this very quickly," said Professor Izzet Kale, head of the applied DSP and VLSI research group at the University's school of electronics. "It will reduce complexity for multichannel receiver designers significantly and provide an infrastructure for people to try new ideas without reinventing the world. For instance, designers can acquire GNSS signals simultaneously, maybe receive Wi-Fi as well.

"The digitally configurable some would describe it as 'software defined', although I do not like the term platform will convert all the different constellations' frequencies and handle any complex numerical processing tasks in the digital domain."

The key, Prof Kale added, is two separate rf channels synchronised with a single master atomic clock and two antennas. The dual multifrequency rf front ends connect to a high speed dual channel a/d converter that digitises and down-converts each incoming rf signal into an IF. The last part of the project is to integrate all this into low power, configurable fpga cores.

ST Microelectronics' role in the iNsight project is 'to review and monitor progress', according to Dr Philip Mattos, the chip maker's chief GNSS engineer, who added the company is very impressed with the results and is likely to use the group's design tool for next generation GNSS architectures.

For now, ST a significant player in multiconstellation receiver chips plans to implement Galileo compatibility in the software already embedded in many of its designs and thus at little extra cost.

But it is already looking at other approaches, one of which would be to design a low cost integrated chip with one radio, but with some 'pins' that would allow a second radio of the same design to be attached when used in a dual band receiver. This would lead to an rf front end that can be used interchangeably for different frequencies.

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