Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Second-hand satellites may gain new voice

05.02.2003


ESA engineers are proposing a technique to enable a digital satellite radio service for European drivers - without the need to launch a single new satellite into orbit.



Commercial digital satellite radio is already a reality in the United States, using a costly set of dedicated satellites. The rival American services allow subscribing drivers to choose between numerous near-CD quality radio channels without tune-out or static.
Two parallel ESA studies have examined a lower-cost method of providing in-car Europe-wide satellite radio, along with supplemental text, pictures and video data. ND Satcom (prime contractor), DLR, IMST and SES Astra conducted one of the studies while Alcatel Space (prime contractor), Frauenhofer Gesellschaft, Skygate and SES Astra performed the other.

"This service would include music and voice data," said ESA engineer Rolv Midthassel from the Technology Projects Division of the Telecommunication Department. "Plus additional data could be displayed on-screen such as information on songs, traffic and weather forecasts, and other services dedicated to car drivers."



It promises to be much cheaper to set up than US satellite radio, because it requires no new expensive satellite launches. Instead the proposal is to reuse existing TV satellites nearing the end of their operating life.

Once in position, 35,000 km away in space, TV satellites will remain in orbit forever, but their useful life amounts to 15 years or less. Onboard thrusters must keep each satellite pointed precisely in geostationary orbit so they stay lined up with fixed-position Earth-based receivers.

However once the thrusters’ propellant runs out the satellites drift out of correct orbit, and are left useless for TV broadcast applications. But further life can be squeezed from a low-propellant TV satellite switched over to mobile digital radio broadcasting where precision position control is less important.

Most thruster propellant is expended correcting satellite attitude in the north-south direction. But if station-keeping is limited to the east-west axis then satellite lifetime could be extended by some five years.

The satellite’s position would oscillate across the sky by a few degrees. But vehicle-mounted digital radio antennas would keep track of the satellite as it moves, just as they would maintain contact with it as the car bearing the antenna moves across the landscape.

"Satellite reception is frequently shadowed by trees, rain, or cloud or blocked altogether by mountains, tunnels or tall buildings," explained Midthassel. "In urban areas the studies indicate that the signal is blocked an average 30 per cent of the time, maybe for several minutes at a time."

These reception gaps make real-time broadcasting impracticable. Instead the service would operate on a cache system – data files are stored by the receiver for later playback.

"Sophisticated interleaving, data coding and large signal margins should enable the useful data to be reconstructed even when some of the signal has disappeared," said Midthassel.

Interleaving is a method whereby the burst of erroneous data arising from blockages and shadowing will be spread out in time and mixed with correctly received data bits. And coding data will then enable the receiver to interpret it in the correct context.

Studies indicate a useful data rate of a million bits per second per satellite transponder. With each satellite having several transponders, this makes the system performance comparable or even superior to US services.

"The receiver cache will contain files like songs, news flashes, and discussion programmes," Midthassel added. "Based on a pre-set user profile an individually-tailored radio programme could be constructed out of available files."

"Alternatively the user could choose which service he wants from the cache – so you could play the latest news then and there instead in a half-hour’s time. Exiting the car to fill up with petrol, you could halt the news then restart it once you’re back."

Test reception measurements have been carried out by both teams monitoring signals from SES Astra satellites.

The next steps come this year, with plans to design a low-cost fully electronically steerable antenna as well as develop a suitable gateway transmitter and user receiver which shall serve as a system demonstrator for extended field testing.

Dominique Detain | alfa
Further information:
http://www.esa.int/export/esaSA/SEM67L1A6BD_telecom_0.html

More articles from Communications Media:

nachricht New Technologies for A/V Analysis and Search
13.04.2017 | Fraunhofer-Institut für Digitale Medientechnologie IDMT

nachricht On patrol in social networks
25.01.2017 | Fraunhofer-Institut für Arbeitswirtschaft und Organisation IAO

All articles from Communications Media >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>