Russia Approves CDMA Signals for GLONASS, Discussing Common Signal Design
April 28, 2008
Nearly 30 years after the first launch of a GLONASS spacecraft, Russia is moving to add code division multiple access (CDMA) signals to the frequency division multiple access (FDMA) format that has set the world’s second-oldest global satellite navigation system apart from GPS and other systems under development.
A February 15, 2008, government decree on new GLONASS requirements calls for open CDMA signals with a binary offset carrier or BOC (2,2) signal structure centered at 1575.42 MHz and a BOC (4,4) signal centered at 1176.45 MHz — essentially corresponding to the center points of GPS signals at the L1 and L5 frequencies and nearby Galileo and Compass signals.
An additional GLONASS FDMA signal will be located at L3 frequencies (1197.648–1212.255 MHz), just below the GPS M-code at L2.
Russia will implement the new signals on the next-generation GLONASS-K satellites, with the first launch currently expected in late 2010 with flight testing the following year.
Use of FDMA GNSS techniques, in which the same code is used to broadcast navigation signals on different frequencies, and the placement of civil GLONASS transmissions on frequencies between 1598.0625 and 1606.5 MHz well above the GPS L1 band, have complicated the design of combined GLONASS/GPS receivers, particularly low-cost equipment for mass market applications.
The new performance requirements and modernization plans were described in an April 7 presentation at the Moscow International Satellite Navigation Forum, by Yuri Urlichich, general director of the Russian Institute for Space Device Engineering (RISDE) and chief designer for GLONASS, and by Sergey Revnivykh, deputy director of the Russian Space Agency’s Central Research Institute for Machine Building (TsNIIMASH) and head of the Information Analysis Center for Positioning, Navigation, and Time, addressing an April 23 plenary session at the European Navigation Conference 2008 in Toulouse, France.
Under the new plan, Russia will continue expansion of its ground control network, including establishment of new monitoring stations outside Russia’s borders for the first time. Improved timing and orbit determination are planned to enable the system to match GPS system performance by 2012.
GLONASS is in the seventh year of a 10-year program to rebuild and modernize the system. Funding under that plan is committed through 2011, with additional revenues now being sought to support the new requirements document, Revnivykh said.
Revnivykh noted the personal backing that GLONASS has received from President Vladimir Putin, whose term ends May 7 following which he is expected to be appointed prime minister by his successor Dimitri Medvedev. “We appreciate that as president Mr. Putin has been a big supporter of GLONASS. We hope that he will be a supporter as prime minister.”
GLONASS positioning and timing accuracy are currently about seven years behind that of GPS, Renivykh said. Nonetheless, improved atomic clocks on board modernized GLONASS satellites (GLONASS-M) launched in recent years have already produced substantially improved user range error (URE) figures, he added.
Promoting Russia's Consumer GNSS Markets
Adding the CDMA signals reflects the Russian government’s mandate to increase compatibility and interoperability with open services provided by other GNSS systems, driven in part by a desire to accelerate adoption of GLONASS in consumer products. Promoting development of civil GNSS chips by Russian companies is among the goals of the GLONASS directive.
In his presentation, Urlichich presented data released in January 2008
S. B. Pisarev, director general of the Russian Institute for
Talks are under way by joint technical working groups with the United States and Europe to further increase signal compatibility, including possible adoption of the multiplex BOC waveform agreed to by the latter two countries for new L1 civil signals in GPS and Galileo.
“We want to provide benefits for all civil users,” Revnivykh told a press conference at the ENC 2008. “But we also have to take into account that GLONASS is a dual-use [civil/military] system and that security issues are involved.”
He added that a completed GLONASS constellation will all GLONASS-K or later generations of satellites should be in place in the 2017–2020 time frame. “We have to ask what would be the greatest benefit of signal designs to users then.”
After gas and oil, GLONASS is another economic resource that Russia has to offer to the world, Revnivykh commented to Inside GNSS during a later conversation.
An Expanded GLONASS Constellation
The GLONASS constellation will ultimately be expanded from the current fully operational constellation (FOC) of 24 satellites to 30 satellites “at a minimum,” Revnivykh said. However, creation of a larger constellation will require upgrades to the GLONASS control segment, which currently can handle only 24 spacecraft.
Russia currently has 16 operational satellites in orbit and plans to add another six GLONASS-M satellites this year with triple-spacecraft launches in September and November. Three remaining older-generation GLONASS satellites will be decommissioned by the end of this year, Revnivykh added.
Terrestrial and space-based augmentation systems are also under development to improve real-time accuracy of GLONASS. The modernization plan also supports design and manufacture of GLONASS or combined GLONASS/GPS for military and other government users of navigation equipment, as well as assistance for designing and manufacturing of combined GLONASS/GPS/Galileo equipment to help develop mass-market navigation services.
Russia is a member of the UN-supported International Committee on GNSS (ICG) and its Providers Forum. It will host the fourth meeting of the committee in Sochi on the Black Sea in the autumn of 2009.
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