GLONASS Receivers

GLONASS
Title	GLONASS Receivers
Author(s)	GMV
Level	Basic
Year of Publication	2011

A GLONASS Receiver is a L-band radio processor capable of solving the navigation equations in order to determine the user position, velocity and precise time (PVT), by processing the signal broadcasted by GLONASS satellites.

GLONASS Receivers

A GLONASS Receiver is a device capable of determining the user position, velocity and precise time (PVT) by processing the signal broadcasted by satellites. Any navigation solution provided by a GNSS Receiver is based on the computation of its distance to a set of satellites, by means of extracting the propagation time of the incoming signals traveling through space at the speed of light, according to the satellite and receiver local clocks.

Notice that satellites are always in motion, so previous to obtaining the navigation message, the satellite’s signal is detected and tracked. The receiver’s functional blocks that perform these tasks are the antenna, the front-end and the baseband signal processing (in charge of acquiring and tracking the signal).

Once the signal is acquired and tracked, the receiver application decodes the navigation message and estimates the user position. The Navigation Message includes:

• Ephemeris parameters, needed to compute the satellite’s coordinates
• Time parameters and Clock Corrections, to compute satellite clock offsets and time conversions
• Service Parameters with satellite health information
• Almanacs, needed for the acquisition of the signal by the receiver. It allows computing the position of all satellites but with a lower accuracy than the ephemeris

The ephemeris and clocks parameters are usually updated every half-an-hour, whereas the almanac is updated at least every six days.

For more information, please refer to article GLONASS General Introduction and GLONASS Interface Control Document which specifies parameters of interface between GLONASS space segment and user equipment in L1 and L2 Bands.

Civil/Commercial use

Comparing to GPS system, GLONASS use in civil/commercial applications is rare. One of the main differences between GPS and GLONASS is that the former uses CDMA technique to separate the satellites while the later uses FDMA technique. The main impact at receiver level is that GLONASS receiver are in general more expensive since thy require higher IF bandwidths and hence they need more complex hardware. The migration of GLONASS system towards CDMA techniques may reduce the cost at receiver level.

To improve this situation, the Russian government has been actively promoting GLONASS for civilian use. In February 2011, the government announced that all passenger cars, large transport vehicles and vehicles transporting dangerous materials will be required to use GLONASS-equipped navigators as of July 2011. The tracking of this road traffic will be tied to road tax collection as well as to a roadside assistance in the event of an accident. The tracking system, known as ERA, will begin testing in July 2011, with transponders becoming mandatory in all vehicles by 2014. As well, the government is planning to force all car manufactures in Russia to make cars with GLONASS starting from 2011. This will affect all car makers, including foreign brands like Ford and Toyota, which have car assembling facilities in Russia.

Commercial response to GLONASS improved accuracy is gaining momentum, and many GNSS Receivers manufactures are developing GPS+GLONASS receivers. There are several recent announcements that include:

• Qualcomm has announced the first GLONASS capable phone (MTS 945 from ZTE): "ZTE is first to market with a smartphone that supports both the GPS and GLONASS satellite systems, taking full advantage of the functionality which has been integrated into our Snapdragon MSM7x30 chipset and software”.
• In February 2011, ST-Ericsson launched “the world’s smallest receiver” to connect to both GPS and GLONASS satellites.
• Broadcom Corporation, a global leader in semiconductors for wired and wireless communications, announced two new GPS system-on-a-chip solutions that include support for the GLONASS Russian Navigation Satellite System.
• In April 2011, Sweden’s Swepos became the first foreign company to use Russia’s GLONASS positioning technology, due to Swepos’ conviction that it is better than GPS at northern latitudes.