GNSS Over China: The Compass MEO Satellite Codes

Compass M-1 Launch, April 14, 2007

With the launch of its first middle-earth-orbiting (MEO) Compass satellite, China has put forth its GNSS entry. The key to using and understanding the performance of the Compass M-1 navigation signals is revealed by its spread spectrum code. This article by a team of Stanford University researchers presents the spread spectrum codes being broadcast by this satellite.

Grace Xingxin Gao, Alan Chen, Sherman Lo, David De Lorenzo, Per Enge
(Stanford University)

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On April 14, 2007 (local time), China launched the Compass M-1 satellite. This satellite represents the first of a new global navigation satellite system (GNSS) that is planned to have a total of 35 satellites. Unlike prior Chinese navigation satellites, Compass M-1 broadcasts in L-band, using signal structures similar to other GNSS systems and sharing frequencies near to or overlapping those of GPS, Galileo, and GLONASS.

The addition of another GNSS, particularly one that will broadcast in the same frequency bands as GPS and Galileo, both excites and intrigues the GNSS community. Such a system has the potential to introduce benefits – as well as concerns – for GNSS users. Numerous researchers around the world, including Stanford University (SU), have been interested in examining the navigation signal of this system.

To understand its effects and to develop receivers that can track the signal, one must understand the signal structure being used. In the case of Compass, this means determining and understanding its spread spectrum codes. This article will present the Compass codes and provide an overview of how our team at Stanford determined these.

(For the rest of this story, please download the complete article using the PDF link above.)

Manufacturers

Stanford University researchers use an Agilent 89600 vector signal analyzer from Agilent Technologies, Palo Alto, California, USA, to collect signals received at the SGMS. The skyplot in Figure 1 was generated with satellite tracking software, Nova for Windows, developed by Northern Lights Software Associates, Jamesville, New York, USA.

Author Profiles

Alan Chen is a Ph.D. candidate in the department of Aeronautics and Astronautics at Stanford University. He received an M.S. from that department and received his S.B. degree in aeronautics and astronautics from MIT. His current research interest involves unexploded ordnance, sensor fusions, autonomous helicopter, and GNSS signals.

David De Lorenzo is a research associate at the Stanford University GPS Research laboratory. He received the Ph.D. in aeronautics and astronautics from Stanford University with thesis research on adaptive antenna arrays, their ability to reject radio frequency interference, and their impact on GPS measurement errors. He has previously worked for Lockheed Martin and for the Intel Corporation.

Per Enge is a professor of aeronautics and astronautics at Stanford University, where he is the Kleiner-Perkins, Mayfield, Sequoia Capital Professor in the School of Engineering. He directs the GPS Research Laboratory, which develops satellite navigation systems based on the Global Positioning System (GPS). He has been involved in the development of Federal Aviation Administration’s GPS Wide Area Augmentation System (WAAS) and Local Area Augmentation System (LAAS) for the FAA. Enge has received the Kepler, Thurlow, and Burka Awards from the Institute of Navigation. He received his Ph.D. from the University of Illinois.

Grace Xingxin Gao is an Electrical Engineering Ph.D. candidate in the GPS Laboratory at Stanford University. She received a B.S. in mechanical engineering and her M.S. in electrical engineering from Tsinghua University, Beijing, China. Her current research interests include Galileo signal and code structures, GNSS receiver architectures, and GPS modernization.

Sherman Lo is a research associate at the Stanford University GPS Research Laboratory managing the assessment of Loran for civil aviation and also works on a variety of GNSS-related issues. He received his Ph.D. in aeronautics and astronautics from Stanford University. He has received the Institute of Navigation (ION) Early Achievement Award and the International Loran Association (ILA) President’s Award.