Compass ICD in October; Harmonizing GNSS

September 29, 2011  - By 0 Comments

China’s GNSS, Compass or Beidou, intends to publish its signal interface control document (ICD) in October. Representatives of the system made an unprecedented showing at ION GNSS in Portland, and referred frankly to “internal deliberations” that may be at the root of much of the public uncertainty about the system’s planned structure and timeline. Meanwhile, representatives of other navigation satellite systems also delivered updates on their status and plans. Everyone is concerned about LightSquared interference, but everyone continues to move forward.

This month’s column is a two-parter: a guest appearance by Len Jacobson, editorial advisory board member for GPS World magazine and president of Global Systems and Marketing Inc.  Len writes on the “Harmonizing GNSS” aspect, the briefings by all systems and their efforts to achieve compatibility and interoperability. Then I’ll return with an account of the Compass panel that formed part of the CGSIC meeting immediately preceeding ION.


len_jacobsonHarmonizing GNSS

by Len Jacobson

Representatives of the International Committee on GNSS (ICG) participated in briefings and a panel discussion at the ION-GNSS Conference in Portland on Thursday, Sept. 22, 2011. The ICG is a committee formed under the auspices of the United Nations Office of Outer Space Affairs. The purpose of the panel was to acquaint the audience with the activities of the ICG and to allow the global and regional satellite navigation systems providers to describe their policies and efforts with regard to interoperability and compatibility among the various GNSS and to advise how multi-GNSS services could be harmonized.

Rick Hamilton from the U.S. Coast Guard Navigation Center organized the panel, and Jeffrey Auerbach, from the same U.S. Department of State (DOS) office as the U.S. ICG representative Dave Turner, moderated it.

The first speaker was Sharafat Gadimova, from the ICG Executive Secretariat. She described the functions and make-up of the ICG and suggested visiting their web site www.icgsecretariat.org for further information. The next meeting of the ICG is scheduled for December 4–9, 2012 in China.

David Turner, the deputy director of the Office of Space and Advanced Technology in the DOS, reiterated the President’s 2010 Space Policy and in particular the addition emphasizing international cooperation and more use of foreign systems by the U.S. government to enhance GPS. Turner co-chairs Working Group (WG)-A on compatibility and interoperability. He discussed a Multi-GNSS Monitoring Network using new and existing GNSS monitoring receivers and networks. He stated that the various GNSS geodetic and timing references can be found on the ICG web site.

Dr. Sergey Revnivykh, deputy director-general, GLONASS Information and Analysis Center, stated his desire that all GNSS be considered equal. In this sense, Russian policy differs from U.S. policy, which considers GPS as the premier GNSS. Dr. Revnivykh discussed the GLONASS System of Differential Correction and Monitoring (SCDM), the Russian version of WAAS. It will augment both GLONASS and GPS. He had to leave after his presentation so was not able to participate in the ensuing panel discussion.

Independently, we have learned from GLONASS communications that the launch of GLONASS-M No. 42 from Plesetsk is scheduled to take place on October 1 at 20:19 UTC. The launch of GLONASS-M Nos. 43, 44, 45 from Baikonur may occur as early as November 2. The launch of GLONASS-M No. 46 from Plesetsk is now scheduled for November 22. The launch  of the next-generation GLONASS-K1 No. 12 from Plesetsk will likely slip to 2012. Additionally, Luch-5A, a Russian geostationary communications satellite that includes an SBAS payload, will launch together with Amos-5, a Russian-built Israeli communications satellite, on December 10 from Baikonur.

Next we heard a short briefing by Xavier Maufroid from the Galileo Implementation office of the European Commission in Belgium. He stressed compatibility with all services, and then interoperability. He stated that the European Union (EU) is concerned about LightSquared (LS) because LS transmissions could affect Galileo reception in the United States and also could expand to provide a similar disruption in Europe if they were to expand into that area. And if not LS, then someone else could attempt a similar broadband service over Europe with the same potential to interfere with Galileo. He later added that 7 billion euros are budgeted for Galileo between 2014 and 2021.

From the Chinese Electronics Technology Group came Dr. Xiancheng Ding, the deputy director-general. He described Beidou (Compass) as having nine satellites with five more to be launched in 2012. This will provide regional service by the end of 2012, including over Australia and New Zealand. Beidou has a communications capability for short messaging, which is needed in rural China.

Dr. Ding said the Beidou signal interface control document (ICD) would be released soon. Other sources indicate it to be as early as October 2011. He indicated that Beidou is fully funded for phase 2 (regional system) and will probably be funded for phase 3 (global system).

The final briefer was Dr. Satoshi Kogure from the Japan Space Ageny. He gave a QZSS update similar to one given in other ION GNSS sessions.

During the panel interchange and answers to questions from the audience, various combinations of signals were discussed as needing to be compatible. That is, to not interfere in same frequency band and to comply with International Telecommunications Union (ITU) regulations. Specific signal pairs mentioned in this context included: GPS L1 and L5 with Galileo; Compass and future GLONASS CDMA; the QZSS LEX with Galileo; and others.

A WG-A workshop proposed jointly to ICG to study the potential noise impact of too many satellites. By 2020, more than 100 satellites are expected to be transmitting the myriad of GNSS signals, with up to 35 in view at any one place. This could cause mutual interference, which in turn could cause degradation in the levels of service of the various GNSS.

Dr. Kogure described a Multiple GNSS demo campaign sponsored in part by the Japanese Space Agency consisting of tens of receivers monitoring GNSS signals over Asia and the Western Pacific. For multi-GNSS testing there is better availability in these region as there are initially more GNSS signals in view. This experiment is a prototype of a multi-GNSS monitoring network with 20 QZSS receivers by March of 2012 and 40 by a year later. China will supply Beidou receivers to Japan for the multi-GNSS Monitoring Network in cooperation with the ICG. There will be a workshop on this topic in November in Korea.

There is still an issue between China and the EU on frequency compatibility for authorized services, but Dr. Xiancheng said a technical solution is known. Negotiations are still ongoing.

All members of the panel were cognizant of the LS problem and are focused on providing interference detection and mitigation for their GNNS.


Compass ICD in October

The long-awaited signal interface control document (ICD) for China’s growing GNSS will appear this month, according to representatives of the system who spoke in a “Compass: Progress, Status, and Future Outlook” workshop as part of ION GNSS and the CGSIC meetings in Portland in September.

The ICD has been rumored to be available previously to receiver manufacturers within China, creating some disgruntlement among companies outside the country. One of the workshop panelists affirmed that GPS/Compass chips and receivers are being actively developed by many Chinese manufacturers and research institutes.

The ICD announcement came among many valuable pieces of information presented during the pre-ION workshop, sponsored by the International Association of Chinese Professionals in Global Positioning Systems. The workshop was chaired by Jade Morton, professor of electrical and computer engineering at Miami University, Ohio.

Dr. Xiancheng Ding of the Beidou Program Office described Compass as a demo system in transition to an operating navigation system. Two more satellites will launch in 2011, making a total of five new space vehicles this year,as part of a total “simple navigational system” of nine satellites that has been built up, and what is termed a “test system” over the Asia-Pacific region, to be complete by the end of the year.

Five more satellites will rise into orbit in 2012, and the system will graduallly extend its coverage and improve its performance. Compass will start official regional service by the end of 2012, meeting user requirements in the Asia-Pacific region.

ICD document v1.0 will be published in 2011, and probably in the month of October. It will be available for international download on the Compass website, www.beidou.gov.cn (as yet without an English version), also at www.compass.gov.cn.

There was some disagreement among panelists as to the final targeted number of satellites in the system: either 30, or 35. Subsequent comments indicated that much of the structure may still be under discussion. The impression given was very much of a dynamic system in formation and growing rapidly.

In a presentation on “preliminary Results of GPS/Compass Integrated Positioning and Navigation,” Dr. Uanxi Yang of China’s National Administration of GNSS and Applications reported integrated navigation with a Unicore UB 240 Compass/GPS receiver, and also mentioned a Shanghai Huace Compass/GPS receiver. Some systematic errors in Compass positioning were reported, and attributed to the sparse satellite distribution currently.

Dr. Yang concluded with the exhortation, “Reasonable Wishes for Compass!” emphasizing the desire of the delegation to continue working hard on, but with realistic expectations for, the new system.

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Alan Cameron

About the Author:

Alan Cameron is editor-in-chief and publisher of GPS World magazine, where he has worked since 2000. He also writes the monthly GNSS System Design e-mail newsletter and the Wide Awake blog.

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