Global star

Globalstar logo

Globalstar is a satellite communication network similar to the Iridium network . This satellite constellation is based on 48 satellites that hover over the earth at an altitude of around 1400 km .

organization

The company was founded Globalstar by an association of worldwide leading telephone companies and equipment manufacturers such as Qualcomm , Alenia , China Telecom (HK), DACOM, DaimlerChrysler Aerospace , Elsacom (a Finmeccanica -Unternehmen), Hyundai , TE.SA.M (a France Telecom / Alcatel companies), Space Systems / Loral and Vodafone AirTouch. The company is managed by Loral Space & Communications.

System architecture and differences to Iridium

Mains supply

Footprints of the Globalstar satellites

The orbital inclination of the Globalstar satellites is 52 degrees (Iridium 86.4 degrees). As a result, Globalstar (like Inmarsat ) does not cover the polar caps . These are only supplied via the Iridium network.

Since the Globalstar satellites have no contact with each other, calls can only be forwarded if there is a ground station in the coverage area of the respective satellite . With Globalstar there must be a gateway within a radius of approx. 3000–3500 km so that the network can be used. With Iridium, on the other hand , calls are forwarded via satellite interlinks to the gateways in Arizona (USA) and Italy , while internal network calls are transmitted directly via the satellites.

With Globalstar, even internal network calls are always routed via the gateway on the ground and, if necessary, the conventional telephone network infrastructure (PSTN).

On the high seas as well as in large parts of Africa and South Asia, the Globalstar network sometimes has no reception, although the satellites theoretically cover these areas. With so-called extended coverage (via reflection of the signal on the sea surface), however, reception on the high seas (entire Caribbean, large parts of the North Atlantic) is also possible in some cases. However, the quality is subject to an even greater range of fluctuation.

Currently (as of January 2007) America (North, Central and South America), Europe (North, Central and South Europe), the Near and Middle East, North Africa, Australia / New Zealand and large parts of Asia are covered. At the end of 2009, another gateway went into operation in Nigeria, which supplies large parts of West Africa. However, so far only simplex data connections have been possible via this gateway. After long negotiations, the framework conditions for the operation of a gateway in South Africa have now been created. However, the gateway is no longer planned to start before 2009, since investing in the latest generation of technology makes more economic sense.

The current supply card of the respective service provider should always be consulted before using the system.

Simplex and duplex operation

In addition to a full duplex connection, Globalstar also offers the option of handling data traffic in simplex mode via its network. This offers the advantage that a connection does not have to be established, which significantly reduces the power consumption of the device. Areas of application for this are, for example, telemetry, weather data from remote stations or personal trackers. However, the disadvantage of these applications is that, due to the one-way communication, the user has no guarantee that his message was successfully transmitted. As a preventive measure, datagrams are transmitted several times in succession and with a time delay.

Gateways

Division of the gateway zones (as of December 2010)

The Globalstar system is operated by different gateway operators, each serving a separate region:

ELSACOM for Northern / Central and Eastern Europe (out of operation since March 30, 2011). The supply area of ELSACOM was divided between GlobalStar Europe and GlobalStar Avrasya.
Globalstar Europe for West / Central Europe
pivotel for Australia
Globalstar Korea / Globalstar Asia Pacific for Korea and parts of Asia (Pacific)
Globaltel for Russia
Globalstar Argentina (TE.SA.M. Argentina) for parts of South America
Globalstar do Brasil for Brazil
Globalstar Peru (TE.SA.M. Peru) for Peru, Ecuador, Bolivia (currently out of service)
Globalstar Américas for Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, Panama (currently out of service)
Global star México for Mexico
Globalstar Canada for Canada
Globalstar Avrasya (Eastern Europe without CIS, Eastern Mediterranean, parts of North Africa)
China Spacecom (no longer in service, territory taken over by GlobalStar Korea)

Network structure

Strictly speaking, the Globalstar network itself consists exclusively of the 48 satellites. This so-called Globalstar Air Interface (GAI) supports telephones according to the ANSI-41 standard as well as devices according to the SIM card-based GSM standard. Most gateways contain the necessary infrastructure for ANSI-41 as well as an MSC for switching calls according to the GSM standard. At the moment, however, only the ANSI-41 standard is supported in small areas in Southeast Asia and the Caribbean, which requires the devices to be registered with the service provider. A SIM card-based roaming is not possible here.

Accordingly, there are devices from Telit and Ericsson GlobalStar / GSM900 based on the GSM standard, which are based on SIM cards and also allow SMS reception and transmission according to the GSM standard. Qualcomm offers an ANSI-41 compliant CDMA / AMPS / Globalstar Trimode device as well as a pure Globalstar handset that also works according to the ANSI-41 standard. Aside from the lack of a SIM card, the main difference is the SMS restriction. So only messages with a maximum length of 35 characters can be received, which have to be sent via a Globalstar web interface. Due to the different standards, direct receipt of SMS from GSM networks is not possible, nor is it possible to send SMS. An advantage of these devices, on the other hand, is the support of the packet switched data service (similar to GPRS), which is not supported by the Telit devices, but is not available in the entire Globalstar network anyway. The Ericsson device can only transfer data in GSM mode. Due to the RoHS , only the Qualcomm GSP-1700 will be available in Europe in the long term, which at the request of Globalstar Inc. no longer has any terrestrial cellular components. In addition, both Ericsson and Qualcomm offer fixed installations according to the respective standard.

It should be noted that not all Globalstar providers have concluded roaming agreements with one another, so that coverage is not automatically guaranteed in the entire Globalstar network. Furthermore, when the devices are operated in the coverage areas of an external gateway, additional roaming charges are incurred, so that the service provider should be selected based on the destination country. While among other things z. For example, Germany, France and Great Britain are served by Globalstar Europe, whereas Italy, Switzerland and Austria are covered by Elsacom. A clear advantage over other satellite network operators is that the subscriber is assigned a conventional mobile phone number with the country code of the gateway operator, e.g. B. +33638, +33640 and +33641 for Globalstareurope (France) or +39310 for Elsacom (Italy). Since there are no additional costs for incoming calls in the coverage area of the home gateway, a Globalstar satellite telephone within the home gateway can be reached much more cheaply than other satellite networks.

The international Globalstar country code (+ 8818 / + 8819) has already been assigned and is primarily used by GlobalStar do Brazil. European customers also have the option of obtaining a number from + 8816/7-Gasse in addition to the primary Globalstar telephone number (+336) located in France. The network identifier assigned by the ITU was 901-04, but this has since been returned.

Some providers also offer roaming agreements with local GSM or CDMA operators so that indoor coverage can be achieved via locally available networks.

Data transfer

Globalstar delivers a higher data transfer rate (9600 baud = GSM CSD ) than the Iridium network (2400 baud). Furthermore, a cost-effective simplex data service for tracking solutions is offered in which the transmitters send data packets with position data after a predefined interval. These messages are not acknowledged. After receiving the first message, identical packets arriving later are discarded and not charged.

Air interface

The data transmission from the satellite to the handheld devices takes place worldwide in the S-band from 2483.5 MHz to 2500.0 MHz. Data transmission from the handset to the satellite takes place worldwide in the L-band from 1610.0 MHz to 1618.25 MHz. Globalstar has to share the frequency range in the L-band with Iridium . The current limit between Globalstar and Iridium is at 1618.25 MHz. In addition, the frequency range from 1610.6 to 1613.8 MHz is a very important and very protected frequency range for radio astronomy .

The Globalstar frequency range is divided into several channels using frequency division multiplexing (FDM). The digital data are coded using code division multiple access (CDMA) and transmitted in one channel. A Globalstar channel has a bandwidth of 1.23 MHz. Due to the limitations of the frequency range in the L-band by iridium and radio astronomy, a maximum of 3 usable Globalstar channels remain in the uplink .

Globalstar is the only civil satellite communication network ever implemented for satellite telephones that uses the advantages of code division multiple access (CDMA) . The code division multiple access (CDMA) is used by some military communications satellites for portable radio solutions used. One example is the American MUOS .

Roaming

A separate GlobalStar contract is not necessarily required to use the GlobalStar network, as there are roaming agreements with GSM network operators. Iridium, on the other hand, did not conclude any roaming agreements when the group was restructured, so that GlobalStar can definitely have advantages for occasional users (despite the limited supply). However, since the GlobalStar network is operated via several autonomous gateways, separate roaming agreements with the desired gateway are required. A roaming agreement with a single gateway does not automatically mean that roaming works across the entire network.

Overall, the operating costs of the Globalstar network are significantly lower than those of the Iridium network. For the end user, however, the complex tariff structure and the division into zones, especially when using external gateways, can result in significantly higher call prices than when using other satellite networks.

Network status

The Globalstar satellites orbit the earth at an altitude of around 1414 km. This altitude is usually avoided for satellite orbit because of the Van Allen Belt . The cause of the degeneration of the S-band transmitters is the so-called " South Atlantic Anomaly ", due to which the satellites are exposed to stronger cosmic radiation during almost every revolution, which severely affects the electronic components of the satellites. In the case of the Globalstar satellites, the amplifiers of the S-band satellite antennas suffer most. Telephone calls (two-way voice) and two-way data transmissions (duplex data service) are handled via the S-band satellite antennas of the Globalstar satellites.

In the meantime (as of August 2013) GlobalStar has completed the start of the second generation of satellites and all new satellites have been activated so that the GlobalStar network is now fully functional again. In the course of 2013/2014, further gateways in Singapore, Nigeria and Panama should expand the GlobalStar coverage area.

It is planned to replace the eight satellites that were launched in 2007 within the next few years, as these also belong to the old generation.

From 2007 to 2011, sometimes massive problems with telephone calls and two-way data transmission via the Globalstar satellites were to be expected. Simplex data connections (e.g. for tracking solutions) are not affected. Telephone calls (Two-Way Voice) and two-way data transmissions (Duplex data service) were e.g. B. in October 2006 and afterwards, i.e. before and during the preparation of the satellite constellation for the new satellites, is not always possible. Statistics on the S-band problem are provided by the Frost & Sullivan study from 2008. If one compares the measurement results from 2008 with the measurement results from 2002, the drop in performance of the S-band amplifiers (due to the harmful radiation) becomes clearly visible.

In order to defuse the S-band problem, four new satellites of the old generation were put into orbit on May 29, 2007 by Soyuz operator Starsem (NORAD 31571, 31573, 31574, 31576). Four more satellites (NORAD 32263-32266) followed on October 20, 2007, also from the Baikonur Cosmodrome . The eight new, fully functional satellites will compensate for the failures of the old satellites. In the meantime (July 2008) all eight new satellites have been activated and the quality of supply has improved significantly, even if it is very dependent on one's own latitude and longitude. However, GlobalStar provides a tool for calculating the supply times on its website free of charge.

According to press release. The second generation of Globalstar satellites will replace the 32 remaining first generation satellites from summer 2009. The first generation of satellites initially consisted of 52 satellites in orbit. 48 satellites were in service and four were in reserve. Due to the S-band problem, GlobalStar was no longer able to ensure network operation with the in-spare orbit satellites (i.e. the reserve satellites in orbit) and the on-board resources of the individual satellites concerned. Therefore GlobalStar decided to prepare and use the eight reserve satellites on the ground. These 8 further satellites of the first generation were deployed at an altitude of 920 km. Over time, they rose automatically to the operating altitude of 1414 km, where they then started operations. The second generation satellites were also launched at this altitude between 2010 and 2013 and also rose to their operating altitude of 1,414 km.

The satellite stock currently operates with 32 satellites, but without a reserve satellite in orbit. Due to the slightly different antenna geometry, however, almost the same quality of coverage can be achieved with 32 satellites as before with 48 satellites.

The availability of the network can be displayed worldwide on the coverage maps depending on the selected service.

The second generation satellites will not support satellite interlink either. Globalstar is therefore planning to expand its gateway network as part of the upgrade to the new generation of satellites.

On January 14, 2010, Globalstar started converting existing gateways in Argentina, Australia, Botswana, France, Korea and the USA for the new system. The focus here was on the Telemetry Control Unit (TCU), as this is where the greatest differences to the "old" system exist. As pure "amplifiers" are used in principle in the 24 new satellites, they are seamlessly compatible with the previous infrastructure and with devices that are already on the market. In the future, these 24 satellites will be sufficient for the entire coverage of the regions already served and will gradually replace the aging satellites. The new generation of Globalstar satellites will also have an improved telemetry system that will give the Globalstar Satellite Operations and Control Center in California better control options.

The validation tests (temperature / vacuum tests) for the new satellites have been completed and the first time window for the launch of initially six new generation satellites for a 90-day period from July 5, 2010 has been announced. On October 19, the first six satellites were successfully launched into space with a Soyuz. Two of the satellites went into operation within a month, the remaining four at the beginning of 2011.

From May 2011, the remaining 18 new satellites will be launched into space in three successive launches in a 3-month cycle. On July 13th and December 26th, 2011, two days after the scheduled launch, a Soyuz-2.1a launcher each put six Globalstar-2 satellites into orbit.

With the exception of six satellites, which were launched in mid-2012 and are used to fill additional gaps and reserves, the replacement of the satellites has been completed. The last, not yet active, new satellites should also be positioned and activated by mid-May 2012.

The exchange is completed and the network is functional again.

Web links

Individual evidence

↑ https://eu.globalstar.com/en/index.php?cid=5550 Secondary Phone Number Service

^ ITU Operational Bulletin. (PDF; 600 KB) In: www.itu.int. May 18, 2012, accessed May 10, 2015 .

↑ https://www.globalstar.com/en/ir/docs/GlobalstarOverviewPresentation.pdf Globalstar - Globalstar Overview 2017 - set of slides (English)

↑ https://gsproductsupport.files.wordpress.com/2009/04/description-of-the-globalstar-system-gs-tr-94-0001-rev-e-2000-12-07.pdf Globalstar - Description of the Globalstar System (GS-TR-94-0001)

↑ http://spectrum.welter.fr/international/cept/ecc-reports/ecc-report-171-unwanted-emissions-iridium-ras-1610-1613-MHz.pdf IMPACT OF UNWANTED EMISSIONS OF IRIDIUM SATELLITES ON RADIOASTRONOMY OPERATIONS IN THE BAND 1610.6-1613.8 MHz

^ Degradation Of Satellites Puts Globalstar's Service, Business Plan At Risk

↑ GLOBALSTAR, INC. FILES FORM 8-K WITH SEC

↑ Constellation Update and Advisory ( Memento of the original from October 6, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2
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↑ Satellite Telephone Quality of Service Comparison Iridium vs. Globalstar July 2002 ( Memento of the original from September 28, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 146 kB) @1@ 2