Online Spotlight: The Globalstar Big LEO Satellite System for Near-Global Satellite Communications
At the end of the last century, satellite operators from the U.S.A. and Europe began to develop mobile satellite communication (MSC) systems for voice, data and tracking solutions. Ground cellular communications were already at an early stage of their development, but were not able to fully cover all areas on Earth. With the development of MSC all remaining regions in the world will be covered with great importance for science, mobile industry, telecommunications and defense.
MSC HISTORICAL BACKGROUND
Big low-Earth-orbit (LEO) systems are large low-earth-orbit satellites that provide comprehensive communications services in addition to real-time voice. They are used to provide global mobile telephone services via small personal handsets.
In September 1991, Inmarsat announced its strategy for the future development of Project-21 using an intermediate circular orbit (ICO). The culmination of this project was the introduction of a handheld phone prototype to the whole world under the name of the Inmarsat-P service. The Inmarsat-P phone was envisaged as a dual-mode terminal to work with a cellular system, from a satellite when out of home region cellular coverage, in a region with a different cellular standard or in a region without roaming arrangements. To implement this service, a new space segment architecture would be required, such as the proposed medium Earth orbit (MEO).
U.S. satellite operators Globalstar, Iridium, Ellipso, Odyssey, Aries and AMSC proposed the exploitation of the big LEO satellite constellation, so that on January 31, 1995, the Federal Communications Commission (FCC) granted licenses in the U.S. to Globalstar, Iridium and Odyssey.
TRW proposed to exploit the MEO satellite solution using a satellite configuration called Odyssey. The Odyssey constellation was to comprise 12 satellites, equally divided into three orbital planes, inclined at 55 degrees to the Equator. The satellites were to be placed 10,600 km above the Earth. The FCC granted TRW a license to set up its satellite MEO system in 1995, noting that construction of the first two spacecraft should begin by November 1997. The Odyssey was scheduled to begin operations in 1999 at an estimated cost of $3.2 billion. Unable to find another major investor willing to support the project, Odysseus was abandoned in December 1997.
The investment of $ 1.2 billion in ICO by Teledesic was announced in November 1999, but the system was abandoned after many problems. Meanwhile, Iridium and Globalstar received bankruptcy protection in the U.S.A. after difficulties with the establishment of space segments and problems with market penetration. Finally, both systems received sufficient funding to proceed to the next stages of development for the upgrade of terrestrial networks and personal satellite communications.
Loral Space and Communications, with Qualcomm, developed the Globalstar system concept at a similar time as Iridium. Globalstar received an operating license from the FCC in November 1996. The first launch of four Globalstar satellites occurred in May 1998 with a Delta rocket from Cape Canaveral. The deployment of 48 satellites plus four spares was finally accomplished, using Delta and Soyuz-Ikar rockets.
The first six second generation Globalstar satellites were launched on 19 October 2010, and additional six were launched in July 2011 followed by another six satellites in December 2011; so, the launch of 24 satellites of the second generation constellation was completed on 6 February 2013. In February 2022, it was announced that Globalstar purchased 17 new satellites to continue its constellation built by MDA Ltd. and Rocket Lab for $327 million. The satellites are expected to be launched by 2025.
The Globalstar satellite constellation supports the company's current line of products and services for voice, duplex and simplex data, including its SPOT branded consumer products that have launched over 2200 rescues in over 70 countries and at sea since its initial launch in 2007. Globalstar is known for its crystal clear voice service “landline quality,” ease of use and value for customers.
The Globalstar system (see Figure 1) uses code division multiple access (CDMA) and frequency division multiple access with an efficient power control technique, multiple beam active phased array antennas for multiple access, frequency reuse, variable rate voice encoding, multiple path diversity and soft-handoff beams to provide high-quality satellite service.1-4
Handheld and semi-fixed satellite phones are communications tools available to businesses, professionals and military troops in mobile and fixed environments for satellite telephone access via the Globalstar big LEO MSC system at sea, on land and in the air. Compared to little LEO systems (comprising small satellites measuring around one meter cubed, to provide mobile data and messaging services), big LEO systems are bigger have more power and bandwidth and offering comprehensive services to their subscribers. The bigger size of these satellites enables more complex data processing in the transponders than the simple store-and-forward feature of the little LEO systems. These systems provide a wide variety of services, such as voice, data and fax, SMS and paging, Search and rescue (SAR), environmental monitoring and position, velocity and time data and determination.
Globalstar is a LEO satellite-based digital telecommunications system that offers wireless telephone, messaging, tracking and other telecommunications services worldwide, starting from the end of the last century. The communications system is designed to provide worldwide digitally crisp voice, data and facsimile services to portable, mobile and fixed user terminals (UTs). To the user, operation of a Globalstar phone is like that of a cellular phone but with one main advantage: while a cellular phone works only with its compatible system within its coverage areas, the Globalstar system offers worldwide coverage and interoperability with current and future publicly switched telephone and land mobile networks.
The Globalstar system comprises three major segments: Space, Ground and User, including a terrestrial telecommunication network, as shown in Figure 1. The Globalstar satellites receive signals from mobile devices in S-Band (forward link) and send signals to mobile devices in L-Band (return link). Links between satellites and ground earth stations (GESs) are in C-Band and the system is controlled by Operations Control Centers (OCCs). GES terminals are connected via satellite links with different users, such as personal earth stations, personal trackers, vehicle earth stations, ship earth stations, aeronautical earth stations and global vehicle trackers.
The Globalstar system does not have an inter-satellite connection like the Iridium network, so it cannot cover both pole regions. Thus, it provides near-global coverage to users anywhere in the world between the two poles, even when affected by propagation interference and non-ideal environmental conditions. Globalstar CDMA is a modified version of Interim Standard 95 (IS-95), originally developed by Qualcomm.
The Globalstar satellite comprises communication systems in S and L-Band, a trapezoidal body and two solar arrays. Each satellite operates at an altitude of 1414 km (approximately 876 mi). On any given call, several satellites transmit a caller's signal via CDMA technology to a satellite dish at the appropriate gateway where the call is then routed locally through the terrestrial telecommunications system. Globalstar phones look and act like mobile or fixed phones. Like "bent-pipes," or mirrors in the sky, the Globalstar constellation of LEO satellites picks up signals from over 80 percent of the Earth’s surface, everywhere outside the extreme polar regions and some mid-ocean regions. Several satellites can pick up a call; this “path diversity” helps assure that the call is not dropped even if a phone moves out of sight of one of the satellites.
The system's software resides on the ground, not on the satellites, which means fast and easier system maintenance and upgrades. The Satellite OCC manages the Globalstar satellite constellation. As soon as a second satellite picks up the signal and can contact the same terrestrial gateway, it begins to simultaneously transmit. If buildings or terrain blocks a phone signal, the “soft-handoff” prevents call interruption. The second satellite now maintains transmission of the original signal to the terrestrial GES or gateway. Additional advantages of using LEO satellites within the Globalstar system include no perceptible voice delay (latency) and lighter/smaller all-in-one phones.
Gateways process calls, then distribute them to existing fixed and cellular local telephone networks or the Internet. Terrestrial gateways are an important part of Globalstar's strategy to keep key technology and equipment easily accessible and to integrate its services as closely as possible with existing local telephone networks. This helps make the Globalstar system and its service easier to manage, expand and improve coverage.
Actual Globalstar coverage may vary because of gateway deployment, local licensing and other factors. Globalstar service is a satellite radio technology subject to transmission limitations caused by the type of terrain, service area limits, customer equipment use and other variable conditions including the functionality and orbital locations of the satellites themselves.
To provide full voice and duplex data coverage, Globalstar expanded its terrestrial network in 2012 with an additional 6 GESs for the Pacific, 3 GESs for the Atlantic and 5 GESs for the Indian Ocean region. Today, the total number of GES terminals is 24, however, for polar coverage, Globalstar must establish GES terminals in each polar region.4-7
The Globalstar satellite transponder is transparent; unlike the Iridium system, without cross or intersatellite-links and onboard traffic processing, all traffic switching service happens on the ground and traffic routing is through the existing fixed public switched telephone network (PSTN) and associated networks. A satellite phased array antenna produces 16 elliptical spot beams that enable continuous multiple satellite global coverage, path diversity and position location. Lowering the angle to the satellite will increase the overlapping coverage. Thus, small changes can dramatically increase the coverage area, which is particularly apparent in the polar regions. If operated at low elevation angles, polar areas that otherwise could not be covered can receive service.
The Globalstar space segment has a constellation of 48 satellites in eight planes with six satellites per plane inclined at 52 degrees to the Equator at an altitude of 1414 km LEO. Four in-orbit spares are parked at a lower altitude. The low orbits permit low-power user phones, like cellular. The constellation is a 48/8/1 Walker Delta pattern with a 52 degree inclination, designed to provide global Earth coverage between 70 degrees N and S latitudes, see Figure 2.
Globalstar provides coverage from any point on the Earth’s surface to any other point worldwide with multiple overlapping satellite beams for simplex and voice/duplex data, exclusive of both polar regions. The simplex data coverage map in Figure 2 shows the coverage with the current 24 GES terminals indicated as ground satellite antenna units.
This service is for satellite asset tracking (SAT) and SAT and fleet management (SATFM) of all mobile assets including aircraft, known as global aircraft tracking (GAT). Globalstar also provides fixed data service for fixed assets known as satellite supervisory control and data acquisition (SCADA) of machine-to-machine communications (M2M). These units are designed to transmit just a single packet message 3-times (the original transmission plus 2-repeats) per day in the frequency appropriate for the given regions in the coverage area.
The coverage area may vary based on terminal location, terrain features, signal strength and other factors affecting satellite communications. The Globalstar simplex data service is provided via units containing GPS Rx and Satellite Tx only. Thus, to provide complete coverage for simplex data, like the Inmarsat coverage map, Globalstar must provide an additional 4 GES terminals for the Pacific area, 2 GES terminals for the Atlantic area and 3 GES terminals for cities in the Indian Ocean Region.
The voice and duplex data coverage map (see Figure 3) is available for satellite personal, mobile and fixed voice (Tel) and duplex data transmission and data service for SATFM of all mobile assets including aircraft. The map indicates coverage for voice and dial-up data calls only. Direct Internet calls (Dialing #777 send) can be made from all regions except China and the Central American countries of Belize, Panama, Guatemala, Honduras, Nicaragua, El Salvador and Costa Rica, along with their surrounding coastal waters.
In both polar areas, the need for overlapping coverage is increased and power demands may be increased because the look angle to the satellite is limited. High gain directional antennas become practical for fixed and even portable installations. The payback is that Globalstar can serve areas that otherwise might be unserviceable. The same considerations for polar areas apply to equatorial areas, where the overlapping coverage is less than 100 percent.
The Globalstar communication satellite is a simple, low-cost satellite designed to minimize both satellite and launch costs. The first-generation satellite, spacecraft orbital planes and second-generation of Globalstar satellite are illustrated in Figure 4.3-6
The ground segment comprises a network of gateways (GESs), satellite control centers (SCCs), OCCs and Globalstar business offices (GBOs) interconnected via a Globalstar data network (see Figure 5). GESs, provide the interfaces between the satellites and the PSTN/public land mobile network to provide telemetry, tracking and command and control links between the SCC and the satellites and to allocate satellite resources on a call-by-call basis.
The Globalstar system has many GESs distributed around the world that receive and transmit feeder link signals from and to the satellites and provide interconnection to the PSTN. GESs are designed for unmanned operation. Each has up to four 5.50 meter antennas and electronic equipment installed in a building or shelter. The GES connects the Globalstar space segment to terrestrial switching equipment, receives telephone calls from the terrestrial switching equipment and generates CDMA carriers to transmit through the satellite. The satellite then retransmits the signal to UTs.
The UT equipment may be either handheld, fixed or mobile and located anywhere within the satellite antenna footprint. In the return direction, the UT transmits to the satellite(s) and the satellite(s) retransmit the signal to the GES. The GES connects the call to terrestrial switching equipment, which can then connect to any subscriber using the standard telephone system. Connections can also be made to terrestrial cellular subscribers or to other Globalstar UT mobile or fixed stations.
The Globalstar system includes two OCCs to manage and control system planning and execution. Each is completely capable of operating the network and managing the satellite constellation. There are two to circumvent the possibility of earthquake, power grid failure or other disasters. One is in San Jose, California and the other is near Sacramento. Each location includes an OCC, SCC and GBO.
The OCC manages the satellites, controls the orbits and provides telemetry and command (T&C) for the satellite constellation. To accomplish this function on a worldwide basis, the OCC communicates with T&C units collocated at selected GESs. The T&C units share the RF links with the GES communications equipment to relay commands and to receive telemetry.
The SCC manages all satellite telemetry, track, command and control functions and launches operations.
To support the GBO, the Globalstar accounting and billing system (GABS) is collocated with the SCC and the OCC. The GABS is responsible for all financial activities associated with Globalstar. 2, 4-6
The user segment includes three different kinds of UT equipment: handheld units, mobile-mounted units and fixed units. UTs with omni-type antennas are designed to support data rates up to 9.6 Kb/s. A variable rate vocoder varies its rate each frame to voice activity. This automatically reduces transmitter power for lower vocoder rates, which means, on average, less interference to other users and higher system capacity.
Satellite diversity is used in the system; if a call is transmitted through multiple satellites, the user terminal and the gateway receive at least two and usually more signals and coherently combine them, which brings diversity gain, reduces the required link margin on each individual link and increases capacity.
Diversity overcomes the adverse effects of propagation such as blocking, shadowing and fading. With the constellation, double satellite coverage is available nearly 100 percent of the time; therefore, UT devices can provide diversity as required. Both forward and reverse link power control is used to adjust GES and UT powers to the minimum required to maintain high performance. Power is increased only as needed, which means less interference to other users and increased capacity.
Handheld Satellite Phone Terminals
The Globalstar handheld terminals look like standard cellular telephones. They can also be used as equipment for alert after emergency grounding of ships and aircraft. Tri-, dual- or Globalstar-only modes of telephone service are available:
1. Tri-mode satellite phone service offers a global phone roaming solution for the U.S.A.-based Advanced Mobile Phone System (AMPS/IS-95), IS-95 CDMA digital phone coverage or the Globalstar satellite service. The tri-mode Qualcomm satellite phone for AMPS/CDMA/Globalstar services is shown in Figure 6a. Calls can be answered with any key for easy access to short messages and voicemail, with a "new message" alert that can be configured by the user. It features standard international dialing (prefix "+"), a mailbox for voice, numeric and text messages, user-configured ringtones (8 modes), side keys for volume adjustment and a 2.5 mm headphone jack.
2. Dual-mode satellite phone service offers global service for the Global System for Mobile Communications (GSM) Cellular Class 4 phones for Globalstar/GSM users, such as the Ericsson and Telit dual-mode GSM/Globalstar phones.
3. The Globalstar phone service mode only satellite phone is one of the smallest and lightest SatPhones with dimensions 16.92 cm (H) x 7.33 cm (W) x 5.79 cm (D). A Qualcomm GSP-1700 satellite phone is shown in Figure 6b.
Fixed Satellite Phone Terminals
The Globalstar network, in general, offers two types of fixed satellite terminals:
1. Payphone Terminals are single line Globalstar fixed units used to connect a payphone service into the PSTN for rural and remote areas used in the U.S.A. out of terrestrial landline or cellular coverage (see Figure 7a). These units can also be installed on mobile platforms, namely onboard aircraft for passenger service with flush mount fuselage antennas. Access to the Globalstar network is via an antenna mounted outside the booth with a clear view of the sky or via a mobile satellite antenna. The antenna is connected to the CDMA radio unit.
2. Fixed Single Line Phones offer communication service in remote office environments. An indoor telephone kit and outdoor antenna are shown in Figure 7b. The antenna can be mounted in a convenient position on the roof, wall or mast with a clear view of the sky and connected to the subscriber’s equipment. The system is compatible with all RJ11 type subscriber equipment such as wall, desk and cordless phones and value-added devices like fax/answering machines. Globalstar also offers a standard trunk interface for compatibility with local switching systems, such as private automatic branch exchanges (PABX).
Fixed satellite phone equipment performance is equivalent to that of a mobile earth station (MES) except that the antenna gain and transmitter power may be even higher. In fact, fixed terminals do not require path diversity to combat fading and blockage and must support seamless beam-to-beam and satellite-to-satellite hand off.
Since there is no hand off between the local cellular system and the Globalstar network, if the user crosses a service boundary between the local cellular system and Globalstar, the call could be dropped and must be placed again. Indicators tell the operator that the mode has changed. The system will not clash in a boundary area, thus all users/MESs can select the preferred mode. The call can be placed in Globalstar mode and will continue until the phone is in an idle state.
The Globalstar system, in general, offers voice, duplex data speeds from 9.6 to 200 Kb/s, circuit switched data similar to dial-up Internet services, packet switched data, Internet, SCADA and integration with GPS for satellite navigation.
3. Multipurpose 9600 Data Satellite Hotspot is the de facto satellite mini router that provides hotspots for users to use a convenient app and seamlessly pair their existing GSP-1700 satellite phone with a smartphone, tablet or laptop to send and receive E-mail and text messages over the Globalstar network (see Figure 8).
With the Globalstar 9600 and Globalstar satellite phones, customers can use their existing Wi-Fi-enabled devices to send e-mails and post on social media over the Globalstar network. Whether on land or at sea, customers can maintain reliable connectivity when beyond the cellular network. The Globalstar 9600 router is compatible with cell phones such as Android, Apple iOS, Windows and Mac. Thus, today’s smartphones provide more options for staying in touch with friends and family.
Customers can take smart phones beyond cellular using the Globalstar satellite hotspot outdoors with a clear view of the sky and horizon without obstructions, buildings and large trees. The phone must be placed on its side and the antenna fully extended, pointing toward the sky and turned on. After 30 seconds, two icons appear on the home screen, which means that unit is registered with the Globalstar satellite network. Globalstar 9600 is then ready to send and receive E-mail and data. This unit is ideal for industries such as: energy, oil and gas, emergency and commercial management, ferries and recreational marine, aircraft, transportation and construction.2,9-11
Mobile Satellite Phone Terminals
1. The Maritime Satellite Phone and Data Package is a satellite Wi-Fi hotspot (SatFi) device that allows customers to use their existing Wi-Fi-enabled devices to make and receive calls, send E-mail and send SMS text messages over the newest Globalstar satellite network. Whether at sea or on land or in the air, up to eight Globalstar SatFi users can maintain reliable connectivity when beyond cellular with one SatFi device providing voice quality and fast data speeds. The modem is VoIP, allowing users to send and receive satellite calls through a smartphone on both cellular and Globalstar communication networks.
Once users are registered and connected to the SatFi, they are immediately able to make outbound calls. Additional users, passengers and guests are able to register their smartphones on SatFi and make calls or data connections through the SatFi app, which must be downloaded on a customer Android or iOS device to connect to the Globalstar network.
In Figure 9a is a new generation of the Globalstar SatFi maritime terminal, which contains: Globalstar SatFi unit, Globalstar SatFi power supplies (20-240VAC/12VDC), a Globalstar marine helix antenna (GAT-17MR) and a Wi-Fi antenna for connecting to existing Wi-Fi-enabled devices. Users can easily connect Wi-Fi-enabled devices to the SatFi device with the custom SatFi and SatFi Voice apps available for Android, Apple iOS, Mac and Windows. Using smartphones, the SatFi device can make voice calls, send E-mails and SMS, post information to social media and transfer incoming calls and send text messages between connected users. In addition, it can provide SOS alerts with GPS location data sent to emergency responders.
2. The Vehicular SatFi Satellite Phone and Data Package is the same as for maritime applications, however, it is designed for the vehicle-based application as well (see Figure 9b). Vehicle-based examples include cars, trucks, buses, recreational vehicles, all-terrain vehicles, locomotives (rails) as well as transportable boats. In addition, this device can be used for fixed location solutions, which may include remote and rural areas where there is no cellular coverage and satellite communication is desired or needed. The SatFi vehicular terminal can use a special antenna for land mobile applications known as the magnetic patch antenna (GAT-17MP).
3. The Aviation SatFi Satellite Phone and Data Package is a dual voltage aviation voice and data package with reliable satellite technology for providing affordable voice and data services in the cockpit, including to passengers. Like maritime and vehicular solutions, the aviation SatFi solution allows up to eight smart devices to connect to the Globalstar satellite network through Wi-Fi.
As shown in Figure 10a, an aviation SatFi terminal containing a supplemental type certificate (STC) antenna for Part 23 Non-Pressurized Aircraft connects directly to a Globalstar STC phone cradle or a SatFi wireless hotspot, including a SPOT TRACE global tracking device unit connected via smartphone or tablet. Using this equipment, pilots and passengers can make and receive clear voice calls, send and receive e-mail messages, transfer data files, post on social media, track the aircraft’s position, use specialty apps and even check the latest weather reports with speeds that are up to 4x faster than existing alternatives. In fact, it gives the aircraft in flight reliable voice and data communications that are completely independent of cellular and radio coverage.
4. The Building SatFi Satellite Phone and Data Package is designed for building or fixed applications. It contains a fixed roof or mast mounted helix antenna (GAT-17HX) and the same SatFi modem previously described (see Figure 10b). The SatFi modem is connected to smartphones or tablets via a Wi-Fi antenna.2,4,11,12
Mobile and Personal Satellite Trackers
1. The Simplex SmartOne C Tracker is a GPS Rx/Globalstar Tx unit designed for intelligent tracking and management of powered and non-powered fixed and movable assets, such as intermediate bulk containers, vehicles and boats and it is a practical solution to improve operating efficiency and security (see Figure 11a). The design allows it to be easily installed and field managed without the need for harnesses, antennas and external power. With an independent power supply, it can work and send position data even if an aircraft is grounded in an emergency with no power sources. The SmartOne is powered by 4 AA 1.5 V lithium batteries providing three+ years of battery life and eliminates the need to purchase expensive proprietary batteries for replacement.
It uses motion sensors, comparative GPS positioning and custom configured sensors to gather and transmit asset status information. Each unit is custom configured to track its asset’s specific needs and provide intermediate and emergency alerts by e-mail and/or text/cellular. SmartOne C is a satellite-managed asset-ready tracker designed for the intelligent management of fixed and mobile assets.
It includes up to 12 different reporting times, interval or 24-hour operational modes and alternate reporting schedules. The device can be line-powered, or in the absence or interruption of external power, it will automatically switch to battery backup. When using line-power, the user has maximum flexibility in messaging frequency allowing for regular monitoring of asset location.
2. The SPOT X 2-Way Satellite Messenger is handheld personal locator that provides transmission and reception of satellite messages so users can be connected when outside of cellular range, including direct communication with SAR services in case of life-threatening emergencies, (see Figure 11b).
It provides users with their own cellular numbers, so others can message the user directly from their cell phones or other SMS devices at any time. It requires an active service subscription. It can be easily connected to the SPOT X app and provides satellite connectivity transforming a phone into a satellite messenger providing the following features:
- It can exchange messages with any cell phone number or E-mail address from virtually anywhere in the world. This requires a clear view of the sky with no obstructions. A user’s SPOT account comes loaded with 14 predefined messages that can be customized and synchronized to a SPOT X device
- It can send an SOS to a 24/7 search & rescue center, message back and forth about the nature of the emergency and receive confirmation when help is on the way
- It can select from 2½, 5, 10, 30 or 60 minute tracking intervals, and let interested parties know that a user is OK and follow the user’s progress with SPOT’s Google Maps™ interface
- It can be easily connected to the SPOT X application via Bluetooth and provides a satellite connection at a user’s fingertips.4,13-15
3. The SPOT Satellite Personal Tracker (SPOT 1) was introduced to the market by Axonn in early 2008 (see Figure 12a). With the SPOT Tracker, people in emergencies and their families have peace of mind knowing help is always within reach. It is the only device of its kind that uses the GPS receiver to acquire its coordinates and send its location with a link to Google maps, including a pre-programmed message via a commercial satellite network. This unit does more than just call for help and check emergency progress. Non-emergency assistance is also available at the push of a button. SPOT 1 features four key functions:
- ALERT 9-1-1 MODE dispatches emergency responders to the exact location. SPOT sends one message every 5 minutes until power is depleted or 911 is cancelled
- ASK FOR HELP is a request for help from friends and family with an exact emergency location. SPOT sends one message every 5 minutes for one hour or until help is cancelled
- CHECK-IN lets contacts know where an emergency is and that survivors are OK. SPOT sends three identical messages to the SPOT service for redundancy. The first of those three messages is delivered
- TRACK PROGRESS sends and saves the emergency location and allows contacts to track progress using Google maps. SPOT sends one message every 10 minutes for 24 hours or until SPOT is powered off.
4. The SPOT Satellite Emergency Messenger (SPOT 2) – The SPOT Satellite Messenger or SPOT 2 is a Satellite Emergency Notification Device. It was introduced in October 2009 as an improvement to SPOT 1 (see Figure 12b). It is designed to be carried into remote locations where the user may require emergency assistance. It has five working modes (see Figure 12b):
•HELP/SPOT ASSIST requests help every 5 minutes for 1 hour from friends/family of a distressed person at any emergency GPS location or asks for help from assistance groups.
•CHECK-IN/OK transmits a message to let predefined contact(s) know where the distress location is and that persons are okay. It attempts to send three messages to help ensure successful transmission.
•CUSTOM MESSAGE creates custom non-urgent pre-programmed message and sends it to friends and family with the GPS location.
•RACK PROGRESS acquires the GPS location of a distressed person every 10 minutes for 24 hours and sends each location one time, allowing all helping contacts to track the distressed person’s progress using Google maps.
•SOS sends emergency assistance the location of a distressed person to the local GEOS IERCC every 5 minutes until batteries die or until the distress is cancelled.4, 16-18
Satellite backhaul via the LEO satellite constellation is being used extensively today supporting cellular operators’ efforts to extend their network coverage in fixed and mobile environments. Urban and semi-urban areas enjoy congestion relief and seamless connectivity by using satellite backhaul, but rural coverage worldwide remains poor with the necessity for a more reliable satellite backbone.
The Globalstar satellite system is primarily designed for phone, data and tracking at sea, on land for roads and railways and in the air. Its basic modulation scheme is CDMA spread spectrum using diversity for signal quality, as well as power control via complex antennas for L-Band (1.6 GHz) and S-Band (2.5) GHz) communication with personal handheld, fixed and mobile equipment onboard ships, land vehicles and aircraft.
Given the technological and business options available and recent innovations in geostationary Earth orbit (GEO) satellites and non-GEO (LEO) high throughput satellite constellations, there is good reason for cellular operators to use Globalstar satellite services for backhaul. In addition to the socio-economic impact, greater use of cellular backhaul via the Globalstar LEO satellite constellation significantly increases the subscriber base and promotes greater reach in rural, remote and mobile environments.
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