Overview
Globalstar is a consortium of leading international telecommunications companies originally established in 1991 to deliver satellite telephony services through a network of exclusive service providers.

The Globalstar system is designed to provide high quality satellite-based telephony services to a broad range of users:

The Globalstar system offers a multitude of services:

Globalstar's constellation of 48 Low Earth Orbiting (LEO) satellites transmits calls from your Globalstar wireless phone or fixed phone station to a terrestrial gateway, where they are passed on to existing fixed and cellular telephone networks in more than 100 countries on 6 continents.

As a wholesaler, Globalstar sells access to its system to regional and local telecom service providers around the world. These Globalstar partners in turn, form alliances with additional providers. This lets Globalstar leverage the marketing, operating and technical capabilities of the world's premier communications service providers.

By extending their reach, Globalstar complements terrestrial networks, rather than competing with them, opening up markets and bringing telephony to entirely new areas of the world.

Ultimately, the caller benefits because his final service provider understands the local market and provides optimal service for the area.

* Depending on the Globalstar Service Provider, service availability planned for rollout in late 2000, early 2001.

 

Gateways
QUALCOMM - designed Globalstar Gateways are an integral part of the Globalstar ground segment, which also includes Ground Operations Control Centers (GOCCs), Satellite Operations Control Centers (SOCCs), and the Globalstar Data Network

Each Gateway, which is owned and managed by the service provider for the country in which the Gateway is located, receives transmissions from orbiting satellites, processes calls, and switches them to the appropriate ground network.

A Gateway may service more than one country. Gateways consist of three or four dish antennas, a switching station and remote operating controls. Because all of the switches and complex hardware are located on the ground, it is easier for Globalstar to maintain and upgrade its system, than it is for systems which handle switching in orbit.

Gateways offer seamless integration with local and regional telephony and wireless networks. The Gateway connects the Globalstar satellite-based wireless network with the Public Land Mobile Network (PLMN), such as AMPS and GSM. It also connects directly into the local Public Switching Telephone Network (PSTN). As such, the Gateway is the termination point for network transmission and network signaling.

The Gateway is connected to the existing PSTN using standard E1/T1 trunk supporting a variety of signaling protocols. Inter-operability between the Globalstar system and telephone/cellular companies enables the subscriber to maintain a convenient single point for billing. Encoding ensures voice and signaling security for individual transmissions.

The Gateway is a sophisticated piece of engineering, designed by QUALCOMM to make the Globalstar Communications System capable of offering seamless services for all Globalstar customers.

Other components of the Globalstar Communications System include:

Satellite Constellation
The Globalstar constellation consists of 48 LEO (low - Earth - orbiting) satellites, plus an additional four satellites in orbit as spares. Each consists of an antenna, a trapezoidal body, two solar arrays and a magnetometer, and operates at an altitude of 1414km (876 miles).

The satellites are placed in eight orbital planes of six satellites each, inclined at 52 degrees to provide service on Earth from 70 degrees North latitude to 70 degrees South. Because of this configuration, the polar regions, including most of Greenland, small parts of Alaska, Canada, Scandinavia, Siberia, and regions in the Southern Hemisphere, including Antarctica and parts of South America are not covered.

"Bent-Pipe" Technology
Like "bent-pipes", or mirrors in the sky, the Globalstar constellation of satellites can pick up signals from over 80% of the Earth's surface. Several satellites pick up a call, and this "path diversity" assures that the call does not get dropped even if a phone moves out of sight of one of the satellites. If buildings or terrain block your phone signal, a "soft-handover" takes place, and the call's transmission is switched to an alternate satellite with no interruption. This satellite now maintains transmission of the original signal to one of several terrestrial Globalstar Gateways. Because all the switches and complex hardware are located on the ground in the Gateways, Globalstar satellites are relatively simplistic, leading to dramatically increased system reliability.

Additional advantages of using low-Earth-orbiting satellites within the Globalstar Communications System include lighter, smaller, all-in-one handsets and no perceptible voice delay. LEO satellites also minimize call transmission time delays. Long transmission delays cause noticeable gaps between the time a caller speaks and when the listener hears what is being said.

Satellite Footprint
The satellite coverage beams for satellite phone communication links and the Gateway communication links are quite large. The picture to the right gives you a sense of scale for the coverage of a typical thirty-six hundred mile diameter beam footprint.

Each footprint moves rapidly across the Earth's surface. A satellite that passes directly overhead is visible to that spot for only about 15 minutes.

When a user places a Globalstar satellite call, the nearest satellite picks up the signal. Globalstar satellite phones can operate with a single satellite in view, though typically two to four satellites will be overhead. This simultaneous coverage by multiple satellites is called "path diversity," which enhances the quality of the Globalstar satellite call.

Path Diversity
Path diversity is a method of signal reception that combines multiple signals of varying power strengths into a single coherent signal. Satellite phones communicate with as many as three satellites simultaneously, combining those signals into a single, static-free signal. Globalstar satellite phones also alter power levels to compensate for shadowing and interference as needed.

As satellites move in and out of view, they will be seamlessly added to and removed from the calls in progress, reducing call interruption. This enables the Globalstar system to provide superior service to a wide variety of locations with less potential for signal blockage from buildings, terrain, or other natural features.