Teledesic LLC

Wengen Wireless LLC

David Palmer Patterson

Mark Alan Sturza

James R Stuart

Moshe L Liron

Douglas Gene Lockie

Edward F Tuck

Alison K Brown

Vilnis G Grencions

Farzad Ghazvinian

Asu Ram Jha

Donald A Ashford

Sami Hinedi

H Beat Wackernagel, Deceased

Len Quadracci

A scalable satellite data communication system that provides incremental global broadband services using Earth-fixed cells may begin with a limited satellite deployment that initially serves a limited number of Earth-fixed cells. The system has the flexibility to incrementally increase the number of Earth-fixed cells that are served, with minimal constraints on the relative locations of the cells on the Earth, by adding satellites of potentially greater complexity to the system. Backward compatibility with existing user terminals is achieved by maintaining the same satellite communication interface as with the already-deployed satellite constellation. Continuous and/or non-continuous service may be provided to selected Earth-fixed cells. Scheduled non-continuous service is particularly advantageous for bulk data transport services. Satellites may use simple mechanically-steered antennas. Communication links may be handed from one satellite to another when one satellite moves out of range and is no longer able to cover a selected Earth-fixed cell.

Scalable satellite data communication system that provides incremental global broadband service using earth-fixed cells

The Satellite Communication System disclosed in the specification is a dynamic constellation (C) of satellites (S). The present invention is capable of offering continuous voice, data and video service to customers across the globe on the land, on the sea, or in the air. The preferred embodiment of the invention comprises a low Earth orbit satellite system that includes 40 spacecraft (S) traveling in each of 21 orbital planes at an altitude of 700 km (435 miles). This relatively large number of satellites employed by the preferred embodiment was selected to provide continuous coverage of the Earth's surface at a high minimum mask angle (1230a) of forty degrees. Each of the individual 840 spacecraft (S) functions as an independent sovereign switch of equal rank which knows the position of its neighbors, and independently handles traffic without ground control. The satellites (S) are capable of transporting calls to millions of customers using portable (P), mobile (M) and fixed (F) residential and business terminals, and gateways (G) to public phone networks. The constellation uses the 20 and 30 GHz frequency bands for communications between Earth and the constellation (C), and the 60 GHz band for communicating among the satellites (S). The present invention is designed to support in excess of 2,000,000 simultaneous connections, representing over 20,000,000 users at typical business usage levels, and over 350 billion minutes of use per year. Only a system such as the preferred embodiment, which utilizes 840 satellites at a preferred minimum mask angle of forty degrees, can accomplish these challenging objectives.

Satellite communication system

The present invention overcomes the limitations encountered by conventional packet switching using virtual circuits. The present invention utilizes a 'datagram' approach that routes every packet (22) conveyed by the system independently at every node in the network. The packets (22) are directed along an optimized pathway through the network by a fast packet switch (38) that directs traffic based on instructions from an adaptive routing processor (12A) that continuously runs an adaptive routing software (12B). This adaptive routing processor (14) supplies an output (12C) to a routing cache memory (20) which stores fast packet switch routing port output tags (30). An input packet processor (28) extracts a supercell address from the header (24) of each packet (22) and uses the supercell address (21A) as an index to retrieve a fast packet switch output port tag (30) stored in the routing cache memory (20). This tag (30) is prepended to the packet (22), and sent to an input port (36) of the fast packet switch (38), which includes a number of multi-stage self-routing switch modules (132) and a number of asynchronous packet multiplexors (134). The modules (132) and multiplexors (134) route the tagged packet (34) to an output port (40) which is connected either to a scanning beam antenna (SBA) or an intersatellite link antenna (ISA).

Non-blocking dynamic fast packet switch for satellite communication

A communication system and methods for sharing a common communication frequency, without interfering with a second communication system which has a plurality of satellites operating in geostationary orbits (GO) and ground stations (GS) which communicate with the satellites (GEO) on the common communication frequency, is disclosed. Conventional geostationary satellites broadcast in C and K.sub.u bands. Ground stations (GS) which receive these signals must have their antennas pointed toward the plane of the Equator (EQ). Satellites (10) which occupy inclined orbits (LO) and communicate with terrestrial terminals (12) propagate beams of energy that do not intersect the plane of the Earth's Equator. Terrestrial terminals (12) in the northern hemisphere communicate with a satellite (10) only when the sub-satellite point of the satellite (10) is at a latitude more northerly than the terrestrial terminal (12). Terrestrial terminals (12) in the southern hemisphere communicate with a satellite (10) only when the sub-satellite point of the satellite (10) is at a latitude more southerly than the terrestrial terminal (12). The spatial isolation of signals achieved by this novel pointing method insures that both the geostationary and inclined orbit satellite systems do not interfere with each other.

Frequency sharing for satellite communication system

Earth-fixed cell beam management methods which may be employed to allocate beams generated by a constellation of low Earth orbit satellites (12) flying in orbits below geosynchronous altitudes are disclosed. These beams (19) are electronically steered so that they illuminate 'Earth-fixed cells' (26) as opposed to 'satellite-fixed cells.' Beam steering apparatus using a spherical dielectric lens (106) is disclosed. In a system that employs satellite-fixed cells, the 'footprint' of the beams propagated by a spacecraft defines the zone on the ground called a 'cell' which is illuminated by the spacecraft. This satellite-fixed cell moves constantly as the spacecraft moves around the globe. In sharp contrast, an 'Earth-fixed cell' (26) is a stationary region mapped onto the surface of the Earth (E) that has permanent fixed boundaries, just like a city or a state. Although the rapidly moving satellites (12) still shine their beams over the ground in rapidly moving footprints (16), the locations of the footprints at any given time do not determine the location of the unchanging Earth-fixed cells (26). The great advantage provided by using cells having boundaries that are fixed to an Earth-fixed grid (20) is realized when a subscriber being served by one satellite must switch to another beam in the same satellite or to a second satellite because the first is moving out of range below the local horizon. With satellite-fixed cells, this 'hand-off' involves the assignment to the terminal of a new communication channel within the new beam or new satellite. This assignment process takes time and consumes processing capacity at both the terminal and the satellite. It is also subject to blocking, call interruption, and call dropping if there is not an idle communication channel in the next serving beam or satellite. The Earth-fixed cell method avoids these problems by allocating communication channels (frequency, code, and/or time slot) on an Earth-fixed cell basis rather than on a satellite-fixed cell basis. Regardless of which satellite/beam is currently serving a particular cell, the terminal maintains the same channel assignment, thus ameliorating the 'hand-off' problem.

Earth-fixed cell beam management for satellite communication system

A series of spacecraft designs (10, 42 and 52) for a Satellite Communication System is disclosed. One of the preferred embodiments of the invention called 'Gearsat.TM.' (10) comprises a hollow torus which inflates when it reaches orbit. When viewed from the side along its circumference, Gearsat (10) looks like two flattened pyramids sharing a common base. Phased array antenna panels (14) are deployed across the top of the pyramid along an exterior cylindrical surface (12), while twin arrays of solar cells (16) cover the slanted surfaces. The satellite (10) rotates about its center, and individual antenna panels (14) are spatially synchronized to transmit and receive signals from particular regions on the ground. An alternative embodiment, called 'Batsat.TM.' (42, 52), includes a central cylindrical body (B) and a plurality of substantially circular linked antenna and solar/thermal panels (A1-A9 and S1 and S2) which carry individual antennas (X) and solar/thermal surfaces (Y). All of the embodiments (10, 42 and 52) are capable of being nested or stacked in a compact arrangement that fit within the payload bay of a launch vehicle (L).

Inflatable torus and collapsible hinged disc spacecraft designs for

Earth-fixed cell beam management methods which may be employed to allocate beams generated by a constellation of low Earth orbit satellites (12) flying in orbits below geosynchronous altitudes are disclosed. These beams (19) are electronically steered so that they illuminate 'Earth-fixed cells' (26) as opposed to 'satellite-fixed cells.' In a system that employs satellite-fixed cells, the 'footprint' of the beams propagated by a spacecraft defines the zone on the ground called a 'cell' which is illuminated by the spacecraft. This satellite-fixed cell moves constantly as the spacecraft moves around the globe. In sharp contrast, an 'Earth-fixed cell' (26) is a stationary region mapped onto the surface of the Earth (E) that has permanent fixed boundaries, just like a city or a state. Although the rapidly moving satellites (12) still shine their beams over the ground in rapidly moving footprints (16), the locations of the footprints at any given time do not determine the location of the unchanging Earth-fixed cells (26). The great advantage provided by using cells having boundaries that are fixed to an Earth-fixed grid (20) is realized when a subscriber being served by one satellite must switch to another beam in the same satellite or to a second satellite because the first is moving out of range below the local horizon. With satellite-fixed cells, this 'hand-off' involves the assignment to the terminal of a new communication channel within the new beam or new satellite. This assignment process takes time and consumes processing capacity at both the terminal and the satellite. It is also subject to blocking, call interruption, and call dropping if there is not an idle communication channel in the next serving beam or satellite. The Earth-fixed cell method avoids these problems by allocating communication channels (frequency, code, and/or time slot) on an Earth-fixed cell basis rather than on a satellite-fixed cell basis. Regardless of which satellite/beam is currently serving a particular cell, the terminal maintains the same channel assignment, thus ameliorating the 'hand-off' problem.

Growing community of inventors

Los Altos, CA, United States of America

David Palmer Patterson