 Method for passing information between a local exchange and a user/terminal |
| OF EMBODIMENTS In the following there will be given a few examples of how the synchronisation of ... |
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| Method and apparatus for providing instant messaging in a wireless communication system |
| OF THE DRAWINGS Referring to FIG. 1, an apparatus 20 for providing Instant Messaging (IM) in a ... |
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| Method for terminating a wireless communication of a mobile communication unit |
| According to an aspect of the present invention, the foregoing needs are addressed by a method for ... |
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| Rules based methods and apparatus |
| In a principle aspect, the present invention takes the form of a rules-based system for monitoring ... |
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| Wireless data communications using FIFO for synchronization memory |
| A wireless network 100 (FIG. 1) includes a plurality of wireless devices 102-1, 102-2 . . . 102-i .... |
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| Wireless device having context-based operational behavior |
| OF THE PREFERRED EMBODIMENT In accordance with the invention, a wireless device uses profiles that ... |
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| System and method for wireless data exchange between an appliance and a handheld device |
| One aspect of the present invention relates to a wireless data exchange system. The wireless data ... |
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| Remote data acquisition and communication system |
| The invention comprises a remote data acquisition and communication system that includes a ... |
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| Method and system for reading intelligent utility meters |
| What is claimed: 1. A system for communicating with a plurality of utility meters, comprising: ... |
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Earth-fixed cell beam management for satellite communication system using dielectic lens-focused scanning beam antennas
| Details |
Inventors: Patterson, David Palmer; Sturza, Mark Alan;
Assignee: Teledesic Corporation (Kirkland, WA)
Primary Examiner: Issing; Gregory C.
Assistant Examiner:
Attorney, Agent or Firm: Christensen O'Connor Johnson & Kindness PLLC
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. |
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DETAILED DESCRIPTION The methods and apparatus described and claimed below pertain to a multibeam antenna system which is deployed aboard each satellite in a constellation of satellites orbiting below geo-synchronous altitude and the allocation of radio beams which are generated by the system.
The multibeam antenna system provides a plurality of beams transmitted and received from positions in Earth orbit, for communicating directly with a plurality of portable, mobile and fixed terminals and gateways.
A plurality of multibeam antennas is deployed on each satellite.
Each one of the multibeam antennas simultaneously receives and transmits a plurality of beams.
Each beam illuminates a segment of an Earth-fixed grid.
The beams are formed by each multibeam antenna, and are focused on the segment of the Earth-fixed grid by a dielectric lens.
Each beam is electronically shaped and steered to keep the segment of the Earth-fixed grid within the footprint of the beam.
Earth-Fixed Cell Beam Management The radio beams which are generated by the multibeam antenna system are precisely controlled so they illuminate "Earth-fixed" cells which are segments of an Earth-fixed grid.
In previous satellite communication schemes, spacecraft which are not held stationary over one particular location on the Earth in geosynchronous orbits fly over large regions of the Earth very rapidly.
The radio beams generated by these fast moving spacecraft sweep across vast regions of the Earth's surface at the same rapid rate of speed.
If these beams were visible to the eye, they would paint bright circular and elliptical patches of light on the ground beneath the satellite which emitted them.
In a system that employs "satellite-fixed" cells, the "footprint" of the radio beams propagated by the 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 orbits around the globe.
An Earth-fixed cell contrasts sharply with a satellite-fixed cell
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Cell Phones 
