Medium-earth-altitude satellite-based cellular telecommunications system

A medium-earth-orbit satellite-based communications system for providing communication between low-power mobile handsets having an omni-directional antenna and a gateway station through a satellite forming part of a satellite constellation, comprising:

• a plurality of satellites orbiting at an altitude between 5600 and 10000 nautical miles and oriented in a plurality of orbital planes, wherein each orbital plane is inclined at a predetermined inclination angle with respect to the equatorial plane of the earth, and wherein at least one of said satellites includes an antenna field of view (FOV) less than full earth coverage;
• and
• a plurality of relatively low-powered mobile handsets including omni-directional antennas for transmitting radio frequency (RF) signals to said satellites;
• wherein a portion of a coverage region of a departing satellite overlaps a portion of a coverage region of an arriving satellite, and including assignment means having a predetermined criterion of assignment that calls placed to or from a user located within the coverage overlap region are assigned to said arriving satellite to minimize satellite-to-satellite handovers.

A method of providing medium-earth-orbit satellite-based communications between low-power mobile handsets having an omni-directional antenna and a gateway station through a satellite forming part of s satellite constellation, comprising the steps of:

• launching a plurality of satellites to an orbiting altitude between 5600 and 10,000 nautical miles, wherein at least one satellite has an antenna field of view (FOV) less than a full earth coverage;
• orienting said satellites in a plurality of orbital planes which are inclined at a predetermined inclination angle with respect to the equatorial plane of the earth;
• receiving, by at least one of said satellites, radio frequency (RF) signals from a plurality of mobile handsets which transmit said RF signals using their omni-directional antennas;
• overlapping a portion of a coverage region of a departing satellite with a portion of a coverage region of an arriving satellite, including assignment means having a predetermined criterion of assignment that calls placed to or from a user located within the coverage overlap region are assigned to said arriving satellite;
• and
• directing an antenna boresight on a sequence of coverage regions assigned thereto including at least one of periodically adjusting the attitude of at least one satellite to direct the antenna boresight on the current coverage region assigned thereto, and periodically gimballing and rotating the antenna of at least one satellite to direct the antenna boresight on the current coverage region assigned thereto.

A medium-earth-orbit satellite-based communications system for providing communication between low-power mobile handsets having an omni-directional antenna and an earth station through a satellite forming part of a satellite constellation, comprising:

• a plurality of satellites orbiting at an altitude between 5600 and 10000 nautical miles and oriented in a plurality of orbital planes, wherein each orbital plane is inclined at a predetermined inclination angle with respect to the equatorial plane of the earth, and wherein at least one of said satellites includes an antenna having a field of view (FOV) less than full earth coverage;
• a plurality of relatively low-power mobile handsets including omni-directional antennas for transmitting radio frequency (RF) signals to said satellites;
• and
• directing means for adjusting a boresight of said satellite antenna to provide directed coverage as the satellite orbits over a currently assigned service region, by performing at least one of periodically adjusting the attitude of the satellite to maintain the antenna boresight on the current service region, and periodically gimballing and rotating the antenna to maintain the antenna boresight on the current service region;
• wherein a portion of a coverage region of a departing satellite overlaps a portion of a coverage region of an arriving satellite, and including assignment means having a predetermined criterion of assignment that calls placed to or from a user located within the coverage overlap region are assigned to said arriving satellite to minimize satellite-to-satellite handovers.

A medium-earth-orbit, satellite-based cellular telecommunications system, comprising:

• a constellation of telecommunications satellites providing a multibeam radio frequency (rf) communications link for a number of mobile cellular telephones having omni-directional antennas, the satellites being placed in a plurality of inclined orbits about the earth at an altitude of between approximately 5600 and 10,000 nautical miles, such that the station-to-station propagation delay time of said communication link is no less than 60 milli-seconds and no more than 150 milli-seconds;
• wherein at least one satellite includes a multi-beam antenna and directing means for adjusting the antenna boresight to provide directed antenna coverage as the satellite orbits over a currently assigned service region for the satellite;
• wherein the characteristics of these orbits, such as the number of orbits, the inclination of each orbit, the number of satellites in each orbit and the altitude of the satellites, are tailored to maximize the coverage area of the satellites and their related line-of-sight elevation angles for predetermined service regions of the earth, while minimizing propagation time delays, the number of beam-to-beam and satellite-to-satellite handovers, and the total number of satellites;
• and
• wherein the number of satellite-to-satellite handovers is further reduced by overlapping a portion of a coverage region of a departing satellite with a portion of a coverage region of an arriving satellite, including assignment means having a predetermined criterion of assignment that calls placed to or from a user located within the coverage overlap region are assigned to said arriving satellite.