Low earth orbit (LEO) satellite communication methods and systems using fractionated satellites and high-resolution spatial multiplexing

A system for communication comprising:

• at least one fractionated satellite, the at least one fractionated satellite comprising a plurality of satellites, each of the plurality of satellites comprising:
• an antenna;
• a relative orbit location and
• an absolute pointing direction,
• wherein the antennas of the plurality of satellites form a phased array antenna,
• wherein the phased array antenna are configured to establish uplink and downlink communication links with user equipment on a surface of the earth using synthesized uplink and downlink antenna patterns, and
• wherein nulls of the synthesized uplink and down link patterns are placed on undesired co-frequency user equipment,
• wherein:
• the downlink antenna patterns are formed at the satellites, individually for each of a plurality of desired user equipment in the presence of a plurality of undesired use equipment sharing the same frequency and time with the desired user equipment,
• the downlink antenna pattern creates a relatively high gain towards the desired user equipment and a relatively low gain towards the plurality of undesired user equipment such that a ratio of powers of desired and undesired signals at the fractionated satellite exceeds a desired value,
• the downlink antenna patterns are formed based on using unique pilot signals transmitted by each satellite, and
• the downlink antenna patterns are formed based on:
• each user equipment computing a vector of downlink channel state estimates based on the unique pilot signals received from the plurality of satellites, the vector of downlink channel state estimates being identified by a time of receipt at the user equipment,
• each user equipment transmitting the downlink channel state vectors back to the plurality of satellites using the uplink communication links from the user equipment to the satellites,
• downlink channel state vectors corresponding to times of receipt within a coherence block being collected in an initial channel state matrix,
• the initial channel state matrix being used to predict a predicted channel state matrix at a future time, identified by a scheduled transmit time, using a prediction algorithm,
• an optimal weight vector is calculated for each of the plurality of user equipment, using an optimization method whose inputs include the predicted channel state matrix and a predicted channel state vector for the user equipment, wherein the predicted channel state vector is additionally provided by the prediction algorithm, and
• form a downlink signal vector destined for each user equipment formed by calculating a scalar product between the optimal weight vector and a scalar user signal for the user equipment,
• wherein the downlink signal vectors for a plurality of user equipment are linearly added to form a composite transmit vector and the composite transmit vector is transmitted using the phased array antenna of the fractionated satellite.