Multipath communication system optimizer

• US 5,796,760 A
• Filed: 07/30/1997
• Issued: 08/18/1998
• Est. Priority Date: 05/09/1994
• Status: Expired due to Term

• Current Assignee: Globalstar Incorporated
• Original Assignee: Globalstar Incorporated
• Inventors: Wiedeman, Robert A., Monte, Paul
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US08/903,166
• Time in Patent Office: 384 Days
• Field of Search: 375/200, 375/211, 375/206, 375/267, 375/295, 375/219, 375/299, 375/316, 375/347, 375/225, 375/226, 375/227, 375/229, 375/260, 370/320, 370/335, 370/279, 370/293, 370/315, 370/316, 455/427, 455/13.1, 455/7, 455/137, 455/132, 455/226.1, 455/59
• US Class Current: 375/130
• CPC Class Codes: H04B 7/18534 for enhancing link reliablility, e.g. satellites diversity
• CPC Class Codes: H04B 7/18543 for adaptation of transmission parameters, e.g. power control for detecting or preventing errors in the information received H04L1/00
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

A multi-path device includes a plurality of communication paths being defined between a plurality of first transceivers and one second transceiver. Each communication path contains at least one repeater. Each signal transmission from the first transceiver to the second transceiver contains an identifiable copy of an identical signal copy over each communication path. There is a signal quality determining portion associated with the second transceiver for determining the quality of the signal copy received by the second transceiver via each of said communication paths. A communication path limiting portion controls the strength of each communication path based upon said signal quality determining portion. It is envisioned that this device may use a CDMA communication protocol.

Claims

1. A satellite communication system, comprising:

a plurality of satellite-based signal repeaters in low earth orbit;

a groundstation comprised of a plurality of code division multiple access (CDMA) spread spectrum transceivers, each of said plurality of transceivers being coupled to a directional antenna for transmitting spread spectrum signals to and for receiving spread spectrum signals from one of said plurality of signal repeaters;

a user terminal comprised of a CDMA spread spectrum transceiver that is coupled to an omni-directional antenna for simultaneously transmitting spread spectrum signals to and for receiving spread spectrum signals from two or more of said directional antennas via two or more of said plurality of signal repeaters;

wherein at least two of said plurality of spread spectrum transceivers of said groundstation simultaneously transmit a same communication signal to said user terminal through different ones of said plurality of repeaters, said transmitted communication signals being identifiable one from the other;

wherein said user terminal is comprised of circuitry for repetitively determining a signal quality of each communication signal received through at least some of said different ones of said plurality of repeaters, and for periodically and simultaneously transmitting a signal indicating said determined signal qualities back to said groundstation through said at least some of said different ones of said plurality of repeaters; and

wherein

said groundstation is responsive to a receipt of the periodically transmitted signal from said user terminal for selectively and independently activating the transmission of, deactivating the transmission of, and controlling the transmission power of individual ones of said plurality of spread spectrum transceivers that are simultaneously transmitting said same communication signal through said different ones of said plurality of repeaters.

2. The satellite communication system of claim 1, wherein said signal quality determining means utilizes at least one of an error rate, a carrier to noise ratio, or a correlation measure of each received signal copy.

3. The satellite communications system of claim 1, wherein said user terminal is further comprised of a plurality of receiver channels individual ones of which can be assigned to correlate one of said identifiable signals transmitted from said groundstation, an equalizer for equalizing said correlated signals to compensate at least for a difference in path length and Doppler frequency offset between the correlated signals, and a combiner for combining the equalized signals to provide a composite received signal.

4. The satellite communications system of claim 3, wherein said circuitry for repetitively determining a signal quality of each communication signal is disposed before said combiner.