Synchronized CPDMA (code phase division multiple access)
A communications protocol in accordance with one exemplary embodiment uses information from GPS satellites to synchronize the phases of transmitters, and aligns the phase with a spreading code used to de-spread the received signals at, for example, a ground station.
1. A communications system comprising:
a location determining module adapted to determine a location of one or more of a terminal and a geostationary communications satellite; and
an alignment module, the alignment module at least in communication with and at least using information corresponding to the determined location from the location determining module to align arrival code-phases of signals for a ground station receiver by altering a clock for a modulated signal transmitted from the terminal,
wherein the alignment module:
determines an alignment time and aligns a code-phase of a spreading code on a clock tick boundary, wherein the determining of the alignment time includes:
determining a geographic position of the terminal;
determining a position of the communications satellite;
determining a distance between the terminal and the communications satellite; and
adjusting a starting time of the spreading code by a function of a communications signal travel distance modulo predetermined time period.
2. The system of claim 1 , wherein the adjusting comprises subtracting a time the communications signal travels along a distance modulo predetermined time period from a predetermined time period.
3. The system of claim 1 , wherein the determining of the alignment time includes:
determining a geographic position of the terminal;
determining a position of the communications satellite;
determining a distance between the terminal and the communications satellite; and
adjusting a starting time of the spreading code by a function of a distance the communications signal travels from the terminal to the communications satellite modulo predetermined time period.
4. The system of claim 1 , wherein the determining of the alignment time includes:
determining a geographic position of the terminal;
determining a geographic position of the ground station receiver;
determining a position of the communications satellite;
determining a distance between the terminal and the communications satellite;
determining a distance between the ground station receiver and the communications satellite;
establishing a total distance a signal traverses by adding the distance between the a terminal and the communications satellite and the distance between the ground station receiver and the communications satellite; and
adjusting a starting time of the spreading code by a function of a communications signal travel distance modulo predetermined time period.
5. The system of claim 4 , wherein the adjusting comprises subtracting a time the communications signal travels along the distance modulo predetermined time period from the predetermined time period.
6. The system of claim 1 , further comprising a ground station alignment module adapted to align code-phase timing of the spreading code used by the ground station receiver to de-spread a received signal with a specific time period clock ticks aligned with a universal GPS clock timing.
7. The system of claim 1 , further comprising a phase delta module, a universal time module, a clock and a travel time calculation module in communication with the location determining module.
8. A communications method for a communications terminal comprising:
determining a location of one or more of the communications terminal and a geostationary communications satellite;
using information corresponding to the determined location to align arrival code-phases of signals as a ground station receiver; and
determining an alignment time and aligning a code-phase of a spreading code on a clock tick boundary for a signal transmitted from the terminal, wherein the determining of the alignment time includes:
determining a geographic position of the terminal;
determining a position of the communications satellite;
determining a distance between the terminal and the communications satellite; and
adjusting a starting time of the spreading code by a function of a communications signal travel distance modulo predetermined time period.
9. The method of claim 8 , wherein the adjusting comprises subtracting a time the communications signal travels along a distance modulo predetermined time period from a predetermined time period.
10. A communications method for a communications terminal comprising:
determining a location of one or more of the communications terminal and a geostationary communications satellite;
using information corresponding to the determined location to align arrival code-phases of signals at a ground station receiver; and
determining an alignment time and aligning a code-phase of a spreading code on a clock tick boundary for a signal transmitted from the terminal, wherein the determining of the alignment time includes:
determining a geographic position of the terminal;
determining a position of the communications satellite;
determining a distance between the terminal and the communications satellite; and
adjusting a starting time of the spreading code by a function of a distance the communications signal travels from the terminal to the communications satellite modulo predetermined time period.
11. A communications method for a communications terminal comprising:
determining a location of one or more of the communications terminal and a geostationary communications satellite;
using information corresponding to the determined location to align arrival code-phases of signals at a ground station receiver; and
determining an alignment time and aligning a code-phase of a spreading code on a clock tick boundary for a signal transmitted from the terminal, wherein the determining of the alignment time includes:
determining a geographic position of the terminal;
a determining a geographic position of the ground station receiver;
determining a position of the communications satellite;
determining a distance between the terminal and the communications satellite;
determining a distance between the ground station receiver and the communications satellite;
establishing a total distance a signal traverses by adding the distance between the terminal and the communications satellite and the distance between a ground station receiver and the communications satellite; and
adjusting a starting time of the spreading code by a function of a communications signal travel distance modulo predetermined time period.
12. The method of claim 10 , wherein the adjusting comprises subtracting a time the communications signal travels along the distance modulo predetermined time period from the predetermined time period.
13. The method of claim 11 , further comprising aligning code-phase timing of the spreading code used by the ground station receiver to de-spread a received signal with a specific time period clock ticks aligned with a universal GPS c timing and updating an internal clock and determining a universal time.