Satellite communication system

• US 6,215,776 B1
• Filed: 10/08/1997
• Issued: 04/10/2001
• Est. Priority Date: 10/08/1997
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Space Operations Company (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Space Operations Company (Martin Marietta Corporation)
• Inventors: Chao, William W.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US08/947,015
• Time in Patent Office: 1,280 Days
• Field of Search: 370/316, 370/321, 370/331, 370/332, 370/337, 455/12.1, 455/13.1, 455/13.3, 455/430, 455/432, 455/436, 455/427
• US Class Current: 370/316
• CPC Class Codes: H04B 7/18589 Arrangements for controlling an end to end session, i.e. for initialising, synchronising or terminating an end to end link

Abstract

A multimedia communication system having a plurality of mobile, fixed location, and portable terrestrial communication terminals. The system links terrestrial communication terminals together through a network of non-geostationary satellites. The satellites communicate with a communication protocol similar to terrestrial communication protocols to reduce protocol conversion. The source and destination addressing uses static terrestrial cells for the uplink and the downlink. The terminal data stream is segmented into communication packets at the terrestrial gateway based on the uplink satellite'"'"'s determination of system parameters. A control satellite dynamically balances up-links and down-links in the terrestrial areas with over-lapping satellite coverage.

Claims

1. A satellite communication system for multimedia communication comprising:

(a) a plurality of non-geostationary communication satellites;

(b) a plurality of mobile and terrestrial communication systems linked to the non-geostationary satellites;

(c) means for communicating between non-geostationary satellites using a satellite communication protocol which is compatible with mobile and terrestrial communication protocols and reduces protocol conversion;

(d) means for dynamically fixing the non-geostationary satellites with respect to terrestrial cells serving as transmitting and receiving points, wherein the means for dynamically fixing performs the steps of;

(i) defining terrestrial coverage areas as static cells; and

(ii) addressing the static cells in planes that are perpendicular to the orbits of the non-geostationary satellites, the addressing including variable resolution within the static cells.

(e) means for segmenting terminal data into communication packets for transmitting through the satellite communication system;

(f) means for routing communication packets among non-geostationary satellites using the satellite communication protocol; and

(g) means for dynamically balancing terrestrial communication links among the non-geostationary satellites in an over-lapping state.

2. The satellite communication system according to claim 1, wherein the means for communicating between the non-geostationary satellites includes communication packet comprising:

(a) terminal data;

(b) payload information;

(c) routing information; and

(d) an error correction code.

3. The satellite communication system according to claim 1, further including means for calculating an efficient communication packet size for transmitting terminal data through the satellite communication system, the calculating based on measuring communication factors including:

(a) an error rate;

(b) a quality of service;

(c) a traffic status;

(d) a cost of service; and

(e) a count of available links.

4. The satellite communication system according to claim 1, wherein the means for routing communication packets among non-geostationary satellites using the satellite communication protocol includes measuring communication factors including:

(a) an error rate;

(b) a quality of service;

(c) a traffic status;

(d) a cost of service; and

(e) a count of available links.

5. The satellite communication system according to claim 1, wherein the means for dynamically balancing the terrestrial communication links among satellites in an over-lapping state comprising:

(a) measuring communication factors in a static cell including;

(i) a traffic density;

(ii) a transport delay;

(iii) a quality of service;

(iv) a computational capacity;

(v) a lack of coverage timing;

(vi) a cost of service;

(vii) a traffic status;

(viii) an error rate in the source and destination static cells;

(b) measuring satellite factors for each satellite in the over-lapping state including;

(i) a logical user identification of a terminal;

(ii) a connection time of each connection;

(iii) a satellite identification;

(iv) an end of coverage time;

(v) a traffic status specific to each satellite in the overlapping state;

(vi) an access code; and

(c) allocating terrestrial links to the non-geostationary satellites covering the static cells such that loads are balanced between over-lapping satellites based on the communication factors and the satellite factors.

6. The satellite communication system according to claim 1, wherein the links between the non-geostationary satellites and the terrestrial communication systems are managed by a control satellite in each static cell comprising the steps of:

(a) selecting one of the non-geostationary satellites first in time to enter the static cell to control communication links within that static cell;

(b) requesting satellite information from each satellite upon entering the static cell;

(c) assigning new terrestrial links to non-geostationary satellites based on the control satellite'"'"'s determination of satellite information of each satellite covering the static cell;

(d) re-assigning existing terrestrial links to a different non-geostationary satellites based on the control satellite'"'"'s determination of the satellite information of each satellite covering the static cell; and

(e) assigning a different satellite to control the static cell before a current control satellite leaves the static cell.

7. The satellite communication system according to claim 1, wherein each non-geostationary satellite determines a route for each communication packet by referencing a dynamic routing table using a context switch marker to reduce search time, the context switch marker provides a reference point in a static cell data base for searching for the static cell'"'"'s location and routing information.

8. A satellite communication system capable of multimedia communication comprising:

(a) a plurality of non-geostationary communication satellites, each of the plurality of non-geostationary communication satellites being assigned to cover a static terrestrial cell;

(b) a plurality of control satellites which are a subset of the plurality of non-geostationary communication satellites, each control satellite being assigned to cover a static terrestrial cell and each static terrestrial cell being assigned no more than one control satellite, wherein each control satellite dynamically balances terrestrial communication links among the satellites assigned to the corresponding static terrestrial cell such that the loads are balanced between the satellites covering that static terrestrial cell;

(b) a first non-geostationary communication satellite assigned to cover a first static terrestrial cell;

(c) a first gateway located in the first static terrestrial cell, the first gateway

(i) receiving a first data stream having a terrestrial protocol from a first terrestrial communication unit;

(ii) converting the first data stream into communication packets having a satellite communication protocol, wherein the satellite communication protocol is similar to the terrestrial protocol;

(iii) sending the communication packets to the first non-geostationary communication satellite over a first link;

(d) a second non-geostationary communication satellite assigned to cover a second static terrestrial cell, the second non-geostationary communication satellite receiving the communication packets routed from the first non-geostationary communication satellite; and

(e) a second gateway located in the second static terrestrial cell receiving the communication packets from the second non-geostationary communication satellite over a second link, converting the communication packets into a second data stream having the terrestrial protocol, and sending the second data stream to a second terrestrial communication unit.

9. The satellite communication system of claim 8, wherein each control satellite makes a load determination based on communication factors and satellite factors.

10. The satellite communication system of claim 9, wherein the communication factors include at least one of:

(i) a traffic density;

(ii) a transport delay;

(iii) a quality of service;

(iv) a computational capacity;

(v) a lack of coverage timing;

(vi) a cost of service;

(vii) a traffic status; and

(viii) an error rate in the source and destination static cells.

11. The satellite communication system of claim 9, wherein the satellite factors are factors specific to a satellite and include at least one of:

(i) a logical user identification of a terminal;

(ii) a connection time of each connection;

(iii) a satellite identification;

(iv) an end of coverage time;

(v) a traffic status; and

(vi) an access code.

12. The satellite communication system of claim 8, wherein when a satellite moves to a new static terrestrial cell with no satellites assigned to that static terrestrial cell, the satellite assigns itself as a control satellite for that static terrestrial cell.

13. The satellite communication system of claim 9, wherein when a satellite moves to a new static terrestrial cell it requests satellite information for all satellites in the new static terrestrial cell from the control satellite assigned to the new static terrestrial cell.

14. The satellite communication system of claim 13, wherein when a satellite exits a static terrestrial cell, the satellite transmits its satellite information to the control satellite for that static terrestrial cell.

15. The satellite communication system of claim 14, wherein when a control satellite exits a static terrestrial cell, the control satellite assigns a different satellite as the new control satellite for that static terrestrial cell before leaving the cell.

16. The satellite communication system of claim 15, wherein the control satellite exiting the static terrestrial cell determines the satellite with the longest remaining coverage time in that static terrestrial cell, and assigns that satellite as the new control satellite.

17. The satellite communication system of claim 16, wherein the satellite information includes at least one of:

(a) a connection time of each terrestrial link;

(b) a satellite identification; and

(c) an end of coverage time per gateway.

18. The satellite communication system of claim 8, wherein each control satellite assigned to a static terrestrial cell maintains satellite coverage information including:

(a) coverage time remaining for satellites assigned to that static terrestrial cell; and

(b) time until coverage for satellites that will move into that static terrestrial cell in the future.

19. The satellite communication system of claim 8, wherein a control satellite transmits a message to a gateway before it will be blacked-out, the message identifying the black-out start time and black-out stop time.

20. The satellite communication system of claim 19, wherein a gateway enters a black-out period and the gateway:

(1) routes messages over available terrestrial links during black-out periods;

or

(2) stores communication data streams during a black-out period and transmits the stored communication data over a satellite link once satellite coverage resumes.

21. The satellite communication system of claim 8, wherein the first gateway requests an optimal communication packet payload length from the first non-geostationary communication satellite, the first non-geostationary communication satellite determining an optimal communication packet payload length based on system parameters and communication parameters.

22. The satellite communication system of claim 21, wherein the system parameters include at least one of:

(a) which satellites are available to link to the first and second gateways;

(b) loads on each of the available satellites;

(c) an error rate of each satellite;

(d) a cost of service; and

(e) number of hops required.

23. The satellite communication system of claim 21, wherein the communication parameters include at least one of:

(a) a priority;

(b) a hop count; and

(c) an amount of data to be transferred.

24. The satellite communication system of claim 8, wherein each communication packet includes:

(a) terminal data;

(b) payload information;

(c) a payload;

(d) routing information; and

(e) an error correction code.

25. The satellite communication system of claim 24, wherein the terrestrial protocol is at least one of Internet Protocol version 4 (IPv4), Internet Protocol Next Generation (IPv6), or asynchronous transfer mode (ATM).

26. The satellite communication system of claim 24, wherein the terrestrial protocol is comprised of data cells, and the payload comprises a plurality of the data cells.