Return link channel loading of multiple satellites with multiple spread spectrum user terminals

• US 6,628,921 B1
• Filed: 10/13/2000
• Issued: 09/30/2003
• Est. Priority Date: 10/13/2000
• Status: Active Grant

• Current Assignee: Globalstar Incorporated
• Original Assignee: Globalstar Incorporated
• Inventors: Yao, Yiming, Vaddiparty, Subrahmanyam V., Monte, Paul A.
• Primary Examiner(s): Maung, Nay
• Assistant Examiner(s): Orgad, Edan
• Application Number:
  US09/687,664
• Time in Patent Office: 1,082 Days
• Field of Search: 455/12.1, 455/13.1, 455/427, 455/450, 455/509, 455/452, 455/464, 455/403, 455/422, 455/453, 455/7, 455/512
• US Class Current: 455/12.1
• CPC Class Codes: H04B 7/1851 Systems using a satellite or space-based relay H04B7/18508, H04B7/18521 take precedence; providing specific services H04B7/18523 - H04B7/18576

Abstract

The satellite communication system comprises a plurality of satellites. The frequency bandwidth of the return link to each satellite is subdivided into a plurality of channels. The method includes steps of finding a total interference in each channel, calculating a predicted total interference from addition of a first user terminal to each channel, determining if the predicted total interference is a minimum, and allocating the first channel to the first user terminal. The predicted total interference is calculated for each channel of the plurality of channels in the return link to each of at least two satellites. The first channel is allocated to the first user terminal if the predicted total interference in the first channel is the minimum value.

Claims

1. A method for maximizing capacity of a satellite communication system comprising the steps of:

finding a total interference in each channel of a plurality of channels which subdivide a predetermined frequency band of a return link to each satellite from a plurality of satellites of the communication system;

calculating a predicted total interference from an addition of a first user terminal on each channel of the plurality channels in the return link to each of at least two satellites of the plurality of satellites;

determining if the predicted total interference in a first channel of the plurality of channels is a minimum value relative to all predicted total interference values; and

allocating the first channel to the first user terminal if the predicted total interference in the first channel is the minimum value.

2. A method as in claim 1, wherein if the predicted total interference in the first channel is not a minimum, the method further comprises the step of determining if the predicted total interference in a second channel is less than a predetermined threshold value;

and allocating the second channel to the first user terminal if the predicted total interference in the second channel is less than the threshold value.

3. A method as in claim 2, wherein if the predicted total interference in the second channel is not less than the threshold value, the method further comprises the steps of:

determining if the predicted total interference in a third channel is less than the threshold value;

if yes, then determining if the first satellite is at an elevation angle, relative to the user terminal, that is smaller than an elevation angle of a second one of the two satellites; and

if yes, allocating the third channel to the first user terminal.

4. A method as in claim 3, wherein if the predicted total interference in the third channel is not less than the predetermined threshold, or if the elevation angle of the first satellite is not smaller than the elevation angle of the second satellite, the method further comprises the step of allocating the user terminal a fourth channel, wherein the fourth channel exhibits a minimum combined average interference density across said first and second satellites, from the combined interference density across said first and second satellites for all available channels.

5. A method as in claim 1, wherein the step of finding the total interference comprises the steps of:

calculating an interference in each channel of the plurality of channels of the return link to each satellite at a predetermined initial time; and

updating the interference in each channel of the plurality of channels of the return link to each satellite by adding the interference of each user terminal allocated to a corresponding one of the channels and subtracting the interference of each user terminal which terminates service on the corresponding channel.

6. A method as in claim 5, wherein the interference in each channel of the plurality of channels of the return link to each satellite is updated at predetermined time periods after the initial time.

7. A method as in claim 1, further comprising the step of registering the total interference in each channel of the plurality of channels of the return link to each satellite in a database of the satellite communication system.

8. A method as in claim 1, wherein the step of calculating a predicted total interference comprises the step of identifying a location and type of the first user terminal when the user terminal request service.

9. A method as in claim 1, wherein a processor of the satellite communication system registers other radio frequency services located proximate to the first user terminal.

10. A method as in claim 1, wherein the predicted total interference is calculated when the first user terminal requests service.

11. A method for assigning a frequency channel to a user terminal of a satellite communication system, the user terminal being illuminated by at least two satellites from a plurality of satellites of the communication system, wherein the method comprises the steps of:

identifying at least one of a location and a type of the user terminal when the user terminal requests service;

determining if a first frequency channel from a plurality of frequency channels for a return link of the user terminal to each one of the two satellites has a minimum total interference density relative to the plurality of frequency channels;

if yes, assigning the first frequency channel to the user terminal;

if no, then determining if a second frequency channel from the plurality of frequency channels for the return link of the user terminal to each satellite has a total interference density below a predetermined threshold;

if yes, assigning the second frequency channel to the user terminal;

if no, then determining if a third frequency channel from the plurality of frequency channels has a total interference density below the predetermined threshold for the return link of the user terminal to a first one of the two satellites and a total interference density above the predetermined threshold for the return link of the user terminal to a second one of the two satellites;

if yes, then determining if the first satellite is at a lower elevation with respect to the user terminal than the second satellite;

if yes, then assigning the third channel to the user terminal; and

if no, or if the total interference density in the third frequency channel for the return link of the user terminal to the first satellite is above the predetermined threshold, then assigning a fourth frequency channel from the plurality of frequency channels for the return link of the user terminal;

wherein

the fourth frequency channel exhibits a minimum combined average interference density across said first and second satellites, relative to the combined interference density across said first and second satellites for all available channels.