Spreading code hopping for synchronous DS-CDMA system to mitigate interference effects

• US 20020097703A1
• Filed: 10/24/2001
• Published: 07/25/2002
• Est. Priority Date: 10/27/2000
• Status: Active Grant

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Inventors: Hall, Eric K., Giallorenzi, Thomas R., Ertel, Richard B., Nieczyporowicz, Leon L.
• Granted Patent: US 7,099,372 B2
• Time in Patent Office: Days
• US Class Current: 370/342
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 21/205 providing an omnidirectional coverage turnstile aerials H01Q21/26
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7097 Interference-related aspects
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 13/0074 Code shifting or hopping
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04W 16/12 Fixed resource partitioning

Abstract

Disclosed is a method for operating a code division multiple access communications system, and a system that operates in accordance with the method. The method operates within a coverage area of a base station by assigning a set of spreading codes to individual ones of a plurality of subscriber stations and then, during transmissions within the cell, by periodically hopping amongst spreading code within the set of spreading codes such that at any given time no two subscriber stations operate with the same spreading code. The set of spreading codes may include the all one'"'"'s spreading code. The step of periodically hopping preferably changes from a currently used spreading code to a next spreading code at a symbol rate or at a multiple of the symbol rate. The set of spreading codes may be a hopped sub-set of a larger set of spreading codes, and in this case the method further operates to assign a non-hopped sub-set of the larger set of spreading codes to individual ones of the plurality of subscriber stations for use on a system access channel and/or on a system control channel or, more generally, for use on a non-traffic channel. The system may be a fixed data rate system or a variable data rate system. In the latter case the step of periodically hopping may change from a currently used spreading code to a next spreading code at the symbol rate, or at a multiple of the symbol rate of the lowest or the highest symbol rate users.

Claims

1. A method for operating a code division multiple access communications system, comprising:

within a coverage area of a base station, assigning a set of spreading codes to individual ones of a plurality of subscriber stations; and

during transmissions within the cell, periodically hopping amongst individual ones of the spreading codes of the set of spreading codes such that at any given time no two subscriber stations operate with the same spreading code.

2. A method as in claim 1, wherein the set of spreading codes comprises an all one'"'"'s spreading code.

3. A method as in claim 1, wherein the set of spreading codes comprises a hopped sub-set of a larger set of spreading codes, and further comprising assigning a non-hopped sub-set of the larger set of spreading codes to individual ones of said plurality of subscriber stations for use on a system access channel.

4. A method as in claim 1, wherein the set of spreading codes comprises a hopped sub-set of a larger set of spreading codes, and further comprising assigning a non-hopped sub-set of the larger set of spreading codes to individual ones of said plurality of subscriber stations for use on a system control channel.

5. A method as in claim 1, wherein the set of spreading codes comprises a hopped sub-set of a larger set of spreading codes, and further comprising assigning a non-hopped sub-set of the larger set of spreading codes to individual ones of said plurality of subscriber stations for use on a non-traffic channel.

6. A method as in claim 1, wherein the step of periodically hopping changes from a currently used spreading code to a next spreading code at a symbol rate or at a multiple of the symbol rate.

7. A method as in claim 1, wherein the system is a fixed data rate system.

8. A method as in claim 1, wherein the system is a variable data rate system.

9. A method as in claim 1, wherein the system is a variable data rate system and wherein the step of periodically hopping changes from a currently used spreading code to a next spreading code at the symbol rate, or at a multiple of the symbol rate of one of the lowest symbol rate users.

10. A method as in claim 1, wherein the system is a variable data rate system and wherein the step of periodically hopping changes from a currently used spreading code to a next spreading code at the symbol rate, or at a multiple of the symbol rate of the highest symbol rate users.

11. A code division multiple access communications system, comprising a controller operating within a coverage area of a base station for assigning a set of spreading codes to individual ones of a plurality of subscriber stations;

and further comprising circuitry that is responsive to transmissions within the cell for periodically hopping amongst the set of spreading codes such that at any given time no two subscriber stations operate with the same spreading code.

12. A system as in claim 11, wherein the set of spreading codes comprises an all one'"'"'s spreading code.

13. A system as in claim 11, wherein the set of spreading codes comprises a hopped sub-set of a larger set of spreading codes, and where said controller further assigns a non-hopped sub-set of the larger set of spreading codes to individual ones of said plurality of subscriber stations for use on a system access channel.

14. A system as in claim 11, wherein the set of spreading codes comprises a hopped sub-set of a larger set of spreading codes, and where said controller further assigns a non-hopped sub-set of the larger set of spreading codes to individual ones of said plurality of subscriber stations for use on a system control channel.

15. A system as in claim 11, wherein the set of spreading codes comprises a hopped sub-set of a larger set of spreading codes, and where said controller further assigns a non-hopped sub-set of the larger set of spreading codes to individual ones of said plurality of subscriber stations for use on a non-traffic channel.

16. A system as in claim 11, wherein said circuitry changes from a currently used spreading code to a next spreading code at a symbol rate or at a multiple of the symbol rate.

17. A system as in claim 11, wherein the system is a fixed data rate system.

18. A system as in claim 11, wherein the system is a variable data rate system.

19. A system as in claim 11, wherein the system is a variable data rate system and wherein the step of periodically hopping changes from a currently used spreading code to a next spreading code at the symbol rate, or at a multiple of the symbol rate of the lowest symbol rate users.

20. A system as in claim 11, wherein the system is a variable data rate system and wherein the step of periodically hopping changes from a currently used spreading code to a next spreading code at the symbol rate, or at a multiple of the symbol rate of the highest symbol rate users.

21. A synchronous, direct sequence code division multiple access communications system, comprising a controller operating within a coverage area of a base station for assigning a set of spreading codes to individual ones of a plurality of subscriber stations;

and further comprising circuitry that is responsive to transmissions within the cell for periodically hopping amongst the set of spreading codes at a symbol rate or a multiple of a symbol rate such that at any given time no two subscriber stations interfere with one another by the use of the same spreading code, wherein the set of spreading codes comprises a hopped sub-set of a larger set of spreading codes, and where said controller further assigns a non-hopped sub-set of the larger set of spreading codes to individual ones of said plurality of subscriber stations for use on at least one of a system access channel or a system control channel.

22. A system as in claim 21, wherein the set of spreading codes comprises an all one'"'"'s spreading code.

23. A system as in claim 21, wherein the system operates as one of a fixed data rate system or as a variable data rate system.

24. A system as in claim 21, wherein the hops between spreading codes are made at a symbol boundary of all of the subscriber stations.