Method and apparatus for code assignment in a spread spectrum wireless communication system

• US 6,714,526 B2
• Filed: 12/15/2000
• Issued: 03/30/2004
• Est. Priority Date: 12/15/2000
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tiedemann, Edward G. Jr., Black, Peter J., Wei, Yongbin
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): JAIN, RAJ K
• Application Number:
  US09/737,893
• Publication Number:
  US 20020110102A1
• Time in Patent Office: 1,201 Days
• Field of Search: 370/342, 370/343, 370/344, 370/345, 370/335, 370/319, 370/320, 375/130, 375/133, 375/140, 375/141, 375/149, 455/456.1
• US Class Current: 370/335
• CPC Class Codes: H04B 1/7097 Interference-related aspects
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 13/18 Allocation of orthogonal codes

Abstract

Method and apparatus for code assignments in a spread-spectrum wireless communication system incorporating a Large Area Synchronized-Code Division Multiple Access (LAS-CDMA) protocol. The method determines a set of LS codes based on an interference free window size. An arborescence structure provides the correspondence between the interference free window size and the set of LS codes. Subsets of the LS codes are formed having null cross-correlation within the interference free window. The subsets are assigned to neighboring cells in the system to reduce interference between neighbors. In one embodiment, a controller determines the subsets and makes the assignments to cells within the system.

Claims

1. In a wireless communication system adapted for Large Area Synchronized-Code Division Multiple Access (LAS-CDMA) transmissions, the transmissions using LS codes for spread-spectrum modulation, a method comprising:

determining a size of an interference free window (IFW);

calculating a plurality of subsets of LS codes, each subset comprising a number of LS codes as a function of the IFW;

assigning a first of the plurality of subsets to a first portion of the system; and

assigning a second of the plurality of subsets to a second portion of the system.

2. The method of claim 1, wherein the calculating further comprises:

determining a number of subsets for application within the system;

determining the first subset of LS codes having null cross-correlation with respect to each other; and

determining the second subset of LS codes having null cross-correlation with respect to each other.

3. The method of claim 1, further comprising:

identifying mobile stations within the first portion of the system with LS codes from the first of the plurality of subsets; and

identifying mobile stations within the second portion of the system with LS codes from the second of the plurality of subsets.

4. The method of claim 1, wherein a cross-correlation of the LS codes within the first and second of the plurality of subsets is null within the IFW.

5. The method of claim 1, wherein the size of the IFW corresponds to an LS code length, and wherein calculating the plurality of subsets further comprises:

generating seed pairs given as;

6. The method as in claim 5, further wherein the number of subsets is at least three.

7. A wireless communication system incorporating a LAS-CDMA protocol, comprising:

a first cell, the first cell being assigned a first subset of LS codes; and

a second cell, the second cell being assigned a second subset of LS codes,

wherein the first and second subsets have a null cross-correlation within a predetermined interference free window.

8. The system as in claim 7, wherein the first and second cells are neighboring cells.

9. The system of claim 8, further comprising:

a first neighborhood of cells each neighboring the first cell, wherein the

second cell is in the first neighborhood.

10. The system of claim 9, further comprising:

a third cell within the first neighborhood, the third cell being assigned a third subset of LS codes, wherein the LS codes within the first and third subsets have a null cross-correlation within the predetermined interference free window.

20. The signal of claim 8, wherein a second set of LS codes is assigned to a second cell within the first cell neighborhood.

11. In a Large Area Synchronized-Code Division Multiple Access wireless communication system, a method comprising:

transmitting a first communication within a first cell, the first communication identifying at least one mobile station within the first cell by a first LS code within a first subset of LS codes; and

transmitting a second communication within a second cell, the second communication identifying at least one mobile station within the second cell by a second LS code within a second subset of LS codes;

wherein a cross-correlation between any two LS codes within the first is null within an interference free window, and the cross-correlation between any two LS codes within the second subset is null within the interference free window.

12. The method of claim 11, wherein the first and second subsets of LS codes are part of a set of LS codes defined by the interference free window.

13. The method of claim 12, wherein for the set of LS codes comprises 128 codes, the interference free window equal to [−

1,+1] corresponds to 64 available codes for forming subsets.

14. The method of claim 12, wherein a correspondence between the interference free window and a number of available codes for forming subsets is based on an arborescence structure.

15. A controller in a Large Area Synchronized-Code Division Multiple Access wireless communication system, comprising:

a first set of instructions for determining an interference free window size for communications between neighboring cells; and

a second set of instructions for determining at least two sets of LS codes based on the interference free window size, a first set for identifying mobile stations in a first cell and a second set for identifying mobile stations in a neighboring cell;

wherein the LS codes within the two sets of LS codes have a null cross-correlation within an interference free window.

16. The controller of claim 15, further comprising:

a third set of instructions for assigning the first set of LS codes to communications in the first cell; and

a fourth set of instructions for assigning the second set of LS codes to communications in the second cell.

17. In a Large Area Synchronized-Code Division Multiple Access wireless communication system, the system having a first cell and a first cell neighborhood, a computer data signal embodied on a carrier wave, the signal comprising:

a first portion comprising header information for transmission to a first mobile user in a first cell; and

a second portion comprising a first LS code corresponding to the first mobile user, the first LS code being part of a first set of LS codes, and

wherein within the first cell neighborhood, the first LS code is assigned only to the first cell.

18. The signal of claim 17, further comprising:

a third portion comprising the first LS code.

19. The signal of claim 18, wherein:

the second portion has an associated first data symbol and the third portion has an associated second data symbol,

the second portion further comprises the first LS code modulated by the first data symbol; and

the third portion further comprises the first LS code modulated by the second data symbol.

21. In a wireless communication system incorporating a LAS-CDMA protocol, a first cell, comprising:

a first set of computer readable instructions adapted to receive a first LS code set, the first LS code set having a plurality of LS codes of a predetermined first length, wherein each of the plurality of LS codes in the first LS code set has a null cross-correlation with respect to each other LS code in the first LS code set; and

a second set of computer readable instructions adapted to generate a data signal on a carrier wave, the data signal comprising;

a first portion comprising header information for transmission to a first mobile within the first cell; and

a second portion comprising a first LS code corresponding to the first mobile user, the first LS code being part of the first LS code set.

22. A wireless apparatus adapted for operation with the first cell of claim 21.