Spreading code allocation method and system

• US 6,597,677 B1
• Filed: 07/16/1999
• Issued: 07/22/2003
• Est. Priority Date: 07/16/1998
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Segawa, Kazuhiro
• Primary Examiner(s): Le, Thanh Cong
• Assistant Examiner(s): CHOW, CHARLES CHIANG
• Application Number:
  US09/354,162
• Time in Patent Office: 1,467 Days
• Field of Search: 370/342, 370/329, 370/335, 370/337, 370/441, 370/437, 370/465, 370/468, 370/491, 455/446, 455/186.1, 455/447, 455/448, 455/442, 455/561, 455/456, 375/206, 375/200, 375/140, 375/137, 375/130, 375/149, 375/145
• US Class Current: 370/342
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04B 7/2668 Arrangements for Wireless Code-Division Multiple Access [CDMA] System Synchronisation, for code acquisition H04B1/7075, for code tracking H04B1/7085
• CPC Class Codes: H04J 13/18 Allocation of orthogonal codes
• CPC Class Codes: H04W 16/02 Resource partitioning among network components, e.g. reuse partitioning
• CPC Class Codes: H04W 16/12 Fixed resource partitioning

Abstract

A method for allocating a plurality of spreading codes to a plurality of base stations is disclosed. After retrievably storing distances between each of the base stations and other base stations in a memory, the memory is searched for a longest distance of the distances. Based on a necessary spreading code difference and a longest spreading code shift corresponding to the longest distance, a spreading code spacing between spreading codes to be allocated to the base stations is determined. Then, spreading codes with the spreading code spacing are sequentially allocated to the base stations.

Claims

1. A method for allocating a plurality of spreading codes to a plurality of base stations, comprising:

a) retrievably storing distances between each of the base stations and other base stations in a memory;

b) searching the memory for a longest distance of the distances;

c) determining a spreading code spacing between spreading codes to be allocated to the base stations based on a necessary spreading code difference and a longest spreading code shift corresponding to the longest distance; and

d) sequentially allocating spreading codes with the spreading code spacing to the base stations.

2. A method according to claim 1, wherein the step c) comprises:

c-1) comparing the necessary spreading code difference with the longest spreading code shift; and

c-2) selecting a greater one of the necessary spreading code difference and the longest spreading code shift as the spreading code spacing.

3. A method according to claim 1, wherein the necessary spreading code difference is obtained by dividing a number of available spreading codes by a number of the base stations.

4. A method according to claim 1, wherein in the step d), the spreading codes with the spreading code spacing are allocated to the base stations such that two spreading codes with a smaller spacing are allocated respectively to two base stations which are located at a longer distant from each other.

5. A method according to claim 4, wherein the step d) comprises:

d-1) selecting a certain base station and a certain spreading code which is allocated to the certain base station;

d-2) selecting a base station located at a longest distance from a previously selected base station, excepting a further previously selected base station;

d-3) allocating a spreading code to a currently selected base station, wherein a currently allocated spreading code is shifted from a previously allocated spreading code by the spreading code spacing; and

d-4) repeating the steps d-2) and d-3) until the spreading codes have been allocated to all the base stations.

6. A method for allocating a plurality of spreading codes to a plurality of base stations in a mobile communications system, comprising:

at each of the base stations,

a) transmitting a predetermined spreading code on a pilot channel to other base stations;

b) detecting a spreading code shift from the predetermined spreading code received from each of the other base stations;

c) transmitting the spreading code shift to a controller of the mobile communications system;

at the controller,

d) retrievably storing spreading code shifts received from the base stations in a memory;

e) searching the memory for a longest spreading code shift;

f) determining a spreading code spacing between spreading codes to be allocated to the base stations based on a necessary spreading code difference and the longest spreading code shift; and

g) sequentially allocating spreading codes with the spreading code spacing to the base stations.

7. A method according to claim 6, wherein the step f) comprises:

f-1) comparing the necessary spreading code difference with the longest spreading code shift; and

f-2) selecting a greater one of the necessary spreading code difference and the longest spreading code shift as the spreading code spacing.

8. A method according to claim 6, wherein the necessary spreading code difference is obtained by dividing a number of available spreading codes by a number of the base stations.

9. A method according to claim 6, wherein in the step g), the spreading codes with the spreading code spacing are allocated to the base stations such that two spreading codes with a smaller spacing are allocated respectively to two base stations which are located at a longer distant from each other.

10. A method according to claim 9, wherein the step g) comprises:

g-1) calculating distances between each of the base stations and other base stations from the spreading code shifts stored in the memory;

g-2) selecting a certain base station and a certain spreading code which is allocated to the certain base station;

g-3) selecting a base station located at a longest distance from a previously selected base station, excepting a further previously selected base station;

g-4) allocating a spreading code to a currently selected base station, wherein a currently allocated spreading code is shifted from a previously allocated spreading code by the spreading code spacing; and

g-5) repeating the steps g-3) and g-4) until the spreading codes have been allocated to all the base stations.

11. A system for allocating a plurality of spreading codes to a plurality of base stations which are connected to a system controller,

each of the base stations comprising:

a test transceiver for transmitting and receiving a predetermined spreading code on a pilot channel to and from other base stations under control of the system controller;

a detector for detecting a spreading code shift from the predetermined spreading code received from each of the other base stations; and

a transmitter for transmitting the spreading code shift to the system controller, and

the system controller comprising;

a database for retrievably storing spreading code shifts received from the base stations;

a selector for searching the database for a longest spreading code shift; and

an allocation controller for determining a spreading code spacing between spreading codes to be allocated to the base stations based on a necessary spreading code difference and the longest spreading code shift, and for sequentially allocating spreading codes with the spreading code spacing to the base stations.

12. A system according to claim 11, wherein the allocation controller comprises:

a comparator for comparing the necessary spreading code difference with the longest spreading code shift; and

a selector for selecting a greater one of the necessary spreading code difference and the longest spreading code shift as the spreading code spacing.

13. A system according to claim 11, wherein the necessary spreading code difference is obtained by dividing a number of available spreading codes by a number of the base stations.

14. A system according to claim 11, wherein the allocation controller allocates the spreading codes with the spreading code spacing to the base stations such that two spreading codes with a smaller spacing are allocated respectively to two base stations which are located at a longer distant from each other.

15. A system according to claim 14, wherein the allocation controller performs spreading code allocation according to a program comprising the steps of:

a) calculating distances between each of the base stations and other base stations from the spreading code shifts stored in the memory;

b) selecting a certain base station and a certain spreading code which is allocated to the certain base station;

c) selecting a base station located at a longest distance from a previously selected base station, excepting a further previously selected base station;

d) allocating a spreading code to a currently selected base station, wherein a currently allocated spreading code is shifted from a previously allocated spreading code by the spreading code spacing; and

e) repeating the steps c) and d) until the spreading codes have been allocated to all the base stations.