Enhanced channel allocation among multiple carriers in a spread spectrum communications system

• US 6,611,506 B1
• Filed: 01/21/1999
• Issued: 08/26/2003
• Est. Priority Date: 01/21/1999
• Status: Expired due to Fees

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Jiang, Frances, Huang, Ching Yao, Koo, Yuen-Yin L.
• Primary Examiner(s): Chin, Vivian
• Assistant Examiner(s): NGUYEN, DUC M
• Application Number:
  US09/234,414
• Time in Patent Office: 1,678 Days
• Field of Search: 370/208, 370/209, 370/328, 370/329-333, 370/375, 370/342, 455/436, 455/439, 455/440, 455/443, 455/450, 455/452, 455/453, 455/456, 455/517, 455/524, 455/525
• US Class Current: 370/329
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 72/52 based on load

Abstract

A method for allocating traffic between multiple carriers in a wireless communications system measures loading on the communication system and selects an appropriate carrier from multiple carriers, based upon the loading measured. A first carrier is selected if the load on the first carrier is lower than or equal to the lowest loading of any supplemental carrier among the multiple carriers. If the load on the first carrier is not lower, then the subscriber may be assigned either to a supplemental carrier or the first carrier. The carrier assignment of the subscriber depends upon a predetermined threshold, which preferably considers actual or estimated differential interference between the first carrier and the supplemental carrier.

Claims

1. A method for allocating traffic between multiple carriers in a wireless communications system, the system including at least a first carrier within a first frequency spectrum and serving a geographic region and a second carrier within a second frequency spectrum different from the first frequency spectrum and serving the geographic region, the method comprising:

determining a threshold based upon differential electromagnetic interference measured within the second frequency spectrum relative to the first frequency spectrum in the geographic region, the threshold ranging from a maximum at a highest measured differential interference to a minimum at a lowest measured differential interference;

prohibiting inter-carrier hand-offs between the first carrier and the second carrier at the maximum; and

allowing inter-carrier hand-offs below the maximum.

2. The method according to claim 1, further comprising:

receiving a subscriber'"'"'s request for access to the communication system via the first carrier;

measuring a first loading level on the first carrier;

measuring a second loading level on the second carrier;

selecting one of the first and second carriers based on at least one of a comparison of the first loading level to the second loading level and on a comparison of a difference between the first and second loading levels to the threshold.

3. The method according to claim 2, wherein said selecting further includes:

selecting the first carrier to service a subscriber if the first loading level is equal to or less than the second loading level to prevent an inter-carrier handoff of the subscriber between the first carrier and the second carrier.

4. The method according to claim 2, wherein said selecting further includes:

selecting the second carrier to service a subscriber; and

permitting an inter-carrier hand-off,

if the difference between the first loading and the second loading is less than the threshold and the first loading level is greater than the second loading level.

5. The method according to claim 2, wherein said measuring the first and second loading levels further includes:

defining the first loading level as power usage of active subscribers on the first carrier divided by total power available for the first carrier; and

defining the second loading level as power usage of active subscribers on the second carrier divided by the total power available for the second carrier.

6. The method according to claim 2, further comprising:

determining whether the second carrier is a border carrier forming at least a portion of an outer periphery of a radio frequency coverage for the subscriber; and

adjusting the threshold prior to the selecting of the second carrier if said determining determines that the second carrier is a border carrier.

7. The method according to claim 6, wherein said adjusting further includes decreasing the threshold by at least one-half if said determining determines that the second carrier is a border carrier.

8. The method according to claim 2, further comprising:

determining whether the second carrier is classified as a border carrier being associated with an umbrella cell on the second frequency spectrum containing a plurality of cells on the first frequency spectrum; and

dividing a threshold precursor by a positive integer greater than one to yield the threshold for the selection of the second carrier.

9. A method for allocating traffic between multiple carriers in a wireless communications system, the system including at least a call-originating carrier within a first frequency spectrum and serving a geographic region and supplemental carriers within corresponding supplemental frequency spectrums different from the first frequency spectrum and serving the geographic region, the method comprising:

determining a threshold based upon differential electromagnetic interference measured within a supplemental frequency spectrums associated with one of the supplemental carriers relative to the first frequency spectrum in the geographic region, the threshold ranging from a maximum at a highest measured differential interference to a minimum at a lowest measured differential interference;

prohibiting inter-carrier hand-offs between the first carrier and a supplemental carrier at the maximum; and

allowing inter-carrier hand-offs below the maximum.

10. The method of claim 9, further comprising:

selecting one of the call-originating carrier and a transferee-candidate carrier from the supplemental carriers based on at least one of a comparison of the first loading level to each of the supplemental-carrier loading levels and on a comparison of a difference between the first loading and a lowest one of the supplemental-carrier loading levels to the threshold.

11. The method of claim 10, wherein said selecting further includes:

selecting the call-originating carrier to service the subscriber if the first loading level is equal to or less than each of the supplemental-carrier loading levels to prevent an inter-carrier handoff between the call-originating carrier and any one of the supplemental carriers.

12. The method of claim 10, wherein said selecting further includes:

selecting the transferee-candidate carrier from the supplemental carriers to service the subscriber; and

permitting an inter-carrier hand-off,

if a difference between the first loading and a lowest one of the supplemental-carrier loading levels is less than the threshold and the first loading level is greater than each of the supplemental-carrier loading levels.

13. The method according to claim 10, wherein said measuring of first carrier and supplemental-carrier loading levels further include:

defining the first loading level as power usage of active subscribers on the call-originating carrier divided by total power available for the call-originating carrier; and

defining each of the supplemental-carrier loading levels as power usage of active subscribers on the corresponding one of the supplemental carriers divided by the total power available for the corresponding supplemental carrier.

14. A method for allocating traffic between multiple carriers in a code division multiple access (CDMA) communications system, the method comprising:

receiving a subscriber'"'"'s request for access to the communication system via a call-originating carrier;

measuring a first loading level of the call-originating carrier within a first frequency spectrum and serving a geographic region;

measuring supplemental-carrier loading levels of supplemental carriers within corresponding frequency spectrums different from the first frequency spectrum and serving the geographic region;

determining a lowest carrier loading level from the supplemental-carrier loading levels and identifying a transferee-candidate carrier associated with the lowest carrier loading level;

identifying whether or not the transferee-candidate carrier is a border carrier with a radio frequency coverage contour extending outward beyond at least one cell operating on different frequency range than the border carrier; and

establishing a first weight factor if the transferee-candidate carrier is a border carrier and establishing a second weight factor if the transferee-candidate carrier is not a border carrier, the first weight factor being greater than the second weight factor such that the first weight factor inhibits inter-carrier handoffs to a greater extent than the second weight factor.

15. The method according to claim 14 further comprising the step of:

selecting the call-originating carrier to service the subscriber if the first loading level is equal to or less than the lowest carrier loading level to prevent an inter-carrier handoff between the call-originating carrier and the supplemental carriers.

16. The method according to claim 14 further comprising the steps of:

identifying whether the border carrier is associated with an umbrella cell containing other cells operating on different frequency ranges than the border carrier;

configuring the other cells to include an overhead channel selected from the group consisting of a control channel, an access channel, and a paging channel; and

configuring the border carrier to predominately provide traffic channels rather than the overhead channel.

17. The method according to claim 14 further comprising the step of:

selecting the transferee-candidate carrier from the supplemental carriers to service the subscriber and permitting an inter-carrier hand-off if a difference between the first loading and a lowest one of the supplemental-carrier loading levels is not less than the first weight factor for the transferee-candidate carrier not being a border carrier.

18. The method according to claim 14 further comprising the step of:

selecting the transferee-candidate carrier from the supplemental carriers to service the subscriber and permitting an inter-carrier hand-off if a difference between the first loading and a lowest one of the supplemental-carrier loading levels is not less than a second weight factor for the transferee-candidate carrier being a border carrier.

19. The method according to claim 14 further comprising the step of:

selecting the call-originating carrier to service the subscriber and inhibiting an inter-carrier hand-off if a difference between the first loading and a lowest one of the supplemental-carrier loading levels is less than the first weight factor for the transferee-candidate carrier not being a border carrier.

20. The method according to claim 14 further comprising the step of:

selecting the call-originating carrier to service the subscriber and inhibiting an inter-carrier hand-off if a difference between the first loading and a lowest one of the supplemental-carrier loading levels is less than the second weight factor for the transferee-candidate carrier being a border carrier.