Method and system for determining a neighbor list for a code division multiple access (CDMA) sector

• US 6,360,098 B1
• Filed: 03/15/2000
• Issued: 03/19/2002
• Est. Priority Date: 03/15/2000
• Status: Expired due to Term

• Current Assignee: Verizon Laboratories Incorporated (Verizon Communications Inc.)
• Original Assignee: Verizon Laboratories Incorporated (Verizon Communications Inc.)
• Inventors: OʼByrne, Vincent, Ganesh, Rajamani
• Primary Examiner(s): Kincaid, Lester G.
• Application Number:
  US09/525,356
• Time in Patent Office: 734 Days
• Field of Search: 455/436-442, 455/450-452, 455/525, 455/67.1, 455/62, 455/63, 455/65, 370/331-333
• US Class Current: 455/436
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection

Abstract

In a code division multiple access (CDMA) radio communications network (20) having a plurality of cells (24) subdivided into sectors (26), a computer based method (36) and a computing system (34) determine a neighbor list (56) for a selected one of the sectors (26). The sector (26) is subdivided into a plurality of locations (64). For each location (64), a primary pilot channel (88) exhibiting a primary signal quality (92) is distinguished. Secondary pilot channels (120) are identified exhibiting secondary signal qualities (119) within a signal quality threshold window (108) of the primary signal quality (92) of the primary pilot channel. The primary and secondary pilot channels (88 and 120) are included in the neighbor list (56) for the sector (26) as candidate handoff channels (98). The candidate handoff channels (98) are arranged in a ranked order in the neighbor list (56) such that those candidate handoff channels (98) having a higher rank have a greater likelihood for inclusion in a neighbor set of a mobile station (32) residing in the serving area of the sector (26).

Claims

1. A computer-based method of determining a neighbor list for a code division multiple access (CDMA) sector in a radio communications network, said network including neighbor CDMA sectors proximate said CDMA sector, and said method comprising:

detecting, at locations in said CDMA sector, neighbor broadcast channels transmitted from said neighbor CDMA sectors;

distinguishing, for each of said locations, a first broadcast channel from said neighbor broadcast channels detected at said each location;

establishing, for said each location, a signal quality threshold window in response to signal quality of said first broadcast channel;

identifying, for said each location, second broadcast channels from said neighbor broadcast channels, each of said second broadcast channels being identified when signal quality of said each second broadcast channel is within said signal quality threshold window; and

including said first and said second broadcast channels as candidate handoff channels in said neighbor list for said CDMA sector.

2. A computer-based method as claimed in claim 1 wherein said CDMA sector includes a plurality of said locations, and said method further comprises performing said detecting, distinguishing, establishing, identifying, and including operations for each of said locations in said CDMA sector.

3. A computer-based method as claimed in claim 1 wherein said distinguishing operation includes:

determining signal quality for each of said detected neighbor broadcast channels; and

choosing one of said neighbor broadcast channels having a greatest signal quality as said first broadcast channel.

4. A computer-based method as claimed in claim 1 further comprising setting a maximum value of said signal quality threshold window to be substantially equivalent to said signal quality of said first broadcast channel.

5. A computer-based method as claimed in claim 1 wherein said neighbor list is utilized to form a neighbor set of said candidate handoff channels for a mobile station residing in said CDMA sector, and said method further comprises arranging said candidate handoff channels in said neighbor list in a ranked order, said ranked order characterizing a likelihood of said candidate handoff channels being selected for inclusion in said neighbor set.

6. A computer-based method as claimed in claim 5 wherein said arranging operation comprises:

ascertaining detection occurrences for said candidate handoff channels, said detection occurrences being responsive to a quantity of said locations at which corresponding ones of said candidate handoff channels are one of said first and said second broadcast channels; and

setting said ranked order such that those of said candidate handoff channels having greater ones of said detection occurrences than others of said candidate handoff channels have a greater likelihood of being selected for inclusion in said neighbor set.

7. A computer-based method as claimed in claim 6 wherein said ascertaining operation comprises:

maintaining detection occurrence counters for each of said candidate handoff channels; and

incrementing a value in one of said detection occurrence counters at each instance of distinguishing a corresponding one of said neighbor broadcast channels as said first broadcast channel and at each instance of identifying said corresponding one of said neighbor broadcast channels as one of said second broadcast channels.

8. A computer-based method as claimed in claim 5 wherein said arranging operation comprises:

ascertaining two-way handoff occurrences for said candidate handoff channels, said two-way handoff occurrences being responsive to a quantity of said locations at which corresponding ones of said candidate handoff channels are eligible for two-way handoff; and

setting said ranked order such that those of said candidate handoff channels having greater ones of said two-way handoff occurrences than others of said candidate handoff channels have a greater likelihood of being selected for inclusion in said neighbor set.

9. A computer-based method as claimed in claim 8 wherein said ascertaining operation comprises:

maintaining two-way handoff counters for each of said candidate handoff channels;

identifying those of said locations at which said detected neighbor broadcast channels include said first broadcast channel and one of said second broadcast channels, said first broadcast channel and said one second broadcast channel forming a channel pair eligible for said two-way handoff;

incrementing a first one of said two-way handoff counters associated with said first broadcast channel of said channel pair; and

incrementing a second one of said two-way handoff counters associated with said second broadcast channel of said channel pair.

10. A computer-based method as claimed in claim 5 wherein said arranging operation comprises:

ascertaining traffic carried values for said candidate handoff channels, said traffic carried values being responsive to a quantity of said locations at which corresponding ones of said candidate handoff channels are eligible for one of two-way handoff and three-way handoff; and

setting said ranked order such that those of said candidate handoff channels having greater ones of said traffic carried values than others of said candidate handoff channels have a greater likelihood of being selected for inclusion in said neighbor set.

11. A computer-based method as claimed in claim 1 wherein said CDMA sector is a first CDMA sector, one of said neighbor CDMA sectors is a second CDMA sector, and said method further comprises including a broadcast channel transmitted from said first CDMA sector as one of said candidate handoff channels in a second neighbor list for said second CDMA sector when a first one of said candidate handoff channels in said neighbor list for said first CDMA sector is transmitted from said second CDMA sector.

12. A computer-based method as claimed in claim 1 wherein said broadcast channels are pilot channels.

13. A computer-based method as claimed in claim 1 wherein said signal quality corresponds to signal strength relative to interference.

14. A computer-readable storage medium containing executable code for instructing a computer to create a neighbor list for a code division multiple access (CDMA) sector in a radio communications network, said radio communications network including neighbor sectors proximate said CDMA sector, said executable code instructing said computer to perform operations comprising:

detecting, at locations in said CDMA sector, neighbor pilot channels transmitted from said neighbor CDMA sectors;

determining signal quality for each of said detected neighbor pilot channels;

distinguishing, for each of said locations, a primary pilot channel from said neighbor pilot channels detected at said each location, said primary pilot channel being one of said neighbor pilot channels having a greatest signal quality;

establishing, for said each location, a signal quality threshold window in response to said signal quality of said primary pilot channel;

identifying, for said each location, secondary pilot channels from said neighbor pilot channels, each of said secondary pilot channels being identified when signal quality of said each secondary pilot channel is within said signal quality threshold window;

including said primary and said secondary pilot channels as candidate handoff channels in said neighbor list for said CDMA sector; and

arranging said candidate handoff channels in said neighbor list in a ranked order, said ranked order establishing a likelihood of said candidate handoff channels being selected for inclusion in a neighbor set for a mobile station residing said CDMA sector.

15. A computer-readable storage medium as claimed in claim 14 wherein said executable code instructs said computer to perform a further operation of setting a maximum value of said signal quality threshold window to be substantially equivalent to said signal quality of said primary pilot channel.

16. A computer-readable storage medium as claimed in claim 14 wherein said executable code instructs said computer to perform further operations comprising:

ascertaining detection occurrences for said candidate handoff channels, said detection occurrences being responsive to a quantity of said locations at which corresponding ones of said candidate handoff channels are one of said primary and said secondary pilot channels; and

setting said ranked order such that those of said candidate handoff channels having greater ones of said detection occurrences than others of said candidate handoff channels have a greater likelihood of being selected for inclusion in said neighbor set.

17. A computer-readable storage medium as claimed in claim 14 wherein said executable code instructs said computer to perform further operations comprising:

ascertaining two-way handoff occurrences for said candidate handoff channels, said two-way handoff occurrences being responsive to a quantity of said locations at which corresponding ones of said candidate handoff channels are eligible for two-way handoff; and

setting said ranked order such that those of said candidate handoff channels having greater ones of said two-way handoff occurrences than others of said candidate handoff channels have a greater likelihood of being selected for inclusion in said neighbor set.

18. A computer-readable storage medium as claimed in claim 14 wherein said executable code instructs said computer to perform further operations comprising:

ascertaining traffic carried values for said candidate handoff channels, said traffic carried values being responsive to a quantity of said locations at which corresponding ones of said candidate handoff channels are eligible for one of two-way handoff and three-way handoff; and

setting said ranked order such that those of said candidate handoff channels having greater ones of said traffic carried values than others of said candidate handoff channels have a greater likelihood of being selected for inclusion in said neighbor set.

19. A computing system for determining neighbor lists for each of a plurality of code division multiple access (CDMA) sectors in a radio communication network, said neighbor lists being utilized to form neighbor sets of candidate handoff channels for a mobile station residing in one of said CDMA sectors, said computing system comprising:

an input element for receiving a pilot channel detection database for said radio communications network, said database including a plurality of locations for each of said CDMA sectors and pilot channels transmitted from said CDMA sectors and detected at corresponding ones of said locations;

a processor, in communication with said input element, for creating said neighbor lists of said candidate handoff channels from said pilot channels in said pilot channel detection database, one each of said neighbor lists corresponding to one each of said CDMA sectors, wherein for each of said locations in a first one of said CDMA sectors, said processor performs operations comprising;

determining when said pilot channels detected at said each location are neighbor pilot channels, said neighbor pilot channels being transmitted from said CDMA sectors proximate said first CDMA sector;

when said pilot channels detected at said each location are said neighbor pilot channels, distinguishing a first one of said neighbor pilot channels as a primary pilot channel;

establishing a signal quality threshold window having a maximum value substantially equivalent to a primary signal quality of said primary pilot channel;

when others of said neighbor pilot channels detected at said each location have secondary signal qualities within said signal quality threshold window, identifying said others of said neighbor pilot channels as secondary pilot channels; and

including said primary and said secondary pilot channels as said candidate handoff channels in a first neighbor list for said first CDMA sector; and

a memory element, in communication with said processor, for storing said neighbor lists for said CDMA sectors, said candidate handoff channels in each of said neighbor lists being arranged in a ranked order, said ranked order establishing a likelihood for said neighbor pilot channels to be selected for inclusion in said neighbor sets.

20. A computing system as claimed in claim 19 wherein said processor arranges said candidate handoff channels in said ranked order according to detection occurrences of said candidate handoff channels, each of said detection occurrences being responsive to a quantity of said locations in said first CDMA sector at which an associated one of said candidate handoff channels is one of said primary and said secondary pilot channels.

21. A computing system as claimed in claim 19 wherein said processor arranges said candidate handoff channels in said ranked order according to two-way handoff occurrences of said candidate handoff channels, each of said two-way handoff occurrences being responsive to a quantity of said locations in said first CDMA sector at which an associated one of said candidate handoff channels is eligible for two-way handoff.

22. A computing system as claimed in claim 19 wherein said processor includes a pilot channel transmitted from said first CDMA sector as one of said candidate handoff channels in a second neighbor list for a second one of said second CDMA sectors when a first one of said candidate handoff channels in said neighbor list for said first CDMA sector is transmitted from said second CDMA sector.