Method and system for adapting a channel assignment plan to include shared frequency channels

• US 6,639,904 B1
• Filed: 12/15/1999
• Issued: 10/28/2003
• Est. Priority Date: 12/15/1999
• Status: Expired due to Term

• Current Assignee: GTE Wireless Incorporated (Verizon Communications Inc.)
• Original Assignee: Verizon Laboratories Incorporated (Verizon Communications Inc.)
• Inventors: Freeman, David F., Jennison, Alan B., Boyer, Pete A.
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): MEHRPOUR, NAGHMEH
• Application Number:
  US09/461,534
• Time in Patent Office: 1,413 Days
• Field of Search: 370/341, 370/348, 370/329, 370/332, 370/333, 370/328, 370/330, 370/344, 370/343, 455/446, 455/448, 455/450, 455/452, 455/453, 455/62, 455/63, 455/671, 455/675
• US Class Current: 370/329
• CPC Class Codes: H04W 16/06 Hybrid resource partitioning, e.g. channel borrowing
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 28/16 Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]

Abstract

In a cellular communication network (20) having a channel assignment plan (28) that distinguishes frequency channels (34) assigned to a plurality of cells (24), a method (58) and system (46) adapt the channel assignment plan (28) during network planning to include shared frequency channels (45). Borrower cells (84) are identified in response to a deficiency value (36) indicating a shortage in a quantity of the frequency channels (34) assigned to the borrower cells (84). Donor cells (95) are selected from the cells (24) in response to a load factor (38) for each of the cells (24), the load factor (38) indicating the number of frequency channels (34) already being shared by the cell (24). Candidate frequency channels (34) that may be shared are evaluated against predetermined channel sharing constraints, such as frequency separation constraints (156, 158), co-channel carrier-to-interference C/I constraints (232, and adjacent channel C/I) constraints (280).

Claims

1. In a cellular communication network having a channel assignment plan that distinguishes channels assigned to a plurality of cells, a method for adapting said channel assignment plan to include shared channels comprising:

identifying a borrower cell from said plurality of cells, said borrower cell being assigned a first subset of said channels, said first subset having a deficiency in a quantity of said channels assigned to said borrower cell;

selecting a donor cell from said plurality of cells in response to a load factor for said donor cell, said donor cell being assigned a second subset of said channels;

choosing a candidate channel from said second subset;

determining a quality measure for said candidate channel; and

designating said candidate channel as one of said shared channels in said channel assignment plan when said quality measure exceeds a channel sharing constraint.

2. A method as claimed in claim 1 wherein said identifying operation comprises:

generating a deficiency value for each of said cells;

detecting candidate borrower cells from said plurality of cells in response to said generated deficiency values; and

specifying a needier one of said candidate borrower cells to be said borrower cell, wherein said deficiency value associated with said needier borrower cell indicates that said needier borrower cell as has a greater deficiency in said quantity of said assigned frequency channels than remaining ones of said candidate borrower cells.

3. A method as claimed in claim 1 further comprising:

generating a deficiency value for each of said cells;

detecting candidate borrower cells from said plurality of cells in response to said generated deficiency values; and

performing said selecting, choosing, determining, and designating operations for each of said candidate borrower cells.

4. A method as claimed in claim 1 wherein said selecting operation comprises:

ascertaining said load factor for said cells, said load factor representing those of said channels assigned to a corresponding one of said cells that are previously designated as said shared channels; and

specifying a better one of said cells to be said donor cell, said better one of said cells exhibiting said load factor that is less than said load factors for the remaining ones of said cells.

5. A method as claimed in claim 1 wherein said selecting operation comprises:

ascertaining a first load factor for a first candidate donor cell from said plurality of cells;

ascertaining a second load factor for a second candidate donor cell from said plurality of cells, said first and second load factors representing those of said channels assigned to corresponding ones of said first and second candidate donor cells that are previously designated as said shared channels;

when said first and said second load factors are equivalent, computing conditional carrier-to-interference (C/I) ratios for said first and second candidate donor cells; and

specifying a better one of said first and second candidate donor cells to be said donor cell, said better donor cell exhibiting a first one of said conditional C/I ratios that is greater than a second one of said conditional C/I ratios for the other of said first and second candidate donor cells.

6. A method as claimed in claim 1 wherein:

each of said channels of said second subset exhibits one of an available status and an unavailable status, said unavailable status indicating those of said channels of said second subset that are designated as said shared channels; and

said choosing operation picks one of said channels exhibiting said available status.

7. A method as claimed in claim 1 wherein said determining operation comprises:

defining said channel sharing constraint as a frequency separation threshold;

identifying neighbor cells from said plurality of cells, said neighbor cells being proximate said borrower cell;

for each of said neighbor cells, determining a frequency separation between said candidate channel and said channels assigned to said neighbor cell; and

verifying said frequency separation threshold is exceeded between said candidate channel and each of said channels assigned to said neighbor cell.

8. A method as claimed in claim 7 further comprising:

distinguishing adjacent neighbor cells as those of said neighbor cells that are adjacent said borrower cell; and

defining said frequency separation threshold for said adjacent neighbor cells as being a width of one of said channels.

9. A method as claimed in claim 8 further comprising:

distinguishing common neighbor cells as those of said neighbor cells that are removed from said borrower cell by one of said adjacent neighbor cells; and

determining said frequency separation threshold for said common neighbor cells is violated when said candidate channel is equivalent to one of said channels assigned to one of said common neighbor cells.

10. A method as claimed in claim 1 wherein said determining operation comprises:

a) defining said channel sharing constraint as a co-channel carrier-to-interference (C/I) ratio threshold;

b) determining a portion of said plurality of cells that are assigned said candidate channel;

c) computing a co-channel C/I ratio value for said borrower cell in response to said operation b); and

d) verifying said co-channel C/I ratio value for said borrower cell exceeds said co-channel C/I ratio threshold.

11. A method as claimed in claim 10 wherein a first cell and a second cell of said portion of said cells share said candidate channel, and said computing operation comprises determining an interference power responsive to a transmission of said candidate channel from one of said first and second cells.

12. A method as claimed in claim 1 wherein said determining operation comprises:

a) defining said channel sharing constraint as an adjacent channel C/I ratio threshold;

b) determining a portion of said plurality of cells that are assigned an adjacent channel, said adjacent channel being adjacent to said candidate channel;

c) computing an adjacent C/I ratio value for said borrower cell in response to said operation b); and

d) verifying said adjacent C/I ratio value for said borrower cell exceeds said adjacent C/I ratio threshold.

13. A method as claimed in claim 12 wherein said determining operation further comprises:

identifying a second portion of said plurality of cells that are assigned said second adjacent channel;

computing a second adjacent C/I ratio for said borrower cell in response to said identifying operation; and

verifying said second adjacent C/I ratio value for said borrower cell exceeds said adjacent C/I ratio threshold.

14. A method as claimed in claim 12 wherein a first cell and a second cell of said portion of said cells share said adjacent channel, and said method further comprises computing an interference power responsive to a transmission of said adjacent channel from one of said first and second cells.

15. A method as claimed in claim 1 further comprising associating said one of said shared channels with said borrower cell and said donor cell in said channel assignment plan.

16. A method as claimed in claim 15 further comprising indicating in said channel assignment plan that only one of said borrower and said donor cells utilize said one shared channel during a time period.

17. A method as claimed in claim 1 further comprising:

increasing said load factor for said donor cell in response to said designating step, said load factor representing those of said channels of said second subset that are previously designated as said shared channels;

decreasing said deficiency of said quantity of said channels assigned to said borrower cell; and

repeating said selecting, choosing, determining, and designating operations in response to identification of a second borrower cell from said plurality of cells.

18. A method as claimed in claim 1 further comprising:

determining when said quality measure for said candidate channel fails to meet said channel sharing constraint;

repeating said choosing and determining operations for subsequent ones of said channels of said second subset; and

when one of said subsequent channels meets said channel sharing constraint, designating said one subsequent channel as one of said shared channels.

19. A method as claimed in claim 1 wherein said donor cell is a first donor cell, and said method further comprises:

determining when said candidate channel fails to meet said channel sharing constraint;

repeating said choosing and evaluating operations for subsequent ones of said channels of said second subset;

when all of said subsequent channels violate said channel sharing constraint, selecting a second donor cell from said plurality of cells; and

performing said choosing, determining, and designating operations in response to selection of said second donor cell.

20. A system for adapting a channel assignment plan for a cellular communication network to include shared frequency channels, said channel assignment plan distinguishing frequency channels assigned to a plurality of cells, and said system comprising:

an input element for receiving said channel assignment plan;

a memory element in communication with said input element for storing said channel assignment plan;

a borrower cell identifier, in communication with said memory element, for identifying a borrower cell from said plurality of cells in response to said channel assignment plan, said borrower cell identifier including;

a detector for detecting candidate borrower cells from said plurality of cells, each of said candidate borrower cells being assigned subsets of said frequency channels, each of said subsets exhibiting deficiencies in a quantity of said frequency channels assigned to corresponding ones of said candidate borrower cells; and

a needier cell selector for specifying a first one of said candidate borrower cells to be said borrower cell, said first borrower cell having a greater deficiency in said quantity of said frequency channels assigned to said needier borrower cell than remaining ones of said candidate borrower cells;

a donor cell selector, in communication with said memory element, for selecting a donor cell from said plurality of cells, said donor cell selector including;

a load factor determiner for ascertaining a load factor for each of said cells from said plurality of cells excluding said identified borrower cell, said load factor representing those of said frequency channels assigned to a corresponding one of said cells that are previously designated as said shared frequency channels; and

a better cell selector for specifying a first one of said cells to be said donor cell, said first cell exhibiting said load factor that is less than said load factors for the remaining ones of said cells;

a channel selector for choosing a candidate frequency channel from a subset of said frequency channels assigned to said donor cell;

a channel evaluator for determining a quality measure for said candidate frequency channel; and

channel designator for designating said candidate frequency channel as one of said shared frequency channels in said channel assignment plan when quality measure exceeds a channel sharing constraint.

21. A system as claimed in claim 20 further comprising a correlator, in communication with said memory element, for associating said one of said shared frequency channels with said borrower cell and said donor cell in said channel assignment plan.

22. A system as claimed in claim 20 further comprising:

a load adjuster, in communication with said frequency designator, for increasing said load factor for said donor cell in response to the designation of said candidate frequency channel as one of said shared frequency channels; and

a deficiency adjuster, in communication with said frequency designator, for decreasing said deficiency in said quantity of said frequency channels assigned to said borrower cell in response to the designation of said candidate frequency channel as one of said shared frequency channels.

23. In a cellular communication network having a channel assignment plan that distinguishes frequency channels assigned to a plurality of cells, a method for adapting said channel assignment plan to include shared frequency channels comprising the steps of:

a) identifying a borrower cell from said plurality of cells, said borrower cell being assigned a first subset of said frequency channels, said first subset having a deficiency in a quantity of said frequency channels assigned to said borrower cell;

b) selecting a donor cell from said plurality of cells in response to a load factor for said donor cell, said donor cell being assigned a second subset of said frequency channels;

c) verifying frequency separations between said candidate frequency channel and each of said frequency channels of said second subset exceed a frequency separation threshold;

d) when each of said frequency separations exceed said frequency separation threshold, verifying a co-channel carrier-to-interference (C/I) ratio value for said borrower cell exceeds a co-channel C/I ratio threshold;

e) when said co-channel C/I ratio value exceeds said co-channel C/I ratio threshold, verifying an adjacent channel C/I ratio value for said borrower cell exceeds an adjacent channel C/I ratio threshold; and

f) designating said candidate frequency channel as one of said shared frequency channels in said channel assignment plan in response to said step e).

24. A method as claimed in claim 23 further comprising the step of preventing said candidate frequency channel from being one of said shared frequency channels when said candidate frequency channel violates one of said frequency separation threshold, said co-channel C/I ratio threshold, and said adjacent C/I ratio threshold.

25. A method as claimed in claim 23 further comprising the step of repeating said operations c)-f) for subsequent ones of said frequency channels of said second subset when said candidate frequency channel violates one of said frequency separation threshold, said co-channel C/I ratio threshold, and said adjacent C/I ratio threshold.