Method for partitioning mobile stations of a wireless network between an overlay and an underlay

• US 6,405,046 B1
• Filed: 08/06/1999
• Issued: 06/11/2002
• Est. Priority Date: 10/08/1998
• Status: Expired due to Term

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Whiting, Philip Alfred, Kumaran, Krishnan
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): SOBUTKA, PHILIP
• Application Number:
  US09/369,687
• Time in Patent Office: 1,040 Days
• Field of Search: 455/444, 455/443, 455/446, 455/449, 455/450, 455/451, 455/452, 455/453, 455/422, 455/509, 455/524
• US Class Current: 455/453
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 16/32 Hierarchical cell structures
• CPC Class Codes: H04W 36/04 Reselecting a cell layer in multi-layered cells

Abstract

A method is described for partitioning the mobile stations occupying each of a plurality of cells of a wireless communication network between an overlay and an underlay. Within each cell, each of that cell'"'"'s mobile stations is assigned to the overlay if the mobile station'"'"'s corresponding path loss exceeds a path-loss threshold, and to the underlay if its corresponding path loss lies below the path-loss threshold. The path-loss threshold for each cell is determined according to a procedure that seeks to drive network capacity up while satisfying a rule that relates to intercell interference.

Claims

1. A method for partitioning the mobile stations occupying each of a plurality of cells of a wireless communication network between an overlay and an underlay, wherein:

(i) each cell has a base station,

(ii) within each cell there is a path loss between the base station and each mobile station of that cell;

(iii) a plurality of communication channels is available to the network; and

(iv) said channels are allocable as overlay channels or underlay channels, each possible allocation of all said channels to be referred to as a channel split;

the method comprising;

determining a path-loss threshold for each cell according to a procedure that seeks to drive network capacity up while satisfying a rule that relates to intercell interference;

repeating the threshold-determination procedure for each of a plurality of possible channel splits, thereby to determine that channel split which yields the greatest network capacity while satisfying the rule that relates to intercell interference;

within each cell, assigning each of that cell'"'"'s mobile stations to the overlay if the mobile station'"'"'s corresponding path loss exceeds the pertinent path-loss threshold, and to the underlay if its corresponding path loss lies below the pertinent path-loss threshold; and

allocating the plurality of communication channels according to the channel split that has been determined to yield the greatest network capacity while satisfying the rule that relates to intercell interference.

2. The method of claim 1, wherein:

the plurality of channel splits, over which the threshold-determination procedure is repeated, is a pruned set of channel splits; and

the pruned set comprises only those channel splits that satisfy a rule that relates to call blocking and a rule that relates to intercell interference.

3. The method of claim 2, wherein the call-blocking rule requires that there be enough underlay channels to permit the average rate of call blocking to fall below a threshold for some partition of the mobile stations between the overlay and the underlay.

4. The method of claim 3, wherein:

the intercell-interference rule relates to a requirement that for a particular partition of mobile stations between the overlay and the underlay in each cell, the risk that the total interference in any cell exceeds a threshold β

must not exceed a further threshold γ

.

5. The method of claim 4, wherein:

the threshold-determination procedure is carried out using data that relate an average rate of call-blocking in each cell to the proportion of that cell'"'"'s traffic that can be supported within the underlay, said proportion to be referred to as the absorption, and using data that relate the absorption in each cell to the corresponding path-loss threshold; and

the particular partition to which the intercell-interference rule relates is determined by the smallest absorption for which a target level of call-blocking performance can be met.

6. A method for partitioning the mobile stations occupying each of a plurality of cells of a wireless communication network between an overlay and an underlay, wherein:

(i) each cell has a base station, and

(ii) within each cell there is a path loss between the base station and each mobile station of that cell;

the method comprising;

within each cell, assigning each of that cell'"'"'s mobile stations to the overlay if the mobile station'"'"'s corresponding path loss exceeds a path-loss threshold, and to the underlay if its corresponding path loss lies below the path-loss threshold;

wherein;

the path-loss threshold for each cell is determined according to a procedure that seeks to drive network capacity up while satisfying a rule that relates to intercell interference; and

the threshold-determination procedure is an optimization procedure, and it is carried out using;

data that relate an average rate of call-blocking in each cell to the proportion of that cell'"'"'s traffic that can be supported within the underlay, said proportion to be referred to as the absorption; and

data that relate the absorption in each cell to the corresponding path-loss threshold.

7. The method of claim 6, wherein the optimization procedure is carried out subject to a constraint that each cell'"'"'s path-loss threshold must lie within an operating range.

8. The method of claim 7, wherein, for each cell:

the operating range has a lower end corresponding to an absorption that is just sufficient for the average rate of call blocking to fall below a target level; and

the operating range has an upper end above which the average rate of call blocking exhibits reduced sensitivity to absorption.

9. The method of claim 8, wherein the data that relate the average rate of call blocking in each cell to the absorption represent a linear relationship over the operating range.

10. A method for partitioning the mobile stations occupying each of a plurality of cells of a wireless communication network between an overlay and an underlay, wherein:

(i) each cell has a base station, and

(ii) within each cell there is a path loss between the base station and each mobile station of that cell;

the method comprising;

within each cell, assigning each of that cell'"'"'s mobile stations to the overlay if the mobile station'"'"'s corresponding path loss exceeds a path-loss threshold, and to the underlay if its corresponding path loss lies below the path-loss threshold;

wherein

the path-loss threshold for each cell is determined according to a procedure that seeks to drive network capacity up while satisfying a rule that relates to intercell interference;

the threshold-determination procedure is a procedure for optimizing the value of an objective function related to the call-blocking performance of the network;

the optimization procedure is carried out using data that relate an average rate of call-blocking in each cell to the proportion of that cell'"'"'s traffic that can be supported within the underlay, said proportion to be referred to as the absorption;

the optimization procedure is carried out using data that relate the absorption in each cell to the corresponding path-loss threshold;

the absorption in each cell has an operating range having a minimum value just sufficient for the average rate of call blocking to fall below a target level, and a maximum value above which the average rate of call blocking exhibits reduced sensitivity to absorption;

the optimization procedure is carried out subject to a constraint that the absorption in each cell must lie within its operating range; and

the optimization procedure is carried out subject to a bound on the risk that total intercell interference in any cell exceeds an interference threshold.

11. The method of claim 10, wherein:

the optimization procedure results in a solution comprising an optimized path-loss threshold for each cell;

corresponding to the solution, there is a respective, predicted level of call-blocking performance for each cell; and

a constraint is imposed that prevents the optimization procedure from seeking unrealistic solutions that exceed a best-case level of blocking performance for each cell.

12. The method of claim 11, wherein the optimization procedure comprises:

carrying out, for each cell, an optimization procedure having relaxed constraints, thereby to obtain the corresponding best-case level of blocking performance for that cell; and

carrying out a network-wide optimization procedure by solving a linear program subject to said constraints on the absorption operating range, interference risk, and the cell blocking performance.

13. The method of claim 11, wherein:

for each given cell, a corresponding clique is defined as the set of neighboring cells that are co-channel interferers of the given cell;

for each given cell, the optimization procedure having relaxed constraints comprises optimizing an objective function that relates to the blocking performance only of cells in the clique of the given cell; and

for each given cell, said optimization procedure is carried out subject to a bound on the risk that total intercell interference in the given cell, from its corresponding clique, exceeds an interference threshold.