Cellular network handoff modeling

• US 7,181,221 B1
• Filed: 09/26/2003
• Issued: 02/20/2007
• Est. Priority Date: 09/26/2002
• Status: Expired due to Fees

• Current Assignee: George Mason Intellectual Properties, Inc.
• Original Assignee: George Mason Intellectual Properties, Inc.
• Inventors: Leu, Alexe E., Mark, Brian L.
• Primary Examiner(s): Urban; Edward F.
• Assistant Examiner(s): Jackson; Blane J.
• Application Number:
  US10/670,467
• Time in Patent Office: 1,243 Days
• Field of Search: 455436-444, 370331-334
• US Class Current: 455/436
• CPC Class Codes: H04W 16/18 Network planning tools
• CPC Class Codes: H04W 36/24 Reselection being triggered by specific parameters
• CPC Class Codes: H04W 36/249 according to timing information

Abstract

Disclosed is a system for evaluating the performance of cellular network handoff decisions. One embodiment of this system includes the steps of: creating a reference cellular network description; creating reduced geometric structures from the reference cellular network description; representing a general trajectory for a mobile unit in the reference cellular network description; approximating the general trajectory with a piecewise path having a multitude of handoff decision points; selecting a handoff mechanism; selecting handoff parameters; creating a discrete-time formulation characterizing handoff behaviors; and calculating at least one handoff performance metric. The handoff performance metrics may include assignment probabilities; handoff probabilities; a mean number of handoff value; a crossover point; and overall signaling load incurred by a handoff mechanism.

Claims

1. A method for evaluating the performance of cellular network handoff decisions comprising the steps of:

a) creating a reference cellular network description, said reference cellular network description describing;

i) a cellular network geometry;

ii) a signal propagation description;

iii) at least two base stations, each of said at least two base stations having;

(1) a location within said cellular network geometry; and

(2) a pilot signal having a pilot signal strength; and

iv) at least one mobile unit capable of;

(1) moving along a trajectory; and

(2) sampling said pilot signal strength; and

b) creating reduced geometric structures from said reference cellular network description;

c) representing a general trajectory for said mobile unit in said reference cellular network description;

d) approximating said general trajectory with a piecewise path having a multitude of handoff decision points;

e) selecting a handoff mechanism;

f) selecting handoff parameters;

g) creating a discrete-time formulation characterizing handoff behaviors; and

h) calculating at least one handoff performance metric along at least one said handoff decision point.

2. A method according to claim 1, wherein at least one of said at least one handoff performance metric includes:

a) an assignment probability;

b) a handoff probability;

c) a mean number of handoff value;

d) a crossover point;

e) an outage probability;

f) a macrodiversity degree; and

g) an overall signaling load incurred by said handoff mechanism.

3. A method according to claim 1, wherein said cellular network geometry includes at least one of the following:

a) a hexagonal cell pattern;

b) a diamond cell pattern;

c) a square cell pattern;

d) a rhombus cell pattern; and

e) a star pattern.

4. A method according to claim 1, wherein said cellular network geometry includes cells mapped into at least one reduced geometric structure.

5. A method according to claim 4, wherein said cellular network geometry includes reduced geometric structures mapped into at least one minimum geometric structure.

6. A method according to claim 1, wherein said signal propagation description includes at least one of the following components:

a) a path loss component;

b) a shadow fading component; and

c) a fast fading component.

7. A method according to claim 1, wherein said piecewise path is a piecewise linear path.

8. A method according to claim 1, wherein said step of selecting a handoff mechanism includes selecting a hard handoff mechanism.

9. A method according to claim 1, wherein said step of selecting a handoff mechanism includes selecting a soft handoff mechanism.

10. A method according to claim 1, wherein said step of selecting a handoff mechanism considers at least one of the following:

a) assignment regions;

b) relative pilot signal strengths; and

c) relative processed signal strengths.

11. A method according to claim 1, wherein said handoff parameters include at least one of the following:

a) a hysteresis value;

b) a drop timer value;

c) an averaging parameter; and

d) a handoff decision interval.

12. A method according to claim 1, wherein said step of calculating at least one handoff performance metric along at least one said handoff decision point uses a recursive procedure.

13. A cellular network handoff modeler comprising:

a) a reference cellular network description generator, capable of generating a reference cellular network description, said reference cellular network description describing;

i) a cellular network geometry;

ii) a signal propagation description;

iii) at least two base stations, each of said at least two base stations having;

(1) a location within said cellular network geometry; and

(2) a pilot signal having a pilot signal strength; and

iv) at least one mobile unit capable of;

(1) moving along a trajectory; and

(2) sampling said pilot signal strength; and

b) a reduced geometric structure creator, capable of creating reduced geometric structures from said reference cellular network description;

c) a general trajectory generator, capable of representing a general trajectory for said mobile unit in said reference cellular network description;

d) a piecewise path creator capable of approximating said general trajectory with a piecewise path having a multitude of handoff decision points;

e) a handoff mechanism selector;

f) handoff parameters selector;

g) a discrete-time formulation creator capable of characterizing handoff behaviors; and

h) a handoff performance metric calculator capable of calculating at least one handoff performance metric along at least one said handoff decision point.

14. A method according to claim 13, wherein at least one of said at least one handoff performance metric includes:

a) an assignment probability;

b) a handoff probability;

c) a mean number of handoff value;

d) a crossover point;

e) an outage probability;

f) a macrodiversity degree; and

g) an overall signaling load incurred by said handoff mechanism.

15. A method according to claim 13, wherein said cellular network geometry includes at least one of the following:

a) a hexagonal cell pattern;

b) a diamond cell pattern;

c) a square cell pattern;

d) a rhombus cell pattern; and

e) a star pattern.

16. A method according to claim 13, wherein said cellular network geometry includes cells mapped into at least one reduced geometric structure.

17. A method according to claim 16, wherein said cellular network geometry includes reduced geometric structures mapped into at least one minimum geometric structure.

18. A method according to claim 13, wherein said signal propagation description includes at least one of the following components:

a) a path loss component;

b) a shadow fading component; and

c) a fast fading component.

19. A method according to claim 13, wherein said piecewise path is a piecewise linear path.

20. A method according to claim 13, wherein said handoff mechanism selector is capable of selecting a hard handoff mechanism.

21. A method according to claim 13, wherein said handoff mechanism selector is capable of selecting a soft handoff mechanism.

22. A method according to claim 13, wherein said handoff mechanism selector considers at least one of the following:

a) assignment regions;

b) relative pilot signal strengths; and

c) relative processed signal strengths.

23. A method according to claim 13, wherein said handoff parameters include at least one of the following:

a) a hysteresis value;

b) a drop timer value;

c) an averaging parameter; and

d) a handoff decision interval.

24. A method according to claim 13, wherein said handoff performance metric calculator uses a recursive procedure.