Method and device for preventing toggling between two zones of a wireless communications network

• US 6,571,096 B2
• Filed: 11/10/1999
• Issued: 05/27/2003
• Est. Priority Date: 11/12/1998
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Plunkett, Robert Thomas
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): WASHINGTON, ERIKA ALISE
• Application Number:
  US09/438,055
• Publication Number:
  US 20010049287A1
• Time in Patent Office: 1,294 Days
• Field of Search: 455/436, 455/437, 455/443, 455/448, 455/449, 455/432, 455/462, 455/552, 455/553, 455/442, 455/414, 370/331
• US Class Current: 455/436
• CPC Class Codes: H04W 36/008375 based on historical data
• CPC Class Codes: H04W 36/302 due to low signal strength
• CPC Class Codes: H04W 36/362 Conditional handover

Abstract

A method and device for preventing toggling between two zones of a wireless communications network employ first and second adjacent cells respectively offering services of first and second different zones. The mobile unit determines if the second zone is more preferable than the first zone when the mobile unit hands off from the first cell to the second cell. If the second zone is less preferable than the first zone, the mobile unit does not switch to the second zone within the second cell. If the second zone is more preferable, the first zone is maintained within the second cell until the signal strength of the second cell exceeds the signal strength of the first cell by an amount determined by an exit parameter. At this point, the mobile unit switches to the services of the second zone. Alternatively, after the mobile unit enters the second cell from the first cell, the mobile unit may be prevented from using services of the second zone if there is a hysteresis parameter associated with the second zone in the second cell and the mobile unit was not using services of the second zone in the first cell, before entering the second cell. Even if there is a hysteresis parameter associated with the second zone in the second cell, the mobile unit may be permitted to power up in the second cell on the second zone.

Claims

1. A method of preventing toggling in a wireless network having first and second adjacent cells, the first cell offering services of at least a first zone, the second cell offering services of both the first zone and a second zone, the services of the first zone being different from the services of the second zone, comprising:

maintaining the services of the first zone after a mobile unit hands off from the first cell to the second cell; and

switching to the services of the second zone after the mobile unit travels within the second cell, past the hand off point to the second cell, wherein the transition point to the second zone is offset from the handoff point to the second cell.

2. A method according to claim 1, wherein the services of the first zone are maintained within the second cell until the signal strength of the second cell exceeds the signal strength of the first cell by a predetermined amount.

3. A method according to claim 1, wherein the services of the first zone are maintained within the second cell until the signal strength of the second cell exceeds the signal strength of the first cell by an amount equivalent to an exit parameter, the exit parameter depending on the identities of the cell and zone with which the mobile unit was communicating prior to entering the second cell.

4. A method according to claim 3, wherein the exit parameter is transmitted to the mobile unit by the cell with which the mobile unit was communicating prior to entering the second cell.

5. A method according to claim 3, wherein the exit parameter is obtained from a list of exit parameters stored in the memory of the mobile unit, an appropriate exit parameter being selected from the list based on the identities of the cell and zone with which the mobile unit was communicating prior to entering the second cell.

6. A method according to claim 3, wherein the exit parameter is updated to correspond with the second cell and the second zone after the mobile unit has switched to the services of the second zone.

7. A wireless network for preventing a mobile unit from toggling between services of first and second zones, comprising:

a first cell to offer services of at least the first zone; and

a second cell, adjacent to the first cell, to offer services of the first and second zones, the services of the first zone being different from the services of the second zone, the first and second cells overlapping at a handoff point where a mobile unit switches communication between the first and second cells, the second cell maintaining the services of the first zone after the mobile unit switches communication to the second cell at the hand off point, the second cell switching to the services of the second zone after the mobile unit travels within the second cell, past the hand off point.

8. A method of preventing toggling in a wireless network having first and second adjacent cells and second and third adjacent cells, the first cell offering services of at least a first zone, the second cell offering services of both the first zone and a second zone, the third cell offering services of at least the second zone, the services of the first zone being different from the services of the second zone, wherein a mobile unit hands off when the mobile unit moves between the cells, comprising:

determining if the services of the second zone are more preferable to the mobile unit than the services of the first zone when the mobile unit moves from the first cell to the second cell;

maintaining the services of the first zone after the mobile unit moves from the first cell to the second cell even if the services of the second zone is more preferable to the mobile unit than the services of the first zone, the second cell being a hysteresis cell for the service of the second zone; and

switching from the services of the first zone to the services of the second zone when the mobile unit moves from the second cell to the third cell.

9. A wireless network system for allowing a mobile unit which hands off between cells to switch services of each zone, comprising:

a first cell offering service of a first zone;

a second cell offering services of both the first zone and a second zone, the services of the first zone being different form services of second zone; and

a third cell allocated between the first cell and the second cell and designated as hysteresis cell for the second zone, offering service of both the first zone and the second zone;

wherein the system prevents the mobile unit from switching from services of the second zone to services of first zone when the mobile unit hands off from second cell to third cell if the second zone is more preferable than the first zone, and the system allows the mobile unit to switch from services of the second zone to services of first zone when the mobile unit hands off from third cell to first cell.

10. The wireless network system according to claim 9,

wherein the mobile unit powers up within the third cell having a hysteresis parameter set for the second zone.

11. The wireless network system according to claim 9,

wherein the system prevents the mobile unit from switching from services of the first zone to services of the second zone when the mobile unit hands off from the first cell to the third cell even though the second zone is more preferable than the first zone, and the system allows the mobile unit to switch from services of the first zone to services of the second zone when the mobile unit hands off from the third cell to the second cell.

12. The wireless network system according to claim 11,

wherein the mobile unit powers up within the third cell having a hysteresis parameter set for the second zone.

13. A method of allowing a mobile unit which hands off between cells to switch services of each zone, a first cell offering service of a first zone, a second cell offering services of both the first zone and a second zone, the services of the first zone being different form services of second zone, a third cell allocated between the first cell and the second cell and designated as hysteresis cell for the second zone, offering service of both the first zone and the second zone, comprising:

preventing the mobile unit from switching from services of the second zone to services of the first zone when the mobile unit hands off from the second cell to the third cell if the second zone is more preferable than the first zone. and

allowing the mobile unit to switch from services of the second zone to services of the first zone when the mobile unit hands off from the third cell to the second cell.

14. The method according to claim 13, further comprising:

preventing the mobile unit from switching from services of the first zone to services of the second zone when the mobile unit hands off from the first cell to the third cell even though the second zone is more preferable than the first zone, and

allowing the mobile unit to switch from services of the first zone to services of the second zone when the mobile unit hands off from the third cell to the second cell.

15. A wireless network system for allowing a mobile unit which hands off between cells to switch services of each zone, comprising:

a first cell offering service of a first zone;

a second cell offering service of a second zone, the service of the first zone being different form service of second zone; and

a third cell allocated between the first cell and the second cell and designated as hysteresis cell for the first zone and the second zone, offering services of both the first zone and the second zone;

wherein the system prevents the mobile unit from switching from services of the second zone to services of first zone when the mobile unit hands off from second cell to third cell if the second zone is more preferable than the first zone, and the system allows the mobile unit to switch from services of the second zone to services of first zone when the mobile unit hands off from third cell to first cell.

16. The wireless network system according to claim 15,

wherein the mobile unit powers up within the third cell having a hysteresis parameter set for the second zone.

17. The wireless network system according to claim 15,

wherein the system prevents the mobile unit from switching from services of the first zone to services of the second zone when the mobile unit hands off from the first cell to the third cell even though the second zone is more preferable than the first zone, and the system allows the mobile unit to switch from services of the first zone to services of the second when the mobile unit hands off from the third cell to the second cell.

18. The wireless network system according to claim 17,

wherein the mobile unit powers up within the third cell having a hysteresis parameter set for the second zone.

19. A method of allowing a mobile unit which hands off between cells to switch services of each zone, a first cell offering service of a first zone, a second cell offering service of a second zone, the service of the first zone being different form service of second zone, a third cell allocated between the first cell and the second cell and designated as hysteresis cell for the first zone and the second zone, offering service of both the first zone and the second zone, comprising:

preventing the mobile unit from switching from services of the second zone to services of the first zone when the mobile unit hands off from the second cell to the third cell if the second zone is more preferable than the first zone. and

allowing the mobile unit to switch from services of the second zone to services of the first zone when the mobile unit hands off from the third cell to the first cell.

20. The method according to claim 19, further comprising:

preventing the mobile unit from switching from services of the first zone to services of the second zone when the mobile unit hands off from the first cell to the third cell even though the second zone is more preferable than the first zone, and

allowing the mobile unit to switch from services of the first zone to services of the second zone when the mobile unit hands off from the third cell to the second cell.

21. A wireless network system for allowing a mobile unit which hands off between cells to switch services of each zone, comprising:

a first cell offering service of a first zone;

a second cell offering service of both the first zone and a second zone, the service of the first zone being different form service of second zone; and

a third cell allocated between the first cell and the second cell and designated as hysteresis cell for the second zone, offering services of both the first zone and the second zone;

wherein the system allows the mobile unit to switch from services of the first zone to services of second zone when the mobile unit hands off from first cell to second cell at the normal handoff point if the second zone is more preferable than the first zone, and the system prevents the mobile unit from switching from services of the second zone to services of first zone at the normal handoff point so that the mobile unit switches from switching from services of the second zone to services of first zone when the mobile unit hands off from the third cell to the first cell at a handoff point which is offset from the normal handoff point.

22. A method of allowing a mobile unit which hands off between cells to switch services of each zone, a first cell offering service of a first zone, a second cell offering service of both the first zone and a second zone, the service of the first zone being different form service of second zone, and a third cell allocated between the first cell and the second cell and designated as hysteresis cell for the second zone, offering services of both the first zone and the second zone, comprising:

allowing the mobile unit to switch from services of the first zone to services of second zone when the mobile unit hands off from first cell to second cell at the normal handoff point if the second zone is more preferable than the first zone; and

preventing the mobile unit from switching from services of the second zone to services of first zone at the normal handoff point so that the mobile unit switches from switching from services of the second zone to services of first zone when the mobile unit hands off from the third cell to the first cell at a handoff point which is offset from the normal handoff point.