Precision hard handoff method using pilot beacon distributors

• US 6,424,834 B1
• Filed: 07/31/1999
• Issued: 07/23/2002
• Est. Priority Date: 02/02/1999
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Corporation
• Inventors: Chang, Chu-Rui, Yee, Meng
• Primary Examiner(s): Maung, Nay
• Assistant Examiner(s): GELIN, JEAN ALLAND
• Application Number:
  US09/365,262
• Time in Patent Office: 1,088 Days
• Field of Search: 455/434, 455/436, 455/437, 455/438, 455/439, 455/440, 455/443, 455/444, 455/561, 455/562, 455/11.1, 455/448, 455/25, 370/331, 370/334, 370/335, 370/336, 370/342
• US Class Current: 455/436
• CPC Class Codes: H04W 16/30 Special cell shapes, e.g. doughnuts or ring cells
• CPC Class Codes: H04W 36/32 by location or mobility data, e.g. speed data
• CPC Class Codes: H04W 36/326 by proximity to another entity

Abstract

A method and system for providing a precision hard handoff between two networks is disclosed. The two networks include a first wireless communication system for serving a defined area, such as a campus, at a first frequency and a second wireless communication system adjacent to the first system and operating at a second frequency. A first pilot beacon distributor is positioned at a transition point of the campus for directionally transmitting a first pilot beacon signal into the campus. When a mobile unit operating on the second frequency crosses the transition point into the campus, it receives the first pilot beacon signal and it shifts operation to the first frequency.

Claims

1. A method for a precision hard handoff from a covering network having a first frequency to a target network having a second frequency, said covering network and said target network both using CDMA technology, said method comprising the steps of:

installing a plurality of pilot beacon distributors having paired directional antennas;

transmitting a pilot beacon signal from one of the pilot beacon distributors; and

triggering a precision hard handoff of the mobile unit from the covering network to the target network by using the pilot beacon signal,

wherein all the above steps are performed in a small border area between the covering network and the target network.

2. The method of claim 1 further comprising connecting a pilot beacon source to the pilot beacon distributors through a plurality of fiber optical cables.

3. The method of claim 1 wherein the paired directional antennas include a first directional antenna having a high front-to-back signal ratio for transmitting the pilot beacon signal and a second directional antenna for transmitting a non-beacon signal.

4. The method of claim 3 wherein the second directional antenna is coupled with the first directional antenna in a back lobe direction of the first directional antenna.

5. The method of claim 3 wherein both the first and the second directional antennas use the first frequency for transmissions.

6. The method of claim 1 wherein the step of triggering further includes the steps of:

receiving the pilot beacon signal by the mobile unit entering the border area;

negotiating a handoff with the covering network; and

completing the precision hard handoff to the target network.

7. The method of claim 6 wherein, when the mobile unit is active, the step of negotiating further includes the steps of:

requesting a soft handoff to the covering network by the mobile unit;

identifying the pilot beacon by the covering network;

refusing the soft handoff by the covering network; and

instructing the mobile unit to start the precision hard handoff to the target network.

8. The method of claim 6 wherein, when the mobile unit is idle, the step of negotiating further includes the steps of:

identifying the pilot beacon signal by the mobile unit;

reading the information in a paging channel by the mobile unit; and

instructing the mobile unit to start the precision hard handoff to the target network by a pre-enabled Global Service Redirection parameter in the paging channel.

9. A method for a precision hard handoff of a mobile unit between a first CDMA communication network using a first frequency and a second CDMA communication network using a second frequency, the mobile unit using the first frequency if it is covered initially under the first network and using the second frequency if it is covered initially under the second network, the method comprising the steps of:

installing a first pilot beacon distributor for directing the precision hard handoff from the first network to the second network in a border area between the first and the second networks;

installing a second pilot beacon distributor for directing the hard handoff from the second network to the first network in the border area between the first and the second networks;

transmitting a first pilot beacon signal by the first pilot beacon distributor at the first frequency;

transmitting a second pilot beacon signal by the second pilot beacon distributor at the second frequency;

identifying the first pilot beacon signal by the mobile unit if the mobile unit moves from the first network to the second network;

identifying the second pilot beacon signal by the mobile unit if the mobile unit moves from the second network to the first network;

negotiating a needed handoff; and

completing the precision hard handoff,

wherein all the above steps are taken in a small border area between the first network and the second network.

10. The method of claim 9 wherein the step of installing a first pilot beacon distributor further includes the steps of:

installing a pilot beacon source for generating the first pilot beacon signal; and

transmitting the first pilot beacon signal to the first pilot beacon distributor through a fiber optical cable.

11. The method of claim 9 wherein the step of installing a second pilot beacon distributor further includes the steps of:

installing a pilot beacon source for generating the second pilot beacon signal; and

transmitting the second pilot beacon signal to the second pilot beacon distributor through a fiber optical cable.

12. The method of claim 9 wherein the first pilot beacon distributor includes a first directional antenna transmitting the first pilot beacon signals at the first frequency and a second directional antenna coupled in a back lobe direction of the first directional antenna transmitting other signals also at the first frequency.

13. The method of claim 12 wherein the first directional antenna has a high front-to-back signal ratio.

14. The method of claim 9 wherein the second pilot beacon distributor includes a first directional antenna transmitting the second pilot beacon signals at the second frequency and a second directional antenna coupled in a back lobe direction of the first directional antenna transmitting non-beacon signals at the second frequency.

15. The method of claim 14 wherein the first directional antenna has a high front-to-back signal ratio.

16. The method of claim 9 wherein, when the mobile unit is active and moving from the first network to the second network, the step of negotiating further includes the steps of:

requesting a soft handoff to the first network by the mobile unit;

identifying the first pilot beacon by the first network;

refusing the soft handoff by the first network; and

instructing the mobile unit to start the precision hard handoff to the second network.

17. The method of claim 16 wherein the step of requesting includes sending a Pilot Strength Measurement Message to the first network by the mobile unit.

18. The method of claim 16 wherein the step of instructing includes sending an Extended Handoff Direction Message to the mobile unit by the first network.

19. The method of claim 9 wherein, when the mobile unit is active and moving from the second network to the first network, the step of negotiating further includes the steps of:

requesting a soft handoff to the second network by the mobile unit;

identifying the second pilot beacon by the first network;

refusing the soft handoff by the second network; and

instructing the mobile unit to start the precision hard handoff to the first network.

20. The method of claim 19 wherein the step of requesting includes sending a Pilot Strength Measurement Message to the second network by the mobile unit.

21. The method of claim 19 wherein the step of instructing includes sending an Extended Handoff Direction Message to the mobile unit by the second network.

22. The method of claim 9 wherein, when the mobile unit is idle, the step of negotiating further includes the steps of:

identifying the first or the second pilot beacon signal by the mobile unit;

reading the information in a paging channel by the mobile unit; and

instructing the mobile unit to start the precision hard handoff to the first or the second network determined by a pre-enabled Global Service Redirection parameter in the paging channel.

23. A system for directing a mobile unit to complete a precision hard handoff from a covering network having a first frequency to a target network having a second frequency, said covering network and said target network both use CDMA technology, said system comprising:

a plurality of pilot beacon distributors having paired directional antennas in a border area between the covering network and the target network for transmitting pilot beacon signals; and

means for triggering a precision hard handoff of the mobile unit from the covering network to the target network by using one of the pilot beacon signals.

24. The system of claim 23 wherein the pilot beacon distributors are connected to a pilot beacon source through a plurality of fiber optical cables.

25. The system of claim 23 wherein the paired directional antennas include a first directional antenna having a high front-to-back signal ratio for transmitting the pilot beacon signal and a second directional antenna for transmitting non-beacon signals.

26. The system of claim 25 wherein the second directional antenna is coupled with the first directional antenna in a back lobe direction of the first directional antenna.

27. The system of claim 25 wherein both the first and the second directional antennas use the first frequency for transmissions.

28. The system of claim 23 whereby the mobile unit receives the pilot beacon signal in the border area, negotiates a handoff with the covering network, and completes the precision hard handoff to the target network.

29. The system of claim 28 whereby the mobile unit negotiates the handoff, when the mobile unit is active, comprising:

means for identifying the pilot beacon in response to a soft handoff request sent to the covering network;

means for refusing the soft handoff request; and

means for instructing the mobile unit to start the precision hard handoff to the target network.

30. The system of claim 28 whereby the mobile unit negotiates the handoff, when the mobile unit is idle, comprising:

means for instructing the mobile unit to start the precision hard handoff to the target network by a pre-enabled Global Service Redirection parameter in a paging channel indicated by the pilot beacon signal.

31. A wireless communication system for providing high volume coverage inside a primary coverage area operating at a primary frequency, the system comprising:

at least one base station in the high volume coverage area operating at a second frequency; and

a first pilot beacon distributor positioned at a transition point between the primary coverage area and the high volume coverage area for directionally transmitting a first pilot beacon signal into the high volume coverage area;

whereby a mobile unit operating on the primary frequency and traveling into the high volume coverage area can receive the first pilot beacon signal and shift operation to the second frequency when crossing the transition point.

32. The system of claim 31 further comprising:

a second pilot beacon distributor positioned at the transition point for directionally transmitting a second pilot beacon signal away from the high volume coverage area;

whereby a mobile unit operating on the second frequency and traveling out of the high volume coverage area can receive the second beacon signal and shift operation to the primary frequency when crossing the transition point.

33. The system of claim 31 wherein the first beacon signal operates at the primary frequency.

34. The system of claim 31 wherein the second beacon signal operates at the second frequency.

35. The system of claim 32 wherein the first and second beacon signal distributors are positioned at a distance to prevent a ping-pong phenomenon between the primary and second frequencies.

36. The system of claim 32 wherein the first beacon signal distributor has a first directional antenna having a high front-to-back signal ratio for transmitting the first pilot beacon signal and enhancing the coverage of the second frequency, and a second directional antenna coupled in a back lobe direction of the first directional antenna for improving the precision of the hard handoff, eliminating a ping-pong phenomenon, and enhancing the coverage of the primary frequency.

37. The system of claim 32 wherein the second beacon signal distributor has a first directional antenna having a high front-to-back signal ratio for transmitting the second pilot beacon signal and enhancing the coverage of the second frequency, and a second directional antenna coupled in a back lobe direction of the first directional antenna for improving the precision of the hard handoff, eliminating a ping-pong phenomenon, and enhancing the coverage of the primary frequency.