Method of handoff control in an enterprise code division multiple access wireless system

• US 7,016,331 B1
• Filed: 09/05/2000
• Issued: 03/21/2006
• Est. Priority Date: 09/05/2000
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Joo, Ki Hyun, Hyun, Sang Kyoon, Rha, Peter S., Kang, Chol Su
• Primary Examiner(s): Phunkulh, Bob A.
• Application Number:
  US09/655,107
• Time in Patent Office: 2,023 Days
• Field of Search: 370/328, 370/329, 370/331, 370/332, 370/333, 370/334, 370/335, 370/336, 370/342, 455/422.1, 455/436, 455/437, 455/438, 455/439, 455/440, 455/441, 455/442
• US Class Current: 370/334
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface
• CPC Class Codes: H04W 36/32 by location or mobility data, e.g. speed data
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 80/00 Wireless network protocols or protocol adaptations to wireless operation

Abstract

A wireless office communication system including a wireless internet base station (WIBS) encompassing a base station controller (BSC), a mobile switch controller (MSC), and an ethernet interface module for coupling the wireless internet base station (WIBS) to an existing internet protocol (IP) based network. A wireless office communication system can also be based on the conventional architecture comprising the base station transceiver subsystem BTS, BSC, and MSC. The WIBS or BTS is attached to a number of antennas via different and identifiable delay elements for the purpose of determining the serving antennas of mobile communication units. A location determination logic enables the system to handle handoffs between a WIBS or BTS and the external public communication system in an optimum manner. Handling handoff requests in this manner prevents unnecessary ping-ponging of hand off and can also increase the percentage of successful handoff by frequency monitoring of the quality of the mobile communication units located in the handoff transition area, particularly to the public communication system.

Claims

1. A hand-off method for a mobile communicating unit in a Code Division Multiple Access (CDMA) enterprise system in communication with an external public cellular system, comprising the steps of:

sending a plurality of handoff request signals by the mobile communication unit to a base station within the enterprise system;

decoding said plurality of handoff request signals;

identifying which one of said plurality of handoff request signals emanates from a pre-designated handoff transition region within the enterprise system;

handing off said identified handoff request signal to said external public cellular system; and

time delaying the handoff request signals to the base station, wherein the step of time delaying the handoff request signals includes the step of dividing said handoff request signals into multiple request signals responsive to multiple extended antenna units within the enterprise system.

2. The method of claim 1, further comprising the step of combining said divided delayed signals into a single request signal to said base station.

3. The method of claim 1, wherein said transmit distribution subsystem comprises a plurality of signal transmit delay elements coupled to a signal dividing unit.

4. The method of claim 1, wherein said step of time delaying the handoff request signals includes the step of inserting time delays only in handoff request signals sent by mobile units in the enterprise system.

5. The method of claim 1, wherein said step of time delaying the handoff request signals includes the step of inserting time delays only in the handoff request signals sent to base stations within the enterprise communication system.

6. A method of handling communications handoff between a mobile communication unit within a code division multiple access communication system and an external public cellular system, comprising the steps of:

designating a handoff region within said communication system;

receiving a plurality of handoff request signals;

identifying an originating location of said handoff request signals by routinely making delay measurements of each of said plurality of handoff request signals;

using said location identification information to hand off each of said request signals; and

time delaying the handoff request signals to the base station, wherein the step of time delaying the handoff request signals includes the step of dividing said handoff request signals into multiple request signals responsive to multiple extended antenna units within the enterprise system.

7. The method of claim 6, further comprising the step of determining whether a receiving base station is receiving handoff request signals is emanating from said handoff transition region.

8. The method of claim 6, wherein if said handoff request signal emanates from said transition region, the mobile communication unit transmitting said handoff request signal is handed off to the external public cellular system.

9. The method of claim 6, wherein if said handoff request signal emanates from a location outside said transition region said mobile communication unit transmitting said handoff request signal is handed off to a base station within the communication system.

10. A method of optimizing handoff between a plurality of mobile communication units within an enterprise code division multiple access (CDMA) communication system and an external public cellular communication system, comprising the steps of:

each of said plurality of mobile communication unit sending a handoff request signal comprising a pilot strength measurement message (PSMM) to a base station within the CDMA communication system;

determining the location of said plurality of mobile communication units by making routine delay measurements of each of said plurality of mobile communication units;

determining whether said mobile communication unit is in a handoff transition area within the CDMA communication system;

handing-off said mobile communication unit to said external public communication system; and

time delaying the handoff request signals to the base station, wherein the step of time delaying the handoff request signals includes the step of dividing said handoff request signals into multiple request signal responsive to multiple extended antenna units within the enterprise system.

11. The method of claim 10, further comprising the step of determining prior to the hand-off step whether said hand-off request signals meets a enterprise system and public cellular system hand-off criteria.

12. The method of claim 11, wherein if the hand-off request signal meets the enterprise system and public system hand-off criteria said PSMM is sent to a target base station in said public system.