Semi-hard handoff in a cellular telecommunications systems

• US 5,790,528 A
• Filed: 12/13/1996
• Issued: 08/04/1998
• Est. Priority Date: 01/27/1994
• Status: Expired due to Fees

• Current Assignee: Nokia Siemens Networks Oy (Nokia Corporation)
• Original Assignee: Nokia Telecommunications Oy (Nokia Corporation)
• Inventors: Muszynski, Peter
• Primary Examiner(s): Marcelo, Melvin
• Application Number:
  US08/676,392
• Time in Patent Office: 599 Days
• Field of Search: 370/328, 370/331-334, 455/436-444
• US Class Current: 370/331
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection

Abstract

In a CDMA cellular telecommunications system, comprising mobile exchanges (MSC), base stations (BS) and mobile stations (MS), a new CDMA handoff procedure, a semi-hard handoff, is employed. Semi-hard handoff takes place within one and the same border base station (BS12), located in the boundary of two service areas (SA1, SA2) which are controlled by neighbouring mobile exchanges (MSC1, MSC2). This border base station is connected to and can be accessed from both of these neighbouring mobile exchanges. The inventive semi-hard handoff is a network based handoff of the communication control functions from the first to the second neighbouring mobile exchange without interrupting the active CDMA radio communications between the border base station (BS12) and the mobile station (MS).

Claims

1. A cellular telecommunications system comprising

a plurality of mobile stations (MS20),

a first mobile exchange (MSC1),

a second mobile exchange (MSC2),

a plurality of base stations, a first group (BS10) of said plurality of base stations being connected solely to said first mobile exchange (MSC1), a second group (BS14) of said plurality of base stations being connected solely to said second mobile exchange (MSC2), and at least one of said plurality of base stations being a border base station (BS12) connected to both said first mobile exchange and said second mobile exchange,

means at said first mobile exchange for requesting a semi-hard handoff from said second mobile exchange,

means at said second mobile exchange for allocating control and diversity combining resources required by said second mobile exchange for processing and controlling user communications,

means at said at least one border base station for switching over user communications signals from said first mobile exchange towards said second mobile exchange,

means at said second mobile exchange for taking control of user communications by means of said allocated resources,

means at said second mobile exchange for informing an associated one of said plurality of mobile stations about the semi-hard handoff,

means at said second mobile exchange for acknowledging the successful completion of the semi-hard handoff to said first mobile exchange,

means at said first mobile exchange for releasing resources involved with user communications.

2. System according to claim 1, wherein the system is a CDMA system.

3. System according to claim 1, wherein the system is a TDMA system.

4. In a cellular telecommunications system comprising

a plurality of mobile stations,

a first mobile exchange,

a second mobile exchange,

a plurality of base stations, a first group of said plurality of base stations being connected solely to said first mobile exchange, a second group of said plurality of base stations being connected solely to said second mobile exchange, and at least one of said plurality of base stations being a border base station connected to both said first mobile exchange and said second mobile exchange,

the method of semi-hard handoff for handing off the control and signal diversity combining functions involved with ongoing user communications from said first mobile exchange to said second mobile exchange without disrupting the radio communications between an associated one of said plurality of mobile stations and said at least one border base station, the semi-hard handoff comprising the steps of

requesting a semi-hard handoff from said second mobile exchange by said first mobile exchange,

allocating control and diversity combining resources required by said second mobile exchange for processing and controlling said ongoing user communications,

switching over said ongoing user communications signals from said first mobile exchange towards said second mobile exchange at said at least one border base station,

taking control of said ongoing user communications by said second mobile exchange by means of said allocated resources,

informing said associated one of said plurality of mobile stations about the semi-hard handoff,

acknowledging the successful completion of semi-hard handoff to said first mobile exchange,

releasing resources involved with said ongoing user communications at said first mobile exchange.

5. Method according to claim 4, wherein the semi-hard handoff is utilized in a CDMA system.

6. Method according to claim 4, wherein the semi-hard handoff is utilized in a TDMA system.