Cellular communication system with common channel soft handoff and associated method

• US 6,216,004 B1
• Filed: 07/13/1998
• Issued: 04/10/2001
• Est. Priority Date: 06/23/1998
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tiedemann, Edward G. Jr., Sarkar, Sandip
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): Gesesse, Tilamun
• Application Number:
  US09/115,217
• Time in Patent Office: 1,002 Days
• Field of Search: 455/442, 455/443, 455/458, 455/517, 455/524, 455/525, 455/522, 455/67.1, 455/434, 370/331, 370/332
• US Class Current: 455/442
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 52/0245 according to signal strength
• CPC Class Codes: H04W 68/00 User notification, e.g. alerting and paging, for incoming communication, change of service or the like
• CPC Class Codes: H04W 68/025 Indirect paging
• CPC Class Codes: H04W 76/28 Discontinuous transmission [DTX]; Discontinuous reception [DRX]
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A cellular communications system comprising;

a mobile unit which designates an active set of base stations;

a base station; and

a base station controller which puts the base stations in the active set in common channel soft handoff.

Claims

1. A method of transmission of control information between a mobile unit and a base station in spread spectrum communications system:

monitoring by a mobile unit the power level of control signals received from multiple base stations;

identifying by the mobile unit a first set of base stations for which the received power level of the received control signal exceeds a prescribed level;

sending a power measurement message from the mobile unit to at least one base station in the set that identifies the base stations in the identified first set;

sending to the mobile unit by at least one base station a message that specifies a second set of base stations that are permitted to transmit to the mobile unit in soft handoff; and

communicating a control message to the mobile unit in soft handoff from multiple base stations that are members of both the first set and the second set;

wherein at least one member of the second set of base stations is determined based on independent soft handoff information other than the information provided by the mobile unit relating to the power level of control signals.

2. The method of claim 1 wherein the control signals monitored by the mobile unit are pilot signals.

3. The method of claim 1 wherein the control messages communicated to the mobile unit includes a paging message.

4. The method of claim 1 wherein the control message communicated to the mobile unit includes a forward common control channel message.

5. The method of claim 1 wherein the control message communicated to the mobile unit includes a paging message and a forward common control channel message.

6. The method of claim 1 further including:

designating time intervals during which a paging message may be sent to the mobile unit; and

wherein communicating a control message to the mobile unit in soft handoff from multiple base stations involves communicating a paging message during a designated time interval.

7. The method of claim 1 further including:

designating time intervals during which a paging message may be sent to the mobile unit and designating time intervals during which a forward common control channel message may be sent to the mobile unit; and

wherein communicating a control message to the mobile unit in soft handoff from multiple base stations involves communicating a paging message during a designated time interval and communicating a forward common control channel message during a designated time interval.

8. The method of claim 1 further including:

the mobile unit and at least one base station separately designating the same time intervals during which a control message may be sent to the mobile unit; and

wherein communicating a control message to the mobile unit in soft handoff from multiple base stations involves communicating a paging message during a designated time interval.

9. The method of claim 1 further including:

the mobile unit and at least one base station separately designating the same time intervals during which a control message may be sent to the mobile unit based at least in part upon identity of the mobile unit; and

wherein communicating a control message to the mobile unit in soft handoff from multiple base stations involves communicating a paging message during a designated time interval.

10. The method of claim 1 further including:

sending a mobile unit identification message from the mobile unit to at least one base station in the set that identifies the mobile unit to the at least one base station;

designating time intervals during which a control message may be sent to the mobile unit based at least in part upon identity of the mobile unit;

wherein designating time intervals involves the mobile unit and at least one base station separately arriving at the same time intervals based at least in part upon identity of the mobile unit.

11. The method of claim 1 further including:

entering a sleep mode by the mobile unit when the mobile unit does not have an assigned traffic channel and temporarily awakening from the sleep mode by the mobile unit from time to time when the mobile unit does not have an assigned traffic channel;

wherein communicating a control message to the mobile unit in soft handoff occurs while the mobile unit is temporarily awake when the mobile unit does not have an assigned traffic channel.

12. The method of claim 1 further including:

designating time intervals during which a control message may be sent to the mobile unit;

entering a sleep mode by the mobile unit when the mobile unit does not have an assigned traffic channel and temporarily awakening from the sleep mode by the mobile unit during a designated time interval;

wherein communicating a control message to the mobile unit in soft handoff occurs while the mobile unit is temporarily awake during a designated time interval when the mobile unit does not have an assigned traffic channel.

13. The method of claim 1 further including:

designating time intervals during which a control message may be sent to the mobile unit;

wherein communicating a control message to the mobile unit in soft handoff from multiple base stations occurs during a designated time interval.

14. The method of claim 1,

wherein the control message includes a quick page message and a corresponding forward common control channel message;

and further including;

designating time intervals during which a quick page message and a corresponding forward common control channel message may be sent to the mobile unit;

wherein communicating a control message to the mobile unit in soft handoff from multiple base stations may occurs during the time intervals designated for quick page messages and corresponding forward common control channel messages.

15. A method of transmission of control information between a mobile unit and a base station in spread spectrum communications system:

monitoring by a mobile unit the power level of control signals received from multiple base stations;

identifying by the mobile unit an Active Set of base stations based upon power levels of the received control signals;

sending messages from the mobile unit to at least one base station that identify the Active Set;

sending a handoff permission message from at least one base station to the mobile unit that specifies a set of base stations that are permitted to transmit control signals to the mobile unit in soft handoff; and

communicating a control message to the mobile unit in soft handoff from multiple base stations that are members of both the Active Set and the set of permitted base stations;

wherein at least one member of the permitted set of base stations is determined based on independent soft handoff information other than the information provided by the mobile unit relating to the power level of control signals.

16. The method of claim 15 further including:

designating time intervals during which a control message may be sent to the mobile unit;

wherein communicating a control message to the mobile unit in soft handoff from multiple base stations occurs during a designated time interval.

17. The method of claim 15 further including:

identifying by the mobile unit an Candidate Set of base stations based upon power levels of the received control signals; and

sending messages from the mobile unit to at least one base station that identify the Candidate Set;

wherein membership of the mobile unit Active Set and the Candidate Set may change between a time when the mobile unit sends a message that identifies the active Set or the Candidate Set and the time when a control message is communicated in soft handoff.

18. The method of claim 15 further including:

designating time intervals during which a control message may be sent to the mobile unit;

entering a sleep mode by the mobile unit when the mobile unit does not have an assigned traffic channel and temporarily awakening from the sleep mode by the mobile unit during a designated time interval;

wherein communicating a control message to the mobile unit in soft handoff occurs while the mobile unit is temporarily awake during a designated time interval when the mobile unit does not have an assigned traffic channel.

19. The method of claim 15,

wherein the control message includes a quick page message and a corresponding forward common control channel message;

and further including;

designating time intervals during which a quick page message and a corresponding forward common control channel message may be sent to the mobile unit;

wherein communicating a control message to the mobile unit in soft handoff from multiple base stations may occur during the time intervals designated for quick page messages and corresponding forward common control channel messages.

20. A method of transmission of control information between a mobile unit and a base station in spread spectrum communications system:

monitoring by a mobile unit the power level of pilot signals received from multiple base stations;

identifying by the mobile unit a first set of base stations based for which the received pilot signal power level exceeds a prescribed level;

sending a message from the mobile unit to at least one base station in the set that identifies the base stations in the identified first set;

sending a handoff permission message from at least one base station to the mobile unit that specifies a set of base stations that are permitted to transmit page signals and a set of base stations that are permitted to transmit forward common control channel messages to the mobile unit in soft handoff;

designating time intervals during which a page signal and a corresponding forward common control channel message may be sent to the mobile unit;

communicating a page signal to the mobile unit from single base station during a designated time interval or from multiple base stations in soft handoff during such designated time interval depending upon overlap of the constituents of the first set and the permitted sets; and

communicating a corresponding forward common control message from a single base station during a designated time interval or from multiple base stations in soft handoff during such designated time interval depending upon overlap of the of the first set and the permitted sets;

wherein at least one member of the permitted set of base stations is determined based on independent soft handoff information other than the information provided by the mobile unit relating to the power level of control signals.