Base station based methods and apparatus for supporting break before make handoffs in a multi-carrier system

• US 7,376,425 B2
• Filed: 11/21/2005
• Issued: 05/20/2008
• Est. Priority Date: 12/05/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Li, Junyi, Lane, Frank A.
• Primary Examiner(s): Eng; George
• Assistant Examiner(s): PHAN, HUY Q
• Application Number:
  US11/283,676
• Publication Number:
  US 20060073836A1
• Time in Patent Office: 911 Days
• Field of Search: 455/437, 455/436, 455/442, 455/435.1, 455/439, 455/522, 455/435.2, 455/432.1, 370/331, 370/330, 370/328, 370/329, 370/332
• US Class Current: 455/437
• CPC Class Codes: H04W 36/00692 using simultaneous multiple data streams, e.g. cooperative multipoint [CoMP], carrier aggregation [CA] or multiple input multiple output [MIMO] allocation of physical resources in CoMP or in CA H04L5/0035
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 36/185 using make before break

Abstract

A mobile communications device initiates a handoff from its current base station (BS) sector network attachment point to a new BS sector. The mobile sends a handoff request over its current wireless link to the current BS sector, which forwards the request to the new BS sector, e.g., via a network link. The new BS sector processes the request assigning dedicated resources, e.g., an identifier and dedicated uplink segments information identifying the allocated resources is conveyed from the new BS sector via the current BS sector to the mobile. The mobile determines the time of the allocated dedicated segments based upon a received beacon signal from the new BS sector with known timing relationships to dedicated segments. The mobile breaks the original wireless link just prior to the time of the first assigned dedicated segment. The mobile communicates information on the assigned dedicated segments to perform registration operations, e.g., timing synchronization and power control, establishing a new wireless link.

Claims

1. A method of operating a second network point of attachment in a communications system including a first network point of attachment, the first network point of attachment using signals in a first frequency band to communicate with a mobile node having a communications link with said first network point of attachment over which data can be communicated, the method comprising:

transmitting beacon signals having a predetermined frequency into said first frequency band on a periodic basis, said first frequency band being a frequency band into which said second network attachment point does not transmit user data;

using a second frequency band which is different from said first frequency band for establishing and maintaining communications links with mobile nodes over which user data can be communicated, said step of using a second frequency band including assigning segments of an uplink communications channel to mobile nodes, the uplink communications channel having a structure that includes a periodic repeating pattern of access segments and traffic segments, access segments being segments into which mobile nodes that do not have an existing wireless communication link established with said second network attachment point can send at least one signal to said network attachment point over the air to establish a wireless communications link with the second network attachment point, each access segment occurring at a fixed time offset from the point at which one of said beacon signals is transmitted into said first frequency band by said second network attachment point, wherein each access segment includes a plurality of tones which can be used for uplink transmissions during at least one symbol transmission time period which occurs during the period of said access segment, said plurality of tones includes at least a first set of tones;

receiving a signal from said first network access point indicating that said mobile node is seeking to perform a handoff to said second network point of attachment from said first network point of attachment;

dedicating the first set of tones to a first mobile node which is coupled to said first network access point;

communicating information to the first mobile node via the first network access point indicating the dedication of said first set of tones to the first mobile node;

prior to receiving said access request signal, communicating information to said first mobile node, via the first network access point, indicating the time at which said access segment will occur relative to one of the beacon signals transmitted into said first frequency band;

monitoring the first set of tones in the first access segment for a registration signal from the mobile node to which said first access segment was assigned; and

receiving a registration signal from the mobile node which was communicated using said dedicated first set of tones.

2. The method of claim 1, further comprising:

monitoring at least one additional set of tones in the first access segment for a registration signal from a mobile node to which said additional set of tones was not dedicated, said additional set of tones being used on a contention basis.

3. The method of claim 1, further comprising:

establishing a secure communications link with said first access node prior to communicating information to the first mobile node via the first network access point indicating the dedication of said first set of tones to said first mobile node.

4. The method of claim 3, further comprising:

receiving at least one Internet Protocol packet with an IP address corresponding to said first mobile node prior to the time of said first access segment;

storing said IP packet; and

forwarding said IP packet to said mobile node over a wireless communications link established using the set of tones dedicated to said first mobile node in said first access segment.

5. A method of operating a second base station to perform a mobile node handoff operation involving a handoff of a mobile node from a first base station having a first communications link with said mobile node, the method comprising:

allocating a dedicated resource to be used by said mobile node when establishing a second communications link with said second base station;

transmitting information about the dedicated resource to said first base station by a communications link between said first and second base stations;

receiving a timing control signal over the air from said mobile node in an uplink communications segment dedicated to said mobile node by said second base station;

transmitting to said mobile node, after receiving said timing control signal, a timing synchronization signal, prior to receiving user data from said mobile node, wherein said timing synchronization signal is a control signal that instructs the mobile node to perform one of the following operations;

advance, retard or leave unaltered the transmission timing of symbols transmitted by said mobile node;

transmitting to said mobile node, after receiving said timing control signal, a transmission power control signal, prior to receiving user data from said mobile node;

establishing a secure communications link with said first base station prior to transmitting said information about the resource dedicated to said mobile node to said first base station;

transmitting high power narrowband signals on a periodic basis; and

communicating to said first base station information indicating a point in time said mobile node should register over the air with said second base station, said point in time having a fixed relationship to the time at which said base station transmits at least one of said high power narrowband signals.

6. An apparatus for operating a second network point of attachment in a communications system including a first network point of attachment, the first network point of attachment using signals in a first frequency band to communicate with a mobile node having a communications link with said first network point of attachment over which data can be communicated, comprising:

means for transmitting beacon signals having a predetermined frequency into said first frequency band on a periodic basis, said first frequency band being a frequency band into which said second network attachment point does not transmit user data;

means for using a second frequency band which is different from said first frequency band for establishing and maintaining communications links with mobile nodes over which user data can be communicated, said step of using a second frequency band including assigning segments of an uplink communications channel to mobile nodes, the uplink communications channel having a structure that includes a periodic repeating pattern of access segments and traffic segments, access segments being segments into which mobile nodes that do not have an existing wireless communication link established with said second network attachment point can send at least one signal to said network attachment point over the air to establish a wireless communications link with the second network attachment point, each access segment occurring at a fixed time offset from the point at which one of said beacon signals is transmitted into said first frequency band by said second network attachment point, wherein each access segment includes a plurality of tones which can be used for uplink transmissions during at least one symbol transmission time period which occurs during the period of said access segment, said plurality of tones includes at least a first set of tones;

means for receiving a signal from said first network access point indicating that said mobile node is seeking to perform a handoff to said second network point of attachment from said first network point of attachment;

means for dedicating the first set of tones to a first mobile node which is coupled to said first network access point;

means for communicating information to the first mobile node via the first network access point indicating the dedication of said first set of tones to the first mobile node;

means for prior to receiving said access request signal, communicating information to said first mobile node, via the first network access point, indicating the time at which said access segment will occur relative to one of the beacon signals transmitted into said first frequency band;

means for monitoring the first set of tones in the first access segment for a registration signal from the mobile node to which said first access segment was assigned; and

means for receiving a registration signal from the mobile node which was communicated using said dedicated first set of tones.

7. The apparatus of claim 6, further comprising:

means for monitoring at least one additional set of tones in the first access segment for a registration signal from a mobile node to which said additional set of tones was not dedicated, said additional set of tones being used on a contention basis.

8. The apparatus of claim 6, further comprising:

means for establishing a secure communications link with said first access node prior to

means for communicating information to the first mobile node via the first network access point indicating the dedication of said first set of tones to said first mobile node.

9. The apparatus of claim 8, further comprising:

means for receiving at least one Internet Protocol packet with an IP address corresponding to said first mobile node prior to the time of said first access segment;

means for storing said IP packet; and

means for forwarding said IP packet to said mobile node over a wireless communications link established using the set of tones dedicated to said first mobile node in said first access segment.

10. An apparatus for operating a second base station to perform a mobile node handoff operation involving a handoff of a mobile node from a first base station having a first communications link with said mobile node, the method comprising:

means for allocating a dedicated resource to be used by said mobile node when establishing a second communications link with said second base station;

means for transmitting information about the dedicated resource to said first base station by a communications link between said first and second base stations;

means for receiving a timing control signal over the air from said mobile node in an uplink communications segment dedicated to said mobile node by said second base station;

means for transmitting to said mobile node, after receiving said timing control signal, a timing synchronization signal, prior to receiving user data from said mobile node, wherein said timing synchronization signal is a control signal that instructs the mobile node to perform one of the following operations;

advance, retard or leave unaltered the transmission timing of symbols transmitted by said mobile node;

means for transmitting to said mobile node, after receiving said timing control signal, a transmission power control signal, prior to receiving user data from said mobile node;

means for establishing a secure communications link with said first base station prior to transmitting said information about the resource dedicated to said mobile node to said first base station;

means for transmitting high power narrowband signals on a periodic basis; and

means for communicating to said first base station information indicating a point in time said mobile node should register over the air with said second base station, said point in time having a fixed relationship to the time at which said base station transmits at least one of said high power narrowband signals.

11. A second network point of attachment comprising:

a processor configured to control said second network point of attachment to implement a method in a communications system including a first network point of attachment, the first network point of attachment using signals in a first frequency band to communicate with a mobile node having a communications link with said first network point of attachment over which data can be communicated, the method comprising;

transmitting beacon signals having a predetermined frequency into said first frequency band on a periodic basis, said first frequency band being a frequency band into which said second network attachment point does not transmit user data;

using a second frequency band which is different from said first frequency band for establishing and maintaining communications links with mobile nodes over which user data can be communicated, said step of using a second frequency band including assigning segments of an uplink communications channel to mobile nodes, the uplink communications channel having a structure that includes a periodic repeating pattern of access segments and traffic segments, access segments being segments into which mobile nodes that do not have an existing wireless communication link established with said second network attachment point can send at least one signal to said network attachment point over the air to establish a wireless communications link with the second network attachment point, each access segment occurring at a fixed time offset from the point at which one of said beacon signals is transmitted into said first frequency band by said second network attachment point, wherein each access segment includes a plurality of tones which can be used for uplink transmissions during at least one symbol transmission time period which occurs during the period of said access segment, said plurality of tones includes at least a first set of tones;

receiving a signal from said first network access point indicating that said mobile node is seeking to perform a handoff to said second network point of attachment from said first network point of attachment;

dedicating the first set of tones to a first mobile node which is coupled to said first network access point;

communicating information to the first mobile node via the first network access point indicating the dedication of said first set of tones to the first mobile node;

prior to receiving said access request signal, communicating information to said first mobile node, via the first network access point, indicating the time at which said access segment will occur relative to one of the beacon signals transmitted into said first frequency band;

monitoring the first set of tones in the first access segment for a registration signal from the mobile node to which said first access segment was assigned; and

receiving a registration signal from the mobile node which was communicated using said dedicated first set of tones.

12. A machine readable medium embodying machine executable instructions for controlling a second network point of attachment to implement a communications method in a communications system including a first network point of attachment, the first network point of attachment using signals in a first frequency band to communicate with a mobile node having a communications link with said first network point of attachment over which data can be communicated, the communications method comprising:

transmitting beacon signals having a predetermined frequency into said first frequency band on a periodic basis, said first frequency band being a frequency band into which said second network attachment point does not transmit user data;

using a second frequency band which is different from said first frequency band for establishing and maintaining communications links with mobile nodes over which user data can be communicated, said step of using a second frequency band including assigning segments of an uplink communications channel to mobile nodes, the uplink communications channel having a structure that includes a periodic repeating pattern of access segments and traffic segments, access segments being segments into which mobile nodes that do not have an existing wireless communication link established with said second network attachment point can send at least one signal to said network attachment point over the air to establish a wireless communications link with the second network attachment point, each access segment occurring at a fixed time offset from the point at which one of said beacon signals is transmitted into said first frequency band by said second network attachment point, wherein each access segment includes a plurality of tones which can be used for uplink transmissions during at least one symbol transmission time period which occurs during the period of said access segment, said plurality of tones includes at least a first set of tones;

receiving a signal from said first network access point indicating that said mobile node is seeking to perform a handoff to said second network point of attachment from said first network point of attachment;

dedicating the first set of tones to a first mobile node which is coupled to said first network access point;

communicating information to the first mobile node via the first network access point indicating the dedication of said first set of tones to the first mobile node;

prior to receiving said access request signal. communicating information to said first mobile node, via the first network access point, indicating the time at which said access segment will occur relative to one of the beacon signals transmitted into said first frequency band;

monitoring the first set of tones in the first access segment for a registration signal from the mobile node to which said first access segment was assigned; and

receiving a registration signal from the mobile node which was communicated using said dedicated first set of tones.

13. A method of operating a second network point of attachment in a communications system including a first network point of attachment and a.first mobile node, the first network point of attachment having a communications link with the first mobile node over which data can be communicated, the first network point of attachment using a first frequency band, the method comprising:

transmitting beacon signals having a predetermined frequency on a recurring basis; and

using a second frequency band which is different from said first frequency band for establishing and maintaining communications links with mobile nodes over which user data can be communicated, said step of using a second frequency band including assigning an access segment of an uplink communications channel to said first mobile node, the uplink communications channel having a structure that includes a repeating pattern of access segments and traffic segments, access segments being segments into whfth mobile nodes that do not have an existing wireless communication link established with said second network attachment point can send at least one signal to said network attachment point over the air to establish a wireless communications link with the second network attachment point, each access segment including a plurality of tones which can be used for uplink transmissions during at least one symbol transmission time period which, occurs during the period of the access segment, said plurality of tones including at least a first set of tones;

dedicating the first set of tones in a first access segment to said first mobile node;

monitoring the first set of tones in the first access segment for a registration signal from the first mobile node to which said first access segment was assigned; and

receiving a registration signal from the mobile node which was communicated using said dedicated first set of tones in said first access segment.

14. The method of claim 13, further comprising:

prior to performing said dedicating step, receiving a signal from said first network access point indicating that said mobile node is seeking to perform a handoff to said second network point of attachment from said first network point of attachment.

15. The method of claim 14, further comprising:

communicating information to the first mobile node via the first network access point indicating the dedication of said first set of tones in the first access segment to the first mobile node.

16. The method of claim 15, further comprising:

prior to receiving said access request signal, communicating information to said first mobile node, via the first network access point, indicating the time at which said access segment will occur relative to one of the beacon signals transmitted into said first frequency band.

17. A computer readable medium embodying machine executable instructions for controlling a second network point of attachment to implement a communications method,

the second network point of attachment being in a communications system including a first network point of attachment and a first mobile node, the first network point of attachment having a communications link with the first mobile node over which data can be communicated, the first network point of attachment using a first frequency band, the communications method comprising:

transmitting beacon signals having a predetermined frequency on a recurring basis; and

using a second frequency band which is different from said first frequency band for establishing and maintaining communications links with mobile nodes over which user data ca.n be communicated, said step of using a second frequency band including assigning segments of an uplink communications channel to said first mobile node, the uplink communications channel having a structure that includes a repeating pattern of access segments and traffic segments, access segments being segments into which mobile nodes that do not have an existing wireless communication link established with said second network attachment point can send at least one signal to said network attachment point over the air to establish a wireless communications link with the second network attachment point, each access segment including a plurality of tones which can be used for uplink transmissions during at least one symbol transmission time period which occurs during the period of said access segment, said plurality of tones including at least a first set of tones;

dedicating the first set of tones in a first access segment to said first mobile node;

monitoring the first set of tones in the first access segment for a registration signal from the first mobile node to which said first access segment was assigned; and

receiving a registration signal from the mobile node which was communicated using said dedicated first set of tones.

18. A second network point of attachment comprising:

a processor configured to control said second network point of attachment to implement a method in a communications system including a first network point of attachment, the first network point of attachment using signals in a first frequency band to communicate with a first mobile node having a communications link with said first network point of attachment over which data can be communicated, the method comprising;

transmitting beacon signals having a predetermined frequency on a recurring basis; and

using a second frequency band which is different from said first frequency band for establishing and maintaining communications links with mobile nodes over which user data can be communicated, said step of using a second frequency band including assigning segments of an uplink communications channel to said first mobile node, the uplink communications channel having a structure that includes a repeating pattern of access segments and traffic segments, access segments being segments into which mobile nodes that do not have an existing wireless communication link established with said second network attachment point can send at least one signal to said network attachment point over the air to establish a wireless communications link with the second network attachment point, each access segment including a plurality of tones which can be used for uplink transmissions during at least one symbol transmission time period which occurs during the period of said access segment, said plurality of tones including at least a first set of tones;

dedicating the first set of tones in a first access segment to said first mobile node;

monitoring the first set of tones in the first access segment for a registration signal from the first mobile node to which said first access segment was assigned; and

receiving a registration signal from the mobile node which was communicated using said dedicated first set of tones.

19. A second network point of attachment for use in a communications system including a first network point of attachment and a first mobile node, the first network point of attachment having a communications link with the first mobile node over which data can be communicated, the first network point of attachment using a first frequency band, the second network attachment point comprising:

a transmitter for transmitting beacon signals having a predetermined frequency on a recurring basis; and

a control module for controlling the second network point of attachment to use a second frequency band which is different from said first frequency band for establishing and maintaining communications links with mobile nodes over which user data cai-i be communicated, said step of using a second frequency band including assigning an access segment of an uplink communications channel to said first mobile node, the uplink communications channel having a structure that includes a repeating pattern of access segments and traffic segments, access segments being segments into which mobile nodes that do not have an existing wireless communication link established with said second network attachment point can send at least one signal to said network attachment point over the air to establish a wireless communications link with the second network attachment point, each access segment including a plurality of tones which can be used for uplink transmissions during at least one symbol transmission time period which occurs during the period of the access segment, said plurality of tones including at least a first set of tones;

a dedicated resource allocation module for dedicating the first set of tones in a first access segment to said first mobile node;

a registration module for monitoring the first set of tones in the first access segment for a registration signal from the first mobile node to which said first access segment was assigned; and

a receiver for receiving a registration signal from the mobile node which was communicated using said dedicated first set of tones in said first access segment.