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

• US 7,047,009 B2
• Filed: 10/14/2004
• Issued: 05/16/2006
• Est. Priority Date: 12/05/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Flarion Technologies (Qualcomm, Inc.)
• Inventors: Laroia, Rajiv, Li, Junyi, Lane, Frank A.
• Primary Examiner(s): Trinh, Sonny
• Assistant Examiner(s): PHAN, HUY Q
• Application Number:
  US10/964,945
• Publication Number:
  US 20050124344A1
• Time in Patent Office: 579 Days
• Field of Search: 455/437, 455/436, 455/442, 455/435.1, 455/439, 455/522, 455/435.2, 370/328, 370/329, 370/330, 370/331
• 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 attachment point in a communications system including a first network attachment point, the first network attachment point using signals in a first frequency band to communicate with a first mobile node having a communications link with said first network attachment point over which data can be communicated, the method comprising:

transmitting, at a high power level, high power narrowband beacon signals having a predetermined frequency into said first frequency band on a repeating basis, said first frequency band being a frequency band into which said second network attachment point does not transmit user data, said high power level being a per tone power level that is multiple times higher than the average per tone power level used by said second network attachment point to transmit user data during a period of time in which said beacon signals are repeatedly transmitted; 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 mobile nodes, 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 second network attachment point over the air to establish a wireless communications link with the second network attachment point, each access segment occurring at a predetermined 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.

2. The method of claim 1, wherein said high power narrowband beacon signals have at least 10 times the average per tone signal energy of tones used to transmit user data in the second frequency band during a period of time, the method further comprising:

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

3. The method of claim 2, 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, the method further comprising:

dedicating the first set of tones in a first access segment to said first mobile node which is coupled to said first network attachment point, said first set of tones being a tone subset that includes less than all the tones in the first access segment; and

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

4. The method of claim 3, further comprising:

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

5. The method of claim 1, wherein said first network attachment point is a sector of a first base station and wherein said second network attachment point is a sector of a second base station, the method further comprising:

allocating a dedicated resource to be used by said first mobile node when establishing a second communications link with said second network attachment point;

transmitting information about the dedicated resource to said first network attachment point by a communications link between said first and second network attachment points;

receiving a timing control signal over the air from said first mobile node in an uplink communications segment dedicated to said first mobile node by said second network attachment point; and

transmitting to said first mobile node, after receiving said timing control signal, a timing synchronization signal, prior to receiving user data from said first mobile node.

6. The method of claim 5, wherein said information about the dedicated resource provides information sufficient for the first mobile node to identify the uplink communications segment dedicated to said first mobile node.

7. The method of claim 5, wherein said information about the dedicated resource includes a device identifier to be used by said first mobile node when communicating over the air with said second network attachment point.

8. A method of operating a second network attachment point in a communications system including a first network attachment point, the first network attachment point 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 recurring basis, said first frequency band being a frequency band into which said second network attachment point does not transmit user data; and

using a second frequency band which is different from said first frequency band for establishing and maintaining communications links with mobile nodes, said step of using a second frequency band including assigning segments or an uplink communications channel to mobile nodes, 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 second network attachment point over the air to establish a wireless communications link with the second network attachment point, access segments having a predetermined time offset relationship to beacon signals that are transmitted into said first frequency band by said second network attachment point;

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

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

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

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.

9. The method of claim 8, 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.

10. The method of claim 8, further comprising:

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

11. The method of claim 10, further comprising:

receiving at least one Internet Protocol packet with an IP address corresponding to said 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 mobile node in said first access segment.

12. 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, said dedicated resource including at least a dedicated set of uplink tones to be used by said mobile node for a period of time when performing a timing synchronization operation as part of establishing a second communications link with said second base station, said dedicated set of uplink tones being less than a full set of tones available for uplink signaling to said second base station during said period of time;

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 on said uplink tones dedicated to said mobile node by said second base station; and

transmitting to said mobile node, after receiving said timing control signal, a timing synchronization signal, prior to receiving user data from said mobile node.

13. The method of claim 12, wherein said information about the dedicated resource provides information sufficient for the mobile node to identify an uplink communications segment dedicated to said mobile node.

14. The method of claim 12, wherein said information about the dedicated resource provides information sufficient for the mobile node to identify the period of time for which the tones were dedicated.

15. The method of claim 14, further comprising:

receiving user data from said mobile node following the transmission of said timing synchronization signal.

16. The method of claim 12, wherein said step of allocating a dedicated resource further includes allocating a device identifier;

and

wherein in addition to transmitting information about the dedicated set of tones, the second base station also transmits the device identifier to be used by said mobile node when communicating over the air with said second base station to said first base station.

17. The method of claim 12, further comprising:

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.

18. The method of claim 17, 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.

19. The method of claim 18, further comprising:

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.

20. 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:

transmitting high power narrowband signals on a periodic basis;

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

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

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 second base station transmits at least one of said high power narrowband signals;

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; and

transmitting to said mobile node, after receiving said timing control signal, a timing synchronization signal, prior to receiving user data from said mobile node.

21. The method of claim 20, wherein said high power narrowband signals are beacon signals having a known frequency relationship to the frequency band to be used by said mobile node to transmit signals to said second base station.

22. 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; and

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

wherein said second base station begins receiving IP packets directed to said mobile node from other network nodes, after transmitting said dedicated resource information to said mobile node and prior to transmitting said timing synchronization signal to said mobile node.

23. A second base station capable of performing mobile node handoff operations involving a handoff of a mobile node from a first base station having a first communications link with said mobile node to said second base station, the second base station comprising:

means for allocating a dedicated resource including a set of uplink tones to be used by said mobile node when establishing a second communications link with said second base station, said set of uplink tones being less than a full set of uplink tones which are used for communicating signals to said second base station;

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

means for receiving, on said dedicated set of uplink tones, a registration signal communicated over the air from said mobile node to said second base station; and

means for transmitting to said mobile node, after receiving said registration signal, a timing synchronization signal, prior to receiving user data from said mobile node.

24. The second base station of claim 23, further comprising:

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

25. The second base station of claim 24, further comprising:

means for receiving user data from said mobile node following the transmission of said power control signal and said timing synchronization signal.

26. The second base station of claim 24, wherein said timing control signal is a signal instructing the mobile node to advance or retard the transmission timing of symbols transmitted by said mobile node.

27. The second base station of claim 26, further comprising:

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 using said secure communications link.

28. A second base station capable of performing mobile node handoff operations involving a handoff of a mobile node from a first base station having a first communications link with said mobile node to said second base station, the second base station 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 on a communications link between said first and second base stations;

means for receiving a registration signal over the air from said mobile node;

means for transmitting to said mobile node, after receiving said registration signal, a timing synchronization signal, prior to receiving user data from said mobile node;

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 second base station transmits at least one of said high power narrowband signals.

29. The second base station of claim 28, wherein said high power narrowband signals are beacon signals having a known frequency relationship to the frequency band to be used by said mobile node to transmit signals to said second base station.

30. A second base station capable of performing mobile node handoff operations involving a handoff of a mobile node from a first base station having a first communications link with said mobile node to said second base station, the second base station 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 over a communications link between said first and second base stations;

means for receiving a registration signal over the air from said mobile node; and

means for transmitting to said mobile node, after receiving said registration signal, a timing synchronization signal, prior to receiving user data from said mobile node; and

wherein said second base station begins receiving IP packets directed to said mobile node from other network nodes, after transmitting said dedicated resource information to said mobile node and prior to transmitting said timing synchronization signal to said mobile node.

31. A method of operating a base station to implement a mobile node handoff between a first communications link with a first base station sector, said first communications link using a first carrier, and a second communications link with a second base station sector said second communications link using a second carrier, the first and second sectors being within the same base station, at least the first sector being different from the second sector or the first carrier being different from the second carrier, the method comprising:

operating receivers in said first and second sectors corresponding to said first and second carriers, respectively, to operate in a timing synchronized manner;

transmitting a timing correction signal to said mobile node over said first communications link;

receiving from the mobile node a signal communicated over said first communications link indicating an intent to handoff to said second communications link;

transmitting over said first communications link information indicating a dedicated resource to be used by said mobile when communicating over said second communications link;

terminating said first communications link with said mobile node; and

receiving from said mobile node at least one off user data and a non-timing control signal over said second communications link prior to transmitting a transmission timing control adjustment signal generated based on any timing control signal received over said second communications link from said mobile node.

32. The method of claim 31, wherein said transmission timing adjustment signal instructs the mobile node to adjust the time at which symbols are transmitted so that they arrive in a synchronized manner at the base station with symbols transmitted by other mobile nodes.

33. The method of claim 31, wherein said dedicated resource is an identifier specific to said second sector and said second carrier.

34. The method of claim 33, wherein said identifier is a device identifier to be used by said mobile node when communicating over said second communications link.

35. The method of claim 31, wherein said dedicated resource is a dedicated airlink communications segment to be used in establishing communications with said second base station sector when transmitting signals over the air to said second base station sector using said second carrier frequency to establish said second communications link.