Methods and apparatus for facilitating robust forward handover in long term evolution (LTE) communication systems

1. A method for facilitating a forward handover in a communications system, comprising:

establishing, by a user terminal, a connection with a first base station of a first cell, the connection including a Radio Resource Control Connected (RRC_Connected) state and a data connected state;

storing at the user terminal first identity information associated with the connection to the first cell, the identity information comprising a Physical Cell Identity (PCI) and a Cell Radio Network Temporary Identifier (C-RNTI);

selecting, by the user terminal, a second base station of a second cell based on a first criterion determined by the user terminal;

initiating, at the user terminal, a forward handover to the second base station of the second cell;

receiving, at the user terminal, second identity information associated with the second cell;

re-establishing the RRC_Connected state with the second base station;

declaring, by the user terminal, a Radio Link Failure (RLF) between re-establishment of the RRC_Connected state and completion of establishment of the connection to the second base station, based on a second criterion determined by the user terminal; and

initiating, by the user terminal, reestablishment of the connection with a third base station of a third cell using the first identity information.

2. The method of claim 1 , wherein the declaring RLF occurs before completion of an RRCConnectionReconfiguration procedure.

3. The method of claim 1 , wherein the third base station is a different base station from the first base station and the second base station.

4. The method of claim 1 , wherein the third base station and the first base station are the same base station.

5. The method of claim 1 , further comprising:

receiving, at the user terminal, third identity information associated with the third cell;

declaring, by the user terminal, a second RLF associated with the third base station between establishment of the RRC_Connected state with the third base station and completion of establishment of the connection to the third base station; and

reestablishing the connection with a fourth base station of a fourth cell using the first identity information.

6. The method of claim 5 , further comprising:

disregarding the third identity information received during the re-establishment of the RRC_Connected state with the third base station.

7. A computer program product comprising a non-transitory computer-readable medium including codes executable by a processor of a user terminal to:

establish a connection with a first base station of a first cell, the connection including a Radio Resource Control Connected (RRC_Connected) state and a data connected state;

store first identity information associated with the connection to the first cell, the identity information comprising a Physical Cell Identity (PCI) and a Cell Radio Network Temporary Identifier (C_RNTI);

select a second base station of a second cell based on a first criterion determined by the user terminal;

initiate a forward handover to the second base station of the second cell;

receive second identity information associated with the second cell;

re-establish the RRC_Connected state with the second base station;

declare a Radio Link Failure (RLF) between re-establishment of the RRC_Connected state and completion of establishment of the connection to the second base station, based on a second criterion determined by the user terminal; and

initiate reestablishment of the connection with a third base station of a third cell using the first identity information.

8. A user terminal, comprising:

a processor module configured to establish, in conjunction with a receiver module and a transmitter module, a connection with a first base station of a first cell, the connection including a Radio Resource Control Connected (RRC_Connected) state and a data connected state;

a module configured to store first identity information associated with the connection to the first cell, the identity information comprising a Physical Cell Identity (PCI) and a Cell Radio Network Temporary Identifier (C_RNTI);

wherein the processor module is further configured to select a second base station of a second cell based on a first criterion and

the transmitter module, in conjunction with the processor module, is further configured to initiate a forward handover with the second base station of the second cell;

wherein the processor module is further configured to declare, in conjunction with the receiver module, a Radio Link Failure (RLF) between establishment of the RRC_Connected state and completion of establishment of the connection to the second base station, based on a second criterion; and

wherein the transmitter module is further configured to initiate reestablishment of the connection with a third base station of a third cell using the first identity information and first user terminal information subsequent to the declaration of RLF.

9. The communications device of claim 8 , wherein the declaring RLF occurs before completion of an RRCConnectionReconfiguration procedure.

10. A user terminal, comprising:

means for establishing a connection with a first base station of a first cell, the connection including a Radio Resource Control Connected (RRC_Connected) state and a data connected state;

means for storing first identity information associated with the connection to the first cell, the identity information comprising a Physical Cell Identity (PCI) and a Cell Radio Network Temporary Identifier (C_RNTI);

means for selecting a second base station of a second cell based on a first criterion determined by the user terminal;

means for initiating a forward handover between the user terminal and the second base station of the second cell;

means for receiving second identity information associated with the second cell;

means for re-establishing the RRC_Connected state with the second base station;

means for declaring a Radio Link Failure (RLF) between re-establishment of the RRC_Connected state and completion of establishment of the connection to the second base station, based on a second criterion determined by the user terminal; and

means for initiating reestablishment of the connection with a third base station of a third cell using the first identity information.

11. A method for facilitating a forward handover in a communications system, comprising:

establishing, at a user terminal, a connection with a source base station of a source cell, the connection including a Radio Resource Control Connected (RRC_Connected) state and a data connected state;

storing at the user terminal, first identity information associated with the connection with the source cell, the first identity information comprising a Physical Cell Identity (PCI) and a Cell Radio Network Temporary Identifier (C-RNTI);

selecting, by the user terminal, a target base station of a target cell based on a first criterion determined by the user terminal;

sending, from the user terminal to the target base station, a connection reestablishment request including the first identity information for retrieval of user context information stored at the source base station;

receiving, at the user terminal, a message from the target base station informing the user terminal to continue the connection process without performing a Random Access Channel (RACH) procedure; and

sending, from the user terminal, a connection request message to the target base station, without performing a RACH procedure with the target base station, subsequent to receipt of the message.

12. The method of claim 11 , wherein the connection request message is an RRCConnectionRequest message.

13. The method of claim 11 , further comprising receiving, from the target base station, a connection setup message.

14. A computer program product comprising a non-transitory computer-readable medium including codes executable by a processor of a user terminal to:

establish a connection with a source base station of a source cell, the connection including a Radio Resource Control Connected (RRC_Connected) state and a data connected state;

store first identity information associated with the connection with the source cell, the first identity information comprising a Physical Cell Identity (PCI) and a Cell Radio Network Temporary Identifier (C-RNTI);

select a target base station of a target cell based on a first criterion determined by the user terminal;

send to the target base station, a connection reestablishment request including first identity information for retrieval of user context information stored at a source base station;

receive, from the target base station, a message informing the user terminal to continue the connection process without performing a Random Access Channel (RACH) procedure; and

send a connection request message to the target base station, without performing a RACH procedure with the target base station, subsequent to receipt of the message.

15. A user terminal, comprising:

a processor module configured to

establish a connection with a source base station of a source cell, the connection including a Radio Resource Control Connected (RRC_Connected) state and a data connected state,

store first identity information associated with the source cell, the first identity information comprising a Physical Cell Identity (PCI) and a Cell Radio Network Temporary Identifier (C-RNTI), and

select a target base station of a target cell based on a first criterion determined by the user terminal;

a transmitter module configured to send to the target base station, a connection reestablishment request including the first identity information for retrieval of user context information stored at the source base station; and

a receiver module configured to receive, from the target base station, a message informing the user terminal to continue the connection process without performing a Random Access Channel (RACH) procedure; wherein the transmitter module is further configured to send a connection request message to the target base station without performing a RACH procedure with the target base station subsequent to receipt of the message.

16. A user terminal, comprising:

means for establishing a connection with a source base station of a source cell, the connection including a Radio Resource Control Connected (RRC_Connected) state and a data connected state;

means for storing first identity information associated with the source cell, the first identity information comprising a Physical Cell Identity (PCI) and a Cell Radio Network Temporary Identifier (C-RNTI);

means for selecting a target base station of a target cell based on a first criterion determined by the user terminal;

means for sending to the target base station, a connection reestablishment request including first identity information for retrieval of user context information stored at a source base station;

means for receiving, from the target base station, a message informing the user terminal to continue the connection without performing a Random Access Channel (RACH) procedure; and

means for sending a connection request message to the target base station, without performing a RACH procedure with the target base station, subsequent to receipt of the message.