FAST RADIO LINK RECOVERY AFTER HANDOVER FAILURE

• US 20100279695A1
• Filed: 01/03/2008
• Published: 11/04/2010
• Est. Priority Date: 01/03/2008
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Amirijoo, Sharokh, Nordstrand, Ingrid Viola
• Granted Patent: US 8,504,046 B2
• Time in Patent Office: Days
• US Class Current: 455/438
• CPC Class Codes: H04W 36/0079 in case of hand-off failure or rejection
• CPC Class Codes: H04W 74/08 Non-scheduled access, e.g. ALOHA hybrid access H04W74/02

Abstract

A radio connection is supported between the mobile station and a source base station associated with a source cell. The mobile station transmits information to the source base station over a shared uplink data communications channel used by multiple mobiles. A handover message is received from the source base station indicating that the source base station has initiated a handover of the radio connection over to a target base station for the target base station to support the radio connection. The handover fails. In response, a message is sent from the mobile station to the source base station requesting that the source base station continue to support the radio connection without requiring the mobile station to perform a radio channel procedure competing with other mobile stations requesting a new radio connection be supported by the source base station.

Claims

1. A method implemented in a mobile station where a radio connection is supported between the mobile station and a source base station associated with a source cell, where uplink radio connection communications are performed using a shared uplink data communications channel shared by multiple mobile stations, the method comprising:

transmitting information to the source base station over the shared uplink data communications channel;

receiving a handover message from the source base station indicating that the source base station has initiated a handover of the radio connection over to a target base station for the target base station to support the radio connection;

detecting that the attempted handover failed; and

sending a message to the source base station requesting that the source base station continue to support the radio connection.

2. The method in claim 1, further comprising:

determining that a predetermined time period has expired before the message is sent, and

requesting that the connection with the source base station be re-established.

3. The method in claim 2, further comprising:

before sending the message to the source base station, determining whether the mobile station is synchronized with the source base station, and if so, sending the message,

wherein the predetermined time period is associated with a synchronization time period.

4. The method in claim 3, wherein the synchronization time period is associated with an uplink timing alignment adjustment received from the source base station after sending an uplink transmission to the source base station

5. The method in claim 2, wherein if the predetermined time period has expired, the mobile station performs a random access procedure to request resources to re-establish the connection on the shared uplink radio channel.

6. The method in claim 2, wherein if the predetermined time period has not expired, the mobile station sends a scheduling request to the source base station, and after receiving an uplink transmission grant from the source base station, the mobile station sends the message to the source base station requesting that the source base station continue to support the radio connection.

7. A method implemented in a source base station where a radio connection is established between a mobile station and the source base station associated with a source cell, where uplink radio connection communications are performed using a shared uplink data communications channel shared by multiple mobile stations, the method comprising:

receiving information from the mobile station;

initiating a handover for the radio connection to a target base station for the target base station to take over support of the radio connection;

sending a handover command to the mobile station indicting initiation of a handover of the radio connection over to the target base station;

detecting that the handover failed;

receiving a message from the mobile station within a predetermined time period requesting that the source base station continue to support the radio connection without requiring the mobile station to perform a radio channel procedure competing with other mobile stations requesting a new radio connection be supported by the source base station; and

continuing to support the radio connection.

8. The method in claim 7, wherein uplink radio transmission resources are allocated using persistent scheduling, semi-persistent scheduling, or non-persistent scheduling.

9. The method in claim 7, further comprising:

sending a timing alignment message to the mobile station just before sending the handover message.

10. The method in claim 7, further comprising:

after the handover failure, receiving from the mobile station a scheduling request, and in response, sending an uplink transmission grant to the mobile station and thereafter receiving the message from the mobile station.

11. The method in claim 7, further comprising:

reserving scheduling request (SR) resources at a first time periodicity for the mobile station to request uplink transmission resources over the shared uplink data communications channel, and

reconfiguring the reserved SR resources to a second shorter time periodicity just before or during the initiated handover.

12. The method in claim 7, wherein the handover command is included in an RRC Connection Reconfiguration and the message is an RRC Connection Reconfiguration Failure message.

13. A mobile station for communicating over a radio connection supported between the mobile station and a source base station associated with a source cell, where uplink radio connection communications are performed using a shared uplink data communications channel shared by multiple mobile stations, the mobile station comprising:

a radio transmitter for transmitting information to the source base station over the shared uplink data communications channel,

a radio receiver for receiving a handover message from the source base station indicating that the source base station has initiated a handover of the radio connection over to a target base station for the target base station to support the radio connection, and

electronic circuitry configured to;

detect that the attempted handover failed; and

generate a message to be transmitted to the source base station via the transmitter requesting that the source base station continue to support the radio connection.

14. The mobile station in claim 13, wherein the electronic circuitry is configured to:

determine that a predetermined time period has expired before the message is sent, and

send a request via the transmitter that the radio connection be re-established with the source base station.

15. The mobile station in claim 14, wherein the electronic circuitry is configured to determine, before sending the message to the source base station, whether the mobile station is synchronized with the source base station, and if so, to send the message,

wherein the predetermined time period is associated with a synchronization time period.

16. The mobile station in claim 15, wherein the synchronization time period is associated with an uplink timing alignment adjustment received from the source base station after sending an uplink transmission to the source base station.

17. The mobile station in claim 15, wherein if the predetermined time period has expired, the electronic circuitry is configured to perform a random access procedure to request resources to re-establish the connection on the shared uplink radio channel.

18. The mobile station in claim 15, wherein if the predetermined time period has not expired, the mobile station sends a scheduling request to the source base station, and after receiving an uplink transmission grant from the source base station, the electronic circuitry is configured to send the message to the source base station requesting that the source base station continue to support the radio connection.

19. A source base station where a radio connection is established between a mobile station and the source base station associated with a source cell, where uplink radio connection communications are performed using a shared uplink data communications channel shared by multiple mobile stations, the base station comprising:

a radio receiver for receiving information from the mobile station;

a connection processor configured to initiate a handover for the radio connection to a target base station for the target base station to take over support of the radio connection; and

a radio transmitter for sending a handover command to the mobile station indicting initiation of a handover of the radio connection over to the target base station, wherein the connection processor is configured to;

detect that the attempted handover failed, and

continue to support the radio connection based on a message received from the mobile station requesting that the source base station continue to support the radio connection without requiring the mobile station to perform a radio channel procedure competing with other mobile stations requesting a new radio connection be supported by the source base station.

20. The base station claim 19, wherein the connection processor is configured to allocate uplink radio transmission resources using persistent scheduling, semi-persistent scheduling, or non-persistent scheduling.

21. The base station claim 19, wherein the connection processor is configured to send a timing message to the mobile station via the radio transmitter just before sending the handover message.

22. The method in claim 19, wherein after the handover failure and receiving from the mobile station a scheduling request, the connection processor is configured to send an uplink transmission grant to the mobile station and thereafter receive the message from the mobile station.

23. The method in claim 19, wherein the connection processor is configured to:

reserve scheduling request (SR) resources at a first time periodicity for the mobile station to request uplink transmission resources over the shared uplink data communications channel, and

reconfigure the reserved SR resources to a second shorter time periodicity just before or during the initiated handover.