Method for handover procedure of user terminal on radio interfaces, a base station and a network therefor

1. A method for a handover procedure of a user terminal on radio interfaces from a source base station (SBS) to a target base station the method comprising,

using the target base station, sending downlink transmission of u-plane user data to the user terminal before the target base station receives a message indicating termination of the handover procedure;

using the target base station, receiving at least one uplink feedback message associated to the downlink transmission of said u-plane user data from the user terminal, wherein the at least one uplink feedback message is an acknowledgment (ACK) or a negative acknowledgment (NACK) received from the user terminal independent of receipt of uplink u-plane user data from the user terminal; and

wherein the target base station uses said at least one message associated to the downlink transmission of said u-plane user data as an indication of the presence of the user terminal within the range of the target base station,

wherein the target base station sends u-plane user data to the user terminal after any uplink or downlink control L1/L2 signaling associated with the handover procedure and prior to reception of the message indicating the termination of the handover procedure; and

wherein the message indicating the termination of the handover procedure is one of an HO complete message and a Feedback (ACK/NACK) message.

2. A method according to claim 1 , wherein the identification of the user terminal in the target base station is transferred from the target base station to the source base station, which in turn transfers said identification to the user terminal.

3. A method according to claim 1 , wherein said u-plane user data are sent with modulation and coding schemes that are appropriate for poor radio conditions.

4. A method according to claim 1 , wherein if the target base station does not receive said at least one message associated to the downlink transmission of said u-plane user data or only receives said at least one message associated to the downlink transmission of said u-plane user data with a signal strength below a certain threshold, the target base station interprets that the user terminal is not yet receiving said downlink transmission of said u-plane user data.

5. A method according to claim 1 , wherein no message only indicating that the handover is complete is sent from the user terminal to the target base station.

6. A method according to claim 1 , wherein said at least one message associated to the downlink transmission of said u-plane user data is sent via a random access channel if the user terminal has not yet received any timing advance value from the target base station.

7. A method according to claim 1 , wherein the target base station indicates in a handover response message that is sent to the source base station at least one downlink resource that will be used for scheduling first user data to the user terminal.

8. A method according to claim 1 , wherein before a first transmission of u-plane user data from the target base station, the source base station sends a measurement report indicating radio channel quality of the user terminal to the target base station, and wherein the target base station selects an appropriate modulation and coding scheme for the u-plane user data based on said measurement report.

9. A base station in a network using radio transmission adapted for taking over a user terminal from another base station during a handover procedure, wherein said base station is operative to:

send downlink transmission of u-plane user data to the user terminal before reception of a message indicating termination of the handover procedure;

receive at least one uplink feedback message associated to downlink transmission of said u-plane user data from the user terminal, wherein the at least one uplink feedback message is an acknowledgment (ACK) or a negative acknowledgment (NACK) received from the user terminal independent of receipt of uplink u-plane user data from the user terminal; and

use said at least one uplink feedback message as an indication of the presence of the user terminal within a range of the base station;

the base station sends u-plane user data to the user terminal after any uplink or downlink control L1/L2 signaling associated with the handover procedure and prior to reception of the message indicating the termination of the handover procedure; and

wherein the message indicating the termination of the handover procedure is one of an HO complete message and a Feedback (ACK/NACK) message.

10. A network using radio transmission adapted for performing a handover procedure of a user terminal from a first base station to a second base station, wherein said network comprises at least one base station operative to:

send downlink transmission of u-plane user data to the user terminal before reception of a message indicating termination of the handover procedure;

receive at least one uplink feedback message associated to downlink transmission of said u-plane user data from the user terminal, wherein the at least one uplink feedback message is an acknowledgment (ACK) or a negative acknowledgment (NACK) received from the user terminal independent of receipt of uplink u-plane user data from the user terminal; and

to use said at least one uplink feedback message as an indication of the presence of the user terminal within a range of the base station;

wherein the at least one base station sends u-plane user data to the user terminal after any uplink or downlink control L1/L2 signaling associated with the handover procedure and prior to reception of the message indicating the termination of the handover procedure; and

wherein the message indicating the termination of the handover procedure is one of an HO complete message and a Feedback (ACK/NACK) message.

11. A method according to claim 1 , wherein the u-plane user data sent by the target base station to the user terminal before reception of the message indicating the termination of the handover procedure includes voice data.

12. A base station according to claim 9 , wherein the u-plane user data sent by the base station to the user terminal before reception of the message indicating the termination of the handover procedure includes voice data.

13. A network according to claim 10 , wherein the u-plane user data sent by the at least one base station to the user terminal includes voice data.

14. A method according to claim 1 , further comprising:

using the target base station, receiving a handover complete message after sending the u-plane user data to the user terminal, wherein the handover complete message is received independent of receipt of uplink u-plane user data from the user terminal.

15. A base station according to claim 9 , wherein said base station is operative to receive a handover complete message after sending the u-plane user data to the user terminal, wherein the handover complete message is received independent of receipt of uplink u-plane user data from the user terminal.

16. A network according to claim 10 , wherein the at least one base station is operative to receive a handover complete message after sending the u-plane user data to the user terminal, wherein the handover complete message is received independent of receipt of uplink u-plane user data from the user terminal.