Method and apparatus for performing handover and re-establishment of connections

1. A method, comprising:

detecting, by a user equipment having dual connectivity with a first network entity and a second network entity, that a signaling strength of the first network entity has dropped below a threshold, wherein Radio-Resource-Control (RRC) configuration information related to the first network entity and the second network entity are communicated with the user equipment via a RRC connection established between the user equipment and the first network entity;

transmitting a measurement report to the first network entity;

receiving from the first network entity, radio-resource-control reconfiguration information indicating a time advance value being in use by the second network entity for on-going connections between the user equipment and the second network entity; and

using the time advance value to perform a handover of the RRC connection during the dual connectivity, from the first network entity to the second network entity network without involving a random-access-channel procedure.

2. The method according to claim 1 , wherein the first network entity comprises a master evolved-Node-B, and the second network entity comprises a secondary evolved-Node-B.

3. The method according to claim 1 , wherein the receiving comprises receiving mobility information.

4. The method according to claim 3 , wherein the timing-advance value corresponds to a timing-advance value of a cell of the second network entity.

5. An apparatus having dual connectivity with a. first network entity and a second network entity, comprising:

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured, with the at least one processor, to cause the apparatus at least to

detect that a signaling strength of the first network entity has dropped below a threshold, wherein Radio-Resource-Control (RRC) configuration information related to the first network entity and the second network entity are communicated with the user equipment via a RRC connection established between the user equipment and the first network entity;

transmit a measurement report to the first network entity;

receive from the first network entity, radio-resource-control reconfiguration information indicating a time advance value being in use by the second network entity for on-going connections between the user equipment and the second network entity; and

use the time advance value to perform a handover of the RRC connection during the dual connectivity, from the first network entity to the second network entity without involving a random-access-channel procedure.

6. The apparatus according to claim 5 , wherein the first network entity comprises a master evolved-Node-B, and the second network entity comprises a secondary evolved-Node-B.

7. The apparatus according to claim 5 , wherein the receiving comprises receiving mobility information.

8. The apparatus according to claim 7 , wherein the timing-advance value corresponds to a timing-advance value of a cell of the second network entity.

9. A method, comprising:

receiving, by a first network entity, a measurement report from a user equipment having dual connectivity with the first network entity and a second network entity, wherein Radio-Resource-Control (RRC) configuration information related to the first network entity and the second network entity are communicated with the user equipment via a RRC connection established between the user equipment and the first network entity;

determining to handover a radio-resource-control connection from the first network entity to the second network entity;

performing handover preparation with the second network entity;

retrieving a timing advance value from the second network entity, wherein the time advance value being in use by the second network entity for on-going connections between the user equipment and the second network entity; and

transmitting radio-resource-control reconfiguration information to the user equipment, wherein the radio-resource-control reconfiguration information comprises the timing advance value and mobility information.

10. The method according to claim 9 , wherein the first network entity comprises a master evolved-Node-B, and the second network entity comprises a secondary evolved-Node-B.

11. The method according to claim 9 , wherein the timing-advance value corresponds to a timing-advance value of a cell of the second network entity.

12. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured, with the at least one processor, to cause the apparatus at least to

receive a measurement report from a user equipment having dual connectivity with the a apparatus and a network entity wherein Radio-Resource-.Control RRC configuration information related to the apparatus and the network entity are communicated with the user equipment via a RRC connection established between the user equipment and the apparatus;

determine to handover the radio-resource-control connection from the apparatus to the network entity;

perform handover preparation with the network entity;

retrieve a timing advance value from the network entity, wherein the time advance value being in use by the network entity for on-going connections between the user equipment and the network entity; and

transmit radio-resource-control reconfiguration information to the user equipment, wherein the radio-resource-control reconfiguration information comprises the timing advance value and mobility information.

13. The apparatus according to claim 12 , wherein the apparatus comprises a master evolved-Node-B, and the network entity comprises a secondary evolved-Node-B.

14. The apparatus according to claim 12 , wherein the timing-advance value corresponds to a timing-advance value of a cell of the network entity.

15. A method, comprising:

performing, by a second network entity, handover preparation with a first network entity for a user equipment having dual connectivity with the first network entity and the second network entity;

transmitting a timing advance value to the first network entity, wherein the time advance value is in use by the second network en n-going connections between the user equipment and the second network entity; and

receiving a scheduling request by the user equipment during the dual connectivity, wherein a random-access-channel procedure is avoided.

16. The method according to claim 15 , wherein the first network entity comprises a master evolved-Node-B, and the second network entity comprises a secondary evolved-Node-B.

17. The method according to claim 15 , wherein the performing comprises transmitting mobility information.

18. The method according to claim 15 , wherein the timing-advance value corresponds to a timing-advance value of a cell of the second network entity.

19. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured, with the at least one processor, to cause the apparatus at least to

perform handover preparation with a network entity for a user equipment having dual connectivity with the us and the network entity;

transmit a timing advance value to the network entity, wherein the time advance value is in use by the apparatus for on-going connections between the user equipment and the apparatus; and

receive a scheduling request by the user equipment during the dual connectivity, wherein a random-access-channel procedure is avoided.

20. The apparatus according to claim 19 , wherein the network entity comprises a master evolved-Node-B, and the apparatus comprises a secondary evolved-Node-B.

21. The apparatus according to claim 19 , wherein the performing comprises transmitting mobility information.

22. The apparatus according to claim 19 , wherein the timing-advance value corresponds to a timing-advance value of a cell of the apparatus.