Handover signalling in wireless networks

1. A method comprising:

a) receiving, by a serving base station from a wireless device on a primary cell in a plurality of cells, a first message comprising at least one parameter indicating whether said wireless device supports configuration of a plurality of timing advance groups (TAGs);

b) selectively transmitting at least one second message to said wireless device by said serving base station if said at least one parameter indicates support for configuration of said plurality of TAGs, said at least one second control message to cause in said wireless device:

i) configuration of at least one secondary cell in said plurality of cells; and

ii) assignment of each of said at least one secondary cell to a TAG in a first plurality of TAGs, said first plurality of TAGs comprising:

(1) a primary TAG comprising a first subset of said plurality of cells, said first subset comprising said primary cell, uplink transmissions by said wireless device in said primary TAG employing a first synchronization signal transmitted on said primary cell as a primary timing reference; and

(2) a secondary TAG comprising a second subset of said at least one secondary cell, uplink transmissions in said secondary TAG employing a second synchronization signal on an activated secondary cell in said secondary TAG as a secondary timing reference; and

c) transmitting, by said serving base station to at least one target base station, at least one third message in response to said serving base station making a handover decision, said at least one third message comprising at least one of:

i) said at least one parameter indicating whether said wireless device supports configuration of said plurality of TAGs; and

ii) configuration information of said first plurality TAGs.

2. The method of claim 1 , wherein said at least one second control message comprises measurement parameters.

3. The method of claim 1 , wherein said at least one second control message is configured to further cause said wireless device to measure signal quality of at least one carrier of one or more of said at least one target base station.

4. The method of claim 3 , further comprising receiving, by said serving base station from said wireless device, at least one measurement report in response to said at least one second control message, said at least one measurement report comprising signal quality information of at least one of said at least one carrier, said signal quality information derived at least in part employing measurements of at least one OFDM subcarrier.

5. The method of claim 1 , wherein said at least one parameter further indicates whether said wireless device supports configuration of said plurality of TAGs for each of one or more band combinations supported by said wireless device.

6. The method of claim 1 , wherein said at least one second control message is to further cause in said wireless device configuration of a time alignment timer for each of said first plurality of TAGs, said time alignment timer starting or restarting in response to said wireless device receiving a timing advance command to adjust uplink transmission timing of a commanded TAG in said first plurality of TAGs.

7. The method of claim 1 , wherein said at least one second control message comprises a media access control dedicated information element comprising a sequence of at least one first information element, each of said at least one first information element comprising: a first TAG index of a first secondary TAG; and a first time alignment timer value for said first secondary TAG.

8. The method of claim 1 , wherein said at least one second control message comprises at least one cell add-modify information element, each of said at least one cell add-modify information element comprising a first plurality of dedicated parameters, said first plurality of dedicated parameters comprising a first cell index for a first secondary cell in said at least one secondary cell.

9. A method comprising:

a) receiving, by a serving base station from a wireless device on a primary cell in a plurality of cells, a first message comprising at least one parameter indicating whether said wireless device supports configuration of a plurality of timing advance groups (TAGs);

b) selectively transmitting at least one second message to said wireless device by said serving base station if said at least one parameter indicates support for configuration of said plurality of TAGs, said at least one second control message to cause in said wireless device:

i) configuration of at least one secondary cell in said plurality of cells; and

ii) assignment of each of said at least one secondary cell to a TAG in a first plurality of TAGs, said first plurality of TAGs comprising:

(1) a primary TAG comprising a first subset of said plurality of cells, said first subset comprising said primary cell; and

(2) a secondary TAG comprising a second subset of said at least one secondary cell; and

c) transmitting, by said serving base station to at least one target base station, at least one third message in response to said serving base station making a handover decision, said at least one third message comprising at least one of:

i) said at least one parameter indicating whether said wireless device supports configuration of said plurality of TAGs; and

ii) configuration information of said first plurality TAGs.

10. The method of claim 9 , wherein said at least one second control message comprises measurement parameters.

11. The method of claim 9 , wherein said at least one second control message is configured to further cause said wireless device measuring signal quality of at least one carrier of one or more of said at least one target base station.

12. The method of claim 11 , further comprising receiving, by said serving base station from said wireless device, at least one measurement report comprising signal quality information of at least one of said at least one carrier, said signal quality information derived at least in part employing measurements of at least one OFDM subcarrier.

13. The method of claim 9 , wherein said at least one parameter further indicates whether said wireless device supports configuration of said plurality of TAGs for each of one or more band combinations supported by said wireless device.

14. The method of claim 9 , wherein said at least one second control message:

a) further comprises configuration information for physical channels for said wireless device; and

b) is configured to further cause said wireless device to set up or modify at least one radio bearer.

15. A serving base station comprising:

a) one or more communication interfaces;

b) one or more processors; and

c) memory storing instructions that, when executed, cause said serving base station to:

i) receive a first message from a wireless device on a primary cell in a plurality of cells, said first message comprising at least one parameter indicating whether said wireless device supports configuration of a plurality of timing advance groups (TAGs);

ii) selectively transmit at least one second message to said wireless device if said at least one parameter indicates support for configuration of said plurality of TAGs, said at least one second control message to cause in said wireless device:

(1) configuration of at least one secondary cell in said plurality of cells; and

(2) assignment of each of said at least one secondary cell to a TAG in a first plurality of TAGs, said first plurality of TAGs comprising:

(a) a primary TAG comprising a first subset of said plurality of cells, said first subset comprising said primary cell; and

(b) a secondary TAG comprising a second subset of said at least one secondary cell; and

iii) transmit in response to said serving base station making a handover decision, at least one third message to at least one target base station, said at least one third message comprising at least one of:

(1) said at least one parameter indicating whether said wireless device supports configuration of said plurality of TAGs; and

(2) configuration information of said first plurality TAGs.

16. The serving base station of claim 15 , wherein said at least one second control message is to further cause in said wireless device configuration of a time alignment timer for each of said first plurality of TAGs, said time alignment timer starting or restarting in response to said wireless device receiving a timing advance command to adjust uplink transmission timing of a commanded TAG in said first plurality of TAGs.

17. The serving base station of claim 15 , wherein said at least one second control message comprises a media access control dedicated information element comprising a sequence of at least one first information element, each of said at least one first information element comprising: a first TAG index of a first secondary TAG; and a first time alignment timer value for said first secondary TAG.

18. The serving base station of claim 15 , wherein said at least one second control message comprises at least one cell add-modify information element, each of said at least one cell add-modify information element comprising a first plurality of dedicated parameters, said first plurality of dedicated parameters comprising a first cell index for a first secondary cell in said at least one secondary cell.

19. The serving base station of claim 15 , wherein one of said at least one second control message is to further cause said wireless device to configure at least one of: a physical layer parameter; a MAC layer parameter; and an RLC layer parameter.

20. The serving base station of claim 15 , wherein one of said at least one second control message comprises radio resource configuration parameters comprising physical channel configuration parameters.