Carrier grouping in multicarrier wireless networks

1. A method comprising:

a) transmitting, by a base station to a wireless device, at least one first radio resource control (RRC) message to cause in said wireless device:

i) configuration of a plurality of cells comprising a primary cell and at least one secondary cell; and

ii) assignment of a cell group index to a cell in said plurality of cells, said cell group index identifying a cell group in a plurality of cell groups, said plurality of cell groups comprising:

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

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

b) transmitting, by said base station to said wireless device, at least one second RRC message to modify a first cell group index of a first cell in said wireless device, wherein:

i) if said first cell is said primary cell, said at least one second RRC message is configured to cause said wireless device to reconfigure said primary cell as a secondary cell with an updated first cell group index different from said first cell group index, said at least one second RRC message comprising mobility control information; and

ii) if said first cell is a secondary cell, said at least one second RRC message configured to cause said wireless device to release said secondary cell and add said secondary cell with an updated first cell group index different from said first cell group index, said at least one second RRC message not comprising mobility control information.

2. The method of claim 1 , wherein:

a) uplink transmissions by said wireless device in said primary cell group employ a first synchronization signal transmitted on said primary cell as a primary timing reference; and

b) uplink transmissions in said secondary cell group employ a second synchronization signal on an activated secondary cell in said secondary cell group as a secondary timing reference.

3. The method of claim 1 , wherein each cell in said plurality of cells comprises a downlink carrier.

4. The method of claim 1 , wherein a physical cell identifier of a cell is broadcast employing a synchronization signal transmitted on said cell.

5. The method of claim 4 , wherein said synchronization signal comprises a primary synchronization signal and a secondary synchronization signal.

6. The method of claim 1 , wherein said at least one second RRC message with mobility control information causes, in said wireless device, the cell category of said first cell to change from a primary cell to a secondary cell.

7. The method of claim 1 , wherein said at least one second RRC message with mobility control information causes, in said wireless device, the cell category of a cell in said at least one secondary cell to change from a secondary cell to a new primary cell.

8. The method of claim 7 , further comprising initiating a random access process with said base station in said wireless device if said at least one second RRC message comprising mobility control information.

9. A base station comprising:

a) one or more communication interfaces;

b) one or more processors; and

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

i) transmit to a wireless device at least one first radio resource control (RRC) message configured to cause in said wireless device:

(1) configuration of a plurality of cells comprising a primary cell and at least one secondary cell; and

(2) assignment of a cell group index to a cell in said plurality of cells, said cell group index identifying a cell group in a plurality of cell groups, said plurality of cell groups comprising a primary cell group and a secondary cell group; and

ii) transmit to said wireless device at least one second RRC message to modify a first cell group index of a first cell in said wireless device, wherein:

(1) if said first cell is said primary cell, said at least one second RRC message is configured to cause said wireless device to reconfigure said primary cell as a secondary cell with an updated first cell group index different from said first cell group index, said at least one second RRC message comprising mobility control information; and

(2) if said first cell is a secondary cell, said at least one second RRC message configured to cause said wireless device to release said secondary cell and add said secondary cell with an updated first cell group index different from said first cell group index, said at least one second RRC message not comprising mobility control information.

10. The base station of claim 9 , wherein:

a) said primary cell group 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 cell group employing a first synchronization signal transmitted on said primary cell as a primary timing reference; and

b) said secondary cell group comprising a second subset of said at least one secondary cell, uplink transmissions in said secondary cell group employing a second synchronization signal on an activated secondary cell in said secondary cell group as a secondary timing reference.

11. The base station of claim 9 , wherein a physical cell identifier of a cell is broadcast employing a synchronization signal transmitted on said cell.

12. The base station of claim 11 , wherein said synchronization signal comprises a primary synchronization signal and a secondary synchronization signal.

13. The base station of claim 9 , wherein said at least one second RRC message with mobility control information causes, in said wireless device, the cell category of said first cell to change from a primary cell to a secondary cell for said wireless device.

14. The base station of claim 9 , wherein said at least one second RRC message with mobility control information causes, in said wireless device, the cell category of a cell in said at least one secondary cell to change from a secondary cell to a new primary cell.

15. A method comprising:

a) receiving, by a wireless device from a base station, at least one first radio resource control (RRC) message to cause in said wireless device:

i) configuration of a plurality of cells comprising a primary cell and at least one secondary cell; and

ii) assignment of a cell group index to a cell in said plurality of cells, said cell group index identifying a cell group in a plurality of cell groups, said plurality of cell groups comprising a primary cell group and a secondary cell group; and

b) receiving, by said wireless device from said base station, at least one second RRC message to modify a first cell group index of a first cell in said wireless device, wherein:

i) if said first cell is said primary cell, said at least one second RRC message is configured to cause said wireless device to reconfigure said primary cell as a secondary cell with an updated first cell group index different from said first cell group index, said at least one second RRC message comprising mobility control information; and

ii) if said first cell is a secondary cell, said at least one second RRC message configured to cause said wireless device to release said secondary cell and add said secondary cell with an updated first cell group index different from said first cell group index, said at least one second RRC message not comprising mobility control information.

16. The method of claim 15 , wherein:

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

b) said secondary cell group comprises a second subset of said at least one secondary cell, uplink transmissions in said secondary cell group employing a second synchronization signal on an activated secondary cell in said secondary cell group as a secondary timing reference.

17. The method of claim 15 , wherein said at least one first RRC message is configured to further cause in said wireless device configuration of a time alignment timer for each of said plurality of cell groups.

18. The method of claim 15 , further comprising starting a random access process with said base station if said at least one second RRC message comprises mobility control information.

19. The method of claim 15 , further comprising starting, by said wireless device, a synchronization process with said base station if said at least one second RRC message comprises mobility control information.

20. The method of claim 15 , further comprising transmitting, by said wireless device to said base station, a random access preamble to said base station if said at least one second RRC message comprises mobility control information.