Synchronization of unlicensed cell reception of a wireless device
A wireless device receives at least one control message comprising configuration parameters of a plurality of cells comprising two or more unlicensed cells comprising a first unlicensed cell and a second unlicensed cell. The wireless device synchronizes a reception timing of the first unlicensed cell employing at least a second received signal of the second unlicensed cell.
1. A wireless device comprising:
one or more processors; and
memory storing instructions that, when executed by the one or more processors, cause the wireless device to:
receive at least one control message comprising configuration parameters of a plurality of cells grouped into a plurality of cell groups, wherein the plurality of cell groups comprise:
a primary cell group comprising a primary cell; and
a secondary cell group comprising two or more unlicensed cells comprising a first unlicensed cell and a second unlicensed cell;
receive, via the first unlicensed cell, a first signal in a first plurality of subframes, the first signal comprising a first downlink synchronization signal;
receive, via the second unlicensed cell, a second signal in a second plurality of subframes, the second signal comprising a second downlink synchronization signal;
synchronize reception timing of signals received via the first unlicensed cell employing at least the second signal received via the second unlicensed cell; and
synchronize reception timing of signals received via the second unlicensed cell employing at least the first signal received via the first unlicensed cell.
2. The wireless device of claim 1 , wherein the second received signal comprises a synchronization signal.
3. The wireless device of claim 1 , wherein the second received signal comprises a discovery signal.
4. The wireless device of claim 1 , wherein the second received signal comprises a reference signal.
5. The wireless device of claim 1 , wherein:
uplink transmission timing in the first cell group is derived employing the primary cell.
6. The wireless device of claim 1 , wherein the at least one control message configures a cell group comprising the first unlicensed cell and the second unlicensed cell.
7. The wireless device of claim 1 , wherein a cell group is configured at least for downlink synchronization.
8. The wireless device of claim 1 , wherein at least one of the two or more unlicensed cells is a licensed assisted access (LAA) cell.
9. The wireless device of claim 1 , wherein a transmission of the second received signal is subject to a listen before talk (LBT) mechanism.
10. A method comprising:
receiving, by a wireless device, at least one control message comprising configuration parameters of a plurality of cells grouped into a plurality of cell groups, wherein the plurality of cell groups comprise:
a primary cell group comprising a primary cell;
a secondary cell group comprising two or more unlicensed cells comprising a first unlicensed cell and a second unlicensed cell; and
receiving, via the first unlicensed cell, a first signal in a first plurality of subframes, the first signal comprising a first downlink synchronization signal;
receiving, via the second unlicensed cell, a second signal in a second plurality of subframes, the second signal comprising a second downlink synchronization signal;
synchronizing reception timing of signals received via the first unlicensed cell employing at least the second signal received via the second unlicensed cell; and
synchronizing reception timing of signals received via the second unlicensed cell employing at least the first signal received via the first unlicensed cell.
11. The method of claim 10 , wherein the second received signal comprises a synchronization signal.
12. The method of claim 10 , wherein the second received signal comprises a discovery signal.
13. The method of claim 10 , wherein the second received signal comprises a reference signal.
14. The method of claim 10 , wherein
uplink transmission timing in the first cell group derived employing the primary the primary cell.
15. The method of claim 10 , wherein the at least one control message configures a cell group comprising the first unlicensed cell and the second unlicensed cell.
16. The method of claim 10 , wherein a cell group is configured at least for downlink synchronization.
17. The method of claim 10 , wherein an unlicensed cell is a licensed assisted access (LAA) cell.
18. The method of claim 10 , wherein a transmission of the second received signal is subject to a listen before talk (LBT) mechanism.