Receiving uplink data via a transmission time interval of an unlicensed cell

1. A method comprising:

receiving, by a wireless device, a downlink control information comprising:

an allocation of resource blocks for transmission of uplink data via a transmission time interval (TTI) of an unlicensed cell;

a first field comprising an index indicating a starting position for the transmission of the uplink data, the index identifying one of pre-configured starting positions; and

a second field indicating an ending symbol for the transmission of the uplink data, the ending symbol being one of pre-configured ending symbols;

performing, based on the starting position of the TTI, a listen-before-talk procedure indicating a clear channel; and

transmitting, the uplink data via the resource blocks of the unlicensed cell, based on the starting position and the ending symbol.

2. The method of claim 1 , wherein the transmitting the uplink data further comprises:

transmitting a reservation signal until an allowed symbol for a physical uplink shared channel transmission; and

transmitting data symbols starting from the allowed symbol.

3. The method of claim 2 , wherein a duration of the reservation signal is less than one symbol.

4. The method of claim 1 , wherein the starting position is based on a value of an uplink timing advance calculated by a wireless device.

5. The method of claim 1 , wherein the downlink control information comprises a listen-before-talk parameter.

6. The method of claim 1 , wherein the downlink control information comprises a transmit power control command.

7. The method of claim 1 , further comprising receiving uplink transmission parameters for the unlicensed cell.

8. The method of claim 1 , wherein the downlink control information indicates a starting time for the listen-before-talk procedure.

9. The method of claim 1 , wherein a starting time for the listen-before-talk procedure is at a pre-determined time before the starting position.

10. 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 a downlink control information comprising:

an allocation of resource blocks for transmission of uplink data via a transmission time interval (TTI) of an unlicensed cell;

a first field comprising an index indicating a starting position for the transmission of the uplink data, the index identifying one of pre-configured starting positions; and

a second field indicating an ending symbol for the transmission of the uplink data, the ending symbol being one of pre-configured ending symbols;

perform, based on the starting position of the TTI, a listen-before-talk procedure indicating a clear channel; and

transmit, the uplink data via the resource blocks of the unlicensed cell, based on the starting position and the ending symbol.

11. The wireless device of claim 10 , wherein the instructions, when transmitting the uplink data, further cause the wireless device to:

transmit a reservation signal until a first allowed symbol for a physical uplink shared channel transmission; and

transmit data symbols starting from the first allowed symbol.

12. The wireless device of claim 11 , wherein a duration of the reservation signal is less than one symbol.

13. The wireless device of claim 10 , wherein the starting position is based on a value of an uplink timing advance calculated by the wireless device.

14. The wireless device of claim 10 , wherein the downlink control information comprises a listen-before-talk parameter.

15. The wireless device of claim 10 , wherein the downlink control information comprises a transmit power control command.

16. The wireless device of claim 10 , wherein configuration parameters for the unlicensed cell comprise uplink transmission parameters.

17. The wireless device of claim 10 , wherein the downlink control information indicates a starting time for the listen-before-talk procedure.

18. The wireless device of claim 10 , wherein a starting time for the listen-before-talk procedure is at a pre-determined time before the starting position.