Uplink transmissions in an unlicensed spectrum

1. A method for uplink transmission by a user equipment (UE), comprising:

receiving an uplink grant for data transmission on an uplink channel, wherein the uplink grant includes a resource block assignment to a resource block from an eNodeB for a channel reservation signal;

determining the resource block for sending a channel, usage beacon signal (CUBS) over a contention-based spectrum based on the resource block assignment included in the uplink grant, wherein the CUBS reserves the uplink channel for the data transmission and indicates that the data transmission will follow in a subsequent subframe according to the resource block assignment; and

transmitting, in response to a successful clear channel assessment on the uplink channel, the CUBS in the subframe that directly precedes the subsequent subframe on which the data transmission follows, wherein transmitting the CUBS comprises transmitting a fractional CUBS (F-CUBS) having a fractional symbol duration on only a subset of all available tones of the resource block;

wherein

the resource block is determined based on the resource block assignment for the channel reservation signal on a condition that the subframe is not a special subframe used for transition from a set of downlink subframes to a set of uplink subframes; and

the resource block is determined based on the resource block assignment received in the uplink grant on a condition that the subframe is the special subframe.

2. The method of claim 1 , further comprising:

detecting a second uplink grant that includes a second resource block assignment to a second resource block in the subframe; wherein

the second resource block is determined based on the second resource block assignment included in the second uplink grant.

3. The method of claim 1 , further comprising:

monitoring for a second uplink grant with a second resource block assignment to a second resource block in the subframe;

wherein

the second resource block is determined based on the second resource block assignment received in the second uplink grant, and

the second resource block is determined based on the second resource block assignment for the channel reservation signal on a condition that a second uplink grant is not received.

4. The method of claim 3 , wherein

the second resource block assignment for the channel reservation signal is shared with other UEs.

5. The method of claim 1 , wherein

the resource block assignment for the channel reservation signal is shared with other UEs.

6. The method of claim 1 , wherein the CUBS is transmitted unaligned with a symbol boundary in the subframe responsive to receiving the clear channel assessment at a time unaligned with the symbol boundary.

7. The method of claim 1 , further comprising transmitting a plurality of additional CUBS to occupy all symbols between a symbol at the time of receiving the clear channel assessment and a next subframe boundary.

8. The method of claim 7 , wherein the plurality of additional CUBS includes at least one CUBS assigned to the subset of tones and at least one CUBS assigned to all tones of a resource block interlace.

9. The method of claim 1 , further comprising determining an uplink transmission synchronization boundary based on a first uplink subframe among all RB assignments received by the UE.

10. The method of claim 1 , further comprising determining an uplink transmission synchronization boundary based on every first uplink subframe following one or more uplink subframes not having an RB assignment.

11. A user equipment (UE), comprising:

a processor;

a memory coupled to the processor, the memory including instructions executable by the processor to:

receive an uplink grant for data transmission on an uplink channel, wherein the uplink grant includes a resource block assignment to a resource block from an eNodeB for a channel reservation signal; and

determine the resource block for sending a channel usage beacon signal (CUBS) over a contention-based spectrum based on the resource block assignment included in the uplink grant, wherein the CUBS reserves the uplink channel for the data transmission by indicating that the UE is sending the data transmission in a subsequent subframe according to the resource block assignment; and

a transmitter configured to transmit, in response to a successful clear channel assessment on the uplink channel, the CUBS in the subframe that directly precedes the subsequent subframe on which the data transmission follows, wherein transmitting the CUBS comprises transmitting a fractional CUBS (F-CUBS) having a fractional symbol duration on only a subset of all available tones of the resource block;

wherein

the resource block is determined based on the resource block assignment for the channel reservation signal on a condition that the subframe is not a special subframe used for transition from a set of downlink subframes to a set of uplink subframes; and

the resource block is determined based on the resource block assignment received in the uplink grant on a condition that the subframe is the special subframe.

12. The apparatus of claim 11 , wherein the instructions are further executable by the processor to:

detect a second uplink grant that includes a second resource block assignment to a second resource block in the subframe; wherein

determine the second resource block based on the second resource block assignment included in the second uplink grant.

13. The apparatus of claim 11 , wherein the instructions are further executable by the processor to:

monitor for a second uplink grant with a second resource block assignment to a second resource block in the subframe;

wherein

the second resource block is determined based on the second resource block assignment received in the second uplink grant, and

the second resource block is determined based on the second resource block assignment for the channel reservation signal on a condition that a second uplink grant is not received.

14. The apparatus of claim 13 , wherein

the second resource block assignment for the channel reservation signal is shared with other UEs.

15. The apparatus of claim 11 , wherein

the resource block assignment for the channel reservation signal is shared with other UEs.

16. The apparatus of claim 11 , wherein the CUBS is transmitted unaligned with a symbol boundary in the subframe responsive to receiving the clear channel assessment at a time unaligned with the symbol boundary.

17. The apparatus of claim 11 , wherein the instructions are further executable by the processor to:

transmit a plurality of additional CUBS to occupy all symbols between a symbol at the time of receiving the clear channel assessment and a next subframe boundary.

18. The apparatus of claim 17 , wherein the plurality of additional CUBS includes at least one CUBS assigned to the subset of tones and at least one CUBS assigned to all tones of a resource block interlace.

19. The apparatus of claim 11 , wherein the instructions are further executable by the processor to:

determine an uplink transmission synchronization boundary based on a first uplink subframe among all RB assignments received by the UE.

20. The apparatus of claim 11 , wherein the instructions are further executable by the processor to:

determine an uplink transmission synchronization boundary based on every first uplink subframe following one or more uplink subframes not having an RB assignment.

21. An apparatus for uplink transmission by a user equipment (UE), comprising:

means for receiving an uplink grant for data transmission on an uplink channel, wherein the uplink grant includes a resource block assignment to a resource block from an eNodeB for a channel reservation signal;

means for determining the resource block for sending a channel usage beacon signal (CUBS) over a contention-based spectrum based on the resource block assignment included in the uplink grant, wherein the CUBS reserves the uplink channel for the data transmission by indicating that the UE is sending the data transmission in a subsequent subframe according to the resource block assignment; and

means for transmitting, in response to a successful clear channel assessment on, the uplink channel, the CUBS in, the subframe that directly precedes the subsequent subframe for on which the data transmission follows, wherein transmitting the CUBS comprises transmitting a fractional CUBS (F-CUBS) having a fractional symbol duration on only a subset of all available tones of the resource block;

wherein

the resource block is determined based on the resource block assignment for the channel reservation signal on a condition that the subframe is not a special subframe used for transition from a set of downlink subframes to a set of uplink subframes; and,

the resource block is determined based on the resource block assignment received in the uplink grant on a condition that the subframe is the special subframe.

22. A computer-readable medium for allocating resources for an uplink transmission, comprising instructions executable by a processor for:

receiving an uplink grant for data transmission on an uplink channel, wherein the uplink grant includes a resource block assignment to a resource block from an eNodeB for a channel reservation signal;

determining the resource block for sending a channel usage beacon signal (CUBS) over a contention-based spectrum based on the resource block assignment included in the uplink grant, wherein the CUBS reserves the uplink channel for the data transmission by indicating that the UE is sending the data transmission in a subsequent subframe according to the resource block assignment; and

transmitting, in response to a successful clear channel assessment on the uplink channel, the CUBS in the subframe that directly precedes the subsequent subframe on which the data transmission follows, wherein transmitting the CUBS comprises transmitting a fractional CUBS (F-CUBS) having a fractional symbol duration on only a subset of all available tones of the resource block;

wherein

the resource block is determined based on the resource block assignment for the channel reservation signal on a condition that the subframe is not a special subframe used for transition from a set of downlink subframes to a set of uplink subframes; and

the resource block is determined based on the resource block assignment received in the uplink grant on a condition that the subframe is the special subframe.

23. The computer-readable medium of claim 22 , further comprises instructions executable by a processor for:

detecting a second uplink grant that includes a second resource block assignment to a second resource block in the subframe; wherein

the second resource block is determined based on the second resource block assignment included in the second uplink grant.

24. The computer-readable medium of claim 22 , further comprises instructions executable by a processor for:

monitoring for a second uplink grant with a second resource block assignment to a second resource block in the subframe;

wherein

the second resource block is determined based on the second resource block assignment received in the second uplink grant, and

the second resource block is determined based on the second resource block assignment for the channel reservation signal on a condition that a second uplink grant is not received.

25. The computer-readable medium of claim 24 , wherein

the second resource block assignment for the channel reservation signal is, shared with other UEs.

26. The computer-readable medium of claim 22 , wherein

the resource block assignment for the channel reservation signal is shared with other UEs.

27. The computer-readable medium of claim 22 , wherein the CUBS is transmitted unaligned with a symbol boundary in the subframe responsive to receiving the clear channel assessment at a time unaligned with the symbol boundary.

28. The computer-readable medium of claim 22 , further comprises instructions executable by a processor for:

transmitting a plurality of additional CUBS to occupy all symbols between a symbol at the time of receiving the clear channel assessment and a next subframe boundary.

29. The computer-readable medium of claim 22 , wherein the plurality of additional CUBS includes at least one CUBS assigned to the subset of tones and at least one CUBS assigned to all tones of a resource block interlace.

30. The computer-readable medium of claim 22 , further comprises instructions executable by a processor for:

determining an uplink transmission synchronization boundary based on a first uplink subframe among all RB assignments received by the UE.