Uplink procedures for LTE/LTE-A communication systems with unlicensed spectrum

• US 10,187,875 B2
• Filed: 07/24/2017
• Issued: 01/22/2019
• Est. Priority Date: 08/16/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Chen, Wanshi, Gaal, Peter, Malladi, Durga Prasad, Luo, Tao, Ji, Tingfang, Bhushan, Naga, Wei, Yongbin, Damnjanovic, Aleksandar
• Primary Examiner(s): Duong, Christine T
• Application Number:
  US15/658,160
• Publication Number:
  US 20170325201A1
• Time in Patent Office: 547 Days
• Field of Search: None
• CPC Class Codes: H04L 27/0006 Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio for spectrum sharing between different networks H04W16/14
• CPC Class Codes: H04L 5/001 the frequencies being arranged in component carriers
• CPC Class Codes: H04L 5/003 Arrangements for allocating sub-channels of the transmission path
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 72/04 Wireless resource allocation
• CPC Class Codes: H04W 72/1215 for collaboration of different radio technologies
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access

Abstract

Long term evolution (LTE)/LTE-Advanced (LTE-A) deployments with unlicensed spectrum leverage more efficient LTE communication aspects over unlicensed spectrum, such as over WIFI radio access technology. In order to accommodate such communications, various uplink procedures may be modified in order to handle communications between licensed and unlicensed spectrum with LTE/LTE-A deployments with unlicensed spectrum.

Claims

1. A method of wireless communication, comprising:

generating, at a user equipment (UE), a random access request, wherein the UE is configured to transmit communication signals to a serving base station over at least unlicensed spectrum and to receive communication signals from the serving base station;

determining, by the UE, a non-clear channel assessment (non-CCA) subframe and a CCA subframe of the unlicensed spectrum;

transmitting, by the UE, the random access request to the serving base station in the non-CCA subframe over a first carrier of one or more carriers operated in a cell serviced by the serving base station; and

monitoring the one or more carriers, by the UE, for a random access response to the random access request for connecting to the cell.

2. The method of claim 1, wherein the receiving the communication signals is over the at least unlicensed spectrum.

3. The method of claim 1, wherein the transmitting the random access request includes:

multiplexing the random access request in frequency with one or more other random access requests from one or more neighboring UEs, wherein the multiplexing is performed over a system bandwidth of the cell.

4. The method of claim 3, wherein the transmitting the random access request further includes:

multiplexing the random access request in code with one or more additional random access requests from one or more additional neighboring UEs in a same frequency as the random access request.

5. The method of claim 1, wherein the transmitting the random access request includes:

multiplexing the random access request in code with one or more additional random access requests from one or more additional neighboring UEs in a same frequency as the random access request.

6. The method of claim 1, further including:

determining a transmission state of the base station; and

determining whether or not to perform a re-transmission of the random access request in response to the transmission state.

7. The method of claim 6, wherein the transmission state consists of at least one of a capable state, or an incapable state, and in response to the transmission state, determining one of:

suspending re-transmitting the random access request when the transmission state indicates the base station has been incapable of sending the random access response;

or

re-transmitting the random access request when the transmission state indicates the base station has been capable of sending the random access response.

8. The method of claim 6, further including:

detecting expiration of a re-transmission time gap without receiving the random access response;

in response to the transmission state, determining one of;

extending the re-transmission time gap when the transmission state indicates the base station has been incapable of sending the random access response;

or

re-transmitting the random access request when the transmission state indicates the base station has been capable of sending the random access response.

9. The method of claim 6, wherein the determining the transmission state includes:

monitoring, by the UE, for one or more reference signals transmitted by the base station;

determining an incapable transmission state when the UE fails to detect the one or more reference signals;

determining a capable transmission state when the UE detects the one or more reference signals; and

determining a capable transmission state when the UE detects a non-CCA subframe.

10. The method of claim 9, wherein the one or more reference signals include one or more of:

a channel usage pilot signal (CUPS);

a channel usage beacon signal (CUBS),

a cell-specific reference signal (CRS); and

a channel state information reference signals (CSI-RS).

11. The method of claim 1, further including:

determining, at the UE, that the UE has been in an idle mode for at least a predetermined period,

wherein the transmitting the random access request is transmitted on one of;

a CCA subframe or non-CCA subframe without performing a CCA check.

12. The method of claim 11, further including:

determining a mismatch of an offset for guaranteed transmission based on the transmitting the random access request without performing the CCA check; and

adjusting the offset according to the mismatch.

13. The method of claim 11, further including:

detecting a non-CCA subframe for guaranteed transmission;

determining the non-CCA subframe is within a restricted transmission period from the transmitting the random access request without performing the CCA check; and

skipping the guaranteed transmission for the non-CCA subframe based on the determining.

14. The method of claim 1, wherein the random access request occupies a fraction of a subframe.

15. The method of claim 14, wherein the fraction of a subframe includes one or more symbols in a single slot.

16. A method of wireless communication, comprising:

identifying, by a base station, a non-clear channel assessment (non-CCA) subframe and a CCA subframe of unlicensed spectrum;

receiving, at the base station, a random access request from a user equipment (UE) in the non-CCA subframe over a first carrier of one or more carriers operated in a cell serviced by the base station, wherein the base station is configured to receive communication signals from the UE over at the least unlicensed spectrum and transmit communication signals to the UE;

generating a random access response, in response to the random access request; and

directing transmission of the random access response to the UE over another carrier of one or more carriers.

17. The method of claim 16, wherein the transmitting the communication signals to the UE is performed over at least the unlicensed spectrum.

18. The method of claim 16, wherein the transmission of the random access response occurs in an unlicensed band over one of:

the non-CCA subframe;

or

the a CCA subframe.

19. The method of claim 16, wherein the random access request occupies a fraction of a subframe.

20. The method of claim 19, wherein the fraction of a subframe includes one or more symbols in a single shot.

21. An apparatus configured for wireless communication, the apparatus comprising:

at least one processor; and

a memory coupled to the at least one processor,

wherein the at least one processor is configured to;

generate, at a user equipment (UE), a random access request, wherein the UE is configured to transmit communication signals to a serving base station over at least unlicensed spectrum and receive communication signals from the serving base station;

determine, by the UE, a non-clear channel assessment (non-CCA) subframe and a CCA subframe of the unlicensed spectrum;

transmit, by the UE, the random access request to the serving base station in the non-CCA subframe over a first carrier of one or more carriers operated in a cell serviced by the serving base station; and

monitor the one or more carriers, by the UE, for a random access response to the random access request for connecting to the cell.

22. The apparatus of claim 21, wherein the at least one processor is further configured to:

determine a transmission state of the base station; and

determine whether or not to perform a re-transmission of the random access request in response to the transmission state.

23. The apparatus of claim 22, wherein the transmission state consists of at least one of a capable state, or an incapable state, and wherein the at least one processor is further configured to, in response to the transmission state, determine one of:

suspending re-transmitting the random access request when the transmission state indicates the base station has been incapable of sending the random access response;

or

re-transmitting the random access request when the transmission state indicates the base station has been capable of sending the random access response.

24. The apparatus of claim 22, wherein the at least one processor is further configured to:

detect expiration of a re-transmission time gap without receiving the random access response;

in response to the transmission state, determine one of;

extending the re-transmission time gap when the transmission state indicates the base station has been incapable of sending the random access response;

or

re-transmitting the random access request when the transmission state indicates the base station has been capable of sending the random access response.

25. The apparatus of claim 22, wherein the configuration of the at least one processor to determine the transmission state includes configuration of the at least one processor to:

monitor, by the UE, for one or more reference signals transmitted by the base station;

determine an incapable transmission state when the UE fails to detect the one or more reference signals;

determine a capable transmission state when the UE detects the one or more reference signals; and

determine a capable transmission state when the UE detects a non-CCA subframe.

26. The apparatus of claim 25, wherein the one or more reference signals include one or more of:

a channel usage pilot signal (CUPS);

a channel usage beacon signal (CUBS),

a cell-specific reference signal (CRS); and

a channel state information reference signals (CSI-RS).

27. The apparatus of claim 21, wherein the random access request occupies a fraction of a subframe.

28. An apparatus configured for wireless communication, the apparatus comprising:

at least one processor; and

a memory coupled to the at least one processor,

wherein the at least one processor is configured to;

identify, by a base station, a non-clear channel assessment (non-CCA) subframe and a CCA subframe of unlicensed spectrum;

receive, at a base station, a random access request from a user equipment (UE) in the non-CCA subframe over a first carrier of one or more carriers operated in a cell serviced by the base station, wherein the base station is configured to receive communication signals from the UE over at least unlicensed spectrum and transmit communication signals to the UE;

generate a random access response, in response to the random access request; and

direct transmission of the random access response to the UE over another carrier of one or more carriers.

29. The apparatus of claim 28, wherein the random access request occupies a fraction of a subframe.

30. The apparatus of claim 29, wherein the fraction of a subframe includes one or more symbols in a single slot.