Contention window size update for NR systems operating on unlicensed band
Systems and methods of adjusting contention window size (CWS) in a LBT procedure for both UL and DL unlicensed spectrum transmissions are described. The UE makes a HARQ-ACK determination for at least one code block group (CBG) of a transport block (TB) in a reference burst from a base station, determines whether the HARQ-ACK determination for the CBG meets a predetermined number of NACKs, transmits to the base station a single bit HARQ-ACK feedback for the TB that is dependent on whether the predetermined number of NACKs has been met, and receives or determines the adjusted CWS and uses the adjusted CWS for communication with the base station.
1. An apparatus comprising:
at least one processor configured to cause a user equipment (UE) to:
transmit one or more physical uplink shared channel (PUSCH) transmissions to a base station in an unlicensed spectrum in a reference burst, wherein the one or more PUSCH transmissions include transport blocks (TBs) comprised of a plurality of code block groups (CBGs);
determine Hybrid Automatic Repeat Request Acknowledgment (HARQ-ACK) information for the plurality of CBGs in the reference burst, wherein determining incudes counting negative ACKs (NACKs) or ACKs from each CBG of the plurality of CBGs individually for each of the transport blocks, and when an uplink grant does not indicate a toggled new data indicator (NI) for a HARQ process, a value of “1” in a code block group transmit information corresponds to a NACK;
determine whether the HARQ-ACK information for the at least one CBG meets a predetermined number of NACKs;
use an adjusted contention window (CW) size for a listen-before talk (LBT) procedure for uplink communications with the base station in the unlicensed spectrum, the adjusted CW size based on the HARQ-ACK information.
2. The apparatus of claim 1 , wherein:
the reference burst is a predetermined time that starts from a beginning of an uplink burst containing the reference burst, and
the predetermined time is independent of subcarrier spacing.
3. The apparatus of claim 1 , wherein:
the reference burst starts from a beginning of an uplink burst containing the reference burst,
and
the reference burst is independent of subcarrier spacing.
4. The apparatus of claim 1 , wherein the CWS is reset to the minimum value when the maximum CWS is used for K consecutive LBT attempts for transmission only for the priority class for which maximum CWS is used for K consecutive LBT attempts, where K is selected by UE.
5. The apparatus of claim 1 , wherein PUSCH transmissions used for CWS adjustment includes only a set of PUSCHs within the reference burst.
6. The apparatus of claim 1 , wherein PUSCH transmissions used for CWS adjustment includes only a set of PUSCHs with a starting symbol in the within the reference burst.
7. The apparatus of claim 1 , wherein PUSCH transmissions used for CWS adjustment includes only the earliest PUSCH in the reference burst.
8. A user equipment (UE), comprising:
wireless communication circuitry;
at least one processor; and
at least one memory medium storing program instructions executable by the at least one processor to cause the UE to:
transmit one or more physical uplink shared channel (PUSCH) transmissions to a base station in an unlicensed spectrum in a reference burst, wherein the one or more PUSCH transmissions include transport blocks (TBs) comprised of a plurality of code block groups (CBGs);
determine Hybrid Automatic Repeat Request Acknowledgment (HARQ-ACK) information for the plurality of CBGs in the reference burst, wherein determining incudes counting negative ACKs (NACKs) or ACKs from each CBG of the plurality of CBGs individually for each of the transport blocks, and when an uplink grant does not indicate a toggled new data indicator (NI) for a HARQ process, a value of “1” in a code block group transmit information corresponds to a NACK;
determine whether the HARQ-ACK information for the at least one CBG meets a predetermined number of NACKs; and
use an adjusted contention window (CW) size for a listen-before talk (LBT) procedure for uplink communications with the base station in the unlicensed spectrum, the adjusted CW size based on the HARQ-ACK information.
9. The UE of claim 8 , wherein:
the reference burst is a predetermined time that starts from a beginning of an uplink burst containing the reference burst, and
the predetermined time is independent of subcarrier spacing.
10. The UE of claim 8 , wherein:
the reference burst starts from a beginning of an uplink burst containing the reference burst, and
the reference burst is independent of subcarrier spacing.
11. The UE of claim 8 , wherein the CWS is reset to the minimum value when the maximum CWS is used for K consecutive LBT attempts for transmission only for the priority class for which maximum CWS is used for K consecutive LBT attempts, where K is selected by UE.
12. The UE of claim 8 , wherein PUSCH transmissions used for CWS adjustment includes only a set of PUSCHs within the reference burst.
13. The UE of claim 8 , wherein PUSCH transmissions used for CWS adjustment includes only a set of PUSCHs with a starting symbol in the within the reference burst.
14. The UE of claim 8 , wherein PUSCH transmissions used for CWS adjustment includes only the earliest PUSCH in the reference burst.
15. A non-transitory, computer accessible memory medium storing program instructions executable by at least one processor of a user equipment (UE) to cause the UE to:
transmit one or more physical uplink shared channel (PUSCH) transmissions to a base station in an unlicensed spectrum in a reference burst, wherein the one or more PUSCH transmissions include transport blocks (TBs) comprised of a plurality of code block groups (CBGs);
determine Hybrid Automatic Repeat Request Acknowledgment (HARQ-ACK) information for the plurality of CBGs in the reference burst, wherein determining incudes counting negative ACKs (NACKs) or ACKs from each CBG of the plurality of CBGs individually for each of the transport blocks, and when an uplink grant does not indicate a toggled new data indicator (NI) for a HARQ process, a value of “1” in a code block group transmit information corresponds to a NACK;
determine whether the HARQ-ACK information for the at least one CBG meets a predetermined number of NACKs; and
use an adjusted contention window (CW) size for a listen-before talk (LBT) procedure for uplink communications with the base station in the unlicensed spectrum, the adjusted CW size based on the HARQ-ACK information.
16. The non-transitory, computer accessible memory medium of claim 15 , wherein:
the reference burst is a predetermined time that starts from a beginning of an uplink burst containing the reference burst, and
the predetermined time is independent of subcarrier spacing.
17. The non-transitory, computer accessible memory medium of claim 15 , wherein:
the reference burst starts from a beginning of an uplink burst containing the reference burst, and
the reference burst is independent of subcarrier spacing.
18. The non-transitory, computer accessible memory medium of claim 15 , wherein the CWS is reset to the minimum value when the maximum CWS is used for K consecutive LBT attempts for transmission only for the priority class for which maximum CWS is used for K consecutive LBT attempts, where K is selected by UE.
19. The non-transitory, computer accessible memory medium of claim 15 , wherein PUSCH transmissions used for CWS adjustment includes only a set of PUSCHs within the reference burst.
20. The non-transitory, computer accessible memory medium of claim 15 , wherein PUSCH transmissions used for CWS adjustment includes only a set of PUSCHs with a starting symbol in the within the reference burst.