HARQ feedback for unscheduled uplink

1. A method of operation of a network node in a cellular communications network to provide Hybrid Automatic Repeat Request (HARQ) feedback for autonomous uplink transmissions in an unlicensed spectrum, the method comprising:

receiving a plurality of autonomous uplink transmissions from a wireless device in the unlicensed spectrum; and

transmitting HARQ feedback for the plurality of autonomous uplink transmissions to the wireless device, the HARQ feedback comprising a bit map of a set of all HARQ processes configured for at least one cell and a corresponding bit acknowledgement mapped to each configured HARQ process, wherein the transmitting the HARQ feedback comprises:

transmitting the HARQ feedback using a shared maximum channel occupancy time scheme in which a portion of a maximum channel occupancy time for an uplink transmission from the wireless device is used for transmission by the network node; and

transmitting the HARQ feedback starting at an earliest subframe boundary within the shared maximum channel occupancy time after completion of the uplink transmission and performing a fast Listen Before Talk (LBT) procedure.

2. The method of claim 1 , further comprising:

determining that the network node has failed to decode data of one or more autonomous uplink transmissions from the wireless device; and

in response to the determination, requesting retransmission of the data via downlink control information (DCI).

3. The method of claim 1 , further comprising:

receiving an indication of a remaining duration of a maximum channel occupancy time (MCOT) from the wireless device; and

in response to receiving the indication, transmitting information to the wireless device during the remaining duration.

4. The method of claim 1 wherein transmitting the HARQ feedback comprises transmitting the HARQ feedback using a format selected from a group consisting of:

a format based on physical downlink control channel (PDCCH) or extended PDCCH (EPDCCH);

a format comprising a physical layer channel using one interlace for multiple signals;

a format comprising a physical layer channel using one interlace for multiple signals in a downlink partial subframe;

a format based on Physical HARQ Indicator Channel (PHICH);

a format based on PHICH in combination with bit compression to reduce a size of the bit map; and

a format based on an implicit ACK/NACK via Control Channel Element (CCE) indices of PDCCH transmissions sent to wireless devices for downlink scheduling where a time gap between an autonomous uplink transmission and a PDCCH transmission is 1 ms or more.

5. The method of claim 1 wherein, for each HARQ process, the corresponding bit acknowledgement indicates a NACK if the network node missed an autonomous uplink transmission from the wireless device on the HARQ process, or the network node failed to successfully decode an autonomous uplink transmission from the wireless device on the HARQ process.

6. The method of claim 1 , further comprising, if the network node ( 14 ) identifies an autonomous uplink transmission from the wireless device ( 12 ) and fails to successfully decode the identified autonomous uplink transmission, performing at least one of:

transmitting a request for retransmission using a dedicated uplink grant via PDCCH OR EPDCCH;

transmitting a NACK via common PDCCH (CPDCCH); and

transmitting a NACK via PHICH.

7. The method of claim 1 wherein the shared maximum channel occupancy time scheme utilizes: a shortened uplink transmission time interval (TTI) within a subframe to enable transmission of the HARQ feedback in a remainder of the subframe; or a timing advance for the uplink transmission such that a downlink channel in which the HARQ feedback is transmitted before a start of a next downlink subframe after completion of the uplink transmission.

8. The method of claim 1 wherein transmitting the HARQ feedback comprises multiplexing the HARQ feedback with a planned downlink transmission.

9. The method of claim 1 wherein transmitting the HARQ feedback comprises triggering a downlink transmission to transmit the HARQ feedback if a HARQ feedback has been pending for at least a predefined or preconfigured threshold amount of time.

10. A network node for a cellular communications network enabled to provide HARQ feedback for autonomous uplink transmissions in an unlicensed spectrum, the network node comprising:

at least one processor, memory and transceiver collectively configured to:

receive a plurality of autonomous uplink transmissions from a wireless device in the unlicensed spectrum; and

transmit HARQ feedback for the plurality of autonomous uplink transmissions to the wireless device, the HARQ feedback comprising a bit map of a set of all HARQ processes configured for at least one cell and a corresponding bit acknowledgement mapped to each configured HARQ process, wherein the transmitting the HARQ feedback comprises:

transmitting the HARQ feedback using a shared maximum channel occupancy time scheme in which a portion of a maximum channel occupancy time for an uplink transmission from the wireless device is used for transmission by the network node; and

transmitting the HARQ feedback starting at an earliest subframe boundary within the shared maximum channel occupancy time after completion of the uplink transmission and performing a fast Listen Before Talk (LBT) procedure.

11. A method of operation of a wireless device in a cellular communications network enabled to transmit autonomous uplink transmissions in an unlicensed spectrum, the method comprising:

performing autonomous uplink transmissions in the unlicensed spectrum for one or more HARQ processes;

receiving, from a network node, HARQ feedback comprising a bit map of a set of HARQ processes configured for at least one cell and a corresponding bit acknowledgement mapped to each configured HARQ process;

in response to determining that no HARQ feedback for a predetermined autonomous uplink transmission is received from the network node within a predetermined time period, retransmitting the predetermined autonomous uplink transmission;

using a timer to determine a number of subframes since an initial transmission of the predetermined autonomous uplink transmission; and

performing retransmission in response to the timer exceeding a configured threshold.

12. The method of claim 11 , further comprising:

determining a remaining duration of a maximum channel occupancy time (MCOT) of the wireless device;

transmitting an indication of a remaining duration of the MCOT to the network node; and

receiving information from the network node during the remaining duration.

13. The method of claim 11 wherein receiving the HARQ feedback comprises receiving the HARQ feedback via physical downlink control channel (PDCCH) or extended PDCCH (EPDCCH).

14. The method of claim 11 , further comprising:

transmitting an autonomous uplink transmission to the network node; and

receiving, from the network node via downlink control information (DCI), a request for retransmission of the autonomous uplink transmission.

15. The method of claim 11 wherein, for each HARQ process of the set of all HARQ processes, the corresponding bit acknowledgement indicates a NACK if the network node missed an autonomous uplink transmission from the wireless device on the HARQ process, or the network node ( 14 ) failed to successfully decode an autonomous uplink transmission from the wireless device on the HARQ process.

16. The method of claim 11 , further comprising receiving the HARQ feedback using a shared maximum channel occupancy time scheme in which a portion of a maximum channel occupancy time for an uplink transmission from the wireless device is used for transmission by the network node.

17. The method of claim 16 , further comprising receiving the HARQ feedback starting at an earliest subframe boundary within the shared maximum channel occupancy time after completion of the uplink transmission.

18. The method of claim 16 wherein the shared maximum channel occupancy time scheme utilizes a shortened uplink transmission time interval (TTI) within a subframe to enable transmission of the HARQ feedback in a remainder of the subframe.

19. The method of claim 16 wherein the shared maximum channel occupancy time scheme utilizes a timing advance for the uplink transmission such that a downlink channel in which the HARQ feedback is received before a start of a next downlink subframe after completion of the uplink transmission.

20. The method of claim 11 wherein transmitting the HARQ feedback comprises multiplexing the HARQ feedback with a planned downlink transmission.

21. A wireless device for a cellular communications network enabled to transmit autonomous uplink transmissions in an unlicensed spectrum, the wireless device comprising:

at least one processor, memory and transceiver collectively configured to:

perform autonomous uplink transmissions in the unlicensed spectrum for one or more HARQ processes;

receive, from a network node, HARQ feedback comprising a bit map of a set of all HARQ processes configured for at least one cell and a corresponding bit acknowledgement mapped to each configured HARQ process;

in response to determining that no HARQ feedback for a predetermined autonomous uplink transmission is received from the network node within a predetermined time period, retransmit the predetermined autonomous uplink transmission;

use a timer to determine a number of subframes since an initial transmission of the predetermined autonomous uplink transmission; and

perform retransmission in response to the timer exceeding a configured threshold.