System and method for retransmission of grant-free traffic
Feedback from a base station is used to reduce retransmissions of a grant-free UE where the SINR of an initial transmission from the grant-free UE is higher than a threshold. Feedback from a base station is also used to adjust transmission by grant-based UEs in resources that overlap with those also available to grant-free UEs.
1. A method comprising:
during a grant-free transmit time interval (TTI), a base station performing grant-free activity detection;
the base station transmitting a notification to adjust grant-based transmission based on a result of the grant-free activity detection.
2. The method of claim 1 wherein the base station transmitting a notification to adjust grant-based transmission comprises transmitting the notification when activity is detected.
3. The method of claim 1 wherein the notification to adjust grant-free transmission indicates that a grant-based UE configured to make a scheduled transmission using resources that include an area of overlap with resources for grant-free UEs is not to transmit in the area of overlap.
4. The method of claim 1 wherein performing activity detection comprises detecting at least one transmission by at least one grant-free UE with an indication that the at least one transmission will be retransmitted.
5. The method of claim 1 further comprising:
estimating an associated SINR of a detected activity;
wherein the base station transmits the notification to adjust grant-based transmission when activity is detected and the associated SINR is less than a threshold.
6. The method of claim 5 wherein the notification to adjust grant-based transmission indicates that a grant-based UE configured to make a scheduled transmission using resources that include an area of overlap with resources for grant-free UEs is not to transmit in the area of overlap.
7. The method of claim 1 wherein transmitting a notification comprises transmitting an indication of whether or not to adjust grant-based transmission for each of resource area of a plurality of resource areas within a grant-free frequency partition.
8. The method of claim 1 wherein transmitting a notification comprises using a dedicated downlink feedback channel.
9. The method of claim 1 wherein transmitting a notification comprises puncturing downlink transmissions.
10. The method of claim 1 wherein:
performing grant-free activity detection comprises determining whether a detected grant-free transmission is a grant-free transmission in respect of which at least one more retransmission is expected or is a retransmission in respect of which at least one further retransmission is expected; and
the base station transmits the notification to adjust grant-based transmission based on a result of the grant-free activity detection when it is determined that the detected grant-free transmission is a grant-free transmission in respect of which at least one further retransmission is expected, or a retransmission in respect of which at least one further retransmission is expected.
11. The method of claim 1 wherein for the purpose of generating the notification, performing grant-free activity detection comprises performing grant-free activity detection in respect of an uplink resource for an in initial grant-free transmission in respect of which one further retransmission is expected, or in respect of a resource for a retransmission in respect of which at least one further retransmission is expected.
12. A method comprising:
during a grant-free transmit time interval (TTI), a base station performing grant-free activity detection;
estimating an associated signal-to-interference-plus-noise ratio (SINR) of a detected activity;
the base station transmitting a notification to reduce grant-free retransmission based on a result of the grant-free activity detection when activity is detected and the associated SINR is greater than a threshold.
13. The method of claim 12 wherein transmitting a notification comprises using a dedicated downlink feedback channel.
14. The method of claim 12 wherein transmitting a notification comprises puncturing downlink transmissions.
15. The method of claim 12 further comprising:
as part of performing grant-free activity detection, determining whether a detected grant-free transmission is an initial transmission or a retransmission;
the base station transmitting the notification to reduce grant-free retransmission based on a result of the grant-free activity detection when it is determined that the detected grant-free transmission is an initial transmission or a retransmission in respect of which at least one further retransmission is expected.
16. The method of claim 12 wherein for the purpose of generating the notification, performing grant-free activity detection comprises performing grant-free activity detection in respect of uplink resources dedicated to initial grant-free transmissions, or in respect of uplink resources dedicated to retransmissions in respect of which at least one further retransmission is expected.