Adaptive HARQ timing relaxation

1. A method of controlling a Hybrid Automatic Repeat Request, HARQ, retransmission round-trip time for transmission in a wireless network, the method comprising:

estimating one or more latency related transmission parameters;

selecting one or more of a plurality of predefined HARQ relaxation techniques based on the estimated one or more latency related transmission parameters; and

scheduling transmission using the selected one or more HARQ relaxation techniques;

wherein the method further comprises:

determining if spatial multiplexing is available for the transmission; and

selecting one or more predefined HARQ relaxation techniques based on the determined availability of spatial multiplexing and the estimated latency related transmission parameters.

2. The method of claim 1 , wherein the transmission is an FDD-mode transmission.

3. The method of claim 1 , wherein the method is performed in a wireless access node arranged to schedule uplink and/or downlink transmission to a wireless device.

4. The method of claim 1 , wherein the plurality of predefined HARQ relaxation techniques comprises increasing a HARQ round-trip time by:

disabling HARQ retransmission;

disabling at least every other HARQ retransmission opportunity for each HARQ process;

postponing HARQ retransmission until receipt of explicit retransmission grant; and/or

alternating HARQ transmission between at least two transport blocks during a spatial multiplexing mode.

5. The method of claim 4 , wherein estimating the one or more latency related transmission parameters comprises:

estimating cell load; and

estimating channel quality.

6. The method of claim 5 , wherein estimating channel quality comprises estimating an uplink channel quality and wherein selecting one or more of the plurality of predefined HARQ relaxation techniques comprises selecting to increase a HARQ round-trip time by disabling at least every other HARQ retransmission opportunity when the uplink channel quality is estimated to be below a predetermined signal-to-noise and interference ratio (SINR) or when the uplink channel quality is estimated to be above the predetermined SINR while the uplink cell load is above a predefined high load.

7. The method of claim 6 , wherein estimating cell load comprises estimating an uplink cell load and wherein selecting one or more of the plurality of predefined HARQ relaxation techniques comprises selecting to increase a IIARQ round-trip time by disabling HARQ retransmission when the estimated uplink cell load is below a predefined low load and uplink channel quality is estimated to be above a predetermined SINR.

8. The method of claim 5 , wherein estimating channel quality comprises estimating a downlink channel quality and wherein selecting one or more of the plurality of predefined HARQ relaxation techniques comprises selecting to increase a HARQ round-trip time by alternating HARQ retransmission between two spatially multiplexed transport blocks when the downlink cell load is below a predefined low load and the downlink channel quality is estimated to be above a predetermined signal-to-noise and interference ratio (SINR).

9. The method of claim 5 , wherein estimating cell load comprises estimating a downlink cell load and wherein selecting one or more of the plurality of predefined HARQ relaxation techniques comprises selecting to increase a HARQ round-trip time by disabling at least every other HARQ retransmission opportunity when the downlink cell load is above a predefined high load.

10. The method according to claim 1 , wherein the method is performed at each scheduling opportunity for the wireless device.

11. The method of claim 7 , wherein estimating cell load comprises estimating an average cell load filtered over time.

12. The method of claim 5 , wherein estimating channel quality comprises estimating an achievable signal-to-noise and interference ratio (SINR) for a given resource allocation.

13. A network node comprising:

a processor operative to control a Hybrid Automatic Repeat Request, HARQ, retransmission round-trip time for transmission in a wireless network, the processor further adapted to:

estimate one or more latency related transmission parameters;

select one or more of plurality of predefined HARQ relaxation techniques based on the estimated one or more latency related transmission parameters; and

schedule transmission using the selected one or more HARQ relaxation techniques;

wherein the processor further adapted to:

determine if spatial multiplexing is available for the transmission; and

select one or more predefined HARQ relaxation techniques based on the determined availability of spatial multiplexing and the estimated latency related transmission parameters.

14. The network node of claim 13 , further comprising a memory, wherein said memory contains instructions executable by said processor.

15. The network node of claim 14 , wherein the network node is a wireless access node arranged to schedule uplink and/or downlink transmission to a wireless device.

16. A network node comprising:

a processor; and

a memory coupled to the processor and storing program code that when executed by the processor cause the processor to:

estimate one or more latency related transmission parameter(s);

select a predefined HARQ relaxation technique; and

schedule transmission using the selected HARQ relaxation technique;

wherein the processor further adapted to:

determine if spatial multiplexing is available for the transmission; and

select one or more predefined HARQ relaxation techniques based on the determined availability of spatial multiplexing and the estimated latency related transmission parameters.

17. The network node of claim 16 , wherein the network node is a wireless access node arranged to schedule uplink and/or downlink transmission to a wireless device.

18. A non-transitory computer-readable storage medium, having stored thereon a computer program which, when run in a network node, causes the network node to perform the method as disclosed in claim 1 .