HARQ Feedback Mirroring for Wireless Scheduling
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Solution Overview
Problem
In wireless communication networks, particularly in LTE systems, there is uncertainty about whether a missed ACK/NACK is due to the UE's failure to receive the downlink grant or the network's failure to receive the ACK/NACK, leading to sub-optimal scheduling of retransmissions and difficulties in determining which downlink assignments the UE has received, especially in dynamically scheduled systems.
Innovation Solution
Incorporating mirrored information, such as the New Data Indicator (NDI) and/or Redundancy Version (RV), along with the ACK/NACK status in HARQ feedback from the UE to the network, allowing the network to better understand the HARQ RX state and avoid unnecessary retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the network uses conventional HARQ feedback without mirrored information, then the feedback channel remains simple, but the network cannot determine whether a missed ACK/NACK is due to UE failure to receive downlink grant or network failure to receive ACK/NACK
Solution Approach 1:
The patent applies the copying principle by having the UE mirror copy fields from the downlink grant message (such as NDI and RV fields) and include them in the uplink HARQ feedback message. This allows the network to compare the original grant values with the mirrored values in feedback to determine whether the feedback itself was lost or whether the UE failed to receive the grant, thereby resolving the information loss without significantly increasing complexity.
2Productivity
If the network implements sub-optimal retransmission scheduling due to uncertainty about missed ACK/NACK causes, then scheduling simplicity is maintained, but retransmission efficiency deteriorates
Solution Approach 1:
The patent implements an enhanced feedback mechanism where the UE includes mirrored grant information (NDI, RV fields) in the HARQ feedback message. This feedback allows the network to accurately determine whether a missed ACK/NACK was caused by UE failure to receive the downlink grant or by network failure to receive the feedback, enabling optimized retransmission scheduling decisions and improving retransmission efficiency without excessive complexity.
3Reliability
If the network does not receive mirrored information in HARQ feedback, then the feedback processing remains simple, but link adaptation for PDCCH/ePDCCH cannot be improved
Solution Approach 1:
The patent uses the copying principle to resolve this contradiction by having the UE include mirrored copies of critical grant fields (such as NDI and RV) in the HARQ feedback message. This allows the network to detect whether the feedback was lost by comparing expected values with mirrored values, thereby improving link adaptation reliability for PDCCH/ePDCCH without significantly increasing feedback processing complexity.
Data Source
AI summary
Techniques according to which HARQ feedback transmitted from a wireless device to a base station includes not only the ACK/NACK status for the corresponding hybrid automatic-repeat-request (HARQ) process, but also certain information that was provided by the network in the last received downlink assignment. An example method, as implemented in a wireless device operating in a wireless communication network, comprises receiving from the wireless communication network, in a first transmission-time interval, a resource-assignment message indicating resources allocated for a data transmission to the wireless device. The example method further comprises transmitting to the wireless communication network, in a second transmission-time interval, feedback information that includes an indication of whether the data transmission was correctly received by the wireless device and further includes one or more mirrored information fields copied from the resource-assignment message.