Wireless Communication Device Retransmission Rules for Missing HARQ Feedback
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Solution Overview
Problem
In wireless communication networks, particularly in unlicensed spectrum using LTE, the unpredictable nature of channel availability due to listen-before-talk (LBT) leads to frequent absence of HARQ feedback, causing misinterpretation and unnecessary retransmissions that interfere with other devices, degrading network performance.
Innovation Solution
A mechanism where wireless communication devices interpret absence of HARQ feedback as an acknowledgement (ACK) and refrain from retransmitting data, unless explicitly signaled otherwise, thereby reducing unnecessary transmissions and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wireless communication devices perform retransmission upon receiving negative acknowledgement or absence of HARQ feedback, then data reliability is improved, but unnecessary retransmissions occur in unlicensed spectrum causing interference and degrading network performance
Solution Approach 1:
The patent applies different HARQ feedback interpretation rules for different spectrum types. In licensed spectrum, absence of feedback is interpreted as NACK triggering retransmission. In unlicensed spectrum, absence of feedback is interpreted as ACK preventing retransmission. This local differentiation resolves the contradiction by adapting the retransmission behavior to the specific spectrum environment.
Solution Approach 2:
The patent changes the interpretation parameter of HARQ feedback based on spectrum type. The same absence of feedback signal is interpreted differently (as NACK vs as ACK) depending on whether the device is operating in licensed or unlicensed spectrum, thereby preventing unnecessary retransmissions in unlicensed bands while maintaining reliability in licensed bands.
2Measurement precision
If wireless communication devices monitor for HARQ feedback in unlicensed spectrum, then data transmission accuracy is improved, but channel sensing requirements increase due to unpredictable channel availability
Solution Approach 1:
Instead of actively sensing the channel to determine if feedback is present, the patent inverts the approach by assuming the channel is clear and only detecting feedback when present. The device monitors for feedback signals but does not perform active channel sensing, simplifying the complexity while maintaining detection accuracy through this inverted detection strategy.
Solution Approach 2:
The patent allows the HARQ feedback mechanism to self-indicate its presence or absence without requiring active sensing by the transmitting device. The feedback system serves itself by either sending the feedback signal when available or remaining silent when not available, and the transmitting device simply monitors for the signal's presence without additional channel sensing complexity.
3Reliability
If wireless communication devices retransmit data upon absence of HARQ feedback, then data delivery reliability is improved, but network efficiency deteriorates due to increased collisions in unlicensed spectrum
Solution Approach 1:
The patent implements location-specific retransmission policies based on spectrum type. In licensed spectrum where channels are dedicated and controllable, retransmission upon feedback absence maintains high delivery reliability. In unlicensed spectrum where channels are shared and unpredictable, the policy changes to avoid retransmission, thereby preventing collisions and maintaining network efficiency. This local quality differentiation resolves the contradiction between reliability and productivity.
Data Source
AI summary
Embodiments herein relate to a method implemented by a wireless communication device. The wireless communication device transmits data to a radio node of a wireless communication network. The wireless communication device monitors for a positive acknowledgement or a negative acknowledgement of the data from the radio node. The wireless communication device retransmits the data to the radio node when said monitoring indicates reception of a negative acknowledgement of the data. The wireless communication device refrains from retransmitting the data to the radio node when said monitoring indicates reception of a positive acknowledgement of the data. The wireless communication device also refrains from retransmitting the data to the radio node when said monitoring indicates neither reception of a positive acknowledgement of the data nor reception of a negative acknowledgement of the data.