HARQ Feedback Deferral Window for Unlicensed Carrier Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communications, particularly in License Assisted Access (LAA) scenarios, the reliability and latency of Hybrid Automatic Repeat Request (HARQ) acknowledgment information feedback are compromised due to uncertainties caused by Listen Before Talk (LBT) procedures on unlicensed carriers, leading to potential HARQ acknowledgment information transmission drops and increased latency in downlink packet delivery.
Innovation Solution
A method and apparatus that allocate an uplink control channel resource for HARQ acknowledgment information feedback within a predefined deferral window, allowing for reliable and timely reporting of HARQ acknowledgment information by user equipment (UE) on unlicensed carriers, with mechanisms to reserve PUCCH resources and dynamically switch between unlicensed and licensed carriers to ensure timely feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If PUCCH is transmitted on unlicensed-carrier LAA SCells, then PUCCH load and inter-cell interference on licensed-carrier PCell are reduced, but HARQ acknowledgment information transmission may be dropped due to LBT uncertainty
Solution Approach 1:
The patent implements dynamic HARQ timing adjustment where the timing between downlink data transmission and HARQ acknowledgment feedback is made flexible rather than fixed. The eNB can dynamically configure different HARQ timing values (k values) based on channel conditions and LBT outcomes, allowing the system to adapt to the uncertain nature of unlicensed carrier access while maintaining reliable feedback transmission.
Solution Approach 2:
The patent changes the parameter of HARQ timing (the time offset between downlink data and uplink acknowledgment) from a fixed value to a configurable range of values. By allowing dynamic adjustment of this timing parameter based on LBT results and channel conditions, the system can optimize feedback reliability while offloading PUCCH to unlicensed carriers.
2Ease of operation
If LBT is performed for PUCCH transmission on unlicensed carriers, then channel access fairness is ensured, but HARQ acknowledgment information transmission timing becomes uncertain and may be dropped
Solution Approach 1:
The patent performs LBT (Listen Before Talk) as a preliminary action before PUCCH transmission on unlicensed carriers. By checking channel availability in advance and preparing HARQ feedback timing accordingly, the system ensures fair channel access while accounting for potential transmission delays. The eNB configures multiple possible timing values in advance to handle different LBT outcomes.
Solution Approach 2:
The patent makes HARQ timing dynamic to accommodate LBT uncertainty. Instead of fixed timing, the system allows flexible timing adjustment based on when LBT succeeds, ensuring that channel access fairness through LBT does not result in unacceptable timing variations or feedback drops.
3Ease of operation
If channel on unlicensed carriers is busy for a long time, then LBT ensures fair access, but latency of downlink packet delivery increases significantly
Solution Approach 1:
The patent performs LBT as a preliminary check before transmission attempts. By detecting busy channels in advance and adjusting timing accordingly, the system avoids unnecessary transmissions during prolonged channel occupancy, reducing wasted time while maintaining fair access. The preliminary LBT action allows the system to react to long-duration channel busy conditions.
Solution Approach 2:
The patent implements dynamic timing adjustment that responds to prolonged channel busy conditions. When LBT indicates the channel will be busy for an extended period, the system can dynamically adjust HARQ timing parameters to defer feedback until the channel becomes available, preventing excessive latency accumulation while preserving access fairness.
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
Embodiments of the present disclosure provide a method and apparatus of obtaining feedback of HARQ acknowledgment information. The method comprises allocating to UE an uplink control channel resource for report of HARQ acknowledgment information related to downlink data transmission on an unlicensed carrier. The method also comprises obtaining feedback of the HARQ acknowledgment information from the UE within a predefined deferral window. The predefined deferral window specifies a minimum delay and a maximum delay for report of the HARQ acknowledgment information. The embodiments of the present disclosure may increase the reliability and reduce the latency of HARQ acknowledgment information feedback. In addition, the embodiments of the present disclosure may not only be for LAA scenarios, but also may be extended to standalone LAA access scenarios on unlicensed carriers.