HARQ Feedback Transmission on Grant-less Uplink Resources
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Solution Overview
Problem
In LTE standalone operation on unlicensed spectrum, Grant-less Uplink (GUL) transmissions face latency issues and increased channel access probability, leading to reduced effective throughput and unfair channel contention with other radio access technologies like Wi-Fi, due to the need for multiple Clear Channel Assessment (CCA) procedures and potential collisions during Hybrid Automatic Repeat Request (HARQ) feedback transmissions.
Innovation Solution
Implementing a method and apparatus that define rules for a User Equipment (UE) to transmit HARQ-ACK feedback on Grant-less Uplink Physical Uplink Shared Channel (GUL PUSCH) resources, allowing for alternative transmission paths when CCA procedures fail, thereby reducing latency and increasing channel access probability by using GUL PUSCH in conjunction with scheduled PUSCH resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple CCA procedures are performed for HARQ feedback transmission, then channel access reliability is improved, but transmission latency increases and throughput decreases
Solution Approach 1:
The patent performs CCA procedures in advance during downlink transmission opportunities, so that the channel is already assessed and ready for uplink HARQ feedback transmission. This preliminary channel assessment eliminates the need for additional CCA procedures at the time of feedback transmission, thereby reducing latency while maintaining reliability.
Solution Approach 2:
The patent dynamically adjusts the timing and resources for HARQ feedback transmission based on downlink transmission opportunities. By flexibly selecting feedback transmission resources that coincide with available downlink slots, the system optimizes channel utilization and reduces unnecessary waiting time for CCA procedures.
2Productivity
If GUL resources are used for HARQ feedback transmission, then channel access probability is improved, but collision risk with other transmissions increases
Solution Approach 1:
The patent utilizes the time dimension by transmitting HARQ feedback on uplink resources that coincide with downlink transmission opportunities. This temporal dimension separation allows the system to leverage available downlink slots for feedback transmission, reducing collision risk with other uplink transmissions while improving channel access probability.
Solution Approach 2:
The patent introduces scheduled PUSCH resources as an intermediary transmission path for HARQ feedback. When GUL resources experience collisions or failures, the system can redirect feedback transmission to these scheduled resources, which are protected by prior CCA procedures performed by the eNodeB, thereby mitigating collision risk.
3Adaptability or versatility
If CCA procedures are performed before every HARQ feedback transmission, then channel contention fairness is improved, but downlink throughput decreases due to suspension
Solution Approach 1:
The patent merges the CCA procedure timing with downlink transmission opportunities. By performing CCA for uplink feedback transmission during available downlink slots, the system combines channel assessment activities with existing transmission schedules, eliminating the need to suspend downlink transmissions for CCA purposes while maintaining fair channel access.
Data Source
AI summary
In accordance with an example embodiment of the present invention, a method, comprising receiving, by a user equipment, information for configuration with Grant-less Uplink Physical Uplink Shared Channel (GUL PUSCH) resources; attempting to transmit, by the user equipment, Hybrid Automatic Repeat Request (HARQ) feedback on at least one resources; performing a channel access procedure for transmitting Hybrid Automatic Repeat Request Acknowledgement (HARQ-ACK) on the GUL PUSCH resources in response to a determination that the attempting to transmit the HARQ feedback on the at least one resources is unsuccessful; and transmitting HARQ-ACK on the GUL PUSCH resources in response to successfully completing the channel access procedure, is disclosed.