Group Acknowledgement for Low Latency Wireless HARQ
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Solution Overview
Problem
Legacy LTE wireless communication systems face challenges in achieving low latency due to rapid retransmissions in poor channel conditions, which counteract the benefits of quick uplink and downlink channels with reduced transmission time intervals (TTIs).
Innovation Solution
Implementing a method where user equipment (UE) receives downlink channel transmissions using a reduced TTI and provides a group acknowledgement in a single uplink channel transmission with a larger TTI, allowing for efficient communication and reducing round-trip time (RTT) associated with hybrid automatic repeat request (HARQ) procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If reduced TTI is used for downlink channel transmissions, then communication speed is improved, but round-trip time for HARQ procedures remains high due to legacy uplink TTI
Solution Approach 1:
The patent applies dynamics by making the uplink TTI flexible and adaptable to match the downlink TTI duration. Instead of using a fixed legacy uplink TTI, the system dynamically adjusts the uplink TTI to be equal to or longer than the reduced downlink TTI, enabling the uplink to keep pace with the accelerated downlink transmissions and thereby reducing the overall round-trip time.
Solution Approach 2:
The patent changes the time interval parameter from the legacy fixed value to a reduced value that matches the downlink TTI. By modifying the uplink TTI parameter to be equal to or longer than the reduced downlink TTI, the system achieves faster HARQ round-trip times while maintaining proper timing relationships for signal processing and feedback.
2Loss of time
If reduced TTI is used for quick uplink channels, then latency is reduced, but reliability deteriorates in poor channel conditions due to rapid retransmissions
Solution Approach 1:
The patent makes the uplink TTI dynamically adjustable based on channel conditions and downlink TTI configuration. This dynamic adaptation allows the system to use reduced TTIs for low latency when conditions permit, while maintaining the ability to adjust timing for reliability when channel conditions deteriorate, thus resolving the contradiction between speed and reliability.
Solution Approach 2:
The patent implements feedback mechanisms where the UE provides acknowledgments for downlink transmissions within the adjusted uplink TTI framework. This feedback loop allows the system to monitor communication reliability and adjust retransmission timing accordingly, ensuring that reduced TTI operations maintain adequate reliability even in varying channel conditions.
3Productivity
If reduced TTI is implemented, then communication efficiency is improved, but compatibility with legacy LTE systems is compromised
Solution Approach 1:
The patent segments the TTI configuration into different types: reduced TTIs for enhanced communication efficiency and legacy TTIs for backward compatibility. By allowing the system to operate with multiple TTI configurations simultaneously or selectively, it maintains compatibility with legacy LTE systems while enabling improved efficiency where supported.
Solution Approach 2:
The patent creates a universal TTI framework that can accommodate both reduced TTIs and legacy TTIs. The base station and UE are configured to understand and operate with different TTI durations, making the system multi-functional and adaptable to different operational modes, thereby maintaining compatibility while enabling efficiency improvements.
Data Source
AI summary
Certain aspects of the present disclosure provide techniques that may be used for low latency communications. For example, aspects allow a single group acknowledgement to be used to acknowledge a plurality of low latency transmissions. An exemplary method generally includes receiving, from a base station, a plurality of downlink channel transmissions, wherein each of the downlink channel transmissions is sent using a first transmission time interval (TTI) that is reduced relative to a legacy TTI and providing, in a single uplink channel transmission sent using a second TTI that is larger than the first TTI, a group acknowledgement indicating whether or not the downlink channel transmissions were successfully received by a UE.