DL HARQ Timing in TDD with Reduced Processing Time
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Solution Overview
Problem
Current downlink Hybrid Automatic Repeat Request (HARQ) timing in LTE TDD systems results in higher latency due to fixed timing configurations, which can be improved by reducing processing time and optimizing HARQ feedback transmission.
Innovation Solution
The proposed solution involves determining a downlink HARQ timing value k based on TDD uplink/downlink configurations to transmit HARQ feedback in an uplink TTI nUL=nDL+k, where k is minimized to reduce processing time, and utilizing the Uplink Part of a Special Subframe (UpPTS) for HARQ acknowledgement, with new timing tables designed for latency optimization and load balancing approaches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If fixed timing configurations are used for downlink HARQ in LTE TDD systems, then system stability and simplicity are maintained, but latency is increased due to longer processing times
Solution Approach 1:
The patent applies dynamics by making the HARQ timing value k variable rather than fixed. The value of k is dynamically selected based on the TDD uplink/downlink configuration, allowing the system to adapt the processing time to match different traffic patterns and duplexing scenarios, thereby reducing latency without sacrificing stability
Solution Approach 2:
The patent changes the parameter k (HARQ timing value) based on different TDD configurations. By adjusting this key parameter according to the specific uplink/downlink configuration, the system optimizes processing time and reduces latency while maintaining compatibility with existing LTE TDD frameworks
2Loss of time
If HARQ feedback is transmitted in traditional downlink SF or DwPTS, then reliability is maintained, but latency is increased due to longer feedback transmission time
Solution Approach 1:
The patent introduces a new dimension for HARQ feedback transmission by utilizing UpPTS (Uplink Part of Special Subframe), which is traditionally not used for data transmission. This dimensional change in resource utilization allows feedback to be sent earlier without compromising the reliability of the feedback mechanism
Solution Approach 2:
The patent enables preliminary action by allowing HARQ feedback to be transmitted in UpPTS before the traditional downlink SF or DwPTS. This advance transmission of feedback reduces the overall latency while the feedback reliability is maintained through proper resource allocation and timing
3Productivity
If minimum processing time is reduced for HARQ feedback, then latency is reduced and system responsiveness is improved, but processing complexity increases
Solution Approach 1:
The patent reduces processing complexity by changing the timing parameter k to smaller values based on TDD configuration. This parameter adjustment allows the system to achieve faster responsiveness while the complexity is managed through standardized timing relationships defined in the patent
Data Source
AI summary
Systems and methods for determining and utilizing downlink Hybrid Automatic Repeat Request (HARQ) timing for reduced processing time are disclosed. In some embodiments, a method of operation of a wireless device in a cellular communications network comprises determining, based on a Time Division Duplexing (TDD) uplink/downlink configuration, a downlink HARQ timing value k for transmission of downlink HARQ feedback for a downlink transmission received in a downlink Transmission Time Interval (TTI) nDL. The method further comprises transmitting, in an uplink TTI nUL=nDL+k, the downlink HARQ feedback for the downlink transmission received in the downlink TTI nDL. For at least some combinations of values for nUL and TDD uplink/downlink configurations, k<4. In this manner, HARQ timing is provided for reduced processing time.