FDD Downlink Assignment DAI for HARQ Feedback Accuracy
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Solution Overview
Problem
In LTE wireless communication systems, channel collisions occur when downlink transmissions with different processing times are scheduled to be acknowledged in the same uplink transmission, leading to mismatches in HARQ bit reporting, which negatively impact downlink performance due to the lack of accurate DAI functionality for FDD operations with diverse processing times.
Innovation Solution
Implementing a network node that schedules downlink transmissions with distinct processing times on different frequency carriers, using a DAI that includes a total and accumulative index to ensure accurate HARQ feedback reporting, even when transmissions occur at different times, thereby preventing misinterpretation of feedback and maintaining downlink performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If downlink transmissions with different processing times are scheduled on different frequency carriers, then HARQ feedback accuracy is improved, but system complexity increases due to need for separate DAI tracking per carrier
Solution Approach 1:
The patent segments the downlink carrier spectrum into multiple frequency carriers, each with its own processing time characteristics. The DAI tracking is segmented per carrier, allowing independent management of HARQ feedback for each carrier. This segmentation enables accurate tracking of transport blocks with different processing times without requiring a single complex unified tracking mechanism across all carriers.
2Productivity
If multiple downlink transmissions are acknowledged in the same uplink transmission, then uplink resource efficiency is improved, but HARQ bit reporting accuracy deteriorates due to channel collisions
Solution Approach 1:
The Downlink Assignment Index (DAI) acts as an intermediary mechanism that mediates between multiple downlink transmissions and the single uplink acknowledgment. The DAI provides a cumulative count of transport blocks across different carriers and time instances, enabling the receiving end to correctly interpret HARQ feedback bits even when multiple downlink transmissions are acknowledged in the same uplink transmission. This intermediary tracking mechanism prevents channel collision errors by ensuring proper bit alignment between transmitted and received acknowledgments.
Data Source
AI summary
According to some embodiments, a network node in a frequency division duplex (FDD) wireless communication network is operable to schedule a first downlink transmission with a first transmission processing time on a first frequency carrier. The scheduling comprises a first downlink assignment index (DAI). The first DAI comprises a first total DAI and a first accumulative DAI. The network node is operable to schedule a second downlink transmission with a second transmission processing time different than the first on a second frequency carrier. The scheduling comprises a second DAI. The second DAI comprises a second total DAI and a second accumulative DAI. The network node expects hybrid automatic repeat request (HARQ) feedback for the first downlink transmission and the second downlink transmission in a single uplink transmission. The network node is further to transmit the scheduling for the first and second downlink transmission to a wireless device.