ACK/NACK Transmission Across TDD and FDD Cells
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems, particularly in LTE-based networks, there is a challenge in efficiently transmitting acknowledgement/not-acknowledgement (ACK/NACK) signals across serving cells that use different types of radio frames, such as TDD and FDD, due to mismatched uplink and downlink subframe configurations, which can lead to timing and synchronization issues.
Innovation Solution
A method and apparatus for a user equipment (UE) to transmit ACK/NACK signals across three or more serving cells aggregated using different types of radio frames, ensuring efficient operation of the Hybrid Automatic Repeat Request (HARQ) process by synchronizing ACK/NACK timing across various frame structures, including TDD and FDD frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple serving cells with different radio frame structures (TDD and FDD) are aggregated, then the system can support more diverse communication scenarios and increase bandwidth, but timing and synchronization issues arise in ACK/NACK transmission
Solution Approach 1:
The patent segments the ACK/NACK transmission process by identifying the primary cell and secondary cell separately. The primary cell's uplink subframe configuration is used as the reference, while downlink data from secondary cells (with different frame structures) is acknowledged in the primary cell's uplink subframes. This segmentation allows each cell to maintain its own frame structure while ensuring synchronized ACK/NACK transmission through the primary cell.
Solution Approach 2:
The primary cell acts as an intermediary between secondary cells with different radio frame structures. Downlink data received from secondary cells is acknowledged through the primary cell's uplink channel, which serves as a common mediator that reconciles the timing differences between TDD and FDD frame structures, ensuring reliable HARQ operation across aggregated cells.
2Productivity
If ACK/NACK timing is determined by standard HARQ timing rules, then the HARQ process operates efficiently in single-cell scenarios, but timing conflicts occur when aggregating cells with different uplink-downlink configurations
Solution Approach 1:
The patent changes the timing parameter reference from the secondary cell's uplink configuration to the primary cell's uplink configuration. By adjusting which cell's uplink-downlink pattern serves as the timing reference, the system resolves timing conflicts without sacrificing HARQ efficiency. The ACK/NACK timing is determined based on the primary cell's uplink subframe availability rather than applying standard timing rules uniformly across all cells.
3Stability of the object's composition
If TDD cell uplink subframes are used for ACK/NACK transmission, then timing alignment is achieved for TDD cells, but FDD downlink subframes cannot be properly acknowledged due to non-continuous uplink configuration in TDD
Solution Approach 1:
The primary cell's uplink channel serves a universal function for all aggregated cells regardless of their frame structure. Whether data is received from TDD or FDD secondary cells, the ACK/NACK is transmitted through the primary cell's uplink channel, making this channel multi-functional and adaptable to different radio frame structures while maintaining timing stability.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided are a method and an apparatus for transmitting ACK/NACK by a terminal in which a primary cell, a first secondary cell, and a second secondary cell are set. The method comprises: receiving scheduling information from the first secondary cell; receiving a data channel from the second secondary cell, the data channel being scheduled by the scheduling information; and transmitting ACK/NACK for the data channel through the primary cell, wherein the primary cell and the first secondary cell use a time division duplex (TDD) frame, and the second secondary cell uses a frequency division duplex (FDD) frame.