ACK/NACK Transmission Timing in TDD-FDD Aggregated Wireless Systems
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Solution Overview
Problem
In wireless communication systems, particularly in LTE-based networks, transmitting ACK/NACK signals across serving cells using different radio frame structures, such as TDD and FDD, poses challenges due to differing uplink and downlink subframe configurations, leading to inefficiencies in HARQ processes.
Innovation Solution
A method where a terminal determines the time interval for transmitting ACK/NACK signals based on either the first HARQ timing, applicable when the primary cell is used alone, or the second HARQ timing, which is additional to the first, allowing efficient operation even when multiple serving cells with different radio frames are aggregated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple serving cells with different radio frames (TDD and FDD) are aggregated, then the system can serve diverse communication needs and increase capacity, but the HARQ process becomes complex and ACK/NACK transmission timing becomes unclear
Solution Approach 1:
The patent segments the HARQ timing determination into separate tables based on the radio frame structure type. Table 1 provides timing for TDD frames while Table 2 provides timing for FDD frames. This segmentation allows the terminal to efficiently determine ACK/NACK transmission timing by first identifying the frame structure type, thereby reducing complexity despite supporting multiple frame types.
Solution Approach 2:
The patent applies different HARQ timing rules to different serving cells based on their local characteristics (TDD or FDD frame structure). Each cell type has its own specific timing parameters and rules, allowing optimized HARQ operation for each cell while maintaining overall system coordination through the primary cell's control.
2Productivity
If TDD and FDD cells are aggregated, then the terminal can receive data from multiple cells simultaneously, but determining the correct uplink subframe for ACK/NACK transmission becomes problematic due to different uplink-downlink configurations
Solution Approach 1:
The patent introduces the primary cell as an intermediary that coordinates HARQ timing for secondary cells with different frame structures. The eNodeB determines the appropriate uplink subframe based on the primary cell's configuration and signaling information, which then guides the terminal's ACK/NACK transmission. This intermediary approach simplifies the terminal's operation by centralizing timing determination logic.
Solution Approach 2:
The patent performs preliminary configuration of HARQ timing parameters through higher-layer signaling before actual data transmission occurs. The eNodeB pre-configures the terminal with the appropriate timing information based on the cell types involved, so that during operation the terminal can directly apply the pre-determined timing rules without complex real-time calculations.
3Ease of manufacture
If conventional HARQ timing is applied to FDD cells in TDD aggregation, then the terminal can use existing timing rules, but transmission delays increase and efficiency decreases
Solution Approach 1:
The patent changes the HARQ timing parameters specifically for FDD cells when aggregated with TDD cells. Instead of using the standard TDD timing parameters, the patent applies modified parameters (as shown in Table 2) that account for the FDD cell's continuous uplink availability. This parameter change enables faster ACK/NACK transmission while maintaining implementation simplicity through tabular lookup.
Data Source
AI summary
Provided are a method whereby a terminal transmits an acknowledgement/not-acknowledgement (ACK/NACK) with a primary cell and a secondary cell aggregated, and a device for supporting the method. The method comprises: receiving data by a downlink subframe of a secondary cell; and transmitting an ACK/NACK for the data by an uplink subframe of a primary cell, wherein: the time interval between the downlink subframe and the uplink subframe is determined by a first hybrid automatic repeat request (HARQ) timing or a second HARQ timing; the first HARQ timing is an HARQ timing which is applied when the primary cell is used alone; and the second HARQ timing is an HARQ timing which is additional to the first HARQ timing.