ACK/NACK Transmission in Carrier Aggregation Systems
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Solution Overview
Problem
In carrier aggregation systems, conventional methods struggle to effectively transmit acknowledgement (ACK)/not-acknowledgement (NACK) signals when serving cells use different uplink (UL)-downlink (DL) configurations, such as FDD or TDD, leading to inefficiencies in HARQ processes and limited adaptability to changing traffic conditions.
Innovation Solution
A method and apparatus for transmitting ACK/NACK signals in a carrier aggregation system, where user equipment determines valid DL subframes based on cell-specific and reference UL-DL configurations, constructing ACK/NACK bit-streams only for valid DL subframes to ensure effective transmission across diverse UL-DL configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ACK/NACK transmission methods are used in carrier aggregation systems with different UL-DL configurations, then the system maintains simplicity in operation, but the HARQ process efficiency deteriorates and adaptability to traffic changes is limited
Solution Approach 1:
The patent applies dynamics by making the ACK/NACK transmission method adaptive to different UL-DL configurations. The system dynamically selects between bundling mode and non-bundling mode based on the specific configuration of serving cells, allowing the HARQ process to efficiently handle varying traffic conditions while maintaining operational simplicity through automated mode selection
Solution Approach 2:
The patent changes the transmission parameter (bundling or non-bundling) based on the UL-DL configuration of serving cells. When cells have the same UL-DL configuration, non-bundling mode is used for higher efficiency; when configurations differ, bundling mode is applied to ensure reliable ACK/NACK transmission, thus optimizing HARQ performance across different scenarios
2Reliability
If ACK/NACK is transmitted for all DL subframes based on reference UL-DL configuration, then the transmission coverage is complete, but unnecessary ACK/NACK transmission occurs for invalid DL subframes reducing system efficiency
Solution Approach 1:
The patent extracts and transmits only the necessary ACK/NACK information for valid DL subframes. By identifying which DL subframes are actually receivable based on the intersection of cell-specific and reference UL-DL configurations, the system removes unnecessary ACK/NACK transmissions for invalid subframes, improving system efficiency while maintaining transmission reliability for valid subframes
3Adaptability or versatility
If the system supports aggregation of cells with different UL-DL configurations (FDD and TDD), then the adaptability to traffic conditions is improved, but the complexity of determining valid DL subframes increases
Solution Approach 1:
The patent performs preliminary determination of valid DL subframes by comparing cell-specific UL-DL configurations with reference UL-DL configurations before ACK/NACK transmission. This advance identification of valid subframes simplifies the subsequent ACK/NACK construction process and enables the system to support diverse cell configurations (FDD and TDD aggregation) while managing determination complexity through systematic comparison methods
Data Source
AI summary
The present invention relates to a method of transmitting an acknowledgement/not-acknowledgement (ACK/NACK) and a device for using such a method. According to the present invention, a cell-specific downlink-uplink setting for one of a plurality of serving cells and a reference UL-DL setting is received, an effective downlink sub-frame capable of actually receiving a data unit from one serving cell is determined based on the settings, and only an ACK/NACK for the effective downlink sub-frame is configured as a bit string and fed back.