HARQ Timing Offset for TDD Carrier Aggregation
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Solution Overview
Problem
In LTE-A systems with carrier aggregation, there is a challenge in transmitting HARQ ACK/NACK signals across secondary cells with different Time Division Duplex (TDD) configurations, leading to interference and difficulties in maintaining reliable data transmission.
Innovation Solution
A method is proposed where the base station transmits PDSCH at specific subframes of a secondary cell and controls the selection of uplink subframes for HARQ ACK/NACK transmission in the primary cell, aligning the timing with the downlink subframes of both primary and secondary cells, and using a specific format and table for mapping and receiving HARQ ACK/NACK signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carrier aggregation with different TDD configurations is used to support high data rate transmission, then bandwidth and data rate are improved, but interference occurs between cells with different TDD configurations and HARQ ACK/NACK transmission becomes unreliable
Solution Approach 1:
The patent changes the timing parameters of HARQ ACK/NACK transmission by introducing a specific offset k between PDSCH reception and PUCCH transmission. This parameter adjustment allows the system to accommodate different TDD configurations in carrier aggregation while maintaining reliable HARQ feedback, resolving the contradiction between supporting high data rates through carrier aggregation and ensuring reliable HARQ transmission across cells with different TDD uplink-downlink configurations.
2Adaptability or versatility
If HARQ ACK/NACK is transmitted in PUCCH of primary cell for secondary cell PDSCH, then cross-carrier feedback is enabled, but timing alignment becomes complex with different TDD configurations
Solution Approach 1:
The patent applies preliminary action by pre-defining the timing relationship between PDSCH and PUCCH using a predetermined offset k. This advance specification of timing parameters simplifies the complexity of timing alignment in cross-carrier feedback scenarios with different TDD configurations, as the timing relationship is established beforehand rather than dynamically calculated, reducing device complexity while maintaining adaptability.
3Productivity
If uplink-downlink configuration is optimized for each cell independently, then each cell achieves optimal performance, but interference occurs at subframe boundaries with different configurations
Solution Approach 1:
The patent introduces the HARQ timing offset k as an intermediary parameter that mediates between cells with different TDD configurations. This intermediary timing parameter allows each cell to maintain its optimized uplink-downlink configuration while providing a standardized mechanism for HARQ feedback transmission that prevents interference at subframe boundaries, enabling both cells to achieve optimal performance without mutual interference.
Data Source
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AI summary
A method for transmitting a physical channel in a Time Division Duplex (TDD) communication system capable of carrier aggregation is provided for supporting aggregation of carriers having different TDD configurations. The communication method of a terminal in a TDD radio communication system accomplishing broadband through carrier aggregation of primary and secondary cells, of which aggregated carriers have different TDD Uplink-Downlink (UL-DL) configurations, includes receiving Physical Downlink Shared Channel (PDSCH) through the secondary cell, and transmitting acknowledgement information corresponding to the PDSCH to a base station, where acknowledgement information is transmitted on a Physical Uplink Control CHannel (PUCCH) of the primary cell.