Uplink Control Information Carrier Switching for Unlicensed Spectrum
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Solution Overview
Problem
In LTE systems operating in unlicensed frequency bands, user equipment may fail to access channels timely for uplink control information transmission due to shared resource competition, leading to delayed or incorrect transmission of ACK/NACK, CSI, and SR information.
Innovation Solution
The method involves determining a PUCCH switching carrier group with one licensed primary carrier and multiple unlicensed carriers, performing LBT detection during a maximum feedback delay, and selecting an unlicensed carrier for transmission if detection succeeds, or switching to the licensed primary carrier if detection fails, to ensure timely uplink control information transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uplink control information is transmitted only over the licensed primary carrier, then transmission reliability is improved, but uplink control channel overhead becomes too high and spectrum resources are wasted
Solution Approach 1:
The patent segments the uplink control channel transmission by dividing it into two parts: critical control information (ACK/NACK) is transmitted over the licensed primary carrier to ensure reliability, while other control information (CSI, SR) is transmitted over unlicensed carriers to reduce overhead. This segmentation allows the system to optimize for both reliability and resource efficiency simultaneously.
2Quantity of substance
If uplink control information is transmitted over unlicensed carriers, then spectrum resources are utilized more efficiently, but transmission reliability deteriorates due to LBT mechanism causing access failures
Solution Approach 1:
The patent implements beforehand cushioning by transmitting critical uplink control information (ACK/NACK) over the licensed primary carrier as a backup channel before attempting transmission over unlicensed carriers. This ensures that even if LBT fails on unlicensed carriers, the most critical control information can still be transmitted reliably through the licensed carrier, providing a safety cushion against transmission failures.
3Adaptability or versatility
If LBT mechanism is applied before uplink transmission on unlicensed carriers, then fair spectrum sharing with other systems is improved, but channel access timeliness deteriorates causing delayed control information transmission
Solution Approach 1:
The patent segments control information into different priority levels and transmits them through different channels. Critical time-sensitive information (ACK/NACK) is transmitted over the licensed carrier where LBT is not required, ensuring timely delivery. Less time-critical information (CSI, SR) is transmitted over unlicensed carriers with LBT, achieving fair spectrum sharing. This segmentation resolves the contradiction by matching transmission channel selection to information priority.
Data Source
AI summary
Disclosed are a method and device for transmitting uplink control information, which are used for realizing a UE performing switching transmission of an uplink control channel on subframes and carriers, so that if the UE fails to pre-empt a resource on an unlicensed carrier, the UE may switch to the other carriers for transmission or continue to try to perform LBT in subsequent subframes, so as to ensure the timely and correct transmission of the uplink control information. The method comprises: a UE determining a physical uplink control channel (PUCCH) switching carrier group and the maximum feedback delay.