SRS Transmission in LTE Unlicensed Frame Structure 3
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Solution Overview
Problem
In LTE systems operating in unlicensed frequency bands with frame structure 3, ensuring normal SRS transmission and accurate uplink channel quality measurement is challenging due to inflexible uplink and downlink subframe configurations, which can lead to channel occupation by other systems like Wi-Fi.
Innovation Solution
A method for determining and selecting an appropriate target symbol within a target subframe for SRS transmission based on its type, using techniques such as receiving high-layer signaling or DCI indications to identify uplink subframes, Uplink Pilot Time Slots, or partial subframe configurations, allowing for flexible SRS scheduling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If frame structure 3 is used with dynamic uplink and downlink subframe configuration, then adaptability to LBT mechanism is improved, but reliability of SRS transmission deteriorates due to possible absence of uplink subframes
Solution Approach 1:
The patent applies dynamics by enabling flexible conversion between uplink and downlink subframes according to LBT channel detection results. The system dynamically adjusts subframe directions based on channel availability, allowing the frame structure to adapt to varying channel conditions while maintaining SRS transmission capability through configurable parameters that define which subframes can serve as SRS transmission opportunities.
2Adaptability or versatility
If downlink subframe is converted to uplink subframe during data transmission, then flexibility of subframe configuration is improved, but loss of time occurs due to re-execution of LBT channel detection
Solution Approach 1:
The patent applies preliminary action by pre-configuring parameters that define which downlink subframes can be converted to uplink subframes for SRS transmission. The network side determines and signals these configurations in advance, so when channel conditions permit, the conversion can occur without requiring real-time LBT re-execution, thereby reducing time loss while maintaining flexibility.
3Device complexity
If traditional TDD fixed subframe allocation is used, then device complexity is reduced, but adaptability to dynamic uplink and downlink business deteriorates
Solution Approach 1:
The patent applies parameter changes by introducing configurable parameters that control subframe direction conversion. Instead of fixed TDD allocation, the system uses parameters to define which subframes can be dynamically switched between uplink and downlink based on traffic demands and channel conditions, achieving adaptability without requiring complex real-time reconfiguration mechanisms.
Data Source
AI summary
The present disclosure provides a Sounding Reference Signal (SRS) sending method when a Long Term Evolution (LTE) system works with a frame structure 3 in an unlicensed frequency band, a SRS sending device, and a terminal, and the SRS sending method when the LTE system works with the frame structure 3 in the unlicensed frequency band includes: determining a type of a target subframe to send a SRS; according to the type of the target subframe, selecting a target symbol in the target subframe for sending the SRS; sending the SRS through the target symbol. According to the technical solution of the present disclosure, when the LTE system works in the unlicensed frequency band, a normal transmission of the SRS can be ensured, thereby ensuring the measurement accuracy of the uplink channel quality, and improving the uplink throughput of the LTE system.