Dynamic Reference Signal Configuration in LAA Subframes
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Solution Overview
Problem
Current wireless communication systems face limitations in communication flexibility and efficiency, particularly in licensed assisted access (LAA) for LTE in unlicensed spectrum, where opportunistic scheduling and listen-before-talk mechanisms lead to reduced subframe occupancy and variable reference signal configurations, affecting channel demodulation accuracy and coexistence with other networks.
Innovation Solution
The implementation of dynamic reference signal configurations and patterns in LAA systems, where eNBs and UEs adapt reference signal transmission based on subframe types and listen-before-talk results, ensuring accurate channel demodulation and fair coexistence with other networks by adjusting OFDM symbol occupation and timing within subframes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If listen-before-talk mechanism is implemented in LAA systems, then fair coexistence with other networks is improved, but subframe occupancy is reduced
Solution Approach 1:
The system dynamically adjusts reference signal configurations and subframe structures based on listen-before-talk outcomes. When the channel is busy, the eNB can transmit reference signals in flexible subframes rather than being constrained by fixed subframe boundaries, thereby maintaining subframe occupancy while ensuring fair coexistence through LBT mechanism.
Solution Approach 2:
The patent changes the parameters of reference signal transmission by allowing variable positioning within subframes and adjusting the number of OFDM symbols occupied by reference signals based on LAA-specific conditions. This enables the system to adapt subframe occupancy dynamically while maintaining reliable channel demodulation and fair coexistence.
2Adaptability or versatility
If dynamic reference signal configurations are implemented, then communication flexibility is improved, but channel demodulation accuracy is affected
Solution Approach 1:
The patent applies different reference signal configurations to different subframe types (flexible vs. non-flexible) and different LAA conditions. Each subframe receives a tailored reference signal configuration appropriate to its specific characteristics, ensuring optimal channel demodulation accuracy for each local condition while maintaining overall system flexibility.
Solution Approach 2:
The reference signal configuration is made dynamic by allowing the eNB to adjust the number of reference signal OFDM symbols and their positioning within subframes based on the listen-before-talk outcome and subframe type. This dynamic adaptation maintains channel demodulation accuracy while achieving communication flexibility.
3Productivity
If reference signals are transmitted in flexible subframes, then subframe usage efficiency is improved, but device complexity is increased
Solution Approach 1:
The eNB signals to the UE in advance whether a subframe is flexible or non-flexible and provides the appropriate reference signal configuration before the UE attempts to decode the subframe. This preliminary signaling allows the UE to prepare the correct demodulation parameters, reducing the complexity of real-time decision-making at the UE while improving subframe usage efficiency.
Solution Approach 2:
The patent segments subframes into flexible and non-flexible types with distinct reference signal configurations. This segmentation allows the system to optimize each segment independently, improving overall subframe usage efficiency while managing device complexity through standardized handling of each segment type.
Data Source
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AI summary
A user equipment (UE) is described that includes a control channel receiver configured to monitor, in a license-assisted-access (LAA) cell, a first physical downlink control channel (PDCCH) and to monitor a second PDCCH. The first PDCCH includes a DCI format having a field for indicating an occupied-OFDM-symbol configuration for a subframe in which the first PDCCH is detected. The second PDCCH is a PDCCH of which detection indicates a transmission of a PDSCH on the LAA cell. A reference signal receiver is configured to receive reference signals of which resource element position within the subframe is determined depending on the occupied-OFDM- symbol configuration. A shared channel receiver is configured to receive the PDSCH assuming the same antenna port is used as for the reference signals.