Subframe-less CSI-RS Scheduling in LAA LTE
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Solution Overview
Problem
Existing CSI-reporting schemes in wireless communication systems, particularly in LTE systems, face limitations due to the duty-cycle constraint of 5% for control signaling without Listen-Before-Talk (LBT), leading to less flexible CSI measurements and potential inaccuracies due to channel access by other transmitters during measurement periods.
Innovation Solution
Implementing a subframe-less configuration for CSI measurement resources, allowing CSI-RS to be sent aperiodically using an LBT mechanism, enabling the network node to control when CSI-measurement resources are present, thereby ensuring accurate measurements and aligning CSI feedback with data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CSI-RS is transmitted periodically with fixed subframe configuration, then the duty cycle constraint of 5% is satisfied, but the flexibility of CSI measurements is reduced and measurement accuracy deteriorates due to potential channel access by other transmitters
Solution Approach 1:
The patent applies dynamics by transitioning from fixed periodic CSI-RS transmission to dynamic aperiodic transmission triggered by LBT outcomes. The network node dynamically determines when to transmit CSI-RS based on channel access success, allowing the system to adapt to varying channel conditions and maximize measurement opportunities while maintaining reliability.
Solution Approach 2:
The patent changes the temporal parameter of CSI-RS transmission from fixed periodic intervals to variable aperiodic timing based on LBT results. This parameter change enables the system to seize measurement opportunities when the channel is clear while respecting duty cycle constraints, thereby improving both accuracy and flexibility simultaneously.
2Measurement precision
If CSI-RS is transmitted aperiodically using LBT mechanism, then the flexibility and accuracy of CSI measurements are improved, but the complexity of resource configuration increases
Solution Approach 1:
The patent applies self-service by enabling the network node to autonomously determine CSI-RS transmission timing based on LBT outcomes without requiring complex centralized scheduling. The system self-regulates measurement resource allocation based on channel conditions, reducing configuration complexity while maintaining high measurement precision.
Solution Approach 2:
The patent implements feedback mechanisms where the network node monitors LBT outcomes and adjusts CSI-RS transmission accordingly. This closed-loop feedback system automatically optimizes measurement precision based on real-time channel access success, eliminating the need for complex manual resource configuration.
3Loss of time
If CSI feedback is received later after periodic CSI-RS transmission, then the duty cycle constraint is maintained, but the timeliness of channel state information is reduced
Solution Approach 1:
The patent applies preliminary action by performing LBT checks before transmitting data and conditionally transmitting CSI-RS in advance when the channel is clear. This allows the system to prepare measurement resources ahead of data transmission, reducing feedback time delay while ensuring duty cycle compliance through prior channel assessment.
Solution Approach 2:
The patent transforms the periodic CSI-RS transmission into event-driven periodic action triggered by LBT success. Instead of rigid periodic transmission that may waste time, the system performs measurements at optimal intervals determined by actual channel availability, reducing overall time delay while maintaining reliable duty cycle compliance.
Data Source
AI summary
Methods by network nodes and related network nodes are disclosed for configuring a user equipment (UE) in a telecommunications system. The UE is configured with a Channel-State Information (CSI) measurement resource with subframe-less configuration. A grant is sent on Enhanced Physical Downlink Control Channel ((e)PDCCH) for the UE with a Radio Network Temporary Identifier (RNTI_CSI) including specification of subframe configuration of CSI-measurement resources. A CSI-reference signal (CSI-RS) is sent according to a desired scheme in subframes indicated by the subframe configuration. Corresponding methods by UEs and related UEs are also disclosed.