MTC UE CSI Feedback via Aperiodic PDCCH Trigger
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Solution Overview
Problem
Current wireless access systems face challenges in efficiently measuring and reporting Channel State Information (CSI) by Machine Type Communication (MTC) User Equipment (UE), particularly in transmitting downlink data and periodically or aperiodically reporting CSI.
Innovation Solution
A method involving receiving a higher layer signal with a Channel Quality Indicator (CQI) index, an aperiodic CSI request field in the Physical Downlink Control Channel (PDCCH) signal, and repeatedly transmitting the Physical Downlink Shared Channel (PDSCH) signal, allowing the UE to measure CSI in a CSI reference resource and feed it back using the Physical Uplink Shared Channel (PUSCH) signal, with options for modulation scheme, coding rate, and repetition number configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CSI measurement and reporting procedures are implemented in MTC systems, then channel quality feedback is improved, but system complexity and overhead increase
Solution Approach 1:
The patent segments CSI reporting into periodic and aperiodic modes, with further subdivision into different reporting configurations. The aperiodic CSI reporting is triggered by specific events (PDCCH reception, PDSCH reception) rather than continuous monitoring, dividing the feedback mechanism into discrete operational modes that reduce overall system complexity while maintaining measurement precision when needed.
Solution Approach 2:
The patent implements periodic CSI reporting configurations where the UE reports CSI at predetermined intervals or triggered by specific downlink receptions. This periodic structure allows the system to obtain necessary channel state information without continuous monitoring, balancing measurement accuracy with reduced signaling overhead and computational burden.
2Loss of time
If aperiodic CSI reporting is implemented, then feedback timeliness is improved, but signaling overhead increases
Solution Approach 1:
The patent configures aperiodic CSI reporting triggers in advance through higher layer signaling (RRC configuration). The network pre-defines the conditions under which aperiodic reporting should occur (e.g., upon PDCCH reception, upon PDSCH reception), so that when these events occur, the UE can immediately report CSI without additional negotiation. This preliminary configuration reduces feedback delay while minimizing real-time signaling overhead.
Solution Approach 2:
The UE autonomously determines when to report aperiodic CSI based on pre-configured triggers and its own reception status. When the UE receives a PDCCH or PDSCH signal, it automatically initiates CSI measurement and reporting according to the configured rules, without requiring continuous network coordination. This self-service mechanism reduces signaling overhead while maintaining timely feedback.
3Reliability
If repeated PDSCH transmission is used for MTC, then transmission reliability is improved, but resource consumption increases
Solution Approach 1:
The patent implements dynamic adaptation of transmission parameters based on CSI feedback. The network uses the reported channel state information to adjust modulation schemes, coding rates, and repetition numbers for PDSCH transmissions. This dynamic adjustment allows the system to use fewer repetitions when channel conditions are good, reducing resource consumption while maintaining reliability when conditions are poor through increased repetitions or more robust modulation.
Solution Approach 2:
The patent changes transmission parameters (modulation scheme, coding rate, repetition number) based on the CQI index and channel conditions. The CQI table maps channel quality to specific transmission parameters, allowing the system to optimize the balance between reliability and resource consumption by selecting appropriate parameter combinations based on current channel state rather than using fixed high-repetition configurations.
Data Source
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AI summary
The present invention provide a method by which a terminal measures channel state information (CSI), a method by which a terminal transmits CSI, and devices for supporting the methods. A method by which a terminal feeds back CSI in a wireless access system, according to one embodiment of the present invention, can comprise the steps of : receiving an upper layer signal including a channel quality indicator (CQI) index; receiving a physical downlink control channel (PDCCH) signal including an aperiodic CSI request field; receiving a physical downlink shared channel (PDSCH) signal that is repeatedly transmitted as many time as the number indicated by the CQI index; measuring the CSI for a CSI reference resource; and feeding back the measured CSI by using a physical uplink shared channel (PUSCH) signal.