Inactive-State Small Data Transmission With CQI-Based Modulation
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Solution Overview
Problem
Existing small data transmission in RRC inactive state is prone to errors and overheads due to poor channel conditions, leading to increased signaling and power consumption.
Innovation Solution
A method where user equipment measures channel quality and reports a channel quality indication to the base station, allowing the base station to select an appropriate modulation scheme for downlink data transmission, thereby reducing errors and retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If QPSK modulation is used for paging notification to ensure reliable reception in low RSRP conditions, then downlink data transmission may be subject to errors in low RSRP conditions, leading to packets retransmissions and overheads
Solution Approach 1:
The base station dynamically adapts the modulation scheme from fixed QPSK to variable modulation (QPSK, 16QAM, 64QAM) based on real-time channel quality feedback (CQI) from the UE. This dynamic adjustment allows the system to optimize between reliability and spectral efficiency according to current channel conditions, resolving the contradiction between using robust but inefficient QPSK and achieving higher efficiency with more vulnerable modulations.
Solution Approach 2:
The patent implements a feedback mechanism where the UE measures channel quality and reports CQI to the base station, which then uses this feedback to select the appropriate modulation scheme for downlink data transmission. This closed-loop feedback system enables the base station to make informed decisions about modulation selection, balancing reliability and energy efficiency based on actual channel conditions rather than using a fixed conservative approach.
2Productivity
If a connection is established for small data transmission, then data can be transmitted, but control signaling overhead increases when payload size is relatively small compared with the amounts of control signals
Solution Approach 1:
The base station pre-configures uplink resources (PUR/CG-SDT) and modulation scheme parameters for the UE before the UE actually needs to transmit data. This preliminary configuration allows the UE to directly use these pre-arranged resources for small data transmission without going through the full connection establishment procedure, thereby reducing signaling overhead while maintaining data transmission capability.
Solution Approach 2:
The patent extracts the essential configuration parameters (modulation schemes, uplink grants) from the full connection establishment process and provides them in advance through simplified RRC Release messaging. This allows small data transmission to proceed using only the extracted essential elements without requiring the complete connection setup, thus reducing the overhead of control signals while preserving data transmission functionality.
3Speed
If modulation scheme is selected without channel quality indication, then transmission can proceed quickly, but transmission errors increase in low RSRP conditions
Solution Approach 1:
The UE performs channel quality measurement and prepares CQI feedback in advance before actual data transmission begins. This preliminary channel assessment allows the base station to select the appropriate modulation scheme before transmission starts, ensuring both speed (by avoiding mid-transmission adjustments) and reliability (by selecting modulation appropriate to current channel conditions).
Solution Approach 2:
The patent implements channel quality feedback where the UE continuously monitors channel conditions and reports CQI to the base station. This feedback enables the base station to adaptively select modulation schemes that match current channel quality, ensuring reliable transmission even in varying RSRP conditions while maintaining efficient use of transmission time.
Data Source
AI summary
Robust Small Data Transmissions are performed from a base station to a user equipment of a wireless communication network while user equipment is in an Inactive state. A user equipment: receives a paging notification from a base station while in an inactive state, performs signal quality measurement, sends a message including at least a channel quality indication to the base station in response to the received paging notification, and receives a message from the base station including downlink data. The message is transmitted using a modulation scheme selected by the base station based on the reported channel quality indication.