CSI Reporting via Random Access Preamble for Downlink Efficiency
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Solution Overview
Problem
In existing mobile communication systems, the CSI reporting process is inefficient, leading to low transmission efficiency for downlink data due to the use of low channel coding code rates and modulation schemes before CSI is determined by the terminal device.
Innovation Solution
A method where a network device sends K reference signal resources, allowing the terminal device to determine S reference signal resources and CSI, which are then used to adjust the channel coding code rate and modulation scheme for improved transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base station uses low channel coding code rate and low modulation scheme for PDSCH transmission before CSI is determined, then transmission robustness is improved, but transmission efficiency deteriorates
Solution Approach 1:
The terminal device performs channel measurement and determines CSI in advance during the random access process, before actual downlink data transmission begins. The terminal sends the determined CSI to the base station through the random access preamble or uplink shared channel, allowing the base station to have CSI available before scheduling PDSCH transmission, thus avoiding the need to use conservative low-rate coding and modulation schemes
2Reliability
If the terminal device reports CSI after RRC connection is established, then the CSI reporting process is completed, but downlink data transmission efficiency deteriorates due to delayed CSI availability
Solution Approach 1:
The terminal device performs channel measurement and determines CSI during the random access process, which occurs before RRC connection establishment. The CSI is sent to the base station along with or before the RRC connection setup complete message, allowing the base station to have CSI available much earlier than the traditional post-RRC-connection reporting timeline, thus reducing the time loss for CSI acquisition
Solution Approach 2:
The random access preamble and uplink shared channel serve as intermediary carriers to transport CSI from the terminal to the base station during the connection establishment phase. Instead of waiting for dedicated CSI reporting resources after RRC connection, the CSI is embedded in the existing random access signaling flow, enabling earlier CSI delivery without requiring additional dedicated reporting mechanisms
Data Source
AI summary
A network device sends K reference signal resources, where K is an integer greater than 0. The network device receives a first random access preamble in a first random access time-frequency resource unit. The network device determines indexes of S reference signal resources and first channel state information CSI of the S reference signal resources based on the first random access preamble and the first random access time-frequency resource unit the S reference signal resources are reference signal resources in the K reference signal resources, and S is an integer greater than 0 and less than or equal to K.