Beam-Based C-RNTI Selection for Low-Latency Cell Updates

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Solution Overview

Problem

In future radio communication systems like NR, layer 1 / layer 2 (L1/L2) inter-cell mobility faces challenges with inefficient DL/UL beam management, leading to higher latency and overhead due to the need for radio resource control (RRC) reconfiguration during handover, and the issue of cell radio network temporary identifier (C-RNTI) collision between user terminals.

Innovation Solution

A terminal equipped with a receiving section and control section that selects an appropriate C-RNTI based on an indication for beam updates, allowing seamless inter-cell mobility without RRC reconfiguration, by associating C-RNTIs with non-serving cells using higher layer signaling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a terminal performs channel state information (CSI) feedback based on downlink reference signals, then the base station can accurately determine the downlink channel state, but the terminal must first perform channel estimation which increases processing complexity and time consumption

Engineering Contradiction:
Improvechannel state measurement accuracyVSAvoidterminal processing complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent introduces an intermediary mechanism where the base station directly provides CSI feedback information to the terminal without requiring the terminal to perform complex channel estimation. The base station acts as a mediator that generates and transmits CSI feedback signals, which the terminal then uses to determine downlink channel state, thereby reducing terminal processing complexity while maintaining measurement accuracy

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the traditional mechanical channel estimation process at the terminal with a signal-based approach. Instead of the terminal performing complex signal processing to estimate channel state, the system uses pre-configured reference signals and feedback mechanisms where the base station provides channel state information directly, substituting the terminal's computational burden with a more efficient signal transmission and reception process

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If the terminal performs channel estimation using downlink reference signals, then the base station can obtain accurate channel state information, but the time required for channel estimation increases the overall communication delay

Engineering Contradiction:
Improvechannel state information accuracyVSAvoidchannel estimation time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent applies preliminary action by having the base station pre-configure and transmit reference signals before the actual data communication begins. The terminal uses these pre-transmitted reference signals to perform channel estimation in advance, so that when data transmission starts, the channel state information is already available, thereby reducing the time delay during the actual communication process

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent ensures continuity of useful action by making the reference signal transmission an integral part of the ongoing communication process. The base station continuously transmits reference signals alongside data signals, allowing the terminal to continuously update channel state information without interruption. This continuous approach eliminates idle estimation periods and maintains efficient communication flow throughout the data transmission process

Inventive Principle:
Principle #20Continuity of useful action

3Productivity

If the base station transmits downlink signals using estimated channel state, then communication efficiency improves, but the terminal must perform complex signal processing to estimate the channel state

Engineering Contradiction:
Improvecommunication efficiencyVSAvoidterminal signal processing complexity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The patent uses the base station as an intermediary that performs channel state estimation and signal processing functions. Instead of the terminal independently estimating channel state and processing signals, the base station centralizes these functions by transmitting reference signals and providing channel state information. This intermediary approach maintains high communication efficiency while significantly reducing the signal processing complexity required at the terminal

Inventive Principle:
Principle #24Intermediary (Mediator)

4Reliability

If the terminal performs accurate channel state feedback, then the base station can optimize downlink transmission, but the terminal requires sophisticated signal processing capabilities

Engineering Contradiction:
Improvechannel state feedback accuracyVSAvoidterminal signal processing capability
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs the base station as an intermediary that handles the complex signal processing required for accurate channel state feedback. The base station transmits reference signals and processes the feedback information, while the terminal performs simpler signal reception and transmission functions. This intermediary mechanism maintains high feedback accuracy needed for reliable downlink transmission optimization while reducing the signal processing capability requirements at the terminal

Inventive Principle:
Principle #24Intermediary (Mediator)

Data Source

PatentEP4297451B1Terminal, wireless communication method, base station and system
Publication Date: 2026.05.06 NTT DOCOMO INC
  • EP4297451B1 patent drawingFigure 1A~1D
  • EP4297451B1 patent drawingFigure 2A~2B
  • EP4297451B1 patent drawingFigure 3

AI summary

A terminal according to one aspect of the present disclosure includes: a receiving section that receives an indication related to a beam; and a control section that selects, when a serving cell is updated by the indication, one cell radio network temporary identifier (C-RNTI) from among a plurality of C-RNTIs, based on the indication. According to one aspect of the present disclosure, a C-RNTI can be appropriately selected.