User Terminal Preamble Detection for Dynamic TTI Direction

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Solution Overview

Problem

In future radio communication systems, there is a demand for increased flexibility in radio resource usage and reduced delay by dynamically switching between downlink (DL) and uplink (UL) per transmission time interval (TTI) in Time Division Duplex (TDD), but user terminals struggle to determine whether each TTI is for DL or UL.

Innovation Solution

A user terminal determines whether each TTI is DL or UL based on the presence or absence of a preamble signal, which is a sequence known to both the radio base station and the user terminal, and controls reception accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If DL and UL are switched dynamically per TTI in TDD to increase flexibility and reduce delay, then resource usage efficiency is improved, but the user terminal cannot determine whether each TTI is for DL or UL

Engineering Contradiction:

Improveresource usage efficiencyVSAvoidTTI direction determination

Core Design Contradiction:

ProductivityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent introduces a preamble signal as an intermediary element that carries direction information (DL or UL) within the TTI structure. This preamble acts as a mediator between the base station's scheduling decisions and the user terminal's reception actions, enabling the terminal to reliably determine TTI direction without complex blind decoding procedures.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If blind decoding is used to determine TTI direction in LTE systems, then the terminal can identify DL or UL, but delay increases and resource usage efficiency decreases

Engineering Contradiction:

ImproveTTI direction identification accuracyVSAvoiddelay

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The preamble signal is transmitted at the beginning of each TTI as a preliminary indicator of the TTI direction. This allows the user terminal to know in advance whether the current TTI is for DL or UL reception, eliminating the need for time-consuming blind decoding operations and reducing processing delay.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If blind decoding is performed to determine TTI direction, then the terminal can identify DL or UL, but processing complexity and energy consumption increase

Engineering Contradiction:

ImproveTTI direction identification accuracyVSAvoidterminal energy consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The preamble signal serves as a simple intermediary carrier of direction information that can be detected through straightforward correlation operations. This eliminates the need for complex blind decoding processes, significantly reducing the computational complexity and energy consumption at the user terminal while maintaining accurate TTI direction identification.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP3346773B1User terminal, wireless base station, and wireless communication method

Publication Date: 2025.07.02 NTT DOCOMO INC

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Figure 3

AI summary

In order to determine whether each TTI is a DL TTI or a UL TTI appropriately in a radio communication system in which DL and UL are switchable in TDD per TTI, the present invention provides a user terminal used in a radio communication system in which downlink (DL) and uplink (UL) are switchable per transmission time interval (TTI), the user terminal comprising: a reception section that receives a DL signal in a DL TTI; and a control section that controls reception of the DL signal by determining whether each TTI is the DL TTI or not based on a signal configuration of each TTI.