Carrier Aggregation with Mixed TTI Lengths

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Solution Overview

Problem

Current wireless communication systems face challenges in efficiently managing data transmission and Hybrid Automatic Repeat Request (HARQ) feedback across carriers with varying Transmission Time Intervals (TTIs) in 5G systems, particularly with the need for flexible uplink/downlink ratios and reduced latency.

Innovation Solution

The implementation of methods and apparatuses at base stations and user equipment to transmit data and HARQ feedback across carriers with different TTI lengths, including scheduling grants and data transmissions in specific control and data regions, optimizing the timing to accommodate both short and long TTIs within the same subframe structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If carrier aggregation with multiple component carriers is adopted to improve throughput, then data transmission capacity is improved, but the complexity of managing different TTI lengths increases

Engineering Contradiction:

ImprovethroughputVSAvoidcomplexity of managing different TTI lengths

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent segments the carrier aggregation system into different component carriers, each with its own TTI length configuration. The base station manages multiple TTIs of different lengths (e.g., 1ms and 2ms) independently on different carriers, allowing flexible throughput optimization while controlling management complexity through carrier-specific TTI configurations

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic TTI length configuration where the base station can select different TTI lengths for different component carriers based on channel conditions and throughput requirements. This dynamic adaptation allows the system to optimize productivity while managing complexity through flexible, data-driven TTI selection

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If subframes/TTIs of the same length are used in carrier aggregation, then scheduling simplicity is maintained, but flexibility for 5G frequency requirements is reduced

Engineering Contradiction:

Improvescheduling simplicityVSAvoidflexibility for 5G frequency requirements

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent applies different TTI lengths to different component carriers based on their specific requirements. Higher frequency carriers use shorter TTIs to meet 5G latency requirements, while lower frequency carriers can use longer TTIs for simplified scheduling. This local differentiation maintains scheduling simplicity on each carrier while providing overall system flexibility

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the TTI length parameter dynamically across different component carriers. The base station configures different TTI durations (e.g., 1ms for high-frequency carriers, 2ms for low-frequency carriers) to optimize both scheduling simplicity and adaptability to 5G frequency requirements simultaneously

Inventive Principle:

Principle #35Parameter changes

3Loss of time

If HARQ feedback is transmitted in the same subframe as data transmission, then latency is reduced, but the control region timing becomes more complex

Engineering Contradiction:

ImproveHARQ feedback latencyVSAvoidcontrol region timing complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The patent implements preliminary action by transmitting HARQ feedback in the same subframe as the data transmission. The base station prepares and sends the HARQ feedback signal simultaneously with the data signal, eliminating waiting time and reducing latency. This is achieved by configuring the feedback timing to coincide with the data transmission timing in the control region

Inventive Principle:

Principle #10Preliminary action

4Adaptability or versatility

If flexible uplink/downlink ratio is implemented, then system adaptability is improved, but control signaling round-trip time increases

Engineering Contradiction:

Improveuplink/downlink ratio flexibilityVSAvoidcontrol signaling round-trip time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by having the base station transmit downlink scheduling information and HARQ feedback in advance within the same subframe. This preliminary transmission of control signals enables the user equipment to prepare for uplink transmissions, achieving flexible uplink/downlink ratio while minimizing control signaling round-trip time through proactive signal delivery

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20250097951A1Method and apparatus for communications with carrier aggregation

Publication Date: 2025.03.20 NEC CORP

AI summary

A method at a base station for performing data transmission to a user equipment in a communications system supporting carrier aggregation of at least one first carrier on which a short TTI is applied and at least one second carrier on which a long TTI is applied. The method transmits at least one DL scheduling grant corresponding to data transmission to the user equipment in a DL control region of at least one of a short TTI on a first carrier and a long TTI on a second carrier and performs DL data transmission towards the user equipment in a data transmission region of a short TTI on the first carrier and in the data transmission region of a long TTI on the second carrier as indicated by the at least one DL scheduling grant.