Short TTI Segmentation in TDD Subframes
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Solution Overview
Problem
Current Time Division Duplex (TDD) systems face long packet data latency due to limitations in frame alignment and Hybrid Automated Repeat Request (HARQ) round-trip time, which restricts the scalability of short transmission time intervals (TTIs) and affects radio resource efficiency.
Innovation Solution
Introducing short TTIs in both downlink (DL) and uplink (UL) subframes of TDD systems, allowing for flexible scheduling and transmission during specific symbols, while ensuring compatibility with legacy systems by reserving certain symbols for secondary synchronization signals and broadcast channels, and removing the guard period for efficient switching between DL and UL transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional TDD frame structure with 1ms subframes is used, then system compatibility and stability are maintained, but packet data latency is long and HARQ round-trip time is increased
Solution Approach 1:
The patent segments the traditional 1ms subframe into multiple shorter transmission time intervals (TTIs) of different lengths. This segmentation allows the system to use shorter TTIs for time-critical transmissions to reduce packet data latency, while maintaining the overall 1ms subframe structure for compatibility with existing systems. The segmented structure enables flexible TTI length selection without requiring complete frame structure redesign.
Solution Approach 2:
The patent introduces dynamic TTI length adaptation within the TDD frame structure. Different TTIs can have different lengths (e.g., 2ms, 4ms, 8ms) depending on traffic requirements and channel conditions. This dynamic flexibility allows the system to optimize latency for urgent data while maintaining stability for regular transmissions, resolving the contradiction between speed and complexity.
2Loss of time
If short TTIs are introduced to reduce latency, then packet data latency decreases, but compatibility with legacy systems deteriorates
Solution Approach 1:
The patent designs the TDD frame structure to support multiple TTI lengths (2ms, 4ms, 8ms) within a single unified framework. This multi-functional design allows the system to accommodate both legacy 1ms TTI requirements and new shorter TTI needs simultaneously. Different user equipment can operate with different TTI lengths based on their capabilities and service requirements, maintaining universal compatibility while enabling latency reduction.
Solution Approach 2:
The patent embeds multiple shorter TTIs within the traditional 1ms subframe structure. The shorter TTIs are nested as components of the larger subframe, allowing legacy systems to recognize the overall 1ms structure while newer systems can exploit the internal shorter TTI segments for reduced latency operations. This nesting approach preserves backward compatibility while enabling forward-looking performance improvements.
3Productivity
If guard period is removed for efficient DL to UL switching, then radio resource efficiency improves, but transmission reliability deteriorates
Solution Approach 1:
The patent changes the timing parameters and synchronization mechanisms to enable guard period removal or significant reduction. By adjusting the uplink timing advance parameters and implementing more precise synchronization protocols, the system can switch between downlink and uplink transmissions with minimal or no guard period, thereby improving radio resource efficiency while maintaining transmission reliability through enhanced timing control.
Data Source
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AI summary
Methods, wireless devices and network nodes for communicating in a wireless communication network are disclosed. According to one aspect, a wireless device includes processing circuitry configured to obtain information regarding the inclusion of at least one short transmission time interval, sTTI, in one of a time division duplex, TDD, uplink, UL, subframe and TDD downlink, DL, subframe of a radio frame. The wireless device further includes a transceiver configured to communicate with the network node using the at least one sTTI during the TDD subframe.