TDD Subframe Partitioning for Short TTI Integration
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Solution Overview
Problem
Current Time Division Duplexing (TDD) technologies face challenges in reducing latency due to frame alignment and Hybrid Automatic Repeat Request (HARQ) Round-Trip-Time, which limits the scalability of short Transmit Time Intervals (TTIs) and affects HARQ timing for both downlink (DL) and uplink (UL) transmissions.
Innovation Solution
The method involves partitioning subframes into two sets: one for legacy TDD transmissions and another for short TTIs, allowing for flexible scheduling of short TTIs without interfering with legacy TDD operations by selecting specific subframe indices and forming complementary sets within a radio frame, enabling both DL and UL short TTIs on previously reserved subframes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If short TTIs are introduced in TDD to reduce latency, then transmission speed is improved, but HARQ timing and frame alignment are disrupted causing system complexity to increase
Solution Approach 1:
The patent segments subframes into two distinct sets: a first set for legacy TDD transmissions and a second set for short TTI transmissions. This segmentation allows short TTIs to be introduced without disrupting legacy HARQ timing and frame alignment, thereby reducing latency while maintaining system compatibility and avoiding excessive complexity increase.
2Loss of time
If short TTIs are introduced to reduce latency, then loss of time is improved, but legacy TDD operations are affected causing reliability to worsen
Solution Approach 1:
By partitioning subframes into separate sets for legacy and short TTI operations, the patent ensures that legacy TDD transmissions maintain their original timing and HARQ processes, preserving reliability. Meanwhile, short TTIs can operate with reduced latency in the dedicated second set of subframes without interfering with legacy operations.
3Adaptability or versatility
If subframes are partitioned into separate sets for legacy and short TTI transmissions, then scheduling flexibility is improved, but device complexity increases
Solution Approach 1:
The patent divides subframes into two manageable sets with clear functional assignments, providing scheduling flexibility by allowing independent configuration of legacy and short TTI transmissions. The segmentation creates well-defined boundaries that simplify the scheduling logic compared to a fully integrated approach, as each set can be managed with its own timing rules without constant interaction between legacy and short TTI processes.
Data Source
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AI summary
Systems and methods are disclosed that relate to selecting Time Division Duplexing (TDD) subframes (SFs) where both downlink (DL) and uplink (UL) short Transmit Time Intervals (sTTIs) can be introduced without substantially affecting legacy TDD operations. In this regard, in some embodiments, a method of operation of a network node of a cellular communications network comprises partitioning a plurality of SFs into at least two sets of SFs. The at least two sets of SFs comprising a first set of SFs for legacy TDD transmissions and a second set of SFs for sTTI TDD transmissions. The method further comprises performing one or more telecommunications functions according to the at least two sets of SFs. In this manner, TDD sTTI transmissions can be performed without substantially affecting legacy TDD operations.