TTI Coexistence via Boundary Alignment
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Solution Overview
Problem
Wireless communication systems face challenges in coexisting with multiple transmission time intervals (TTIs) of different durations, leading to resource scheduling conflicts and increased system complexity due to varying TTI durations among user equipment (UEs).
Innovation Solution
The system configures TTIs of shorter durations to align with or be embedded within longer TTIs, using gap symbols or merged TTIs to avoid timing conflicts, allowing for efficient coexistence of different TTI durations in both uplink and downlink communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple TTIs of different durations are supported to enable low-latency communication, then communication flexibility and low-latency performance are improved, but resource scheduling conflicts and system complexity increase
Solution Approach 1:
The system segments the TTI structure by dividing longer TTIs into multiple shorter TTIs. For example, a 1ms TTI can be segmented into multiple shorter TTIs of different durations (e.g., 2-symbol, 4-symbol, 7-symbol TTIs), allowing flexible allocation of time resources while maintaining clear boundary definitions that prevent scheduling conflicts
Solution Approach 2:
The patent implements nesting by embedding shorter TTIs within longer TTI structures. Shorter TTIs of 2 or 4 symbols can be nested within 7-symbol TTIs, which themselves can be nested within 1ms subframes. This nested structure allows the system to support multiple TTI durations simultaneously while maintaining hierarchical organization that simplifies resource management and reduces scheduling complexity
2Loss of time
If shorter TTIs are used to reduce transmission time, then latency is reduced, but scheduling conflicts with longer TTIs increase
Solution Approach 1:
The system applies local quality by assigning different TTI duration characteristics to different time resources within the same system. Specifically, certain symbol periods are designated for short TTIs (2 or 4 symbols) to achieve low latency, while other symbol periods are allocated to longer TTIs (7 symbols or 1ms) for stable scheduling. The boundaries of these different TTI types are carefully configured to align with each other, ensuring that short TTIs do not overlap with long TTI boundaries, thus preventing scheduling conflicts while maintaining low-latency performance where needed
Data Source
AI summary
Methods, systems, and devices for wireless communication are described. Different transmission time interval (TTI) durations may be supported and configured to coexist with one another. A set of TTIs with a relatively short duration may overlap in time with longer duration TTIs. Boundaries of TTIs with a relatively short duration may be configured to align with boundaries of relatively longer duration TTIs. For example, TTIs that are a Long Term Evolution (LTE) subframe, an LTE slot, and a duration of two LTE symbol periods may be supported. Two-symbol period TTIs may align with or be embedded within slot-duration TTIs, which, in turn, may align with or be embedded within a subframe. In some examples, one or more symbol periods of a subframe may be designated as a gap between two-symbol TTIs within the subframe, or such symbols may be merged with a two-symbol TTI within the subframe.