Short TTI Wireless Frame Structure for Low Latency
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Solution Overview
Problem
Current wireless communication systems face challenges in transmitting uplink/downlink data quickly, particularly due to limitations in resource allocation and latency, which are critical for next-generation mobile communication systems requiring high-speed data transfer and low latency.
Innovation Solution
A new physical frame structure is introduced, incorporating short Transmission Time Intervals (TTIs) within legacy TTIs, allowing for contention-based or scheduling-based data transmission, with demodulation reference signals (DMRS) transmitted within these short TTIs, and specific indicators for resource allocation to prevent collisions, enabling efficient uplink data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a new physical frame structure with short TTI is introduced, then data transmission speed is improved, but system complexity increases
Solution Approach 1:
The legacy TTI is segmented into multiple short TTIs (first short TTI and second short TTI), each with its own data transmission opportunity. This segmentation enables faster data transmission by reducing the TTI duration while maintaining the overall legacy TTI structure, thus improving speed without completely redesigning the system framework.
Solution Approach 2:
Multiple short TTIs are nested within the legacy TTI structure. The first and second short TTIs are contained within the boundaries of a single legacy TTI, allowing the system to support both short TTI-based fast transmission and legacy TTI-based operations, thereby improving speed while managing complexity through hierarchical nesting.
2Productivity
If contention-based or scheduling-based transmission is implemented in short TTI, then resource allocation efficiency is improved, but collision problems increase
Solution Approach 1:
The system dynamically supports both contention-based and scheduling-based transmission modes within the short TTI framework. The DCI format includes dynamic indicators that enable flexible switching between contention and scheduling resources, allowing the system to optimize resource allocation efficiency while managing collision risks through adaptive mode selection.
Solution Approach 2:
The DCI format acts as an intermediary that carries indicators to distinguish between contention and scheduling resources. This intermediary mechanism enables the system to coordinate resource allocation efficiently while preventing collisions by providing clear signaling about resource types and allocation status.
3Speed
If PHICH resources are mapped using new PRB index or indicators, then uplink data transmission is improved, but resource mapping complexity increases
Solution Approach 1:
The PHICH resources are pre-mapped using indicators included in the DCI format before actual data transmission occurs. This preliminary mapping approach enables faster uplink data transmission by having resource assignments ready in advance, while the indicator-based system manages mapping complexity through compact signaling rather than full resource specification.
Solution Approach 2:
The system uses parameter changes in the DCI format indicators to dynamically adjust PHICH resource mapping. By changing indicator values rather than reconfiguring entire resource maps, the system achieves faster uplink transmission while keeping mapping complexity manageable through parameter-based control.
Data Source
AI summary
In a method for transmitting data in a wireless communication system supporting a low latency service according to the present invention, a method performed by a first UE comprises transmitting to an eNB an urgent signal (US) for informing of occurrence of an event related to an urgent situation; receiving from the eNB a response to the urgent signal through two PHICH (Physical HARQ Indication Channel) resources; and transmitting to the eNB urgent data including detailed information related to the occurred event on the basis of the received response, wherein each PHICH resource is determined by a Physical Resource Block (PRB) index of the resource to which the urgent signal is transmitted.