Shortened TTI Configuration for Wireless Latency Reduction
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Solution Overview
Problem
Current wireless communication systems face challenges in reducing latency for data transmission, particularly due to the limitations of Transmission Time Interval (TTI) length and hybrid automatic repeat request (HARQ) Round Trip Time (RTT), which impact network performance and delay in data exchange between user equipment (UE) and the evolved NodeB (eNodeB).
Innovation Solution
The implementation of shortened Transmission Time Intervals (xTTIs) within Long Term Evolution (LTE) subframes, allowing for faster acknowledgement/non-acknowledgement (ACK/NACK) feedback and efficient HARQ timeline management, along with self-contained HARQ-ACK windows, to minimize RTT latency while maintaining backward compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional Transmission Time Interval (TTI) length is used, then system compatibility and stability are maintained, but latency for data transmission increases
Solution Approach 1:
The patent segments the conventional TTI into multiple shorter transmission time intervals (sTTIs). Each sTTI can be independently scheduled and transmitted, allowing the system to reduce latency by sending multiple smaller packets in parallel rather than waiting for one complete large packet to finish transmission. This segmentation enables finer granularity in resource allocation and faster retransmission of failed packets.
Solution Approach 2:
The patent introduces dynamic TTI configuration where the network can switch between conventional TTI and shortened TTI modes based on traffic conditions, channel quality, and service requirements. This dynamic adaptation allows the system to optimize for low latency when needed while maintaining compatibility with legacy systems during normal operation, resolving the contradiction between latency reduction and system compatibility.
2Speed
If Transmission Time Interval (TTI) is shortened, then data transmission speed increases, but processing complexity and system overhead increase
Solution Approach 1:
The patent merges multiple sTTI processing functions into unified scheduling and control mechanisms at the network side. By consolidating the management of multiple short TTIs into a single scheduling framework, the system achieves high data transmission speed through parallel processing while avoiding proportional increases in overall system complexity. The unified scheduler efficiently manages resource allocation across multiple sTTIs without requiring separate complex processing for each interval.
3Loss of time
If hybrid automatic repeat request (HARQ) Round Trip Time (RTT) is reduced, then network responsiveness improves, but protocol complexity increases
Solution Approach 1:
The patent implements preliminary HARQ configuration where acknowledgment timing and retransmission parameters are pre-negotiated and configured before actual data transmission begins. This preliminary setup allows the system to achieve reduced HARQ RTT during actual operation without the complexity of dynamic negotiation during transmission. The pre-configured parameters enable faster automatic retransmission while keeping protocol complexity manageable through standardized pre-agreed rules.
Data Source
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AI summary
Embodiments of latency reduction for wireless data transmission are generally described herein. A user equipment (UE) identifies a shortened transmission time interval (xTTI) length configuration for a time division duplexing (TDD) component carrier (CC), the xTTI length configuration comprising a length in time or a length in orthogonal frequency division multiplexing (OFDM) symbols. The UE identifies scheduling timing and hybrid automatic repeat request (HARQ) timing of physical downlink shared channel (PDSCH) and physical uplink shared channel (PUSCH) on the TDD CC based on the identified xTTI length configuration. The UE signals for transmission of a HARQ acknowledgement (HARQ-ACK) based on the identified xTTI length configuration.