Shortened TTI Uplink Scheduling for Latency Reduction
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Solution Overview
Problem
Current LTE communication systems experience latency due to the 8 ms round trip delay in Hybrid Automatic Repeat Request (HARQ) processes, which is caused by the 1 ms minimum Transmission Time Interval (TTI) for uplink transmissions, leading to delayed transmission and reception of communication signals.
Innovation Solution
Implementing a method and apparatus for scheduling uplink transmissions using a shortened Transmit Time Interval (sTTI) of 0.5 ms or less, allowing for reduced latency by configuring User Equipment (UE) to operate in a sTTI mode, where data is transmitted in a Physical Uplink Shared Channel (PUSCH) using a Physical Resource Block (PRB) spanning 0.5 ms or fewer SC-FDMA symbols, and enabling flexible configuration of sTTI operations based on data priority and network conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a 1 ms minimum TTI is used for uplink transmissions, then the system maintains stable operation and compatibility with existing LTE protocols, but the HARQ round trip delay increases to 8 ms, resulting in high latency
Solution Approach 1:
The patent divides the 1 ms TTI into multiple shorter transmission time intervals (e.g., 0.5 ms or smaller). By segmenting the transmission timeline, the system enables multiple HARQ processes to operate in parallel within the same original TTI period, thereby reducing the round trip delay for each individual transmission while maintaining overall system stability through structured resource allocation.
Solution Approach 2:
The patent introduces dynamic TTI length adjustment, allowing the system to flexibly switch between different TTI durations (e.g., 1 ms, 0.5 ms, or shorter) based on traffic conditions and latency requirements. This dynamic adaptation enables the system to optimize between stability and latency reduction by selecting appropriate TTI lengths for different operational scenarios.
2Loss of time
If the TTI is shortened to reduce latency, then the HARQ round trip delay decreases, but the scheduling complexity and resource management difficulty increase
Solution Approach 1:
The patent systematically varies key parameters including TTI length, the number of parallel HARQ processes, and resource block allocation patterns. By carefully adjusting these parameters, the system achieves latency reduction while managing scheduling complexity through standardized parameter sets that can be pre-configured and optimized for different deployment scenarios.
Solution Approach 2:
The patent introduces intermediate control mechanisms and signaling protocols that mediate between the shortened TTI requirements and the existing LTE framework. These intermediaries include new control channels, signaling messages, and coordination procedures that manage the increased scheduling complexity while enabling the benefits of shorter TTIs.
3Productivity
If multiple HARQ processes are implemented in parallel to reduce latency, then the transmission speed increases, but the resource allocation complexity and interference management difficulty worsen
Solution Approach 1:
The patent segments the available time-frequency resources into distinct allocations for each parallel HARQ process. By dividing resources systematically among multiple processes, the system enables high-speed parallel transmissions while managing resource allocation complexity through structured, non-overlapping resource assignments that can be tracked and managed independently.
Solution Approach 2:
The patent utilizes additional resource dimensions (such as frequency division, code division, or spatial division) to separate multiple HARQ processes. By transitioning from purely time-based multiplexing to multi-dimensional resource allocation, the system increases transmission speed through parallel processes while reducing interference management complexity through orthogonal separation in multiple domains.
Data Source
AI summary
A method and apparatus schedule uplink transmissions with reduced latency. A device can transmit a sidelink transmission in an in a transmit time interval. The device can transmit an uplink transmission in the same transmit time interval as the sidelink transmission.