Shorter TTI Downlink Control Information Design for Latency Reduction
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Solution Overview
Problem
Current wireless communication systems face challenges in reducing packet data latency, which affects both responsiveness and throughput, particularly due to the fixed and longer transmission time intervals (TTIs) in 3GPP LTE networks.
Innovation Solution
The implementation of shorter transmission time intervals (S-TTIs) and innovative downlink control information (DCI) formats that allow for multiple shorter TTIs within a given time window, along with discontinuous reception (DRX) indicators and S-TTI release indicators, to reduce latency and optimize resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If shorter transmission time intervals (S-TTIs) are implemented, then packet latency is reduced and system responsiveness is improved, but device complexity and processing overhead increase
Solution Approach 1:
The patent divides a traditional 1ms TTI into multiple shorter S-TTIs (e.g., two 0.5ms S-TTIs or four 0.25ms S-TTIs). Each S-TTI is further segmented into distinct phases: control phase for Downlink Control Information (DCI) transmission, data phase for user data transmission, and acknowledgment phase for HARQ feedback. This segmentation enables independent processing and transmission of control and data, reducing overall latency while distributing processing tasks across multiple smaller intervals.
Solution Approach 2:
The patent implements preliminary action by transmitting DCI in advance during the control phase of each S-TTI, before the actual data transmission begins. The DCI contains scheduling information, resource allocations, and control commands that prepare the UE for upcoming data transmission. This preliminary control signaling enables the UE to prepare reception and processing resources beforehand, reducing processing overhead during the data phase.
2Productivity
If multiple S-TTIs are monitored within a time window, then resource allocation efficiency is improved, but power consumption increases due to continuous monitoring
Solution Approach 1:
The patent implements periodic action through discontinuous reception (DRX) mechanisms where the UE monitors S-PDCCH only during specific periodic intervals rather than continuously. The network configures DRX cycles with active monitoring periods followed by sleep periods. During active periods, the UE monitors for DCI in S-TTIs; during sleep periods, the UE powers down monitoring circuits to save energy. This periodic monitoring maintains resource allocation efficiency while significantly reducing average power consumption compared to continuous monitoring.
Solution Approach 2:
The patent applies dynamics by making the monitoring behavior adaptive based on traffic conditions and network configuration. The UE dynamically adjusts its monitoring pattern according to DRX configurations received from the network, transitioning between different monitoring states (full monitoring, partial monitoring, or no monitoring) based on current resource allocation needs. This dynamic approach optimizes the balance between resource allocation efficiency and power consumption in real-time.
Data Source
AI summary
Downlink control information techniques for wireless communications with shorter TTI (S-TTI) length are disclosed. An apparatus of a user equipment (UE) can include processing circuitry configured to decode signaling indicating a duration of a time window, the time window comprising a plurality of S-TTIs forming a single TTI. Absence of a discontinuous reception (DRX) indicator is detected within control information received within a first S-TTI of the plurality of S-TTIs. Upon detecting the absence of the DRX indicator within received control information, a S-PDCCH within each of the plurality of S-TTIs is monitored during the duration. Scheduling information received via the S-PDCCH within one of the plurality of S-TTIs is decoded, and data is encoded for transmission on a shared data channel based on the scheduling information.