DM-RS Sharing for Short TTI Latency Reduction
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Solution Overview
Problem
Current wireless communication systems, particularly 3GPP LTE, face challenges in reducing packet data latency, which affects system responsiveness, throughput, and resource efficiency, and is not adequately addressed by existing pre-scheduling strategies or short transmission time intervals (TTIs).
Innovation Solution
The method involves configuring multiple short TTIs, each shorter than 1 ms, and sharing a demodulation reference signal (DM-RS) among user equipment (UEs) and eNodeB, allowing for efficient DM-RS transmission by indicating a reference TTI for DM-RS sharing, either within a set of short TTIs or across different UEs, to reduce overhead and enhance data reception performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If multiple short TTIs are configured in a subframe, then latency is reduced and transmission responsiveness is improved, but DM-RS overhead increases and radio resource efficiency deteriorates
Solution Approach 1:
The patent merges DM-RS resources across multiple short TTIs by configuring a reference TTI that provides DM-RS for both the reference TTI itself and a target TTI. This combining approach allows the system to achieve low latency through multiple short TTIs while reducing overall DM-RS overhead by reusing the same reference signal across different time intervals.
2Reliability
If DM-RS is transmitted in every short TTI, then data reception reliability is maintained, but radio resource efficiency decreases and buffering requirements increase
Solution Approach 1:
The patent implements preliminary action by transmitting DM-RS in advance in a reference TTI before the actual data transmission in the target TTI. This allows the receiver to prepare channel estimates ahead of time, maintaining reliable data reception while avoiding the need to transmit redundant DM-RS in every subsequent short TTI, thereby improving radio resource efficiency.
3Speed
If shorter TTI duration is used, then system responsiveness and latency are improved, but the number of transmission attempts within a delay bound increases requiring more buffering
Solution Approach 1:
The patent ensures continuity of useful action by establishing a systematic relationship between reference TTIs and target TTIs, where DM-RS transmitted in the reference TTI continuously supports data reception across multiple target TTIs. This continuous utilization of the same reference signal reduces the need for additional buffering while maintaining high system responsiveness through frequent short TTI transmissions.
Data Source
AI summary
Multiple short transmission time intervals (TTIs), each of which is shorter than 1 ms, may be configured in a subframe. A user equipment (UE) may transmit a demodulation reference signal (DM-RS) which is shared among different UEs to an eNodeB (eNB). In this case, the DM-RS may be transmitted in a reference TTI, which is one short TTI among the multiple short TTIs, and the reference TTI may be indicated by downlink control information (DCI) received from the eNB. Alternatively, a UE may transmit the DM-RS which is shared among different short TTIs to the eNB.