DMRS Sub-subframe Scheduling for Latency Reduction

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Solution Overview

Problem

Conventional demodulation reference signals (DMRS) in wireless communications are scheduled over 1 ms intervals, which does not facilitate shorter scheduling times and higher latency reduction, particularly in LTE networks, impacting packet data latency and radio resource efficiency.

Innovation Solution

Mapping DMRS resource elements to various sub-subframes within a 1 ms subframe, allowing for separate scheduling and precoding of radio transmissions per sub-subframe, thereby reducing latency and improving scheduling efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If DMRS are scheduled over 1 ms intervals, then backwards compatibility is maintained, but latency is increased and scheduling flexibility is reduced

Engineering Contradiction:

ImprovelatencyVSAvoidscheduling flexibility

Core Design Contradiction:

Loss of timeVSAdaptability or versatility

Solution Approach 1:

The patent divides the 1 ms subframe into multiple sub-subframes (e.g., two 0.5 ms sub-subframes), allowing DMRS to be scheduled independently in each sub-subframe. This segmentation enables shorter scheduling intervals and reduced latency while maintaining compatibility with legacy systems that operate on 1 ms intervals.

Inventive Principle:

Principle #1Segmentation

2Productivity

If PDSCH assignments cover the full 1 ms subframe, then resource utilization is maximized, but decoding latency increases

Engineering Contradiction:

Improveresource utilizationVSAvoiddecoding latency

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent segments the PDSCH assignment into multiple sub-subframe assignments, where each sub-subframe assignment covers only a portion of the total data. The UE can decode each sub-subframe independently and earlier, reducing overall decoding latency while still utilizing the full 1 ms resource block allocation.

Inventive Principle:

Principle #1Segmentation

3Loss of time

If HARQ RTT is reduced through shorter subframes, then responsiveness improves, but system complexity increases

Engineering Contradiction:

ImproveHARQ RTTVSAvoidscheduling complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The patent introduces dynamic scheduling where the network can flexibly assign different sub-subframe durations and configurations based on traffic conditions and UE capabilities. This dynamic approach enables reduced HARQ RTT when needed while avoiding unnecessary complexity in scenarios where legacy 1 ms scheduling suffices.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS12133205B2DMRS with shortened scheduling

Publication Date: 2024.10.29 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

According to some embodiments, a network node is operable to separately schedule radio transmissions per sub-subframe (SSF). A method in the network node comprises mapping a first demodulation reference signal (DMRS) to first resource elements in a first SSF. The first resource elements are associated with a first set of antenna ports. The method includes mapping a second DMRS to second resource elements in a second SSF. The second resource elements are associated with the first set of one or more antenna ports and precoding of the second DMRS differs from a precoding of the first DMRS. The method further includes scheduling a radio transmission during the first SSF precoded in accordance with the first DMRS, and scheduling a radio transmission during the second SSF precoded in accordance with the second DMRS. In particular embodiments, a subframe may comprise two, four, or eight sub-subframes.