DMRS Mapping Flexibility for Interference and Latency Trade-offs

Solution Overview

Problem

In next-generation mobile communication systems, the reception side faces interference and delay during demodulation of data channels due to the positioning of demodulation reference signals (DMRS) in radio communication systems, particularly in high-density cell environments and scenarios requiring low latency.

Innovation Solution

The proposed solution involves mapping demodulation reference signals (DMRS) to either a fixed symbol within the subframe or to the top symbol of the data channel, allowing for flexible mapping based on communication scenarios to minimize interference and delay, with the radio base station and user terminal configuring the DMRS mapping method dynamically or pre-defining it according to expected communication statuses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If the demodulation RS is mapped to a fixed symbol position in the subframe, then the channel estimation and signal demodulation processing time is reduced, but interference occurs between demodulation RS in different cells or beams

Engineering Contradiction:

Improveprocessing time for channel estimation and signal demodulationVSAvoidinterference between demodulation RS

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by allowing different demodulation RS mapping methods in different regions or scenarios. Specifically, it supports both front-loaded DMRS (mapped to fixed early symbol) and data-first DMRS (mapped after data channel), enabling the system to select the appropriate mapping strategy based on local interference conditions, latency requirements, and channel characteristics, thereby reducing interference while maintaining efficient processing where applicable

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements dynamics by making the demodulation RS mapping position configurable and adaptable rather than fixed. The system can dynamically switch between different mapping methods (front-loaded vs. data-first) based on traffic conditions, interference levels, and service requirements, allowing the mapping strategy to evolve in response to changing network conditions

Inventive Principle:

Principle #15Dynamics

2Object-affected harmful factors

If the demodulation RS is mapped after the data channel symbols, then interference between demodulation RS in different cells is reduced, but the processing time for channel estimation and signal demodulation increases

Engineering Contradiction:

Improveinterference between demodulation RSVSAvoidprocessing time for channel estimation and signal demodulation

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The patent applies local quality by allowing different demodulation RS mapping methods in different regions or scenarios. Specifically, it supports both front-loaded DMRS (mapped to fixed early symbol) and data-first DMRS (mapped after data channel), enabling the system to select the appropriate mapping strategy based on local interference conditions, latency requirements, and channel characteristics, thereby reducing interference while maintaining efficient processing where applicable

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements dynamics by making the demodulation RS mapping position configurable and adaptable rather than fixed. The system can dynamically switch between different mapping methods (front-loaded vs. data-first) based on traffic conditions, interference levels, and service requirements, allowing the mapping strategy to evolve in response to changing network conditions

Inventive Principle:

Principle #15Dynamics

3Quantity of substance

If the number of control symbols is increased to accommodate more control information, then downlink control signaling capacity is improved, but the available resources for data and reference signals are reduced

Engineering Contradiction:

Improvedownlink control signaling capacityVSAvoidavailable resources for data and reference signals

Core Design Contradiction:

Quantity of substanceVSArea of stationary object

Solution Approach 1:

The patent applies another dimension by utilizing the time domain more effectively through flexible DMRS mapping. By allowing DMRS to be positioned either before or after data channels depending on control resource allocation, the system creates additional temporal dimensions for resource organization, enabling better packing of control, data, and reference signals without simple linear trade-offs

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentEP3579510B1User terminal and wireless communication method

Publication Date: 2022.10.19 NTT DOCOMO INC

Figure 1A~1B
Figure 2A~2B
Figure 3

AI summary

In user terminal 20, reception section 202 receives a downlink signal including a data signal and a demodulation reference signal mapped to downlink resources, and control section 203 controls reception of the demodulation reference signal included in the downlink signal based on one of a first mapping method and a second mapping method set to user terminal 20, wherein the demodulation reference signal is mapped to fixed symbols in a subframe in the first mapping method, and the demodulation reference signal is mapped to top symbols of symbols provided with the data signal in the subframe in the second mapping method.