Sub-tiled Reference Signal Design for 5G Overhead Reduction

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Solution Overview

Problem

Current wireless communication systems face high overhead and inefficiency in channel state information (CSI) transmission due to inflexible reference signal designs, particularly in 4G LTE, which are not suitable for varying user equipment mobility patterns, leading to increased latency and resource wastage in 5G network development.

Innovation Solution

The method involves sub-tiling reference signals within resource elements, dispersing them across frequency bins and time slots according to a pre-defined grid, allowing each sub-tiled signal to occupy less time, frequency, and power extent, enabling flexible combination and transmission, thereby reducing overhead and improving channel estimation accuracy for diverse user equipment scenarios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If common reference signals (CRS) are transmitted in every physical resource block to support high speed UEs, then channel estimation capability for fast moving UEs is improved, but reference signal overhead increases to 5-10%

Engineering Contradiction:

Improvechannel estimation capabilityVSAvoidreference signal overhead

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The reference signal is segmented into two distinct types: CSI-RS for nomadic users and CRS for high-speed users. This segmentation allows each reference signal type to be optimized for its specific use case, with CSI-RS transmitted sparsely (every 5-180ms) to reduce overhead for stationary users, while CRS is transmitted continuously only where needed for high-speed users, thereby reducing overall overhead while maintaining reliable channel estimation for both user types

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different reference signal qualities and transmission densities are applied locally based on user mobility characteristics. Nomadic users receive sparse CSI-RS transmissions optimized for frequency-selective channels, while high-speed users receive dense CRS transmissions optimized for time-variant channels. This local quality differentiation ensures each user type receives appropriate channel estimation capability without imposing unnecessary overhead on all users

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If CSI-RS are transmitted sparsely to reduce overhead for nomadic users, then reference signal overhead is reduced, but channel estimation accuracy for frequency selective channels deteriorates

Engineering Contradiction:

Improvereference signal overheadVSAvoidchannel estimation accuracy

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The system dynamically adapts the reference signal transmission density and type based on user mobility state and channel characteristics. For nomadic users in frequency-selective channels, CSI-RS are transmitted at optimized intervals (5-180ms) with appropriate frequency spacing to capture channel variations. For high-speed users in time-variant channels, CRS are transmitted continuously with denser time spacing. This dynamic adaptation maintains measurement precision for each user type while optimizing overall overhead

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If both CSI-RS and CRS are combined to support different user types, then versatility of channel estimation is improved, but signaling overhead increases

Engineering Contradiction:

Improvesupport for different user mobility patternsVSAvoidsignaling overhead

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The reference signal resource is segmented into dedicated pools: CSI-RS resources for nomadic users and CRS resources for high-speed users. Each user type is assigned appropriate reference signal resources based on their mobility characteristics, avoiding the need for all users to receive both types. This segmentation maintains versatility in supporting different user types while preventing the overhead accumulation that would result from universal transmission of both reference signal types

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system creates a universal reference signal framework where a single infrastructure supports multiple user types through appropriate resource allocation. The base station can dynamically assign CSI-RS or CRS resources to different users based on their mobility state, and users can be configured to use either or both reference signal types as needed. This multi-functional approach provides versatility without requiring permanent overhead for all reference signal types simultaneously

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS10911106B2Flexible reference signal design

Publication Date: 2021.02.02 NOKIA TECHNOLOGIES OY

AI summary

A radio network sub-tiles reference signals (RSs) within a set of resource elements (REs) such that each sub-tiled RS occupies less than a time and/or frequency and/or power extent of its respective RE. The set of REs are dispersed across both frequency bins and time slots according to a pre-defined grid; and transmitted. The user equipment (UE) uses that pre-defined grid to locate within that transmission the set of dispersed REs. The UE accumulates and combines at least one subset of the sub-tiled RSs and estimates therefrom a quality; then reports uplink an indication of that estimated quality. Examples of the RSs include channel state information RSs, beam RSs and beam refinement RSs. Advantages are particularly relevant for 5G new radio systems.