Downlink Dedicated Pilots Mapping for LTE Beamforming Overhead

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Solution Overview

Problem

The existing LTE standard cannot acquire all channel information when more than 4 antennas are used for beamforming, leading to feedback overhead issues with beamforming weight-values.

Innovation Solution

A method for mapping downlink dedicated pilots to resource elements in the Extended CP frame structure, specifically positioning them in a physical resource block with a time-domain interval of 2-3 OFDM symbols and a frequency-domain interval of 2 subcarriers, ensuring even distribution and alignment with cell-specific reference signals to support beamforming with lower overhead and superior performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the number of cell-specific reference signals is increased to support more than 4 antenna ports, then the beamforming capability is improved, but the reference signal overhead increases significantly

Engineering Contradiction:

Improvebeamforming capabilityVSAvoidreference signal overhead

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent divides the reference signal function into two segments: cell-specific reference signals (for basic channel estimation) and downlink dedicated pilots (for beamforming-specific channel information). This segmentation allows each type of signal to serve its specific purpose efficiently, avoiding the need to increase cell-specific reference signals for beamforming support.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces downlink dedicated pilots as an intermediary signal specifically for beamforming operations. These pilots act as a mediator between the transmitted beamformed signals and the channel estimation process, enabling accurate beamforming without requiring additional cell-specific reference signals.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If cell-specific reference signals are used to extract channel information for more than 4 antennas, then the channel estimation is simplified, but the real channel information of each antenna cannot be acquired

Engineering Contradiction:

Improvechannel estimationVSAvoidchannel information accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent applies local quality by making different reference signals serve different purposes: cell-specific reference signals provide general channel estimation, while downlink dedicated pilots provide antenna-specific beamforming channel information. Each signal type is optimized for its specific function, ensuring both ease of operation and measurement precision.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent performs preliminary action by pre-configuring downlink dedicated pilots with specific time-domain and frequency-domain mapping patterns before transmission. This preliminary setup ensures that the pilots are positioned optimally to capture accurate channel information for beamforming without requiring complex real-time processing.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If beamforming weight-value feedback is implemented to compensate for insufficient channel information, then the beamforming performance is maintained, but the feedback overhead increases

Engineering Contradiction:

Improvebeamforming performanceVSAvoidfeedback overhead

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent enables self-service by allowing the downlink dedicated pilots to automatically provide the necessary channel information for beamforming without requiring external feedback mechanisms. The pilots contain embedded channel state information that the receiver can extract directly, eliminating the need for beamforming weight-value feedback.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS8391233B2Method for mapping downlink dedicated pilots to resource elements in extended cyclic prefix frame structure

Publication Date: 2013.03.05 ZTE CORP

AI summary

A method for mapping downlink dedicated pilots to resource elements in an Extended Cyclic Prefix frame structure, applied in a long term evolution system, includes the following steps: the first downlink dedicated pilot of each port is mapped to the specific position of a physical resource block; other downlink dedicated pilots of the port are mapping-processed according to the time-domain interval, frequency-domain interval and a preset regulation; the time-domain interval is two or three OFDM symbols, and the frequency-domain interval is two subcarriers of the same time domain. By defining the positions of pilots in the physical resource block, downlink dedicated pilots can obtain the information of all channels when a base station uses a beamforming of more than four antennas. Making the channel information obtained by dedicated pilots contain the real channel information and the process-weight-value of a beamforming, a UE does not need to obtain the transmission-weight-value of a beamforming, thereby avoiding the feedback overhead of beamforming weight-values.