CoMP Frequency Offset Compensation for UE Reception

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Solution Overview

Problem

In cooperative multi-point (CoMP) transmission environments, large frequency offsets between transmission points degrade the reception capability of user equipment (UE) in 3GPP LTE systems, particularly when the frequency offset between cooperative points is significant.

Innovation Solution

The method involves determining the frequency offset between the cell-specific reference signal (CRS) and the quasi co-located demodulation-reference signal (DM-RS) and compensating for it when the offset exceeds 50 Hz, using a radio resource control (RRC) signal to indicate quasi co-location, ensuring accurate channel state estimation and data demodulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If cooperative multi-point (CoMP) transmission is implemented, then transmission capacity and coverage are improved, but reception capability deteriorates when frequency offset between transmission points is large

Engineering Contradiction:

Improvetransmission capacityVSAvoidreception capability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the frequency synchronization parameter by introducing frequency offset estimation and compensation mechanisms. The UE estimates frequency offset between CRS and DM-RS from different transmission points and applies compensation to maintain frequency alignment, thereby resolving the reception capability degradation caused by large frequency offsets in CoMP transmission

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements a feedback mechanism where the UE measures frequency offset between reference signals from different transmission points and reports this information back to the network. The network uses this feedback to adjust frequency synchronization, enabling continuous optimization of reception capability in CoMP environments

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If frequency offset between cooperative points increases, then transmission flexibility is improved, but modulation performance deteriorates

Engineering Contradiction:

Improvetransmission flexibilityVSAvoidmodulation performance

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent performs preliminary frequency offset estimation and compensation before data demodulation. By estimating the frequency offset between CRS and DM-RS in advance and applying compensation, the system maintains accurate frequency alignment for modulation, preventing performance degradation while preserving transmission flexibility

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9768898B2Method for reception in cooperative transmission environment and terminal

Publication Date: 2017.09.19 LG ELECTRONICS INC

AI summary

One embodiment of the present specification provides a reception method for a terminal supporting cooperative multi-point (CoMP). The reception method for the terminal may comprise the steps of: receiving a signal which indicates that a channel state indicator-reference signal (CSI-RS) port and a cell-specific reference signal (CRS) port are almost quasi co-located; and determining a frequency offset between a CRS and a demodulation-reference signal (DM-RS), which is quasi co-located with the CRS, on the basis of the signal which indicates that the CSI-RS port and the CRS port are almost quasi co-located. Herein the frequency offset between the CRS and the DM-RS may be within 50 Hz.