Rate Matching Mode Switching for CSI-RS Interference Mitigation
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Solution Overview
Problem
In LTE-Advanced systems, the introduction of CSI-RS for channel sounding interferes with Rel-8 PDSCH performance, leading to decoding issues due to lack of explicit signaling for UE capability acquisition, resulting in mismatched rate matching modes between eNB and UE, causing interference and performance degradation.
Innovation Solution
Implementing a method where the UE operates in a first rate matching mode until the eNB correctly acquires its capabilities, then switching to a second rate matching mode, which involves rate matching around CSI-RS REs, mitigating interference by explicit or implicit signaling, and configuring UE through RRC connection reconfiguration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CSI-RS is transmitted for channel sounding, then channel state information is improved, but PDSCH performance deteriorates due to interference
Solution Approach 1:
The patent extracts the harmful CSI-RS signals from the PDSCH transmission resources by introducing rate matching, where the eNB identifies and excludes CSI-RS resource elements from the data transmission. This allows the PDSCH to be transmitted without interference from CSI-RS, resolving the contradiction between channel sounding and data transmission performance
Solution Approach 2:
The patent introduces rate matching as an intermediary mechanism between CSI-RS transmission and PDSCH transmission. The eNB uses rate matching to dynamically adjust the PDSCH transmission based on CSI-RS presence, acting as a mediator that coordinates both channel sounding and data transmission to avoid interference
2Reliability
If rate matching mode is changed after capability acquisition, then decoding accuracy is improved, but signaling overhead increases
Solution Approach 1:
The patent applies preliminary action by configuring the UE with multiple rate matching modes in advance through capability acquisition procedures. The eNB pre-configures the UE with different rate matching configurations (first and second rate matching modes) before actual transmission, so that when rate matching needs to be changed, the UE already has the necessary configuration information, reducing the need for extensive real-time signaling
Solution Approach 2:
The patent introduces dynamics by allowing the eNB to switch between different rate matching modes (first rate matching mode before capability confirmation, second rate matching mode after capability confirmation) based on the UE's capability acquisition status. This dynamic adaptation enables the system to optimize decoding accuracy while managing signaling overhead through conditional mode switching
3Reliability
If explicit signaling is used for capability acquisition, then rate matching alignment is improved, but signaling overhead increases
Solution Approach 1:
The patent uses feedback mechanisms where the UE provides capability information to the eNB, and the eNB adjusts rate matching modes accordingly. The feedback loop ensures that the eNB and UE are aligned on the correct rate matching mode without requiring constant explicit signaling, as the capability information is exchanged and processed through the existing RRC connection reconfiguration procedures
Data Source
AI summary
In one aspect thereof the exemplary embodiments of this invention provide a method that includes, prior to confirmation that a network access node has correctly acquired capabilities of a user equipment, operating a user equipment with the network access node in accordance with a first rate matching mode and, only after confirmation to the user equipment that the network access node has correctly acquired capabilities of the user equipment, changing the rate matching mode to a second rate matching mode. In an embodiment the first rate matching mode comprises puncturing a downlink shared channel transmission with a set of resource elements, which may be at least one of reference symbols and muted resource elements, and the second rate matching mode comprises rate matching the downlink shared channel around those resource elements that are members of the set of resource elements. Also described are apparatus and computer readable storage medium storing program code that operate in accordance with the method.