Uplink DMRS Multiplexing for Cross-Link Interference Rejection
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Solution Overview
Problem
In dynamic TDD systems, the interference between downlink and uplink communications in adjacent cells hampers the reception of demodulation reference signals, leading to ineffective interference rejection and desired signal processing in target cells.
Innovation Solution
A user equipment apparatus is equipped with a reception unit to receive control information for uplink demodulation reference signal resources and a transmitting unit to multiplex these signals into specific symbols at the beginning of data segments in subframes, allowing for effective interference rejection by muting resources in the target cell to isolate cross-link interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dynamic TDD is used to flexibly control downlink and uplink resources in each cell, then traffic accommodation efficiency is improved, but cross-link interference between cells increases
Solution Approach 1:
The patent segments the time-frequency resources by introducing specific symbols at the beginning of data segments where DMRS is transmitted. This segmentation allows the target cell to isolate and process reference signals separately from interfering downlink data transmissions in adjacent cells, thereby maintaining flexible resource control while mitigating cross-link interference.
Solution Approach 2:
The patent introduces demodulation reference signals (DMRS) as an intermediary element that enables the target cell to estimate and reject cross-link interference. The DMRS acts as a mediator that carries channel state information necessary for interference rejection processing, allowing the system to maintain dynamic TDD flexibility while compensating for the harmful interference effect.
2Productivity
If downlink communication in an interfering cell is transmitted simultaneously with uplink communication in a target cell, then resource utilization is improved, but demodulation reference signal reception in the target cell deteriorates
Solution Approach 1:
The patent applies local quality by transmitting DMRS in specific localized symbols at the beginning of data segments in the target cell. These localized reference signal transmissions are designed to be robust against downlink interference, enabling accurate channel estimation and interference rejection even when downlink communication occurs simultaneously in interfering cells.
Solution Approach 2:
The patent implements preliminary action by transmitting DMRS at the very beginning of data segments before the main data transmission occurs. This timing allows the target cell to perform channel estimation and interference rejection processing in advance, preparing the reception system to handle subsequent uplink data transmission even while downlink communication is active in interfering cells.
3Measurement precision
If interference rejection processing is performed using ideal MMSE receiver weight, then signal demodulation accuracy is improved, but computational workload increases
Solution Approach 1:
The patent extracts only the necessary channel state information from DMRS that is required for interference rejection processing. By using DMRS-based MMSE receiver weight calculation instead of ideal MMSE that requires complete interference signal component estimation, the system extracts just the essential information needed to reject cross-link interference, significantly reducing computational workload while maintaining adequate demodulation accuracy.
Data Source
AI summary
A user equipment apparatus in a radio communication system in which uplink communication and downlink communication are dynamically changed includes a reception unit configured to receive, from a base station, control information indicating a resource for an uplink demodulation reference signal in a subframe used for transmitting uplink data; and a transmitting unit configured to transmit the uplink demodulation reference signal according to the control information; wherein the resource for the uplink demodulation reference signal is multiplexed into a part of resources corresponding to one or more symbols at a beginning of a data segment in the subframe used for transmitting the uplink data.