Interference DMRS Detection with Serving Signal Cancellation
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Solution Overview
Problem
In Long-Term Evolution (LTE) systems, user equipment (UE) faces interference from unwanted signals that degrade the reception of the desired signal, necessitating a method to model and cancel interfering signals to improve signal quality.
Innovation Solution
The UE determines whether the serving signal is transmitted in a DMRS-based mode and cancels either the serving DMRS or data signal to form a diminished signal, which is then analyzed for power levels of interference DMRS candidates. Hypothesis testing is performed to identify the presence, rank, port number, and scrambling identity of the interference DMRS, using specific power ratio calculations and thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE receives both desired signal and interfering signal simultaneously, then the UE can maintain continuous communication, but the interfering signal degrades the reception quality of the desired signal
Solution Approach 1:
The patent extracts and removes the interfering signal component from the received signal by identifying and canceling the interference DMRS. This is achieved by detecting interference DMRS candidates, determining their parameters (port number, scrambling identity, rank), and subtracting them from the received signal to isolate the desired signal for improved reception quality
Solution Approach 2:
The patent introduces an intermediary process of interference detection and characterization between signal reception and desired signal extraction. By using reference signals (DMRS) as intermediaries to detect and model interfering signals, the system can identify and remove interference components without directly processing the mixed signal, thereby improving reception quality
2Reliability
If the UE performs interference signal cancellation by modeling and removing interfering signals, then the reception of the desired signal is improved, but the complexity of signal processing increases
Solution Approach 1:
The patent segments the interference cancellation process into distinct stages: interference DMRS detection, parameter determination (port number, scrambling identity, rank), interference signal modeling, and signal subtraction. This segmentation allows the UE to systematically handle complex interference cancellation by breaking it down into manageable processing steps, reducing overall system complexity while maintaining reception quality
Solution Approach 2:
The patent performs preliminary interference detection and characterization using DMRS before main signal processing. By detecting and modeling interfering signals in advance using reference signals, the system prepares interference cancellation parameters beforehand, which simplifies the subsequent desired signal extraction process and reduces real-time processing complexity
3Measurement precision
If the UE analyzes power levels of multiple interference DMRS candidates and performs hypothesis testing, then the accuracy of interference characterization is improved, but the processing time and computational load increase
Solution Approach 1:
The patent evaluates a limited set of four interference DMRS candidates with specific port number and scrambling identity combinations rather than exhaustively searching all possible interference configurations. This partial action approach achieves sufficient interference characterization accuracy by focusing on the most likely candidates, thereby reducing processing time and computational load while maintaining detection precision
Data Source
AI summary
A system and method for characterizing an interference demodulation reference signal (DMRS) in a piece of user equipment (UE), e.g., a mobile device. The UE determines whether the serving signal is transmitted in a DMRS-based transmission mode; if it is, the UE cancels the serving DMRS from the received signal; otherwise the UE cancels the serving data signal from the received signal. The remaining signal is then analyzed for the amount of power it has in each of four interference DMRS candidates, and hypothesis testing is performed to determine whether interference DMRS is present in the signal, and, if so, to determine the rank of the interference DMRS, and the port and scrambling identity of each of the interference DMRS layers.