UE-Specific DMRS Synchronization for Dynamic Transmission Point Switching
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Solution Overview
Problem
In wireless communication systems, especially in LTE-Advanced, dynamic switching between transmission points can lead to performance issues due to unsynchronized frequency references, resulting in reduced throughput and increased retransmissions, as user equipment (UE) may not detect changes in transmission points and face challenges in maintaining optimal time and frequency synchronization.
Innovation Solution
The UE uses a user equipment specific demodulation reference signal (DMRS) for synchronization instead of relying solely on the serving cell's Primary Synchronization Signal (PSS), Secondary Synchronization Signal (SSS), and Common Reference Symbol (CRS), with explicit or implicit signaling indicating when the frequency reference changes, allowing for dynamic adaptation and synchronization adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the UE uses the serving cell's PSS, SSS, and CRS for synchronization, then the synchronization process is simple and standardized, but the UE cannot detect changes in transmission points and loses frequency reference accuracy during dynamic switching
Solution Approach 1:
The patent segments the synchronization reference signals into two types: common reference signals (PSS, SSS, CRS) for initial and coarse synchronization, and UE-specific DMRS for fine frequency reference tracking. This segmentation allows the system to maintain both simplicity in the basic synchronization process and accuracy during dynamic transmission point switching by using the appropriate reference type for each stage.
Solution Approach 2:
The patent introduces DMRS as an intermediary reference signal that bridges the gap between common synchronization signals and the need for continuous frequency tracking during dynamic switching. The DMRS carries frequency reference information that helps the UE maintain accurate synchronization when switching between transmission points, acting as a mediator between the standardized common signals and the dynamic requirements of CoMP operations.
2Adaptability or versatility
If the system implements dynamic switching between transmission points, then the system adaptability and throughput are improved, but the UE faces challenges in maintaining optimal time and frequency synchronization
Solution Approach 1:
The patent applies preliminary action by having the network pre-configure multiple transmission points and pre-synchronize their reference signals before dynamic switching occurs. The common reference signals from multiple transmission points are prepared in advance with known frequency relationships, allowing the UE to quickly and reliably switch between points without losing synchronization stability during the actual dynamic switching operation.
Solution Approach 2:
The patent implements feedback mechanisms where the UE monitors the quality of received reference signals from different transmission points and reports back to the network. Based on this feedback, the network can optimize the selection and configuration of transmission points, ensuring that the UE maintains reliable synchronization by switching to the best available transmission point while adapting to changing channel conditions.
3Ease of manufacture
If the UE relies on common reference signals for synchronization, then the implementation is standardized and compatible, but the UE data throughput decreases and retransmissions increase during transmission point switching
Solution Approach 1:
The patent merges the functions of common reference signals and UE-specific reference signals into a unified synchronization framework. The common PSS, SSS, and CRS provide standardized initial synchronization and cell identification, while the UE-specific DMRS provides continuous frequency tracking and channel estimation. This combination maintains implementation compatibility with existing standards while enabling high throughput during dynamic switching by utilizing both reference signal types together.
Solution Approach 2:
The patent changes the parameter of frequency reference accuracy by introducing UE-specific DMRS with dedicated frequency reference information. This parameter change allows the system to move from the standardized but less accurate common reference signals to a more accurate UE-specific reference system during dynamic switching, thereby increasing data throughput and reducing retransmissions while maintaining compatibility through the layered approach.
Data Source
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AI summary
A method comprising: receiving at a user equipment a user equipment specific signal; using said user equipment specific signal to obtain synchronization information with respect to a transmission point.