LTE-NR Reference Signal Coexistence With Dynamic DMRS Placement
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Solution Overview
Problem
In wireless communication systems where LTE and NR operate on the same frequency band, the configuration of additional NR DMRS symbols can collide with LTE CRS, leading to channel estimation corruption and degraded performance.
Innovation Solution
The NR DMRS symbols are moved away from colliding symbol positions when LTE CRS are present, and this is signaled to the wireless device using parameters like lte-CRS-ToMatchAround, ensuring NR PDSCH can be transmitted across the entire slot, thereby increasing throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional NR DMRS symbols are configured to improve channel estimation accuracy, then measurement precision is improved, but collisions with LTE CRS occur causing channel estimation corruption
Solution Approach 1:
The patent implements dynamic DMRS symbol positioning where the network node can flexibly adjust the symbol positions of NR DMRS based on the presence and configuration of LTE CRS. This dynamic adaptation allows the system to maintain optimal channel estimation accuracy while avoiding collisions with LTE reference signals, thereby preserving reliability.
Solution Approach 2:
The patent changes the temporal parameter (symbol position) of NR DMRS to resolve collisions with LTE CRS. By modifying the time-domain location of DMRS symbols rather than their frequency-domain characteristics, the system maintains measurement precision while eliminating harmful interactions with LTE reference signals.
2Reliability
If NR DMRS symbols are moved away from colliding positions to avoid LTE CRS collisions, then reliability is improved, but the number of available resource elements for data transmission decreases
Solution Approach 1:
The patent applies preliminary action by pre-planning and signaling the adjusted DMRS symbol positions to wireless devices before data transmission occurs. This allows the system to establish collision-free reference signal positions in advance, ensuring reliable channel estimation while maximizing the remaining resource elements available for productive data transmission.
Solution Approach 2:
The patent uses signaling parameters (lte-CRS-ToMatchAround, nrofCRS-Ports) to convey information about LTE CRS configuration to NR wireless devices. This copying of CRS position information enables devices to independently determine appropriate DMRS positions that avoid collisions, maintaining both reliability and productivity without requiring direct interference management.
3Reliability
If LTE CRS is transmitted continuously to maintain mobility and cell detection functionality, then reliability is improved, but resource element availability for NR transmissions is reduced
Solution Approach 1:
The patent segments the time-frequency resource grid by identifying and marking resource elements occupied by LTE CRS. This segmentation allows the NR system to allocate DMRS and data around these protected CRS positions, ensuring LTE reliability for mobility and cell detection while maximizing NR productivity in the remaining resources.
Solution Approach 2:
The patent introduces signaling parameters as an intermediary mechanism that conveys LTE CRS configuration information to NR wireless devices. This intermediary allows NR devices to adapt their DMRS positioning and data mapping without directly interfering with continuous LTE CRS transmissions, thereby maintaining both LTE reliability and NR productivity.
Data Source
AI summary
Radio network node, wireless device, and related methods are described. According to one aspect, when a first radio access technology and a second radio access technology are coexisting on the same carrier, the symbol location of the reference signals of the first radio access technology may be moved or changed when the reference signals of the first radio access technology collide with the reference signals of the second radio access technology.