LTE NR Reference Signal Collision Management
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Solution Overview
Problem
The coexistence of LTE and NR in shared spectrum leads to collisions between their reference signals, resulting in degraded performance for either technology due to identical time and frequency resource grids.
Innovation Solution
Implementing methods to selectively puncture LTE CRS symbols overlapping NR DMRS symbols, reduce the number of NR DMRS symbols, and use collision-aware channel estimation in UE receivers to mitigate signal collisions, allowing for reduced performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If LTE and NR use identical time and frequency resource grids for spectrum coexistence, then spectrum utilization is improved, but reference signal collisions occur causing performance degradation
Solution Approach 1:
The patent extracts and removes the conflicting reference signal components (LTE CRS or NR DMRS) from the resource grid at collision points. The network node identifies overlapping reference signal resources and selectively punctures (removes) the transmission of one reference signal type to eliminate collisions, allowing both LTE and NR to coexist in the same spectrum without mutual interference.
Solution Approach 2:
The patent applies different transmission qualities to different parts of the resource grid. Instead of uniformly transmitting all reference signals across the entire grid, the system applies local puncturing only at specific resource elements where collisions occur. This preserves the quality of non-colliding reference signals while removing only the problematic overlapping portions.
2Measurement precision
If reference signal transmission is maintained without puncturing, then channel estimation accuracy is improved, but signal collisions increase causing performance degradation
Solution Approach 1:
The patent converts the harmful effect of reference signal collisions into a beneficial outcome by using the collision detection mechanism to trigger selective puncturing. The system identifies where collisions would occur and proactively removes those specific reference signal transmissions, transforming the potential harm of collisions into the benefit of collision-free operation while maintaining overall system performance.
3Object-affected harmful factors
If NR DMRS symbols are reduced to avoid collisions, then collision interference is reduced, but demodulation reference signal availability decreases
Solution Approach 1:
The patent extracts only the specific NR DMRS symbols that collide with LTE CRS symbols and removes them selectively, rather than reducing the overall quantity of NR DMRS symbols. This targeted extraction approach eliminates collision interference while preserving the maximum possible number of reference signals for channel estimation and demodulation functions.
Data Source
AI summary
Embodiments of methods in a base station and a UE are disclosed. In some embodiments, a method implemented in a network node includes any one or more of: selectively puncturing transmission of LTE CRS symbols that overlap NR DMRS symbols in a downlink transmission time interval; selectively puncturing transmission of NR DMRS symbols that overlap LTE CRS symbols in the downlink transmission time interval; and selectively reducing a number of NR DMRS symbols transmitted to the UE in the downlink transmission time interval. In some embodiments, a method implemented in a UE includes identifying, in a downlink channel, subchannels containing NR DMRS symbols that are corrupted due to collision with LTE CRS symbols. For each identified subchannel: a respective time averaged channel estimate is determined based on NR DMRS symbols that are not corrupted due to collision with the LTE CRS symbols; and a respective MMSE weight is determined using the time averaged channel estimate.