NR Base Station CRS Muting for Spectrum Sharing
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Solution Overview
Problem
In spectrum sharing between New Radio (NR) and Long Term Evolution (LTE) base stations, certain NR messages cannot perform LTE Cell Specific Reference Signal (CRS) rate matching, leading to interference and decoding issues due to LTE CRS, resulting in a 1.5 dB Signal-to-Noise ratio gap and increased Physical Resource Blocks (PRBs) usage.
Innovation Solution
A method is implemented where the NR base station indicates to the shared resource allocator that certain NR messages cannot perform LTE CRS rate matching, prompting the LTE base station to mute CRS on specific resources during transmission, thereby reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LTE CRS is transmitted normally in spectrum sharing, then LTE coverage and reference signal functionality are maintained, but NR messages that cannot perform CRS rate matching experience interference and decoding failures
Solution Approach 1:
The NR base station performs preliminary identification of messages that cannot perform CRS rate matching (such as random access messages, paging messages, and RRC messages) before transmission. The scheduler marks these messages in advance and triggers CRS muting on the LTE side for the specific time-frequency resources where these vulnerable NR messages will be transmitted, preventing interference before it occurs.
Solution Approach 2:
Instead of muting CRS across the entire LTE carrier, the solution applies CRS muting selectively only on the specific resource blocks and time slots where vulnerable NR messages are transmitted. This localized approach maintains LTE CRS functionality in other regions while eliminating interference only where necessary for NR message protection.
2Reliability
If existing solutions use lowest modulation and coding scheme to counter LTE interference, then some NR messages can be transmitted, but there is still a 1.5 dB SNR gap compared to no CRS interference and increased PRB usage
Solution Approach 1:
The solution converts the harmful LTE CRS signal into a beneficial muted state specifically for the duration and resources needed by vulnerable NR messages. By coordinating between NR and LTE schedulers, the LTE CRS is muted only when and where NR vulnerable messages are transmitted, transforming the interference source into a non-interfering state precisely when needed, thereby eliminating the 1.5 dB SNR gap and reducing PRB requirements.
3Productivity
If spectrum sharing is implemented between NR and LTE base stations, then spectrum utilization efficiency is improved, but coordination complexity increases and interference management becomes more difficult
Solution Approach 1:
The NR base station's scheduler acts as an intermediary that identifies vulnerable NR messages and communicates their resource requirements to the LTE base station. This coordination mechanism enables the LTE scheduler to mute CRS appropriately without requiring complex bidirectional negotiation, simplifying the overall system coordination while maintaining effective interference management.
Data Source
AI summary
Embodiments described herein relate to methods and apparatuses for a New Radio base station that is spectrum sharing with a Long Term Evolution base station. A method in a first scheduler for use in a New Radio base station includes determining that one or more NR messages are to be scheduled for transmission during a time period, wherein the one or more NR messages cannot perform LTE Cell Specific Reference Signal, CRS, rate matching; and responsive to the determination, transmitting a first indication that there are one or more NR messages that cannot perform LTE CRS rate matching to be transmitted during the time period to a shared resource allocator configured to allocate resources to the NR base station and the LTE base station.