CSI-RS Mobility Measurement for Additional Carriers Without CRS
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Solution Overview
Problem
Conventional LTE systems face challenges in measuring Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ) for new carriers without Cell-specific Reference Signals (CRS), necessitating an alternative technique for mobility measurements in wireless terminals.
Innovation Solution
The implementation of a technique using Channel State Information (CSI) reference signals (CSI-RS) for mobility measurements, which involves signal power estimation and noise plus interference power estimation using muted CSI-RS, allowing wireless terminals to determine RSRP and RSRQ without CRS, and communicating these measurements to the base station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CRS is not transmitted on an additional carrier to improve spectral efficiency, then spectral efficiency is improved, but mobility measurement capability deteriorates
Solution Approach 1:
The patent extracts the reference signal function from CRS and implements it separately using CSI-RS. The CSI-RS is configured specifically for mobility measurement purposes, allowing CRS to be removed for spectral efficiency while maintaining measurement capability through the extracted CSI-RS mechanism.
Solution Approach 2:
The patent makes CSI-RS serve multiple functions: it provides channel state information for MIMO operations and simultaneously enables mobility measurements (RSRP/RSRQ) for handover decisions. This multi-functionality allows a single signal type to replace the traditional CRS role in mobility measurements.
2Productivity
If a new carrier type is introduced for carrier aggregation to enhance spectral efficiency, then spectral efficiency is improved, but compatibility with existing LTE Rel. 8/9/10 UE deteriorates
Solution Approach 1:
The patent enables existing LTE UE to perform mobility measurements on new carrier types by making CSI-RS serve the dual purpose of channel state information provision and mobility measurement reference. This universality allows backward compatibility while supporting new carrier functionalities.
Solution Approach 2:
The patent changes the measurement parameters from CRS-based RSRP/RSRQ to CSI-RS based measurements. By adjusting the reference signal type and measurement configuration parameters, the system achieves compatibility between existing UE and new carrier types without requiring UE capability changes.
3Reliability
If CSI-RS density is increased to provide robust support for mobility measurements, then measurement reliability is improved, but signal overhead increases
Solution Approach 1:
The patent applies different CSI-RS densities in different regions or scenarios. Instead of uniformly increasing density across the entire system, the configuration allows localized adjustment of CSI-RS density based on specific measurement requirements, traffic conditions, and channel characteristics, thereby improving reliability where needed while controlling overall overhead.
Data Source
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AI summary
A system and a method for a mobility measurement in a wireless network comprises determining at a wireless terminal a channel power estimation E s for a carrier signal based on Channel State Information Reference Signals (CSI RS), and determining at the wireless terminal a noise plus interference I+N for the carrier signal based on a muted CSI RS. The carrier signal is an additional carrier without the presence of a Cell-specific Reference Signal. In one exemplary embodiment, the periodicity of the CSI RS is selected to be 1, 2 or 3 subframes.