Reference Signal Density in 5G Wireless Communications
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Solution Overview
Problem
In wireless communication systems, particularly in 5G, the sparse density of channel state information reference signals (CSI-RS) limits the ability of user equipment (UE) to perform fine time/frequency tracking, Doppler spread estimation, and delay spread estimation, as compared to cell-specific reference signals (CRS) in LTE, due to pilot pollution, unnecessary energy consumption, and inflexible resource utilization.
Innovation Solution
The method involves transmitting multiple reference signals over multiple resource elements, associating antenna ports with similar channel characteristics, and configuring these signals to allow for increased density of reference signals, enabling channel measurements without requiring separate tracking signals, thereby enhancing time and frequency tracking capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cell-specific reference signals (CRS) are transmitted with high density in LTE, then fine time/frequency tracking and channel measurement accuracy are improved, but pilot pollution and unnecessary energy consumption increase
Solution Approach 1:
The patent applies local quality by making reference signal transmission selective rather than universal. Specifically, it transmits reference signals only in resource elements where data is actually being transmitted to UEs, rather than across the entire bandwidth. This localized approach maintains tracking accuracy where needed while avoiding energy waste in empty resources.
Solution Approach 2:
The patent implements dynamics by making reference signal transmission flexible and adaptive. The system dynamically adjusts reference signal presence based on actual data transmission patterns, allowing the density and location of reference signals to change according to traffic conditions, thereby optimizing both accuracy and energy efficiency.
2Reliability
If cell-specific reference signals (CRS) are transmitted continuously, then tracking loop performance is maintained, but resource utilization flexibility is reduced
Solution Approach 1:
The patent makes the reference signal transmission dynamic by aligning it with data transmission patterns. Reference signals are transmitted only when and where data is transmitted, allowing the system to adapt resource usage to actual needs while maintaining tracking performance through selective presence of reference signals.
Solution Approach 2:
The patent achieves multi-functionality by using the same reference signal structure to serve both tracking purposes and data transmission purposes. The reference signals are integrated into the data transmission resources rather than being separate dedicated pilots, allowing unified resource utilization for multiple functions.
3Loss of energy
If channel state information reference signals (CSI-RS) are transmitted with sparse density in 5G, then energy consumption is reduced, but fine time/frequency tracking capability deteriorates
Solution Approach 1:
The patent applies local quality by concentrating reference signal energy in specific resource elements where data transmission occurs, rather than distributing sparse signals across the entire bandwidth. This localized concentration maintains effective tracking capability while keeping overall signal density low for energy efficiency.
Solution Approach 2:
The patent changes the parameter of reference signal density from a fixed sparse value to a variable that adapts to data transmission patterns. The effective density increases locally where needed for tracking while remaining low globally for energy efficiency, achieved by modulating presence based on traffic conditions.
Data Source
AI summary
Aspects herein describe increasing density of reference signal transmissions in wireless communications. A plurality of reference signal configurations, each indicating resource elements for one or more antenna ports over which reference signals for the one or more antenna ports are scheduled for transmission, can be received. An association configuration indicating an association between at least two antenna ports as having similar channel characteristics can also be received. A plurality of reference signals can be received in the resource elements corresponding to the at least two antenna ports as indicated in the at least two of the plurality of reference signal configurations, which can be used to perform a channel measurement of the similar channel characteristics of channels of the at least two antenna ports over at least a portion of the plurality of reference signals.