Frequency-Hopped CRS Configuration for Heterogeneous Network Overhead
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Solution Overview
Problem
In LTE wireless communication systems, the existing downlink reference signals, such as CRS, result in significant overhead and are not sufficient for efficient time and frequency tracking in heterogeneous networks with unsynchronized carriers, particularly in scenarios where legacy and new type cells are not accurately synchronized, necessitating a reduction in common signal transmission to enhance spectral efficiency and energy saving.
Innovation Solution
The implementation of a frequency-hopped CRS-based reference signal with reduced overhead, where CRS is transmitted in a limited number of resource blocks and symbols, and the hopping patterns are signaled through RRC, allowing for efficient time and frequency tracking, and enabling reliable channel quality measurements across the bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CRS is transmitted to all UEs based on the largest number of MIMO layers/ports, then channel estimation and synchronization are improved, but signaling overhead increases
Solution Approach 1:
The patent applies local quality by configuring different CRS parameters (number of antenna ports, frequency density, time density) specifically for small cell carriers rather than using uniform configuration across all carriers. This allows CRS to be transmitted with appropriate density only where needed for reliable channel estimation in small cells, reducing overall overhead while maintaining estimation accuracy for the specific use case.
Solution Approach 2:
The patent changes CRS parameters (antenna port count, frequency density, time density) based on the carrier type and small cell configuration. By dynamically adjusting these parameters rather than using fixed Rel-8 CRS configuration, the system achieves reliable channel estimation for small cells while significantly reducing reference signal overhead compared to the conventional approach of broadcasting CRS for the maximum number of ports.
2Stability of the object's composition
If common signals are transmitted in heterogeneous networks, then time and frequency synchronization are maintained, but spectral efficiency decreases
Solution Approach 1:
The patent extracts CRS transmission from the macro cell carriers and relocates it to small cell carriers with optimized parameters. By taking out the common signal transmission from the traditional macro cell context and implementing it selectively in small cells with reduced overhead configuration, the system maintains synchronization stability while improving overall spectral efficiency of the heterogeneous network.
Solution Approach 2:
The patent implements periodic CRS transmission with optimized time density specifically for small cell carriers. By using periodic action with adjusted parameters (reduced time density and frequency density) only where needed for synchronization in small cells, the system maintains synchronization stability while minimizing the impact on spectral efficiency compared to continuous common signal transmission across all carriers.
3Measurement precision
If CRS is transmitted with high density, then channel quality measurement accuracy is improved, but energy consumption increases
Solution Approach 1:
The patent applies local quality by configuring CRS with appropriate density only in small cell carriers where channel quality measurement is critical, rather than uniformly across all carriers. This localized approach maintains measurement precision for small cell RRM operations while reducing overall base station energy consumption by transmitting CRS with lower density elsewhere in the heterogeneous network.
Solution Approach 2:
The patent changes CRS transmission parameters (frequency density, time density, antenna port count) based on carrier type and measurement requirements. By dynamically adjusting these parameters rather than using fixed high-density configuration, the system achieves sufficient channel quality measurement accuracy for small cell RRM while significantly reducing base station energy consumption compared to conventional high-density CRS transmission.
Data Source
AI summary
Eliminating or reducing transmission of common signals for enhanced spectral efficiency, improved support for heterogeneous networks, network energy saving possibilities, can be obtained by apparatuses and methods according to certain embodiments. A method for operating a user equipment can include receiving a measurement object from a network for detection of one or more predetermined type cells. A cell search can be conducted. When a predetermined type cell is found, cell specific reference signal hopping parameters can be determined. Then, radio resource management measurement can be performed from the cell specific reference signal hopping parameters.