Hybrid Beamforming CSI Feedback via BFRS Resource Allocation
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Solution Overview
Problem
Current wireless communication systems face capacity limitations in high-frequency bands due to increased interference and traffic load, particularly in millimeter wave (mmWave) bands, where stringent link budgets and reduced antenna size necessitate innovative solutions for effective channel state information (CSI) feedback.
Innovation Solution
The implementation of hybrid antenna beamforming systems that utilize beamforming reference signals (BFRS) with resource blocks containing time-frequency resources, allowing for the determination and transmission of analog transmit beams and grouping information from a network controller to user equipment (UE), enabling effective multiple-input and multiple-output (MIMO) channel formation and CSI feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If hybrid antenna architecture is used to reduce hardware complexity and power consumption, then device complexity and energy use are reduced, but measurement precision of channel state information deteriorates due to limited RF chains
Solution Approach 1:
The patent segments the beamforming process into two independent stages: analog beamforming for spatial direction and digital beamforming for MIMO processing. This segmentation allows the system to use fewer RF chains while maintaining measurement precision by separating the functions that were previously coupled
Solution Approach 2:
The patent introduces beamforming reference signals (BFRS) as an intermediary mechanism that enables accurate channel measurement despite limited RF chains. The BFRS provides a structured reference for measuring channel quality across different spatial directions, compensating for the reduced number of simultaneous measurements possible with fewer RF chains
2Reliability
If analog beamforming is used to compensate for mmWave path loss, then link budget is improved, but device complexity increases due to additional phase shifters and beamforming hardware
Solution Approach 1:
The patent merges the analog and digital beamforming functionalities into a unified hybrid beamforming architecture. By combining the spatial filtering capability of analog beamforming with the signal processing capability of digital beamforming, the system achieves improved link budget while managing hardware complexity through shared RF chains
Solution Approach 2:
The patent makes the RF chains multi-functional by allowing them to perform both analog beamforming operations and digital MIMO processing. This universality reduces the total number of RF chains needed compared to having separate dedicated hardware for each function, thereby managing complexity while maintaining link budget performance
3Reliability
If larger number of antenna arrays are deployed at mmWave frequencies, then link budget is improved through beamforming, but manufacturing precision requirements increase due to smaller antenna elements
Solution Approach 1:
The patent segments the large antenna array into multiple sub-arrays, each handled by a separate RF chain. This segmentation reduces the manufacturing precision requirements for individual antenna elements while maintaining the overall beamforming capability needed for mmWave link budget compensation
Solution Approach 2:
The patent changes the operational parameters of the antenna system by using beamforming to electronically steer and focus signals. This parameter change allows the system to achieve the required link budget through signal processing rather than relying solely on precise physical antenna element placement and characteristics
4Measurement precision
If beamforming reference signals are transmitted for each analog beam, then measurement precision is improved, but loss of time increases due to sequential transmission requirements
Solution Approach 1:
The patent segments the channel measurement process into multiple independent measurements, one for each analog beam. This segmentation allows the system to perform precise measurements for each spatial direction separately, improving overall measurement precision while managing the time required through efficient resource allocation
Solution Approach 2:
The patent implements periodic transmission of beamforming reference signals in a structured sequence. This periodic action allows the system to efficiently cycle through different analog beams and their corresponding BFRS transmissions, maintaining measurement precision while minimizing the total time required for complete channel state assessment
Data Source
AI summary
Various methods and systems are provided to provide for Channel State Information (CSI) feedback of hybrid beamforming. In a first example embodiment, a method for signaling a beamforming reference signal (BFRS) is provided. A resource block is created for the BFRS, the resource block containing a plurality of resource elements, each resource element defined by a time-frequency resource within one subcarrier and one multiplexing symbol. A total number of analog transmit beams for the BFRS is then determined, along with grouping information for the analog transmit beams for the BFRS. Then, the resource block, the total number of analog beams, and the grouping information are transmitted from a first network controller to a user equipment (UE). Then the BFRS is transmitted from the first network controller to the UE.