mmWave Beam Selection Using Frequency Multiplexing
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Solution Overview
Problem
Current cellular communication systems face capacity limitations due to interference and traffic loads, particularly in macro cellular deployments, and high-frequency bands are needed to mitigate these issues, but existing beamforming techniques are inefficient in finding optimal beam pairs for initial access in mmWave communications.
Innovation Solution
A method and system for beam selection using multiple mmWave subcarrier frequencies, where a communications controller sends frequency-multiplexed beams to a user equipment (UE) to cover a wide receive angle range, allowing the UE to select the best transmit-receive beam pair based on receive metric values, and iteratively refine the beam selection using hybrid precoding techniques to improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional beamforming techniques are used for initial access in mmWave communications, then the system can establish connectivity, but the search complexity is high and the access time is long
Solution Approach 1:
The patent segments the beam search process into two distinct stages: coarse beam search and fine beam search. The coarse stage uses wide beams to quickly identify promising directions, while the fine stage uses narrow beams to precisely determine the optimal beam pair. This segmentation reduces overall search complexity and access time compared to traditional exhaustive search methods.
Solution Approach 2:
The patent performs preliminary action by conducting the coarse beam search first to identify candidate directions before performing the more resource-intensive fine beam search. This preliminary identification of promising beam directions allows the system to focus subsequent resources on a reduced search space, improving overall efficiency.
2Productivity
If frequency multiplexing is used to transmit multiple beams simultaneously, then the initial access efficiency is improved, but the hardware requirements and CSI feedback increase
Solution Approach 1:
The patent segments the frequency resources to be assigned to different beams, with each beam occupying a specific frequency subset. This segmentation allows the UE to measure and report CSI for individual beams independently, reducing the overall feedback overhead while maintaining the ability to perform parallel beam searches through frequency multiplexing.
Solution Approach 2:
The patent implements partial frequency multiplexing where not all beams are transmitted simultaneously on all frequencies. Instead, beams are selectively activated and frequency-assigned based on the coarse search results, reducing the hardware burden and feedback requirements while maintaining search efficiency.
Data Source
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AI summary
A method for operating a UE includes receiving, by the UE during an initial access sequence, a plurality of first inbound beams each transmitted by a communications controller in a different transmit direction over a first carrier, where the first inbound beams have a different subcarrier frequency range from each other, generating values of a receive metric in accordance with the first inbound beams, selecting one of the first inbound beams in accordance with the receive metric values, transmitting, by the UE, an indication of the selected first inbound beam, and receiving, by the UE, a second inbound beam transmitted by the communications controller in a transmit direction in accordance with the indication of the selected first inbound beam, where the second inbound beam has a second subcarrier frequency range of the first carrier that is different than a first subcarrier frequency range of the selected first inbound beam.