mmWave Beam Training via Wide-to-Narrow Rotation
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Solution Overview
Problem
Millimeter wave (mmWave) communications systems face challenges with high path-loss and limited range due to high-frequency operations, and existing beam-forming techniques require extensive beam training, resulting in significant time overhead for initial attachment of user equipment (UE) in communications systems.
Innovation Solution
The system and method involve transmitting wide beam-formed reference signals and broadcast signals initially, followed by rotation of these signals by a narrow beam-width, allowing UE to detect the wide beam boundary and inform the mmWave eNB, which assigns a narrow beam direction, thereby reducing the time overhead for initial attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If beam-forming is used to increase the range of mmWave communications system, then the range is improved, but the time overhead for initial attachment increases due to extensive beam training
Solution Approach 1:
The beam training process is segmented into two distinct phases: wide beam training for initial attachment and narrow beam training for data transmission. This segmentation allows the system to use wide beams with larger coverage during initial attachment, reducing the time overhead, while narrow beams are used later for high-rate data transmission, thus resolving the contradiction between range improvement and time overhead reduction.
Solution Approach 2:
The system dynamically switches between wide beam and narrow beam modes based on the operational phase. During initial attachment, wide beams are used to cover larger areas and reduce training time. Once attached, the system transitions to narrow beams for efficient data transmission. This dynamic adaptation resolves the contradiction by optimizing beam characteristics for each specific phase of operation.
2Use of energy by moving object
If narrow beam beam-width is used for beam-forming, then the energy directionality is improved, but the time required for beam detection and initial attachment increases
Solution Approach 1:
The beam training process is divided into two stages: wide beam training for initial attachment where detection time is critical, and narrow beam training for data transmission where energy directionality is critical. This segmentation allows each stage to use the appropriate beam width optimized for its specific requirement, resolving the contradiction between energy directionality and detection time.
Solution Approach 2:
Wide beam training is performed as a preliminary action before narrow beam training. The wide beams establish initial attachment and identify rough beam directions first. Then, narrow beams are trained within the identified direction ranges. This preliminary action with wide beams reduces the overall time for beam detection while preserving the energy directionality benefits of narrow beams for subsequent data transmission.
3Loss of time
If wide beam beam-width is used for initial attachment, then the time overhead is reduced, but the energy directionality and transmission efficiency decrease
Solution Approach 1:
The system segments the beam training process into wide beam phase for initial attachment and narrow beam phase for data transmission. During initial attachment, wide beams are used to reduce time overhead and enable quick connection establishment. After attachment, narrow beams are employed to provide the necessary energy directionality and transmission efficiency. This temporal segmentation resolves the contradiction by using each beam type in the phase where it provides the greatest benefit.
Solution Approach 2:
The beam width is dynamically adjusted based on the operational phase: wide beams during initial attachment to minimize time overhead, and narrow beams during data transmission to maximize energy directionality. This dynamic switching resolves the contradiction by optimizing the beam characteristics for the specific operational requirements of each phase.
Data Source
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Figure 3~4B
AI summary
A method for operating a user equipment (UE) in a millimeter wave (mmWave) communications system includes receiving a first wide beam beam-formed reference signal from a mmWave evolved NodeB (eNB) during an initial time interval, the first wide beam beam-formed reference signal carrying timing information, detecting a wide beam boundary between the first wide beam beam-formed reference signal and a second wide beam beam-formed reference signal during a subsequent time interval, wherein both the first wide beam beam-formed reference signal and the second wide beam beam-formed reference signal are rotated by a narrow beam beam-width during each intermediate time interval between the initial time interval and the subsequent time interval, and informing the mmWave eNB of an indication that the UE detected the wide beam boundary during the subsequent time interval, the indication being used to assign a narrow beam direction to the UE.