Beam Tracking in FD-MIMO Systems
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Solution Overview
Problem
In FD-MIMO systems, the increased beam gain due to precoding results in a narrowed beam width, leading to increased beam tracking errors and potential coverage holes, especially as the number of antennas increases to several hundreds or tens of thousands, posing a challenge for effective beam tracking in future mobile communication technologies like 5G.
Innovation Solution
The base station transmits a beam stream including a primary beam for data transmission and secondary beams with precoded reference signals in the vicinity of the primary beam, allowing user equipment to select suitable beam indexes for feedback, enabling effective beam tracking by limiting beam candidates to the vicinity of the current beam, thereby reducing overhead and maintaining coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If precoding is applied to increase beam gain, then beam gain is improved, but beam width is narrowed
Solution Approach 1:
The patent segments the beam transmission by sending multiple beams (first beam for data, second beams as candidates) instead of relying on a single narrow beam. This segmentation allows the system to maintain high gain through precoding while providing multiple coverage directions to prevent coverage holes caused by beam narrowing.
Solution Approach 2:
The base station performs preliminary action by transmitting second beams (beam candidates) in advance in directions toward the vicinity of the first beam before data transmission. The user equipment measures these candidate beams and feeds back beam indexes, enabling the base station to pre-adjust the beam direction to track user movement, thus compensating for the narrow beam width effect.
2Power
If beam width is narrowed to increase beam gain, then beam gain is improved, but beam tracking error increases
Solution Approach 1:
The patent implements feedback mechanism where user equipment measures the reference signals in second beams, selects suitable beam indexes, and feeds them back to the base station. The base station uses this feedback to adjust and track the beam direction, compensating for the narrow beam width and reducing beam tracking errors through continuous feedback loops.
Solution Approach 2:
The base station transmits beam candidates in advance in directions toward the vicinity of the current beam, allowing the user equipment to measure and report the best beam direction before data transmission. This preliminary action enables proactive beam tracking adjustment, reducing tracking errors that would otherwise occur with narrow beams.
3Power
If number of antennas is increased to several hundreds or tens of thousands, then beam gain is improved, but beam tracking difficulty increases
Solution Approach 1:
The patent manages the complexity of large-scale MIMO by segmenting the beam transmission into a first beam for data and multiple second beams as candidates. This segmentation simplifies the tracking process by providing a structured approach to beam management, making it more manageable despite the large number of antennas.
Solution Approach 2:
The base station performs preliminary beam direction adjustment by transmitting candidate beams in advance and using user equipment feedback to determine the optimal beam direction before data transmission. This preliminary action simplifies the overall beam tracking process for large-scale MIMO systems by establishing a systematic method to handle the complexity of tracking numerous antennas.
Data Source
AI summary
In a mobile communication system including a base station provided with a plurality of antenna ports, and user equipment that executes radio communication with the base station, the base station transmits a beam stream including a first beam for transmitting data to the user equipment, and one or more second beams for transmitting a precoded reference signal in a direction toward a vicinity of the first beam; and upon receiving the beam stream, the user equipment selects, from the first beam and the second beam, and transmits, to the base station, one or more suitable beam indexes.