Massive MIMO Base Station Beamforming Weight Control
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Solution Overview
Problem
In massive-MIMO systems operating in high frequency bands, user terminals far from radio base stations struggle to receive reference signals adequately, hindering channel estimation and beamforming, which leads to difficulties in transmitting data signals effectively.
Innovation Solution
The implementation of a method where fixed weights are applied to channel estimation reference signals and data signals, considering the receiving conditions of user terminals, allows for adequate beamforming even when reference signals are not received, by using synchronization signals with varying weights and determining data transmission methods based on user terminal feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If beamforming is applied to transmit data signals in massive-MIMO systems, then spectral efficiency and data rates are improved, but user terminals far from base stations cannot receive reference signals adequately, causing channel estimation failures
Solution Approach 1:
The patent segments reference signals into two types: first reference signals transmitted without beamforming for channel estimation, and second reference signals transmitted with beamforming for data signal reception. This segmentation allows terminals to obtain channel state information from the first reference signals while benefiting from beamforming on second reference signals, resolving the contradiction between spectral efficiency and channel estimation reliability.
Solution Approach 2:
The first reference signals act as an intermediary mechanism that enables channel estimation for distant terminals without requiring beamforming. These reference signals serve as a mediator between the base station and distant terminals, providing the necessary channel state information for subsequent beamformed data transmission.
2Productivity
If a large number of antenna elements are used in massive-MIMO, then multiplexing efficiency and beamforming reliability are improved, but propagation loss in high frequency bands increases, reducing coverage area
Solution Approach 1:
The patent dynamically adjusts the transmission method based on terminal location and receiving conditions. For distant terminals, the system uses first reference signals without beamforming to ensure coverage, while for nearby terminals with good receiving conditions, it employs second reference signals with beamforming to maximize spectral efficiency. This dynamic adaptation resolves the contradiction between multiplexing efficiency and coverage area.
3Measurement precision
If conventional channel estimation methods using reference signals without beamforming are used, then channel state information can be obtained, but data signals cannot be transmitted effectively to distant terminals due to insufficient reference signal reception
Solution Approach 1:
The patent segments reference signals into two functional groups: first reference signals dedicated to channel estimation (transmitted without beamforming) and second reference signals dedicated to data signal reception (transmitted with beamforming). This segmentation allows distant terminals to accurately estimate channel state information from first reference signals while still enabling effective data transmission using beamformed second reference signals.
Solution Approach 2:
The patent applies different transmission characteristics to different reference signals based on their local function. First reference signals use no beamforming to maximize reception quality for channel estimation, while second reference signals use beamforming to maximize data transmission effectiveness. This local quality differentiation resolves the contradiction between measurement precision and productivity.
Data Source
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AI summary
The present invention is designed so that, in a communication system to employ massive MIMO, data signals to which beamforming is applied can be transmitted adequately. A radio base station transmits a data signal to a user terminal by applying beamforming using a plurality of antenna elements, and has a determining section that determines the type of a weight to apply to the data signal for beamforming, a generating section that generates a reference signal which the user terminal uses in channel estimation, a weight control section that controls weights to apply to transmitting signals, and a transmitting section that transmits the data signal and the reference signal, and the weight control section determines whether or not to apply a weight to the reference signal based on the type of the weight.