Switched Beam Selection Using Downlink Pilot Signals
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Solution Overview
Problem
Conventional switched beamforming methods require continuous uplink signals for estimating the direction of arrival (DOA), leading to resource wastage and increased load at the base station, and errors due to frequency differences between uplink and downlink frequency bands.
Innovation Solution
A system and method that utilize a common downlink pilot signal to estimate channels for multiple antennas, calculate signal-to-noise ratios (SNR) using predetermined weight value vectors, and select the switched beam with the maximum SNR, reducing the need for uplink resource allocation and minimizing frequency band errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sequential uplink signals are used to estimate DOA at the base station, then beam direction can be determined, but resource wastage increases and base station load increases
Solution Approach 1:
The patent inverts the traditional approach by having the mobile terminal (instead of the base station) perform DOA estimation and switched beam selection. The mobile terminal estimates the channel based on downlink pilot signals, calculates SNR for different beam directions, and feeds back the selected beam index to the base station. This inversion transfers the computational burden from the base station to the mobile terminal, resolving the contradiction between measurement precision and resource efficiency.
Solution Approach 2:
The mobile terminal performs self-service by autonomously estimating the channel, calculating SNR for multiple beam directions using predetermined weight vectors, and selecting the optimal beam without requiring continuous base station intervention. The terminal only feeds back the beam selection result, enabling the base station to apply the selected beam for data transmission without bearing the computational load of DOA estimation.
2Reliability
If continuous uplink signals are transmitted for DOA estimation, then beam selection accuracy is maintained, but uplink resources are continuously consumed
Solution Approach 1:
The system uses periodic downlink pilot signals transmitted by the base station, which the mobile terminal uses to perform channel estimation and beam selection. Instead of requiring continuous uplink signals, the periodic pilot signals enable the mobile terminal to periodically update beam selection based on current channel conditions, maintaining reliability while significantly reducing uplink resource consumption.
Solution Approach 2:
The base station pre-configures and transmits pilot signals that enable the mobile terminal to perform channel estimation and beam selection in advance. The predetermined weight value vectors are also prepared in advance, allowing the mobile terminal to calculate SNR for different beam directions without requiring real-time base station computation, thus reducing ongoing resource consumption.
3Measurement precision
If uplink frequency band is used for DOA estimation in FDD system, then downlink beam can be selected, but frequency difference causes estimation errors
Solution Approach 1:
The downlink pilot signal serves multiple functions: it enables channel estimation, facilitates SNR calculation for beam selection, and provides a common reference for both base station and mobile terminal. By using the same downlink frequency for these purposes, the system eliminates frequency offset errors that would occur with uplink-based estimation in FDD systems, while maintaining beam selection accuracy.
Data Source
AI summary
The present invention relates to a system for selecting a switched beam for supplying a maximum received power to a subscriber station, and a method thereof. The number of switched beams used by a base station is limited, and a weight value vector for forming the switched beam is predefined. The subscriber station uses a pilot signal for discerning transmitting antennas to estimate channel values for the respective transmitting antennas, and uses the channel values and the predefined weight value vectors to determine a switched beam for supplying a maximum signal-to-noise ratio (SNR). The subscriber station notifies the base station of an identifier of a selected beam by using a feedback channel, and the base station uses the switched beam to transmit traffic data.