Mobile Station Synchronization Signal Beamforming for Massive-MIMO
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Solution Overview
Problem
In LTE-Advanced and subsequent mobile communication systems employing massive-MIMO, the cell search process is hindered due to the inability to adequately transmit synchronization signals over long distances, especially when the massive-MIMO base station lacks identification information, leading to suboptimal communication system performance.
Innovation Solution
A synchronization method where the mobile station apparatus generates and transmits synchronization signals with controlled beamforming, changing beamforming weights at predetermined intervals to ensure the signals reach distant massive-MIMO base stations, and include identification information to enable accurate cell search and connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the massive-MIMO base station transmits synchronization signals using conventional methods, then the signal can be transmitted, but the signal cannot reach distant mobile stations adequately due to lack of beamforming control
Solution Approach 1:
Instead of the base station transmitting synchronization signals in all directions, the mobile station actively transmits synchronization signals toward the base station using beamforming. This inversion of the traditional synchronization signal transmission direction enables reliable synchronization establishment even when the base station lacks identification information.
Solution Approach 2:
The mobile station changes beamforming parameters (beam direction, beam width, gain) to optimize synchronization signal transmission. By adjusting these parameters, the mobile station can direct signals accurately toward the base station and achieve reliable synchronization over long distances.
2Device complexity
If the base station lacks identification information, then the system structure is simplified, but the mobile station cannot perform accurate cell search and specification
Solution Approach 1:
The mobile station acts as an intermediary by generating and transmitting synchronization signals that include beamforming information. This intermediary approach allows the mobile station to convey identification and synchronization information to the base station without requiring the base station to have pre-configured identification information.
Solution Approach 2:
The mobile station performs preliminary beamforming operations and transmits synchronization signals before formal connection establishment. This preliminary action enables the base station to acquire necessary information for subsequent communication setup even without pre-stored identification data.
3Measurement precision
If beamforming weights are changed frequently, then signal accuracy to specific directions is improved, but transmission time and processing overhead increase
Solution Approach 1:
The mobile station changes beamforming weights periodically at predetermined intervals rather than continuously. This periodic adjustment maintains adequate beam direction accuracy for synchronization purposes while minimizing unnecessary processing overhead and time consumption.
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
The present invention is designed to allow a communication system employing massive-MIMO to optimize its performance. A mobile station apparatus transmits a synchronization signal by controlling the transmission direction of the transmitting beam for the synchronization signal by means of beamforming using a plurality of antenna elements, and has a synchronization signal processing section (62) that generates the synchronization signal including identification information of the mobile station apparatus, and changes the beamforming weight for the synchronization signal at predetermined time intervals, and a transmitting section (63) that transmits the synchronization signals generated in accordance with each beamforming weight on the uplink.