MU-MIMO Null Signal Direction for Interference Mitigation
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Solution Overview
Problem
In wireless communication systems using MU-MIMO, inaccurate channel information leads to interference and decreased communication quality due to incorrect transmission beam control, especially when multiple users share the same frequency band, causing packet retransmissions and increased error rates.
Innovation Solution
A wireless communication system that periodically assesses and adjusts transmission directivity to specific terminals, using interference estimation and null signal determination to optimize modulation schemes, coding rates, and spatial multiplexing orders based on measured interference, thereby mitigating the impact of channel estimation errors and inter-user interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spatial multiplexing is used to transmit signals to multiple terminals simultaneously, then spectral efficiency is improved, but interference between terminals occurs due to channel estimation errors
Solution Approach 1:
The patent applies preliminary anti-action by directing null signals to terminals that are not current transmission targets before interference occurs. The base station预先 identifies terminals that may receive interference and directs null signals to their directions, creating preemptive interference cancellation. This prevents inter-terminal interference before it degrades communication quality, while maintaining the spectral efficiency benefits of spatial multiplexing.
2Measurement precision
If transmission beam control is performed using channel information, then directivity to transmission destinations is improved, but accuracy of channel information deteriorates over time due to environment changes
Solution Approach 1:
The patent implements periodic action by repeatedly directing null signals at predetermined intervals to terminals that are not current transmission targets. This periodic null signal direction continuously updates and maintains accurate channel state information over time, compensating for environmental changes and mobility. The periodic refresh of channel information ensures beam control accuracy is maintained without requiring continuous channel estimation.
3Reliability
If null signals are directed to specific terminals to prevent interference, then communication quality for those terminals is improved, but system complexity increases due to periodic assessment and adjustment
Solution Approach 1:
The patent applies self-service by having non-transmission target terminals autonomously measure reception power levels and determine when null signal direction is needed. Terminals compare their received power against thresholds and autonomously trigger null signal direction requests to the base station. This distributes the control complexity from the base station to the terminals themselves, reducing overall system complexity while maintaining communication quality.
Data Source
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AI summary
Communication quality is prevented from being deteriorated due to interference caused by low accuracy of channel information or interference from another base station or another wireless communication system. A wireless communication system includes a first wireless station including a plurality of antenna elements, transmission units corresponding to the plurality of antenna elements, and a transmission directivity control unit that controls transmission directivity of the plurality of antenna elements, and a plurality of second wireless stations each including a reception power measurement unit that measures a reception power. The transmission directivity control unit determines the transmission directivity of each of the plurality of antenna elements so that a signal does not reach a particular second wireless station among the plurality of second wireless stations. The transmission units generate wireless signals using the transmission directivity. The plurality of antenna elements transmit the generated wireless signals. The reception power measurement unit measures the reception power in a period that is set so that a signal does not reach the particular second wireless station, and detect the presence or absence of interference.