Multiuser MIMO Retransmission Interference Cancellation
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Solution Overview
Problem
In multi-user MIMO systems, interference from other users can lead to errors in data stream reception, resulting in increased retransmission operations and decreased overall system throughput due to insufficient suppression of interference signals.
Innovation Solution
A radio communication system with a retransmission controller and communication resource setting section that adjusts resource distribution based on receiving statuses, using interference signal demodulation, buffering, and elimination to enhance SINR and reduce retransmissions by prioritizing communication resources for receiving stations that successfully demodulate interference signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiuser MIMO allocates spatial resources to multiple users simultaneously, then sector throughput is enhanced through multi-user diversity gain, but user equipment experiences interference from other users' signals
Solution Approach 1:
The patent converts the harmful interference signal from other users into a beneficial resource by having the receiving station demodulate and buffer the interference signal, then use it for interference cancellation during retransmission. This transforms the harmful factor (interference) into a useful tool for improving reception quality and reducing retransmissions.
Solution Approach 2:
The receiving station performs preliminary demodulation and buffering of the interference signal before the retransmission occurs. By preparing the interference signal in advance and storing it in a buffer, the system is ready to cancel the interference when the retransmitted signal arrives, improving the effectiveness of interference suppression.
2Reliability
If retransmission is performed in multiuser MIMO with independent control per user, then successful reception probability is enhanced through soft combining, but the number of retransmission operations increases due to insufficient interference suppression
Solution Approach 1:
The patent uses the interference signal, which was previously harmful and caused reception failures requiring retransmission, as a beneficial resource for interference cancellation. By demodulating and buffering the interference signal and subtracting it from the received signal during retransmission, the system reduces the number of retransmissions needed while maintaining high successful reception probability.
Solution Approach 2:
The system implements feedback by having the receiving station detect reception status and send ACK/NACK signals to the base station. This feedback mechanism allows the base station to determine when retransmission is necessary, while the receiving station uses the buffered interference signal to improve the reception of retransmitted data through interference cancellation.
3Ease of operation
If communication resources are allocated equally to all users during retransmission, then fairness is maintained, but receiving SINR is insufficient for users experiencing interference
Solution Approach 1:
The patent applies local quality by allowing each receiving station to independently process and buffer the interference signal specific to its location and reception conditions. Each station performs interference cancellation locally using its own buffered interference signal, tailored to its specific interference environment, rather than applying a uniform resource allocation approach.
Data Source
AI summary
In a multiuser MIMO system, entire system throughput achieved during retransmission is significantly enhanced. When an interference signal addressed to another user equipment (UE2) 200b has been demodulated successfully, a user equipment (UE1) 200a holds the demodulated data pertaining to the interference signal, and feeds back ACK information about the UE2 and CQI information achieved after elimination of the interference signal to a radio base station (BS) 100. When the UE2 performs retransmission after ended in a receiving failure and when the UE1 has demodulated the interference signal addressed to the UE2 successfully, the BS changes the distribution of communication resources in such a way that communication resources for the UE2 become larger than those for the UE1. At the time of retransmission, the UE1 eliminates the interference signal from a newly-received signal by use of previously-held demodulated data pertaining to the interference signal, and the UE2 combines data pertaining to the desired signal held during previous receiving failure with data pertaining to the retransmitted signal by means of soft combining.