Multi-User MIMO Power Scaling Interference Cancellation
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Solution Overview
Problem
In multi-user MIMO systems, power scaling leads to increased interference between users, reducing the transmission rate for user equipment near the base station.
Innovation Solution
A wireless communication apparatus and method that calculates and feeds back the reception quality of signals when interference signals are canceled, allowing for the use of high-level modulation systems and optimizing transmission parameters based on this feedback to improve transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power scaling is applied to ensure signal strength for cell edge users, then reception quality for cell edge users is improved, but interference signal level for users near the base station increases
Solution Approach 1:
The receiving device calculates reception quality under the assumption that interference signals are canceled, and feeds back this information to the transmitting device. This feedback enables the transmitting device to optimize power distribution and modulation schemes based on actual reception conditions, resolving the contradiction between ensuring signal strength for cell edge users and minimizing interference for near users.
Solution Approach 2:
The invention changes the parameter used for reception quality assessment from actual received signal quality to hypothetical quality after interference cancellation. This parameter change allows the system to evaluate and optimize transmission parameters based on the assumption that interference will be removed, enabling higher modulation schemes even when interference signals are present.
2Productivity
If high-level modulation systems are used to improve transmission rate, then transmission efficiency is improved, but reception quality deteriorates in the presence of interference signals
Solution Approach 1:
The receiving device performs preliminary calculation of reception quality assuming interference cancellation before actual reception. This preliminary assessment allows the system to select appropriate modulation schemes that would be viable after interference removal, enabling higher transmission rates without compromising actual reception quality.
Solution Approach 2:
By feeding back hypothetical reception quality information to the transmitting device, the system can make informed decisions about modulation scheme selection. This feedback mechanism enables the use of high-level modulation systems by providing the transmitting device with knowledge of post-cancellation reception quality, thus improving transmission efficiency without sacrificing reliability.
3Reliability
If power is allocated to cell edge users to improve their reception, then transmission reliability for cell edge users is improved, but transmission rate for users near base station is reduced
Solution Approach 1:
The invention changes the evaluation parameter from actual received signal quality to hypothetical quality after interference cancellation. This allows the system to allocate power to cell edge users while maintaining high transmission rates for near users, because the near users' reception quality is evaluated based on the assumption that interference will be canceled, not based on actual interference levels.
Solution Approach 2:
The system performs preliminary assessment of reception quality under interference cancellation assumptions before finalizing transmission parameters. This preliminary action enables optimized power distribution that considers both cell edge user reliability requirements and near user transmission rate requirements, resolving the contradiction between the two objectives.
Data Source
AI summary
When power scaling is applied to multi-user MIMO, a reduction in transmission rate is suppressed and transmission efficiency is improved. When signals are transmitted through spatial multiplexing from a wireless base station 11 to a plurality of pieces of user equipment 12 and 13, notification of a transmission parameter (MCS) of the distant user equipment (UE-B) 13 is provided as control information to the adjacent user equipment (UE-A) 12. The user equipment 12 calculates, based on the received control information, a reception quality (CQI) after cancellation of a signal serving as an interference signal and destined for the other user equipment 13, and feeds back the calculated result to the wireless base station 11. Based on this feedback, the wireless base station 11 sets a transmission parameter (MCS) of each piece of the user equipment 12 and 13 using the CQI after the cancellation, and transmits signals intended for respective users through spatial multiplexing after performing power distribution between the users by power scaling.