MU-MIMO Scheduling With Selective CSI Feedback
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Solution Overview
Problem
In multi-user MIMO communication systems, determining an optimal user set for beamforming and transmission power allocation is challenging, and existing user scheduling algorithms face inefficiencies due to incomplete channel state information (CSI) and high CSI feedback overhead, which restricts performance.
Innovation Solution
A scheduling method that actively exchanges CSI by transmitting a channel state information request signal, calculating effective channel gains, and determining the order of CSI transmission among user equipment to optimize scheduling while minimizing overhead, using techniques like zero-forcing beamforming and projection matrices to enhance data transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If CSI compression technique is used to reduce the amount of CSI, then the overhead in MAC layer is reduced, but the performance of user scheduling is largely restricted
Solution Approach 1:
The patent applies partial action by requesting CSI only from a subset of user equipment rather than all users. The base station selectively requests CSI based on scheduling decisions, obtaining only the necessary CSI information needed for optimal scheduling while avoiding excessive overhead. This resolves the contradiction by balancing the need for sufficient scheduling information with the need to minimize feedback overhead.
2Productivity
If brute-force search is used for user scheduling, then optimal scheduling is achieved, but high complexity is required
Solution Approach 1:
The patent employs feedback mechanisms where user equipment responds to CSI request signals by providing requested channel state information. This interactive feedback approach enables the base station to obtain necessary scheduling information efficiently without requiring complex exhaustive searches. The feedback loop allows for optimized scheduling decisions based on actual channel conditions while maintaining lower computational complexity.
3Measurement precision
If CSI is requested from all user equipment, then complete scheduling information is obtained, but excessive overhead is generated
Solution Approach 1:
The patent applies local quality by requesting CSI only from specific user equipment that are candidates for scheduling rather than from all users. The base station makes localized decisions about which users to request CSI from based on current scheduling needs and channel conditions, obtaining precise information only where necessary for optimal scheduling while minimizing overall feedback overhead.
Data Source
AI summary
Provided is a scheduling method of a multi-user multi-input multi-output (MIMO) communication system. The scheduling method includes transmitting a channel state information request signal to a user equipment when data to be transmitted to the user equipment is received, and calculating, by the user equipment receiving the channel state information request signal, an effective channel gain of the user equipment, determining whether channel state information (CSI) is capable of being transmitted, and transmitting the CSI of the user equipment according to a result of the determining. Also, the scheduling method includes determining whether the CSI is received from the user equipment within a predetermined standby time, and when the CSI is received within the predetermined standby time, performing scheduling of the user equipment which has transmitted the CSI, determining whether a degree of freedom remains, and transmitting the channel state information request signal to another user equipment, from which CSI is not received, when the degree of freedom remains.