MIMO Feedback Scheduling to Reduce Precoder Rates
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Solution Overview
Problem
Conventional closed-loop MIMO systems face challenges in efficiently scheduling feedback from multiple receivers, leading to uplink bottlenecks and increased feedback delay, which degrades link performance and requires a more efficient method to reduce precoder feedback rate.
Innovation Solution
A feedback control system with a scheduling module at the base station that determines and broadcasts feedback control criteria to receivers, allowing them to constrain and schedule precoder feedback, using either a round-robin or metric-based scheduler to reduce the total feedback rate and delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all receivers continuously transmit precoder feedback in conventional closed-loop MIMO systems, then the transmitter obtains complete channel information for optimal precoding, but the uplink feedback rate increases linearly with the number of users causing uplink bottlenecks
Solution Approach 1:
The patent implements periodic feedback transmission where receivers transmit precoder feedback only at scheduled time instances rather than continuously. The base station generates feedback indicators that trigger periodic feedback opportunities, reducing the feedback rate while maintaining adequate channel information for precoding operations.
Solution Approach 2:
The base station preliminarily determines which receivers should transmit feedback and when, by generating feedback indicators based on current channel conditions and scheduling requirements. This preliminary action prevents unnecessary feedback transmissions and optimizes the timing of feedback opportunities.
2Measurement precision
If receivers transmit precoder feedback with high frequency, then the transmitter has up-to-date channel information for accurate precoding, but the feedback delay increases degrading system performance
Solution Approach 1:
The feedback scheduling is dynamic rather than static. The base station adapts the feedback timing and frequency for each receiver based on current channel conditions, quality metrics, and scheduling requirements. This dynamic approach optimizes the balance between information freshness and feedback delay.
Solution Approach 2:
The system changes the feedback parameter (timing and frequency) based on channel conditions and system state. Feedback indicators convey parameter information that adjusts when and how receivers transmit feedback, allowing the system to adapt to varying channel dynamics and optimize performance.
3Quantity of substance
If the system uses codebook-based precoding to reduce feedback overhead, then the feedback rate decreases, but the precision of channel representation is limited by codebook quantization
Solution Approach 1:
The patent introduces feedback indicators as an intermediary mechanism between the receiver and transmitter. These indicators do not directly convey quantized channel information but rather control when and how feedback is transmitted, allowing the system to manage feedback rate independently of the precision requirements.
Data Source
AI summary
In a closed-loop wireless communication system, a codebook-based feedback control mechanism is provided where feedback from each of a plurality of receivers is scheduled to control the feedback so that the receiving devices do not needlessly feed back precoding information to the transmitting device. The feedback may be controlled by establishing and distributing a schedule to control when each receiver feeds back precoding information, or by establishing and distributing a metric-based feedback threshold that must be satisfied before feedback is permitted.