Dynamic Open-Loop to Closed-Loop Switching in Multi-Stream Transmission
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Solution Overview
Problem
Existing closed-loop transmission schemes in LTE face challenges with increased bandwidth and number of layers, leading to questionable gain in relation to overhead, limited performance in small transmission bursts due to energy consumption, and difficulties in balancing downlink and uplink capacity.
Innovation Solution
A method and apparatus that enable switching from open-loop to closed-loop multi-stream transmission techniques during a transmission burst, using detailed channel state information to optimize pre-coding and reduce energy consumption by discontinuing CSI-RS transmission when not necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If closed-loop spatial multiplexing is used with increased bandwidth and number of layers, then transmission capacity is improved, but the gain in relation to overhead becomes questionable
Solution Approach 1:
The patent applies dynamic switching between open-loop and closed-loop transmission modes based on real-time channel conditions and transmission burst characteristics. The eNB decides whether to request PMI reports dynamically, transitioning from static closed-loop operation to adaptive hybrid operation, thereby optimizing the balance between transmission capacity and signaling overhead.
Solution Approach 2:
The patent changes the operational parameters of the transmission system by introducing conditional PMI reporting based on transmission burst size thresholds. When bursts are small, PMI reporting is suspended; when bursts are large enough, PMI reporting is activated. This parameter change adapts the system to achieve full rank transmission benefits without excessive overhead.
2Reliability
If detailed CSI feedback is requested from UE, then transmission performance is improved, but UE battery consumption increases
Solution Approach 1:
The patent implements partial CSI feedback operation by requesting PMI reports only when transmission bursts exceed a certain size threshold. Instead of continuously requesting detailed CSI feedback, the system applies partial feedback action selectively, reducing UE battery consumption while maintaining transmission performance when it matters most.
Solution Approach 2:
The patent introduces conditional feedback mechanisms where the eNB monitors transmission burst characteristics and dynamically decides whether to request PMI reports. This feedback loop allows the system to adapt to traffic patterns, requesting detailed CSI feedback only when transmission bursts are sufficiently large to justify the energy expenditure.
3Reliability
If CSI estimation and feedback are performed for small transmission bursts, then performance gain is limited, but UE battery drains and CSI reference symbols consume energy
Solution Approach 1:
The patent applies partial action by suspending PMI reporting for small transmission bursts where the performance gain would be limited. The system selectively activates CSI feedback only when transmission bursts are large enough to provide meaningful performance improvement, thereby avoiding wasteful energy consumption on small bursts.
Solution Approach 2:
The patent changes the operational parameter of PMI reporting activation based on transmission burst size. By introducing a threshold parameter, the system transitions from always-requesting CSI feedback to conditionally requesting it only when burst size justifies the energy investment, optimizing the performance-to-energy-ratio.
4Measurement precision
If eNB waits for PMI report before transmission, then pre-coding accuracy is improved, but packet delay increases
Solution Approach 1:
The patent applies preliminary action by having the UE prepare and buffer PMI reports in advance before they are actually needed for transmission. The UE continues to estimate channel state and generate PMI reports even during small transmission bursts, so that when a large burst occurs, the pre-computed PMI reports are already available, eliminating waiting time and reducing packet delay while maintaining pre-coding accuracy.
Data Source
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Figure 2
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AI summary
The present invention relates to a method and apparatus for multi-stream wireless communication between a transmitter node and a receiver node. The method comprises applying an open-loop multi-stream transmission technique during an initial part of a transmission burst. In another step of the method, detailed channel state information is received (54). The detailed channel state information indicates transmission pre-coding to be used during the transmission burst when applying a closed-loop multi-stream transmission technique. The method further includes switching (55) from the open-loop multi-stream transmission technique to the closed-loop multi-stream transmission technique during the transmission burst, in response to receiving the detailed channel state information. The method is applicable to both uplink and downlink transmission bursts.