Sliding Radio Frame Configurations for Dynamic TDD Interference Control
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Solution Overview
Problem
Dynamic TDD systems in 5G NR face significant inter-cell cross-link interference (CLI) due to asymmetric traffic demands, leading to degraded UL and DL capacities, and existing coordination schemes incur high signaling overhead and complexity.
Innovation Solution
A sliding radio frame configuration (RFC) coordination scheme that allows BSs to autonomously select RFCs based on traffic demands, with limited signaling overhead, using a predefined codebook and a master BS to minimize CLI and maximize capacity by aligning RFCs with minimal misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If each BS independently changes its DL-to-UL subframe ratio according to its traffic ratio, then the adaptability to traffic demands is improved, but inter-cell cross-link interference increases
Solution Approach 1:
A master base station is introduced as an intermediary to coordinate radio frame configurations among multiple base stations. The master BS receives RFC requests from slave BSs, determines the optimal configuration considering cluster-wide traffic conditions, and signals the coordinated RFC to all slave BSs. This intermediary approach enables adaptive TDD operation while preventing CLI through centralized coordination.
Solution Approach 2:
Slave base stations provide feedback to the master base station regarding their traffic conditions and desired radio frame configurations. The master BS uses this feedback to make informed coordination decisions, adjusting the RFC of slave BSs to optimize overall cluster performance while minimizing inter-cell interference. This feedback mechanism enables adaptive operation without requiring full centralized control.
2Object-affected harmful factors
If coordination schemes among BSs are implemented to counteract CLI, then the harmful interference is reduced, but signaling overhead and implementation complexity increase
Solution Approach 1:
The coordination function is segmented into two parts: a master base station that performs centralized RFC determination, and slave base stations that execute the coordinated configurations. This segmentation allows complex coordination logic to be concentrated in one entity while keeping individual BS implementations simpler. The master BS handles the complexity of CLI mitigation by making centralized decisions, while slave BSs simply follow the assigned configurations.
Solution Approach 2:
The master base station acts as an intermediary that simplifies coordination by centralizing the decision-making process. Instead of requiring complex peer-to-peer coordination between all BS pairs, the master BS mediates all RFC adjustments, receiving traffic condition reports from slave BSs and issuing coordinated configuration commands. This intermediary approach reduces signaling overhead compared to distributed coordination schemes.
3Productivity
If DL-heavy BSs transmit with high power, then downlink capacity is improved, but UL transmissions of adjacent BSs are destroyed
Solution Approach 1:
The radio frame configuration is made dynamic and adaptable to changing traffic conditions. Base stations can adjust their DL-to-UL subframe ratios in response to instantaneous traffic demands, allowing DL-heavy BSs to allocate more downlink resources when needed while coordinating with neighboring BSs to prevent CLI. This dynamic adjustment enables high downlink capacity when required while mitigating interference to uplink transmissions through coordinated configuration changes.
Solution Approach 2:
Slave base stations monitor their traffic conditions and provide feedback to the master base station about their DL-to-UL traffic ratios and desired configurations. The master BS uses this feedback to coordinate RFC adjustments that allow DL-heavy BSs to operate at high capacity while preventing DL-to-UL interference to neighboring cells. The feedback loop enables adaptive power and resource allocation that responds to actual traffic conditions.
Data Source
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AI summary
Slave units of a mobile communication system each determine (S907), out of a predefined sliding codebook of Q unique radio frame configurations, a radio frame configuration for communicating with user equipments, and transmit (S907), to a master unit of a cluster which the slave units belong to, a request to use the determined radio frame configuration. The predefined sliding codebook comprises sub-codebooks each grouping together radio frame configurations of the Q unique radio frame configurations, that share the same downlink-to-uplink subframe ratio but with a phase offset of the radio frame configurations. The master unit identifies (S909) a common sub-codebook out of the sub-codebooks of the predefined sliding codebook, that comprises most of the determined radio frame configurations indicated in the requests received from the slave units, and, for each of the determined radio frame configurations, selects (S911, S915, S917, S921) a radio frame configuration out of the Q unique radio frame configurations, that corresponds to a sub- codebook of the determined radio frame configuration and minimizes an average misalignment with a radio frame configuration of the common sub-codebook.