Cyclic Prefix Reduction in mmWave MIMO Systems
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Solution Overview
Problem
In wireless mobile communication systems, the cyclic prefix duration needs to be reduced to accommodate increased control overhead associated with beamforming, especially in multiple transmission path environments where delay spread variations are significant, to maintain data rates and avoid inter-symbol interference.
Innovation Solution
Estimate delay spread variations for different transmit/receive beam pairs and employ beam switching reference signals to dynamically adjust cyclic prefix durations, using subframe configurations with predefined CP durations for each mobile station, and implement beam switching to accommodate high mobility and support single-user MIMO operations even when CP differences are large.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cyclic prefix duration is increased to eliminate inter-symbol interference in multiple transmission path environments, then reliability is improved, but productivity deteriorates due to decreased data rates
Solution Approach 1:
The patent implements dynamic cyclic prefix adjustment where the base station determines delay spread for different transmit/receive beam pairs and configures different CP durations accordingly. This allows the system to adapt CP length to actual channel conditions rather than using a fixed conservative value, thereby reducing overhead while maintaining ISI protection where needed.
Solution Approach 2:
The system changes the CP duration parameter based on measured delay spread characteristics of different beam pairs. By estimating delay spread using beam switching reference signals and configuring CP accordingly, the system optimizes the CP parameter to balance reliability and data rate requirements.
2Productivity
If cyclic prefix duration is reduced to increase data rates, then productivity is improved, but reliability deteriorates due to potential inter-symbol interference
Solution Approach 1:
The system dynamically adjusts CP duration based on actual delay spread measurements for each beam pair rather than using a fixed conservative value. This allows shorter CP to be used when delay spread is small, improving data rate while maintaining sufficient protection against ISI when needed.
Solution Approach 2:
Different CP durations are configured for different transmit/receive beam pairs based on their specific delay spread characteristics. This localized optimization allows each beam pair to use the minimum necessary CP length, improving overall system efficiency while maintaining reliability for each individual connection.
3Device complexity
If a single cyclic prefix duration is used for all beam pairs, then device complexity is reduced, but adaptability deteriorates due to inability to accommodate delay spread variations
Solution Approach 1:
The system implements dynamic CP configuration where the base station determines delay spread for different beam pairs and configures appropriate CP durations. This allows the system to adapt to varying delay spread conditions across different beam pairs while maintaining manageable complexity through automated measurement and configuration procedures.
Solution Approach 2:
The CP duration parameter is changed and optimized for each beam pair based on measured delay spread. This parameter adaptation enables the system to handle diverse propagation conditions and beam configurations without requiring overly complex manual configuration or fixed conservative settings.
4Adaptability or versatility
If beam switching is implemented to support high mobility and SU-MIMO, then adaptability is improved, but device complexity increases due to need for delay spread estimation and CP adjustment
Solution Approach 1:
The system performs preliminary delay spread estimation using beam switching reference signals before configuring CP durations for data transmission. This advance measurement and configuration approach simplifies the overall process by establishing appropriate CP settings before actual data transmission begins, reducing complexity during active communication.
Solution Approach 2:
The system uses feedback from delay spread measurements to automatically configure appropriate CP durations. The base station measures delay spread using beam switching reference signals, determines the appropriate CP configuration, and applies it accordingly. This closed-loop approach manages complexity through automated decision-making based on measured channel conditions.
Data Source
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AI summary
To reduce the duration of a cyclic prefix used for a multiple input, multiple output (MIMO) communications channel, delay spread variations for different transmit/receive beam pair combination is estimated and used for fast beam switching and to support single user MIMO (SU-MIMO) even when the CP difference between two beams is large. Beam switching reference signals are employed to estimate delay spread exceeding current CP, and to support beam switching. CP covering sub-clusters within clusters for the MIMO channel are exploited to reduce the CP requirement and improve efficiency. Any one of a number of different CP durations may be selected for each different mobile station, using one of a finite set of subframe configurations for which the CP durations of different symbol locations within the subframe are predefined. Dynamically switching subframe configurations by the system accommodates high mobility.