WTRU Delay Spread Measurement for Dynamic Cyclic Prefix Selection
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Solution Overview
Problem
Existing wireless communication systems face challenges in selecting appropriate cyclic prefix (CP) sizes to mitigate inter-symbol interference (ISI) due to varying delay spreads, leading to inefficient system overhead and potential signal decoding issues, especially in environments with reconfigurable intelligent surfaces (RIS) that introduce complex propagation paths.
Innovation Solution
Implement AI/ML operations for federated learning among WTRUs to dynamically determine and adjust CP sizes based on delay spread measurements using CSI-RS resources, enabling WTRUs to request CP size changes and report delay spread information to optimize communication performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger cyclic prefix size is used to accommodate maximum delay spread, then signal decoding reliability is improved, but system overhead increases
Solution Approach 1:
The patent implements dynamic CP size selection where the WTRU measures delay spread and selects from multiple standardized CP sizes (e.g., 1/12, 1/24, 1/32 of OFDM symbol duration) based on the measured delay spread value. This dynamic adaptation allows the system to use larger CP sizes only when necessary, reducing overhead in environments with small delay spread while maintaining reliability when delay spread is large.
Solution Approach 2:
The patent changes the CP size parameter dynamically based on measured delay spread characteristics. The WTRU reports delay spread measurements to the network, which then configures appropriate CP sizes for different transmission scenarios. This parameter adaptation resolves the contradiction by matching CP size to actual channel conditions rather than using a fixed conservative size.
2Device complexity
If standardized CP sizes are used based on sub-carrier spacing mode, then device complexity is reduced, but adaptability to varying delay spreads deteriorates
Solution Approach 1:
The patent segments the CP size configuration into multiple standardized options (e.g., first CP size, second CP size, third CP size corresponding to different sub-carrier spacing modes). Each size is pre-defined and standardized, which simplifies the WTRU's task while enabling adaptation through selection from these segmented options based on measured delay spread and network configuration.
Solution Approach 2:
The patent implements a feedback mechanism where the WTRU measures delay spread and reports this information to the network node. The network then uses this feedback to configure the appropriate CP size for the WTRU. This feedback loop enables adaptability to varying delay spreads while maintaining standardized CP size options, resolving the contradiction between simplicity and adaptability.
3Loss of energy
If smaller cyclic prefix sizes are used for high sub-carrier spacing modes, then system overhead is reduced, but ability to mitigate inter-symbol interference deteriorates
Solution Approach 1:
The patent dynamically adjusts CP size based on the actual delay spread measurement and operational conditions. When operating with high sub-carrier spacing modes that inherently have smaller standard CP sizes, the system can still extend the CP size dynamically if delay spread measurements indicate the need for longer protection against ISI, thus resolving the overhead-reliability tradeoff.
Solution Approach 2:
The patent changes the CP size parameter independently of the sub-carrier spacing mode by measuring actual delay spread conditions. This allows the system to use smaller CP sizes for high SCS modes when delay spread is small (reducing overhead) while switching to larger CP sizes when delay spread increases (improving ISI mitigation), thereby resolving the contradiction between overhead reduction and interference protection.
Data Source
AI summary
A wireless transmit/receive unit (WTRU) may receive configuration information that indicates one or more of a first transmission configuration indicator (TCI) state, a second TCI state, a first cyclic prefix (CP) size, a first channel state information-reference signal (CSI-RS) resource set, and a second CSI-RS resource set. The WTRU may determine a first delay spread and a first measurement value associated with a first CSI-RS. The WTRU may determine a second delay spread and a second measurement value associated with a second CSI-RS. The WTRU may send a first indication indicating whether the first delay spread is greater than or less than the first CP size.