LTE Broadcast Cyclic Prefix Configuration for Delay Spread
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Solution Overview
Problem
Current LTE technology faces challenges in maintaining efficient wireless communication due to insufficient cyclic prefix duration, leading to inter-symbol interference, especially in scenarios with large delay spreads, which affects the quality of broadcast services.
Innovation Solution
The method involves selecting a cyclic prefix overhead for OFDMA symbols based on an integer multiple of a standard carriers-to-resource blocks definition, ensuring the cyclic prefix duration results in an integer number of carriers per resource block, thereby optimizing the cyclic prefix duration and overhead for extended duration cyclic prefixes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cyclic prefix duration is extended to mitigate inter-symbol interference in large delay spreads, then the reliability of broadcast services is improved, but the overhead increases
Solution Approach 1:
The patent changes the cyclic prefix parameter from fixed to variable by introducing different cyclic prefix durations (normal and extended) based on the delay spread characteristics of the broadcast channel. This allows the system to adapt the cyclic prefix length to match the actual channel conditions, providing sufficient protection against inter-symbol interference only when needed, thereby improving reliability without unnecessarily increasing overhead in all cases.
Solution Approach 2:
The patent implements dynamic selection of cyclic prefix duration based on channel delay spread measurements. The system can switch between normal cyclic prefix (NCP) and extended cyclic prefix (ECP) modes depending on the detected channel conditions, making the cyclic prefix length adaptive rather than static. This dynamic approach ensures optimal performance across varying broadcast scenarios while minimizing overhead when extended protection is not required.
2Object-affected harmful factors
If the cyclic prefix overhead is increased to cover larger delay spreads, then inter-symbol interference is reduced, but the spectral efficiency deteriorates
Solution Approach 1:
The patent modifies the cyclic prefix duration parameter to match the actual delay spread of the broadcast channel. By using normal cyclic prefix for small delay spreads and extended cyclic prefix only when necessary, the system achieves effective inter-symbol interference mitigation without consistently incurring the spectral efficiency penalty that would result from always using extended cyclic prefix.
3Reliability
If the cyclic prefix duration is extended to ensure coverage of large delay spreads, then the reliability of wireless communication is improved, but the overhead increases
Solution Approach 1:
The patent implements dynamic adaptation of cyclic prefix duration based on measured channel delay spread characteristics. The system monitors the broadcast channel conditions and selectively applies extended cyclic prefix only when the delay spread exceeds the threshold that normal cyclic prefix can handle. This dynamic approach ensures high reliability in challenging conditions while minimizing overhead in favorable conditions, resolving the contradiction between reliability and overhead.
Data Source
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AI summary
Extended duration cyclic prefixes with lower overhead are disclosed in which an integer multiple sequence of carriers above the nominal 300 carrier-per-25 resource blocks (RBs) definition are selected to reduce the cyclic prefix overhead below the normative 20%. Sets of durations are then provided associated with each such integer multiple sequence of carriers that allow for the combined duration of the symbol duration and extended duration cyclic prefix to result in an integer number of carriers for each RB.