OFDM-Based OOK Cyclic Prefix Design to Avoid False Transitions
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Solution Overview
Problem
In OFDM-based OOK waveforms for ultra-low power devices, the conventional CP generation method introduces false transitions at symbol boundaries due to duplicating the end of the OFDM symbol, degrading envelope detection performance, especially under large sampling frequency offset conditions.
Innovation Solution
Generate the CP by duplicating samples from the beginning of the first OOK chip in an OFDM symbol and adjust the duration to ensure uniform chip length, thereby avoiding artificial edges at symbol boundaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CP is generated by duplicating the end of the OFDM symbol, then the CP effectively mitigates inter-symbol interference for FFT-based OFDM receivers, but false transitions are introduced at symbol boundaries that degrade envelope detection performance
Solution Approach 1:
Instead of duplicating the end of the OFDM symbol (conventional approach), the patent duplicates the beginning of the first OOK chip to generate the CP. This inversion of the duplication source eliminates false transitions at symbol boundaries while maintaining ISI mitigation, as the duplicated beginning portion does not create artificial edges when appended to the symbol end
2Ease of operation
If the conventional CP duplication method is used, then synchronization is facilitated, but receiver complexity increases due to the need to handle false transitions under large sampling frequency offset conditions
Solution Approach 1:
The patent extracts only the essential function of the CP (ISI mitigation and synchronization) by duplicating the beginning of the first OOK chip rather than the entire end of the symbol. This extraction approach eliminates the harmful false transitions while preserving the beneficial synchronization properties, thereby reducing receiver complexity for handling large sampling frequency offsets
Data Source
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AI summary
A system and a method are disclosed for transmitting data in a wireless communication network. The method includes transmitting, by a network node, a bit stream comprising ambient Internet of things, A-IoT, data; generating an on-off keying, OOK, OOK-1 or OOK-4 modulated waveform; generating a cyclic prefix, CP, by duplicating one or more samples of a first OOK chip in the waveform; appending the CP at the beginning of the first OOK chip in the waveform; and transmitting the waveform with the appended CP over a wireless channel to one or more A-IoT devices.