Dynamic Frequency Interleaver for OFDM Noise Reduction
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Solution Overview
Problem
Existing frequency interleaving methods in OFDM systems are inefficient in eliminating highly noisy carriers or those affected by parasitic signals during transmission, as they do not adequately modify the transmission channel properties to reduce noise and maintain spectral efficiency.
Innovation Solution
A mixed method of dynamic interleaving that selects and positions zero carriers based on channel transfer function estimates, replacing noisy carriers with zero carriers and inserting them at variable positions within the OFDM multiplex to form blocks of symbols, thereby improving noise reduction and spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency interleaving is implemented to eliminate noisy carriers, then noise reduction is achieved, but temporal and frequency correlations are not sufficiently reduced
Solution Approach 1:
The patent applies dynamics by making the interleaving pattern variable over time through time-frequency interleaving. The interleaver dynamically adjusts the mapping between subcarriers across different time slots, preventing persistent correlation patterns and enabling the system to adapt to changing channel conditions, thereby simultaneously reducing noise impact and improving decision circuit reliability
Solution Approach 2:
The patent introduces another dimension by extending interleaving from purely frequency domain to time-frequency domain. This dual-dimensional approach adds temporal variation to the frequency-based interleaving, creating a more comprehensive decorrelation mechanism that addresses both noise reduction and reliability improvement
2Productivity
If zero carriers are inserted to replace noisy carriers, then spectral efficiency is maintained, but device complexity increases
Solution Approach 1:
The patent applies universality by designing an interleaver that simultaneously performs multiple functions: it interleaves data symbols, positions zero carriers, and manages time-frequency variations all within a single unified structure. This multi-functionality maintains spectral efficiency while avoiding the need for separate complex mechanisms for each function
3Object-affected harmful factors
If dynamic selection of orthogonal functions is implemented, then noise reduction is achieved, but processing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-defining a set of orthogonal functions (Walsh-Hadamard codes) and their corresponding interleaving patterns before transmission. The receiver can selectively apply the appropriate pre-configured function based on channel conditions, reducing the need for complex real-time processing while achieving noise and parasitic signal reduction
Data Source
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AI summary
The invention relates to an interleaving method (1) and a data symbol frequency interleaver (EF). The data symbols are allocated to carriers of a set NFF? of carriers of a multiplexing and modulating unit by means of orthogonal functions of a multicarrier transmission device (EM). The inventive method consists in selecting carriers used for transmitting data symbols from the carrier set in a time varying manner and in dynamically interleaving a block of carriers consisting of selected and zero carriers.