OFDM Transmitter Symbol Mapping for PAPR Reduction
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Solution Overview
Problem
In OFDM radio transmission, frequency selectivity fading causes significant fluctuations in subcarrier quality, leading to difficult demodulation and unnecessary transmission power consumption, particularly due to the repetition technology's excess quality and power consumption on subcarriers with excellent propagation paths.
Innovation Solution
A radio transmitting apparatus that replicates symbols, removes unnecessary symbols based on subcarrier propagation quality, and maps the rest onto subcarriers to generate a multicarrier signal, thereby reducing Peak to Average Power Ratio (PAPR) and transmission power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If repetition technology is used to improve signal quality through diversity combining, then signal quality is improved, but transmission power consumption increases unnecessarily
Solution Approach 1:
The patent applies local quality by differentiating the treatment of symbols based on their mapping locations. Symbols mapped to subcarriers with poor propagation quality (deep fades) are retained and repeated for diversity combining, while symbols mapped to subcarriers with good propagation quality are excluded from repetition. This selective approach ensures that repetition resources are allocated only where needed, improving signal quality in critical areas without wasting transmission power in areas where the channel is already good.
2Reliability
If repetition technology is used to ensure demodulation on poor subcarriers, then demodulation reliability is improved, but PAPR increases
Solution Approach 1:
The patent reduces PAPR by applying local quality assessment to each subcarrier. By identifying subcarriers with good propagation quality and excluding their corresponding symbols from repetition, the patent avoids creating redundant signal peaks that would increase PAPR. Only symbols on poor subcarriers are repeated, which maintains demodulation reliability while minimizing the generation of high peak power events.
Solution Approach 2:
The patent applies partial action by performing repetition only on a subset of symbols rather than all symbols. Specifically, it repeats only those symbols that are mapped to subcarriers experiencing deep fades, while excluding symbols on subcarriers with good propagation quality. This partial repetition approach is sufficient to ensure demodulation reliability for the critical symbols without the excessive PAPR increase that would result from repeating all symbols.
Data Source
AI summary
A radio transmitting apparatus wherein unnecessary consumption of transmission power can be suppressed and PAPR (Peak to Average Power Ratio) can be reduced in multicarrier communication. In the apparatus, a repetition part (105) replicates (repeats) each symbol outputted from a modulating part (103) to generate and output a plurality of identical symbols to an S/P part (107), which converts the symbol sequence outputted in series from the repetition part (105) into parallel symbol sequences and outputs them to an interleaver (109). The interleaver (109) then reorders the symbol sequences outputted from the S/P part (107) and outputs them to a mapping part (111), which removes, in accordance with the propagation path quality of each of subcarriers constituting OFDM symbols that are multicarrier signals, some of the identical symbols as replicated by the repetition part (105) and then maps the rest of the symbols onto subcarriers for application to an IFFT part (113).