OFDM PAR Reduction via Data-Dependent Scrambler Sequences
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current OFDM transmit waveforms face high Peak-to-Average-Ratio (PAR) levels, leading to increased power consumption due to larger power amplifiers, and clipping techniques introduce undesirable out-of-band frequency components.
Innovation Solution
A PAR reduction system that generates a secondary scrambler sequence based on data to be scrambled, combining it with a primary scrambler sequence to produce a PAR reduction sequence, which randomizes the baseband data and reduces PAR levels without introducing high out-of-band frequency components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If clipping technique is used to reduce PAR levels, then power amplifier size and power consumption are reduced, but high out-of-band frequency components are produced
Solution Approach 1:
The patent introduces an intermediary signal processing stage that modifies the transmit waveform before amplification. By applying a PAR reduction sequence to the baseband signal, the waveform's peak characteristics are altered without requiring hard clipping, thus reducing the need for large linear power amplifiers while avoiding the generation of harmful out-of-band emissions that result from conventional clipping techniques.
Solution Approach 2:
The patent changes the statistical parameters of the transmit waveform by multiplying it with a PAR reduction sequence. This transformation modifies the amplitude distribution and peak characteristics of the signal, thereby reducing the PAR value and allowing the power amplifier to operate more efficiently without introducing distortion or out-of-band emissions.
2Reliability
If larger power amplifiers are used to handle high PAR levels, then linear operation and signal quality are maintained, but device size and power consumption increase
Solution Approach 1:
The patent applies preliminary signal processing to modify the transmit waveform's peak characteristics before it reaches the power amplifier. By pre-reducing the PAR through sequence multiplication, the power amplifier is presented with a signal that has more favorable statistical properties, allowing it to operate in a more efficient region without sacrificing signal quality or linearity.
3Loss of information
If conventional scrambling is used, then data security and randomization are achieved, but PAR levels remain high during non-data transmission
Solution Approach 1:
The patent merges the data scrambling function with the PAR reduction function into a single unified process. The PAR reduction sequence serves dual purposes: it randomizes the data for security purposes while simultaneously modifying the waveform's peak characteristics to reduce PAR. This combination eliminates the need for separate scrambling and PAR reduction stages, and addresses the high PAR issue during non-data transmission periods.
Data Source
AI summary
Methods and apparatus for reduction of a peak to average ratio for an OFDM transmit signal. In an aspect, a method is provided for reducing a peak to average ratio of a transmit waveform. The method includes obtaining a primary scrambler sequence, generating a secondary scrambler sequence having a length characteristic based on data to be scrambled, and combining the primary and secondary scrambler sequences to produce a PAR reduction sequence. In another aspect, an apparatus is provided for reducing a peak to average ratio of a transmit waveform. The apparatus includes a secondary generator configured to generate a secondary scrambler sequence having a length characteristic based on data to be scrambled, and combining logic configured to combine a primary scrambler sequence and the secondary scrambler sequences to produce a PAR reduction sequence.