OFDM Preamble Sequence Generation Using Golay Complementary Codes
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Solution Overview
Problem
Existing OFDM communication systems face challenges with high peak-to-average power ratio (PAPR) in preamble sequences, leading to performance deterioration and increased processing time for minimal PAPR generation.
Innovation Solution
The use of Golay complementary sequences to generate preamble sequences with a PAPR less than 3 dB by mapping elements to subcarriers and inserting null data, minimizing operations and optimizing subcarrier usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional preamble sequences are used in OFDM systems, then synchronization can be achieved, but the peak-to-average power ratio (PAPR) becomes excessively high causing signal distortion and performance deterioration
Solution Approach 1:
The patent transforms the frequency-domain preamble sequence into a time-domain sequence with controlled PAPR by applying IFFT with specifically designed phase rotations on subcarriers. This parameter transformation in the frequency domain (phase shifts) results in a time-domain sequence with reduced peak power, directly resolving the PAPR issue while maintaining synchronization functionality
Solution Approach 2:
The patent constructs a composite preamble sequence by combining multiple components: a base sequence for synchronization, phase rotation factors for PAPR reduction, and null data placements for spectral shaping. This composite structure achieves both low PAPR and effective synchronization, resolving the contradiction between reliability and harmful factors
2Object-affected harmful factors
If minimal PAPR preamble sequences are generated using conventional methods, then signal quality is maintained, but the processing time and computational complexity increase significantly
Solution Approach 1:
The patent divides the preamble generation process into distinct segments: frequency-domain sequence definition, phase rotation application, IFFT transformation, and null data insertion. This segmentation allows each step to be optimized independently, reducing overall processing time while maintaining low PAPR characteristics
Solution Approach 2:
The patent performs preliminary phase rotation calculations in the frequency domain before the IFFT transformation. By pre-computing the phase factors and organizing the frequency-domain sequence with null data positions predetermined, the actual time-domain generation requires minimal computation, significantly reducing processing time
Data Source
AI summary
A method for generating a preamble sequence in an orthogonal frequency division multiplexing (OFDM) communication system having A subcarriers in a frequency domain. The method comprises generating a length-2×M×N preamble sequence, where 2×M×N is less than A, by using a length-N Golay complementary sequence and a length-M Golay complementary sequence; and assigning elements constituting the preamble sequence to 2×M×N subcarriers among the A subcarriers on a one-to-one mapping basis, assigning null data to the remaining subcarriers excluding the 2×M×N subcarriers from the A subcarriers, and then IFFT-transforming the assigned result into time-domain data.