OFDM Preamble Generation with Low PAPR and Arbitrary Lengths
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Solution Overview
Problem
Existing OFDM systems face challenges in generating preambles with low Peak-to-Average-Power Ratio (PAPR) and arbitrary lengths, which are necessary for efficient signal transmission and synchronization, especially due to the high PAPR caused by multiplexing of subcarriers.
Innovation Solution
A preamble generating apparatus and method that includes a reception unit for setting information, a preamble-elements generating unit, a preamble-model creating unit, a PAPR calculator, and a deciding unit to generate preambles using a Frank-Zadoff sequence, allowing for the creation of preambles with arbitrary lengths and low PAPR by optimizing the placement of elements and calculating the minimum PAPR for use in communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a CAZAC sequence is repeated to generate a preamble, then the PAPR is reduced, but the preamble length is restricted to power of two
Solution Approach 1:
The preamble generation process is segmented into multiple stages: generating a base CAZAC sequence, creating a template with guard intervals and DC components, and then mapping the base sequence onto the template. This segmentation allows the preamble to have arbitrary length while maintaining low PAPR characteristics through the CAZAC sequence.
Solution Approach 2:
The invention changes the parameters of the preamble generation process by allowing the base CAZAC sequence length to differ from the final preamble length. By controlling the mapping process and template structure, the system achieves arbitrary preamble lengths while preserving the low PAPR property of the underlying CAZAC sequence.
2Length of moving object
If the recursion of CAZAC sequence increases (two, four, etc.), then the preamble length increases, but the PAPR becomes higher
Solution Approach 1:
The invention introduces a template structure as an intermediary between the base CAZAC sequence and the final preamble. This template includes guard intervals and DC component positions, allowing the system to achieve arbitrary preamble lengths without directly increasing CAZAC sequence recursion, thereby maintaining low PAPR.
3Reliability
If guard subcarriers are added to avoid spectral interference, then communication reliability improves, but preamble length increases
Solution Approach 1:
The template is prepared in advance with guard interval positions and DC component positions predetermined. This preliminary structuring allows guard subcarriers to be efficiently incorporated into the preamble without unnecessarily increasing length, as the mapping process directly places CAZAC sequence elements in the appropriate non-guard positions.
Data Source
AI summary
A preamble generating apparatus used for synchronization of a reception apparatus in an orthogonal frequency division multiplexing system and generating a preamble to be added to a beginning of data at a time of communication, receives preamble length identifying information and position specifying information, and generates a plurality of elements constituting a preamble according to a predetermined sequence based on those information. The preamble generating apparatus creates a preamble model, and generates a plurality of preambles by setting the generated elements at positions of elements in element deciding information included in the preamble model, the positions indicating elements in the preamble model which are to be used in data communication. The preamble generating apparatus calculates PAPRs respectively corresponding to the plurality of preambles, and compares the PAPRs of the preambles with one another to decide the preamble corresponding to a minimum PAPR as a preamble to be used in communication.