Synchronization Signal Design Using Symmetric Zadoff-Chu Sequences
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Solution Overview
Problem
Existing synchronization schemes in OFDM systems face challenges in optimizing performance due to constraints on power consumption, cost, and radio reception sensitivity, with prior art proposals either reducing frequency diversity or increasing cross-correlations and Peak-to-Average-Power-Ratio (PAPR) values.
Innovation Solution
A method is introduced to establish a synchronization signal using centrally symmetric discrete Fourier frequency coefficients and number sequences, which allows for efficient implementation of a matched filter receiver and maximizes signal-to-noise ratio, utilizing all available subcarriers and reducing PAPR values by defining the sequence as centrally symmetric and puncturing the central element of a Zadoff-Chu sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Zadoff-Chu sequences of length 71 with specific root indices are used for PSC synchronization, then cell search capability is improved, but PAPR values increase and frequency diversity is reduced
Solution Approach 1:
The patent changes the sequence length parameter from 71 to 72 to achieve optimal PAPR properties while maintaining good autocorrelation characteristics for synchronization. This parameter change resolves the contradiction by finding a sequence length that balances synchronization accuracy with acceptable PAPR values
Solution Approach 2:
The patent introduces an asymmetric modification to the Zadoff-Chu sequence by puncturing specific elements (setting certain positions to zero) to create a modified sequence that achieves lower PAPR while maintaining the essential correlation properties needed for accurate synchronization
2Measurement precision
If synchronization sequences are designed to improve autocorrelation properties, then timing estimation accuracy is improved, but cross-correlations between different cell identities increase
Solution Approach 1:
The patent applies different root indices u to different cell identity groups, creating local variations in the sequence properties. This allows each cell to have optimized autocorrelation for timing estimation while the diversity of root indices across cells reduces mutual cross-correlations
Solution Approach 2:
The patent segments the set of synchronization sequences into multiple groups based on cell identity, with each group using sequences with specific root indices. This segmentation strategy ensures that sequences within each group have good autocorrelation properties while sequences across different groups have reduced cross-correlations
3Ease of manufacture
If OFDM synchronization signals use non-centrally symmetric sequences, then implementation is simpler, but matched filter efficiency is reduced and computational complexity increases
Solution Approach 1:
The patent intentionally introduces central symmetry to the Zadoff-Chu sequences, which creates a specific asymmetric property (symmetry about the center point) that enables efficient matched filter implementation. This controlled asymmetry reduces computational complexity while maintaining implementation simplicity
4Adaptability or versatility
If all available subcarriers are utilized for synchronization signals, then frequency diversity is improved, but PAPR values increase
Solution Approach 1:
The patent changes the sequence length to 72, which perfectly matches the number of available subcarriers, enabling utilization of all subcarriers for frequency diversity while the specific structure of the modified Zadoff-Chu sequence maintains acceptable PAPR values
Solution Approach 2:
The patent converts the potentially harmful high PAPR effect of using all subcarriers into a benefit by using the specific modified Zadoff-Chu sequence structure, which transforms the high peak power issue into an opportunity to achieve optimal frequency diversity with controlled PAPR through the mathematical properties of the sequence
Data Source
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AI summary
The invention concerns a method of establishing a synchronisation signal in a communication system. A set of discrete Fourier frequency coefficients is defined and transformed into a discrete time representation, the discrete time representation being particularly useful as a synchronisation signal. According to example embodiments of the invention, signal symmetry is exploited. Preferably, the centre frequency, also referred to as DC subcarrier, is not used for transmission. The invention also concerns transmitter and receiver of a communication system.