Zadoff-Chu Preamble Generation via Double Iteration
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Solution Overview
Problem
The existing methods for generating preambles in LTE systems using Zadoff-Chu sequences are complex due to the need for direct Discrete Fourier Transform (DFT) calculations, which are cumbersome for prime-length sequences, leading to high computational complexity and storage requirements.
Innovation Solution
A double iteration method is employed to calculate the DFT of Zadoff-Chu sequences with cyclic shifts, simplifying the process through integer additions, subtractions, and table look-ups, avoiding complex multiplications and fixed-point operations, thereby reducing computational and storage needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct DFT calculation is used for prime-length Zadoff-Chu sequences, then the preamble generation follows the standard LTE procedure, but the computational complexity and storage requirements increase significantly
Solution Approach 1:
The patent segments the direct DFT calculation into two parts: (1) pre-computation and storage of DFT basis values W_N^k for k=0 to N-1, and (2) efficient computation of the ZC sequence values x_u(n) using the closed-form formula. This segmentation allows the complex DFT operation to be broken down into manageable components that can be computed and stored separately, reducing the real-time computational burden while maintaining accuracy.
Solution Approach 2:
The patent applies preliminary action by pre-computing and storing the DFT basis values W_N^k in a lookup table before actual preamble generation. This pre-computation eliminates the need to perform complex exponential calculations during real-time preamble generation, significantly reducing computational complexity while ensuring the correctness of the DFT operation is maintained through stored accurate values.
2Ease of manufacture
If conventional FFT method is used, then the DFT can be realized through series connection of base station modules, but it requires the sequence length to be dividable which is not suitable for prime-length ZC sequences
Solution Approach 1:
The patent changes the parameter of sequence length adaptability by using the closed-form ZC sequence formula x_u(n) = exp(-jπu n (n+1)/N) which is valid for any N including prime numbers. This parameter change allows the system to handle prime-length sequences that cannot be processed by conventional FFT methods requiring composite lengths, thereby improving versatility while maintaining implementation feasibility through direct formula evaluation.
3Measurement precision
If complex multiplication and modular arithmetic are used in ZC sequence calculation, then the DFT of cyclic shift ZC sequence can be computed, but the algorithm remains very complex with large amounts of computation
Solution Approach 1:
The patent uses copying by storing pre-computed DFT basis values W_N^k in a lookup table, effectively creating a copy of these values for rapid retrieval. This copying approach replaces complex real-time calculations with simple table lookups, significantly improving calculation efficiency while maintaining the precision of the DFT operation through accurate stored values.
Solution Approach 2:
The patent applies preliminary action by pre-computing the DFT basis values and storing them in a lookup table before actual preamble generation. This pre-computation eliminates the need to perform complex exponential and modular arithmetic operations during real-time processing, thereby improving productivity while maintaining the measurement precision through accurate pre-stored values.
Data Source
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AI summary
The disclosure involves a method and an apparatus for implementing preamble generation. The method comprises: obtaining a first parameter value according to a root sequence number of a Zadoff-Chu (ZC) sequence; obtaining an initial value of a first sequence, according to a length and a cyclic shift value of the ZC sequence and the obtained first parameter value; performing iterative calculatings on the first sequence according to the initial value of the first sequence and the first parameter value; performing iterative calculatings on a second sequence according to the iteratively calculated values of the first sequence and a preset initial value of the second sequence; performing Discrete Fourier Transform (DFT) on the iteratively calculated values of the second sequence. The method and apparatus in the disclosure can achieve low complexity and high calculation precision in the calculation process and greatly reduce the amount of calculation and storage.