DFT-Based Random Access Preambles for Sequence Collision Reduction
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Solution Overview
Problem
Existing wireless communication systems, such as 4G and 5G networks, face limitations in the number of unique sequences that can be generated for random access procedures due to constraints in Zadoff-Chu sequences, restricting the number of devices that can concurrently perform random access procedures.
Innovation Solution
Implementing partial discrete Fourier transform (DFT)-based sequence design, which includes generating sequences through deterministic sampling of DFT matrices, using quadratic, cubic, or Fibonacci-type sampling functions, and applying sequence masking and interleaving to enhance sequence properties and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Zadoff-Chu sequences are used for random access preambles, then sequence generation is simple and orthogonal properties are maintained, but the number of unique sequences is limited
Solution Approach 1:
The patent segments the DFT matrix into multiple columns, where each column represents a base sequence. This segmentation allows generation of multiple unique sequences from a single matrix structure, resolving the contradiction by providing sequence diversity without requiring proportionally increased system complexity
Solution Approach 2:
The patent changes the parameter of sequence generation from fixed Zadoff-Chu formulations to flexible DFT-based generation with configurable sampling functions. By varying the sampling function parameters (quadratic, cubic, Fibonacci types) and DFT matrix dimensions, the system generates numerous unique sequences while maintaining manageable computational complexity
2Productivity
If more devices perform random access concurrently, then network capacity increases, but sequence collision probability increases with limited unique sequences
Solution Approach 1:
The patent transitions from one-dimensional Zadoff-Chu sequence generation to two-dimensional DFT matrix structure with row-column indexing. This dimensional expansion provides additional degrees of freedom for sequence generation, enabling support for more concurrent devices while maintaining unique sequence identification and reducing collision probability
3Quantity of substance
If deterministic sampling functions are used to generate sequences from DFT matrix, then sequence uniqueness increases, but computational complexity increases
Solution Approach 1:
The patent performs preliminary computation of the DFT matrix structure and stores it for reuse. By pre-computing the matrix and its columns, the system avoids redundant calculations during sequence generation, thereby increasing the number of unique sequences available while keeping the computational complexity manageable through caching and reuse
Data Source
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AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may transmit a random access preamble to a base station as part of a two-step random access procedure. The UE may generate the preamble by identifying a discrete Fourier transform (DFT) matrix and generating a set of sequences based on the DFT matrix. Each sequence of the set of sequences may be generated by selecting a column of the DFT matrix and performing deterministic sampling of respective entries from the selected column in accordance with a sampling function. The UE may then select a sequence from the set of sequences based on generating the set of sequence. The UE may transmit the selected sequence to a wireless device (e.g., a base station).