Cubic Phase Polynomial Sequences for 5G PRACH Capacity
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Solution Overview
Problem
The 5G NR standard faces a PRACH capacity shortfall due to the combination of large subcarrier spacing and short sequence length, leading to a reduction in the number of available ZC sequences for random access, which increases interference and reduces detection accuracy.
Innovation Solution
A network access node generates a subset of cubic phase polynomial sequences with specific auto- and cross-correlation properties, allowing for increased sequence availability without increasing interference, by using element-by-element multiplication of Zadoff-Chu sequences with Alltop sequences and cyclically shifted versions, ensuring low correlation and orthogonal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Zadoff-Chu sequences are used for PRACH in 5G NR with large subcarrier spacing and short sequence length, then the system supports new use cases like low-latency and high-speed transmissions, but the number of available sequences decreases drastically leading to PRACH capacity shortfall
Solution Approach 1:
The patent changes the mathematical parameters of the sequences by introducing cubic phase polynomial sequences with controlled third-order coefficients, transitioning from traditional Zadoff-Chu sequences to a new sequence family that provides both adaptability for 5G NR and sufficient quantity of available sequences
Solution Approach 2:
The patent creates composite sequences by combining cubic phase polynomials with specific coefficient structures, merging the benefits of low correlation properties with increased sequence availability to solve the capacity shortfall problem
2Quantity of substance
If the number of PRACH sequences is increased to solve capacity shortfall, then sequence availability improves, but interference between sequences increases reducing detection accuracy
Solution Approach 1:
The patent carefully controls the third-order coefficient parameter in cubic phase polynomial sequences to maintain low cross-correlation properties even when increasing the total number of sequences, thereby increasing capacity without proportionally increasing interference
Solution Approach 2:
The patent applies different cubic phase polynomial structures with specific coefficient values to different sequence groups, creating local variations in sequence properties that reduce overall interference while maintaining high sequence availability
Data Source
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AI summary
The invention relates to a network access node (100) and a client device (300) for generating and using cubic phase polynomial sequences (s i , s j ) of length L with a third order coefficient value a 3 belonging to the subset of sequences (S k ). The network access node (100) transmits a control message (510) to the client device (100), wherein the control message (510) indicates the cyclical shift value N cs and the third order coefficient value a 3 . The client device (300) receives the control message (510) and determines a cubic polynomial phase sequence (s i ) belonging to the subset of sequences (S k ) based on the cyclical shift value N cs and the third order coefficient value a 3 . The client device (300) thereafter transmits the determined cubic polynomial phase sequence (s i ) as a random access preamble (520) to the network access node (100). Due to the properties of said cubic phase polynomial sequences (s i , s j ) the number of available sequences for random access in cells is provided without increasing interference. Furthermore, the invention also relates to corresponding methods, and a computer program.