Random Access Preamble Sets Using Zadoff-Chu Cyclic Shifts
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Solution Overview
Problem
Current mobile communication systems face challenges in designing a set of Random Access Preambles (RAPs) that efficiently support varying cell radii without excessive signaling overload, as the number of preambles per root sequence (Npre) is limited, affecting uplink synchronization and detection performance.
Innovation Solution
A method is introduced to generate 64 RAPs using Zadoff-Chu sequences with pre-defined cyclic shift increments (NCS values) to ensure efficient uplink synchronization, where NCS values are selected from a limited set to minimize signaling overload and maximize Npre, while maintaining good autocorrelation and cross-correlation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of preambles per root sequence (Npre) is increased to support more RAPs, then the detection performance and uplink synchronization are improved, but the signaling overload increases and the device complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the cyclic shift increment (NCS) values from which the preambles are generated. By selecting specific NCS values from a predefined set, the system optimizes the number of usable preambles per root sequence without increasing the total number of root sequences, thereby improving detection performance while controlling signaling overhead.
Solution Approach 2:
The patent makes the system more universal by designing a configurable framework where a limited set of NCS values can be selected based on different cell radii and deployment scenarios. This allows the same base station to adapt to various network conditions without requiring additional hardware or signaling resources, achieving multi-functionality with existing resources.
2Adaptability or versatility
If the number of preambles per root sequence (Npre) is increased to support varying cell radii, then the adaptability to different cell sizes is improved, but the number of root sequences (Nr) must increase which increases device complexity
Solution Approach 1:
The patent introduces dynamics by allowing the selection of different NCS values based on the cell radius and network conditions. Instead of using a fixed number of preambles per root sequence, the system can dynamically adjust which preambles are usable by selecting appropriate NCS values, enabling adaptation to varying cell radii without increasing the number of root sequences.
Solution Approach 2:
The patent changes the parameter NCS from a fixed value to a selectable set of values {0, 13, 15, 18, 22, 26, 32, 38, 46, 59, 76, 93, 119, 167, 279, 419}. This parameter change allows the system to optimize preamble generation for different cell radii while maintaining a constant number of root sequences, thus improving adaptability without increasing device complexity.
3Quantity of substance
If more root sequences (Nr) are used to generate 64 RAPs, then the number of available preambles is sufficient, but the number of disjoint sets of RAPs (ND) decreases which affects network planning
Solution Approach 1:
The patent changes the approach from increasing the number of root sequences to optimizing the cyclic shift increment values. By carefully selecting NCS values from the predefined set, the system ensures that 64 unique preambles can be generated from fewer root sequences, thereby maintaining the quantity of available preambles while increasing the number of disjoint sets for better network planning.
Data Source
AI summary
A method of facilitating a user equipment (UE) communicating with a base station (BS) via a cell of a mobile communications system is disclosed. The UE selects a random access preamble sequence from a set of random access preamble sequences and transmits the random access preamble sequence to the BS. The BS receives the random access preamble sequence and estimates a time of arrival of the random access preamble sequence. A pre-defined set is used in generating the set of random access preamble sequences via at least one Zadoff-Chu sequence. The pre-defined set including all of the following values: 0, 13, 15, 18, 22, 26, 32, 38, 46, 59, 76, 93, 119, 167, 279, 419.