CAZAC Sequence Cyclic Prefix Adjustment for Random Access
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Solution Overview
Problem
Current wireless communication technologies face difficulties in determining how to extend Constant Amplitude Zero Auto-Correlation (CAZAC) sequences for Random Access Channel (RACH) signals, particularly in larger cell sizes, and in setting the cyclic prefix (CP) and zero-correlation zone (ZCZ) lengths to maintain orthogonality and ensure proper sequence detection.
Innovation Solution
A method for generating iterative sequences by repeating the cyclic prefix and adjusting the lengths of CP and ZCZ in proportion to cell size, allowing user equipment to select sequences based on received information from the Node-B, ensuring proper timing detection and reducing sequence ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If CAZAC sequences are extended for larger cell sizes, then the coverage area is improved, but the orthogonality and sequence detection accuracy deteriorate
Solution Approach 1:
The extended CAZAC sequence is segmented into multiple copies of the base sequence separated by cyclic prefixes. This segmentation maintains the orthogonality property while extending the effective sequence length to cover larger cell sizes, allowing the Node-B to detect timing points accurately even in extended coverage areas.
Solution Approach 2:
The patent changes the structure parameter of the sequence by introducing cyclic prefixes between sequence copies and adjusting the zero-correlation zone length. This parameter change maintains orthogonality and detection accuracy while enabling the sequence to function effectively over larger cell sizes.
2Reliability
If the cyclic prefix length is increased to maintain orthogonality in larger cells, then the orthogonality is improved, but the signaling overhead increases
Solution Approach 1:
The patent makes the cyclic prefix length dynamic by setting it proportional to the cell size rather than using a fixed length. This allows the system to adapt the CP length to actual cell size requirements, maintaining orthogonality in larger cells while minimizing unnecessary signaling overhead in smaller cells.
3Productivity
If multiple sequences are made available for random access, then the access capacity is improved, but the sequence ambiguity increases
Solution Approach 1:
The patent applies preliminary circular shifts to the base CAZAC sequence to generate multiple orthogonal sequences before transmission. This preliminary action ensures that sequences remain orthogonal and unambiguous even when multiple sequences are available for random access, allowing the Node-B to easily distinguish between different user equipment signals.
Data Source
AI summary
A method is provided for performing a random access procedure by a Node-B with a specific user equipment (UE) within a cell in which a plurality of UEs are located together. The Node-B transmits a random access procedure configuration including a basic sequence index related with a random access channel and zero correlation zone (ZCZ) configuration. The Node-B receives a random access preamble corresponding to the random access procedure configuration from the UE over the random access channel. A length of a cyclic part and a length of a sequence part of the random access preamble are differently given based on the random access procedure configuration. The random access preamble is generated from Constant Amplitude Zero Auto-Correlation (CAZAC) sequences based on the basic sequence index by applying a length of a cyclic shift according to the ZCZ configuration.