CAZAC Sequence Preamble for Random Access Channel Capacity
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Solution Overview
Problem
Existing methods for transmitting data through a random access channel in mobile communication systems face limitations in increasing the number of available code sequences while maintaining excellent transmission characteristics, leading to performance attenuation due to channel changes and noise susceptibility.
Innovation Solution
The proposed solution involves generating new code sequences by multiplying existing code sequences with exponential sequences, conjugating elements within code sequence blocks, combining first code sequences to indicate information bits, and creating combination code sequences through circular shifts and cyclic prefixes, thereby expanding the code sequence length and improving transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CAZAC sequence is used for random access channel transmission, then excellent transmission characteristics are achieved, but the number of available sequences is limited to N-1 for a sequence of length N
Solution Approach 1:
The CAZAC sequence is divided into multiple blocks, and different conjugation patterns are applied to different blocks. This segmentation allows the same base sequence to generate multiple distinct sequence sets, effectively increasing the number of available sequences while maintaining the excellent correlation properties of the original CAZAC sequence.
Solution Approach 2:
The patent combines CAZAC sequences with conjugation operations to create composite sequence structures. By applying conjugation to specific blocks of the CAZAC sequence, new sequence variants are generated that maintain the mathematical properties of CAZAC sequences while expanding the total number of available sequences beyond the traditional N-1 limit.
2Loss of information
If additional information is transmitted through Walsh sequence in CDM mode, then message information can be conveyed, but only log2 N bits of additional information are obtained when Walsh sequence has length N
Solution Approach 1:
Instead of relying solely on Walsh sequence length to determine information capacity, the patent introduces a time-dimensional approach by dividing the CAZAC sequence into multiple blocks and applying different conjugation patterns to each block. This transforms the information encoding from a single-dimension (Walsh sequence selection) to a multi-dimensional system (block index × conjugation pattern), significantly increasing the bits of additional information that can be transmitted.
3Loss of information
If Walsh sequence is mixed with CAZAC sequence for data transmission, then data can be conveyed, but the Walsh sequence acts as noise in detection of CAZAC sequence
Solution Approach 1:
The patent extracts the data transmission function from the CAZAC sequence structure itself by using conjugation operations on different blocks, rather than mixing a separate Walsh sequence. This separation allows the CAZAC sequence to maintain its pure correlation properties for detection while the conjugation patterns carry the data information, eliminating the noise interference problem.
4Reliability
If repetitive sequences are transmitted to prevent Walsh sequence from acting as noise, then detection reliability is improved, but access time increases
Solution Approach 1:
Instead of transmitting multiple repetitive sequences to improve detection reliability, the patent uses a single CAZAC sequence with different conjugation patterns applied to different blocks. The receiver can detect the sequence ID from this single transmission by analyzing the conjugation patterns across blocks, achieving both reliability and time efficiency without requiring repetitive transmissions.
Data Source
AI summary
Disclosed is a data transmission method in a mobile communication system. The data transmission method through a code sequence in a mobile communication system includes grouping input data streams into a plurality of blocks consisting of at least one bit so as to map each block to a corresponding signature sequence, multiplying a signature sequence stream, to which the plurality of blocks are mapped, by a specific code sequence, and transmitting the signature sequence stream multiplied by the specific code sequence to a receiver.