Low PAPR CAZAC Sequence Generation for Random Access
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Solution Overview
Problem
In EUTRAN, hard handovers between different cells result in interrupted data transmission and increased buffer accumulation due to prolonged handover times, and the peak-to-average power ratio (PAPR) of CAZAC sequences used in random access signals leads to signal distortion and power amplification issues.
Innovation Solution
A mobile station is configured to transmit a random access signal using a prescribed CAZAC sequence, such as a Zadoff-Chu sequence, with a selected sequence index that minimizes PAPR, and synchronizes with the handover destination by aligning the uplink and downlink frequency positions, allowing for reduced power back-off and efficient handover execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a CAZAC sequence is used as a preamble in random access signal, then excellent autocorrelation and cross-correlation characteristics are obtained, but the peak-to-average power ratio (PAPR) increases causing signal distortion and power amplification issues
Solution Approach 1:
The patent applies parameter changes by modifying the phase rotation parameter (alpha) of the CAZAC sequence to optimize the PAPR characteristics. Specifically, the patent sets alpha to specific values (0, pi/4, pi/2, or 3pi/4) to minimize PAPR while maintaining the excellent correlation properties of CAZAC sequences. This parameter optimization resolves the contradiction between maintaining reliability through CAZAC sequence properties and reducing harmful PAPR effects.
2Speed
If hard handover is performed between different cells, then handover can be completed in short period, but data transmission is interrupted and buffer accumulation increases
Solution Approach 1:
The patent applies preliminary action by performing buffer status reporting and data buffering before the handover is completed. The source base station buffers downlink data and reports buffer status to the network before the handover finishes, allowing for proactive data management. This reduces the impact of transmission interruption by preparing data transfer in advance, thus resolving the contradiction between fast handover completion and minimizing data loss.
3Adaptability or versatility
If synchronization channels are arranged around the middle of downlink transmission bandwidth, then terminal stations can perform initial search and handover easily regardless of system bandwidth, but uplink and downlink frequency position alignment becomes complex
Solution Approach 1:
The patent applies local quality by establishing a specific frequency relationship between uplink and downlink synchronization channels. The patent specifies that the center frequency of the uplink synchronization channel should be located at a frequency position that corresponds to the center frequency of the downlink synchronization channel, with a specific frequency offset relationship. This localized frequency alignment rule simplifies the overall system complexity while maintaining adaptability for terminal stations to perform initial search and handover across different bandwidth configurations.
Data Source
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AI summary
A mobile station, configured to establish an uplink wireless connection by transmitting a random access signal through a random access channel after receiving a synchronization channel transmitted from a radio base station in a handover destination, comprises a preamble generating unit for restricting a CAZAC sequence used as a preamble of the random access signal to a prescribed CAZAC sequence from among a plurality of CAZAC sequences with different indexes, and generating the preamble of the random access signal using the prescribed CAZAC sequence.