PRACH Preamble Scrambling for Collision Detection
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Solution Overview
Problem
In Next-generation Radio (NR) Physical Random Access Channel (PRACH) systems, existing M-stage preamble sequences may be detected inaccurately when multiple User Equipments (UEs) transmit over the same time-frequency resource, leading to collisions and incorrect detection of preamble sequences.
Innovation Solution
The method involves scrambling and descrambling preamble sub-sequences using a cyclic shift value from the previous stage's preamble sub-sequence index or linearly mapped value, ensuring accurate detection by configuring pseudo-random noise sequences for scrambling and descrambling processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If M-stage preamble sequences are used to improve detection performance and reduce collision probability, then the reliability of preamble detection is improved, but the complexity of the detection process increases due to the need to detect multiple preamble sub-sequences
Solution Approach 1:
The preamble sequence is divided into M preamble sub-sequences transmitted in different stages. Each sub-sequence can be detected independently, allowing the system to improve reliability through multiple detection opportunities while managing complexity by processing each segment separately rather than as a single complex sequence
Solution Approach 2:
Cyclic shift values are determined in advance based on successfully detected preamble sub-sequences from previous stages. This preliminary determination of cyclic shift values enables the receiver to prepare appropriate detection parameters before receiving subsequent sub-sequences, improving detection reliability while maintaining manageable complexity through pre-computation
2Productivity
If multiple UEs transmit preamble sequences over the same time-frequency resource, then the resource utilization efficiency is improved, but the accuracy of preamble sequence detection deteriorates due to collisions and interference
Solution Approach 1:
By segmenting the preamble transmission into multiple stages with multiple sub-sequences, the system allows multiple UEs to share the same time-frequency resource while enabling the receiver to detect and identify individual sequences through multiple independent detection opportunities, thereby maintaining detection accuracy despite higher resource utilization
Solution Approach 2:
Cyclic shift values are determined in advance based on successfully detected preamble sub-sequences. This preliminary action enables the receiver to compensate for interference and collisions by using the detected cyclic shift information to correctly interpret subsequent sub-sequences, maintaining detection accuracy even when multiple UEs transmit simultaneously
Data Source
AI summary
A method and device for sending and receiving a preamble sequence of a physical random access channel, comprising: scrambling a preamble subsequence and then sending, the preamble subsequence being scrambled according to a cyclic shift value of a preamble subsequence sent in the previous stage; performing a descrambling operation according to a cyclic shift value of a preamble subsequence received in the previous stage during reception; and determining a preamble sub-sequence detected after descrambling as a preamble sub-sequence received in the current stage, where the received preamble sub-sequence in the current stage and the received preamble sub-sequence in the previous stage belong to the same preamble sequence.