Random Access Preamble Code Division Multiplexing
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Solution Overview
Problem
The existing random access preamble designs in 5G cellular communication systems face challenges with high phase noise and frequency errors at higher carrier frequencies, leading to increased hardware complexity and a higher collision probability due to a limited number of orthogonal sequences, which restricts access capacity.
Innovation Solution
The method involves creating a random access preamble using code division multiplexing of identical random access sequences in the frequency domain, transforming them into the time domain, and using orthogonal cover codes to reduce collision probability and improve access capacity without significant performance loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If code division multiplexing is applied to random access preambles, then access capacity is improved and collision probability is reduced, but processing complexity increases
Solution Approach 1:
The patent applies code division multiplexing by introducing a code domain dimension to the random access preamble structure. Multiple preambles are multiplexed using orthogonal cover codes in the code domain, allowing simultaneous access from multiple UEs without increasing time or frequency resources. This resolves the contradiction by improving access capacity through dimensionality expansion while keeping the physical layer structure manageable.
Solution Approach 2:
The patent segments the random access preamble into multiple sequences that are code-division multiplexed using orthogonal cover codes. Each UE is assigned a specific orthogonal code, and the preamble is divided into segments that can be independently processed. This segmentation allows the receiver to separate and detect multiple preambles simultaneously, improving access capacity while distributing processing complexity across multiple orthogonal code channels.
2Speed
If higher carrier frequencies are used in 5G, then bandwidth and data rate are improved, but phase noise and frequency error increase
Solution Approach 1:
The patent changes the structure of the random access preamble by applying code division multiplexing with orthogonal cover codes in the frequency domain. This parameter change in the preamble structure makes the system more robust to phase noise and frequency errors inherent in higher carrier frequencies, allowing 5G to achieve high data rates while maintaining reliability through the orthogonal code-based multiplexing approach.
3Productivity
If the number of orthogonal sequences is increased, then access capacity is improved, but collision probability increases due to limited orthogonal sequences
Solution Approach 1:
The patent resolves the contradiction by introducing a code domain dimension through orthogonal cover codes. Instead of relying solely on a limited set of orthogonal sequences in the time or frequency domain, the system multiplexes multiple preambles by assigning different orthogonal codes to different UEs. This creates additional orthogonal dimensions, significantly increasing access capacity while maintaining low collision probability through the orthogonality properties of the codes.
Data Source
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AI summary
One embodiment of the present disclosure relates to a method for transmitting a random access preamble in a transmitting sub-frame at a terminal device. The method comprises: creating a random access preamble such that it comprises a plurality of random access sequences; dividing the plurality of random access sequences into a number Nc of groups, each of groups including two or more random access sequences; performing code division multiplexing with respect to the groups of the plurality of random access sequences in a frequency domain, based on an orthogonal cover code selected for the terminal device from a pre-defined code set; and transforming signals after the code division multiplexing into the time domain. According to an aspect of the present disclosure, there are provided corresponding methods and devices.