Random Access Preamble Selection for Wireless Latency Reduction
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Solution Overview
Problem
In wireless communications, terminal devices cannot determine the type of random access to perform when both 4-step and 2-step random access preambles are configured by the network device, leading to inefficiencies in access latency and data transmission.
Innovation Solution
A method that allows terminal devices to select or determine a random access preamble from configured 2-step or 4-step random access preambles based on data amount thresholds, signal strength, and reference signal received power, enabling flexible selection of random access type for initial data transmission or retransmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the network device configures both 4-step and 2-step random access preambles, then the terminal device has more access options and can reduce access latency by selecting 2-step random access, but the terminal device cannot determine which type of random access to perform, leading to access inefficiency
Solution Approach 1:
The patent uses different physical layer signature characteristics (analogous to color changes) to differentiate between 2-step and 4-step random access preambles. Specifically, 2-step random access preambles are transmitted on physical uplink shared channel (PUSCH) resources while 4-step random access preambles are transmitted on physical random access channel (PRACH) resources. This physical layer distinction allows terminal devices to easily identify and select the appropriate random access type based on resource configuration, resolving the ambiguity problem while maintaining the latency benefits of 2-step random access.
2Device complexity
If the terminal device randomly selects a random access preamble type from configured preambles, then the terminal device can perform random access without determination logic, but the access process becomes inefficient due to random selection
Solution Approach 1:
The patent changes the parameter of physical layer transmission resources to enable deterministic selection. By associating 2-step random access preambles with PUSCH resources and 4-step random access preambles with PRACH resources, the terminal device can determine the appropriate random access type by checking which resource type is configured and available. This parameter-based differentiation eliminates random selection while keeping the terminal device logic simple, as it only needs to check resource configuration rather than implement complex determination algorithms.
3Loss of time
If the terminal device always performs 2-step random access, then the access latency is reduced, but the system cannot adapt to different data transmission scenarios requiring 4-step random access
Solution Approach 1:
The patent implements dynamic random access type selection by allowing the terminal device to adaptively choose between 2-step and 4-step random access based on real-time resource configuration and transmission requirements. The network device dynamically configures PUSCH and/or PRACH resources, and the terminal device dynamically selects the appropriate random access type based on this configuration. This dynamic approach enables the system to achieve low latency when 2-step random access is suitable while maintaining adaptability to switch to 4-step random access when required by the transmission scenario.
Data Source
AI summary
This application provides a random access method and a communications apparatus. The method includes: determining at least one random access preamble from at least one 2-step random access preamble, or determining one type of random access preamble from at least one 2-step random access preamble and at least one 4-step random access preamble, and performing random access by using the determined random access preamble. According to the application, the terminal device can determine a type of random access to be performed, thereby reducing an access latency.