Two-Step Random Access Procedure for Low Latency
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Solution Overview
Problem
Current contention-based random access procedures in communication systems, such as those in 5G networks, incur significant delay overhead due to the need for multiple independent steps between terminal devices and network devices, making them unsuitable for low-latency scenarios like Ultra-Reliable Low Latency Communication (URLLC).
Innovation Solution
A method is introduced to reduce the number of steps in the random access procedure by combining the first and third steps into a single step and the second and fourth steps into another single step, allowing information interaction to occur only once between the terminal device and the network device, using pre-configured resources and timing windows to optimize the random access process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a four-step contention-based random access procedure is used, then the random access process is comprehensive and reliable, but the delay overhead is large
Solution Approach 1:
The patent merges the four-step random access procedure into a two-step procedure by combining Message 1 and Message 3 into a single uplink message (Message A), and combining Message 2 and Message 4 into a single downlink message (Message B). This reduces the number of information interaction rounds from two to one, thereby reducing delay overhead while maintaining the essential functions of random access including contention detection and resolution
Solution Approach 2:
The patent uses pre-configured resources for Message A transmission, including pre-configured uplink shared channel resources and pre-configured random access preamble resources. This preliminary configuration eliminates the need for multiple negotiation steps and allows the terminal to directly transmit on predetermined resources, reducing access delay while maintaining reliability through pre-planned resource allocation
2Reliability
If four independent steps are used for information interaction, then the random access procedure is thorough, but the information interaction is performed twice causing large delay
Solution Approach 1:
The patent combines the uplink information transmission (original Message 1 and Message 3) into a single Message A that includes both the random access preamble and the uplink data or control information. Similarly, the downlink responses (original Message 2 and Message 4) are combined into a single Message B. This merging reduces information interaction from two rounds to one round, improving access efficiency while maintaining completeness
Solution Approach 2:
Message A serves multiple functions simultaneously: it acts as a random access preamble, carries uplink data, and requests uplink resources. Message B similarly serves as both a random access response and an uplink grant. This multi-functionality consolidates multiple separate communication steps into unified messages, reducing overall interaction time while maintaining all necessary communication functions
Data Source
AI summary
A random access method and network/terminal devices are provided, where a terminal device sends first information on a first resource, and sends second information on a second resource. The terminal device detects third information on one group of third pre-allocated resources in a first window, where a start position of the first window can be a position after a first time interval after the terminal device sends the second information. Alternatively, the start position of the first window can be a position after a first time unit after the first time interval after the terminal device sends the second information. Alternatively still, the start position of the first window can be a position after a first time unit in the one group of third pre-allocated resources after the first time interval after the terminal device sends the second information; and the terminal device receiving fourth information on a fourth resource.