NTN Uplink Resource Selection Using 2-Step RACH and SR
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Solution Overview
Problem
The long transmission delays in satellite communication networks due to the high altitude of satellites result in significant delays, which are not suitable for meeting the quality of service requirements in 5G Non-Terrestrial Networks (NTN).
Innovation Solution
Implementing a method for uplink transmission that utilizes a 2-step random access channel (RACH) to send a buffer status report (BSR) on a physical uplink shared channel (PUSCH) during the 2-step RACH or on an uplink resource obtained through a scheduling request (SR), allowing for flexible resource allocation based on data volume, quality of service, and network instructions to minimize delay and resource occupation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional 4-step RACH is used for uplink transmission in NTN, then the procedure is simple and reliable, but the transmission delay is excessively long due to multiple round-trip times
Solution Approach 1:
The patent segments the traditional 4-step RACH procedure into a 2-step process by combining message 3 and message 4 into a single message 3 that contains both the uplink data and the contention resolution information. This segmentation reduces the number of round-trip times from four to two, significantly decreasing transmission delay while maintaining procedure simplicity.
Solution Approach 2:
The patent merges the uplink data transmission and contention resolution functions into a single message 3 transmission. The UE transmits both the uplink data payload and the contention resolution identifier in one message, eliminating the need for separate message 4 transmission and reducing overall transmission delay.
2Speed
If 2-step RACH is implemented to reduce delay, then transmission speed improves, but resource allocation becomes more complex and may occupy more network resources
Solution Approach 1:
The patent applies preliminary action by having the UE indicate the presence of uplink data in message 2 (random access response) before actually transmitting the data in message 3. This allows the network to prepare appropriate uplink resources in advance, simplifying the resource allocation process while enabling faster 2-step RACH transmission.
Solution Approach 2:
The patent implements dynamic resource allocation where the network adjusts uplink resource configuration based on real-time conditions. The gNodeB can dynamically determine whether to allocate resources for 2-step RACH or traditional SR-based transmission based on current network load and UE requirements, optimizing resource usage while maintaining transmission speed benefits.
3Loss of time
If SR-based uplink resource acquisition is used, then resource allocation is flexible and adaptive, but transmission delay increases due to additional signaling rounds
Solution Approach 1:
The patent makes the 2-step RACH procedure universal by enabling it to handle multiple scenarios: urgent data transmission requiring low delay, data transmission with available uplink resources, and data transmission without pre-configured resources. The UE can use 2-step RACH with or without prior SR configuration, making the mechanism versatile for different network conditions.
Solution Approach 2:
The patent introduces message 2 (random access response) as an intermediary that carries uplink resource configuration information. This intermediary allows the network to provide resource allocation details before the actual data transmission, enabling the UE to proceed with 2-step RACH while maintaining resource allocation flexibility and adaptability.
4Loss of time
If uplink data is transmitted during 2-step RACH, then transmission delay is reduced, but the probability of collision increases and resource occupation increases
Solution Approach 1:
The patent implements feedback mechanisms where the gNodeB receives the uplink data in message 3 and sends back a contention resolution message. This feedback loop allows the network to detect and resolve collisions by identifying the correct UE through the contention resolution identifier, maintaining reliability even when multiple UEs transmit simultaneously.
Solution Approach 2:
The patent replaces the mechanical collision avoidance approach (waiting for clear channel) with an information-based resolution system. Instead of physically avoiding collisions through sequential transmission, the system uses unique identifiers and feedback mechanisms to identify and resolve collisions logically, allowing parallel transmission attempts while maintaining reliability.
Data Source
AI summary
An uplink transmission method applied to a terminal includes: sending a buffer stat us report (BSR) during a 2-step random access channel (RACH) or sending the BSR on an uplink resource obtained through scheduling request (SR) according to resource configuration of the SR and resource configuration of the 2-step RACH.