NR-U Random Access via New RAR Format
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Solution Overview
Problem
The existing random access methods for New Radio (NR) systems in unlicensed frequency bands face challenges due to the need for Listen Before Talk (LBT) mechanisms, leading to increased random access delay and power consumption, as the current RAR window length is not suitable for distinguishing between different UE transmissions.
Innovation Solution
A new RAR format is introduced that includes information such as an LBT category and frame information, allowing for more precise channel access and reducing the complexity of implementation by using a unified RAR format for both licensed and unlicensed carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a new RAR format with LBT category and frame information is introduced for unlicensed carriers, then random access delay and power consumption are reduced, but device complexity and message format complexity increase
Solution Approach 1:
The patent introduces a new RAR format that includes LBT category information and frame information as additional parameters. This allows the system to distinguish between different UE transmissions on unlicensed carriers, enabling more efficient random access procedures that reduce delay and power consumption while managing the increased information requirements through structured parameter inclusion.
Solution Approach 2:
The solution segments the random access response by introducing different RAR formats tailored for different carrier types. The new format specifically for unlicensed carriers separates and organizes LBT-related information distinct from traditional random access parameters, allowing targeted optimization without affecting licensed carrier operations.
2Reliability
If Listen Before Talk mechanism is implemented on NR unlicensed frequency band, then fair coexistence with other systems is ensured, but random access delay and power consumption increase
Solution Approach 1:
The patent implements feedback mechanisms where the network device provides LBT category information and frame information to the UE through the new RAR format. This feedback enables the UE to adjust its channel access strategy, perform LBT more efficiently, and reduce power consumption while maintaining fair coexistence on unlicensed carriers.
Solution Approach 2:
The solution performs preliminary action by including LBT category information and frame information in advance within the RAR message. This allows the UE to prepare and execute LBT procedures more efficiently before actual data transmission, reducing overall power consumption while ensuring fair coexistence.
3Device complexity
If a unified RAR format is used for both licensed and unlicensed carriers, then implementation complexity is reduced, but the ability to provide specific unlicensed carrier information is limited
Solution Approach 1:
The patent achieves universality by designing a unified RAR format structure that can accommodate both licensed and unlicensed carriers. The format includes optional fields for LBT category information and frame information that are specifically relevant to unlicensed carriers, allowing the same basic structure to serve multiple carrier types while providing enhanced functionality where needed.
Data Source
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AI summary
Provided in embodiments of the present application are a wireless communication method, a terminal device, and a network device, which may achieve random access on NR unlicensed frequency bands. The wireless communication method comprises: a terminal device sends a first message during random access to a network device on an uplink licensed carrier or an uplink unlicensed carrier, the first message comprising a random access preamble; and the terminal device uses a first RAR format to detect a first RAR for the first message, the first RAR format targeting the unlicensed carrier.