PRACH Resource Set Selection for NR-U Random Access
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Solution Overview
Problem
In the context of New Radio (NR) systems deploying networks on unlicensed spectra, there is a challenge in enabling terminal devices to access networks efficiently through NR-U carriers, particularly in scenarios requiring independent network deployments and dual connectivity, where channel sensing and random access procedures need to be managed effectively to avoid interference.
Innovation Solution
The solution involves a communication method where a terminal device acquires and determines a target Physical Random Access Channel (PRACH) resource set, comprising at least one first and one second PRACH resource set, to facilitate PRACH transmission on an unlicensed spectrum. This includes receiving indication information from a network device to configure the PRACH resource sets, allowing the terminal device to select appropriate resources for random access procedures, ensuring channel availability and minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a terminal device performs channel sensing on an unlicensed spectrum before sending a signal, then the device can avoid interfering with other transmissions, but the device cannot send any signal when the channel is busy, reducing network access efficiency
Solution Approach 1:
The PRACH resources are segmented into multiple resource sets (first PRACH resource set and second PRACH resource set) with different characteristics. The terminal device can select from multiple segmented resources rather than a single resource, allowing it to find an available resource even when some are busy, thus maintaining reliability while improving access efficiency.
2Adaptability or versatility
If the network deploys independent NR-U carriers on unlicensed spectrum, then the network can utilize additional spectrum resources, but the terminal device faces challenges in accessing the network due to LBT requirements
Solution Approach 1:
The network device performs preliminary actions by configuring multiple PRACH resource sets with different time-frequency resources and LBT parameters before the terminal device needs to access the network. This preliminary configuration enables the terminal device to have multiple options available, making access easier despite LBT requirements.
Solution Approach 2:
The multiple PRACH resource sets act as intermediaries between the terminal device and the unlicensed spectrum. By providing multiple intermediate resources with different characteristics, the system facilitates easier terminal access while maintaining proper LBT compliance on the unlicensed spectrum.
3Ease of operation
If the terminal device selects PRACH resources from a single resource set, then the resource selection process is simple, but the device may fail to access the network when all resources in that set are occupied
Solution Approach 1:
The system introduces dynamics by allowing the terminal device to adaptively select from multiple PRACH resource sets based on current channel conditions and LBT outcomes. The terminal can dynamically switch between different resource sets (first and second sets) depending on which resources are available, maintaining both operational simplicity and high access reliability.
Data Source
AI summary
The embodiments of the present application relate to a communication method, a terminal deice, and a network device. The method comprises: a terminal device acquires a target physical random access channel (PRACH) resource set, the target PRACH resource set comprising at least one resource set between a first PRACH resource set and a second PRACH resource set, the first PRACH resource set and the second PRACH resource set being different by at least one resource; and the terminal device determines a target PRACH resource in the target PRACH resource set, the target PRACH resource being used for PRACH transmission in a random access process. The communication method, the terminal device, and the network device of the embodiments of the present application allow the terminal device to access a network via an NR-U carrier.