5G Random Access Preamble Resource Indication via Network Signaling
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Solution Overview
Problem
In the context of 5G mobile communications, there is a challenge in how NR terminal devices perform non-contention based random access when both LTE and NR coexist, leading to issues such as resource wastage and increased complexity in detecting random access preambles.
Innovation Solution
The method involves a network device sending specific information to indicate either an NR uplink resource or a supplementary uplink resource for non-contention based random access, allowing the terminal device to configure and use the appropriate resource for sending a random access preamble, thereby preventing failures and reducing signaling overheads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the terminal device is configured with multiple random access resources (NR uplink resource and SUL resource) without clear indication, then the terminal device has more resource options for random access, but the terminal device cannot determine which resource to use, leading to random access failure
Solution Approach 1:
The network device performs preliminary action by pre-configuring multiple random access resources (NR uplink resource and SUL resource) with distinct identifiers, and before the terminal device attempts random access, sends indication information to specify which pre-configured resource should be used. This preliminary configuration and indication resolves the resource determination issue before the actual random access occurs.
Solution Approach 2:
Indication information acts as an intermediary between the network device and terminal device. It carries the identifier of the specific random access resource to be used, mediating the selection process by translating the network's resource allocation intent into a clear terminal device instruction, thus solving the resource determination problem.
2Reliability
If the terminal device repeatedly sends random access preamble on multiple resources to ensure successful access, then the probability of successful random access increases, but resource wastage increases
Solution Approach 1:
The network device provides feedback to the terminal device through indication information that specifies which random access resource should be used. This feedback mechanism eliminates the need for the terminal device to blindly retry on multiple resources, as the network directly guides the terminal to the appropriate resource, thereby maintaining high success rates while avoiding resource wastage from unnecessary retransmissions.
Solution Approach 2:
The network device performs preliminary action by pre-configuring multiple random access resources with distinct identifiers and sending indication information before the terminal device attempts random access. This preliminary specification of the exact resource to use prevents the terminal device from wasting resources on repeated attempts on incorrect resources, while ensuring reliable access through proper resource selection.
3Ease of operation
If the terminal device sends random access preamble on any configured resource without indication, then the terminal device can perform random access without additional signaling, but the network device complexity for detecting preambles on multiple resources increases
Solution Approach 1:
Indication information serves as an intermediary that carries the identifier of the specific random access resource to be used. By including this identifier in the indication information sent to the terminal device, the network device enables the terminal to select the correct resource without the network needing to perform complex blind detection across multiple resources, thus reducing network device complexity while maintaining ease of operation.
4Loss of information
If the network device configures multiple random access resources without sending indication information, then signaling overhead is reduced, but the terminal device cannot determine the appropriate resource for transmission
Solution Approach 1:
The network device performs preliminary action by pre-configuring multiple random access resources (NR uplink resource and SUL resource) with distinct identifiers during initial setup. This preliminary configuration allows the network to later send compact indication information containing only the resource identifier, rather than re-transmitting full resource configuration details, thus balancing signaling overhead with resource selection clarity.
Data Source
AI summary
A method for receiving a random access preamble includes: sending, by a network device, a broadcast message, where the broadcast message is used to configure an NR uplink resource and an SUL resource, and the NR uplink resource and the SUL resource are used to send a random access preamble; sending, by the network device, first indication information and second indication information to a terminal device, where the first indication information is used to indicate the NR uplink resource or the SUL resource, and second indication information is used to indicate a first random access preamble; and receiving, by the network device, the first random access preamble on the resource indicated by the first indication information.