Random Access Procedure Uplink Grant Size Mismatch Handling
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Solution Overview
Problem
In 5G New Radio (NR) networks, the mismatch between the size of the uplink grant provided during a Random Access procedure and the size of the MAC PDU stored in the terminal device's Msg3 buffer can cause issues, particularly when switching between Contention Free Random Access (CFRA) and Contention Based Random Access (CBRA) resources, leading to potential data loss and delays in handover procedures.
Innovation Solution
The terminal device determines whether the size of the uplink grant matches the size of the MAC PDU in the Msg3 buffer and adjusts subsequent transmissions accordingly, discarding unnecessary data units or adjusting the Buffer Status Report (BSR) and Power Headroom Report (PHR) to ensure compatibility, thereby avoiding data loss and completing the Random Access procedure successfully.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If beam switching procedure occurs in NR between CFRA and CBRA resources, then multi-beam operation flexibility is improved, but size mismatch between uplink grant and MAC PDU occurs
Solution Approach 1:
The patent implements dynamic beam switching between CFRA and CBRA resources, allowing the terminal to adaptively select different random access resources based on beam quality. The system dynamically adjusts the random access procedure by switching between contention-free and contention-based resources, which resolves the size mismatch issue by enabling flexible retransmission with corrected MAC PDU sizing.
Solution Approach 2:
The patent changes the parameter of random access resource type by switching between CFRA and CBRA modes. When beam switching occurs, the terminal can change the resource allocation parameters by selecting different random access procedures, which allows the network to reallocate uplink grants with correct size parameters matching the MAC PDU buffer.
2Adaptability or versatility
If uplink grant size differs from MAC PDU buffer size during beam switching, then resource allocation flexibility is improved, but data loss occurs
Solution Approach 1:
The patent implements a feedback mechanism where the terminal detects the size mismatch between the received uplink grant and the MAC PDU in the buffer. Upon detecting the mismatch, the terminal triggers a retransmission with corrected sizing, ensuring that the MAC PDU is properly sized and transmitted without data loss. This feedback loop prevents data loss by correcting the allocation error.
Solution Approach 2:
The patent prepares for potential size mismatches by implementing a retransmission mechanism. Before data loss can occur, the system has a prepared fallback procedure to retransmit the MAC PDU with correct sizing. This cushioning mechanism ensures that even if an initial allocation is incorrect, the data can be recovered and transmitted successfully in a subsequent attempt.
3Adaptability or versatility
If beam switching between CFRA and CBRA occurs, then handover capability is improved, but procedure delays occur
Solution Approach 1:
The patent performs preliminary beam quality measurements and assessments before initiating the random access procedure. By evaluating beam conditions in advance, the terminal can proactively select the most appropriate random access resources (CFRA or CBRA), avoiding unnecessary beam switching and associated delays during the actual handover process.
Solution Approach 2:
The patent enables the terminal to skip unnecessary beam switching steps by directly selecting the appropriate random access resources based on preliminary beam quality assessment. If the current beam is suitable, the terminal can proceed directly with the random access procedure without performing additional beam switching, thereby reducing handover delays while maintaining capability.
Data Source
AI summary
Embodiments of the present disclosure relate to methods, devices and computer readable mediums for random access procedure. The method comprises transmitting, at a terminal device, a random access request in a random access procedure to a network device; in response to receiving, in the random access procedure, from the network device an uplink grant for the terminal device, determining whether a first size of a first data unit indicated by the uplink grant matches a second size of a second data unit stored in a buffer of the terminal device; in response to determining that the first size mismatches the second size, determining a first part of the second data unit for subsequent transmissions.