Base Station Uplink Grant Scheduling During Cell Handover
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Solution Overview
Problem
In wireless communications systems, cell handover leads to significant uplink data transmission latency, particularly affecting latency-sensitive services like voice services, as terminals can only trigger uplink scheduling after handover completion, resulting in prolonged data transmission delays.
Innovation Solution
A scheduling method where the target base station proactively sends an uplink grant to the terminal after sending a random access response and before receiving a handover complete command, allowing uplink scheduling to commence before cell handover is completed, thereby reducing latency. This includes sending multiple grants within a preset time frame and adjusting based on buffer status reports or service attributes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal waits for handover completion before triggering uplink scheduling, then the handover process is completed successfully, but the uplink data transmission latency increases significantly
Solution Approach 1:
The target base station performs preliminary uplink resource allocation by sending an uplink grant to the terminal during the handover process, before the handover is fully completed. This allows the terminal to prepare for uplink data transmission in advance, reducing the latency when handover finishes. The uplink grant is sent after receiving the random access request but before receiving the handover complete message, enabling the terminal to have resources ready immediately upon handover completion.
2Loss of time
If the target base station proactively sends uplink grant before handover completion, then the uplink transmission latency is reduced, but the risk of resource waste increases if handover fails
Solution Approach 1:
The target base station sends a preliminary uplink grant with a relatively small resource allocation (e.g., 1 RB) before handover completion. This partial allocation is sufficient to reduce latency but minimizes potential resource waste if handover fails. The grant is designed to be conservative in size, providing just enough resources for the terminal to maintain uplink synchronization and send data immediately after handover, without over-allocating resources that would be wasted upon handover failure.
3Productivity
If the terminal sends BSR after receiving uplink grant, then the base station can allocate appropriate resources, but the scheduling response time is delayed
Solution Approach 1:
The target base station performs preliminary resource allocation by sending an uplink grant to the terminal during the handover process, before the handover is fully completed. This allows the terminal to prepare for uplink data transmission in advance, reducing the latency when handover finishes. The uplink grant is sent after receiving the random access request but before receiving the handover complete message, enabling the terminal to have resources ready immediately upon handover completion.
Solution Approach 2:
The terminal sends a Buffer Status Report (BSR) to the base station after receiving the preliminary uplink grant, providing feedback about its data buffer status. The base station uses this feedback to adjust and optimize resource allocation in subsequent grants. This feedback mechanism ensures accurate resource allocation while minimizing delays, as the BSR is sent early in the process rather than waiting for handover completion.
Data Source
AI summary
Embodiments of the present disclosure provide a scheduling method and a base station. In a cell handover process, a target base station serving a target cell receives a random access request from a terminal, sends a random access response to the terminal according to the random access request, and proactively sends an uplink grant to the terminal after sending the random access response and prior to receiving a handover complete command from the terminal. By proactively sending the uplink grant, the target base station can perform uplink scheduling for UE before cell handover is completed, so as to reduce an uplink transmission latency caused by the cell handover.