Grant-Free Handover via Pre-Configured CTU Resources
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Solution Overview
Problem
In LTE systems, the existing uplink scheduling request mechanism for terminal devices leads to high signaling overheads and transmission delays, especially in scenarios with heavy load or poor channel quality, and poses challenges during handovers for grant-free transmission in machine-type communication services.
Innovation Solution
A handover method is introduced where a network device requests and instructs a terminal device to switch from one base station to another for grant-free transmission, using handover request and instruction messages to facilitate seamless resource allocation on contention transmission units (CTUs), reducing blind detection and signaling overheads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the uplink scheduling request mechanism is used in LTE systems, then terminal devices can request uplink resources from base stations, but signaling overheads increase and transmission delays occur
Solution Approach 1:
The patent applies preliminary action by pre-configuring grant-free transmission resources and parameters before actual data transmission is needed. The network device pre-allocates contention transmission units (CTUs) and configures transmission parameters in advance, so when MTC services need to transmit data, they can immediately use the pre-configured resources without waiting for scheduling requests and grants, thereby reducing transmission delay while maintaining reliable resource allocation.
2Productivity
If grant-free transmission is implemented to reduce signaling overheads, then transmission efficiency improves, but challenges arise during handover between base stations
Solution Approach 1:
The patent applies preliminary action in handover by pre-configuring multiple target base station information and their corresponding CTU resources before handover is needed. When handover occurs, the terminal device can immediately switch to the pre-configured target base station and use the pre-allocated CTU resources, avoiding the complexity of real-time resource negotiation and reducing handover interruption time.
Solution Approach 2:
The patent uses the network device as an intermediary to manage the handover process. The network device coordinates the handover by selecting target base stations, allocating CTU resources, and providing handover instruction messages to terminal devices. This intermediary management simplifies the handover complexity by centralizing the decision-making and resource allocation process.
3Loss of information
If terminal devices transmit on pre-configured CTU resources without scheduling requests, then signaling overheads are reduced, but resource conflicts may occur under heavy load
Solution Approach 1:
The patent applies segmentation by dividing the grant-free transmission resources into multiple contention transmission units (CTUs) with different configurations. The network device can allocate different CTU resources to different terminal devices or service types, segmenting the resource space to reduce conflicts. When resource conflicts occur, the system can segment the resolution process by identifying specific conflicting CTUs and reallocating resources in a targeted manner.
Solution Approach 2:
The patent uses parameter changes to adapt grant-free transmission to varying load conditions. The network device can dynamically adjust CTU parameters such as time-frequency resources, coding schemes, and power levels based on current network load and channel conditions. This allows the system to maintain transmission reliability under heavy load by changing parameters to reduce conflicts, while still avoiding scheduling requests to maintain low signaling overhead.
Data Source
AI summary
The present disclosure provides a handover method for grant-free transmission, a terminal device, and a network device. The handover method includes: sending, by a first network device, a handover request message to a second network device to request to hand over a terminal device from the first network device to the second network device to perform grant-free transmission; receiving, by the first network device, a handover request acknowledgement message sent by the second network device to acknowledge handing over the terminal device from the first network device to the second network device to perform grant-free transmission; and sending, by the first network device, a handover instruction message to the terminal device to instruct the terminal device to transmit a signal to the second network device on a CTU resource in a grant-free transmission mode.