Layer 2 Relay Packet Return During UE Mobility Handover
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Solution Overview
Problem
In UE-to-Network relay scenarios, data packets intended for a remote UE may be stranded when the remote UE switches from a relay connection to a direct connection, leading to dropped transmissions due to the relay UE losing the connection to forward the data to the intended recipient.
Innovation Solution
The relay UE is configured to recognize and return data packets to the originating device with specific headers indicating the data is being routed back, allowing the originating device to resend the packets to the intended recipient using new MAC or adaptation headers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the remote UE uses a relay connection to communicate with the network, then coverage extension and connectivity are improved, but data packets may be stranded when the remote UE switches to direct connection
Solution Approach 1:
The relay UE is pre-configured with a return path to the originating device. When data packets need to be returned, the relay UE can directly transmit them back through the same or alternative relay path without requiring new routing setup, enabling rapid response to connection changes
Solution Approach 2:
The relay UE acts as an intermediary that not only forwards data packets from the originating device to the remote UE but also maintains the capability to return packets to the originating device. This dual-function intermediary role ensures continuous data flow management during mobility events
2Productivity
If the relay UE forwards data packets to the remote UE, then data transmission is enabled, but dropped transmissions occur when the remote UE moves out of relay coverage
Solution Approach 1:
The system implements feedback through status indicators that inform the originating device about the delivery status of data packets. When the relay UE determines it cannot forward packets (e.g., remote UE moved), it returns the packets with status information, enabling the originating device to retry transmission through appropriate paths
Solution Approach 2:
The patent changes the state parameter of data packets from 'forwarded' to 'returned' based on delivery conditions. This parameter change triggers different handling at the originating device, allowing dynamic adaptation of transmission strategies based on current network conditions and remote UE location
3Loss of information
If the relay UE returns data packets to the originating device, then data integrity is maintained, but additional signaling and processing overhead is introduced
Solution Approach 1:
The relay UE's transmission mechanism is designed to handle both forward transmission and return transmission of data packets using the same protocol and processing path. This multi-functionality reduces the need for separate complex handling logic for different transmission directions
Solution Approach 2:
When returning data packets, the relay UE transmits copies of the original packets along with status indicators. The originating device receives these copies and can process them through existing data handling routines, minimizing the need for new complex processing logic
Data Source
AI summary
A user equipment (UE) is configured to operate as a relay UE between a remote UE and a base station. The relay UE receives, from an originating device, a data packet for relay to a recipient device, determines that the relay of the data packet to the recipient device has failed and sends, to the originating device, a transmission including the data packet, wherein the transmission comprises an indication that the data packet is being returned to the originating device.