Inter-RAT Handover PDU to IP Conversion for 3G LTE
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Solution Overview
Problem
The challenge of inter-RAT handover between legacy 3G and LTE systems is complicated due to differences in user plane data processing procedures and formats, leading to issues with packet forwarding and potential data loss during handovers.
Innovation Solution
Implementing an IP packet forwarding strategy that converts buffered protocol data units (PDUs) into IP packets before handover, allowing for seamless transition between networks without context transfer and minimizing packet loss by retransmitting only unacknowledged packets in the target network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If PDU level forwarding is used for inter-RAT handover, then legacy system compatibility is maintained, but packet processing fails due to format differences between 3G and LTE systems
Solution Approach 1:
The patent changes the data format parameter from PDU level (3G format) to IP packet level (LTE format). The source network converts buffered PDUs into IP packets before forwarding, transforming the data structure to match the target network's expected format, thereby enabling successful packet processing in LTE system while maintaining compatibility with legacy 3G infrastructure through the conversion process
2Reliability
If all buffered packets are retransmitted in target network, then data loss is avoided, but radio resource usage increases due to duplication transmission
Solution Approach 1:
The patent implements a feedback mechanism where the user equipment sends an acknowledgment list indicating which packets have been successfully received. The target network uses this feedback information to determine which packets need retransmission, retransmitting only the unacknowledged packets rather than all buffered packets, thereby avoiding duplicate transmission of already received data and optimizing radio resource utilization
3Measurement precision
If context transfer is performed during handover, then processing accuracy is improved, but handover complexity and time increase
Solution Approach 1:
The patent extracts and removes the context transfer step from the handover process. Instead of transferring ROHC context and other processing state information between networks, the system forwards IP packets directly without context transfer. This extraction simplifies the handover procedure while maintaining processing accuracy through direct IP packet forwarding and acknowledgment-based retransmission
Data Source
AI summary
The invention provides a method for enabling inter-RAT handover in a communication system comprising a first network utilizing a first radio access technology and a second network utilizing a second radio access technology. When a user equipment moves from the first network into the second network and a handover is to be made, processing protocol data units (PDUs) in non-IP packet format and buffered in the first network or in the user equipment into IP packets in response to a handover confirmation (HOcfm) sent by the second network; forwarding the processed IP packets from the first network to the second network if the PDUs are buffered in the first network; and retransmitting the processed IP packets after the user equipment is switched to the second network. An user equipment and a communication system corresponding with the method of the invention are also provided.