Inter-RAT Handover Control Using Empty GRE Packets
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Solution Overview
Problem
During inter-RAT handover, particularly from 3GPP to HRPD networks, there is a risk of out-of-order packet delivery due to delays in packet forwarding, which existing procedures fail to address effectively.
Innovation Solution
The use of an empty GRE packet with sequence numbers is employed to indicate the end of forwarded data packets, ensuring that the target gateway delivers packets in-order by switching to direct data packets from the home network gateway once the empty GRE packet with the expected sequence number is received.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If packet forwarding is used during inter-RAT handover, then packet loss is reduced, but out-of-order packet delivery occurs
Solution Approach 1:
An empty GRE packet serves as an intermediary marker between the source gateway and target gateway to delimit the forwarded packets. This mediator enables the target gateway to distinguish between forwarded packets and direct packets, allowing it to deliver forwarded packets first and then direct packets, thereby maintaining in-order delivery while utilizing packet forwarding to reduce packet loss during inter-RAT handover
Solution Approach 2:
The sequence number field is extracted from the GRE packet header to serve as a standalone marker indicating the end of forwarded packets. By taking out this critical identification information and placing it in the empty GRE packet, the system enables the target gateway to accurately identify where forwarded packets end and direct packets begin, ensuring proper packet ordering without affecting the forwarding mechanism
2Stability of the object's composition
If sequence numbers are added to all data packets, then packet ordering is ensured, but packet overhead increases
Solution Approach 1:
The packet stream is segmented into two distinct types: forwarded packets (with sequence numbers for ordering) and direct packets (without sequence numbers to reduce overhead). The empty GRE packet acts as a delimiter between these segments, allowing the target gateway to process each segment appropriately while minimizing the total overhead by not adding sequence numbers to all packets uniformly
Data Source
AI summary
An empty GRE packet along with a sequence number provides in-order delivery of data packets for a session to a UE during inter-RAT handover. In particular, an empty GRE packet sent from a source gateway in a source RAN (Radio Access Network) to a target gateway in a target RAN includes a sequence number to indicate to the target gateway the end of forwarded data packets from the source gateway. The target gateway sends data packets received from the source gateway to the UE until the empty GRE packet with the expected sequence number is received. Upon receipt of the empty GRE packet containing the expected sequence number, the target gateway begins sending data packets received directly from a home network gateway to the UE.