TCP Sender Handover Rate Control via ACK Sequence Verification
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Solution Overview
Problem
In mobile communication systems, data transmission rates are decreased due to congestion control triggered by retransmission timeout events during upward vertical handover in overlay networks, even when packet loss caused by channel congestion does not occur, leading to potential overload on new networks.
Innovation Solution
A data transmission rate control method that involves a TCP sender checking for retransmission timeouts, storing sequence numbers, and performing congestion control only if ACK signals corresponding to those numbers are received, allowing for optimal initial slow start limit and retransmission timeout settings in the new network during handover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If congestion control is performed upon retransmission timeout event during upward vertical handover, then packet loss is addressed, but data transmission rate is greatly decreased
Solution Approach 1:
The patent changes the parameter of congestion control activation by introducing a flag that distinguishes between retransmission timeouts caused by actual congestion versus those caused by RTT changes during handover. This allows the system to maintain appropriate congestion control only when necessary, preventing unnecessary rate reduction during handover transitions.
Solution Approach 2:
The patent implements feedback mechanisms by monitoring the relationship between transmitted packet sequence numbers and acknowledged sequence numbers. When the difference indicates handover rather than congestion, the feedback loop prevents erroneous congestion control activation, thereby maintaining data transmission rate while still addressing actual packet loss issues.
2Reliability
If conventional TCP congestion control is applied during upward vertical handover, then retransmission timeout events are handled, but unnecessary congestion control is performed due to RTT changes
Solution Approach 1:
The patent segments the congestion control mechanism into two independent parts: a flag that identifies handover conditions and a separate congestion control activation logic. This segmentation allows the system to distinguish between handover-induced retransmission timeouts and genuine congestion events, preventing unnecessary congestion control while maintaining appropriate handling of actual packet loss.
Solution Approach 2:
The patent introduces an intermediary flag variable that mediates between the retransmission timeout detection and the congestion control activation. This intermediary element processes the difference between transmitted and acknowledged sequence numbers to determine whether handover has occurred, thereby controlling whether congestion control should be activated based on this intermediate determination.
3Object-affected harmful factors
If slow start phase mode is used for new network during upward vertical handover, then network overload is prevented, but data transmission rate is limited
Solution Approach 1:
The patent applies preliminary action by setting the slow start flag before the actual data transmission begins on the new network. This preliminary determination, based on the handover condition detection, allows the system to pre-configure appropriate transmission parameters that prevent network overload while enabling faster data transmission rates compared to conventional slow start procedures.
Data Source
AI summary
Provided is a data transmission rate control method in upward vertical handover in an overlay network environment, including: a TCP (Transmission Control Protocol) sender checking whether or not a retransmission timeout event occurs while communicating with a TCP receiver through a dual interface in a TCP scheme; the TCP sender storing a sequence number of a packet having the largest sequence number among transmitting packets, and after that, performing congestion control if the retransmission timeout event occurs; the TCP sender checking whether or not ACK signal corresponding to a sequence number which is equal to or smaller than the stored sequence number is received after the TCP sender performs the congestion control; and the TCP sender determining to execute upward vertical handover if the ACK signal is received.