Modem Selective Discard for Duplicate TCP Packet Reduction
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Solution Overview
Problem
In wireless networks, unnecessary retransmissions of TCP packets occur due to premature timeouts caused by delayed or corrupted data, leading to increased traffic and inaccurate round trip time calculations.
Innovation Solution
A modem with a selective discard function that identifies and discards duplicate TCP packets before they are retransmitted, based on the receipt of RLC acknowledgments, thereby reducing superfluous traffic and retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TCP packets are retransmitted upon timeout, then data delivery reliability is improved, but unnecessary retransmissions increase traffic and distort round trip time measurements
Solution Approach 1:
The modem performs preliminary actions by storing RLC packet data and monitoring RLC acknowledgments before the TCP timeout occurs. When a TCP retransmission is triggered, the modem checks whether the corresponding RLC acknowledgment has already been received. If the RLC acknowledgment was received before the TCP timeout, the modem proactively discards the duplicate TCP packet, preventing unnecessary retransmission traffic while maintaining data delivery reliability.
2Reliability
If duplicate TCP packets are retransmitted, then data delivery reliability is improved, but round trip time calculations become inaccurate
Solution Approach 1:
The modem implements a feedback mechanism where it continuously monitors RLC acknowledgment status and uses this information to control TCP packet retransmission. The RLC acknowledgment serves as feedback indicating whether data has been successfully delivered. By feeding this information back to the TCP layer, the modem can prevent premature retransmissions that would otherwise corrupt round trip time measurements, thereby maintaining both reliability and measurement accuracy.
3Reliability
If all received data units are forwarded to the host processor, then data completeness is ensured, but unnecessary traffic increases between modem and host
Solution Approach 1:
The modem extracts and removes duplicate data units from the data stream before forwarding to the host processor. By implementing a duplicate detection mechanism that compares incoming RLC packets against stored data, the modem extracts only the necessary unique data units and discards duplicates. This reduces the quantity of traffic between modem and host while ensuring data completeness, as all unique data is forwarded and no necessary data is lost.
Data Source
AI summary
In one embodiment the modem has a network interface, application interface, processor, and memory. The network interface exchanges radio data with a network. The application (or host) interface exchanges application data with an application (or host) processor. The processor converts a unit of radio data to a corresponding unit of application data. The memory stores each unit of application data received by the modem. The processor is configured to execute a selective discard function to reduce traffic by determining if a newly arrived unit of application data is a duplicate of a stored unit of application. In the case that the newly arrived unit of application data is a duplicate of the stored unit of application data, the processor is further configured to selectively discard the duplicate unit of application data in dependence on whether an acknowledgement of the data has been already recognized by the processor.