Real-Time Network Coding with Feedback for Lossy Multicast

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Solution Overview

Problem

Transmitting real-time data streams simultaneously to multiple receivers over unreliable networks, such as wireless multicast, is challenging due to varying packet losses and the inefficiency of traditional ARQ mechanisms, which result in delays and inability to meet stringent real-time constraints for applications like live video streaming or industrial control.

Innovation Solution

A feedback-based real-time network coding method that prioritizes packets in the transmit queue based on deadlines and partial feedback from receivers, generating linear combinations that allow receivers to decode packets timely, even with incomplete feedback information, and maximizes the number of receivers that can decode packets immediately upon reception.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional ARQ mechanism is used for multicast, then reliable data delivery can be achieved, but transmission delays increase and real-time constraints cannot be met

Engineering Contradiction:

Improvereliable data deliveryVSAvoidtransmission delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system implements a feedback mechanism where receivers send NACKs (negative acknowledgments) for packets that were not received correctly. The transmitter uses this feedback information to generate targeted retransmissions, allowing it to retransmit only to specific receivers that need retransmission rather than waiting for all receivers to acknowledge, thus reducing delay while maintaining reliability

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The transmitter segments the multicast group into different receiver subsets based on their packet reception status. Each receiver is tracked individually with its own set of missing packets, allowing the system to send different retransmissions to different receivers simultaneously, reducing overall transmission delay while ensuring reliable delivery to all

Inventive Principle:

Principle #1Segmentation

2Reliability

If individual retransmission is sent to each receiver, then each receiver can receive needed packets, but other receivers stay idle and real-time constraints are violated

Engineering Contradiction:

Improvepacket delivery to each receiverVSAvoidtransmission efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The transmitter uses universal coding techniques where a single retransmission can serve multiple receivers simultaneously. By encoding retransmissions to contain information useful to multiple receivers at once (using their intersection of missing packets), the system eliminates idle time for receivers while maintaining efficient bandwidth utilization

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The transmitter proactively identifies receivers that are falling behind and predicts which packets they will need based on their reception patterns. This preliminary identification allows the system to prepare and send retransmissions before receivers actually request them, keeping all receivers actively engaged and meeting real-time constraints

Inventive Principle:

Principle #10Preliminary action

3Reliability

If ACKs are used for multicast feedback, then reliable delivery can be ensured, but additional delays occur and receiver coordination is required

Engineering Contradiction:

Improvedata delivery reliabilityVSAvoidfeedback delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Instead of using positive acknowledgments (ACKs) where receivers confirm receipt of packets, the system inverts the approach by using negative acknowledgments (NACKs) where receivers only signal when packets are missing. This inversion reduces feedback traffic and delays since receivers don't need to send feedback for every successfully received packet, only when something is wrong

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The system extracts only the essential feedback information (which packets are missing) from the complete acknowledgment process. By removing the redundant ACK transmissions for successfully received packets and keeping only the critical NACK information, the system reduces feedback delay and complexity while maintaining reliability

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS9602246B2Method and apparatus for feedback-based real-time network coding

Publication Date: 2017.03.21 UNIVERSIDADE DO PORTO

AI summary

The present subject-matter relates to transmitting a real-time data stream, namely simultaneously to multiple receivers over unreliable networks (e.g. wireless multicast), in a timely and reliable manner, in particular to a method, apparatus and computer program product for feedback-based real-time network coding. It is disclosed a computer-implemented method for a transmitting node, a receiving node, and an intermediate node of feedback-based real-time network coding from a transmitter and to one or more receivers, in particular comprising a linear combination of packets from the transmitter; determining whether the received linear combination of packets is linearly independent of previous linear combinations of packets; determining the validity of a priority level of the packets; determining validity of the deadline of the packets; determining whether a packet is to be removed from a transmit queue, and if determined removing it. There are also disclosed said transmitting, receiving, and intermediate nodes.