Adaptive Multicast FEC Grouping for Reliable WLAN Streaming

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Solution Overview

Problem

Wireless local area networks (WLANs) face challenges in supporting real-time multimedia streaming due to random and burst packet losses from multi-path fading and interference, as existing error correction schemes like FEC and ARQ are not adaptable to varying channel conditions, leading to inefficiencies in bandwidth usage and error recovery.

Innovation Solution

An adaptive method combining forward error correction (FEC) and automatic repeat request (ARQ) is introduced, where FEC packets are divided into adaptive multicast groups and an ARQ group, allowing clients to dynamically join or leave groups based on channel conditions, enabling flexible error correction and efficient bandwidth use.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If higher FEC is used to improve packet protection, then reliability is improved, but bandwidth overhead increases and network bandwidth is wasted

Engineering Contradiction:

Improvepacket protectionVSAvoidbandwidth overhead

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent implements dynamic FEC adjustment where the system continuously monitors channel conditions and adapts the FEC level accordingly. When channel conditions are good, lower FEC is used to save bandwidth; when conditions deteriorate, FEC is increased to maintain reliability. This dynamic adaptation resolves the contradiction by making FEC variable rather than static.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the FEC parameter (coding rate) based on measured channel quality indicators. By adjusting this key parameter in response to changing conditions, the system optimizes the trade-off between reliability and bandwidth efficiency, using more FEC only when necessary.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If ARQ is used for error correction, then packet recovery is improved, but round trip time delay increases

Engineering Contradiction:

Improvepacket recoveryVSAvoidround trip time delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements a hybrid approach where FEC provides partial error correction capability for immediate recovery, while ARQ serves as a backup for remaining errors. This partial use of ARQ reduces the frequency of ARQ operations, thereby reducing overall delay while maintaining packet recovery capability.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The system prepares FEC-coded packets in advance and transmits them proactively. This preliminary error correction capability allows many packets to be recovered without waiting for ARQ round trips, reducing the effective delay experienced by the application.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If ARQ is used in multicast applications, then error recovery is improved, but feedback explosion problem occurs

Engineering Contradiction:

Improveerror recoveryVSAvoidfeedback traffic

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent combines FEC and ARQ into a hybrid system where FEC handles the majority of error correction needs, reducing the number of ARQ feedback messages required. This merging of techniques allows the system to maintain error recovery capability while significantly reducing feedback traffic volume.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

FEC acts as an intermediary between the transmitter and receiver, providing a first line of defense against errors. This intermediary error correction mechanism reduces the burden on ARQ feedback, allowing fewer feedback messages to achieve the same overall reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Device complexity

If a single static FEC is used for all mobile devices, then system complexity is reduced, but it cannot satisfy the requirements of all devices with different channel conditions

Engineering Contradiction:

Improvesystem complexityVSAvoidchannel condition adaptation

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent segments the FEC service into multiple levels or modes (e.g., different coding rates). The system can select appropriate segments based on channel conditions, providing adaptability without requiring completely different systems for each device. This segmentation allows graduated adaptation to different conditions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system implements a universal FEC mechanism that can function in multiple modes (different coding rates, different block sizes). This multi-functional FEC system serves all devices with a single implementation framework, adapting to different channel conditions through parameter variation rather than requiring device-specific configurations.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8499212B2Method and apparatus for adaptive forward error correction with merged automatic repeat request for reliable multicast in wireless local area networks

Publication Date: 2013.07.30 INTERDIGITAL CE PATENT HOLDINGS SAS

AI summary

A method and apparatus are described for increasing multicasting reliability, including receiving content and a first layer of a plurality of a forward error correction coded packets from a first multicast group and joining an additional multicast group in order to receive one of additional layers of forward error correction coded packets and the content along with a further additional layer of the plurality of forward error correction coded packets.