Multicast Acknowledgment via Probabilistic Subcarrier Selection

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Solution Overview

Problem

Existing low-power and lossy network (LLN) technologies lack an efficient acknowledgment mechanism for multicast transmissions, leading to long delays due to the need for synchronized membership IDs and limited subcarrier availability, which is inefficient in dense networks.

Innovation Solution

The use of a probabilistic data structure, such as a Bloom filter, to select a subset of subcarriers for simultaneous acknowledgment transmissions, allowing acknowledgments from multiple nodes to collide on the same subcarriers, eliminating the need for synchronized membership IDs and increasing robustness to interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing LLN link technologies use traditional acknowledgment mechanisms for multicast transmissions, then reliability is maintained, but delay increases significantly due to lack of efficient acknowledgment mechanism

Engineering Contradiction:

Improveacknowledgment reliabilityVSAvoidacknowledgment delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The acknowledgment mechanism is segmented into individual node acknowledgments that are transmitted separately on different subcarriers rather than requiring centralized coordination. Each node independently selects and transmits its acknowledgment, eliminating the need for synchronized membership IDs and reducing delay while maintaining reliability through the segmented acknowledgment structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a frequency dimension by utilizing multiple subcarriers for acknowledgment transmissions. Instead of time-based sequential acknowledgments, nodes transmit acknowledgments simultaneously on different frequency subcarriers, transforming the problem from time-domain coordination to frequency-domain parallelism, thereby reducing delay while maintaining reliability

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Stability of the object's composition

If synchronized membership IDs are used for acknowledgment coordination, then acknowledgment order is maintained, but device complexity increases due to synchronization requirements

Engineering Contradiction:

Improveacknowledgment order stabilityVSAvoidsynchronization complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

Each node independently selects its own subcarrier for acknowledgment transmission based on local computation without requiring synchronization with other nodes. The probabilistic data structure enables self-service subcarrier selection, eliminating the need for centralized membership ID synchronization while maintaining stable acknowledgment delivery through the inherent structure of the probabilistic approach

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent changes the parameter space from synchronized membership IDs to probabilistic subcarrier selection. By transforming the coordination mechanism from identity-based synchronization to frequency-based probabilistic selection, the system maintains acknowledgment stability while reducing device complexity associated with synchronization protocols

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If limited subcarriers are allocated for acknowledgments, then frequency spectrum efficiency is improved, but productivity decreases due to acknowledgment collisions in dense networks

Engineering Contradiction:

Improvefrequency spectrum efficiencyVSAvoidacknowledgment throughput

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The subcarrier allocation becomes dynamic through probabilistic selection rather than static assignment. Each node dynamically selects subcarriers based on the probabilistic data structure, allowing the system to adapt to network conditions and node density. This dynamic approach increases productivity in dense networks by reducing collisions while maintaining frequency spectrum efficiency through flexible subcarrier utilization

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent allows for potential acknowledgment collisions by enabling more nodes to transmit on the same subcarriers simultaneously rather than strictly preventing all collisions. This partial action approach accepts some collisions as tolerable in exchange for allowing excessive nodes to participate in acknowledgment transmissions, thereby increasing overall productivity and acknowledgment throughput in dense networks

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS9350645B2Simultaneous acknowledgments for multicast packets

Publication Date: 2016.05.24 CISCO TECHNOLOGY INC

AI summary

In one embodiment, a multicast communication is received at a particular node of a plurality of nodes receiving the multicast communication in a network. The particular node selects a subset of subcarriers using a probabilistic data structure, such that each of the plurality of nodes selects a respective subset of subcarriers using the probabilistic data structure. The particular node transmits an acknowledgement of receipt of the multicast communication on the subset of subcarriers selected by the particular node. The transmission occurs simultaneously with transmissions of acknowledgements from the other of the plurality of nodes.