Bluetooth Slot Availability Masks for Accessory Collision Avoidance

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Solution Overview

Problem

In wireless personal area networks, especially those using Bluetooth connections, overlapping communication between accessory devices and a source device can lead to audio packet retransmissions, reducing available bandwidth and impacting performance due to uncoordinated timing of internal communication between accessory devices.

Innovation Solution

Implementing slot availability masks (SAMs) to schedule communication, where a source device coordinates time slots for internal communication among accessory devices, ensuring non-overlap with its own transmissions and receptions, and using guard periods to prevent collisions, thereby optimizing bandwidth usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If accessory devices communicate internally using the same radio frequency band as the source device, then wireless communication functionality is enabled, but communication collisions occur between source-device communication and accessory-device internal communication

Engineering Contradiction:

Improvewireless communication functionalityVSAvoidcommunication collision avoidance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The radio frequency band is segmented into distinct time slots: some slots are allocated for source-device communication while other slots are reserved for accessory-device internal communication. This temporal segmentation prevents collisions by ensuring that both communication types can coexist without overlapping in time, while still utilizing the same frequency band.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Communication between the source device and accessory devices follows a periodic slot structure, where time slots are regularly allocated for different communication purposes. This periodic scheduling ensures that accessory devices know when to communicate internally versus when to communicate with the source device, preventing collisions through predictable, repeating patterns.

Inventive Principle:

Principle #19Periodic action

2Device complexity

If accessory devices communicate internally without coordinated timing, then device complexity is reduced, but retransmission rates increase due to communication overlaps

Engineering Contradiction:

Improvecommunication coordination complexityVSAvoidbandwidth efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The slot availability mask is determined and distributed to accessory devices in advance, before actual communication occurs. This preliminary scheduling provides accessory devices with pre-coordinated timing information, allowing them to communicate internally during designated slots without requiring complex real-time coordination, thereby reducing both complexity and retransmissions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The slot availability mask provides feedback to accessory devices about when they can communicate internally versus when they should communicate with the source device. This feedback mechanism enables coordinated timing without requiring complex peer-to-peer coordination between accessory devices, reducing complexity while improving bandwidth efficiency through reduced collisions.

Inventive Principle:

Principle #23Feedback

3Reliability

If guard periods are added to prevent communication collisions, then communication reliability improves, but available bandwidth decreases due to unused time slots

Engineering Contradiction:

Improvecollision preventionVSAvoidbandwidth utilization

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Guard periods are applied selectively and minimally—only where absolutely necessary to prevent collisions between source-device transmissions and accessory-device internal communication. Rather than adding excessive guard periods throughout the entire communication schedule, the system uses the slot availability mask to place guard periods only at critical transition points, maintaining reliability while maximizing bandwidth utilization.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11405935B2Optimized Bluetooth scheduling for accessory devices

Publication Date: 2022.08.02 APPLE INC

AI summary

Communication between a source device and one or more pairs of accessory devices and between accessory devices within pairs of accessory devices is scheduled using slot availability masks (SAMs). A primary accessory device provides to the source device information about requirements for communication between the primary accessory device and a secondary accessory device. The source device determines a SAM map that specifies a periodic cycle of time slots, with time slots marked as available or unavailable for transmission and/or reception. The SAM map satisfies requirements to avoid collisions between communication between the source device and the accessory devices and communication between accessory devices within pairs of accessory devices. When multiple pairs of accessory devices establish connections with the source device, internal communication between accessory devices within pairs of accessory devices are aligned to use at least a common overlapping set of time slots.