BLE Isochronous Link Scheduling for High-Priority ACL Traffic
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Solution Overview
Problem
The Bluetooth Low Energy (BLE) protocol faces inefficiencies in handling isochronous and asynchronous data transactions due to the strict coupling of isochronous data packets with isochronous connection events and asynchronous data packets with asynchronous connection events, leading to substantial delays in control messages and complex scheduler designs, particularly in applications like True Wireless Stereo (TWS) earphones.
Innovation Solution
The method involves transmitting high priority asynchronous data payloads within isochronous connection events using the isochronous physical channel, replacing the payload of isochronous data streams, and encoding a priority indicator in the header to signal the receiving device, allowing for immediate handling of high priority ACL packets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high priority asynchronous data is transmitted using the asynchronous physical channel, then data transmission follows protocol requirements, but transmission latency increases due to waiting for the next ACL event
Solution Approach 1:
The patent merges asynchronous data transmission with isochronous connection events by allowing ACL packets to be transmitted during CIS events. The controller transmits a mix of CIS and ACL packets in the same connection event, enabling high priority asynchronous data to bypass the waiting period for the next ACL event while maintaining protocol compliance through proper packet formatting and identification.
2Stability of the object's composition
If isochronous data packets are strictly coupled with isochronous connection events, then data transmission timing is synchronized, but channel utilization efficiency decreases
Solution Approach 1:
The patent introduces dynamic packet type identification within connection events. The receiver device examines a packet type indicator field to determine whether each packet is a CIS packet or an ACL packet, allowing the system to dynamically adapt packet transmission types based on priority needs while maintaining synchronized connection event timing.
3Device complexity
If asynchronous data events occur at synchronized intervals, then connection management is simplified, but control message delays increase
Solution Approach 1:
The patent enables control messages to be transmitted in advance during isochronous connection events that occur more frequently than ACL events. By allowing ACL packets to be sent during CIS events, the system performs preliminary transmission of control data before the next scheduled ACL event, reducing delays for time-sensitive control messages.
Data Source
AI summary
A technique for reducing latency of high priority asynchronous traffic in the presence of isochronous traffic of a Bluetooth™ Low Energy communications system includes communicating an Asynchronous Connection Link (ACL) payload using a Connected Isochronous Stream (CIS) event. A bit in a header of a host-controller interface packet indicates to the controller that an ACL packet is a high priority ACL packet. The controller replaces the payload of a CIS event with the payload of the high priority ACL packet and the controller encodes a bit in a header of the CIS packet to signal to the receiving device that a corresponding CIS event contains an ACL payload. The controller transmits the CIS packet in the corresponding CIS event and the receiving device applies ACL handling of the CIS event in response to decoding the bit in the header of the CIS packet.