USB Protocol Adaptation Layer Priority Data Flow Control
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Solution Overview
Problem
Existing USB communication systems face issues with higher priority data packets being delayed by lower priority packets, leading to increased latency, particularly in scenarios where bulk data transfers precede interrupt or isochronous data, which can result in unacceptable delays for time-sensitive data.
Innovation Solution
Implementing a protocol adaptation layer (PAL) that determines the data transfer type and priority of USB data, controlling the flow of data from the PAL to the network layer based on thresholds for outstanding transfer requests, thereby prioritizing higher priority packets and reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If USB data transfers are handled in first-come-first-served order without priority differentiation, then the system operation is simple, but high priority data packets experience increased latency when blocked by lower priority packets
Solution Approach 1:
The patent segments USB data transfers into different priority queues based on data transfer types (bulk, interrupt, isochronous). Each queue is managed separately with appropriate priority levels, allowing high-priority interrupt and isochronous transfers to be processed before lower-priority bulk transfers, thereby reducing latency for time-sensitive data without significantly increasing overall system complexity
Solution Approach 2:
The patent changes the parameter of data transfer handling from uniform processing to priority-based processing. By assigning different priority levels to different USB data transfer types and implementing threshold-based control for outstanding transfer requests, the system optimizes latency for high-priority data while maintaining manageable complexity through standardized priority assignment rules
2Productivity
If the number of outstanding transfer requests is increased to improve throughput, then data transmission efficiency improves, but latency for high priority packets increases due to more packets waiting in queue
Solution Approach 1:
The patent implements dynamic threshold adjustment for the number of outstanding transfer requests based on data transfer type priority. High-priority interrupt and isochronous transfers have lower thresholds to limit their queue depth and prevent blocking, while bulk transfers have higher thresholds to allow greater throughput. This dynamic differentiation enables the system to maintain high overall throughput while ensuring low latency for time-sensitive high-priority packets
Solution Approach 2:
The patent applies different quality characteristics to different data transfer types by assigning specific threshold values for outstanding transfer requests to each USB data transfer type. High-priority transfers receive local optimization with lower thresholds to minimize latency, while lower-priority bulk transfers tolerate higher thresholds for improved throughput, creating locally optimized performance characteristics for each data type
Data Source
AI summary
In an example, a method for transmitting data includes determining, at a Universal Serial Bus (USB) host, a USB data transfer type of USB data being transmitted from the host device to a USB device, and determining a priority of the USB data based on the determined USB data transfer type. The example method also includes controlling transfer of the USB data from a protocol adaptation layer (PAL) of the USB host to a network layer of the USB host based on the determined priority.