USB Extension Buffer Management for Distance Limitations
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Solution Overview
Problem
The existing USB specifications limit SuperSpeed connections to a maximum cable length of 3 meters, restricting the distance between a host device and a USB device, necessitating new techniques to extend USB communication over longer distances while maintaining compliance with USB standards.
Innovation Solution
The implementation of a downstream facing port device (DFP) and an upstream facing port device (UFP) that use a non-USB extension medium to manage communication, where the DFP determines the number of data packets to request from a USB device based on available buffer space, generates synthetic data request packets, and transmits data packets over the extension medium to compensate for latency and extend USB communication beyond the standard distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a regular copper cable is used for a SuperSpeed connection, then the connection complies with USB specifications, but the cable length is limited to at most 3 meters
Solution Approach 1:
The patent introduces extension devices (DFP and UFP) as intermediaries between the host and USB device. These devices communicate over a non-USB extension medium (such as Ethernet or other communication networks) while maintaining USB protocol compatibility. The DFP receives data requests from the UFP via the extension medium, manages buffer space, and coordinates data transfers, effectively mediating the connection between USB devices over distances exceeding the standard 3-meter cable limitation.
2Length of stationary object
If the cable length is extended beyond 3 meters, then the distance between host and USB device increases, but the SuperSpeed connection cannot be properly supported
Solution Approach 1:
The patent segments the USB connection into multiple components: the host device, the UFP (upstream facing port), the extension medium, the DFP (downstream facing port), and the USB device. This segmentation allows each component to operate independently at its optimal speed and protocol, with the extension medium using appropriate communication protocols for long-distance transmission while the USB segments maintain SuperSpeed signaling where applicable.
3Length of stationary object
If extension devices are introduced to extend USB communication, then the distance between host and USB device increases, but the complexity of the system increases
Solution Approach 1:
The extension devices (DFP and UFP) are designed to be multi-functional, serving both as USB protocol endpoints and as network communication interfaces. They can operate in different modes (USB mode, extension mode) and support multiple protocols, reducing the need for dedicated hardware for each function and thereby managing system complexity while enabling extended communication distances.
Data Source
AI summary
A method of managing communication between a host device and a USB device via a non-USB extension medium is provided. A downstream facing port device (DFP device) receives a data request packet that includes a first buffer count from an upstream facing port device (UFP device) via the non-USB extension medium. The DFP device determines a number of data packets to request from the USB device based on a free buffer count tracked by the DFP device that represents an amount of buffer space available on the UFP device. The DFP device generates a synthetic data request packet that includes a second buffer count based on the determined number of data packets to request from the USB device. The DFP device receives a set of data packets from the USB device responsive to the synthetic data request packet, and transmits the set of data packets to the UFP device.