USB 3.0 Link Layer Timer Adjustment to Extend Distance

Abstract

Methods and devices for transmitting SuperSpeed information between a host device and a USB device via an extension medium are provided. Link partner relationships are established between the host device and an upstream facing port device, between the USB device and a downstream facing port device, and between the upstream facing port device and the downstream facing port device. While the link partner relationship between the upstream facing port device and the downstream facing port device is substantially compliant to the USB 3.0 Specification, the link partner relationship may use a configurable link layer acknowledgement timer to compensate for delays in transmission over the extension medium.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . A USB extension device, comprising:
 a USB SuperSpeed physical layer interface;   a remote interface; and   a protocol engine configured to:
 receive a header packet from a device via the USB SuperSpeed physical layer interface; 
 transmit a header packet acknowledgement to the device via the USB SuperSpeed physical layer interface to be received at a time less than a standard link layer acknowledgement time after the header packet was transmitted by the device; 
 transmit the header packet received from the device via the USB SuperSpeed physical layer interface to a second USB extension device via an extension medium accessible via the remote interface; 
 monitor an amount of time elapsed after transmitting the header packet to the second USB extension device; 
 receive a header packet acknowledgement from the second USB extension device; 
 compare the monitored amount of time to the standard link layer acknowledgement time; and 
 not causing a transition to a recovery state for a link layer connection between the USB extension device and the second USB extension device via the extension medium and not causing a transition to a recovery state for a link layer connection between the USB extension device and the device via the USB SuperSpeed physical layer interface in response to determining that the monitored amount of time is greater than the standard link layer acknowledgement time. 
   
     
     
         2 . The device of  claim 1 , wherein the standard link layer acknowledgement time is a PENDING_HP_TIMER. 
     
     
         3 . The device of  claim 1 , wherein the extension medium includes fiber optic cable, coaxial cable, or wireless transmission. 
     
     
         4 . The device of  claim 1 , wherein the extension medium includes a packet-based network, an Ethernet layer  2  network, or an Ethernet layer  3  network. 
     
     
         5 . The device of  claim 1 , wherein the USB physical layer interface includes an upstream facing port or a downstream facing port. 
     
     
         6 . A USB extension device, comprising:
 a USB SuperSpeed physical layer interface;   a remote interface; and   a protocol engine configured to:
 transmit a link layer header packet received from the device via the USB SuperSpeed physical layer interface to the second USB extension device via an extension medium accessible via the remote interface; and 
 receive a link layer header packet acknowledgement from the second USB extension device; 
   wherein the link layer header packet acknowledgement is received at an elapsed time after the link layer header packet transmission that is greater than a standard link layer acknowledgement timer without causing the second link partner relationship or the first link partner relationship to transition to recovery.   
     
     
         7 . The device of  claim 6 , wherein the standard link layer acknowledgement timer is three microseconds. 
     
     
         8 . The device of  claim 6 , wherein the extension medium includes fiber optic cable, coaxial cable, or wireless transmission. 
     
     
         9 . The device of  claim 6 , wherein the extension medium includes a packet-based network, an Ethernet layer  2  network, or an Ethernet layer  3  network. 
     
     
         10 . The device of  claim 6 , wherein the USB physical layer interface includes an upstream facing port or a downstream facing port. 
     
     
         11 . A method, comprising:
 receiving, by a Universal Serial Bus (USB) extension device, a header packet from a device via a USB SuperSpeed physical layer interface;   transmitting, by the USB extension device, a header packet acknowledgement to the device via the USB SuperSpeed physical layer interface to be received at a time less than a standard link layer acknowledgement time after the header packet was transmitted by the device;   transmitting the header packet received from the device via the USB SuperSpeed physical layer interface to a second USB extension device via an extension medium accessible via a remote interface;   monitoring an amount of time elapsed after transmitting the header packet to the second USB extension device;   receiving a header packet acknowledgement from the second USB extension device; and   not causing a transition to a recovery state for a link layer connection between the USB extension device and the second USB extension device via the extension medium and not causing a transition to a recovery state for a link layer connection between the USB extension device and the device via the USB SuperSpeed physical layer interface in response to determining that the monitored amount of time is greater than the standard link layer acknowledgement time.   
     
     
         12 . The method of  claim 11 , wherein the standard link layer acknowledgement time is three microseconds. 
     
     
         13 . The method of  claim 11 , wherein the extension medium includes fiber optic cable, coaxial cable, or wireless transmission. 
     
     
         14 . The method of  claim 11 , wherein the extension medium includes a packet-based network, an Ethernet layer  2  network, or an Ethernet layer  3  network. 
     
     
         15 . The method of  claim 11 , wherein the USB SuperSpeed physical layer interface includes an upstream facing port or a downstream facing port.