In part two of this blog series, I am going to discuss the challenges of multiplexing PC Video and USB 2.0 wirelessly over 802.11n. The PC-on-TV architecture, shown below, illustrates the complete system.  The PC video and audio is presented to the user’s TV or monitor without disturbing any of the existing A/V sources (e.g. cable-TV source, DVD, etc.) connected to the TV.  The PC DVI or HDMI output and USB connection is connected to the PC Extender, which then transmits both video and USB 2.0 wirelessly over 802.11n.  The TV or Monitor Extender receives the transmission and decodes the video and USB 2.0 sending DVI or HDMI to a remote TV or monitor and enabling connection of any USB 2.0 device. 

PC-on-TV Architecture

Let’s examine the PC-on-TV architecture and the three challenges of combining high definition real time PC video with latency sensitive USB 2.0 and transmitting it wirelessly; these challenges are transmitting video, transmitting USB 2.0 and multiplexing video and USB together.   

Challenge one: When transmitting video, maintaining video quality within the bandwidth limitation is critical.  Video quality is of high importance since artifacts are magnified on large TVs or monitors and may be unacceptable.  As for bandwidth, it determines if a semi compressed, compressed video, or uncompressed video can be utilized.  Uncompressed HD video can take Gigabits of bandwidth for transmission.  Over Cat 5 cable, this is possible but certainly not wirelessly.  Furthermore, for a typical home to have reliable connectivity, the wireless bandwidth is limited to 20Mbps.   

Challenge two: The next challenge is transmitting USB 2.0.  USB-IF specifies a distance limitation of five meters (16.4 feet) for USB.  In the PC-on-TV architecture, the distance would easily exceed five meters.   

Challenge three: The third challenge is devising a way to multiplex video and USB 2.0.  The USB traffic that occurs depends on the type of device connected to the host.  For example, interrupt devices such as mouse, keyboard, game controllers are low bandwidth but bulk and ISO devices can require larger bandwidth.  Enough bandwidth had to be allocated for all types of USB devices while not affecting the video quality.  Furthermore, latency and buffering had to be balanced which inherently are diametrically opposed.  Too much buffering results in long latency and poor interactive response, too little buffering means the ability for error correction is lost.  Low system latency is critical and ideally is 50 milliseconds so the end user does not notice a delay.   

In part three of the blog series, I’ll discuss the solutions to these three challenges and how Icron was able to overcome them.  In the mean time, please contact info@icron.com for more information!

Tags: extremeusb, KVM products, PC extension, video + usb, Wireless PC

This entry was posted on Thursday, September 2nd, 2010 at 20:38 and is filed under Product How To . You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.