Overcoming 10GBASE-T Test and Measurement Hurdles – Bring on the Streaming Video

By Randy White, Serial Applications Technical Marketing Manager Tektronix

As bandwidth-hungry applications become the norm in corporate settings, the pressure is on network managers to scale their networks to faster speeds. Applications like streaming video, VoIP, IPTV, video conferencing over Ethernet, virtualization technology, server consolidation and thin clients, among others are driving an industry move to 10 gigabit Ethernet, currently the fastest available.

Copper cabling is the medium of choice for network managers since it is convenient and cost effective. As speeds increase, companies want the ability to upgrade their existing infrastructure with plug-and-play simplicity. The IEEE 802.3an-2006 standard, or 10GBASE-T, is the industry response and allows a gradual upgrade from 1000BASE-T using autonegotiation to select the appropriate speed.

Now with corporate demand for more bandwidth about to hit hockey-stick growth curves, the industry is ramping up to deliver the required silicon and electronic components in volumes that will allow organizations to reliably pump 10 gigabits of data per second through 100 meters of unshielded twisted pair (UTP) CAT-6a cable.

Behind the scenes, accomplishing this feat is no small task. 10GBASE-T Ethernet introduces new challenges for design and test. Despite numerous improvements in UTP cable, every “trick in the book” of signal processing needed to be employed to achieve these data rates. To meet these challenges, the 802.3an-2006 standard uses some of the techniques listed below:

• Self-synchronizing scrambler - Provides clock transitions, and a statistically random power spectrum for EMI control, equalizer convergence, etc.
• DSQ 128 coding - The 10GBASE-T standard uses a synthetic 2-dimensional 128 DSQ (Double SQuare) constellation, which conveys 7 bits per symbol.
• LDPC (Low Density Parity Check) block codes – Block codes are one of two kinds of error correcting codes that can be used to approach the Shannon capacity of a channel.
• Tomlinson-Harashima Precoding (THP) - The 10GBASE-T standard calls for the use of THP, which is a scheme in which the equalizer for the channel is placed in the transmitter theoretically allowing the receiver to see “perfect” symbols. Training is accomplished during the initialization phase of the link.

With the big jump in speed and complexity, test and measurement takes on a vital role for the entire supply chain from chip makers to product developers to manufacturers. Tektronix has stepped up to fill this need with the recent introduction of XGbT test automation software and test fixtures. The new oscilloscope-based solution lowers cost by nearly 50 percent, removes complexity and improves usability compared to some 10GBASE-T test solutions that require the use of two or three separate instruments.

Dedicated 10GBASE-T test methodologies and solutions ensure reliable results for Transmitter, Receiver and Cable testing. At the same time, they enable fast validation cycles which are critical to ensuring a high level of repeatability across different testing environments and applications. Lastly automation capability speeds and simplifies testing so that products coming off assembly lines are fully compliant – and all those videos stream without a hitch.

Randy White is the serial applications technical marketing manager at Tektronix. Randy has worked with various aspects of test and measurement solutions at Tektronix over the past few years. He has given seminars on high-speed serial measurements and is actively involved in many working groups for high-speed serial standards. He holds a BSEE from Oregon State University in Corvallis, Oregon.