i/oZONE Products for the week of October 20, 2003
Quellan Says . . .
Gigabit Backplane Breakthrough? -- Part 1 of a 2-part
review of Quellan's Gigabit Noise Canceller
Live demonstration shows BER performance improvement by a
factor of 1,000,000 in conventional backplanes is possible at 5 Gbit/s speeds
Quellan Inc, a leading developer of Gigahertz spectrum Analog Chips, demonstrated the ability to "cancel" unwanted "crosstalk" noise in a multi-Gigabit backplane at the IMAPS Conference. This cancellation technology enables existing noise impaired equalized backplanes to go from passing 100,000 bits before an error occurred to a throughput of 10 trillion bits before an error occurred -- a Bit Error Rate improvement of 1,000,000. This translates into a throughput improvement from 1.25Gbps to 7Gbps while sustaining a BER of 10e-17.
Similar in principle to the technology used in consumer "Noise Canceling Headphones", Quellan's technology cancels noise at frequencies 1,000,000 times higher - in the Gigahertz range. As system and network traffic bandwidth increases, the aging backplanes in the field- those passive chassis that carry signals between cards - become increasingly unable to transport signals from card to card. The noise that is coupled from pin to pin on the connectors increases with frequency and at the rates required, render equipment inoperable. Since this equipment has been installed for years, it cannot be torn down to be upgraded. Quellan's chips allow the infrastructure to stay in place and by incorporating chips on new switch cards, speeds of 5 and 6.25 Gigabits per second can be achieved on legacy backplanes. IT managers benefit by leaving their network intact and OEMs benefit by being able to offer higher performance capabilities into existing systems, which greatly reduces development cost and time to market.
"Crosstalk is now a significant barrier to upgrading all types of network, compute and broadcast equipment" said Tony Stelliga, CEO of Quellan. "In fact, we have seen systems where crosstalk at desired data rates exceeds the signal level. By canceling the undesirable 'aggressor' signals, we are able to allow the 'victim' signal to propagate freely down the backplane, largely unaffected. The use of our chips on new line cards, then, allows in-field system upgrades in the compute, telecom and enterprise and broadcast markets."
"Quellan's demonstration today clearly showcases a valuable technology to the communications marketplace," said Mike Noonen, GM of the Network Technology Group at National Semiconductor. "Quellan has a approached this imminent problem from the system level and have developed a winning technology to address it."
Quellan ran the demonstration on their CSP Real Time or "CSP R/T"
system that is now available to OEMs to perform evaluation of Quellan's
Technology and to better characterize their backplanes. The CSP R/T provides
single and dual channel cancellation and a Feed Forward Equalizer for high
performance cancellation and system analysis using a range of Pods that
are available for different connector sets.
analogZONE Says . . .
Quellan's release of it first product comes at an interesting time. While the recession has slowed the growth in demand for bandwidth a bit, it has continued to grow at a reasonably steady pace throughout the recession. It's now finally beginning to nibble at the edges of the surplus capacity that lurked within many enterprise and carrier networks. And with these first signs of growth in the networking market, manufacturers are contemplating what it's going to take to capture whatever revenues they can. While the pundits are still arguing about whether customers will be more interested in buying new equipment or simply upgrading what they have to meet their growing capacity needs, my money's on whatever upgrade technology can help them squeeze the last nickel out of whatever CAPEX they have at hand.
As we've discussed before, one of the biggest bottlenecks to upgrading the capacity of older equipment is the backplane, which simply runs out of useful bandwidth when you get much above the 622 Mbit/s they were originally designed for. Over the past year, I've looked at quite a few innovative silicon solutions that mine bandwidth by applying different pre-emphasis, equalization, and even line coding techniques to either end of the lossy copper traces. When I took a look at Quellan's plans earlier this year, they had set their sights on applying their innovative hybrid signal processing methodology to equalize and restore the wildly attenuated multi-gigabit signals after their trip across the backplane. Although most companies making high-speed SerDes incorporate some sort of equalization into their products, Quellan applied some real rocket science to the problem and came up with a hybrid digital/analog adaptive equalization technique that would significantly out-perform anything I'd seen to date.
But Quellan is full of surprises. While I quietly waited for their first alpha silicon to emerge, it seems that they were taking another look at the problem and realized there was a better way to solve it. The result is the Nx600, what appears to be the industry's first Gigabit noise canceller. The Reader's Digest version of the story is that it appears to dramatically reduce crosstalk from adjacent channels by sampling their signals and re-injecting an inverted version into the receiver at the level and phase required to cancel it. The results appear to be dramatic, with Quellan's test rig demonstrating a six order of magnitude improvement in the BER of a 5.0-Gbit/s signal across a poor-quality, 1.25 Gbit/s backplane.
While it must be used in conjunction with a separate SerDes transceiver, and this first product can only cancel one channel, the implications of this product are significant. If this thing works as they claim, it can be used to selectively clean up the handful of ill-mannered "problem channels" found on nearly every legacy backplane. These are pairs of traces whose length, manufacturing tolerances, and position with respect to other noisy channels makes them especially good receivers for noise coming from adjacent traces and from internal reflections. While a SerDes transceiver with reasonably good pre-emphasis and equalization might be able to move 5-Gbit/s traffic across most of the channels, there are usually a handful of connections that cannot support these speeds. By adding a canceller to these worst-case channels, designers should be able to bring the entire backplane up to a higher speed of operation, and add years of life to the chassis it resides in.
To make their point, Quellan has created a demonstration that tries to shove a 5-Gbit/s signal across a particularly troublesome 36 inch set of traces in an older backplane. Due to a heavy schedule, I was not able to make the technical demonstration that they were running in Atlanta this week, but I was able to see the screen shots they took. The pictures I saw showed a signal that was buried in noise from its own reflections and adjacent channel crosstalk. Switching on the canceller dramatically cleared up the signal to the point where it was obvious that any reasonably-designed SerDes receiver could extract a clean bit stream from it. For now about all I can do is say that the screen shots I saw validate Quellan's basic claims that the chip's five-tap FIR filter and on-chip phase adjustment can deliver up To 10 dB NEXT cancellation and improve BER in noisy environments by a factor of 1,000,000 or more.
But what I saw during my briefing intrigued me enough that I'm taking Quellan up on its invitation to view the demonstration live. To do this I'll be taking the long way to my appointments in Atlanta this week with a quick swing through Silicon Valley to catch Quellan's demo. Hopefully, some hands-on time with a live system will help resolve my last remaining doubts about the technology's effectiveness and let me soak up more information about how it works.
If all goes well, I'll have a second part to this review for you next week that fills you in on all the juicy details. I've also asked my partner, Paul McGoldrick (analogZONE's founder and resident analog expert) to provide his analysis as well.
The Nx600 is fabricated in 0.18 µm CMOS, and is housed in a 24-Pin Package. Selected customers should probably expect to get samples within the next couple of months, with production slated for early next year. While price is still not firmed up, Quellan says it expects to sell the Nx600 for "under $20" in production volumes.