Chip Pushes Twisted-Pair Copper To 10 Gbits

FREMONT, Calif. — Sreen Raghaven, president and CEO of Vativ Technologies Inc., said it took three major areas of work to produce a single-chip, proprietary short-haul transceiver for 10-Gbit/second full-duplex operation over Category 5e or CAT6 unshielded copper twisted pair. The San Diego startup is sampling the transceiver now to key prospects.

"Getting to 10 Gbits/s on twisted-pair wiring is all about using existing bandwidth more efficiently," Raghaven said. "First, we had to implement an encoding scheme that gave us more effective bits per baud. That had to be coupled with much more aggressive forward error correction to improve the noise margin."

"Second, we needed to significantly improve both the bandwidth and the linearity of the mixed-signal section of the chip. Third, we had to dramatically increase the throughput of the digital signal-processing function, both to keep up with the increased bit rate and to handle the more aggressive algorithms."

The chip, fabricated in 130-nanometer mixed-signal CMOS, connects directly to a standard RJ-45 connector on the media side and to a Xaui port on the system side. The device includes a proprietary PHY and DSP functions to do the heavy lifting.

The company chose 6-bit/baud quadrature amplitude modulation, leveraging QAM's efficient bandwidth utilization and computability. The modulation technique is backed up by a modified multidimensional trellis forward error correction (FEC) algorithm.The result, according to Raghaven, is a chip that achieves a great deal in a standard technology. The front-end amplifier sends the signal from the copper to a high-linearity A/D converter operating "in the range of 1 Gsample/s." That data, in turn, is multiplexed into a bank of four DSP data paths responsible for decoding and FEC computation. Of course, there is a complementary transmit path.

Vativ is betting that availability of the chip in advance of a 10-Gbit Ethernet standard, along with the chip's demonstrated compatibility with CAT5e-6 cable and RJ-45 connectors, will give the company an early beachhead in the data center, where proprietary 10-Gbit connections with a range of less than 15 meters or so make economic sense. The company is working with partners to provide the chip in modules that could drop into existing Xenpac slots without mechanical or software changes, giving data center managers an alternative to short-haul fiber at a fraction of the total cost.