San Diego -- Nonlinear signal-processing algorithms from Chaos Telecom Inc. look to improve the effective signal-to-noise ratio of DSL modems and consequently improve their range, data rate or power requirements.
By year's end, Chaos Telecom hopes to sign licensing deals with several DSL chip makers now evaluating the algorithms. The startup is marketing them as intellectual property for use in chips that would address two drawbacks of DSL service compared with cable: limited distance and slower downloads.
"About a half-dozen DSL ASIC companies are evaluating our algorithms," said CEO Larry Fromm. "We hope to get our solution embedded into their silicon. We expect to have licensing revenue starting this year." Revenue would be tied to the volume of licensees' DSL chip sales.
Five-year-old Chaos Telecom bases its technology on the chaos theory concept of nonlinear dynamics--an area of expertise of two of its founders, Henry Abarbanel, a full-time professor of physics at the University of California, San Diego, and James Lemke, an adjunct professor with the school's electrical and computer engineering department. Abarbanel is a researcher at UCSD's Institute for Nonlinear Science, as are co-founders Nikolai Rulkov, Lev Tsimring and Alexander Volkovskii. Chaos Telecom has five mostly part-time workers and has raised about $3 million to date, primarily from SBV Venture Partners.
Working with a "partner"--described by Fromm as a major communications ASIC company but not otherwise identified--Chaos has demonstrated the effectiveness of its IP. "We are actively trying to sell it to all the major DSL chip companies," he said.
Today's signal processors typically employ linear processing techniques; few claim nonlinear signal-processing capability, though the technology is not new. Nor is it easy. "Interest in nonlinear signal processing is increasing because advances in computational capabilities now make it practical to implement more-sophisticated nonlinear processing techniques," Will Strauss, president of Forward Concepts Co., said in an e-mail exchange. Nonlinear approaches could perform much better than linear ones to process especially noisy signals, "as in removing impulsive-type or heavy-tailed noise," Strauss said. "However, sometimes employing both linear and nonlinear techniques simultaneously will do a better job than either."
Some "noise" on a communications circuit comprises "complex but utterly deterministic nonlinear artifacts of the original signal" that can cause nonlinear impairments in the communications channel, Chaos' Fromm said. "These artifacts are so complex that no one, to our knowledge, has even attempted to eliminate them in a complex communication system."
Few companies aside from Chaos have tried to commercialize the technology. In January 2002, nDSP Inc., a fabless provider of nonlinear digital signal-processing ICs, was acquired by Pixelworks Inc. (Tualatin, Ore.), which said at the time that it planned to offer chip sets and systems-on-chip integrating its image- and video-processing technology with nDSP's products. Two of the three products that were being developed by nDSP were subsequently completed; a third was dropped.
Optichron Inc., a fabless semiconductor company based in Fremont, Calif., leverages proprietary nonlinear signal-processing technology in its Linearizer engine, a silicon chip that's a part of its Turbolinear family of analog-to-digital converter modules. The modules enhance communications by improving linearity and overcoming nonlinear distortion, enabling higher-performance systems at reduced costs, the company said.
"The Linearizer engine is scalable, allowing engineers to simply enable or disable filter blocks to meet their specific design needs," said vice president of marketing Juan Garcia. Wireless communications and cellular infrastructure companies have shown particular interest. "The technology is quite leverageable throughout the cellular send and receive paths," Garcia said. Optichron will announce monolithic chips incorporating the technology soon.
Chaos Telecom's algorithms improve the effective signal-to-noise ratio (SNR) of a system at little cost by eliminating complex nonlinear artifacts, Fromm said.
Common nonlinear impairments in a communications channel include saturated amplifiers and oxidized junctions. "On impaired ADSL lines, our nonlinear echo canceler improves the effective SNR by 8 dB, which means a data rate improvement of about 374 kbits/second on an ADSL line," Fromm said. "Since our solution tends to work best on the poorest-performing [i.e., most-impaired and longest] lines, the improvement is often significant [and may mean] the difference between a home's being able to receive ADSL service or not."
The algorithms, which Chaos says will work with future as well as existing standards, are implemented on a single side of the communication channel. "Almost all improvements to communication systems require changes to both the transmitter and receiver. Our solution works at the receiver only--it does not require any changes to the transmitter--and still improves the communication system," Fromm said.
Once Chaos Telecom establishes a revenue stream, Fromm said, the company will expand and try to apply its IP beyond DSL chips. "Increased SNR is the coin of the realm," he said. "We hope to grow our team and adapt the technology to other markets, such as satellite communications and 10-Gbit Ethernet."
The company has reached out to potential customers in those areas. "Preliminary talks are encouraging," Fromm said.
