Cable Television Laboratories Inc. and a subcommittee of
the Institute of Electrical and Electronics Engineers last week made separate moves on how
to best add new modulation techniques to cable modems in order to toughen their
performance, even in all-coaxial systems.
Last Thursday, the IEEE 802.14 group -- after three
deadlock-induced rounds of voting -- decided on a combination solution that meshes
techniques developed individually by Terayon Communication Systems and Broadcom Corp.
The next day, CableLabs said it will also seek out Broadcom
and Terayon to jointly write what is being called the "advanced PHY," or
Terayon's approach, now widely deployed throughout the
world, centers on S-CDMA (synchronous code-division multiple-access) technology. The main
advantage: Upstream data signals glide through noise, even in all-coaxial systems that are
not augmented with fiber.
Broadcom's single-carrier approach, QAM (quadrature
amplitude modulation), offers higher speed and more capacity for upstream data traffic.
Libit Signal Processing Inc. also endorses a single-carrier
QAM technique for the advanced PHY, said Jacob Tanz, vice president of North American
sales for the chip maker.
Merging S-CDMA and QAM techniques would theoretically
create a system that sends data faster when possible, with much better performance in
noisy upstream systems, said Richard Green, CEO of CableLabs.
"It can be done. It will be tricky," Green added.
The advanced-PHY proposal that CableLabs receives from
Terayon and Broadcom will be reviewed as a possible extension to the cable-modem standard
known as DOCSIS (Data Over Cable Service/Interoperability Specification). If it is
approved, the Terayon/Broadcom solution will be added as an extension that will be known
as DOCSIS 1.2. This could happen as early as the first quarter of 1999, with certified
product available a year later, CableLabs officials said.
Notably, Terayon's S-CDMA technology -- essentially
the crown jewel of the company -- will be thrown into a royalty-free DOCSIS licensing
pool, per DOCSIS rules. In the past, Terayon has been adamantly against that move.
Terayon executives could not be reached to discuss the
matter at deadline.
The 802.14 vote and subsequent CableLabs decision
essentially shut the door on a third company's technique: UltraCom Corp. UltraCom,
formed by Hybrid Network Inc. founder Howard Strachman, submitted a technique called
"variable constellation/multitone modulation."
Strachman could not be reached by press time.