The cable industry is beginning to seriously consider using
fixed-wireless broadband technology as a means of extending its infrastructure into the
business sector, prompting new thinking on the subject at Cable Television Laboratories
Inc. and among leading suppliers.
"CableLabs has always taken the position that there
should be a means available for supporting wireless extension of the cable-network
infrastructure to ensure broader market coverage," CableLabs CEO Richard Green said.
"We're in a position to move in this direction, given the background of effort
we've already expended on wireless, if the board [of directors] chooses to make this
Green said that while resolving issues related to wireless
transmission and architecture may not be as compelling as other projects CableLabs has
going, there is growing recognition among operators that the industry's newly
developed high-speed-data and Internet-telephony platforms could generate significant new
business in the commercial sector.
"The problem is that our networks don't serve
many of those potentially lucrative locations where business is concentrated, which is
where wireless could make a difference," he added.
The cable-products unit at Cisco Systems Inc. is actively
promoting new wireless technology to cable operators in response to intensifying desire
for access to the business sector, said Paul Bosco, vice president and general manager of
"The cable guys are picking up on this and looking at
using it for offering cable services to small and medium-sized businesses, as well as for
backhaul applications where they would connect noncontiguous pieces of the HFC [hybrid
fiber-coaxial] network," he added.
Cisco has integrated wireless-access links based on its new
VOFDM (vector orthogonal frequency-division multiplexing) technology into its cable-data
platform, including "uBR" (universal broadband router) headend and router
products, Bosco said.
"This is a non-line-of-sight technology that opens the
possibility of using multiaccess-based architecture to cable operators," he said,
adding that the platform can also be used to reach customers over digital-subscriber-line
links via telephone wires.
VOFDM is one of the new over-the-air transmission
technologies CableLabs is following as it awaits further direction from its members on the
fixed-wireless agenda, Green said, adding, "It's a very interesting possibility,
as are others we're looking at, such as ultra wideband."
"In fact," he said, "CableLabs has some
patents on some of the techniques that are used in VOFDM."
Broadcom Corp. is developing a new ASIC
(application-specific integrated circuit) based on the VOFDM scheme with the
media-access-control technology of DOCSIS (Data Over Cable Service Interface
Specification) built in. Broadcom plans to make the chips available to manufacturers by
the middle of the year.
With Cisco licensing VOFDM at no charge, the companies hope
to persuade industry sectors such as cable to adopt the platform as a de facto standard.
VOFDM is designed to maximize coverage by overcoming
line-of-sight barriers via spatial diversity, which means using a dual-feed antenna
receiver at the end-user premises to capture incoming signals from diverse paths and
combining them to achieve the highest possible signal-to-noise level.
By combining relatively weak reflected signals, the system
delivers an output to the user that is on a par with the quality achieved with a direct
line-of-sight transmission, Bosco said.
But there are other technologies vying for attention as
efficient alternatives to the mainstream approaches used in fixed-wireless applications,
based on the QAM (quadrature amplitude modulation) and QPSK (quadrature phase shift key)
modulation techniques used in wireline transmissions.
"Everybody thought the RF spectrum was pretty well
understood, and that it had become a fairly plodding realm of development. But all of a
sudden, there's a bunch of new approaches that have implications for wireline
applications, as well as wireless applications," Green said.
Ultra wideband is a new technology based on spread-spectrum
techniques that were developed for military applications. This approach to spread
spectrum, in contrast to the widely used CDMA (code-division multiple-access) approach,
uses the entire frequency band to achieve very robust signal-to-noise performance, rather
than breaking that band into smaller channels -- a daunting computational challenge only
recently made cost-effective because of new microprocessors.
Another technology vying for network operators'
attention as the Federal Communications Commission makes ever more wireless spectrum
available under unlicensed and licensed categories is Lucent Technologies'
According to Lucent, its approach could produce a 10- to
20-fold increase in capacity over wireless links and overcome many of the interference
problems that plague today's systems.
Blast uses Lucent-developed algorithms to assign specific
signals to specific transmission paths in the multipath dissemination of a radio wave at a
given frequency. It allows reuse of the frequency many times over to deliver different
messages to and from different users.
"It's an interesting technology that we need to
learn more about," Green noted.
With the increasing availability of spectrum, cable
operators will have many options at their disposal if they choose to avail themselves of
They can bid on new spectrum being made available, such as
the 39-gigahertz block going up for auction in the spring. They can also avail themselves
of unlicensed spectrum, such as the 200-megahertz block available at 5.8 GHz, or lease
slices from license holders, which -- as in the case of
local-multipoint-distribution-service licensees -- often have more than they know what to
Now that companies like Teligent Inc. and WinStar
Communications Inc. are operating fixed-wireless broadband systems commercially, it's
easier to see that the technology can be used to extend cable's high-speed-data
platform into the business market, Bosco noted.
"The DOCSIS platform is ideally suited to meeting the
huge demand for broadband services that is driving so much activity in the small-business
market, which gives the cable industry a big incentive to find a way to reach those
customers," he added.