NYT on BPL
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Sun Nov 2 15:23:13 CST 2003
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Power Line Nets Take New Tack: Streaming A/V
Wayne, N.J. - With service providers looking to deliver triple-play
services-voice, video and data-over broadband pipes, interest in
streaming signals throughout the home is at an all-time high in the
development community. The HomePlug Powerline Alliance is returning
to the drawing board to craft a ground-up specification, HomePlug AV,
that will be optimized for audio and video streaming over home power
"No new wires!" was the rallying cry the HomePlug alliance adopted
last year for its campaign to use existing power lines to deliver
14-Mbit/second throughput for distributing broadband connections in
the home. In the ensuing months, however, the group's contention that
its approach would be a formidable competitor on the home front to
802.11 wireless LANs has largely fallen on deaf ears.
As the alliance has struggled to convince chip companies and systems
houses to ante up for development and marketing, WLAN systems have
grabbed the lion's share of home-networking applications. The
difference still comes down to the wire: Both wireless and HomePlug
deliver the ability to distribute broadband connections, said Peter
Kempf, president of the HomePlug Powerline Alliance, but "wireless
delivers the added benefit of mobility."
Now HomePlug vendors are regrouping to attack the WLAN behemoth from
another angle. They are already calling the upcoming spec a better
home A/V streaming option than wireless LANs.Chip set costs
A few members of the HomePlug camp have pointed to the disparity in
marketing budgets as a reason for WLAN's victories on the home front.
But while there's no doubt that far more marketing dollars have
flowed to wireless, a more salient reason for Wi-Fi's dominance to
this point may be the disparities in chip set implementations.
Currently, the cost for implementing 802.11b in a router or other
networking product falls in the $10 range, said Michael Greeson,
principal analyst at research firm Parks Associates. Competing
solutions must ask how they stack up against that cost, he said.
In HomePlug's case, the answer thus far is that they haven't measured
up well. According to Kempf, adding HomePlug to a design will run
between $12 and $15.
HomePlug chip costs are coming more in line with 802.11b pricing with
the release of second generation of chip sets. But even if they can
match the cost, HomePlug vendors face issues on the on the data rate
HomePlug 1.0 systems deliver a peak throughput of 14 Mbits/s, while
802.11b WLAN systems cap out at 11 Mbit/s: advantage HomePlug. But
most of the design effort in the WLAN sector has moved beyond 802.11b
systems toward developing 802.11g or 802.11a architectures, which
increase data rates into the 54-Mbit range: advantage wireless. And,
like 802.11b silicon, the cost of these chips is quickly coming down,
again prompting OEMs to lean toward WLANs for home-networking
"Existing HomePlug technology delivers a real throughput of about 3
to 8 Mbits/s," said Allen Huotari, technical leader at Cisco Systems'
Linksys unit. "That falls short of what you can get with 802.11g and
Time to regroup
The problems with HomePlug have clearly been felt at the equipment
level. Siemens, once a shining star in the sector, has abandoned its
HomePlug efforts. Linksys has bridging devices and a wall adapter
reference design for HomePlug but is still focusing on the WLAN
arena. And Iogear Inc., Phonex Broadband Corp. and NetGear Inc. see
interest rising for HomePlug, but nowhere near the levels seen for
But hopes are high for the follow-on, HomePlug AV spec. "We're
getting to the point where people want to know what's next," Kempf
said. And for HomePlug, what's next is a spec that is optimized for
multimedia delivery in the home.
Whereas the WLAN sector is looking to make changes at the
media-access control (MAC) layer to support advanced
quality-of-service (QoS) capabilities, the HomePlug camp has pursued
what is "really a top-down rework" of its spec, said Arnaud Perrier,
product-marketing manager at HomePlug chip vendor Intellon Corp.
Audio/video system vendors, he noted, do not base the movement of
signals on the Ethernet model-the model used for WLAN system
development. "Video streams are isochronous in nature," Perrier said.
Thus, with the new spec, the HomePlug Alliance intends to enable
solutions more optimized for video transfers.
"We think by starting from scratch we can do something 802.11 cannot
do," said HomePlug's Kempf.
Right now, the HomePlug association has five proposals on the table
for the AV spec. Kempf said the organization is conducting a
"bake-off" on the technologies and could adopt a solution as early as
late November. "In less than two months, we could have a technology
for AV," he said.
Since the decision hasn't been made, HomePlug backers are being quiet
on the specific technology options under consideration. But they're
forthcoming about the data rate performance the technology is
expected to provide.
Clearly, to support high-bandwidth streams like high-definition TV,
HomePlug AV systems will need to provide real throughput in the
50-Mbit/s range. What's up for debate is whether the AV spec should
define a 100- or 200-Mbit/s peak throughput to achieve it. While 200
Mbits/s is possible under some of the proposals, analyst Greeson
said, 100 Mbit/s is the likely stop for the spec.
The big question
What designers still must question, however, is whether the move to
100 Mbits/s and optimization for multimedia streaming will be enough
for HomePlug to win ports away from WLAN systems. Clearly, the WLAN
camp has also been moving forward, adding extensions to the 802.11
specification to support audio and video streaming. The 802.11e spec,
which defines the QoS upgrades for the 802.11 MAC, is in draft form
could be ratified next year, observers of the process said. And chip
set vendors are already prepping support for the QoS capabilities
defined in 802.11e, thus setting the stage for a battle between
802.11 and HomePlug on a new front.
"802.11 hasn't had the QoS capabilities needed to handle A/V
services," Linksys' Huotari said, "but it will."
As for which camp will win this next phase of the war for home
broadband delivery, some observers say it doesn't have to be an
either/or proposition. A merged HomePlug/wireless network, these
sources say, could be the best option for handling audio and video
distribution. Under this model, HomePlug AV technology would be used
to establish a home backbone. End users would then connect either
ultrawideband or 802.11 wireless access points around the house to
stream audio, video and data the last few feet.
Greeson is among those who consider this scenario viable for the
home-networking environment. With the cost of wireless on the
decline, he said, wireless-access points will be embedded in all
kinds of devices. But to make this model effective, a strong backbone
is needed to move content from room to room. and HomePlug AV might
fill the bill.
Huotari also sees merit in using HomePlug AV as a backbone, provided
the alliance lives up to its promise that the spec will deliver 50
Mbits/s in 90 percent of the cases.
And it would behoove HomePlug's backers to deliver on that promise as
quickly as possible, whether the follow-on spec is used to build
wireless backbones or standalone nets. Kempf said that chips based on
the AV specification could hit the market by midyear 2004, with
end-user systems hitting the shelves in time for next year's holiday
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