"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.

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 front.

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 designs.

"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 .11a systems."

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 WLANs.

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.

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 shopping season.