Hostile Environs!

Sat, 05/31/2003 - 8:00pm
David Iler, Contributing Editor

It takes a bold competitor to step into the ring with one of broadband's fastest-growing and most hyped technologies–wireless networking–but that's exactly what the proponents of powerline networking are doing.

Establishing networks through powerline wiring in homes with Ethernet and Universal Serial Bus (USB) bridges has mainly been viewed as a complementary technology that reaches into areas of the home not accessed by IEEE 802.11b signals or served by telephone outlets for HomePNA connections. New powerline devices on the market include an 802.11b transceiver and router, serving as an extension of wireless nets–useful, but still complementary.

Also, nagging issues such as poor marketing compared to the mighty Wi-Fi (Wireless-Fidelity, 802.11x) industry, less-than-spectacular throughputs, and a relatively late-to-market launch of standardized powerline products last year have cast powerline nets as the underdog in home networking technologies.

However, a new iteration of the HomePlug Powerline Alliance 1.0 specification, dubbed HomePlug AV, promises to become much more than a complementary technology, instead serving as a high-bandwidth video backbone for the home. While HomePlug AV is only in the very early stages of development, the forthcoming ReadyWire chip developed by Phonex Broadband Corp. offers compelling audio applications that may differentiate powerline from competing technologies in the more immediate future.


Promoted and certified by the HomePlug Powerline Alliance, powerline devices plug into an electrical outlet and use Ethernet to connect to other computers and IP devices. A simple powerline network may consist of a cable modem or DSL router in a home office connected to a powerline Ethernet bridge plugged into an electric outlet. A computer connected into another Ethernet bridge plugged into an outlet in a faraway bedroom, for example, completes the network.

Similarly, an 802.11b-enabled powerline device can receive a broadband signal from a cable modem/DSL router through a home's power grid and pass it wirelessly to an 802.11b-capable PC.

Although HomePlug-certified products have been on the market for slightly less than 12 months, the concept has been around for years. Still, the technology's market share has been minuscule.

Karen Sohl, corporate communications manager for Linksys Group Inc., which sells all forms of networking products, says wired Ethernet remains the most installed home networking technology, according to company sales. Linksys, which is about to merge with Cisco Systems, shipped about 1.4 million wireless home-net products in the first quarter of this year, approximately 7,000 of them being the HomePNA variety.

Powerline devices lag far behind for Linksys, with about 3,500 units shipped for the first quarter of this year.

"We're sitting in the shadow of a pretty popular solution right now," i.e., wireless, says Peter Kempf, HomePlug Powerline Alliance president and vice president of marketing and networking components for chipmaker Conexant Systems. Still, powerline has compelling features that have kept vendors such as Linksys and others in the powerline market.


A key selling point of powerline networking is the near-ubiquitous presence of power outlets throughout a home, reaching into corners and rooms where wireless and phone line access points don't reach or are not present. Most houses average more than 40 electrical plug pairs.

"Powerline is more of a backbone technology," says Corey Chao, marketing manager of Efficient Networks Inc., a subsidiary of Siemens Corp. that makes powerline devices. "It's a way to reach every part of the home."

Other favorable aspects of HomePlug include its ease and simplicity in setting up a network due to its reliance on Ethernet, and its industrial strength, always-on 56-bit DES encryption. Wi-Fi, in comparison, offers an optional, albeit hackable, 10-bit WEP (Wired Equivalent Privacy) encryption scheme, but devices that support the more fortified Wi-Fi Protected Access (WPA) platform are on the way.


For modulation and transmission, the HomePlug 1.0 specification relies on Orthogonal Frequency Division Multiplexing (OFDM), which according to Kempf, "sounds the channel," selects the tones with the best signal-to-noise ratio, filters out noisy parts of the spectrum, and transmits on the "clean" portion of the spectrum. HomePlug 1.0 uses 76 tones within the 4 MHz to 21 MHz spectrum.

The HomePlug 1.0 specification provides for a basic throughput at the Physical Layer of 14 megabits per second, although actual throughputs range from 5 Mbps to 8 Mbps.


Conspicuous by its absence in the HomePlug Powerline Alliance is Broadcom Corp., a former member of the group.

Broadcom, which develops silicon for wireless and HomePNA networking products, has raised some questions about HomePlug's signal.

Tests conducted by Broadcom in December 2001 indicated that powerline technologies working in the 4 MHz to 20 MHz band can interfere with Federal Communications Commission-licensed bands in that range used by amateur radio operators, notes Stephen Palm, principal engineer for Broadcom's Home and Wireless Networking Division. Additionally, Broadcom found powerline signals could degrade HomePNA signals.

Larry Yonge, vice president of Intellon Corp., a developer of networking semiconductors, counters that HomePlug "went through great pains to be friendly with amateur radio bands."

"To meet the HomePlug specification, you have to do notch filtering" for licensed radio bands within the 4 MHz to 21 MHz spectrum, he points out.

With regard to HomePNA signals, Yonge says any interference "is really a function of the routing of wires," specifically the proximity of telephone and powerline wires in a wall, and the quality of the twisted pair. "A good design should not pass the signal," he adds. "The more likely path [of interference] is a poorly designed [HomePNA] power supply."

Yonge adds that HomePlug was "designed to exist with other signals on the powerline," including power signals used by appliances. By adapting the modulation on each carrier, through OFDM, HomePlug signals will adapt and choose other channels to co-exist, he says.

Yet interference, Palm notes, wasn't the only issue Broadcom had with powerline. "For distributing video, it just didn't quite measure up as a backbone technology," he says.


Addressing this concern, and perhaps the real dragon-slayer for HomePlug, is the planned AV iteration of the spec, for which a technology RFP (request for proposal) has just been issued. The core aim of HomePlug AV is to simultaneously deliver six channels of standard definition television or two simultaneous channels of high-definition video within the 4-21 MHz band. The AV version also calls for throughputs that scream at up to 100 Mbps.

"The challenge is to do more than just a single stream of video," says Kempf. In this way, a HomePlug AV network could become a "true video backbone of the home."

"The killer application for powerline is video," he says, noting that the spec will attempt to meet the requirements of voice-over-IP through a quality of service (QoS) scheme that accounts for jitter and latency.

Adding a QoS component, according to Carl Mansfield, senior manager of multimedia communications for Sharp Laboratories of America, will require the spec to include functionality beyond the Media Access Control layer to provide a transport layer, allow for remote control, and accommodate a video format, most likely MPEG-2.

Also needed in the AV iteration of HomePlug will be a network discovery scheme such as Universal Plug and Play, although it's unclear whether it will actually be written into the standard. To accommodate legacy devices such as televisions and monitors, the spec will most likely support dongles or adapters with a HomePlug AV interface and left/right audio and S-Video connector interfaces.

As a key developer of cable modem and set-top box silicon, Conexant has given thought to the possibilities of a video backbone enabled by HomePlug AV. For example, Kempf notes that a multiple-tuner set-top or media center with a hard disk drive typically has been designed to sit near the living room television in most homes. Imagine connecting that full-featured set-top to other, less-expensive boxes in the home through a powerline net that can access the resources of the main box and display content on televisions or stand-alone liquid crystal or flat panel displays–all without running new wires.

These types of applications are made more relevant by the presence of key large consumer electronics companies in the HomePlug Alliance, including Sharp, Matsushita Electric Corporation of America (Panasonic) and Sony Corp.

"Having these people focus on HomePlug is a tremendous plus," says Kempf.

According to Mansfield, several companies are working on audio applications that would work well with a HomePlug AV network. As an example of a device on the market today, he noted Philips Electronics' FW-i1000 Internet Audio Mini HiFi boom box which is equipped with an RJ-45 Ethernet jack and online audio download features.

Using a HomePlug Ethernet bridge, the box can access a cable modem in another room through a home's powerline network to download music. He expects more sophisticated audio and video applications to emerge as HomePlug AV is developed.

A significant caveat to HomePlug AV is its development cycle. Mansfield projects that HomePlug AV-based product will be on the market in three years, a timeframe that seems distant given the rapid pace of today's technology. This perception is not lost on Chao. "The only thing we're concerned about is the timeframe," he says. "That's something we're battling…to get something out earlier."

The HomePlug Alliance hopes to complete the AV spec in 12-to-17 months.


While most of the powerline net industry focuses on HomePlug AV, Phonex is moving quickly on a new chip, dubbed ReadyWire. The integrated chip includes both a digital signal processor and an ARM 946 processor and executes a QoS scheme called TimeSlot. TimeSlot, says Phonex Director of Marketing Brad Warnock, parts out bandwidth using Time Division Multiple Access (TDMA) into 15 time slots. Further, it allocates a particular time slot to a specific application or device, and controls slots independently of each other, suitable for low-bandwidth audio.

The ReadyWire chip will be capable of 599 kilobits per second of throughput. Warnock expects a ReadyWire-based device with RCA and speaker output jacks to accommodate conventional audio or surround sound speakers and/or headphones for either whole house audio or MP3 streaming audio from a computer.


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