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Powerline Communications Extend Converged Home Networks

By Michael Stich & Corey Chao


Within the past few years, American homes have become saturated with new forms of communications. Digital phones, data, and entertainment services such as video over IP were novelties in the home a decade ago, and are now commonplace, with more on the way. As the need to share different types of information among these systems becomes increasingly evident, service providers are looking for networking technologies that are capable of converging data, voice, and audio/video for delivery throughout the home. The solutions they discover should employ existing physical media whenever possible, since the converged home networks will have to be easy for consumers to understand, use, and afford.

One type of network that comes close to fitting the bill is the household electrical grid. Residential powerlines are not usually thought of when considering communications networks, but in many cases, they can provide an excellent medium for home networks transmitting converged digital services. With an average of over 40 power outlets in a typical U.S. home, each one becomes an entry point into a potential home network. In comparison, there are fewer numbers of coaxial cable or telephone jacks. As different technologies become spotlighted by various suppliers and the pros and cons become more evident, consumers and service providers may soon begin to take advantage of this valuable but overlooked resource.

Advantages of Powerline Communications

Consider the physical media available in todays typical home.

Telephone Lines Over 95 percent of U.S. homes have phone lines based on copper-based twisted-pair, but the number of telephone jacks in a home typically dont number more than six or seven. Bandwidth on the phone network may vary, depending on the wiring, but is usually reasonably high.

Coaxial Cables Over 90 percent of homes have coaxial TV cable, and coax is high-capacity by design. But, like telephone jacks, the number of coaxial cable jacks seldom number more than five or six.

Category 5 Wiring Like coax, Cat 5 is satisfactory for the high throughput requirements of digital video, but these networks normally go to only certain rooms in the house, and they provide a single outlet in each room. In addition, Cat 5 is available in less than 10 percent of U.S. homes and, thus, requires a laborious installation for a majority of Americans.

Household powerlines, on the other hand, go to every room and provide multiple sockets in each. If the electrical network were used for communications, every power outlet in the house would be a potential connection.

Wireless local area networks based on the 802.11 standard, are intended to reach everywhere in the home or at least they should. To their credit though, WiFi systems are inexpensive and easy to install and, as a result, they are already widely deployed as laptops with WiFi have also proliferated both consumer and business PC arenas. Unfortunately, wireless LANs do not have enough capacity for multiple streams of high-quality video and, in many installations, they vary in their transmission data rate and range, due to local interference such as cordless phones and other devices that use the same frequency spectrum. For data networks, wireless drop-offs normally do not present a serious problem because PCs (notably laptops) can be moved around for better reception, and the traffic tends to be low bandwidth, low priority data. But, for high bandwidth content that has to be received in real time, such as HD or SD video, erratic transmissions are unacceptable. As for the future of wireless LANs, the Ethernet 802.11n standard is intended to address these issues in the near future.

Today, powerline-based networks are intended to avoid the rate/reach issues that are inherent in wireless networks, delivering a more consistent performance throughout the household grid. Powerline networks provide a much larger, more reliable channel for communicating converged data, voice, and audio/video content than WiFi networks. If coaxial and CAT5 cables provide the most consistent medium and wireless LANs the least consistent, then powerlines sit somewhere in between. Powerlines can, thus, provide a useful extension to the home network, supplementing and overlapping the other media, though not completely substituting for any of them.

Technology Industry Initiatives
Currently, there are no ITU or IEEE standards established for home powerline LANs, though the technology issues are being widely discussed. Of the many alliances among companies that address home networks in general, the HomePlug Alliance, with more than 60 members at all supplier levels, is the largest organization devoted to defining powerline LANs. In 2001, the HomePlug 1.0 standard established powerline networking and today is supported by products from four integrated circuit (IC) manufacturers. The more recent HomePlug AV standard has the announced support to date of 11 IC suppliers and a number of service providers.

HomePlug 1.0 tops out at 14 megabits per second (Mbps), limiting its usefulness to data exchange. On the other hand, HomePlug AV extends the bandwidth minimum to 70 Mbps over powerlines, and it also delivers transmission over cable with a minimum of 100 Mbps. Coaxial transmission could support multiple channels of high-definition (HD) video, depending on the compression used, with additional bandwidth for data and voice. Powerline transmission would be limited to two channels of standard definition (SD) video or a single HD channel, plus data and voice. That HomePlug AV can span different physical media helps enable powerlines to serve as a mid-capacity extension to higher-capacity carriers in the household LAN.

HomePlug has been extremely successful in North America, but in Europe it faces a challenge from the Universal Powerline Alliance (UPA), which delivers maximum transmissions of 90 Mbps over powerlines and even greater performance over coax. Like HomePlug, UPA proposes open standards, though with 11 alliance members, a single IC supplier and no committed service providers, it is not yet widely supported. A different alliance, CEPCA, is focused on the Japanese market, but its standard is unlikely to find use elsewhere.

Other industry initiatives that also seek to leverage the existing infrastructure for home networking include the Media over Cable Alliance (MoCA) and the Home Phone Network Alliance (HomePNA). The 802.11n Ethernet committee and WiFi Alliance will also have significant impact with a standard that upgrades wireless LANs. Given the likelihood that the home network will provide converged information exchange over diverse media, all of the preceding alliances and possibly others may be important in defining residential networking for the future.

Converged Services for Home Networks
For service providers, home networking brings new business opportunities, along with some concerns. Cable TV providers can add VoIP phone services to their products, and telephone providers can offer IP-based television (IPTV). Both types of providers, of course, already supply Internet access. Whatever the source of the converged information services, digital voice calls and radio/TV transmissions take place in real time and require priority over the bursty traffic of the data network. Reserved channels and quality of service (QoS) mechanisms can help resolve these potential conflicts.

Home entertainment LANs will add to the complexity of digital rights management (DRM). The content will not only be more widely disseminated, but it will also be harder to control on the wireless residential connections than on the wired ones. When these factors are added to the basic technical problems inherent in WiFi transmissions, service providers may prefer to keep their support for wired and wireless networks separate for the time being, at least until the industry has resolved the DRM, rate, and reach issues.

System Considerations
While consumer products that can support powerline communications have not yet appeared, the technology is available to integrate directly. RGs, STBs and other central units will be based on IC technology that provides high performance for signal processing, along with flexibility for adapting to emerging standards, different products and various regional requirements.

As residential communications and entertainment requirements continue to evolve, powerlines will become an important element of converged home LANs. No medium goes everywhere and carries all information today, nor is there likely to be an ideal medium in the near future, even after 802.11n Ethernet adds considerable capacity to wireless data LANs. A number of industry initiatives look to bring powerline networking to the mainstream, with the HomePlug Alliance taking the lead in North America. DSPs and advanced analog ICs provide the technology that will enable residential networks to deliver data, voice and audio/video information via a variety of carriers throughout the home.

Programmable digital signal processors (DSPs), which have demonstrated their value in systems with these requirements, will be widely used as an enabling technology. In addition to handling the basic data manipulations required to shift data among different carriers, DSPs provide the performance needed for encoding and decoding voice and audio-video information functions that are essential for home entertainment networks. High-power analog ICs will also be indispensable for linking digital circuitry with carrier electrical wires. An IC manufacturer with leadership in both DSP and analog processes is well-positioned to provide the enabling technology for this emerging form of communications. IT

Michael Stich is director of Service Provider Strategic Marketing and Corey Chao is marketing manager of Residential Gateways and Embedded Systems for Texas Instruments. For more information, please visit the company online at (news - alerts).

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