Multiple Standards Vie for Home Networking Supremacy

"No new wires" is the rallying cry of four different standards contending for dominance in the potentially lucrative home-networking market. While it is increasingly common for new construction to have CAT5 cable installed throughout the home for wired Ethernet connections, the overwhelming majority of home networks will have to use wireless connections or existing home wiring such as the power lines or phone lines.

There are four basic types of home networks:

• Data networks that connect PCs and Macs.
• Communication networks that connect phones and Faxs.
• Entertainment networks that connect TVs, stereos, and game consoles.
• Control networks that tie in lighting, heating and cooling, security, and home automation.

Next it was predicted that high-speed Internet access via ADSL or cable modems would penetrate the home market, necessitating sharing this connection among multiple PCs. However, actual installations of high-speed Internet connections have not lived up to initial rosy predictions.

The most recent vision for a "killer app" for home networking sees a home gateway that provides many forms of digitized content for distribution throughout the home. Products such as DVD players, digital video recorders (DVRs), set-top boxes, graphics processors, digital cameras, and digital audio receivers (DARs) deliver video-on-demand, along with streaming video and audio, and enable head-to-head gaming applications to be shared across different devices in the home including PCs and televisions. Consumer electronics, including digital televisions, set-top boxes, digital replay devices, DVD players, and MP3 tuners, along with plain old telephone service (POTS) are being integrated into the home network and require support for high-performance, reliable networking technologies. Although current home networks operate in the range of 10 Mbit/s, that is still 10 times slower than fast Ethernet at 100 Mbit/s.

Access providers for telephone, cable TV, satellite TV, and so on are starting to carry all kinds of information in a digital format. That means a telephone company can offer Internet services and video-on-demand, while a cable TV company can offer phone services. These providers are all planning to deliver integrated services. These services will come in a bundle with a single monthly bill that's less than if the consumer bought these services separately.

According to Strategy Analytics, 85% of U.S. homes will be online by 2005 with at least 75% of that group using multiple devices. Currently, some 65% of US households have a PC, and some 22 million homes have more than one. By 2005, Analysts predict that over 46 million U.S. households will use broadband connections to access the Internet, up from 10 million today, and 25-million home networks will be installed by 2004.

Figure 1:  Cayman's 3220 ADSL home gateway combines a four-port 10BaseT Ethernet hub with optional support for IEEE 802.11b and HomeRF wireless home networks.

The recently approved IEEE 802.11g standard offers the data rate of IEEE 802.11a, while maintaining backward compatibility with IEEE 802.11b without the necessity of a dual-mode radio.

HomeRF extends beyond wireless LAN with 10-Mbps performance, cordless telephone support for up to eight lines, QoS support for media streaming, including music and TV, and standardized roaming. HomeRF streaming supports a range of options including multi-cast, two-way (in other words, videoconferencing) and receive-only configurations. The technology allows up to eight simultaneous sessions with typical applications such as MP3 headsets, remote Dolby Surround-Sound speakers, and MPEG4 video distribution.

HomeRF was designed from the beginning to provide privacy and security for consumers and small businesses that don't have network administrators to protect them. HomeRF uses pseudo-random frequency-hopping technology. The technology also adds a 24-bit network ID, 128-bit data encryption, and other security features.

HomeRF products first hit the market in 2000 with 1.6-Mbit/s performance. Nearly all of the early products were PC related and supported data applications. HomeRF 2.0, with 10-Mbit/s performance, debuted in 2001 and supports more phone lines and new features for digital music and Internet-based TV. HomeRF 2.0 is compatible with first-generation HomeRF products.

Figure 2:  The Motorola Simplefi wireless digital-audio receiver allows users to experience their favorite Internet music on their stereos. Users can play MP3s directly on their home entertainment system without burning a CD and play streaming audio and Internet radio from content providers via a wireless HomeRF link to their PC.

HomePNA uses frequency-division multiplexing (FDM). Focus groups reveal that one barrier to Home PNA adoption is that consumers do not understand how phone lines can be used for simultaneous voice and data communications. HomePNA proponents maintain that a standard phone line has enough bandwidth to support POTS, a high-speed DSL modem, and a home phone-line network. The biggest drawback to HomePNA is that the average house in the U.S. has fewer than five phone jacks. In Europe, the average number of phone jacks per house is less than two.

HomePNA's support of QoS ensures reliable content delivery to the end-user. HPNA 1.0, the original version of the standard, operated at a rather slow 1 Mbit/s. The current specification, HPNA 2.0, is based on technology developed by Broadcom and operates at a faster 10 Mbit/s. This second generation of HomePNA delivers 10 Mbit/s of performance over the phoneline, which translates into eight to ten times the performance of a high-speed DSL or cable Internet connection. HomePNA version 3.0 is expected to be finalized by the fourth quarter of 2002 and will reach a throughput rate of up to 100 Mbit/s. Version 3.0 will be compatible with other services such as POTS, ISDN, and xDSL, and will be backwards compatible with HomePNA 1.0 and 2.0. The Voice-over-HomePNA application, which extends HomePNA 2.0 by enabling eight simultaneous high-quality voice streams within the home, will also be supported by version 3.0. QoS enables the HomePNA phoneline technology to prioritize data, audio, and video traffic delivery, in real-time without disruption. Bandwidth demands for multimedia applications will continue to increase within the home as entertainment applications push the adoption of home networking, making QoS essential.

HomePNA offers several advantages: it's standardized, easy to install, and inexpensive. It requires no additional networking equipment, such as hubs or routers, and supports up to 25 devices. HomePNA does have some limitations. Physically, users will need a phone jack close to each computer or Internet appliance. There is a 1000-foot limit for wiring between devices and the overall area of coverage should not exceed 10,000 square feet. Also, the possibility of substandard phone-line wiring exists. It is estimated that in less than one percent of U.S. homes HomePNA will not work on the existing wiring.

Figure 3:  Netgear Phoneline adapters allow users to transform the existing phone lines in their homes into a computer network. Installation is simple: just plug one end into the PC's USB port and the other end into a telephone wall jack.

The HomePlug 1.0 specification was released in June of 2001. HomePlug 1.0 technology uses an enhanced form of orthogonal frequency-division multiplexing (OFDM) with forward error-correction, similar to the technology found in DSL modems. The available range of frequencies on the electrical subsystem (4.3 MHz to 20.9 MHz) is split into 84 separate carriers. OFDM sends packets of data simultaneously along several of the carrier frequencies, allowing for increased speed and reliability. If noise or a surge in power usage disrupts one of the frequencies, the system will sense it and switch that data to another carrier. This rate-adaptive design allows the maintenance of an Ethernet-class connection throughout the powerline network without losing any data.

Figure 4:  The Asoka USB Adapter allow users to utilize their existing home power outlets to turn their home powerline wiring into a high-speed home network at up to 14 Mbit/s. The adapter is compliant with the HomePlug power line v1.0 industry standard.

"The HomePlug market is not without its hurdles, however," says Mike Wolf, a Director with In-Stat/MDR. "The development of a rival standard in the Consumer Electronics Association (CEA)'s R7.3, the need for compliance with power emission regulations in different countries, and, perhaps most importantly, the need to educate consumers about the benefits of powerline networking are all inhibitors." The market will face some of the same hurdles that impacted the Home Phoneline Networking Alliance (HPNA) marketplace. Research has shown that consumers have a difficult time grasping the concept of networking over power lines. However, In-Stat/MDR believes that HomePlug has the following advantages over HPNA:

• A larger potential market, because powerline networking will likely be adopted in more countries than phoneline networking.
• A higher number of power outlets per home compared to phone jacks.

According to HomePlug, communicating at millions of bits per second over common house wiring requires sophisticated algorithms running on fast silicon. House wiring is a hostile environment for high data rates. Brush motors in hair dryers and kitchen appliances are a significant source of interference. Turning appliances on and off, using dimmer switches, and using halogen lights injects noise spikes into the transmission line. Each branch off the main breaker panel acts as a stub, causing multipath interference. In addition, the whole network of house wiring acts as an antenna, picking up RF interference from radio transmitters.

Signal attenuation is another problem. Long runs between outlets are one cause, but the common surge-suppressor power strip often contains filters to block high frequencies—the very ones HomePlug uses to carry data. Furthermore, most houses in the U.S. take power from both sides of the neighborhood distribution transformer's secondary windings, creating two 120V phases and one 240V phase. Powerline signals must go through this winding if an outlet is on one phase and a second outlet on the other phase. The secondary winding acts as a lowpass filter, attenuating the signal. All these factors create a unique, often-complex, time-varying transfer function for each outlet-to-outlet channel in a home.

About the Author Charles H. Small is a technical editor based in Waltham, MA.