Harmony at home: digital-home networking
As digital data becomes pervasive, designers must deliver in-home devices that automatically interact to simplify operation and share content.
By Warren Webb, Technical Editor -- EDN, January 8, 2004
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The market for digital devices in the home is exploding. Consumers are clamoring for convergence products that provide immediate access to entertainment, security, automation, and computing data from any of their electronic devices. Yet, consumers will not be satisfied until all of these new devices provide minimal installation aggravation and work together seamlessly. Current consumer frustration with complex device setups, intricate equipment interconnections, and incompatible hardware demonstrate the need for industrywide standards for the interoperability of in-home devices. We no longer measure the sophistication of a home-electronics system by the number of remotes on the coffee table but by its simple and intuitive operation.
As a home-electronics designer, your challenge is formidable. You must deliver equipment that not only works with legacy hardware and competing manufacturers' devices, but also is flexible enough to interact with hundreds of yet-to-be-designed products. Although you may have a terrific idea for a home-electronics device, its actual performance is just part of the picture. For example, if your device displays or otherwise renders digital data, it must be compatible with devices that generate or store digital content. A digital television may get its input from an antenna, a cable connection, a personal video recorder, a DVD player, a personal or mobile computer, and possibly a broadband-Internet connection. And the fact that homes usually contain more than one television multiplies the interconnection pathways and possibilities. A home network simplifies all of these connection choices and becomes essential as a home's device collection grows.
Although the elements of a digital home are infinitely variable, several categories of equipment are common to many in-home systems. For example, most systems start with legacy entertainment devices, such as home theaters, televisions, and stereos. Even though these legacy devices are probably analog, designers must include them in their interoperability plans during the transition to an all-digital home. Meanwhile, many of the next-generation all-digital devices also fit into the entertainment category, resulting in a mix of analog and digital hardware. Although they are often omitted from the discussion, you should also factor electronic automation and security devices into long-term digital home planning. Today, many of these devices are stand-alone, proprietary systems, but this situation will change as open interconnection standards become widespread. A truly integrated digital home will allow users to access and control these systems from anywhere within the home or from any remote location with an Internet connection.
Digital revolution
Desktops, laptops, PDAs, and some multifunction cell phones are part of the computing category, the catalyst for the entire digital-home movement. Starting with music, then digital photos, and now, to some extent, movies, consumers have discovered the benefits of archiving content to their personal-computing devices. Computers can easily search, sort, and reproduce content. But the desire to use entertainment devices to render music, photos, and movies stored on a PC has led to a number of specialized consumer products that connect the computer to the television or the stereo. For example, several vendors now offer computer systems featuring Microsoft's Media Center operating system, squarely targeting the digital home. Media Center software is an extension of Windows XP Professional and includes personal-video-recorder features in addition to a special user interface for enhanced multimedia editing, storage, and playback. Because of the specialized hardware requirements, Microsoft sells the Media Center operating system only through authorized vendors, such as HP and ViewSonic. Gateway's 610XL Media Center combines entertainment and computing on a 17-in.-wide screen display (Figure 1). At $2000, the 610XL includes a 3-GHz Intel Pentium 4 processor, 512 Mbytes of DDR SDRAM, a 200-Gbyte hard drive, CD-RW and DVD-RW drives, and wireless networking. Microsoft also offers a free software developer's kit download to help developers create applications and software components for the Media Center operating system.
A LAN is a key element of flexible interoperability when the number of devices is large or spread throughout the home. Networks allow in-home devices to automatically exchange both control information and content. With multiple PCs becoming common in families with school-age children, wired or even wireless networks are common in the home. However, the problem with network connectivity is the sheer number of incompatible media formats and transmission protocols in use today. Because it would be impossible to include hardware and software for each networking standard, device manufacturers generally pick a reasonable subset or allow provisions for field upgrades, such as an expansion-card slot.
The most basic computing-network standard, Ethernet, requires Category 5 wiring, connecting every expected node location throughout the home. Home-electronics enthusiasts have shied away from wired Ethernet because of problems with retrofitting the required cabling. However, because Ethernet and direct wiring have the lowest cost per node of all networking types, it is the choice of many new homebuilders. About 20% of new homes contain some sort of structured wiring for computer networking, entertainment, or related uses. Home Director, an IBM spin-off, sells home-wiring products to home builders for interconnecting audio and video systems, security systems, PCs, and the Internet (Figure 2).
Extolling the benefits of their "no-new-wires" mantra, power-line-networking proponents have been working on ever-increasing data rates. From the first agonizingly slow X-10 products introduced in the mid-1970s to the promise of 100 Mbps with the next-generation Homeplug AV standard, power-line networking seems to be an ideal interconnection scheme for the home: Just plug in the power cord, and your device also connects to the network. However, power-line networking has some inherent problems, including tethered operation, node cost, phase coupling, and neighborhood bandwidth sharing. With roots in home and building automation, Domosys' PowerBus and Echelon's LonWorks protocols also enable low-data-rate device interoperability over home power lines.
Untethered networking
The popularity of port-able, battery-operated equipment, such as PDAs and laptop computers, has pushed wireless interconnections to the top spot for many home-network designers. Although the range varies depending on the standard, wireless networks allow complete device mobility inside and on the periphery of the home. WiFi (Wireless Fidelity), or 802.11b, the current wireless favorite, offers low-cost silicon, wide adoption, and a range that is compatible with the home environment. However, the half-duplex protocol 802.11b operates in the same 2.4-GHz range as microwaves and many cordless phones, so plenty of opportunity exists for interference. In most instances, this interference does not stop transmission, but it does slow the data rate. With a maximum range of about 100m, 802.11b uses Ethernet protocol and carrier-sense, multiple-access with collision avoidance to allow multiple users to share the same spectrum.
Because WiFi's maximum 11-Mbps raw data rate is marginal for a single video stream and unacceptable for multiple streams or high-definition television, home-network designers will probably select a higher bandwidth alternative for wireless video. Unauthorized users can easily penetrate 802.11b networks without local security provisions. Some experts have even suggested Bluetooth as a short-range alternative for home networks. But with its 10m range and 1-Mbps bandwidth, Bluetooth is relegated solely to controlling cable-replacement duties.
To meet the demand for higher data rates, the IEEE released the 802.11a and 802.11g standards, which are a much better fit for wireless home networking. The 802.11a standard uses OFDM (orthogonal frequency-division multiplexing) as a modulation scheme and provides data speeds as high as 54 Mbps. Its 5-GHz carrier frequency prevents interference with many in-home consumer devices. The 802.11g standard is a 2.4-GHz, 54-Mbps wireless networking standard with a reduced range but better interoperability with 802.11b devices. Off-the-shelf interface devices and chip sets that work with all of the a, b, and g standards are now available from manufacturers at prices approaching the original WiFi baseline.
New networking technologies on the horizon may offer even higher wireless data rates in the home. The IEEE is working on 802.15.3a, a new UWB (UltraWideBand) standard that delivers data rates exceeding 500 Mbps over short distances. Although the data rate decreases with distance, UWB promises 110 Mbps at 10m—a substantial speed increase over 802.11. UWB technology uses high rise-time pulses to spread RF energy over several gigahertz at such low power as to appear as harmless noise to other devices. UWB can easily coexist with other wireless technologies, such as 802.11 (Figure 3). There are currently two proposals for the new UWB standard. XtremeSpectrum and Motorola propose a single band, direct-sequence CDMA (code-division multiple access) technology, and Intel and Texas Instruments lead the OFDM Alliance Multiband approach, which uses dozens of channels from 2 to 11 GHz.
Web at home
The last important element of the digital-home architecture is the Internet connection. Almost essential for sophisticated systems, Internet connectivity provides remote interaction, monitoring, and control of the home along with access to external content. Although you can access basic Internet service through a dial-up modem, most users opt for higher bandwidth data via DSL, cable, satellite, or wide-area wireless technologies. For example, Wi-Max, also known as 802.16a, is a new non-line-of-sight, metropolitan-area-networking standard that can transfer data at about 70 Mbps over 30 km to thousands of users from a single base station. Operating in the 2- to 11-GHz range, 802.16a can be an effective high-bandwidth replacement for the last-mile connection to the home. Considered part of the Internet connection, a gateway device provides a protective firewall, in-home network management, and a perfect location to deliver digital services to the home. Several vendors offer reference architectures to speed development and deployment of advanced gateway systems. For example, ADI Engineering offers the Coyote gateway reference design, which includes the Intel IXP425 network processor. Coyote provides WAN (wide-area-network) connectivity via ADSL or Ethernet, 802.11a/b single or dual mode, two voice lines, a four-port Ethernet switch, voice over IP, USB, RS-232, IDE, and parallel interfaces (Figure 4).
No matter what technologies are available in the home, the measure of a successful system is how well the devices work together. Although several organizations have tried to organize industrywide interoperability standards, most have suffered from inadequate participation by major hardware and software vendors. The latest group seems to be off to a good start with backing from the likes of Microsoft, Intel, HP, IBM, Sony, and several other equipment manufacturers. The DHWG (Digital Home Working Group) envisions a wired and wireless interoperable network of PCs, consumer electronics, and mobile devices in the home for sharing digital media and content services. Its goal is to develop a set of design guidelines by mid-2004 that use established standards such as Internet Protocol, UPnP (Universal Plug and Play), WiFi, and other common formats to simplify the sharing of digital content.
The basic interoperability issues include media formatting, transport protocols, device management, and networking technology. The DHWG plans to include the most common formats that devices require and allow optional formats for increased performance between compatible hardware. Figure 5 provides an early overview of the DHWG standards. In the digital-imaging area, for example, DHWG standards will require device compatibility with JPEG and PNG (Port-able Network Graphics). PNG is a patent-free file format for the lossless but compressed storage of raster images that supports indexed-color, grayscale, and true-color images. Designers may optionally include GIF and TIFF compatibility. For audio content, DHWG requires LPCM (linear pulse-code modulation), which offers an uncompressed audio format that is similar to CD audio but with higher sampling frequencies and quantizations. LPCM offers as many as eight channels of 48- or 96-kHz sampling frequency and 16, 20, or 24 bits per sample. Vendors may optionally incorporate AAC (Advanced Audio Coding), MP3 (MPEG Audio Layer 3), AC-3 (Dolby Digital coding system), ATR-AC3plus (Adaptive Transform Acoustic Coding), or WMA9 (Microsoft Active Streaming file) audio formats. In the all-important video area, in which compression technologies prevail, DHWG requires MPEG-2 (Moving Picture Experts Group 2) formatting and allows MPEG-1, MPEG-4, and WMV9 (Microsoft Active Streaming file).
Not with my data
Another big challenge in the digital home is digital-rights management. Content providers want developers to include provisions to protect data, yet little incentive exists for hardware and software vendors to do so. Although the initial charter downplays content protection, you can bet that content producers are lobbying DHWG to make digital-rights management a large part of their agenda. Microsoft offers the Windows Media Rights Manager 9 Series software developer's kit, which lets developers create applications that configure and encrypt digital-media files and issue licenses. The resulting Windows Media file contains a version of the file that has been encrypted with a key so that only the person who has obtained a license for that file can play it.
Simplified home-device interoperability also requires some type of device-discovery and -control mechanism to automate device connections. UPnP, required by DHWG, defines a set of common services that devices can use to join a peer-to-peer network and describe their capabilities to enable other devices to use them without a complicated setup or configuration. Using common protocols instead, UPnP requires no device drivers. You can implement UPnP devices using any programming language and on any operating system. In 2000, Intel created the first version of a Linux software-development kit for UPnP devices and subsequently released it to the open-source community. You can download the kit at http://upnp.sourceforge.net.
The frustrations of connecting home-entertainment devices, the plethora of remotes, and the incessant blinking of that unset digital clock on the VCR attest to the need for industrywide standards for consumer-device interoperability. And these problems will become worse as vendors deliver convergence products that combine computing functions with these entertainment devices. It is time for the industry to support a common set of standards to simplify the sharing of digital music, photos, and video among networked consumer electronics, mobile devices, and PCs.
You can reach Technical Editor Warren Webb at 1-858-513-3713, fax 1-858-486-3646, e-mail wwebb@edn.com.
For more information...
For more information on products such as those discussed in this article, contact any of the following manufacturers directly, and please let them know you read about their products in EDN.
ADI Engineering
1-434-978-2888
www.adiengineering.com
DHWG (Digital Home Working Group)
www.dhwg.org
Domosys
1-418-681-8022
www.domosys.com
Echelon
1-408-938-5200
www.echelon.com
Gateway
1-800-369-1409
www.gateway.com
Hewlett-Packard
1-970-635-1000
www.hp.com
Home Director
1-800-426-7144
www.homedirector.com
Homeplug Powerline Alliance
www.homeplug.org
Hewlett-Packard
1-970-635-1000
www.hp.com
IBM
1-888-839-9289
www.ibm.com
IEEE (Institute of Electrical and Electronics Engineers)
www.ieee.org
Intel
1-408-765-8080
www.intel.com
Microsoft
1-425-882-8080
www.microsoft.com
Motorola
www.motorola.com
Sony
www.sony.com
Texas Instruments
1-972-644-5580
www.ti.com
UPnP Forum
www.upnp.org
ViewSonic
1-909-444-8888
www.viewsonic.com
XtremeSpectrum
1-703-269-3000
www.xtremespectrum.com
