Electronic Design

Digital Home Networks Need Some Discipline

There's no shortage of home networking products out there, but not all are equal in terms of interoperability.

Not all that long ago, a state-of-the-art home network may have comprised two or more computers wired together via their serial or parallel ports. In more sophisticated arrangements, network cards provided the link from PC to PC. Just the ability to share data between a laptop and a desktop, as well as a printer and other basic peripherals including a common Internet connection, was network nirvana.

But as simple as these topologies appear, achieving a successful and reliable configuration on the first, second, and sometimes third try would often prove to be a masochistic experience at best for the average computer user. Depending on the operating system, software compatibility, and other interoperability issues, the road to network nirvana was not without frustrating detours.

Current home networks are far more intricate, often including wired and wireless computer peripherals that interact with electronics not traditionally associated with computers, such as household appliances, security systems, telephones, and home-entertainment systems. With the proliferation of broadband Internet and wireless services, users can access their home networks from pretty much anywhere in the world.

Despite the complexity of current home networks, they’re far easier to set up and configure due to the reality of true plug-and-play peripherals and a number of certain interoperability standards adhered to by manufacturers. Of course, we can’t rule the occasional bit of cabaret encountered when two different products adhere to two different standards.

Convergence & Divergence
Roughly speaking, today’s digital home consists of three domains: content delivery, content distribution, and home automation. Content delivery originates from any outside sources and may include a broadband Internet connection, satellite or cable television feed, or other form of data delivery. Content distribution stems from a number of dedicated components, like a set-top box and/or PC that sends content to a target destination, i.e., TV, audio system, another PC, PDA, or even a cell phone.

Becoming more popular, automation components add another layer of complexity to the home network. Devices that regulate thermostats, open and close doors, control surveillance cameras and smoke alarms, and perform other functions can be wired, wireless, operational through the home’s power lines, or any combination of the three. And all connect via a PC, which may handle content delivery and distribution tasks as well.

As all three domains of the home network converge, all of the products involved need to work together, and, hopefully, in a seamless manner. Because each domain has its own set of standards, this is where they diverge. End users usually have to go with products from one or several manufacturers that subscribe to a particular standard if they want their systems to work, and that may eliminate choices.

Current Standards
There’s no shortage of home-networking standards on the market, all of which vie for a lion’s share of market acceptance (see the table). Each has its strong points and downsides.

In its second release as of June 2007, the well-known ZigBee specification revolves around the IEEE 802.15.4 standard for wireless personal-area networks (WPANs). It contains a suite of communication protocols for low-power digital radios.

ZigBee boasts of being highly interoperable, easier to implement, and less expensive than other technologies such as Wi-Fi and Bluetooth. Applications include home and commercial automation and automatic meter reading.

In November 2007, the alliance announced the free public availability of the ZigBee Home Automation (HA) public application profile. This standard provides manufacturers with a standards-based approach to creating wireless home automation products worldwide without the need for proprietary technology. Reportedly, the HA profile will enable the development of home automation applications offering the highest levels of reliability, control, ease of use, security, and choice.

Also employing an array of digital radios, the Z-Wave Alliance hosts more than 100 manufacturers developing wireless home control products based on the Z-Wave standard. Operating in the 900-MHz industrial, scientific, and medical (ISM) band, the technology delivers data rates up to 40 kbits/s using a Gaussian frequency-shift keying (GFSK) modulation scheme.

Users can create outdoor networks extending to 30 m with lower ranges indoors depending on the structure. Z-Wave may be the most popular RF technology for remote control devices, and its two-way mesh topology and battery-to-battery support make it highly compatible with sensors and control units.

Both ZigBee and Z-Wave primarily focus on home and commercial automation markets with some usage in data and media delivery. A more encompassing approach and the brainchild of the UPnP Forum, Universal Plug and Play (UPnP) technology, consists of network protocols that allow numerous devices to connect seamlessly for data sharing, communications, and entertainment. These device control protocols, based on TCP/IP, UDP, and HTTP communication standards, support peer-to-peer networking of PCs, appliances, and wireless devices.

In simple terms, UPnP enables communication between any two devices under the command of any control device on the network. It supports zero-configuration and automatic discovery of devices from a range of vendors. Devices connect to a network, obtain an IP address, and acknowledge the presence of other devices on the network.

While this sounds good, UPnP is not without concerns, particularly in security. Assuming all users of a particular network are trustworthy, all is fine. Yet UPnP users can turn off security features, like antivirus software, spyware detectors, and firewalls.

As the protocols are Internet-based, the possibility of unauthorized users getting into the network increases. Additionally, security protocols available within the technology are quite complex for average users. As a security measure, a lot of UPnP-compliant devices come with UPnP turned off.

These three networking standards, which represent a small sample of what’s out there, all work within themselves. Devices meeting requirements for the particular standard work well within that system, but each does not support all the device types by all manufacturers. Each may or may not support all of the popular and esoteric media and data formats out there as well.

A Call For New Standards
According to Victor Dominguez, business development director at DS2, the need for interoperability in the digital home has never been more imperative due to recent developments in consumer electronics and growing consumer demand for a true digital home.

In a paper titled “The Requirement for Interoperability in the Digital Home,” he points out that the broadband over powerline market is growing rapidly with predicted annual sales to reach $5.3 billion by 2010. He also says that current and next-generation technologies must gain support by way of a full-scale effort by all the market players to ensure that new networks and consumer products all interoperate, leading to a real digital home solution for global users.

Dominguez concludes that tech providers are designing systems and devices based on varying specifications, which means that they do not necessarily interoperate with products from other providers and, in some situations, do not even have upgrade interoperability with legacy products. Areas for immediate improvement include setting minimum requirements for quality of service (network speed/latency, reliability, and jitter) and establishing priority classification systems to manage the home network and minimize frequency interference.

Universal specifications for powerline networking are currently under joint development by IEEE and ETSI and should be made public some time in 2008. Until that time, Dominguez points to several sets of specifications such as the Universal Powerline Association’s Digital Home Standard (UPA DHS) to initiate stability for new applications. The UPA DHS is an open and interoperable standard. Plus, all UPA-tested products are backward-compatible.

Jaime Fink, director of product marketing for 2Wire, noted in a recent interview that one of his company’s challenges seems to be getting the telecom and broadband providers to quickly support some of the emerging home-networking standards. This could make things tricky for product makers like 2Wire, which provides global telecom carriers with broadband components, software, and service platforms that enable triple-play services: networked data, voice, and media.

On that note, the International Telecommunication Union (ITU) approved HomePNA 3.1 as a global home networking standard back in February 2007. The HomePNA 3.1 specification delivers data speeds up to 320 Mbits/s over existing phone wires and coaxial cables, which suits most content delivery applications. Several providers jumped on the bandwagon, such as AT&T, which uses HomePNA 3 for in-home distribution of its U-verse services.

Universal Interoperability
The Digital Living Network Alliance (DLNA) shares its vision of a wired and wireless interoperable network of personal computers, consumer electronics, and mobile devices in the home and on the road with a fairly long member list of prestigious consumer electronics, computer, and mobile device makers.

Similar to UPnP, a DLNA home network relies on existing Internet technologies and standards such as IP for universal addressing. The alliance guidelines currently specify version IPv4, citing it as a source of inexpensive connectivity. It also supports transparent delivery of different media types.

Unique to DLNA technology, devices on the network integrate a Device and Service Discovery and Control (DSDC) component that allows them to automatically self-configure networking properties, discover other devices on the network, and control and collaborate with these devices in a consistent manner. The DSDC component performs these feats using the UPnP Device Control Protocol Framework Version 1.

In terms of content delivery and distribution across the home network, the DLNA media model supports a base set of required image, audio, and video formats and a set of optional media formats. Required formats include JPEG, LPCM, and MPEG 2, respectively, while optional media includes PNG, GIF, and TIFF for images, AAC, AC-3, ATRAC 3plus, MP3, and WMA9 audio formats, and MPEG 1/4, AVC, and WMV9 video codecs.

Additionally, devices that source or render media content support a set of streaming media transports: HTTP mandatory and RTP optional. Most important, the DLNA both encourages the development of new codecs for bit-rate optimization and plans to support them as they emerge.

According to SMSC vice president of marketing Vamshi Kandalla, DLNA appears to be the way to go for network interoperability. The company recently put its chips in the DLNA corner with its PCI-based LAN9132 network multimedia co-processor, which supports home-networking, high-definition streaming as set forth by DLNA guidelines. It’s the company’s first PCI-based networking product, hoping to provide users with a broader spectrum of value-added networking options.

Which Way Will It Go?
It would be foolish to say which set of standards will take center stage in the future—or embrace any one home-networking technology as doing the same. Whether it be wired via Ethernet, USB, or HDMI, or be it powerline or wireless technologies, or a combination, the network has to be flexible, reliable, and able to operate with existing and new devices. It is safe to say this will be the case because, at some point, the market will tolerate no less.

Need More Information?
The Requirement for Interoperability in the Digital Home
Universal Powerline Association’s Digital Home Standard (UPA DHS)

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