In today's exploding service environment, with competition stronger than ever and powerful new multimedia services in the wings, a carrier's responsibilities now extend into the house itself - a place where things get complicated very fast.

Home networks are a mishmash of mediums, equipment, and standards. Coaxial cable, electrical wiring, Cat 2/3/5, and wireless devices are all present. What's more, numerous associations, standards bodies, alliances, and vendors are jockeying to be the solution of choice for consumers hungry for next-generation digital services.

And hungry they are. It's estimated that more than 20% of TV households already have HDTV. That number will increase dramatically after April 2009, when all TV sets sold in the U.S. will be required to support HDTV. The Wi-Fi Alliance reports that the average residential wireless user currently has 4 devices communicating wirelessly, while In-Stat, a leading high-tech market research firm, states that home networking equipment revenue will jump from $9 billion in 2004 to over $21 billion in 2009, as homeowners help themselves to advanced entertainment and communications choices.

The killer app of this new era in digital services is IPTV. By 2010, when IPTV is expected to hit its stride, 72 million households worldwide will have already subscribed to this feature-rich mix of global channels, anywhere-TV, video on demand (VoD), and personal media channels.

The appeal of IPTV is immense. Among other advantages, consumers will be able to access entertainment by staging a search a la Yahoo! or Google for the program, actor, genre, or subject matter they want. Viewers will be in charge, and media consumption will enter a new era of fluidity that will challenge the business skills of content creators and distributors alike.

Carriers will also play a key role in this evolving digital landscape. With more digital information being forced through the pipeline, Quality of Service (QoS) becomes more important than ever. A cohesive QoS environment must be established from the CO, through the OSP, across the residential gateway, and ultimately to the subscriber's device.

The trouble is, a lot of factors come into play inside the home, and they vary from house to house. VoIP, video streaming, and interactive gaming are highly sensitive to increases in latency and reductions in speed. Depending on the medium and equipment used, these latency and speed issues can wreak havoc on transmission quality.

To ensure QoS, traffic must be prioritized and disruptive elements eliminated. For carriers, this requires a thorough understanding of the QoS strategies employed by the various coax, power line, and wireless network standards. Let's take a look at these strategies and their implications for OSP designers:

Coaxial
Coaxial cable hosts possibly the most crowded field of standards for next-generation services. Among the leaders is the MoCA (Multimedia over CoAxial) Alliance, an initiative of Comcast, Cisco, Motorola, Panasonic, Verizon, and other major communications companies. MoCA bases its QoS on Entropic's c.LINK network chip technology, which enables splitter jumping from node to node within the home network, directly or back through any number of upstream splitters.

Like all networking standards, MoCA supports video, voice, and data. To ensure its QoS, however, MoCA uses constant-delay TDMA to time-coordinate traffic and guarantee collision avoidance. MoCA also supports IEEE 802.1p priority queues, offering delays of less than 5 msec with very low jitter.

In addition to these strategies, Entropic’s c.LINK technology supports Parameterized Quality of Service (PQoS), which ensures that asynchro-nous data requiring only best-effort delivery does not interfere with time-sensitive multimedia data streams. Finally, c.LINK’s parameterized interface allows operators to either build a standard Universal Plug-and-Play (UPnP) QoS system, or create a custom solution using alternative, higher-layer QoS services.

Another leader in the coax category is the HomePNA Alliance, an organization that has chosen to deliver multimedia home networking over both coaxial cable and phone wires. The latest iteration of the HomePNA standard is HomePNA 3, which AT&T has selected to drive its U-verse service bundle. AT&T is integrating HomePNA 3 into IP set-top boxes by Motorola and Scientific Atlanta, along with residential gateways from 2Wire.

HomePNA employs CopperGate's CopperStream microchip technology, guaranteeing video, voice, and Internet data QoS using synchronous Media Access Control (MAC) with collision avoidance techniques. It also defines limits for jitter (<1 msec), latency (<10 msec) and error rates (<10-7 packet error).

Because of the challenges it foresees in delivering IPTV at the residential level, the HomePNA Alliance treats the home network as part of the carrier’s broader distribution system. In fact, HomePNA considers professional installation of home networking equipment, along with remote monitoring and management of the equipment, essential parts of its overall QoS strategy.

The third major standard to appear under the coax umbrella is Ultra Wide Band (UWB), a technology also capable of wireless operation. The WiMedia Alliance is the global organization behind UWB technology. Although much of the group's focus is on Wireless UWB, its standard is robust enough to stand up to the rigors of HDTV as well.

Tzero Technologies, an ultra wideband semiconductor leader, has optimized its version of UWB specifically for HDTV distribution using a series of coax and wireless links. With Tzero UWB, service providers can network entertainment without running new cabling. Consumer electronics manufacturers can also use Tzero’s chipsets to create new classes of wireless video devices - HDTVs, digital video recorders, and more - that are easier and less expensive to install.

Tzero Technologies' UltraMIMO (Multiple-Input, Multiple-Output) is the predominant standards-based UWB wireless technology available today. It provides link reliability of over 99% - significantly better than current Wi-Fi, which has only 90% reliability. UltraMIMO cancels in-band interference of 10 dB or more above the desired signal power, and uses the JPEG2000 codec to lower latency, maintain image quality, and reduce errors.

Wireless
Of course, Wi-Fi users and carriers alike await the much-anticipated rollout of 802.11n. The new standard, according to latest information from the WiFi Alliance, will now be ratified in late 2008 or early 2009.

802.11n uses several new techniques to strengthen wireless signals, increase range, and raise data rates for IPTV. For example, transmission speeds are intensified by actually leveraging radio signals that bounce off walls and obstructions. To strengthen the signal, 802.11n uses MIMO, a technology by which multiple antennas are used at both the transmission and reception points.

802.11n establishes 4 priority levels for traffic; in order from highest to lowest, they are: voice, video, data (Internet, email, etc.), and background (e.g., local printers). While 802.11n QoS ensures minimal latency effects like delay or jitter, the standard requires that levels be set by the consumer - a potential drawback to the system.

In an effort to simplify setup at the residential level, as well as to get a jump on the debut of 802.11n, Ruckus Wireless, a well-funded wireless equip-ment supplier, has developed MediaFlex, a wireless multimedia system that enables high-def transmissions within the 802.11b and 802.11g framework.

MediaFlex is comprised of two elements: BeamFlex, a MIMO smart antenna; and SmartCast, an RF traffic engineering technology with QoS. SmartCast QoS uses traffic management algorithms to ensure adequate, on-demand bandwidth for multiple broadcast quality video streams, while maintaining adequate bandwidth for data applications. It automatically detects video and IPTV traffic, prioritizing them to optimize bandwidth and delay.

Powerline
Rounding out the alternative media for home networks is the home's electrical wiring grid. Clearly the most ubiquitous of all transmission alternatives, electrical wiring also carries the most challenges. Impedance and amplitude/phase variances are present at every stub. Brush motors, fluorescent/halogen lamps, dimmer switches, amateur band radio, and other devices can degrade signals from 30 to 60 percent - even more in some cases.

Also playing a factor is the privacy risk. Neighborhood electrical transformers don't prevent signals from propagating into adjacent homes, making electrical wiring as susceptible to eavesdropping and service stealing as older wireless technologies.

HomePlug standards-based solutions are a leading answer to the problems of powerline communications (PLC), as the medium is known. The HomePlug Alliance, perhaps the best-known of the PLC players, announced its HomePlug AV standard in 2005. Leveraging Ortho-gonal Frequency Division Multiplexing (OFDM) modulation, HomePlug AV uses OFDM in burst mode, rather than the continuous mode, to increase throughput and minimize errors.

HomePlug AV’s adaptive approach to changes in the power line medium enable it to manage interference and transfer function degradations; other strengths include France-Telecom-developed Turbo Codes for Forward Error Correction (FEC), interleaving, automatic repeat request, and line cycle synchronization. These strategies deal more effectively with the many cyclical noise sources found in home wiring.

Channel access is accomplished in HomePlug AV at the Medium Access Control layer using a mix of priority-based Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) and TDMA. CSMA/CA provides efficient delivery of asynchronous traffic, while TDMA provides bandwidth reservation, tight control of latency/jitter, and quasi error-free delivery.

Intellon's INT6000 and new INT6300 open-standard-based chips and firmware are driving the HomePlug AV market. With the INT6000 and INT6300, eight (8) levels of QoS (prioritized) can be set to ensure that video and voice are delivered reliably. An innovative Central Coordinator controls the activities of the network, allocating time for CSMA use, scheduling TDMA, and establishing admission control in order to prevent other networks in other residences from linking into the local home network.

Competing with HomePlug in PLC is the Universal Powerline Association (UPA), an international association headquartered in Europe. The UPA is dedicated to establishing an open, multi-vendor system. Its members in-clude Ambient Corporation, Current Technologies International, Corinex Communications, DS2, Itochu, Ilevo, Sumitomo, and Toyo Network Systems. Chipset technology from DS2 (Design of Systems on Silicon S.A.) has been chosen as the standard for UPA solutions.

In March 2005, the UPA approved its Digital Home Standard (DHS), supporting the creation of hybrid coaxial/powerline network equipment. By transmitting networking signals over both coax and powerlines, the DHS strategy ensures that the best signal (typically via coax) will prevail in order to maximize throughput. Other QoS elements are very similar to that of HomePlug including OFDM modu-lation, TDMA, eight service classes, and centralized bandwidth management.

CPE Considerations
For service providers and their OSP designers, establishing quality of service from the core through the home network is a matter of instituting a consistent, end-to-end standard. Modern gateway devices are moving from the outside wall of the house to indoors, often in the form of hybrid gateway/set-top devices that can be configured to match a home’s particular medium. Auto-configuration server solutions assist in this effort by allowing carriers to configure Customer Premises Equipment (CPE) remotely.

In some cases where a set-top box is not capable of integrating with a particular standard, an adaptor or other adjunct device is needed. Whether or not an adaptor is required, however, IPTV gateway devices must be set to match the frequencies of the network's physical layer, enabling them to sync with the QoS strategy of the standard being used. Once the profile is known, integrating with the particular queuing mechanism is often as simple as downloading a configuration file.

With consistent QoS in place, service providers can also improve trouble-shooting for Triple Play services. A properly configured and consistent system will provide the visibility necessary for resolving problems quickly and maintaining quality service.

Accommodating the advantages and disadvantages of coaxial, powerline, and wireless standards will continue to be a real test for the service provider. Doing so, however, will increase customer satisfaction and, ultimately, differentiate the provider in a crowded digital services marketplace.

Find more information about these organizations:
HomePNA Alliance - www.homepna.org
In-Stat - www.in-stat.com
MoCA Alliance - www.mocalliance.org
Universal Powerline Association - www.upaplc.org
Wi-Fi Alliance - www.wi-fi.org
WiMedia Alliance - www.wimedia.org