A primer on home networking technologies
Successful and economical deployment of IP-based broadband services and the networks used to support them in homes or businesses often requires service providers to re-use the existing wiring infrastructure at the customer premises. Fortunately, there are a variety of home networking technologies to choose from to meet system demands. However, when choosing a networking solution, service providers must evaluate which technology offers them the best economic and performance trade-offs.
The following is an overview of popular home networking technologies service providers can use to deploy video and data services in the home or office. The key attributes and traits of each are discussed without bias to any particular technology, including: Multimedia over Coax (MoCA), HPNAv3, HomePlug A/V, and wireless 802.11a/b/g.
Home networking is not new to consumers or service providers. However, new advances in entertainment and communications technologies are creating the need for an affordable high-speed network at the customer premises that is able to support next-generation services. A fully networked home that uses the latest technologies such as IPTV and the multi-room digital video recorder (DVR) illustrates why more backbone bandwidth is needed. Video demands on home networking determine the required capacity. Table 1 shows the nominal data rates for an MPEG encoded video.
IPTV service provides standard definition television (SDTV) and high-definition television (HDTV) to users via a data connection. Presently, most service providers are providing IPTV in an MPEG-2 format. However, they have plans to switch to the less bandwidth intensive MPEG-4/H.264 standard. In either case, the capacity required for each video channel can vary if higher compression rates or variable rate encoding are used to transport IPTV signals.
Multi-room, or whole-home DVR solutions provide a common hard drive-based DVR that can be accessed by other less expensive, light client set-top boxes (STBs) throughout the home. The technology enables end users to record their favorite programs from, and watch them in, any room in the home. Home networking facilitates transmission of program content and command signals between the light clients in each room and the central DVR, often in an IPTV format.
Multimedia networking typically assumes a best-effort or buffered data rate for applications that involve using the home network to transfer content between a PC and TV. For example, consumers can use multimedia networking to view on their TV sets, digital photos they have stored on their PCs.
Online gaming typically requires the same amount of bandwidth needed to support data services. However, latency of the data connections used for gaming is critical. Home networks used to support gaming services and applications likely will need to provide a higher quality of service (QoS) in order to deliver maximum competitive performance.
Many home networks also will be used to provide integration to data networks or to wireless extension access points. As a result, required service flow will occupy some of the home network’s bandwidth.
Presently, typical broadband data services offer anywhere from 2 Mbps up to 30 Mbps, and services that will support up to 100 Mbps are on the horizon. Standard best-effort 2-10 Mbps data services and wireless extension applications co-exist easily with IPTV or DVR services. At present, typical data services do not require any stringent latency -or jitter- related demands.
Home networking technology
Service providers can choose from a number of technologies to deliver the services described above. The following is a brief description of each solution’s key benefits and varying data rates (see Table 2).
Cat-5 Ethernet, or Fast Ethernet, offers a physical data rate of 100 Mbps and an informational data rate of more than 80 Mbps. The standard output for most home networking technologies, a single Cat-5 Ethernet connection often is used between the CPE such as STBs and home networking converters. Unfortunately, less than 5 percent of the homes with video service are equipped with Cat-5, which is expensive and resource-intensive to install throughout the house.
MoCA was designed to operate and coexist with cable or satellite television. Its key benefits include the ability to work over existing coax and through multiple splitters in a house, which in turn enables both retail and service providers to share the home coax network. MoCA is a good solution for service providers using a retail marketing model because it can be configured to automatically scan for active channels and train itself to find the best frequency. Occupying only a 50 MHz band, MoCA enables multiple high-speed channels to coexist. With up to eight nodes per channel, one frequency can be used for a 100 Mbps data network and a separate frequency can be used for a 100 Mbps IPTV network.
Ensuring QoS, MoCA also provides a true peer-to-peer mesh network and time-coordinated communications, which prevent collisions on the network. It offers a raw data rate of up to 270 Mbps max and has a typical information data rate of greater than 100 Mbps in most installations.
HPNAv3 can be transmitted via twisted pair phone lines or via coaxial cable. Therefore, operators can re-use both types of wiring in this type of home network. Designed to provide guaranteed QoS for services and priority service flows, HPNAv3 is a good candidate for QoS sensitive applications such as live HDTV or VoIP.
HPNAv3 operates in the 4-21 MHz range, which typically prevents it from operating in a system with a DOCSIS cable modem or an interactive cable STB. When used in an IPTV installation that is bundled with an FTTH, xDSL or data service, HPNAv3 does not conflict. The technology also is well suited to overlay satellite services and it has the flexibility to offer varying channel plans. While HPNAv3 enables direct peer-to-peer communications, however, they must be scheduled through a master communications element.
The upcoming HomePlug A/V standard looks very promising from a convenience perspective because it offers the ultimate re-use of existing AC wiring. End users can purchase electronic devices at the store and simply plug them into their home networks, which automatically enable those devices to share data and video. HomePlug AV operates in the 2-28 MHz range using varying modulation schemes to achieve a 200 Mbps PHY rate and 150 Mbps information data rate.
Used to establish wireless data connections to PCs, portable laptops, and printers, 802.11 a/b/g-based wireless solutions have become ubiquitous.
802.11a and 802.11g have promising raw data rates of up to 54 Mbps, but due to RF propagation issues, they are limited to a short distance, and data rates degrade rapidly if there are any walls in the signal path (Table 3). While walls, floors, and appliances can degrade their effectiveness, wireless communications are useful complements to other home networking technologies with the addition of wireless access points throughout the home.
The types of services operators offer will impact the demands and requirements placed on the home network. However, the biggest influence comes from consumers’ expectations of the service quality of live video and on-demand video. Consumers are much more likely to notice, and object to, their TV pictures freezing or tiling while watching their digital TVs. Because keeping these effects to a minimum is critical, the number of “entertainment outlets” planned for each home and the type of content to be viewed or experienced, comes into play when selecting a home network.
The network architecture selected to support a single STB and SDTV will require less bandwidth and quality than the architecture needed to deliver multiple HDTV streams throughout the home. As for data, consumers using their PCs to download and view news clips or highlights from a show are likely to have different expectations and perceptions of quality than consumers who have gathered to watch the Super Bowl on a 60-inch HDTV set.
When transporting services such as VoIP and video, network performance metrics such as latency and jitter can have a significant impact on service quality. Because latency is a critical factor for VoIP quality, a home network’s latency must be accounted for in its overall budget.
The BER, or packet error rate (PER), have a direct impact on the perceived quality of service. BER and PER can occur from noise on the system or from service capacity issues. For services such as VoIP or IPTV, which operate using real-time protocol (RTP), lost packets are not retransmitted. This can directly affect the user experience. For example, IPTV picture quality can be affected by distribution network and home network transport of signals.
It is important to determine the capacity needs of the system along with the expected service quality expectations as the system or service is deployed and equipment is selected. A system’s limitations also will be driven by CPE limitations. A safety margin on the required capacity should also be included to allow for network and overhead efficiencies.
In “greenfield” deployments, where no services have been installed previously, service providers have the luxury of picking the system that best meets their performance and price targets. In non-greenfield situations, making an initial investigation of what a home network architecture will look like is the first step in determining which technologies are most appropriate for use in each home. Understanding which services will co-exist on home wiring is critical for success. For example, knowing whether or not a service has to co-exist and overlay on an existing cable TV or satellite installation will influence the home networking technology choice.
Because whole-home DVR plus IPTV is the primary driver for advanced networking, coaxial cables are typically the ideal choice since they usually reside close to the TV. Both MoCA and HPNAv3 are designed to work on coax.
Coaxial cables and connectors are designed to be shielded in order to prevent over-the-air signals from mixing into the signals carried over the center conductor. However, coaxial home wiring networks are susceptible to ingress noise if the shielding, connectors, or terminations are substandard or damaged.
Ingress noise occurs when unwanted over-the-air signals or electrical noise seeps into the coaxial network. Often presenting itself in the same frequency as desired signals, ingress noise can disrupt or disturb operator-provided analog or digital services running over coaxial plant. Disruptive ingress noise can come from blenders, bread makers, vacuum cleaners, remote control cars, cordless phones, ham radios, machinery and microwave ovens. This noise can affect signals being transmitted within high-speed data and video home networks.
Ingress can be difficult to diagnose at installation because the sources are often intermittent.
To prevent noise issues, all coaxial installations should be verified. Verification should include the replacement of any sub-standard connectors, splitters, wire and terminals; elimination of any unterminated cable ends; and termination of any unused ports.
Each home networking technology provides different bandwidth rates, types of connectivity and conveniences to services providers and end users. All of the networking technologies discussed in this article are capable of providing an excellent solution when applied appropriately.
Service providers that know which technologies will provide them with the best cost/performance trade-offs and plan their home networking strategies up-front will be in the best position to offer their customers a better broadband experience and the reliability they expect.
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