Wi-Fi + powerline turns home networks into ‘smart pipes’
Suddenly we’ve all got home networks. And what’s more, our networks are being pressured to not simply connect computers and entertainment devices, but to do so with the same quality and performance that is delivered directly from the high-definition television or digital music device.
Home networking has come a long way. What started as a means of sharing a broadband connection (first-generation home networking) quickly became a data network for connecting computers and sharing peripherals (second-generation home networking).
Now those data networks are being asked to evolve into entertainment-grade networks for distributing digital content stored in the home and accessed from outside the home (third-generation home networking). Will first- and second-generation technology meet our third-generation expectations? The short answer is: No.
One of the key issues is how to leverage wireless technology’s ubiquity while dealing with its quality of service (QoS) deficiencies as compared to wireline solutions. We’ve grown accustomed to Wi-Fi’s convenience. Now that the security setup headache has by and large been cured and wireless delivers additional performance via 802.11n, Wi-Fi works (mostly) for sharing a broadband connection and transferring data between devices.
What it does not do well is reliably deliver high-definition video throughout a typical home with real walls and other electrical equipment. A dropped packet is meaningless during a file transfer but is another thing entirely while streaming video.
To reliably deliver high-definition video, we need to go back to proven and trusted Cat-5 wires. However, drilling holes for wire runs everywhere they are needed is frequently not an option. Coax cable and twisted pair (phone lines) are great alternatives, but they typically don’t reach every desired location, either. Electrical wires are more pervasive but sometimes create interference concerns, especially with portable devices. Figure 1 shows the various physical media options.
Each home networking medium forces a trade-off between performance and ubiquity. Unfortunately, no single medium alone is sufficient to deliver peak bandwidth requirements and quality of service demands across the full range of services and applications that a home network must deliver, now and in the near future. For this reason, the industry is turning its attention to the development of true hybrid home networks that create a “unified smart pipe” for all services and applications.
These hybrid networks go well beyond simple dual-function extender devices that, for instance, use powerline communications (PLC) to “bridge” two Wi-Fi zones. Hybrid smart pipe solutions combine the attributes of the network’s multiple technologies, harnessing their capabilities to either intelligently partition traffic streams or combine the mediums into larger pipelines for supporting higher-bandwidth needs.
One combination of mediums that is particularly compelling is Wi-Fi and PLC. Together, they provide the coveted “wholehouse coverage” that operators need.
PLC is not limited to any specific geography, and it works in any power environment (multi-phase, 50 Hz, 60 Hz, 110V or 220V). Furthermore, it is available for use at any power receptacle in the home (typically 40-plus outlets).
Wi-Fi combined with PLC can extend traditional home networking coverage and performance beyond what either networking technology can achieve by itself, while providing full fault tolerance and improving overall noise immunity. The result is a simpler, more universal and consumer-friendly solution for IPTV, over-the-top video distribution and entertainment networking.
Implementing hybrid smart pipes requires a way to switch between multiple physical layer (PHY) technologies that provide the interface to each network medium (e.g., Cat-5, coax cable, twisted pair, powerline, air). Additionally, intelligent switching algorithms are required to constantly monitor PHY conditions and to allocate traffic streams according to throughput requirements and QoS priorities.
This monitoring is critical because if the status in one medium deteriorates (for example, if the wireless signal is degraded), the network can compensate by dynamically reallocating traffic streams. Overall network performance and reliability becomes the synergistic product of all PHY technologies, and the network’s intelligent switching capabilities are perhaps more important than the performance of any individual physical medium.
Working with multiple mediums has another significant benefit: Individual channels on each medium may be aggregated, or “bonded,” together to deliver one enhanced “super channel” capable of supporting higher throughput rates and more stringent quality requirements. This extends the coverage and robustness of the home network, enabling it to reach parts of the home that would not be possible with a single medium alone. Figure 2 shows this principle at work.
The technology behind each individual physical medium has undergone a long period of industry discussion and a few battle scars. A previously murky standards map is now becoming clear. In the wireline space, there are two established standards in coax home networking: the Multimedia over Coax Alliance’s MOCAx, which has been deployed by Verizon and others, and the HomePNA Alliance’s HomePNAx, which has been deployed by AT&T. MoCA operates in the RF realm, while HomePNA operates in the baseband domain, so while these standards do not interoperate, they do not interfere with each other, either.
The other wireline option, PLC home networking, is now supported by the newly approved IEEE standard 1901, which is backed by the HomePlug Powerline Alliance and Panasonic and is quickly becoming the de facto standard. IEEE 1901 contains a coexistence protocol called ISP (inter-system protocol), which provides a means of assuring non-interference for existing and future technologies that may want to share the medium.
The IEEE 1901 Draft Standard is the first global PLC standard, and its publication is expected to lead to the widespread incorporation of PLC network interface connections inside consumer electronics devices. Powerline networking can also be implemented using the emerging G.hn technology.
Meanwhile, over the air, Wi-Fi is ubiquitous. The possibilities for intelligent, multi-PHY home networking are enticing. With a smart switch controlling a single smart pipe, customers can have one box in the home and have a plugand-play experience for all devices connected to that box, as well as have the opportunity for their home networking service to become a managed service by their provider, which will support all necessary self-service tools for resolving any technical issues.
If/when these issues must be elevated, there is one customer care contact and one common and consistent user interface. The carrier benefits from these same dynamics, working with a common inhome infrastructure and common open systems service platform with reduced cost and operating expenses. Figure 3 illustrates this scenario.
While the standards map in each individual medium is well populated, a standard for intelligent switching is only now being discussed. Perhaps the most important hints in this direction are the collaboration messages coming from the special-interest groups, such as HomePlug and MoCA, which have announced that they are exploring ways of working together.
What would be really interesting would be a Wi-Fi/HomePlug/MoCA collaboration group. A single, unified standard for intelligent switching across multiple mediums? Watch this space.
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